Driving system

A driving system includes: a left electric motor which drives a left wheel of a vehicle; a first parking gear which is provided on a left power transmission path between the left electric motor and the left wheel; a right electric motor which drives a right wheel of the vehicle; a second parking gear which is provided on a right power transmission path between the right electric motor and the right wheel; and a rotation regulation unit that engages with both of the first parking gear and the second parking gear. The first parking gear and the second parking gear have different tooth tip diameters.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority from Japanese Patent Application No. 2017-030273 filed on Feb. 21, 2017, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to a driving system provided in a vehicle.

BACKGROUND

In the related art, there is known a parking device which regulates rotation of a driving shaft that drives a wheel to maintain a vehicle in a stopped state when a select lever (shift lever) is selectively operated to a parking range (hereinafter, referred to as a P range). For example, JP-A-05-116540 and JP-A-2009-137427 disclose a parking device of an electric car including: gear-like parking gears which are respectively provided in driving shafts of a driving system that can independently drive left and right wheels; and a parking pawl in which a projected portion that engages with a tooth groove of the parking gears is formed. In the parking device, the projected portion of the parking pawl engages with the tooth groove of the parking gear to regulate the rotation of the driving shaft when a select lever is operated to the P range. Hereinafter, a specific configuration of the driving system described in JP-A-2009-137427 will be described with reference toFIGS. 6 and 7.

As illustrated inFIG. 6, a driving system100of JP-A-2009-137427 includes: a left wheel driving system103A including a first electric motor101A which drives a left wheel, and a first transmission102A which is provided on a power transmission path between the first electric motor101A and the left wheel; a right wheel driving system103B including a second electric motor101B which drives a right wheel, and a second transmission102B which is provided on a power transmission path between the second electric motor101B and the right wheel; first and second rotation detectors105A and105B which are installed on rotor shafts104A and104B of each of the electric motors101A and101B and detect a rotation angle of each of the rotor shafts104A and104B; first and second parking devices130A and130B which are installed on each of the rotor shafts104A and104B and regulate rotation of each of the rotor shafts104A and104B during parking; and a substantially cylindrical case106which accommodates these components therein.

As illustrated inFIG. 7, the first and second parking devices130A and130B respectively include a parking gear131, a parking pawl132, and a parking rod133. The parking gear131has a shape of a gear, and is disposed concentrically to each of the rotor shafts104A and104B. A tooth groove131bwhich is formed between a tooth131aand a tooth131aof the parking gear131is configured such that a projected portion132aof the parking pawl132engages therewith.

The parking pawl132has the projected portion132athat engages with the tooth groove131bat a tip end thereof n addition, a rear end of the parking pawl132is rotatably supported by the case106via a pawl shaft134. The pawl shaft134is provided with a torsion spring135so that a spring load acts in a direction in which engaging between the parking gear131and the projected portion132aof the parking pawl132is released. The parking pawl132rotates around the pawl shaft134by the parking rod133when the select lever is selectively operated to the P range.

The parking rod133includes a tip end side rod133a, a rear end side rod133b, a cam137, and a coil spring138. The tip end side rod133aof the parking rod133has a diameter greater than that of the rear end side rod133b. The tip end side rod133ais slidably supported by a bracket136fixed to the case106. Meanwhile, on the rear end side rod133b, the cam137for driving the parking pawl132is disposed. The cam137is slidably provided on the rear end side rod133b, receives a spring load of the coil spring138from the rear part, and abuts against a step133cformed between the tip end side rod133aand the rear end side rod133b. In addition, the rear end side rod133bis connected to the select lever which is not illustrated at the rear end thereof.

In the above-described first and second parking devices130A and130B, when the select lever is selectively operated to the P range, the parking rod133moves toward the case106side inFIG. 5. When the parking rod133moves in this manner, the cam137rides on the bracket136and pushes up the tip end of the parking pawl132from a lower side to an upper side in the drawing. Then, the parking pawl132rotates around the pawl shaft134.

In addition, in a case where the projected portion132aof the parking pawl132abuts against a tooth bottom surface of the tooth groove131bof the parking gear131, the projected portion132aof the parking pawl132engages with the tooth groove131bof the parking gear131, and thus, the rotation of each of the rotor shafts104A and104B is regulated, and the vehicle is maintained in a stopped state.

Meanwhile, in a case where the projected portion132aof the parking pawl132abuts against the tooth tip surface131cof the parking gear131, the cam137makes the rear end side rod133bslide toward a side opposite to the case106inFIG. 5against the spring load of the coil spring138so as to ensure escape against a stroke of the parking rod133. Accordingly, it becomes unnecessary for the projected portion132aof the parking pawl132to forcibly press the tip end surface131c, and this prevents the first and second parking devices130A and130B from failing. In a case where the projected portion132aof the parking pawl132abuts against the tooth tip surface131cin this manner, when the parking gear131slightly rotates and the tooth groove131bof the parking gear131comes to a position of the projected portion132aof the parking pawl132, the projected portion132aand the tooth groove131bengage with each other to regulate the rotation of each of the rotor shafts104A and104B, and the vehicle is maintained in a stopped state.

However, in the driving systems of JP-A-05-116540 and JP-A-2009-137427, since two parking devices (parking pawls) are provided, not only there is a concern that the number of components, the costs, the size and the like increase, but also there is a concern that parking effects cannot be sufficiently obtained since there is a case where it is not possible to regulate the rotation of left and right wheels at the same time during a parking operation when phases of the teeth of parking gears of the first and second parking devices are shifted (hereinafter, simply referred to as phases of the left and right parking gears).

Here, the driving system of JP-A-2009-137427 is provided with a phase synchronization unit for synchronizing the phases of the left and right parking gears, and accordingly, it is possible to regulate the rotation of left and right rear wheels at the same time during the parking operation, however, since the phase synchronization unit of JP-A-2009-137427 makes the phases of the left and right parking gears match each other by using a driving force of the electric motor that drives the wheel, when phase-matching the left and right parking gears, there is a concern that power is generated in the wheels, and thereby deteriorating straight traveling performance of the vehicle. In addition, when the phase matching of the parking gears by the phase synchronization unit of JP-A-2009-137427 is executed in a travel stopped state, there is a concern that the vehicle moves, and thus, there is a restriction that the phase matching cannot be executed unless the vehicle is in the middle of traveling.

Meanwhile, in the parking device described in JP-A-05-116540, since teeth of one parking gear of a pair of parking gears are missing in every other tooth, during a selecting operation to the P range, even in a case where the phases of each of the parking gears are shifted, it is possible to engage the parking gear and the projected portion of the parking pawl with each other, however, when the teeth of one parking gear of the pair of parking gears are missing in every other tooth, the tooth groove of the parking gear widens in a gear circumferential direction, and thus, even in a state where the projected portion of the parking pawl engages with the tooth groove of the parking gear, backlash is generated in a rotational direction of the parking gear. Therefore, there is a concern that one wheel rotates during parking only by an amount that corresponds to the tooth groove widened due to teeth missing, and the vehicle moves.

SUMMARY

The present invention is to provide a driving system which is capable of regulating rotation of two parking gears by one rotation regulation unit, and is capable of reducing a moving distance of a vehicle after an operation of the rotation regulation unit.

The invention provides following Aspects (1) to (6).(1). A driving system (e.g., a driving system1in an embodiment) including:a left electric motor (e.g., a first electric motor2A in an embodiment) which drives a left wheel e.g., a left wheel LW in an embodiment) of a vehicle;a first parking gear (e.g., a first parking gear51in an embodiment) which is provided on a left power transmission path between the left electric motor and the left wheel;a right electric motor (e.g., a second electric motor2B in an embodiment) which drives a right wheel of the vehicle;a second parking gear (e.g., a second parking gear52in an embodiment) which is provided on a right power transmission path between the right electric motor and the right wheel; anda rotation regulation unit (e.g., a parking pawl53in an embodiment) that engages with both of the first parking gear and the second parking gear,wherein the first parking gear and the second parking gear have different tooth tip diameters (e.g., tooth tip diameters R1and R2in an embodiment).(2). The driving system according to (1),wherein the first parking gear and the second parking gear have a same pitch (e.g., pitches P1and P2in an embodiment).(3). The driving system according to (1) or (2),wherein the first parking gear and the second parking gear have a same tooth bottom diameter (e.g., tooth bottom diameters r1and r2in an embodiment).(4). The driving system according to any one of (1) to (3),wherein the first parking gear and the second parking gear are disposed to be adjacent to each other.(5). The driving system according to any one of (1) to (4),wherein the first parking gear is provided in an output shaft (e.g., an output shaft21A in an embodiment) of the left electric motor, andthe second parking gear is provided in an output shaft (e.g., an output shaft21B in an embodiment) of the right electric motor.(6). The driving system according to any one of (1) to (4),wherein the first parking gear is provided in an axle (e.g., a left axle6A in an embodiment) of the left wheel, andthe second parking gear is provided in an axle (e.g., a right axle6B in an embodiment) of the right wheel.

According to (1), since the rotation of the two parking gears is regulated by one rotation regulation unit, the number of components and the costs can be reduced and the size thereof can be reduced. In addition, since the first parking gear and the second parking gear have different tooth tip diameters, even in a case where the phases are shifted, the two parking gears gradually engage with one rotation regulation unit, and thus, it is possible to reduce the moving distance of the vehicle after the operation of the rotation regulation unit. In other words, compared to a case where the teeth of one parking gear of the pair of parking gears are missing in every other tooth as described in the related art, it is possible to reduce the moving distance of the vehicle until the second parking gear engages with the rotation regulation unit after the first parking gear engages therewith.

According to (2), since the first parking gear and the second parking gear have the same pitch, it is possible to reduce backlash generated between the first parking gear and the second parking gear, and the rotation regulation unit.

According to (3), since the first parking gear and the second parking gear have the same tooth bottom diameter, it is possible to reduce backlash generated between the first parking gear and the second parking gear, and the rotation regulation unit.

According to (4), since the first parking gear and the second parking gear are disposed to be adjacent to each other, the width of the rotation regulation unit can be reduced.

According to (5), since the first parking gear is provided in the output shaft of the left electric motor and the second parking gear is provided in the output shaft of the right electric motor, a force for maintaining the vehicle in a stopped state may be small, and it is possible to further reduce the size of a parking mechanism.

According to (6), since the first parking gear is provided in the axle of the left wheel and the second parking gear is provided in the axle of the right wheel, the rotation of a first parking gear and a second parking gear is regulated at a position closer to the left wheel and the right wheel, it is possible to maintain the stopped state so as not to further cause unnecessary movement of the vehicle.

DETAILED DESCRIPTION

Hereinafter, one embodiment of a driving system of the present r will be described with reference to the attached drawings. In addition, the drawings are to be seen in the sign direction.

As illustrated inFIG. 1, a driving system1includes: a left wheel driving system4A including a first electric motor2A which drives a left wheel LW of a vehicle, and a first transmission3A which is provided on a power transmission path between the first electric motor2A and the left wheel LW; a right wheel driving system4B including a second electric motor2B which drives a right wheel RW of the vehicle, and a second transmission3B which is provided on the power transmission path between the second electric motor2B and the right wheel RW; and a parking mechanism5which regulates rotation of the left wheel LW and the right wheel RW during parking.

The first electric motor2A is disposed coaxially to a left axle6A, and includes an output shaft21A that outputs a driving force of the left wheel LW. The output shaft21A includes an outer protrusion portion21athat protrudes from the first electric motor2A toward the left wheel LW and an inner protrusion portion21bthat protrudes from the first electric motor2A toward the right wheel RW, and the first transmission3A is connected to the outer protrusion portion21a.

The second electric motor2B is disposed coaxially to a right axle6B, and includes an output shaft21B that outputs the driving force of the right wheel RW. The output shaft21B includes the outer protrusion portion21athat protrudes from the second electric motor2B toward the right wheel RW and the inner protruding portion21bthat protrudes from the second electric motor2B toward the left wheel LW, and the second transmission3B is connected to the outer protrusion portion21a.

The first transmission3A includes a first gear31A provided in the output shaft21A (outer protrusion portion21a) of the first electric motor2A, a second gear32A provided in the left axle6A, a plurality of pinion gear33A which engage with the first gear31A and the second gear32A. The pinion gear33A includes a large-diameter gear33awhich engages with the first gear31A, a small-diameter gear33bwhich engages with the second gear32A, and a pinion shaft33cwhich supports the large-diameter gear33aand the small-diameter gear33bintegrally rotatably. Accordingly, after deceleration by the first gear31A, the pinion gear33A (the large-diameter gear33aand the small-diameter gear33b), and the second gear32A of the first transmission3A, the driving force output from the output shaft21A of the first electric motor2A is transmitted to the left wheel LW via the left axle6A.

The second transmission3B includes a first gear31B provided in the output shaft21B (outer protrusion portion21a) of the second electric motor29, a second gear32B provided in the right axle69, and a plurality of pinion gears33B which engage with the first gear31B and the second gear32B. The pinion gear33B includes a large-diameter gear33awhich engages the first gear31B, a small-diameter gear33bwhich engages with the second gear32B, and a pinion shaft33cwhich supports the large-diameter gear33aand the small-diameter gear33bintegrally rotatably. Accordingly, after deceleration by the first gear31B, the pinion gear33B (the large-diameter gear33aand the small-diameter gear33b), and the second gear32B of the second transmission3B, the driving force output from the output shaft21B of the second electric motor2B is transmitted to the right wheel RW via the right axle6B.

The parking mechanism5has a configuration which includes a first parking gear51which is provided on a power transmission path of the left wheel driving system4A, a second parking gear52which is provided on a power transmission path of the right wheel driving system4B, a parking pawl53which engages with the first parking gear51and the second parking gear52, and regulates the rotation of the left wheel LW and the right wheel RW as a projected portion53aof the parking pawl53engages with tooth grooves51aand52aof the first parking gear51and the second parking gear52when a select lever (not illustrated) is operated to the P range. Since the configuration for operating the parking pawl53is similar to that of the parking devices130A and130B of the related art which are illustrated inFIGS. 6 and 7, the description thereof will be omitted.

The first parking gear51and the second parking gear52are coaxially disposed to be adjacent to each other, and the parking pawl53engages with both the first parking gear51and the second parking gear52. More specifically, the first parking gear51and the second parking gear52respectively have a predetermined gear width W1, and are disposed to be adjacent to each other in a vehicle width direction via a gap W2which is smaller than the gear width W1. The parking pawl53has a width W3obtained by adding the gap W2to the gear width W1+W1of the first parking gear51and the second parking gear52, and can engage with both of the first parking gear51and the second parking gear52.

According to the parking mechanism5, since the rotation of the two parking gears51and52is regulated by one parking pawl53, it is possible to reduce the number of components and the costs, and to reduce the size. In addition, since the first parking gear51and the second parking gear52are disposed to be adjacent to each other, the width W3of the parking pawl53can also be reduced.

The first parking gear51is provided in the output shaft21A of the first electric motor2A, and the second parking gear52is provided in the output shaft21B of the second electric motor2B. More specifically, the first parking gear51is provided in a tip end portion of the inner protrusion portion21bwhich protrudes from the first electric motor2A toward the right wheel RW (the second electric motor2B) side in the output shaft21A of the first electric motor2A, and the second parking gear52is provided in a tip end portion of the inner protrusion portion21bwhich protrudes from the second electric motor2B toward the left wheel LW (first electric motor24) side in the output shaft21B of the second electric motor2B.

According to the parking mechanism5, by regulating the rotation of the first parking gear51and the second parking gear52on the upstream side of the first transmission3A and the second transmission3B, a force for maintaining the vehicle in a stopped state may be small, and it is possible to further reduce the size of the parking mechanism5.

Here, in the first parking gear51and the second parking gear52, pitches P1and P2and tooth bottom diameters r1and r2of the teeth51band52bare the same as each other, and the tooth tip diameters R1and R2(R1<R2in the embodiment) are different from each other. In addition, the pitches P1and P2are intervals (the widths of the tooth groove51aand the tooth groove52a) between the tooth51band the tooth51band between the tooth52band the tooth52bin the circumferential direction, the tooth bottom diameters r1and r2are distances from the shaft center to the bottom portion of the tooth grooves51aand52a, and the tooth tip diameters R1and R2are distances from the shaft center to the tooth tip surfaces51cand52c. Accordingly, even in a case where the phases of the first parking gear51and the second parking gear52are shifted, as the first parking gear51and the second parking gear52gradually engage with one parking pawl53, not only the rotation of the left wheel LW and the right wheel RW can be regulated, but also backlash after the engagement with the parking pawl53can be reduced and the moving distance of the vehicle after the parking operation can be reduced. Hereinafter, the operation of the parking mechanism5will be described with reference toFIGS. 2A and 2B.

[Operation of Parking Mechanism]

The first parking gear51and the second parking gear52are in a state where the phases of the teeth51band52bare shifted (refer to (a) ofFIG. 2) and in a state where the phases of the teeth51band52bmatch each other (refer to (b) ofFIG. 2).

As illustrated in (a) ofFIG. 2, when the select lever is operated to the P range in a state where the phases of the teeth51band52bof the first parking gear51and the second parking gear52are shifted, the projected portion53aof the parked pawl53does not engage with the tooth grooves51aand52aof the first parking gear51and the second parking gear52at the same time, and abuts against the tooth tip surfaces51cand52cof the first parking gear51or the second parking gear52.

(a) ofFIG. 2illustrates a state where the projected portion53aof the parking pawl53abuts against the tooth tip surface51cof the first parking gear51and engages with the tooth groove52aof the second parking gear52, and in this state, as the rotation of the second parking gear52is regulated by the parking pawl53, the rotation of the right wheel RW is regulated.

In addition, in a case where the projected portion53aof the parking pawl53abuts against the tooth tip surface52cof the second parking gear52, the projected portion53aof the parking pawl53does not engage with the tooth grooves51aand52aof any of the first parking gear51and the second parking gear and thus, the rotation of the first parking gear51and the second parking gear52is allowed. However, when the vehicle slightly moves, the state illustrated in (a) ofFIG. 2, that is, the state is made where the projected portion53aof the parking pawl53abuts against to the tooth tip surface51cof the first parking gear51and engages with the tooth groove52aof the second parking gear52.

In addition, in the state illustrated in (a) ofFIG. 2, since the projected portion53aof the parking pawl53engages only with the tooth groove52aof the second parking gear52, the rotation of the first parking gear51is allowed, but when the left wheel LW slightly moves, the first parking gear51rotates, and the projected portion53aof the parking pawl53also engages with the tooth groove51aof the first parking gear51at a timing when the teeth51band52bof the first parking gear51and the second parking gear52are phase-matched (refer to (b) ofFIG. 2). In addition, in a state where the projected portion53aof the parking pawl53engages with the tooth grooves51aand52aof the first parking gear51and the second parking gear52, it is possible to regulate the rotation of the first parking gear51and the second parking gear52in a state where backlash barely exists, and to maintain the vehicle in a stopped state.

As described above, according to the embodiment, since the rotation of the two parking gears51and52is regulated by one parking pawl53, it is possible to reduce the number of components and the costs, and to reduce the size. In addition, since the first parking gear51and the second parking gear52have different tooth tip diameters R1and R2, even in a case where the phases are shifted, by gradually engaging with one parking pawl53, the moving distance of the vehicle can be reduced after the operation of the parking pawl53. In other words, compared to a case where the teeth of one parking gear of one pair of parking gears are missing in every other tooth as illustrated in the related art, after the first parking gear engages, it is possible to reduce the moving distance of the vehicle until the second parking gear engages.

Also, since the first parking gear51and the second parking gear52have the same pitches P1and P2and the same tooth bottom diameters r1and r2, it is possible to reduce backlash generated between the first parking gear51and the second parking gear52, and the parking pawl53.

In addition, since the first parking gear51and the second parking gear52are disposed to be adjacent to each other, the width W3of the parking pawl53can be reduced.

In addition, since the first parking gear51is provided in the output shaft21A of the first electric motor2A and the second parking gear52is provided in the output shaft21B of the second electric motor2B, the force for maintaining the vehicle in a stopped state may be small, and it is possible to further reduce the size of a parking mechanism5.

[Modified Examples of Parking Mechanism]

Next, modification examples of the parking mechanism5according to the embodiment of the present invention will be described with reference toFIGS. 3 and 4. However, the configurations common to the above-described embodiment will be given the same reference numerals as those of the above-described embodiment, and thus, the description of the above-described embodiment will be employed.

First Modification Example

As illustrated inFIGS. 3A and 3B, the parking mechanism5according to the first modification example is different from that of the above-described embodiment in that the pitches P1and P2of the first parking gear51and the second parking gear52are different from each other. For example,FIG. 3Aillustrates a case where the pitch P2of the second parking gear52is greater than the pitch P1of the first parking gear51, andFIG. 3Billustrates a case where the pitch P1of the first parking gear51is greater than the pitch P2of the second parking gear52.

Second Modification Example

As illustrated inFIGS. 4A and 4B, the parking mechanism5according to the second modification example is different from that of the above-described embodiment in that the tooth bottom diameters r1and r2of the first parking gear51and the second parking gear52are different from each other. For example,FIG. 4Aillustrates a case where the tooth bottom diameter r1of the first parking gear51is greater than the tooth bottom diameter r2of the second parking gear52, andFIG. 4Billustrates a case where the tooth bottom diameter r1of the first parking gear51is greater than the tooth bottom diameter r2of the second parking gear52.

In addition, not being limited to the above-described embodiment, deformations, improvements and the like of the present invention can be appropriately employed.

For example, in the above-described embodiment, since the first parking gear51and the second parking gear52are disposed further on the upstream side than the first transmission3A and the second transmission3B with respect to the left wheel LW and the right wheel RW, the force of the parking mechanism5for maintaining the vehicle in a stopped state may be small, and it is possible to further reduce the size of the parking mechanism5, however, the first parking gear51and the second parking gear52may be disposed further on the downstream side (for example, the left axle6A and the right axle6B) than the first transmission3A and the second transmission3B. In this case, since the first parking gear51and the second parking gear52are installed at positions closer to the left wheel LW and the right wheel RW, it is possible to maintain the stopped state so as not to further cause unnecessary movement of the vehicle, in addition, in a case where the first parking gear51and the second parking gear52are disposed in the first transmission3A and in the second transmission3B, both merits can be received.

In addition, in the above-described embodiment, the driving force of the first electric motor2A and the second electric motor2B is transmitted to the left wheel LW and the right wheel RW via the first transmission3A and the second transmission3B, but as illustrated inFIG. 5, the present invention can also be realized in the driving system which transmits the driving force of the first electric motor2A and the second electric motor2B to the left wheel LW and the right wheel RW not through the first transmission3A and the second transmission3B.

As illustrated inFIG. 8, the present invention can also be realized in the driving system which provides the first parking gear51in the left axle6A of the left wheel LW, and provides the second parking gear52in the right axle6B of the right wheel RW.