JP2014119047A - Torque limiter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque limiter which is interposed in a drive force transmission passage for transmitting a drive force of a prime motor in which output torque is largely changed depending on a rotation speed of an output shaft, and can obtain a proper torque limit characteristic.SOLUTION: A torque limiter 6 comprises: a drum member 21 arranged at an end of a counter shaft 4 and rotatable integrally with the counter shaft 4; a piston 24 which is slidable to the axial direction via an O-ring 25 at an internal peripheral side of the drum member 21; a spring 23 for energizing the piston 24 to the counter shaft direction; and a friction element 31 arranged at an end of an output shaft 5 and disposed at an internal peripheral side of the drum member 21. A centrifugal hydraulic pressure chamber 40 is defined by the friction element 31 and the drum member 21, and filling oil is supplied to the centrifugal hydraulic pressure chamber 40 via an oil passage 5a formed at the output shaft 5. The torque limit characteristic corresponding to the rotation speed is obtained by a centrifugal force acting on the filling oil.

Description

  The present invention relates to a torque limiter interposed in a driving force transmission path for transmitting a driving force of a prime mover to driving wheels.

  Patent Document 1 discloses a torque limiter applied to a work vehicle, specifically, a combine for harvesting a crop. The torque limiter is interposed in a torque transmission path for transmitting torque from the engine to the working unit, and a transmission is disposed on the lower side of the torque transmission path than the torque limiter. The torque limiter is configured such that the limit torque is changed when the transmission is shifted. With this configuration, it is possible to obtain an appropriate torque limit characteristic according to the speed selected by the transmission.

Japanese Utility Model Publication No. 6-43566

  When an electric motor is used as the prime mover for driving the driving wheels of the vehicle, as shown in FIG. 5, the output torque TRQMOT of the electric motor changes greatly depending on the rotational speed NM, and therefore a constant torque regardless of the rotational speed NM. When the transmission torque is limited by the limit value TRQFIX, the following problems occur. That is, as shown in FIG. 5, when the torque limit value TRQFIX is set to a torque value suitable for the low speed rotation side, an excessive torque limit value is set on the high speed rotation side, and conversely, a torque value suitable for the high speed rotation side is set. Then, the transmission torque is excessively limited on the low speed rotation side. Therefore, when the torque limit value TRQFIX is set as shown in FIG. 5, when excessive torque is reversely input from the drive wheel side, a torque that greatly exceeds the output torque TRQMOT is applied to the motor. When the torque limiter is activated, excessive frictional heat is generated, which may cause damage to the torque limiter.

  Since the torque limiter disclosed in Patent Document 1 changes the torque limit value according to the gear position, the above problem cannot be solved.

  The present invention has been made paying attention to this point, and is interposed in a driving force transmission path for transmitting the driving force of a prime mover whose output torque varies greatly depending on the rotation speed of the output shaft. An object of the present invention is to provide a torque limiter capable of obtaining torque limiting characteristics.

  In order to achieve the above object, the first aspect of the present invention provides a first shaft (4) and a second shaft (5) constituting a driving force transmission path for transmitting the driving force of the prime mover (1) to the driving wheels (10). ) And a torque limiter for limiting the torque transmitted between the first shaft and the second shaft to a torque limit value (TRQLMT) or less, and an end portion of the first shaft (4) A drum member (21) that can rotate integrally with the first shaft, a piston (24) that is slidable in the axial direction via a seal member (25) on the inner peripheral side of the drum member, A spring (23) for urging the piston in the direction of the first shaft (4), and a friction element provided at the end of the second shaft (5) and disposed on the inner peripheral side of the drum member (21) (31), and the friction element (31) and the drum member (21) Defining heart hydraulic chamber (40), the oil from the centrifugal said hydraulic chamber first axis (4) or the second shaft (5), characterized in that the supplied.

  According to a second aspect of the present invention, in the torque limiter of the first aspect, an oil pump (12) driven by the prime mover (1) and oil discharged from the oil pump are supplied to the centrifugal hydraulic chamber (40). ) And an oil passage (5a) provided in the first shaft (4) or the second shaft (5), and the friction element (31) is between the piston (24) And a connecting part (31b) for connecting the friction part to the second shaft (5), and the piston (24) has an annular shape, The annular inner peripheral diameter (D1) is configured to be smaller than the inner peripheral diameter (D2) of the friction part (31a), and a gap (between the coupling part (31b) and the piston (24) ( 30), and the connecting portion (31b) includes the first shaft. Wherein the second shaft side communicating with the communicating holes (31c) are provided with.

  According to a third aspect of the present invention, in the torque limiter according to the first or second aspect, the prime mover is an electric motor (1).

  According to a fourth aspect of the present invention, in the torque limiter according to any one of the first to third aspects, the outer peripheral side and the inner peripheral side of the drum member are communicated with the side wall (21b) of the drum member. A communication hole (21c) is provided, and the axial position of the communication hole overlaps with the axial position of the spring (23).

  According to the first aspect of the present invention, the centrifugal force acting on the oil in the centrifugal hydraulic chamber changes according to the rotational speed of the prime mover, and the torque limit value can be set in accordance with the rotational speed of the prime mover. Become. As a result, for example, it is possible to appropriately set a torque limit value for blocking a large reverse torque input from the drive wheel side, and to prevent an excessive load from being applied to the torque limiter. Moreover, since an excessive load can be avoided, the torque limiter can be reduced in size and weight.

  According to the second aspect of the present invention, the gap is provided between the connecting portion and the piston, and the connecting portion is provided with a communication hole communicating with the first shaft side and the second shaft side. The oil flows into the gap between the friction element and the piston through the communication hole, and the torque limit value can be set appropriately according to the hydraulic pressure in the centrifugal hydraulic pressure chamber.

  According to the invention described in claim 3, while the output torque of the motor tends to decrease as the rotational speed increases, the centrifugal force acting on the oil in the centrifugal hydraulic chamber increases as the rotational speed of the motor increases. Reduce the torque limit value. Therefore, a torque limiting characteristic suitable for the motor output torque characteristic can be achieved.

  According to the fourth aspect of the present invention, since the oil flowing out from the centrifugal hydraulic chamber is discharged via the communication hole provided in the side wall of the drum member, the oil stays in the vicinity of the spring installation position of the drum member. Thus, an increase in centrifugal force applied to the drum member can be prevented.

It is a skeleton figure of the vehicle drive device containing the torque limiter concerning one Embodiment of this invention. It is sectional drawing which shows the structure of a torque limiter. It is a figure which expands and shows a part of FIG. It is a figure which shows the relationship between the rotational speed (NM) of an electric motor, the output torque (TRQMOT) of an electric motor, and the torque limit value (TRQLMT) of a torque limiter. It is a figure for demonstrating the subject of a prior art.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a skeleton diagram of a vehicle drive device including a torque limiter according to an embodiment of the present invention. The vehicle drive device includes an electric motor 1 and a counter shaft 4 arranged in parallel with an output shaft 2 of the electric motor 1. , An output shaft 5 arranged coaxially with the counter shaft 4, a gear pair 3 including a drive gear 3 a supported by the output shaft 2 of the electric motor 1 and a driven gear 3 b supported by the counter shaft 4, a counter shaft 4 and an output A torque limiter 6 interposed between the shafts 5, and the drive force of the output shaft 5 is configured to drive the drive wheels 10 via the final gear 7, the differential gear mechanism 8, and the drive shaft 9. Has been. The output shaft 2 of the electric motor 1 is connected to the drive shaft 12 a of the oil pump 12 via the transmission mechanism 11, and the oil pump 12 is driven by the electric motor 1.

  FIG. 2 is a cross-sectional view showing the configuration of the torque limiter 6. The torque limiter 6 is provided at the end of the counter shaft 4 and can rotate integrally with the counter shaft 4, and the inner peripheral side of the drum member 21. The piston 24 is slidable in the axial direction (left-right direction in the figure) via the O-ring 25, the plurality of springs 23 for biasing the piston 24 in the direction of the counter shaft 4, and the end of the output shaft 5. And a friction element 31 disposed on the inner peripheral side of the drum member 21 and on the counter shaft 4 side of the piston 24.

  The drum member 21 has a cylindrical shape constituted by a bottom wall 21a and a side wall 21b. The side wall 21b is provided with a communication hole 21c that communicates the outer peripheral side and the inner peripheral side of the drum member 21. The communication hole 21 c is arranged so that its axial position overlaps with the axial position of the spring 23. The friction element 31 has a disk-like shape including a friction part 31a that contacts the piston 24 and can transmit torque between the piston 24, and a connection part 31b that connects the friction part 31a to the output shaft 5. The connecting portion 31b is provided with a communication hole 31c that connects the counter shaft 4 side and the output shaft 5 side. In addition, when a larger engagement force (friction area × surface pressure) via the friction portion 31 a is required, the friction portion 31 a may be configured to contact the bottom wall 21 a of the drum member 21.

  The piston 24 has an annular shape, and the inner peripheral diameter D1 of the annular shape is smaller than the inner peripheral diameter D2 of the friction portion 31a, and a gap 30 is provided between the coupling portion 31b and the piston 24. Is provided. The spring 23 is interposed between the flange 22 fixed to the side wall 21b of the drum member 21 and the piston 24, and a plurality of the springs 23 are arranged at equal angular intervals in the circumferential direction (for example, four at intervals of 90 degrees).

  An oil passage 5 a is provided inside the output shaft 5, and the oil passage 5 a is connected to a discharge hole of the oil pump 12 through a filling oil supply passage 13. A centrifugal hydraulic chamber 40 is defined by the friction element 31 and the drum member 21, and the centrifugal hydraulic chamber 40 is connected to the oil passage 5a. An oil reservoir 41 is provided at the bottom of a casing (not shown) that accommodates the torque limiter 6, and the oil reservoir 41 is connected to the oil pump 12 via the return oil passage 14.

  When the electric motor 1 is operated and the oil pump 12 is driven, the filling oil is supplied to the centrifugal hydraulic chamber 40 via the filling oil supply passage 13 and the oil passage 5a. The filling oil supplied to the centrifugal hydraulic chamber 40 flows out from the communication hole 31c of the connecting portion 31b, reaches the oil reservoir 41 through the gap 30 between the piston 24 and the connecting portion 31b, and the communication hole 21c, and returns to the oil passage 41. 14 is returned to the oil pump 12. The hole diameter of the communication hole 31c provided in the connecting portion 31b of the friction element 31 is adjusted so as to obtain a desired torque limiting characteristic (see FIG. 4, curve L1).

FIG. 3 is an enlarged view of a part of FIG. 2, and the operation of the torque limiter 6 according to the rotational speed NM of the electric motor 1 will be described with reference to FIGS. 2 and 3.
When the electric motor 1 is in a stopped state, the filling oil is not supplied to the centrifugal hydraulic chamber 40, so that the piston 24 and the friction portion 31a are in the maximum surface pressure state (the state in which the engagement force between them is maximum). In this state, the torque limiter 6 operates at the basic torque limit value TRQPG determined by the urging force of the spring 23. That is, the operation is performed so that the transmission torque TRQTR is equal to or less than the basic torque limit value TRQSPG.

  In the low-speed rotation state of the electric motor 1, the filling oil is supplied to the centrifugal hydraulic chamber 40, the hydraulic pressure in the centrifugal hydraulic chamber 40 is increased by the centrifugal force acting on the filling oil in the centrifugal hydraulic chamber 40, and the filling oil passes through the communication hole 31c. And flows into the gap 30 between the connecting portion 31b and the piston 24, and reduces the surface pressure (engagement force) between the piston 24 and the friction portion 31a against the biasing force of the spring 23. As a result, the torque limiter 6 operates at the low speed torque limit value TRQLMT1 (<TRQSPG) determined by the biasing force of the spring 23 and the relatively small centrifugal force acting on the filling oil.

  In the high-speed rotation state of the electric motor 1, the centrifugal force acting on the filling oil in the centrifugal hydraulic chamber 40 increases, and the surface pressure (engagement force) between the piston 24 and the friction portion 31a is further increased against the biasing force of the spring 23. Reduce. As a result, the torque limiter 6 operates at a high speed torque limit value TRQLMT2 (<TRQLMT1) determined by the urging force of the spring 23 and a relatively large centrifugal force acting on the filling oil.

  FIG. 4 is a diagram showing the relationship between the rotational speed NM of the electric motor 1 and the output torque TRQMOT of the electric motor 1 and the torque limit value TRQLMT of the torque limiter 6. According to the torque limiter 6 of this embodiment, the rotational speed NM Corresponding to the change, the torque limit value TRQLMT changes as shown by the curve L1, and the torque limit value TRQLMT decreases corresponding to the decrease in the motor output torque TRQMOT shown by the curve L0 as the rotational speed NM increases. Torque limiting characteristics can be obtained.

  A curve L2 indicates a component (hereinafter referred to as “centrifugal hydraulic torque TRQCF”) that decreases the torque limit value TRQLMT due to an increase in centrifugal force acting on the filling oil as the rotational speed NM increases. The centrifugal hydraulic torque TRQCF takes a negative value, and its absolute value increases as the rotational speed NM increases. The straight line L3 indicates the basic torque limit value TRQSPG by the spring 23, and the torque limit value TRQLMT corresponds to the sum of the basic torque limit value TRQPG and the centrifugal hydraulic torque TRQCF.

  As described above, in the present embodiment, the centrifugal force acting on the filling oil in the centrifugal hydraulic chamber 40 changes according to the rotational speed NM of the electric motor 1, and the torque limit value TRQLMT is set corresponding to the rotational speed NM of the electric motor 1. It becomes possible to set. As a result, for example, a torque limit value for blocking a large reverse torque input from the drive wheel side can be set appropriately, and an excessive load can be prevented from being applied to the torque limiter 6. Moreover, since an excessive load can be avoided, the torque limiter 6 can be reduced in size and weight.

  Further, a gap 30 is provided between the connecting portion 31b and the piston 24, and further, a connecting hole 31c is provided in the connecting portion 31b, so that the filling oil flows into the gap 30 through the connecting hole 31c, The torque limit value TRQLMT can be appropriately set according to the hydraulic pressure in the centrifugal hydraulic chamber 40.

  Further, the output torque of the electric motor 1 tends to decrease as the rotational speed NM increases, while the centrifugal force acting on the filling oil in the centrifugal hydraulic chamber 40 increases as the rotational speed NM increases and decreases the torque limit value TRQLMT. . Therefore, as shown in FIG. 4, a torque limiting characteristic suitable for the motor output torque characteristic can be achieved.

  Further, since the filling oil flows out of the drum member 21 through the communication hole 21c provided in the side wall 21b of the drum member 21, the filling oil flowing out from the centrifugal hydraulic chamber 40 is near the position where the spring 23 of the drum member 21 is installed. It is possible to prevent the centrifugal force that is accumulated and applied to the drum member 21 from increasing.

  In the present embodiment, the counter shaft 4 and the output shaft 5 correspond to a first shaft and a second shaft, respectively, and the O-ring 25 corresponds to a seal member.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the embodiment described above, the oil passage 5a is provided in the output shaft 5 (driven shaft) and the filling oil is supplied to the centrifugal hydraulic chamber 40, but the oil passage is provided in the counter shaft 4 (drive shaft). Filling oil may be supplied to the centrifugal hydraulic chamber 40.

  In addition, the friction element 31 is fixed to the shaft end of the output shaft 5 (driven shaft), and the drum member 21 is fixed to the shaft end of the counter shaft 4 (drive shaft). The drum member 21 may be fixed to the counter shaft 4 and the friction element 31 may be fixed to the shaft end of the counter shaft 4.

1 Electric motor (motor)
4 Counter axis (first axis)
5 Output shaft (second axis)
21 Drum member 21c Communication hole 23 Spring 24 Piston 25 O-ring (seal member)
31 Friction element 31a Friction part 31b Connection part 31c Communication hole

Claims (4)

Torque is transmitted between the first shaft and the second shaft, which is interposed between the first shaft and the second shaft constituting the driving force transmission path for transmitting the driving force of the prime mover to the drive wheels. In the torque limiter that limits below the limit value,
A drum member provided at an end of the first shaft and rotatable integrally with the first shaft;
A piston slidable in the axial direction via a seal member on the inner peripheral side of the drum member;
A spring for urging the piston in the first axial direction;
A friction element provided at an end of the second shaft and disposed on an inner peripheral side of the drum member;
A centrifugal hydraulic chamber is defined by the friction element and the drum member,
A torque limiter characterized in that oil is supplied to the centrifugal hydraulic chamber from the first shaft or the second shaft. An oil pump driven by the prime mover;
An oil passage provided in the first or second shaft for supplying oil discharged from the oil pump to the centrifugal hydraulic chamber;
The friction element is composed of a friction part capable of transmitting torque to and from the piston, and a connection part for connecting the friction part to the second shaft,
The piston has an annular shape, and the inner circumferential diameter of the annular shape is smaller than the inner circumferential diameter of the friction portion, and a gap is provided between the coupling portion and the piston.
2. The torque limiter according to claim 1, wherein the connection portion is provided with a communication hole communicating with the first shaft side and the second shaft side.   The torque limiter according to claim 1, wherein the prime mover is an electric motor.   The side wall of the drum member is provided with a communication hole that communicates the outer peripheral side and the inner peripheral side of the drum member, and the axial position of the communication hole overlaps with the axial position of the spring. The torque limiter according to any one of claims 1 to 3.

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