JP5533182B2 - Electric vehicle transmission unit - Google Patents

Description

  The present invention relates to a transmission unit for an electric vehicle that is used for an electric vehicle such as an electric vehicle that only runs electrically with power from an electric motor, or a hybrid vehicle that can run not only with power from an engine but also with power from an electric motor. It is about.

Conventionally, for example, Patent Document 1 has proposed a transmission unit for an electric vehicle.
This electric vehicle transmission unit is not a planetary gear type based on the basic concept of the present invention, but a parallel shaft type transmission unit.
If a low speed stage request is required, such as when the vehicle is starting, the low speed stage selection state of the transmission unit is realized by inactivating and fastening the normally closed low speed stage selection friction element,
When a high speed stage is required, such as during normal driving, the low speed stage selection friction element is hydraulically operated using oil from an oil pump driven by an electric motor as a working medium, and at the same time, the high speed stage A high speed stage selection state of the transmission unit is realized by hydraulically operating the selection friction element to be in a fastening state.

According to such a configuration, when the low speed stage request for the low oil discharge flow rate from the oil pump driven by the rotation speed of the electric motor is low, the low speed stage can be realized without depending on the low oil discharge flow rate. You can
When the rotational speed of the electric motor is high and the oil discharge flow rate from the oil pump driven thereby is high, the high speed stage can be surely realized by this large oil discharge flow rate.

Japanese Patent Laid-Open No. 11-13878

  However, in the above-described conventional transmission unit, when the transmission unit for an electric vehicle is configured as a planetary gear set type transmission unit, the transmission friction element for selecting a low-speed stage is fastened by non-operation and the transmission unit is connected to the low-speed stage. When the selected state is set, the oil consumption is small and the above-described effects can be obtained, but the following problems cannot be forbidden.

In other words, in the case of a planetary gear set type transmission unit, normally, the planetary gear in the transmission unit is brought into a low speed stage selection state by bringing it into a state of revolving while rotating.
The planetary gear rotating bearings (bearings, etc.) revolving while rotating in this manner require sufficient lubrication because the planetary gear rotates at a relatively high speed even when the low speed stage is selected.

However, when the low speed stage is selected, the actual number of rotations of the oil pump is so low that the amount of oil discharged from the oil pump is small, and the amount of oil required by the rotation support portion of the planetary gear cannot be covered.
For this reason, the rotation support part of the planetary gear becomes poorly lubricated due to insufficient oil amount, and there arises a problem that the durability here, and consequently the durability of the transmission unit for an electric vehicle deteriorates.

The present invention is based on the fact that the above problem is caused by the rotation of the planetary gear when the low speed stage is selected.
An electric vehicle that avoids the above-described problems related to poor lubrication by eliminating the need for lubrication of the planetary gear rotation support portion so as not to cause rotation of the planetary gear when the low speed stage is selected. The purpose is to propose a transmission unit for a vehicle.

For this purpose, the transmission unit for an electric vehicle according to the present invention is configured as follows.
First, to explain the electric vehicle transmission unit that is the premise of the present invention,
Having a planetary gear, comprising a planetary gear set capable of selecting a low speed stage and a high speed stage with a higher gear ratio than the low speed stage;
A travel drive motor is coupled to the input element of the planetary gear set, and a drive wheel is coupled to the output element;
The oil from the oil pump driven by the transmission system between the travel drive motor and the drive wheels is operated as a working medium.

The present invention provides a low-speed stage selection state for such an electric vehicle transmission unit.
By the rotation disable state of the planetary gear in engagement normally closed type low speed stage selection frictional element to be engaged at normal, characterized in that configured to realize the low-speed stage selection state.

According to the transmission unit for an electric vehicle of the present invention, since the planetary gear does not rotate when the low speed stage is selected, it is not necessary to lubricate the rotation support portion of the planetary gear.
Therefore, even when the low speed stage is selected, the rotational speed of the oil pump is low, and even if the amount of oil discharged from this is small, the rotation support portion of the planetary gear will not be poorly lubricated.
It is possible to avoid the above-described problem that the durability of the planetary gear rotation support portion is deteriorated and the durability of the transmission unit for an electric vehicle is deteriorated.

1 is a schematic plan view of a wheel drive system provided with a transmission unit for an electric vehicle according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part showing a connection procedure of a transmission unit oil pump to the wheel drive system of FIG. FIG. 2 is a schematic diagram showing a configuration of an electric vehicle transmission unit in FIG. FIG. 4 is a collinear diagram showing a rotational speed ratio between components of the electric vehicle transmission unit in FIG.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
<Configuration of Example>
FIG. 1 is a schematic plan view of a wheel drive system including an electric vehicle transmission unit according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of the main part showing the coupling point of the oil pump for the transmission unit to the wheel drive system,
FIG. 3 is a schematic diagram illustrating a configuration example of the electric vehicle transmission unit in FIG.

First, the wheel drive system of FIG. 1 will be described. In the figure, 1L and 1R respectively indicate left and right drive wheels of an electric vehicle, and 2 indicates an electric type for driving the vehicle by driving the left and right drive wheels 1L and 1R. A traveling drive motor is shown.
The power from the travel drive motor 2 is distributed to the left and right drive wheels 1L and 1R through the speed change unit 3, the final drive gear set 6 including the final drive pinion 4 and the final drive ring gear 5, and the differential gear device 7 in order. It is assumed that the vehicle is driven by driving these left and right drive wheels 1L and 1R.

The shaft 4a that rotates together with the final drive pinion 4 also functions as a pump drive shaft of the oil pump 8.
Therefore, the oil pump 8 is drivingly coupled to the free end of the final drive pinion shaft 4a far from the transmission unit 3.

At the time of this drive coupling, as clearly shown in FIG. 2, the pump drive gear 10 is fitted through the one-way clutch 9 to the free end of the final drive pinion shaft 4a.
The inner peripheral teeth of the input pump element constituting the oil pump 8 are meshed with the outer peripheral teeth of the pump drive gear 10, whereby the oil pump 8 is drivingly coupled to the pump drive gear 10.
Thus, the oil pump 8 is drivingly coupled to the final drive pinion shaft 4a via the one-way clutch 9.

The one-way clutch 9 is arranged in a direction to drive the oil pump 9 when the final drive pinion shaft 4a drives the vehicle forward by forward rotation.
When the final drive pinion shaft 4a causes the vehicle to travel backward by reverse rotation, the one-way clutch 9 is free-running so that the oil pump 9 is not driven.

FIG. 3 illustrates details of the transmission unit 3 in FIG. 1, 11 is an input shaft of the transmission unit 3, and 12 is an output shaft of the transmission unit 3.
The input shaft 11 and the output shaft 12 are arranged in a coaxial butting relationship and are rotatably supported by the transmission unit case 3a (see also FIG. 1).

The transmission unit 3 is of a simple planetary gear set type, has a sun gear 13 at its center,
Concentrically surrounding the sun gear 13, the ring gear 14 is rotatably provided,
A set of three planetary pinion gears (planetary gears) 15 is engaged with the sun gear 13 and the ring gear 14, and the planetary pinion gears 15 are rotatably supported by a common carrier 16.

The planetary gear set type transmission unit 3 causes the carrier 16 to function as an input element and the sun gear 13 to function as an output element.
For this reason, the carrier 16 is bound to the inner end of the input shaft 11 close to the output shaft 12, and the sun gear 13 is bound to the inner end of the output shaft 12 close to the input shaft 11.

The transmission unit 3 is further driven and coupled as appropriate between the carrier 16 and the sun gear 13, and the carrier 16 and the sun gear 13 are rotated together to make the planetary pinion gear 15 unable to rotate. Speed change friction element) 17,
A two-speed brake (speed-change friction element for selecting a high-speed stage) 18 that allows the planetary pinion gear 15 to revolve while rotating along the inner periphery of the ring gear 14 by fixing the ring gear 18 in a non-rotatable state Provide.

The first-speed clutch 17 is a normally-closed variable speed friction element that is normally fastened by elastic means such as a spring, and the second-speed brake 18 is a normal-open type that is normally released by elastic means such as a spring. The variable speed friction element.
Here, when releasing the first speed clutch 17, the clutch 17 is hydraulically operated against an elastic means such as a spring to change the state from the engaged state to the released state.
When the second speed brake 18 is engaged, the brake 18 is hydraulically operated against elastic means such as a spring to change the state from the released state to the engaged state.

The transmission unit 3 of FIG. 3 configured as described above has an input shaft 11 coupled to an output shaft 2a of the travel drive motor 2 as shown in FIG. 1, and the output shaft 12 is connected to a final drive pinion shaft (oil pump drive shaft) 4a. Combined with practical use.
This speed change unit 3 uses the oil discharged from an oil pump 8 driven by a final drive pinion shaft (oil pump drive shaft) 4a as a working medium to actuate the hydraulic pressure of the first speed clutch 17 (change from the engaged state to the released state) ), And the hydraulic operation of the second-speed brake 18 (change of state from the released state to the engaged state) is performed, and the planetary gear set components are lubricated.

<Operation of Example>
The operation of the electric vehicle transmission unit 3 according to the above embodiment will be described below.
When the traveling drive motor 2 is stopped, the oil pump 8 is not driven and the oil discharge amount is zero, so both the first speed clutch 17 and the second speed brake 18 are in an inoperative state. Yes, the first speed clutch 17 is engaged and the second speed brake 18 is released.

At this time, the transmission unit 3 is coupled between the carrier 16 and the sun gear 13 by engaging the first-speed clutch 17, and the carrier 16 and the sun gear 13 are directly connected to each other so as to rotate together with the planetary pinion gear 15 and the ring gear 14 (1 Speed selection state, low speed stage selection state).
However, when the traveling drive motor 2 is stopped, since the input rotational speed to the carrier 16 is 0, the output rotational speed from the sun gear 13 (output shaft 12) is also 0, and the wheels 1L, 1R Is not driven, and can be kept stationary.

If the forward (D) range is selected in the hope of starting the vehicle and the travel drive motor 2 is driven in the forward direction by depressing the accelerator pedal, the forward rotational power from now on becomes the carrier 16, the sun gear 13, the planetary pinion gear 15 and While rotating the ring gear 14 integrally, it is transmitted as it is to the left and right drive wheels 1L and 1R via the final drive gear set 6 and the differential gear device 7, and the vehicle is driven at the first speed (low speed stage) by driving these left and right drive wheels 1L and 1R. You can start.
The alignment chart at this time is as illustrated by a solid line in FIG. 4 because the rotation speeds of the carrier 16, the sun gear 13, the planetary pinion gear 15, and the ring gear 14 are the same.

  Since the oil pump 8 is driven by the final drive pinion shaft 4a while the vehicle is running after starting, the hydraulic operation of the first speed clutch 17 (the state change from the engaged state to the released state) is performed using the discharged oil from now on as the working medium. ), And hydraulic operation of the second-speed brake 18 (change of state from the released state to the engaged state) is possible, and the planetary gear set components can be lubricated.

When the vehicle is running after starting, when the vehicle speed rises or the running load decreases, it becomes possible to select the 2nd speed (high speed stage) with a higher gear ratio than the 1st speed (low speed stage)
Using the oil discharged from the oil pump 8, the first speed clutch 17 is hydraulically operated to change the state from the engaged state to the released state, and at the same time, the second speed brake 18 is hydraulically operated to change the state from the released state to the engaged state.

At this time, since the ring gear 18 is fixed to be non-rotatable by engaging the second speed brake 18, the rotational power from the traveling drive motor 2 to the carrier 16 rolls (revolves) the planetary pinion gear 15 along the inner periphery of the ring gear 14. Rotate while letting.
Due to the revolution and rotation of the planetary pinion gear 15, the sun gear 13 is rotated at a speed increased by a gear ratio determined by the gear ratio between the ring gear 14 and the sun gear 13, and this increased speed rotation is transmitted from the sun gear 13 to the final drive gear set 6 and the differential gear device 7. Is transmitted to the left and right drive wheels 1L and 1R, and the vehicle can be driven at the second speed (high speed stage) by increasing the speed of the left and right drive wheels 1L and 1R.

  The nomogram at this time explains the case where the input rotational speed to the carrier 16 is the same as that when the first speed (low speed stage) is selected as described above. Since the rotational speed of the sun gear 13 is increased by the gear ratio between the ring gear 14 and the sun gear 13, it is as shown by a one-dot chain line in FIG.

  When the vehicle is driven in reverse (R) range and the drive motor 2 is driven in the reverse direction by depressing the accelerator pedal, the transmission unit 3 selects the same first speed (low speed stage) as before the previous start. Therefore, the reverse rotational power from the travel drive motor 2 causes the carrier 16, the sun gear 13, the planetary pinion gear 15 and the ring gear 14 to rotate integrally in the reverse direction while passing through the final drive gear set 6 and the differential gear device 7 as they are. The vehicle is transmitted to the left and right drive wheels 1L and 1R, and the vehicle can be moved backward at the first speed (low speed stage) by the reverse drive of the left and right drive wheels 1L and 1R.

  However, since the final drive pinion shaft 4a is also rotated in the reverse direction during reverse travel, the one-way clutch 9 in FIG. 2 does not run freely and the oil pump 8 is not driven.

<Effect of Example>
By the way, in this embodiment, since the carrier 16, the sun gear 13, the planetary pinion gear 15 and the ring gear 14 are integrally rotated when the first speed (low speed stage) is selected, the planetary pinion gear 15 does not rotate. There is no need to lubricate the rotating bearing.

Therefore, when the first speed (low speed stage) is selected, the rotation speed of the oil pump 8 is low, and even if the oil discharge amount is small, the rotation support portion of the planetary pinion gear 15 will not be poorly lubricated.
It is possible to avoid the problem that the durability of the planetary pinion gear rotation support portion is deteriorated and the durability of the electric vehicle transmission unit 3 is deteriorated.

Further, as shown in FIG. 1, the oil pump 8 is arranged to be driven by a transmission system between the output element (sun gear 13: output shaft 12) of the planetary gear set type transmission unit 3 and the drive wheels 1L, 1R.
As can be seen from the above, the oil pump 8 can be kept at a low speed at the first speed (low speed stage) where the required oil discharge amount from the oil pump 8 is small, and the friction at the unnecessary high speed rotation of the oil pump 8 Increase in energy loss can be prevented.

Furthermore, the oil pump 8 is not directly connected to the drive shaft 4a, but is connected to the drive shaft 4a via the one-way clutch 9 as shown in FIG.
When the vehicle is running backward, the oil pump 8 can be prevented from being driven by the free running of the one-way clutch 9.
It is possible to prevent the oil pump 8 from being operated wastefully and increasing friction and increasing energy loss during reverse travel in which the speed change unit 3 is set to the first speed (low speed stage) selection state for low speed travel.

Further, the normally closed type variable speed friction element in which the first speed clutch 17 for realizing the first speed (low speed stage) with the planetary pinion gear 15 being non-rotatable is normally engaged by an elastic means such as a spring. Because
Coupled with the fact that the 2nd speed brake 18 for realizing the 2nd speed (high speed stage) by fixing the ring gear 14 is a normally open type shifting friction element that is normally released by elastic means such as a spring,
When realizing the first speed (low speed stage), both the speed change friction elements 17 and 18 can be deactivated and the first speed (low speed stage) can be realized, and even if the oil discharge amount of the oil pump 8 is small 1st speed (low speed stage) can be realized.

As in this embodiment, the input element of the planetary gear set type transmission unit 3 is the carrier 16, and the traveling drive motor 2 is coupled to the carrier 16,
The output element of the planetary gear set type transmission unit 3 is the sun gear 13, and the driving wheels 1L and 1R are coupled to this,
The planetary gear set type transmission unit 3 can select the first speed (low speed stage) by drivingly coupling the carrier 16 and the sun gear 13 with the first speed clutch 17, and by fixing the ring gear 14 with the second speed brake 18 If you want to select 2nd speed (high speed stage),
The transmission unit 3 can be constituted by a simple simple planetary gear set, which is very advantageous in terms of cost.

<Other examples>
However, in the present invention, the transmission unit 3 does not necessarily have to be configured with a simple planetary gear set as shown in the example,
Of course, the above idea of the present invention can be applied to any type of transmission unit as long as it is composed of a planetary gear set in which a planetary gear (may be a stepped planetary gear) such as the planetary pinion gear 15 exists. is there.

1L, 1R left and right drive wheels
2 Travel drive motor
3 Electric vehicle transmission unit
4 Final drive pinion
5 Final drive ring gear
6 Final drive gear set
7 Differential gear unit
8 Oil pump
9 One-way clutch
11 Input shaft
12 Output shaft
13 Sun gear (output element)
14 Ring gear
15 Planetary pinion gear (Planetary gear)
16 Carrier (input element)
17 1-speed clutch (speed change friction element for low speed selection)
18 2-speed brake (speed friction element for high speed selection)

Claims (4)

It has a planetary gear and has a planetary gear set that can select a low speed stage and a high speed gear ratio that is higher than the low speed stage, and a travel drive motor is driven as an input element of the planetary gear set and a drive is driven as an output element In the transmission unit for an electric vehicle using the oil from the oil pump that is coupled with the wheels and driven by a transmission system between the travel drive motor and the drive wheels as the working medium,
A speed change unit for an electric vehicle, wherein the low speed stage is selected by making the planetary gear non-rotatable by fastening a normally closed low speed stage selection speed change friction element that is normally engaged. In the electric vehicle transmission unit according to claim 1,
The transmission unit for an electric vehicle, wherein the oil pump is driven by a transmission system between an output element of the planetary gear set and a drive wheel. In the transmission unit for an electric vehicle according to claim 2,
The transmission unit for an electric vehicle, wherein the oil pump is driven by a transmission system between an output element of the planetary gear set and a drive wheel via a one-way clutch. In the electric vehicle transmission unit according to any one of claims 1 to 3 ,
The input element of the planetary gear set is a carrier that rotatably supports the planetary gear, and the traveling drive motor is coupled to the carrier,
An output element of the planetary gear set is a sun gear meshing with the planetary gear, and the driving wheel is coupled to the sun gear;
In addition to the carrier and sun gear, the planetary gear set has a ring gear meshing with the planetary gear, and the carrier and the sun gear are driven and coupled by fastening the normally closed low-speed stage selection speed change friction element. The planetary gear is made incapable of rotating, and the low speed stage can be selected, and by fixing the ring gear, the planetary gear can roll along the inner periphery of the ring gear and the high speed stage can be selected. A transmission unit for an electric vehicle, characterized in that:

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