Determination of the mechanical efficiency of the gearbox with cylindrical strait wheels. Moscow State Technical University. N. E. Bauman Classification of gearboxes depending on the fastening method

1. The purpose of the work

Deepening the knowledge of theoretical material, obtaining practical skills of self-experimental definition of gearboxes.

2. Basic theoretical provisions

The mechanical efficiency coefficient of the gearbox is the ratio of power, useful (resistance power N C. to the power of driving forces N D. on the input shaft of the gearbox:

The power of the driving forces and forces of resistance can be determined according to the formulas

(2)

(3)

where M D. and M S. - moments of the driving forces and forces of resistance, respectively, NM; and - the angular velocities of the shafts of the gearbox, respectively, input and output, from -1 .

Substituting (2) and (3) in (1), we get

(4)

where - the gear ratio of the gearbox.

Any complex machine consists of a number of simple mechanisms. The efficiency of the machine can be easily defined if the efficiency of all simple mechanisms included in it are known. For most mechanisms, analytical methods for determining the efficiency have been developed, but deviations in the purity of the processing of the rubbing surfaces of parts, the accuracy of their manufacture, changes in the load on the elements of kinematic pairs, the lubrication conditions, the speed of relative movement, etc., lead to a change in the friction coefficient.

Therefore, it is important to be able to experimentally determine the efficiency of the mechanism under study under specific operating conditions.

Necessary to determine the efficiency of the gearbox parameters ( M d, m with and L R.) You can determine using DP-3K devices.

3. DP-3K device device

The device (Figure) is mounted on the resulting metal base 1 and consists of an electric motor 2 with a tachometer 3, a loader device 4 and the gearbox under study.

3 6 8 2 5 4 9 7 1

11 12 13 14 15 10

Fig. Kinematic diagram of the device DP-3K

The electric motor housing is hinged in two supports so that the axis of rotation of the engine shaft coincides with the axis of the corps of the case. The fixation of the engine housing against circular rotation is carried out by a flat spring 6. When the torque is transmitted from the electric motor of the spring gearbox, it creates a jet attached to the electric motor housing. The motor shaft is tested with the gearbox input shaft through the coupling. The opposite end is articulated with a tachometer shaft.

The gearbox in the DK-3K device consists of six identical pairs of gear wheels mounted on ball bearings in the housing.

The upper part of the gearboxes has an easy-graded cover made of organic glass, and serves to visually observe and measure gear wheels when determining the transfer ratio.

The load device is a magnetic powder brake, the principle of operation of which is based on the property of the magnetized medium to resist the ferromagnetic bodies in it. A liquid mixture of mineral oil and iron powder is applied as a magnetized medium in the design of the loading device. The body of the loader is installed balancing with respect to the base of the device on two bearings. The limitation of circular rotation of the housing is carried out by a flat spring 7, which creates a jet, which balance the moment of the resistance forces (braking torque) created by the loading device.

Measuring devices of the torque and braking moments consist of flat springs 6 and 7 and the indicators of the hourly type 8 and 9, measuring springs, proportional to the torque values. The springs are additionally pasted strain gauges, a signal from which through a strain gauge can also be fixed on an oscilloscope.

On the front part of the base, the control panel 10 is located on which:

Toggle switch 11 on and off the electric motor;

Rotation frequency control knob 12 of the electric motor;

Signal lamp 13 of the instrument on;

Toggle switch 14 on and off the chain of the loading of the load device;

Handle 15 adjustment of the excitation of the load device.

When performing this laboratory work:

Determine the gear ratio of the gearbox;

Cancel measuring devices;

Determine the efficiency of the gearbox, depending on the resistance forces and on the speed of the electric motor.

4. Procedure for performing work

4.1. Determination of gear ratio reducer

The transfer ratio of the gearbox of the DP-3K device is determined by the formula

(5)

where z. 2 , z. 1 is the number of teeth, respectively, larger and smaller wheels of one stage; to\u003d 6 - the number of steps of the gearbox with the same gear ratio.

For the gearbox of the device DP-3K, the transfer ratio of one step

Found Gate Record i P. Check the experienced way.

4.2. Target measuring devices

The targeting of the measuring devices is performed when the device is disconnected from the source using tarium fixtures consisting of levers and cargo.

To target the measuring device of the motion of the electric motor, it is necessary:

Install on the electric motor housing Calibration device DP3A Sat. 24;

Install the load on the lever of the tariff device to the zero mark;

Install the indicator arrow to zero;

By installing the cargo on the lever on subsequent divisions, fix the indicator readings and the corresponding division on the lever;

Determine average value m cf. Indicator Formula Prices

(6)

where TO - the number of measurements (equals the number of divisions on the lever); G. - cargo weight, N.; N I. - indication of the indicator - the distance between the divide on the lever ( m.).

Middle Definition m C.Sr.prices of fission indicator of the load device are made by installation on the body of the loading device of the Tarising device DP3A Sat. 25 by a similar method.

Note. The weight of goods in the tariff devices DP3K Sat. 24 and DP3K Sat. 25 is respectively 1 and 10 N..

4.3. Definition of the Reductor efficiency

Definition of the Reducer efficiency depending on the resistance forces, i.e. .

To determine dependence, it is necessary:

Turn on the device 11 of the electric motor and the speed adjustment knob 12 set the specified by the teacher N;

Install the loading knob 15 of the load of the loading device to zero, turn on the excitation supply chain 14;

Smooth turn of the excitation current control knob Set the first value (10 divisions) arrow of the indicator arrow M S. resistance;

Handle 12 speed adjustment set (adjust) Initial specified rotational speed n.;

Fix the readings H 1 and H 2 indicators 8 and 9;

Further adjustment of the excitation current to increase the moment of resistance (load) to the next predetermined value (20, 30, 40, 50, 60, 70, 80 divisions);

Maintaining the speed of rotation unchanged, fix the indicators readings;

Determine the values \u200b\u200bof moments of driving forces M D.and resistance forces M S. For all measurements by formulas

(7)

(8)

Determine for all measurements of the Reducer efficiency by formula (4);

Apply indicators h. 1 I. h. 2, the values \u200b\u200bof the moments M D. and M S. and the found values \u200b\u200bof the Reducer efficiency for all measurements in the table;

Build a graph.

4.4. Definition of the Reducer efficiency depending on the number of rotation of the electric motor

To determine graphical dependence, it is necessary:

Enable the toggle switch 14 of the power and excitation chain and the excitation current adjustment knob to set the status value specified by the teacher M S. on the output shaft of the gearbox;

Include an electric motor device (toggle switch 11);

By installing the speed adjustment handle 12, a number of values \u200b\u200b(from the minimum to the maximum) rotational speed of the motor shaft and maintaining the constant moment value M S. load fixing indicator readings h. 1 ;

Give a qualitative assessment of the effect of the rotation frequency N on the Reducer efficiency.

5. Drawing up a report

The report on the work must contain the name

the purpose of the work and the task of determining the mechanical efficiency, the main technical data of the installation (type of gearbox, the number of teeth on wheels, the type of electric motor, the loading device, measuring devices and instruments), calculations, description of the target of the measuring devices, the table of experimentally obtained data.

6. Control questions

1. What is called mechanical efficiency? Its dimension.

2. What is the mechanical efficiency depends on?

3. Why are the mechanical efficiency determined by an experimental way?

4. What is the sensor in the measuring devices of the torque and braking moments?

5. Describe the load device and its principle of operation.

6. How will the mechanical efficiency of the gearbox change, if the moment of resistance forces increases (decrease) twice?

7. How will the mechanical gearbox efficiency change if the moment of resistance forces increases (decrease) by 1.5 times?

Laboratory work 9.

1 Torque on the output shaft of the gearbox M2 [nm]
The torque on the output shaft of the gearbox is called the torque, which is summed up to the output shaft of the gearbox, at the set value of the PN, the Safety coefficient S, and the calculated service life of 10,000 hours, taking into account the Reducer efficiency.
2 Nominal torque of the gearbox Mn2 [nm]
The rated torque of the gearbox is the maximum torque, to the safe transmission of which the reducer is calculated, based on the following values:
. Safety coefficient S \u003d 1
. Service life 10,000 hours.
MN2 values \u200b\u200bare calculated in accordance with the following standards:
ISO DP 6336 for gears;
ISO 281 for bearings.

3 Maximum torque M2MAX [nm]
The maximum torque is called the largest torque, which is maintained by the gearbox under conditions of static or inhomogeneous load with frequent launches and stops (this value is understood as an instantaneous peak load when the gearbox or starting torque under load).
4 Required torque MR2 [nm]
The torque value corresponding to the necessary consumer requirements. This value should always be less or equal to the nominal value of the MN2 output torque of the selected gearbox.
5 Estimated torque M C2 [nm]
The torque value that must be guided by selecting the gearbox, taking into account the required torque of the MR2 and the operational factor FS, is calculated by the formula:

The values \u200b\u200bof the dynamic efficiency of the gearboxes are indicated in Table (A2)

Limit thermal power PT [kW]

This value is equal to the limit value of the transmitted mechanical power reducer under conditions of continuous operation at an ambient temperature of 20 ° C without damage to the nodes and parts of the gearbox. At ambient temperature other than 20 ° C, and the intermittent operation mode, the PT value is adjusted taking into account the thermal coefficients ft and the speed coefficients shown in Table (A1). It is necessary to ensure the following condition:

Efficiency ratio (efficiency)

1 Dynamic efficiency [ηD]
Dynamic efficiency is the ratio of the power obtained on the output shaft P2, to the power applied to the input shaft P1.

Transmission number [I]

The characteristic inherent in each reducer equal to the ratio of rotation speed at the inlet N1 to the speed of rotation at the output N2:

i \u003d n1 / n2

Rotational speed

1 Speed \u200b\u200bat the inlet N1 [min -1]
The speed of rotation, supplied to the input shaft of the gearbox. In the case of direct connection to the electric motor, this value is equal to the output speed of the electric motor; In the case of connections through other drive elements to obtain the input speed of the gearbox, the engine speed should be divided into a gear ratio of the supply drive. In these cases, it is recommended to bring the speed of rotation below 1400 rpm to the reducer. It is not allowed to exceed the values \u200b\u200bof the input speed of the gearboxes specified in the table.

2 speed at the output N2 [min-1]
The output rate of N2 depends on the input velocity of N1 and the gear ratio I; Calculated by the formula:

Safety coefficient [s]

The value of the coefficient is equal to the ratio of the rated power of the gearbox to the actual power of the electric motor connected to the gearbox:

S \u003d PN1 / P1

Reducer	Number of steps	Types of gear	Mutual location of the axes of the entrance and output shafts
Cylindrical	Single-stage	One or more cylindrical gears	Parallel
			Parallel or coaxial
	Four-stage		Parallel
Conical	Single-stage	One conical transfer	Crossing
Conical-cylindrical		One conical transmission and one or more cylindrical gears	Crossing or crossing
Worm	Single-stage two-stage	One or two worm gears	Crossing
			Parallel
Cylindrical worm or worm-cylindrical	Two-stage, three-stage	One or two cylindrical transmissions and one worm gear	Crossing
Planetary	Single-stage two-stage three-stage	Each step consists of two central gear wheels and satellites
Cylindrical planetary	Two-stage, three-stage, four-stage	Combination of one or more cylindrical and planetary gears	Parallel or coaxial
Conical planetary	Two-stage, three-stage, four-stage	Combination of one conical and planetary gear	Crossing
Worm-planetary	Two-stage, three-stage, four-stage	Combination of one worm and planetary gear	Crossing
Wave	Single-stage	One wave transmission

Classification of gearboxes depending on the location of the axes of the input and output shafts in space.

Reducer	Location of the axes of the input and output shafts in space
1. With parallel axes of input and output shafts	1. Horizontal; axis are located in a horizontal plane; The axes are located in the vertical plane (with the inlet shaft above or under the output shaft); Axis are located in the inclined plane
	2. Vertical
2. With the coinciding axes of the input and output shafts (coaxial)	1. Horizontal
	2. Vertical
3. With intersecting axes of the input and output shafts	1. Horizontal
4. With cross-moving axes of the input and output shafts	1. Horizontal (with inlet shaft above or under output shaft)
	2. Horizontal axis of the input shaft and the vertical axis of the output shaft
	3. Vertical axis of the input shaft and the horizontal axis of the output shaft

Classification of gearboxes depending on the fastening method.

Method of fastening	Example
On the withdrawal paws or on the stove (to the ceiling or wall):
at the level of the plane base of the gearbox housing:
above the level of the plane base of the gearbox housing:
Flange from the input shaft
Flange from the output shaft
Flange from the side of the entrance and output shafts
Nazadka

Structural designs according to the installation method.

Conditional images and digital designations of constructive designs of gearboxes and gear gear gearboxes: (products) according to the installation method of installation GOST 30164-94.
Depending on the design, gearboxes and gearboxes are divided into the following groups:

a) coaxial;
b) with parallel axes;
c) with intersecting axes;
d) with cross-going axes.

To the group A), products with parallel axes are attributed, in which the ends of the input and output shafts are directed to the opposite directions, and their mid-scene distance is no more than 80mm.
The variators and variator drives are also attributed to groups b) and c). Conditional images and digital designations of structural versions according to the installation method characterize the structural designs of the housings, as well as the location in the surface of the surfaces of the shafts or axes of the shafts.

The first is the structural execution of the housing (1 - on the paws, 2 - with the flange);
The second is the location of the mounting surface (1 - gender, 2 - ceiling, 3 - wall);
The third is the location of the end of the output shaft (1 - horizontal left, 2 - horizontal to the right, 3 - vertical down, 4 - vertical top).

The conditional designation of the group A) consists of three digits:
The first is the structural execution of the housing (1 - on the paws; 2 - with the flange); The second is the location of the mounting surface (1 - floor; 2 - ceiling; 3 - wall); The third is the location of the end of the output shaft (1 - horizontal left; 2 - horizontal to the right; 3 - vertical down; 4 - vertical up).

The conditional designation of groups of groups b) and B) consists of four digits:
The first is the structural design of the housing (1 - on the paws; 2 - with the flange; 3 - mounted; 4 - noar); The second is the relative position of the surface of the attachment and axes of the shafts for the group b): 1 - parallel to the axes of the shafts; 2 - perpendicular to the axes of the shafts; For group B): 1 - parallel to the axes of the shafts; 2 - perpendicular to the axis of the output shaft; 3 - perpendicular to the axis of the input shaft); The third is the location of the fastening surface in space (1 - gender; 2 - ceiling; 3 - LEAP wall, front, rear; 4 - wall right, front, rear);

the fourth is the location of the shafts in space for the group b): 0 - the trees are horizontal in the horizontal plane; 1 - trees horizontal in the vertical plane; 2 - Vertical shafts; For group c): 0 - horizontal shafts; 1 - the output shaft vertical; 2 - the entrance shaft vertical).
The conditional designation of the group g) consists of four digits:
The first is the structural design of the housing (1 - on the paws; 2 - with the flange; 3 - mounted; 4 - noar);
The second is the relative position of the surface of the attachment and axes of the shafts (1 - parallel to the axes of the shafts, from the side of the worm; 2 - parallel to the axes of the shafts, on the wheel side; 3, 4 - perpendicular to the axis of the wheel; 5, 6 - perpendicular to the worm axis);
The third is the location of the shafts in space (1 - the trees horizontal; 2 - the output shaft vertical: 3 - the input shaft vertical);
The fourth is the mutual arrangement of a worm pair in space (0 - worm under the wheel; 1 - Worm over the wheel: 2 - Worm to the right of the wheel; 3 - worm on the left of the wheel).
The hinged design products are installed by a hollow output shaft, and the housing is fixed at one point from the rotational torque. Nozzle design products are installed with a hollow output shaft, and the housing is fixed motionless at several points.
In the motor gearboxes in the image of constructive execution according to the installation method there must be an additional simplified image of the engine circuit according to GOST 20373.
Examples of conventional designations and images:
121 - coaxial gearbox, structural design of the housing on the paws, fastening to the ceiling, horizontal shafts, output shaft on the left (Fig. 1, a);
2231 - gearbox with parallel axes, the execution of the housing with the flange, the surface of the attachment is perpendicular to the axes of the shafts, the mounting to the left wall, the trees are horizontal in the vertical plane (Fig. 1, b);
3120 - gearbox with intersecting axes, housing performance attachments, the mounting surface is parallel to the axes of the shafts, the mounting to the ceiling, the trees are horizontal (Fig. 1, B);
4323 - Reducer with cross-going axes, extension of the housing, the surface of the fastening is perpendicular to the axis of the wheel, the output shaft is vertical, the worm on the left of the wheel (Fig. 1, d). The LLLL symbol is indicated by the fixation point of the product from the rotational torque and fastening the hollow output shaft on the shaft of the working machine.

This article contains detailed information on the choice and calculation of the gear motor. We hope the proposed information will be useful to you.

When choosing a specific model, the gearbox takes into account the following specifications:

• type gearbox;
• power;
• revolutions at the exit;
• gear ratio;
• construction of input and output shafts;
• installation type;
• additional functions.

Type of reducer

The presence of a kinematic drive scheme will simplify the choice of the type of gearbox. Constructive gearboxes are divided into the following types:

Worm single-stage with the arrangement of the input / output shaft (angle of 90 degrees).

Worm two-stage With perpendicular or parallel location of the axis of the input / output shaft. Accordingly, the axes can be located in different horizontal and vertical planes.

Cylindrical horizontal With parallel location of the input / output shaft. The axes are in one horizontal plane.

Cylindrical coaxial at any angle. The axis of the shafts are located in the same plane.

IN conical-cylindrical The gearbox of the axis of the input / output shafts intersect at an angle of 90 degrees.

IMPORTANT!
The arrangement of the output shaft in space is determined for a number of industrial applications.

• The design of worm gearboxes allows you to use them at any position of the output shaft.
• The use of cylindrical and conical models is more often possible in the horizontal plane. With the same with worm gearboxes of mass-dimensional characteristics, the operation of cylindrical units is economically appropriate due to an increase in the transmitted load of 1.5-2 times and high efficiency.

Table 1. Classification of gearboxes according to the number of steps and type of transmission

Type of reducer	Number of steps	Type of transmission	Osay location
Cylindrical	1	One or more cylindrical	Parallel
	2		Parallel / coaxial
	3
	4		Parallel
Conical	1	Conical	Crossing
Conical-cylindrical	2	Conical Cylindrical (one or more)	Cross / crossing
	3
	4
Worm	1	Worm (one or two)	Crossing
	1		Parallel
Cylindrical worm or worm-cylindrical	2	Cylindrical (one or two) Worm (one)	Crossing
	3
Planetary	1	Two central gear wheels and satellites (for each stage)	Coaxial
	2
	3
Cylindrical planetary	2	Cylindrical (one or more)	Parallel / coaxial
	3
	4
Conical planetary	2	Conical (one) planetary (one or more)	Crossing
	3
	4
Worm-planetary	2	Worm (one) Planetary (one or more)	Crossing
	3
	4
Wave	1	Wave (one)	Coaxial

Transmission number [I]

The gear ratio of the gearbox is calculated by the formula:

I \u003d n1 / n2

where
N1 - the rotational speed of the shaft (the number of rpm) at the entrance;
N2 - the rotational speed of the shaft (number of rpm) at the output.

The value obtained during the calculations is rounded to the value specified in the specifications of the specific type of gearboxes.

Table 2. Range of gear ratios for different types of gearboxes

IMPORTANT!
The speed of rotation of the motor shaft and, accordingly, the gearbox input shaft cannot exceed 1500 rpm. The rule is valid for any types of gearboxes, except for cylindrical coaxials at a speed of rotation up to 3000 rpm. This technical parameter manufacturers indicate the consolidated characteristics of electrical engines.

Torque gearbox

Torque on the weekend - Rotating moment on the weekend. The rated power, the safety coefficient [S] is taken into account, the calculated duration of operation (10 thousand hours), the Reducer efficiency.

Nominal torque - Maximum torque that provides secure transmission. Its value is calculated based on the security coefficient - 1 and the duration of operation - 10 thousand hours.

Maximum torque - The limit torque, withstanding the gearbox, with constant or changing loads, operation with frequent starts / stops. This value can be interpreted as a instant peak load in the mode of operation of the equipment.

Required torque - Torque, satisfying the criteria of the customer. Its value is smaller or equal to the nominal torque.

Estimated torque - The value required to select the gearbox. The calculated value is calculated by the following formula:

MC2 \u003d MR2 X SF ≤ Mn2

where
MR2 - the required torque;
SF - service factor (operational coefficient);
Mn2 - nominal torque.

Operational coefficient (service factor)

Service factor (SF) is calculated by the experimental method. The type of load is taken into account, the daily duration of work, the number of starts / stops per hour of operation of the gear motor. You can determine the operational coefficient using table 3 data.

Table 3. Parameters for calculating the operational coefficient

Type of load	To-in starts / stops, hour	Average duration of operation, day
		<2	2-8	9-16h	17-24
Smooth start, static mode of operation, acceleration of medium size	<10	0,75	1	1,25	1,5
	10-50	1	1,25	1,5	1,75
	80-100	1,25	1,5	1,75	2
	100-200	1,5	1,75	2	2,2
Moderate load at startup, variable mode, acceleration of the mass of medium	<10	1	1,25	1,5	1,75
	10-50	1,25	1,5	1,75	2
	80-100	1,5	1,75	2	2,2
	100-200	1,75	2	2,2	2,5
Operation with heavy loads, variable mode, acceleration of a large amount of mass	<10	1,25	1,5	1,75	2
	10-50	1,5	1,75	2	2,2
	80-100	1,75	2	2,2	2,5
	100-200	2	2,2	2,5	3

Drive power

Properly calculated drive power helps to overcome the mechanical friction resistance arising from straight and rotational movements.

Elementary formula for calculating power [P] - calculating the ratio of force to speed.

With rotational motions, the power is calculated as the torque ratio to the number of revolutions per minute:

P \u003d (MXN) / 9550

where
M - torque;
N - the number of revolutions / min.

The output power is calculated by the formula:

P2 \u003d p x s

where
P - power;
SF - service factor (operational coefficient).

IMPORTANT!
The input power value should always be higher than the value of the output power, which is justified by losses when engaged:

P1\u003e P2.

It is impossible to make calculations using the approximate value of the input power, as the efficiency can differ significantly.

Efficiency ratio (efficiency)

CPD Calculation Consider on the example of a worm gearbox. It will be equal to the ratio of mechanical output power and input power:

ñ [%] \u003d (P2 / P1) x 100

where
P2 - output power;
P1 - input power.

IMPORTANT!
In worm gearboxes P2< P1 всегда, так как в результате трения между червячным колесом и червяком, в уплотнениях и подшипниках часть передаваемой мощности расходуется.

The higher the gear ratio, the lower the efficiency.

The efficiency of the operation and the quality of lubricants used for the prophylactic maintenance of the gearbox motor is affected.

Table 4. CPD worm single-stage gearbox

Ratio	Efficiency at a w, mm
	40	50	63	80	100	125	160	200	250
8,0	0,88	0,89	0,90	0,91	0,92	0,93	0,94	0,95	0,96
10,0	0,87	0,88	0,89	0,90	0,91	0,92	0,93	0,94	0,95
12,5	0,86	0,87	0,88	0,89	0,90	0,91	0,92	0,93	0,94
16,0	0,82	0,84	0,86	0,88	0,89	0,90	0,91	0,92	0,93
20,0	0,78	0,81	0,84	0,86	0,87	0,88	0,89	0,90	0,91
25,0	0,74	0,77	0,80	0,83	0,84	0,85	0,86	0,87	0,89
31,5	0,70	0,73	0,76	0,78	0,81	0,82	0,83	0,84	0,86
40,0	0,65	0,69	0,73	0,75	0,77	0,78	0,80	0,81	0,83
50,0	0,60	0,65	0,69	0,72	0,74	0,75	0,76	0,78	0,80

Table 5. KPD wave gearbox

Table 6. KPD gear gearboxes

Explosion-proof performances of motor gearboxes

Motor gearboxes of this group are classified by the type of explosion protection execution:

• "E" - aggregates with an increased degree of protection. Can be operated in any mode of operation, including freelance situations. Strengthened protection prevents the probability of inflammation of industrial mixtures and gases.
• "D" is an explosive shell. The buildings of the aggregates are protected from deformations in the case of an explosion of the motor gear itself. This is achieved at the expense of its design features and high tightness. Equipment with the explosion protection class "D" can be used in modes of extremely high temperatures and with any groups of explosive mixtures.
• "I" is an intrinsically safe chain. This type of explosion protection provides support for explosion-proof current in the electrical network, taking into account specific conditions for industrial use.

Reliability indicators

Reliability indicators Motor gearboxes are shown in Table 7. All values \u200b\u200bare shown for a long mode of operation at a constant rated load. The gear motor must provide 90% of the resource specified in the table and in short-term overload mode. They arise when starting the equipment and exceeding the nominal moment twice as minimum.

Table 7. Resource shafts, bearings and gearboxes

For calculation and acquisition of motor gearboxes of various types, contact our specialists. You can familiarize yourself with the catalog of worm, cylindrical, planetary and wave motor gearboxes offered by the technical equipment.

Romanov Sergey Anatolyevich,
head of Mechanics Department
companies tehgorod

Other useful materials:

Purpose of work: 1. Determination of geometric parameters of gear wheels and calculating gear ratios.

3. Constructing graphs of dependence at and at.

Work performed: Full name

group

Work accepted:

Measurement results and calculation of wheel and gear parameters

Number of teeth

Diameter of peaks of teeth d A., mm

Module m.by formula (7.3), mm

Armor distance a W.by formula (7.4), mm

Ratio u.by formula (7.2)

General gear ratio by formula (7.1)

Kinematic scheme reducer

Table 7.1

Chart of dependence

η

T. 2, n ∙ mm

Table 7.2.

Experienced data and calculation results

Chart of dependence

η

n., min -1

Control questions

1. What losses are in gear transmission and what are the most effective measures to reduce transfer losses?

2. The essence of relative, constant and load losses.

3. How does the transmission efficiency change depending on the power transmitted?

4. Why is the efficiency with an increase in the degree of precision gears and gears rises?

Laboratory work number 8

Definition of the Cord Reducer

purpose of work

1. Determination of the geometric parameters of the worm and worm wheel.

2. The image of the kinematic gearbox scheme.

3. Constructing graphs of dependence at and at.

Basic safety regulations

1. Turn on the installation from the permission of the teacher.

2. The device must connect to the rectifier, and the rectifier - to the network.

3. After the installation is completed from the network, turn off.

Installation Description

On cast base 7 (Fig. 8.1) Mounted the studied gearbox 4 , electric motor 2 with tachometer 1 shown by the frequency of rotation and load device 5 (Magnetic powder brake). The brackets are mounted measuring devices consisting of flat springs and indicators 3 and 6 whose rods are resting in the springs.

On the control panel placed toggle 11 comprising and turning off the electric motor; a pen 10 a potentiometer that allows simpler to adjust the frequency of rotation of the electric motor; Tumbler 9 including load device and handle 8 potentiometer that allows you to adjust the braking torque T 2..

The stator of the electric motor is mounted on two ball bearings installed in the bracket, and can be freely rotated around the axis coinciding with the axis of the rotor. The reactive moment occurred during the operation of the electric motor is fully transmitted to the stator and acts in the direction opposite to the rotation of the anchor. Such an electric motor is called balancing.

Fig. 8.1. Installation DP - 4K:

1 - tachometer; 2 - electric motor; 3 , 6 - indicators; 4 - worm reducer;
5 - brake powder; 7 - base; 8 - load control knob;
9 - toggle switching on the load device; 10 - knob of regulating the speed of rotation of the electric motor; 11 - Turning on the electric motor

To measure the magnitude of the torque developed by the engine, the lever is attached to the stator, which presses to the flat spring of the measuring device. Spring deformation is transmitted to the indicator rod. By deflection of the arrow of the indicator, one can judge the magnitude of this deformation. If the spring is broken, i.e. Set the point addiction T. 1 turning the stator, and the number of indicator divisions, then when performing experience, you can judge the indicator readings on the moment of moment T. 1, developed by the electric motor.

As a result of the targeting of the measuring device of the electric motor, the value of the tariff coefficient

Similar method, the target brake device is determined:

General

Kinematic research.

Clean transfer number

where z. 2 - the number of worm wheels;

Z. 1 - the number of calls (turns) worm.

DP-4K installation reducer worm has a module M. \u003d 1.5 mm, which is responsible for GOST 2144-93.

Delicious diameter worm d. 1 and diameter coefficient worm q. Determined by the solution of equations

; (8.2)

According to GOST 19036-94 (the original worm and the original production worm), the height of the head of the coil is taken.

Estimated worm's pitch

Top Top

Dividing angle lifting

Slip speed, m / s:

, (8.7)

where n. 1 - frequency of rotation of the electric motor, min -1.

Definition of the Reductor efficiency

Power losses in worm engagement are made up of friction losses in engagement, friction in bearings and hydraulic losses for stirring and splashing oil. The main part of the losses are the losses in engagement, depending on the accuracy of the manufacture and assembly, the rigidity of the entire system (especially the rigidity of the Worm shaft), the method of lubrication, worm materials and teeth wheels, roughness of contact surfaces, slip speed, worm geometry and other factors.

Overall worm gearbox efficiency

where η P. – Efficiency, taking into account losses in one pair of bearings, for rolling bearings η n \u003d 0.99 ... 0,995;

n.- number of bearings pairs;

η p \u003d 0.99 - efficiency, taking into account the hydraulic losses;

η 3. - efficiency, taking into account the losses in the engagement and determined by the equation

where φ is an angle of friction, depending on the material of the worm and the teeth of the wheel, the roughness of the working surfaces, the quality of lubricant and the sliding speed.

The experimental definition of the Reducer efficiency is based on the simultaneous and independent measurement of torque T. 1 at the entrance and T. 2 at the output shaft of the gearbox. Reducer efficiency can be determined by equation

where T. 1 - torque on the shaft of the electric motor;

T. 2 - torque at the output shaft of the gearbox.

Experienced values \u200b\u200bof torque are determined by dependencies

where μ 1 I. μ 2 – tariff coefficients;

k. 1 I. k. 2 - According to the indications of the indicators of the measuring devices of the engine and the brakes.

Procedure for performing work

2. According to Table. 8.1 of the report to construct the kinematic scheme of worm transmission, for which it is possible to use the conditional notation shown in Fig. 8.2 (GOST 2.770-68).

Fig. 8.2. Conducting worm gear
with cylindrical worm

3. Turn on the electric motor and rotation of the handle 10 potentiometer (see Fig. 8.1) Set the frequency of rotation of the electric motor shaft n. 1 \u003d 1200 min -1.

4. Install the arrows of the indicators to the zero position.

5. Turn the knob 8 Potentiometer load reducer with different moments T. 2 .

Removing the indicator readings of the measuring device of the electric motor should be made at the selected speed of the electric motor.

6. Record in table. 8.2 Indicator reading report.

7. According to formulas (8.8) and (8.9), calculate values T. 1 I. T. 2. The results of the calculations will be in the same table.

8. According to Table. 8.2 Reports to build a chart with.

9. Similar to carry out experiments with and variable speed. Experienced data and calculation results are table. 8.3 report.

10. Build a graph of dependency at.

Sample report design

The worm reducer is one of the classes of mechanical gearboxes. Reducers are classified by the type of mechanical transmission. The screw, which underlies the worm gear, looks like a worm, hence the name.

Motor gear - This is an aggregate consisting of a gearbox and an electric motor that consist in one block. Worm gearbox Created In order to work as an electromechanical engine in various general-purpose machines. It is noteworthy that this type of equipment works perfectly both at constant and variable loads.

In a worm gearbox, an increase in torque and a decrease in the angular velocity of the output shaft occurs due to the energy conversion concluded in high angular velocity and low torque on the input shaft.

Errors when calculating and choosing a gearbox can lead to premature failure of it and, as a result, at best to financial losses.

Therefore, the work on calculating and selecting the gearbox must be trusted with experienced designers specialists who will take into account all the factors from the location of the gearbox in space and working conditions to the heating temperature during operation. Confirming this by the corresponding calculations, the specialist will ensure the selection of the optimal gearbox under your specific drive.

Practice shows that the properly selected gearbox provides for no less than 7 years - for worm and 10-15 years old for cylindrical gearboxes.

The choice of any gearbox is carried out in three stages:

1. Choosing a gearbox type

2. Select the size of the gap (sizes) of the gearbox and its characteristics.

3. Check payments

1. Choosing a gearbox type

1.1 Original data:

The kinematic drive diagram indicating all the mechanisms connected to the gearbox, their spatial location relative to each other with the place of attachment and installation methods of the gearbox.

1.2 Determination of the location of the axes of the shafts of the gearbox in space.

Cylindrical gearboxes:

The axis of the input and output shaft of the gearbox is parallel to each other and lie only in one horizontal plane - a horizontal cylindrical gearbox.

The axis of the input and output shaft of the gearbox is parallel to each other and lie only in one vertical plane - a vertical cylindrical gearbox.

The axis of the input and output shaft of the gearbox may be in any spatial position. At the same time, these axes lie on one straight line (coincide) - a coaxial cylindrical or planetary gearbox.

Conid-cylindrical gearboxes:

The axis of the input and output shaft of the gearbox is perpendicular to each other and lie only in one horizontal plane.

Worm gearboxes:

The axis of the input and output shaft of the gearbox can be in any spatial position, while they cross at an angle of 90 degrees to each other and do not lie in the same plane - a single-stage worm gearbox.

The axis of the input and output shaft of the gearbox can be in any spatial position, while they are parallel to each other and do not lie in the same plane, or they are crossped at an angle of 90 degrees to each other and are not lying in the same plane - two-stage gearbox.

1.3 Determination of the method of fastening, assembling position and optional of the gearbox.

The method of fastening the gearbox and the mounting position (fastening on the foundation or the driven shaft of the drive mechanism) is determined by the specifications given in the catalog for each gearbox individually.

The assembly option is determined by the schemes in the catalog. The schemes of "assembly options" are given in the "Designation of Reducers" section.

1.4 In addition, when choosing a type of gearbox, the following factors can be taken into account

1) noise level

• the lowest - worm gearboxes
• the highest - in cylindrical and conical gearboxes

2) Efficiency coefficient

• the highest - in planetary and single-stage cylindrical gearboxes
• the lowest - worm, especially two-stage

Worm gearboxes are preferably used in re-short-term operating modes

3) Material intensity for the same torque values \u200b\u200bon a low-speed shaft

• the lowest is the planetary single-stage

4) Dimensions with identical gear ratios and torque:

• the largest axial - in coaxial and planetary
• the greatest in the direction of perpendicular axes - at cylindrical
• the smallest radials to the planetary.

5) Relative value of rub / (nm) for the same interlineal distances:

• the highest - conical
• the lowest is the planetary

2. Selection of dimensions (sizes) of the gearbox and its characteristics

2.1. Initial data

The kinematic drive diagram containing the following data:

• view of the drive machine (engine);
• required torque on the output shaft T Rem, NHM, or the power of the motor installation r, kW;
• rotation frequency of the input shaft of the gearbox N Bh, rpm;
• frequency of rotation of the output shaft of the gearbox n out, rpm;
• the nature of the load (uniform or uneven, reversible or non-observative, the presence and magnitude of overloads, the presence of jolts, shocks, vibrations);
• required duration of operation of the gearbox in the clock;
• average daily work in the clock;
• the number of inclusions per hour;
• duration of inclusions with a load, PV%;
• environmental conditions (temperature, heat removal conditions);
• duration of inclusions under load;
• radial console load applied in the middle of the landing part of the ends of the output shaft F out and the input shaft F BX;

2.2. When choosing a gabarit of the gearbox, the following parameters calculate:

1) gear ratio

U \u003d n q / n out (1)

The most economical is the operation of the gearbox at a speed of rotation at the entrance of less than 1500 rpm, and in order to more prolonged the reduction of the gearbox, it is recommended to apply the frequency of rotation of the input shaft less than 900 rpm.

The gear ratio is rounded to the desired side to the nearest number according to the table 1.

The table selects the types of gearboxes of satisfying the specified gear ratio.

2) Calculated torque on the output shaft of the gearbox

T q \u003d T Cre x to dignity, (2)

T Rem - the required torque on the output shaft, NHM (source data, or formula 3)

To the dir - the coefficient of operation

With a well-known motor installation power:

T Ref \u003d (p require x U x 9550 x efficiency) / n Vx, (3)

R Reb - Motor Installation Power, kW

n VK - the frequency of rotation of the gearbox input shaft (provided that the motor installation shaft is directly without additional transmission transmits rotation to the input shaft of the gearbox), rpm

U is the gear ratio of the gearbox, formula 1

Efficiency - the efficiency of the reducer

The operating factor is defined as a product of coefficients:

For gear gearboxes:

By dir \u003d to 1 x to 2 x to 3 x to PV X to the roar (4)

For worm gearboxes:

By dir \u003d k 1 x to 2 x to 3 x to PV X to the roar to h (5)

K 1 - Type factor and motor installation characteristics, Table 2

K 2 - Duration Coefficient Table 3

K 3 - ratio of the number of starts Table 4

To PV - Duration Coefficient Table 5

To the roar - the coefficient of reversibility, with non-observe work to the roar \u003d 1.0 with a reversing work to the roar \u003d 0.75

To h - coefficient, taking into account the location of a worm pair in space. When the worm is located under the wheel to h \u003d 1.0, when arranged above the wheel to h \u003d 1.2. When the worm is located on the side of the wheel to h \u003d 1.1.

3) Calculated Radial Cantilever Load on the Output Shaft Gearbox

F out .Rech \u003d F out to dir, (6)

F out - radial console load applied in the middle of the landing part of the end of the output shaft (source data), n

By dir - the coefficient of operation mode (formula 4.5)

3. The parameters of the selected gearbox must satisfy the following conditions:

1) T nom\u003e t calc, (7)

Nom - nominal torque on the output shaft of the gearbox, cited in this catalog in the specifications for each gearbox, NHM

T Settletry torque at the output shaft of the gearbox (Formula 2), NHM

2) F Nome\u003e F out. (8)

F Nom - nominal console load in the middle of the landing part of the ends of the output shaft of the gearbox, driven in the technical characteristics for each gearbox, N.

F out. Honor - calculated radial console load on the output shaft of the gearbox (formula 6), N.

3) R wh.< Р терм х К т, (9)

P ВХ.Sch - estimated power of the electric motor (Formula 10), kW

P TERM - thermal power, the value of which is given in the technical characteristics of the gearbox, kW

K T - temperature coefficient, the meanings of which are shown in Table 6

The calculated power of the electric motor is determined by:

P ВХ.Schch \u003d (t no x n) / (9550 x KPD), (10)

T Ot - the estimated torque on the output shaft of the gearbox (Formula 2), NHM

n out - the frequency of rotation of the output shaft of the gearbox, rpm

Efficiency - efficiency ratio of the gearbox,

A) for cylindrical gearboxes:

• single-stage - 0.99
• two-stage - 0.98
• three-speed - 0.97
• four-stage - 0.95

B) for conical gearboxes:

• single-stage - 0.98
• two-stage - 0.97

C) for conedic-cylindrical gearboxes - as a product of the values \u200b\u200bof the conical and cylindrical parts of the gearbox.

D) For worm gearboxes of efficiency, driven in specifications for each gearbox for each gear ratio.

Buy the worm gearbox, find out the cost of the gearbox, correctly select the necessary components and help with questions arising during operation, the managers of our company will help you.

Table 1

table 2

Leading machine	Generators, elevators, centrifugal compressors, uniformly loaded conveyors, liquid mixers, centrifugal pumps, gear, screw, booms, blowers, fans, filtering devices.	Water treatment facilities, unevenly downloadable conveyors, winches, cable drums, running, swivel, lifting cranes, concrete mixers, furnaces, transmission shafts, cutters, crushers, mills, equipment for the oil industry.	Punching presses, vibration devices, sawmills, rumble, single-cylinder compressors.	Equipment for the production of rubber products and plastics, mixing machines and equipment for shaped rolled products.
Electric motor steam turbine
4, 6-cylinder internal combustion engines, hydraulic and pneumatic engines
1st, 2, 3-cylinder internal combustion engines

Table 3.

Table 4.

Table 5.

Table 6.

cooling	Ambient temperature, with about	Duration of inclusion, PV%.
Reducer without strange cooling.
Reducer with water cooling spiral.