JPH07139610A - Overload absorption mechanism of power transmission device - Google Patents

Abstract

PURPOSE:To absorb any overload applied to a device without enlargement and complication of a power transmission device. CONSTITUTION:The power of a motor is transmitted to an input shaft 12. An input gear 15 and an output gear 16 are formed by a helical gear. A differential case 17 is fitted to the output gear 16. Disc springs 20 are arranged respectively in the space in an axial direction toward a gear case 11a in the bearings 19 so as to allow the movement in the axial direction of the differential case 17. A differential bevel gear device is installed in the differential case 17. The differential bevel gear device is slidable against the output shaft 26. A friction material 21 is installed on the contact surface of the gear case 11a with the output gear 16. A pair of right/left drive wheels are connected respectively to the output shaft 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload absorbing mechanism for a power transmission device which transmits power by helical gears.

[0002]

2. Description of the Related Art Generally, a power transmission device for a battery type forklift has a structure as shown in FIG.

The gear case 31 has an input shaft 3
One end of 2 is supported by a tapered roller bearing 33. Further, since the other end is rotatably supported by the bearing 34, the input shaft 32 is fixed to the gear case 3
It is rotatable with respect to 1. A gear 32a for inputting power of a motor (not shown) to the input shaft 32
Are integrally molded. An input gear 35 is fitted on the input shaft 32 so as to be integrally rotatable.

An output gear 36 having a diameter larger than that of the input gear 35 meshes with the input gear 35. The input gear 35 and the output gear 36 are helical gears.

A differential case 37 is fitted to the output gear 36 with a bolt 38 so that it can rotate integrally with the output gear 36. The differential case 37 has bearings 39 at both ends.
Through the differential part 31a of the gear case 31
It is rotatably supported by. A pinion shaft 40 is fixed to the center of the differential case 37 by a bolt 41 so as to be parallel to the output gear 36, and is integrally rotatable with the differential case 37. At both ends of the pinion shaft 40, a differential pinion gear 42 is provided.
It is possible to rotate integrally with 0 and the pinion shaft 4
It is fitted so that it can rotate about 0 as its central axis.

A pair of left and right differential side gears 43 mesh with the differential pinion gear 42. Output shafts 44 are spline-coupled inside the pair of differential side gears 43, respectively, so that the output shafts 44 can rotate integrally with the differential side gears 43. A pair of left and right drive wheels (not shown) are respectively connected to the pair of output shafts 44, and power is transmitted to the drive wheels to drive the forklift.

With the above structure, the power from the motor (not shown) is transmitted to the input shaft 32 via the gear 32a, and the input shaft 32 rotates. The input gear 35 rotates as the input shaft 32 rotates. The rotation of the input gear 35 is transmitted to the differential case 37 via the output gear 36. As the differential case 37 rotates, the pinion shaft 40 and the differential pinion gear 42 rotate integrally. Then, as the differential pinion gear 42 revolves around the output shaft 44 as the central axis, the differential side gear 43 rotates and the output shaft 44 also rotates. Then, as the output shaft 44 rotates, power is transmitted to drive wheels (not shown), and the forklift travels.

By the way, the drive wheel, that is, the output shaft 44 may be overloaded. For example,
When trying to start with the handbrake applied,
Also, when trying to climb an excessively steep slope. At this time, the overload is also transmitted to the motor, which may cause a failure such as seizure of the motor. Further, in the helical gear composed of the input gear 35 and the output gear 36, since the force to move in the thrust direction becomes large, the differential case 37 causes the bearing 3 to move.
The force of pressing 9 against the gear case 31 becomes large. Therefore, if the overload is repeated, the bearing 39 and the gear case 31 may be damaged.

As a countermeasure against these problems, a torque limiter as an overload preventing device is attached to the output shaft 44. The torque limiter detects the torque applied to the output shaft 44, and when an overload is applied to the output shaft 44, the controller provided in the motor mechanically brakes the torque.
Alternatively, the motor is stopped by turning off the power.

[0010]

However, such an overload prevention device requires two means, a means for detecting an overload on the drive wheels and a means for stopping the motor, and the power transmission device as a whole is large in size. There was a problem of becoming complicated and complicated.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is power transmission capable of absorbing an overload applied to the power transmission without increasing the size or complexity of the power transmission. It is to provide an overload absorbing mechanism for the device.

[0012]

In order to solve the above-mentioned problems, the present invention solves the above problems by using a reduction gear case, an input shaft rotatably supported by the reduction gear case, and a reduction gear fitted to the input shaft. A small gear, a large reduction gear that constitutes a helical gear together with the small reduction gear, a differential gear case fitted to the large reduction gear and rotatably supported with respect to the reduction gear case, and a differential gear In a power transmission device including a differential bevel gear device arranged in a case and a drive shaft rotatably supporting the differential gear case and spline-coupled to the differential bevel gear device, a reduction gear case and a differential gear case are provided. The gist of the invention is that an elastic member is provided axially with the gear case and a friction material is provided on the contact surface between the reduction gear case and the reduction gear or the differential gear case.

[0013]

Therefore, according to the present invention, the power of the input shaft is transmitted to the drive shaft through the helical gear and the differential bevel gear device. When the drive shaft is overloaded, the force generated in the helical gear to move in the axial direction increases. When the force to move in the axial direction increased due to overload becomes larger than the biasing force of the elastic member, the reduction gear wheel moves in the axial direction together with the differential gear case. At this time, the reduction gear is brought into contact with the friction material, so that the axial force is absorbed by the friction material. In addition, even during the transition period when the power from the input shaft decreases, the power due to the inertia is absorbed by the friction material. Then, when the power from the input shaft decreases, the force generated in the helical gear to move in the axial direction becomes smaller than the urging force of the elastic member, and the large reduction gear is moved to the original position by the urging force of the elastic member. Return to.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a power transmission device for a battery type forklift will be described below with reference to FIG. A protection circuit for preventing overcurrent is connected to a DC motor (not shown) (hereinafter referred to as a motor).

The gear case 11 has an input shaft 1
One end of 2 is supported by a tapered roller bearing 13. Further, since the other end is rotatably supported by the bearing 14, the input shaft 12 has the gear case 1
It is rotatable with respect to 1. The input shaft 12 is integrally formed with a gear 12a for inputting the power of the motor. Further, an input gear 15 is fitted to the input shaft 12 so as to be integrally rotatable.

An output gear 16 as a reduction gear having a diameter larger than that of the input gear 15 meshes with the input gear 15. Input gear 1
5 and the output gear 16 are helical gears.

A differential case 17 as a differential gear case is fitted to the output gear 16 with a bolt 18 so that it can rotate integrally with the output gear 16. The differential case 17 is rotatably supported by both ends of the differential case 17 with respect to the differential portion 11a of the gear case 11 via bearings 19.
The bearing 19 is provided with disc springs 20 axially between the bearing 19 and the differential portion 11a of the gear case 11, and is slidable in the axial direction.

The disc spring 20 is mounted so that it does not contract against the force that tends to move in the thrust direction generated in the output gear 16 constituting the helical gear when a normal load is applied to the output side. It is a load. When the output side is overloaded, the disc spring 20 contracts due to the force that is generated in the output gear 16 to move in the thrust direction, so that the differential case 17 and the bearing 19 are allowed to move in the axial direction. Has become.

The output gear 16 also slides in the axial direction together with the differential case 17. On the inner side surface 11b of the differential portion 11a of the gear case 11, which comes into contact with both side surfaces of the output gear 16 when it slides, a ring-shaped friction material 21 having substantially the same diameter as the output gear 16 is provided.
Are attached respectively. The friction material 21 is preferably resistant to wear and has a frictional force, and specifically, urethane rubber, resin or the like can be considered.

A pinion shaft 22 is fixed to the differential case 17 approximately at the center thereof by a bolt 23 so as to be parallel to the output gear 16 so that the pinion shaft 22 can rotate integrally with the differential case 17. A differential pinion gear 24 is integrally rotatable at both ends of the pinion shaft 22 with respect to the pinion shaft 22.
It is fitted so that it can rotate on the axis of 2.

A pair of left and right differential side gears 25 mesh with the differential pinion gear 24. The output shafts 26 are spline-coupled inside the pair of differential side gears 25, respectively, so that the output shafts 26 can rotate integrally with the differential side gear 25 and can slide in the axial direction. Therefore, when the output shaft 26 is overloaded and the force generated in the output gear 16 to move in the thrust direction becomes large, the output gear 1
6, the differential case 17, the pinion shaft 22, the differential pinion gear 24, and the differential side gear 25 (hereinafter referred to as the output gear 16 and the transmission gear) are the output shaft 26.
With respect to the bearing 19, it is slid in the axial direction. In the present embodiment, the pinion shaft 22, the differential pinion gear 24, and the differential side gear 25 constitute a differential bevel gear device.

A pair of left and right drive wheels (not shown) are connected to the output shaft 26, and power is transmitted to the drive wheels so that the forklift can travel.

Next, the operation of the overload absorbing mechanism of the power transmission device for a battery-powered forklift configured as described above will be described. Power from a motor not shown is gear 1
It is transmitted to the input shaft 12 via 2a, and the input shaft 12 rotates. Input shaft 1
The input gear 15 rotates as 2 rotates. The rotation of the input gear 15 depends on the output gear 16
Is transmitted to the differential case 17 via.
As the differential case 17 rotates,
The pinion shaft 22 and the differential pinion gear 24 rotate integrally. As the differential pinion gear 24 revolves around the output shaft 26 as the central axis, the differential side gear 25 rotates and the output shaft 26 rotates.
Rotate together. Then, as the output shaft 26 rotates, power is transmitted to drive wheels (not shown).

By the way, when starting with the hand brake applied, or when trying to climb a steep slope, the drive wheels, that is, the output shaft 26 is overloaded. At this time, the force generated in the output gear 16 that constitutes the helical gear to move in the thrust direction becomes larger than the biasing force of the disc spring 20. Therefore, the output gear 16 and the transmission gear are the bearing 1
9 slides with respect to the output shaft 26 in the axial direction. By sliding the output gear 16 in the axial direction, the force that meshes with the input gear 12 is dispersed in the thrust direction, and damage to the gear is prevented. Then, the thrust force is absorbed by the biasing force of the disc spring 20 and the friction material 21 that comes into contact when the output gear 16 slides in the axial direction.

When the output shaft 26 is overloaded, the motor protection circuit detects an overcurrent flowing through the motor due to the overload, and the motor is turned off or mechanically braked. Try to stop the motor. At this time, the motor does not stop immediately but rotates by the inertia torque. Then, this inertia torque is transmitted to the output gear 16. Since the output gear 16 is in contact with the friction material 21, this inertia torque is absorbed by the friction material 21. Therefore, the motor can be stopped completely, and its inertia torque is transmitted to the output shaft 26 without applying a twisting force.

After that, when the power from the motor decreases,
The force generated in the output gear 16 to move in the thrust direction becomes smaller than the biasing force of the disc spring 20,
The output gear 16 and the transmission gear return to the original position together with the bearing 19.

As described above, according to this embodiment, when the output shaft 26 is overloaded, the output gear 16 moves in the axial direction to disperse the force meshing with the input gear 12 into the thrust force. Then, the force is absorbed by the friction material 21 by the biasing force of the disc spring 20 and the contact of the output gear 16 with the friction material 21. Further, since the inertia torque of the motor is also absorbed by the friction material 21, the motor can be completely stopped and the input gear 12, the output gear 16, the gear case 11 and the bearing 19 due to the overload applied to the output shaft 26. It is possible to prevent damage such as.

Further, the output gear 1 moved in the axial direction
When the power from the motor 6 is reduced, 6 returns to the original position by the urging force of the disc spring 20. Therefore, when the motor is driven again, the work and device for returning the motor are not required.

The present invention is not limited to the above embodiment, but may be modified as follows, for example, without departing from the spirit of the present invention. (1) In the above-described embodiment, a battery-type forklift, that is, a power transmission device of a DC motor is described as an example of the power transmission device, but the power source is not particularly limited. For example, the present invention may be embodied in a power transmission device that uses an engine as a power source.

(2) In the above embodiment, the left and right drive wheels are applied to the power transmission device of the type that is driven by one power source. However, the power drive device of the type in which the left and right drive wheels are driven by independent power sources, respectively. It may be applied to a transmission device.

(3) In the above embodiment, the disc spring 20 is used as the elastic member, but a coil spring or the like may be used instead of the bearing 1 in the differential portion 11a of the gear case 11.
It is also possible to provide a plurality of them at positions facing each other.

(4) In the above embodiment, the friction material 21 is provided on the gear case 11 side, but it may be fixed on the output gear 16 side so as to be integrally rotatable. Further, the friction material 21 may be provided on the contact surface between the gear case 11 and the differential case 17.

(5) In the above-mentioned embodiment, the ring-shaped friction material is used as the friction material 21, but a plurality of tip-shaped friction materials are provided on the circumferential surface of the gear case 11 which contacts the output gear 16. May be.

[0034]

As described above in detail, according to the present invention, there is an excellent effect that an overload applied to a power transmission device can be absorbed without increasing the size or complexity of the device.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment in which the present invention is embodied in an overload absorbing mechanism of a power transmission device for a battery-powered forklift.

FIG. 2 is a cross-sectional view showing a conventional power transmission device for a battery-powered forklift.

[Explanation of symbols]

11 ... Gear case, 12 ... Input shaft, 15 ...
Input gears constituting helical gears, 16 ... Output gears as reduction gears constituting helical gears, 1
DESCRIPTION OF SYMBOLS 7 ... Differential case, 20 ... Belleville spring as an elastic member, 21 ... Friction material, 22 ... Pinion shaft which comprises a differential bevel gear device, 24 ... Differential pinion gear which comprises a differential bevel gear device, 25 ... Differential bevel gear device Differential side gears,
26 ... An output shaft as a drive shaft.

Claims (1)

[Claims] 1. A reduction gear case, an input shaft rotatably supported by the reduction gear case, a reduction small gear fitted to the input shaft, and a helical gear together with the reduction small gear. A reduction gear, a differential gear case fitted to the reduction gear and rotatably supported with respect to the reduction gear case, a differential bevel gear device arranged in the differential gear case, and a differential gear case. In a power transmission device that rotatably supports a gear case and that includes a differential bevel gear device and a drive shaft that is spline-coupled, an elastic member is provided between the reduction gear case and the differential gear case in the axial direction, and deceleration An overload absorbing mechanism for a power transmission device in which a friction material is provided on a contact surface between a gear case and a reduction gear or a differential gear case.