JP2003113874A - Power transmission device for electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an electric motor and the functions related thereto from the overspeed at a low cost. SOLUTION: A power transmission device comprises the electric motor 25, a speed reducing mechanism 27 to reduce the drive force, and a differential device 31 to distribute the reduced drive force to a wheel side, and a torque limiter 29 is disposed between the speed reducing mechanism 27 and the electric motor 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle that uses an electric motor as a driving force source, and a four-wheel vehicle that uses both a fuel engine (a normal engine utilizing fuel explosion) and an electric motor as a driving force source. The present invention relates to a power transmission device for an electric motor used in a drive hybrid electric vehicle or the like.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 9-226394 discloses an electric vehicle drive device 501 as shown in FIG.

This electric vehicle drive device 501 is composed of an electric motor 503, a speed reduction mechanism 505, a differential device 507 and the like.

The electric motor 503 is rotated by the electric power of an on-vehicle battery, and its driving force is decelerated by the speed reduction mechanism 505 to the range of rotational speed of the wheels to amplify the torque and distributed from the differential device 507 to the left and right wheel sides. .

[0005]

However, this electric vehicle drive device 501 is used in a hybrid four-wheel drive vehicle in which a fuel engine and an electric motor are used together as a drive force source, and is used as an auxiliary drive force source. While a certain electric motor is stopped and the vehicle is driven by the fuel engine that is the main driving force source, the wheels on the side of the electric motor 503 cause the electric motor 50 to rotate.
Since 3 is mechanically rotated, an electromotive force is generated in the state of the generator, and an extra load is applied to the bearing of the electric motor 503, and durability is reduced.

The mechanical rotation of the electric motor 503 is
Since the speed is increased by passing through the speed reduction mechanism 505 in the opposite direction,
The electromotive force is amplified and the battery or a circuit element such as a regulator composed of an integrated circuit is overloaded,
Normal functions may be impaired, leading to reduced durability.

In order to prevent such a situation, a protective measure for short-circuiting the electromotive force of the electric motor 503 is necessary, which increases the cost.

In addition, an electric motor power connection / disconnection device such as the electric vehicle drive device 501 is provided with an engagement / disconnection mechanism such as a clutch between the electric motor and the differential device, and is used except when traveling by the electric motor. There is a structure in which the rotation of the wheels is blocked by an interrupting mechanism to protect the electric motor.

However, in such a structure, an interrupting mechanism and its control system are required, which increases the cost, and if the interrupting mechanism fails, the same problems as described above occur.

Therefore, an object of the present invention is to provide a power transmission device for an electric motor which can protect the electric motor and its related functions from the accompanying rotation of wheels and which is constructed at an extremely low cost.

[0011]

According to a first aspect of the present invention, there is provided a power transmission device for an electric motor, wherein a reduction mechanism for reducing the driving force of the electric motor and a differential device for distributing the driving force reduced by the reduction mechanism to the wheel side. And a torque limiter arranged between the speed reduction mechanism and the electric motor to cut off the driving force when the target index exceeds a predetermined value and transmit the driving force when the target index falls below the predetermined value. I am trying.

In the case of the power transmission device for an electric motor according to the present invention, the target index of the torque limiter is, for example, the rotational speed (the traveling speed of the vehicle) or the driving torque, and the traveling of the vehicle assumed during normal traveling is performed. The torque limiter is set so as not to operate (disengage) within the range of changes in speed (rotational speed of the torque limiter portion) and drive torque.

Taking the case where the target index is the rotational speed as an example, the driving force of the electric motor is decelerated by the reduction mechanism within the assumed traveling speed range in which the torque limiter does not operate, the torque is amplified and transmitted to the differential device. Are distributed to the left and right wheels.

When excessive rotation (high-speed rotation exceeding the rotation speed range corresponding to the assumed traveling speed) occurs due to the wheel turning, a torque limiter arranged between the reduction mechanism and the electric motor operates. The connection is released and the accompanying rotation of the wheels is cut off from the electric motor.

In this way, the circuit elements such as the electric motor, the battery, and the regulator composed of the integrated circuit are protected from the accompanying rotation and the durability is improved, and it is necessary to take a protective action to short-circuit the electromotive force of the electric motor. It is possible to avoid the increase in costs associated with this.

Also, the bearing of the electric motor is released from an extra burden, and the durability is improved.

Further, the torque limiter which operates in response to the rotation speed and the driving torque is delayed in operation (time lag).
Because of small, the response of disconnection and connection is extremely fast.

Further, since the torque limiter has a small difference between the rotational speed and the driving torque at the time of disconnection and at the time of connection, the disconnection and the connection are performed with such accurate rotational speed (vehicle running speed) and drive torque. .

Due to these reasons, the above-mentioned protection function for the electric motor and the like is further improved.

Further, since the torque limiter which operates in response to the rotation speed and the driving torque does not require a control system,
The power transmission device for an electric motor of the present invention is constructed at an extremely low cost.

Further, in the structure in which the discontinuing mechanism such as the clutch is arranged between the electric motor and the differential device, even if the discontinuing mechanism is malfunctioned, the above-mentioned protection function by the torque limiter can be obtained, so that the vehicle speed can be increased. Normal driving is possible without restrictions.

The invention of claim 2 is the power transmission device for an electric motor according to claim 1, wherein the speed reduction mechanism is
A plurality of shaft sets including a first shaft connected to the output shaft side of the electric motor, and a reduction gear set disposed between the shafts of the shaft sets. The torque limiter is provided on the first shaft. It is characterized in that it is arranged at the same time, and it is possible to obtain the same operation and effect as the constitution of claim 1.

Further, the first shaft connected to the output shaft of the electric motor is the input side end of the reduction mechanism, and the rotation speed due to the accompanying rotation of the wheels becomes the highest, so that the first shaft rotates. This is the most sensitive area for speed.

Therefore, for example, if the first shaft is composed of two shafts and a torque limiter is arranged between these shafts, the torque limiter operates with high sensitivity, and the above-mentioned operation for an electric motor or the like is performed. Maximum protection function.

By disposing the torque limiter on the first shaft connected to the output shaft of the electric motor,
Because it can be controlled by directly sensing the rotation speed of the electric motor,
The protection function for electric motors etc. is further enhanced.

A third aspect of the present invention is the power transmission device for an electric motor according to the first or second aspect, wherein the torque limiter returns to the connected state with a target index of a predetermined value or less, and the driving force is reduced. It is characterized in that it has an automatic return function for transmitting the above, and it is possible to obtain the same operation and effect as the constitution of claim 1 or claim 2.

Further, in this configuration using the torque limiter which returns to the connected state when the target index becomes equal to or less than the predetermined value, a control system for connecting the torque limiter by detecting that the target index becomes equal to or less than the predetermined value is unnecessary. Therefore, the structure is simplified and the cost is reduced.

An invention according to claim 4 is the power transmission device for an electric motor according to any one of claims 1 to 3, wherein the torque limiter is a centrifugal clutch. It is possible to obtain the same actions and effects as the configurations of 3 to 3.

According to a fourth aspect of the present invention, a centrifugal clutch having a rotational speed as a target index is used in a torque limiter. Since the centrifugal clutch reacts with high sensitivity to the rotational speed, it protects an electric motor or the like. The function is extremely large.

[0030]

DETAILED DESCRIPTION OF THE INVENTION A power transmission device 1 for an electric motor (one embodiment of the present invention) will be described with reference to FIGS. 1 and 2.

A power transmission device 1 for an electric motor is defined by claim 1.
It has the characteristics of 2, 3 and 4. Also, in the following description, the left and right directions are the left and right directions in FIGS. 1 and 2.

FIG. 2 shows a power system of a four-wheel drive vehicle using a power transmission device 1 for an electric motor (hereinafter, power transmission device 1).

This four-wheel drive vehicle is a hybrid electric vehicle in which an engine and an electric motor are used together as a driving force source, and a front wheel power system using the engine as the driving force source and an electric motor as the driving force source. The power transmission device 1 is used for the rear wheel side power system.

The power system on the front wheel side includes a horizontally installed engine 3, a transmission 5, a front differential 7 (a differential device for distributing the driving force of the engine to the left and right front wheels),
It is composed of front axles 9 and 11, left and right front wheels 13 and 15, and the like.

The power system on the rear wheel side is, as shown in FIGS. 1 and 2, a power transmission device 1, rear axles 17, 19, left and right rear wheels 2.
1, 23, etc.

Further, the power transmission device 1 includes an electric motor 2
5, a reduction mechanism 27, a centrifugal clutch 29 (torque limiter), a rear differential 31 (a differential device that distributes the driving force of the engine to the left and right rear wheels) having a function of interrupting the driving force, a battery 33, a sensor 35, and a controller 3.
It is composed of 7 etc.

As shown in FIG. 1, the power transmission device 1 is housed in a casing 39. The casing 39 is composed of a casing body 41 and a cover 43, and the cover 43 is fixed to a left opening portion of the casing body 41 by a bolt 45. Further, the casing 39 is provided with an oil reservoir.

The electric motor 25 is fixed to the right end of the casing body 41 by a bolt 47.

A first shaft 49 (first shaft connected to the output shaft of the electric motor) is arranged coaxially with the electric motor 25 inside the casing body 41. The first shaft 49 has a coaxial structure of a right shaft 51 and a left shaft 53. The right shaft 51 has a ball bearing 55 at the right end, and the left shaft 53 has a ball bearing 57 at the left end.
Are respectively supported by the casing body 41.

The right shaft 51 and the left shaft 53 are provided with ball bearings 63, which are arranged between a hollow large diameter portion 59 formed on the left shaft 53 and a small diameter portion 61 formed on the right shaft 51.
63 support each other and center each other.

Large diameter hole 6 formed at the right end of the right shaft 51
A hub 69 having a spline 67 is welded to the shaft 5, and an output shaft 71 (FIG. 2) of the electric motor 25 is connected to the right shaft 51 via the spline 67.

An oil seal 73 is arranged between the right shaft 51 and the casing body 41 to prevent oil leakage to the outside (especially, the electric motor 25 side).

The electric motor 25 is connected to the battery 33 via the controller 37, and the controller 3
7 is an electric motor 25 based on the information from the sensor 35.
Drive, rotation speed adjustment, drive stop, etc.

Further, during normal traveling, the controller 37 stops the driving of the electric motor 25 and shuts off the driving force by the rear differential 31 to stop the rotation of the rear wheel side power system, and at the same time, the front wheels 13 and 15 are driven by the engine. The vehicle is driven by 3 to bring the vehicle into a two-wheel drive state by the front wheel side power system.

When a large driving force is required, the controller 37 drives the electric motor 25 and connects the rear differential 31 to operate the rear wheel side power system,
23 is driven auxiliary to bring the vehicle into the four-wheel drive state.

The reduction gear mechanism 27 includes a two-stage reduction gear set 75,
It is composed of 77.

The reduction gear set 75 is composed of a small diameter gear 79 and a large diameter gear 81 which mesh with each other, and the reduction gear set 77 is composed of a small diameter gear 83 and a large diameter gear 85 which mesh with each other.

The small diameter gear 79 of the reduction gear set 75 is the left shaft 5
3 is integrally formed on the left end portion of the third large gear 81
It is press-fitted on the shaft 87.

The left end side of the second shaft 87 is the ball bearing 8
9 is supported on the cover 43, and the right end is supported on the casing body 41 by a ball bearing 91. An oil seal 93 is arranged between the second shaft 87 and the cover 43 to prevent oil leakage to the outside.

The small diameter gear 83 of the reduction gear set 77 is the second shaft 8
7 is integrally formed, and the large diameter gear 85 is a rear differential 31.
Is welded to the left end of the outer differential case 95 (differential case: third shaft).

A plurality of sets of the centrifugal clutch 29 are arranged at equal intervals in the circumferential direction between the right shaft 51 and the left shaft 53 of the first shaft 49, and the screw holes 97, the balls 99, the coil springs 101, and the bolts are respectively arranged. 103 and a hemispherical engagement hole 105 (cam surface).

Each screw hole 97 is formed in the large diameter portion 59 of the left shaft 53, the ball 99 and the coil spring 101 are mounted in this order in the screw hole 97, and then the bolt 103 is screwed into the screw hole 97. The coil spring 101 is appropriately bent.

Further, the engagement holes 105 are formed in the small diameter portion 61 of the right shaft 51 at equal intervals in the circumferential direction, and the balls 9 are formed.
9 is pressed toward the engagement hole 105 side by the biasing force of the coil spring 101.

FIG. 1 shows a state in which each ball 99 is engaged with each engaging hole 105 and the centrifugal clutch 29 is connected. When the centrifugal clutch 29 is connected, the right shaft 51 and the left shaft 53 of the first shaft 49 are connected, and the driving force of the electric motor 25 is transmitted to the speed reduction mechanism 27 side.

When the engagement between the ball 99 and the engagement hole 105 is released, the connection of the centrifugal clutch 29 is released,
The rotation transmitted through the reduction gear mechanism 27 by the rotation of the rear wheels 21, 23 is cut off from the electric motor 25.

Vehicle traveling speed (rotational speed of the first shaft 49:
When the target index) exceeds the set value, the centrifugal force of the ball 99 becomes larger than the biasing force of the coil spring 101, and the ball 99
Moves outward in the radial direction, the engagement between the ball 99 and the engagement hole 105 is released, and the centrifugal clutch 29 is connected (right shaft 51
And the left side shaft 53) are released.

Vehicle traveling speed (rotational speed of the first shaft 49)
Is less than the set value, the ball 99 engages with the engagement hole 105 by the urging force of the coil spring 101, the centrifugal clutch 29 returns to the connected state, and the right shaft 51 and the left shaft 53 are connected.

The balance between the mass of the ball 99 and the urging force of the coil spring 101 is adjusted so that the centrifugal clutch function does not operate in the range where the traveling speed of the vehicle (the rotation speed of the first shaft 49) is less than or equal to the above set value. Has been done.

When the centrifugal clutch 29 is engaged, the driving force of the electric motor 25 is decelerated by the reduction gear sets 75 and 77 to the traveling rotational speed range of the rear wheels 21 and 23, the torque is amplified, and the outer differential case of the rear differential 31. Rotate 95.

The rear differential 31 is composed of a power connection / disconnection device 107, a bevel gear type differential mechanism 109, and the like.

The power connection / disconnection device 107 includes an outer differential case 95, an inner differential case 111, a multi-plate type main clutch 113, a ball cam 115, a pressure plate 117, a cam ring 119, a multi-plate type pilot clutch 121, a return spring 123, and an armature 1.
25, electromagnet 127, controller 37 and the like.

The large diameter gear 85 portion of the outer differential case 95 is supported on the inner differential case 111 by ball bearings 129 and 129. The outer differential case 95 only transmits torque by the large diameter gear 85,
It has a floating structure that is released from the function of supporting the members.

In the inner differential case 111, the left boss portion 131 is supported by the cover 43 by the ball bearing 133, and the right boss portion 135 is supported by the ball bearing 137.
And the core 139 of the electromagnet 127, and is supported by the casing body 41. The core 139 is fixed to the casing body 41.

The right boss portion 135 (inner differential case 111) has a rotor 14 made of a magnetic material on the outer periphery thereof.
1 is fixed by a snap ring 143 and positioned in the axial direction. The rotor 141 also serves as the right side wall member of the outer differential case 95.

The main clutch 113 is arranged between the outer differential case 95 and the inner differential case 111. The outer plate 145 is spline-connected to the inner circumference of the outer differential case 95, and the inner plate 147 is spline-connected to the outer circumference of the inner differential case 111.

The pilot clutch 121 is arranged between the outer differential case 95 and the cam ring 119. The outer plate 149 is spline-connected to the inner circumference of the outer differential case 95, and the inner plate 151 is spline-connected to the outer circumference of the cam ring 119.

The ball cam 115 is arranged between the pressure plate 117 and the cam ring 119. The pressure plate 117 is the inner differential case 111.
The spline is connected to the outer periphery of the so as to be movable in the axial direction,
As described below, the main clutch 113 is pressed by the cam thrust force of the ball cam 115.

A thrust bearing 153 is arranged between the cam ring 119 and the rotor 141 to receive the cam reaction force of the ball cam 115 and absorb the relative rotation between the cam ring 119 and the rotor 141.

The return spring 123 is arranged between the pressure plate 117 and the inner differential case 111, and urges the pressure plate 117 in the disengagement direction of the main clutch 113.

The armature 125 is formed in a ring shape, and is arranged between the pressure plate 117 and the pilot clutch 121 (inner plate 151) so as to be movable in the axial direction. Further, the inner periphery of the armature 125 has a step portion 1 formed on the pressure plate 117.
It is supported on the outer periphery of 55 so as to be relatively rotatable and centered.

The lead wire of the electromagnet 127 is drawn out of the casing main body 41 via a grommet and is connected to the battery 33 side by a connector.

The core 139 of the electromagnet 127 and the rotor 141
A proper air gap is formed between the air gap, the rotor 141, and the pilot clutch 12.
1. The magnetic path of the electromagnet 127 is constituted by the armature 125.

When the electromagnet 127 is excited, a magnetic flux loop 157 is formed on this magnetic path.

The differential mechanism 109 is composed of a plurality of pinion shafts 159, a pinion gear 161, output side gears 163, 165, and the like.

The pinion shafts 159 are arranged radially from the center of rotation of the inner differential case 111,
The tip of each is the engagement hole 1 of the inner differential case 111.
It is engaged with 67 and is prevented from rotating by the step portion 169.

Each pinion gear 161 is rotatably supported on each pinion shaft 159, and the side gears 163, 165 mesh with the pinion gear 161 from the left and right. Between the side gears 163, 165 and the inner differential case 111, the side gears 163, 1
Thrust washers 171 that receive the meshing reaction force of 65 are arranged.

The side gears 163 and 165 are spline-coupled to the left and right rear axles 17 and 19, respectively, and the rear axles 17 and 19 are the left and right boss portions 131 and 135 of the inner differential case 111, the cover 43, and the casing body 41.
And are respectively connected to the left and right rear wheels 21 and 23.

Oil seals 173 are respectively provided between the rear axles 17, 19 and the cover 43 and the casing body 41.
Is placed to prevent oil leakage to the outside.

The rotation of the inner differential case 111 is distributed from the pinion shaft 159 to the side gears 163 and 165 via the pinion gear 161 and further the rear axle 1
The signals are transmitted from 7, 19 to the left and right rear wheels 21, 23.

When a driving resistance difference occurs between the rear wheels 21 and 23 on a bad road or the like, the driving force of the electric motor 25 is differentially distributed to the left and right rear wheels 21 and 23 by the rotation of the pinion gear 161. .

The controller 37 performs the excitation of the electromagnet 127, the control of the excitation current, and the stop of the excitation in accordance with the road conditions, the traveling conditions such as starting, acceleration, turning of the vehicle and the steering conditions.

The excitation of the electromagnet 127 is performed simultaneously when the electric motor 25 is rotated, and the excitation of the electromagnet 127 is stopped simultaneously when the rotation of the electric motor 25 is stopped.

When the electromagnet 127 is excited, the above-mentioned magnetic flux loop 157 attracts the armature 125 and presses and engages the pilot clutch 121 with the rotor 141 to generate a pilot torque.

When the pilot torque is generated, the cam ring 119 connected to the outer differential case 95 by the pilot clutch 121 and the inner differential case 11 are connected.
The driving force of the electric motor 25 is applied to the ball cam 115 via the pressure plate 117 on the first side, and the ball cam 115 converts the driving force into a cam thrust force while amplifying this driving force, and moves the pressure plate 117 to the left to move the main clutch. 113 is pressed and fastened.

When the power connection / disconnection device 107 is connected in this way, the driving force of the electric motor 25 for rotating the large diameter gear 85 (outer differential case 95) is the same as the inner differential case 1.
11 and the rotation thereof is distributed to the left and right rear wheels 21 and 23 by the differential mechanism 109, so that the vehicle becomes a four-wheel drive state.

At this time, if the exciting current of the electromagnet 127 is controlled, the slip ratio of the pilot clutch 121 changes and the cam thrust force of the ball cam 115 changes, and the rear wheel 2
The driving force transmitted to the 1 and 23 sides is controlled.

If such control of the driving force is performed during turning, for example, turning performance and vehicle body stability can be greatly improved.

When the excitation of the electromagnet 127 is stopped,
The pilot clutch 121 is released and the ball cam 11
The cam thrust force of 5 disappeared, and the return spring 12
The pressure plate 117 is returned to the right by the urging force of No. 3, the main clutch 113 is released, the connection of the power connection / disconnection device 107 is released, and the vehicle enters the two-wheel drive state of front wheel drive.

When the connection of the power connecting / disconnecting device 107 is released, the reduction gear mechanism 27 (outer differential case 95) to the electric motor 25 is cut off from the accompanying rotation of the rear wheels 21 and 23.

The decoupling operation of the power connecting / disconnecting device 107 is performed at the same time as the stopping operation of the electric motor 25 as described above. Therefore, in the two-wheel drive state, the reduction mechanism 27 and the electric motor 25 cause the rear wheels 21 and 23 to operate. It is prevented from being mechanically turned by the accompanying rotation of the.

Therefore, the reduction mechanism 27, the electric motor 25,
Circuit elements such as the battery 33 and a regulator composed of an integrated circuit are protected from adverse effects caused by the rotation of the rear wheels 21 and 23, and durability is improved.

Further, in the two-wheel drive state in which the electric motor 25 is stopped and the connection of the power connection / disconnection device 107 is released, no centrifugal force or drive torque is applied to the reduction mechanism 27 (first shaft 49). Centrifugal clutch 29 arranged on shaft 49
Does not work (disconnect).

Further, in the four-wheel drive state in which the electric motor 25 is driven and the power connection / disconnection device 107 is connected, for example, by the driving force of the front wheel side power system (engine 3) or by the acceleration at the time of downhill, When the rotational speed or the drive torque generated in the first shaft 49 exceeds the above-mentioned set values, the centrifugal clutch 29 is actuated to disconnect the electric motor 25 from the speed reduction mechanism 27 side, and the electric motor 25, the battery 33, the circuit of the regulator and the like. Protects elements from over-rotation.

Further, due to the malfunction of the power interruption device 107,
Even in the two-wheel drive state, even if a situation in which the rotation of the rear wheels 21, 23 cannot be interrupted occurs, the rotation speed and drive of the first shaft 49 are driven by the rotation of the rear wheels 21, 23 transmitted from the reduction mechanism 27 side. When the torque exceeds the set value, the electric motor 25 is released by the deceleration of the centrifugal clutch 29.
Separated from the 7 side.

In this way, the circuit elements such as the electric motor 25, the battery 33, the regulator, the rear wheel 21,
Protected against over-rotation due to the accompanying rotation of 23.

In any case, if the rotational speed of the first shaft 49 or the driving torque applied to the first shaft 49 becomes less than the set value, the centrifugal clutch 2 is urged by the urging force of the coil spring 97.
When 9 is returned to the connected state and the vehicle is driven by four wheels, the driving force of the electric motor 25 is transmitted to the speed reduction mechanism 27 side.

When the large-diameter gear 81 of the reduction gear set 75 rotates, the oil in the oil pool formed in the casing 39 scatters and each gear 7 of the reduction gear sets 75 and 77 is scattered.
9, 81, 83, 85 meshing parts and bearings 55,
Lubricate and cool 57, 63, 89, 91 and the like.

Further, the oil in the oil reservoir is the large diameter gear 8
It is scattered by the rotation of 5, and the bearings 129, 131,
While lubricating and cooling 137, the scattered oil enters through the gaps on the left and right sides of the outer differential case 95 and the inner differential case 111, and slides between the pilot clutch 121, the armature 125 and the pressure plate 117 (step 155), and the ball cam. 115, the thrust bearing 153, the main clutch 113, etc. are lubricated and cooled.

Further, the oil in the oil sump flows in along with the rotation of the inner differential case 111 from the spiral oil groove formed inside the bosses 131 and 135, and each gear 161 of the differential mechanism 109. , 163, 165 are lubricated and cooled, and further centrifugal force is applied to move to the main clutch 113 side.
3. After lubricating and cooling the ball cam 115, pilot clutch 121, etc., the oil returns to the oil sump.

Thus, the power transmission device 1 for an electric motor is constructed.

This power transmission device 1 includes an electric motor 25,
Circuit elements such as the speed reduction mechanism 27, the battery 33, and the regulator are protected by the centrifugal clutch 29 from excessive rotation due to the accompanying rotation of the rear wheels 21 and 23, and the durability is significantly improved.

Further, it is not necessary to take a protective measure for short-circuiting the electromotive force of the electric motor 25, and it is possible to avoid a cost increase accompanying this.

Also, the bearing of the electric motor 25 is released from an extra burden, and the durability is improved.

Further, the centrifugal clutch 29, which operates in response to the rotational speed, has a small operation delay (time lag), and the response of the connection releasing operation and the connection operation is extremely fast.

Further, since the centrifugal clutch 29 has a small difference between the rotational speed at which the connection is released and the rotational speed at which it is connected, and reacts with high sensitivity to the rotational speed, the connection release operation and the connection operation are performed. Each is performed at an accurate rotation speed (vehicle traveling speed).

For these reasons, the above-mentioned protection function for the electric motor and the like is further improved.

Further, since the centrifugal clutch 29 that operates in response to the rotational speed does not require a control system, the power transmission device 1 can be constructed at an extremely low cost.

In addition, the power disconnecting device 107 of the rear differential 31.
Even if the above condition is not satisfied, the centrifugal clutch 29 can provide the above-described protection function for the electric motor and the like, so that normal traveling can be performed without restricting the vehicle speed.

The first shaft 49 connected to the output shaft 71 of the electric motor 25 is the input side end of the reduction mechanism 27, and the rotation speed of the rear wheels 21, 23 is the highest, This is the highest sensitivity to rotation speed.

Therefore, the right shaft 51, which is a division of the first shaft 49,
Since the centrifugal clutch 29 arranged between the left side shaft 53 and the left side shaft 53 reacts with high sensitivity, the above-described protection function for the electric motor 29 and the like is maximized.

By disposing the centrifugal clutch 29 on the output shaft 71 side of the electric motor 25, the electric motor 25
Since the control can be performed by directly sensing the rotational speed of the electric motor, the protection function for the electric motor 25 and the like is further increased.

Further, in the power transmission device 1 using the centrifugal clutch 29 which returns to the connected state at the rotation speed of the predetermined value or less, the torque limiter (centrifugal clutch 29) is connected by detecting the rotation speed of the predetermined value or less. Since no system is required, the construction is simpler and the cost is reduced.

The above embodiment is an example of application to an electric vehicle using an engine as a main driving force source and an electric motor as an auxiliary driving force source. However, the power transmission device for an electric motor according to the present invention is an electric motor. It can also be used in a vehicle that uses a motor as a main driving force source.

Further, the differential device used in the present invention is not limited to the bevel gear type differential device (differential mechanism) as in the embodiment, but can be slidably fitted in the planetary gear type differential device and the accommodation hole of the differential case. Any type of differential device may be used, such as a differential device in which a side gear on the output side is connected by a housed pinion gear or a differential device using a worm gear.

[0115]

The power transmission device for an electric motor of the present invention comprises:
The torque limiter protects the electric motor, battery, circuit elements, etc. from over-rotation due to the accompanying rotation of the wheels, and the durability is greatly improved.

Further, it is not necessary to take a protective measure for short-circuiting the electromotive force of the electric motor, and it is possible to avoid an increase in cost accompanying this.

Also, the bearing of the electric motor is released from an extra burden, and the durability is improved.

Further, the torque limiter has a very quick response of connection and disconnection, and has a small difference in rotational speed and drive torque at the time of connection release and connection. Therefore, the torque limiter has a large protection function for the electric motor and the like.

Further, since the torque limiter does not require a control system, the power transmission device for an electric motor of the present invention is constructed at an extremely low cost.

A power transmission device for an electric motor according to claim 2 is
It is possible to obtain the same effect as the configuration of claim 1.

Further, the torque limiter which operates with high sensitivity provides a high protection function for the electric motor and the like.

Further, since the control can be performed by directly sensing the rotation speed of the electric motor, the protection function for the electric motor is further enhanced.

A power transmission device for an electric motor according to claim 3 is
It is possible to obtain the same effect as the configuration of claim 1 or claim 2.

Further, a control system for detecting a target index equal to or less than a predetermined value and connecting the torque limiter is unnecessary, and the structure is simple and the cost is reduced.

A power transmission device for an electric motor according to claim 4 is
It is possible to obtain the same effects as those of the configurations of claims 1 to 3.

Further, by using the centrifugal clutch, a great protection function for an electric motor or the like can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a skeleton mechanism diagram showing a four-wheel drive vehicle using the embodiment of FIG.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

1 Power transmission device for electric motor 21,23 Rear wheels 25 electric motor 27 Reduction mechanism 29 Centrifugal clutch (torque limiter) 31 Rear differential (differential device) 49 1st axis (frame set) 71 Output shaft of electric motor 25 75,77 reduction gear set

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3D043 AA07 AA10 AB17 EA03 EA05                       EA11 EA42 EE03 EE06 EF21                       EF24                 3J062 AA02 AB36 BA11 BA19 CF17                       CF26 CF34 CF44                 3J068 AA02 AA05 AA07 BA14 BB03                       CA05 CA08 CB03 EE05 EE12                       GA08 GA10 GA14

Claims (4)

[Claims] 1. A deceleration mechanism for decelerating the driving force of an electric motor, and a differential device for distributing the driving force decelerated by the deceleration mechanism to a wheel side, and an object between the deceleration mechanism and the electric motor. A power transmission device for an electric motor, characterized in that a torque limiter is arranged to cut off the driving force when the index exceeds a set value and transmit the driving force when the target index falls below the set value. 2. The invention according to claim 1, wherein the reduction mechanism includes a plurality of shaft sets including a first shaft connected to an output shaft side of the electric motor, and each of the shaft sets. A power transmission device for an electric motor, comprising a reduction gear set arranged between shafts, wherein the torque limiter is arranged on the first shaft. 3. The invention according to claim 1 or 2, wherein the torque limiter has an automatic return function for returning to a connected state and transmitting a driving force at a target index of a predetermined value or less. A power transmission device for an electric motor, characterized in that: 4. The power transmission device for an electric motor according to claim 1, wherein the torque limiter is a centrifugal clutch.