Drive device

Abstract

To provide a drive device which enables simplification of control for performing packing lock while inhibiting unintentional behavioral change of a vehicle.SOLUTION: A drive device includes: a left side power transmission part Tl which transmits torque of a left motor; and a right side power transmission part Tr which transmits torque of a right motor. The left side power transmission part Tl includes: a parking gear 16; and a movable member 5 which frictionally contacts with the right side power transmission part Tr. The drive device includes a parking pole 17 configured to engage with the parking gear 16; and a pressing mechanism 12 which presses the movable member 5 toward the right side power transmission part Tr in conjunction with movement of the parking pole 17 in a lock direction in which the parking pole 17 is engaged with the parking gear 16.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a drive unit configured to drive left and right drive wheels by independent drive force sources. [Background technology]

[0002] Patent Documents 1 and 2 describe control devices for a vehicle equipped with a motor for each of the left and right drive wheels and a parking mechanism. These control devices are configured to suppress unintended behaviors such as the vehicle turning due to differences in the timing of locking and unlocking the parking mechanism.

[0003] Specifically, the control device described in Patent Document 1 is configured to calculate the switching time required to complete switching of the parking mechanisms from a locked state to a released state based on the load acting on each parking mechanism, and to start releasing the parking mechanism with the shorter switching time later than the parking mechanism with the longer switching time, to match the timing of completing switching of each parking mechanism from a locked state to a released state, or to reduce the switching speed of the parking mechanism with the shorter switching time, or to increase the load acting on the parking mechanism with the shorter switching time and reduce the load acting on the parking mechanism with the longer switching time.

[0004] Furthermore, the control device described in Patent Document 2 is configured such that, during parking lock, if one parking mechanism is locked and the other cannot be locked, the left and right drive wheels are fixed substantially simultaneously by applying a braking force to each drive wheel by the hydraulic brake mechanism until the other parking mechanism is locked. Similarly, when releasing the parking lock, if one parking mechanism is released and the other parking mechanism is locked, the left and right drive wheels are released substantially simultaneously by applying a braking force to each drive wheel by the hydraulic brake mechanism until the other parking mechanism is released.

[0005] Patent Document 3 describes a so-called inboard type electric vehicle in which a motor and a power transmission mechanism for driving the right drive wheel and a motor and a power transmission mechanism for driving the left drive wheel are mounted on a chassis, and this electric vehicle is equipped with an engagement device that selectively couples the left and right power transmission shafts together so that even if one of the motors fails, the other motor can transmit torque to the left and right drive wheels. Each power transmission shaft is provided with a parking mechanism. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-051443 A [Patent Document 2] JP 2006-044458 A [Patent Document 3] Japanese Patent Application Publication No. 05-116541 Summary of the Invention [Problem to be solved by the invention]

[0007] In the vehicles described in Patent Documents 1 and 2, the left and right drive wheels are always independently driven, so the timing at which the parking mechanisms are activated is made different or a hydraulic brake mechanism is used in combination to synchronize the timing at which the parking mechanisms are locked or unlocked. Therefore, the control devices described in Patent Documents 1 and 2 require control to synchronize the operation of the parking mechanisms and control to synchronize the hydraulic brakes in addition to the parking mechanisms, which can make the control complicated.

[0008] The present invention has been made in light of the above technical problems, and has an object to provide a drive device that can simplify control for parking lock while suppressing unintended changes in vehicle behavior. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a drive device comprising a left motor, a left side power transmission section that transmits the torque of the left side motor, a left side drive shaft connected to the left side power transmission section, a right side motor, a right side power transmission section that transmits the torque of the right side motor, and a right side drive shaft connected to the right side power transmission section, wherein one of the left side power transmission section and the right side power transmission section is provided with a parking gear and a movable member that frictionally contacts the other power transmission section of the left side power transmission section and the right side power transmission section, a parking pole that meshes with the parking gear, and a pressing mechanism that presses the movable member toward the other power transmission section as the parking pole moves in a locking direction to mesh with the parking gear. Effect of the Invention

[0010] In the drive device of the present invention, one of the left power transmission part connected to the left drive shaft and the right power transmission part connected to the right drive shaft is provided with a parking gear and a movable member that is in frictional contact with the other power transmission part, and is equipped with a pressing mechanism that presses the movable member toward the other power transmission part as the parking gear moves in the locking direction to engage the parking pole. Therefore, the parking lock is performed with the two power transmission parts in frictional contact by the movable member, so that it is possible to suppress the occurrence of a difference in timing when the locking of the left and right drive shafts is completed. In other words, it is possible to suppress the occurrence of unintended behavior such as the vehicle turning when the parking lock is performed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a drive device according to an embodiment of the present invention. [Diagram 2]4A is a cross-sectional view showing a schematic configuration of each power transmission unit, and FIG. 4B is a view showing the configuration as viewed from an arrow B in FIG. [Diagram 3] 1A and 1B are diagrams showing the operation of the clutch mechanism, where (a) is a diagram showing a state in which the clutch mechanism is released, (b) is a diagram showing a state in which the clutch mechanism is engaged and the parking mechanism is released, and (c) is a diagram showing a state in which the clutch mechanism is engaged and the parking mechanism is locked. [Figure 4] 4 is a flowchart illustrating a control method for performing parking lock. [Diagram 5] 4 is a flowchart illustrating a control method for releasing the parking lock. [Figure 6] 10 is a flowchart illustrating a method for controlling the actuator when one of the motors fails. [Figure 7] 5 is a flowchart illustrating a method for controlling an actuator when traveling on a rough road. [Figure 8] 10 is a flowchart illustrating a method for controlling an actuator in consideration of the energy efficiency of a motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of the implementation of the present invention, and is not intended to limit the present invention.

[0013] FIG. 1 shows a schematic diagram of an example of a drive device according to an embodiment of the present invention. The drive device 1 shown in FIG. 1 is a so-called inboard type drive device supported on a vehicle body, and two motors Mr, Ml as drive power sources are provided to rotate around a central axis of rotation along the vehicle width direction. These motors Mr, Ml can be configured in the same manner as motors provided as drive power sources for conventional electric vehicles and hybrid vehicles, and can be configured as motor generators that function as a motor that generates drive torque when power is supplied from an electric storage device (not shown), and also function as a generator that converts the power into electric power when an output shaft (rotor shaft) is rotated. Specifically, each of the motors Mr, Ml can be configured as a permanent magnet synchronous motor or an induction motor. Note that the motors Mr, Ml are not mechanically connected to each other when a clutch mechanism C described later is released, and are configured so that the rotation speed and torque of one of the motors Mr (Ml) and the rotation speed and torque of the other motor Ml (Mr) can be controlled separately.

[0014] The right motor Mr is connected to a right drive shaft Sr via a right power transmission unit Tr, and the left motor Ml is connected to a left drive shaft Sl via a left power transmission unit Tl. These power transmission units Tr, Tl can be configured, for example, by a reduction mechanism made up of a small diameter gear attached to the output shaft of the motor Mr, Ml and a large diameter gear meshing with the small diameter gear.

[0015] The power transmission units Tr and Tl are configured to be selectively connected to each other. A diagram for explaining this configuration is shown in Fig. 2. In the example shown in Fig. 2, the left power transmission unit Tl has a left output gear 1l, and a left cylindrical shaft 2l is integrally connected to the left output gear 1l. Similarly, the right power transmission unit Tr has a right output gear 1r, and a right cylindrical shaft 2r is integrally connected to the right output gear 1r. The left cylindrical shaft 2l and the right cylindrical shaft 2r are rotatably held in a case (not shown) via needle bearings 3.

[0016] The left drive shaft Sl is fitted to the left cylindrical shaft 2l from the left side in the vehicle width direction by spline engagement or the like, and the right drive shaft Sr is fitted to the right cylindrical shaft 2r from the right side in the vehicle width direction by spline engagement or the like.

[0017] In addition, the portion of the left cylindrical shaft 2l extending toward the center in the vehicle width direction is provided with, in order from the left output gear 1l side, a first region A1 having a relatively large outer diameter, a second region A2 whose outer diameter gradually decreases, and a third region A3 having a relatively small outer diameter.

[0018] The second region A2 is formed such that the length in the axial direction of the left cylindrical shaft 2l is shorter than the radius of the rolling elements 4 described later. The outer peripheral surface of the left cylindrical shaft 2l in the second region A2 is formed into a concave arc surface having the same radius of curvature as the radius of curvature of the rolling elements 4.

[0019] The third region A3 has its tip inserted into the right cylindrical shaft 2r so as to be rotatable relative to the right cylindrical shaft 2r. An annular movable member 5 is fitted to the portion of the right cylindrical shaft 2r that moves on the left cylindrical shaft 2l and is rotatable integrally with the left cylindrical shaft 2l. The side surface of the movable member 5 on the second region A2 side faces the concave arc surface formed on the left cylindrical shaft 2l and is formed as a concave arc surface with the same radius of curvature. That is, the concave arc surface formed on the left cylindrical shaft 2l and the concave arc surface of the movable member 5 form an annular groove 6 having a semicircular cross section.

[0020] Furthermore, a spring 7 for pressing the movable member 5 towards the second region A2 is fitted into the third region A3. An annular stopper 8 that abuts against one end of the spring 7 and receives the load acting on the spring 7 is engaged with the tip of the third region A3. A step 9 for limiting the amount of movement of the movable member 5 towards the second region A2 is formed on the left cylindrical shaft 2l, and the width of the annular groove 6 when the movable member 5 moves until it abuts against the step 9 (the width on the outermost diameter side of the left cylindrical shaft 2l) is formed to be smaller than the diameter of the rolling element 4.

[0021] An annular first friction material 10 is integrated with the surface of the movable member 5 facing the right cylindrical shaft 2r, and an annular second friction material 11 is integrated with the surface of the right cylindrical shaft 2r facing the movable member 5 so as to be in frictional contact with the first friction material 10. That is, by pressing the movable member 5 toward the right cylindrical shaft 2r, in other words, by widening the groove width of the annular groove 6, the first friction material 10 and the second friction material 11 come into contact with each other, and a torque according to the contact pressure is transmitted between the left power transmission unit Tl and the right power split unit Tr.

[0022] A pressing mechanism 12 for expanding the groove width of the annular groove 6 is provided outside the second area A2 and the third area A3, more specifically, below in the vertical direction. As shown in FIG. 2(b), the pressing mechanism 12 includes three rolling elements 4, a support member 14 having an arc portion 13 for rotatably holding the three rolling elements 4, and an actuator 15 for pressing the support member 14 in the normal direction of the left cylindrical shaft 2l to move it forward. Therefore, when the actuator 15 presses the support member 14 toward the left cylindrical shaft 2l, the rolling elements 4 fit into the annular groove 6. Since the width of the annular groove 6 is formed smaller than the diameter of the rolling elements 4 as described above, the movable member 5 is expanded toward the right cylindrical shaft 2r according to the amount of the rolling elements 4 that fit into the annular groove 6. Therefore, the frictional contact between the friction materials 10 and 11 transmits torque between the left power transmission unit Tl and the right power transmission unit Tr. That is, the pressing mechanism 12, the movable member 5, and the right cylindrical shaft 2r function as a clutch mechanism C.

[0023] As shown in FIG. 2, a parking gear 16 is formed in the first region A1 of the left cylindrical shaft 2l. A parking pole 17 that meshes with the parking gear 16 is provided in the pressing mechanism 12. The parking pole 17 shown in FIG. 2 is formed in a U-shape in a side view by an engagement portion 18 that is inserted between the teeth of the parking gear 16, a stopper portion 19 that is formed parallel to the engagement portion 18, and a support portion 20 that connects the engagement portion 18 and the stopper portion 19. The stopper portion 19 is rotatably supported by a support shaft 21 that is formed protruding from the support member 14. In order to limit the amount of rotation of the parking pole 17, an arc-shaped stopper shaft 22 that abuts against the stopper portion 19 is formed between the engagement portion 18 and the stopper portion 19 protruding from the arc portion 13, and a spring 23 that presses the engagement portion 18 is provided between the stopper shaft 22 and the engagement portion 18.

[0024] Therefore, by pressing the support member 14 toward the left cylindrical shaft 2l by the actuator 15, the parking pole 17 is inserted into and engaged with the parking gear 16. When the parking pole 17 is engaged with the parking gear 16 in this manner, if the tooth tip of the parking gear 16 comes into contact with the engaging portion 18, the spring 23 is compressed, and when the contact is released, the spring 23 inserts the engaging portion 18 into the parking gear 16.

[0025] FIG. 3 is a diagram for explaining the relationship between the timing of engagement of the clutch mechanism C and the timing of parking lock when the parking pole 17 meshes with the parking gear 16. FIG. 3(a) shows a state in which the clutch mechanism C and the parking lock are released. That is, the rolling element 4 and the parking pole 17 are separated from the left cylindrical shaft 2l. Therefore, the movable member 5 is pressed toward the left output gear 1l by the spring 7, and the friction materials 10, 11 are not in contact with each other. Also, since the rotation of the parking gear 16 is not restricted, the left cylindrical shaft 2l is rotatable. Therefore, in the state shown in FIG. 3(a), only the output torque of the left motor Ml is transmitted to the left drive shaft Sl, and only the output torque of the right motor Mr is transmitted to the right drive shaft Sr. That is, the left drive shaft Sl and the right drive shaft Sr are controlled independently.

[0026] As shown in FIG. 3(b), when the actuator 15 advances the support member 14 by a first predetermined amount L1, the rolling element 4 starts to engage with the annular groove 6. As described above, the maximum width of the annular groove 6 when pressed by the spring 7 is narrower than the diameter of the rolling element 4. Therefore, as the amount of engagement of the rolling element 4 with the annular groove 6 increases, the movable member 5 is pressed toward the right cylindrical shaft 2r. As a result, the frictional materials 10 and 11 come into contact with each other, and the left power transmission unit Tl and the right power transmission unit Tr are connected so as to be able to transmit torque. Since the frictional force generated between the frictional materials 10 and 11 changes depending on the amount of engagement of the rolling element 4, the torque capacity transmitted between the left power transmission unit Tl and the right power transmission unit Tr can be controlled by controlling the actuator 15.

[0027] Furthermore, even when the left side power transmission unit Tl and the right side power transmission unit Tr are connected so as to be able to transmit torque as shown in FIG. 3(b), if the amount of movement of the support member 14 is less than the second predetermined amount L2, the parking pole 17 is configured not to mesh with the parking gear 16.

[0028] Therefore, in the state shown in FIG. 3(b), various driving modes can be adopted, such as outputting torque from only one of the motors Ml (Mr) and transmitting that torque to the left and right drive shafts Sl, Sr to drive, or making the output torques of the left and right motors Ml, Mr different and transmitting the same torque to the left and right drive shafts Sl, Sr to drive.

[0029] As shown in Fig. 3(c), when the support member 14 is further advanced by the actuator 15, the frictional force between the friction materials 10, 11 becomes maximum and the parking pole 17 meshes with the parking gear 16. That is, the clutch mechanism C is fully engaged and the parking lock is established. Therefore, the left and right drive shafts Sl, Sr stop. That is, the forward direction of the support member 14 becomes the locking direction in which the parking pole 17 meshes with the parking gear 16.

[0030] Next, a method for controlling the actuator 15 will be described. Fig. 4 shows a flowchart for explaining the control method for parking lock, and determines whether or not the parking range (P range) has been selected by a shift device such as a shift lever (not shown) (step S1).

[0031] If the P range is not selected and therefore the answer is negative in step S1, the routine is terminated. On the other hand, if the P range is selected and therefore the answer is positive in step S1, the actuator 15 advances the support member 14 so that the rolling element 4 engages with the annular groove 6 (step S2). The target movement amount of the support member 14 at this time is set to be equal to or greater than a second predetermined amount L2 in order to achieve parking lock, as shown in FIG. 3(c).

[0032] By advancing the support member 14 in step S2, the movable member 5 is pressed and the annular groove 6 is expanded, so that the friction materials 10, 11 come into frictional contact with each other. That is, the clutch mechanism C is engaged (step S3). Then, the parking pole 17 meshes with the parking gear 16. That is, the parking lock is established (step S4).

[0033] 1, the clutch mechanism C is engaged to engage the left and right drive shafts Sl, Sr so that they can rotate together, and then the parking gear 16 provided on one of the cylindrical shafts (the left cylindrical shaft 2l) is engaged with the parking pole 17 to perform parking lock, so that it is possible to prevent a difference in timing when the locking of the left and right drive shafts Sl, Sr is completed. In other words, it is possible to prevent the vehicle from performing unintended behavior such as turning its head during parking lock.

[0034] FIG. 5 shows a flowchart explaining a control method for releasing the parking lock. In this method, it is determined whether or not a range other than the parking range (P range) has been selected by a shift device such as a shift lever (not shown), i.e., whether or not the P range has been released (step S11).

[0035] If the P range is not released and therefore the answer is negative in step S11, the routine is terminated. On the other hand, if the P range is released and therefore the answer is positive in step S11, the actuator 15 moves the support member 14 backward (step S12).

[0036] By moving the support member 14 backward in step S12, first, the parking gear 16 and the parking pole 17 are disengaged from each other. That is, the parking lock is released (step S13). Next, the rolling element 4 is released from the annular groove 6, and the movable member 5 is pressed by the spring 7, and the friction materials 10, 11 are released. That is, the clutch mechanism C transitions to a released state (step S14).

[0037] In the example shown here, the clutch mechanism C is released after the parking lock is released, but in cases where the vehicle travels straight when starting, the clutch mechanism C does not need to be released. In other words, the amount of movement of the support member 14 may be equal to or greater than the first predetermined amount L1 and less than the second predetermined amount L2.

[0038] 1, the parking lock is released while the left and right power transmission units Tl and Tr are connected, so that the timing at which the left and right drive shafts Sl and Sr are released can be prevented from differing. In other words, it is possible to prevent the vehicle from turning around or other unintended behavior when the parking lock is released.

[0039] Fig. 6 shows a flowchart for explaining a method for controlling the actuator 15 when one of the motors fails. In the example shown in Fig. 6, first, it is determined whether or not one of the left motor Ml and the right motor Mr (Mr) has failed (step S21). This step S21 can be determined based on signals from sensors provided in inverters for controlling the motors Ml and Mr.

[0040] If the answer to step S21 is negative because none of the motors Ml, Mr has failed, the routine is immediately terminated. On the other hand, if the answer to step S21 is positive because either one of the motors Ml (Mr) has failed, the actuator 15 advances the support member 14 (step S22). This step S22 is an execution step for engaging the clutch mechanism C, and therefore the control amount of the actuator 15 is set so that the movement amount of the support member 14 is equal to or greater than the first predetermined amount L1 and less than the second predetermined amount L2.

[0041] By advancing the support member 14 in step S22, the movable member 5 is pressed, the annular groove 6 is expanded, and the friction materials 10, 11 come into frictional contact with each other. That is, the clutch mechanism C is engaged (step S23). Then, torque is output only from the motor Mr (Ml) in the direction that is not faulty (step S24). In this case, the torque is divided and transmitted to the left and right drive shafts Sl, Sr. Therefore, in step S24, the required torque of the motor Mr (Ml) is set to the combined value of the torque required for the left and right wheels. Note that if the required torque is equal to or greater than the upper limit torque of the motor Mr (Ml), the required torque of the motor Mr (Ml) is set to the upper limit torque.

[0042] Next, it is determined whether the driver has performed a steering operation (step S25). This step S25 can be determined based on a signal from a steering angle sensor that detects the amount of steering operation, as in conventional vehicles. If the steering has not been operated and the result of the determination in step S25 is negative, the actuator 15 further advances the support member 14 within a range equal to or less than a second predetermined amount L2 in order to prevent the clutch mechanism C from slipping (step S26).

[0043] On the other hand, if the steering is operated and the result of step S25 is affirmative, the actuator 15 moves the support member 14 backward within a range equal to or greater than the first predetermined amount L1 in order to allow differential rotation between the inner and outer wheels (step S27).

[0044] 1, even if one of the motors Ml (Mr) fails, the drive unit 1 can perform evacuation running by engaging the clutch mechanism C and outputting torque from the other motor Mr (Ml). In addition, when turning during such evacuation running, the transmission torque capacity of the clutch mechanism C can be reduced to allow differential rotation of the left and right drive shafts Sl, Sr, thereby preventing a decrease in running stability.

[0045] Fig. 7 shows a flowchart for explaining a method for controlling the actuator 15 when traveling on a rough road. In the example shown in Fig. 7, first, it is determined whether or not torsional resonance has occurred (step S31). This step S31 is a step for determining whether or not the frequency of the torsional torque generated by repeated spinning and contact of the drive wheels is the resonance frequency of the motors Ml, Mr, the power transmission units Tl, Tr, or the drive shafts Sl, Sr, and the frequency of the torsional torque can be obtained based on a signal from a resolver that detects the rotation speed of the motors Ml, Mr. Then, it is determined whether or not the frequency of the torsional torque matches the natural frequency of the motors Ml, Mr, the power transmission units Tl, Tr, or the drive shafts Sl, Sr.

[0046] If the answer to step S31 is negative because torsional resonance is not occurring, the routine is terminated. On the other hand, if the answer to step S31 is positive because torsional resonance is occurring, the actuator 15 advances the support member 14 so that the clutch mechanism C transmits torque (step S32). In other words, the clutch mechanism C functions as a friction damper.

[0047] Next, it is determined whether or not the torsional resonance has increased (step S33). This step S33 is a step for determining whether or not the transmission torque capacity of the clutch mechanism C is appropriate, and can be determined based on the amount of fluctuation in the rotation speed of the motors Ml and Mr detected by the resolvers.

[0048] If the torsional resonance has increased and the answer is YES in step S33, the transmission torque capacity of the clutch mechanism C is adjusted (step S34), and the process returns to step S33. In this step S34, for example, the actuator 15 moves the support member 14 further forward to increase the frictional force generated between the friction materials 10, 11.

[0049] On the other hand, if the torsional resonance has not increased and therefore the answer to step S33 is NO, the actuator 15 moves the support member 14 backward (step S35). As a result, the movable member 5 is pressed by the spring 7, and the friction materials 10, 11 are released. That is, the clutch mechanism C is released (step S36).

[0050] As described above, the drive device 1 shown in FIG. 1 can suppress torsional resonance by controlling the amount of friction by controlling the transmission torque capacity of the clutch mechanism C, thereby suppressing a decrease in the durability of the drive device 1 caused by driving on rough roads, for example.

[0051] In addition, the energy efficiency of the motors Ml and Mr varies depending on the operating point determined by the rotation speed and torque due to their structure. Specifically, when rotating at less than a predetermined rotation speed, the energy efficiency improves as the rotation speed increases, and when rotating at a rotation speed higher than the predetermined rotation speed, the energy efficiency deteriorates as the rotation speed increases. Similarly, when the output torque is less than the predetermined torque, the energy efficiency improves as the output torque increases, and when the output torque is higher than the predetermined torque, the energy efficiency deteriorates as the output torque increases.

[0052] Therefore, when the torque required for each drive wheel is relatively small, it may be more energy efficient to output torque from only one motor Ml (Mr) than to output torque from each of the motors Ml and Mr.

[0053] FIG. 8 shows a flow chart for explaining a method for controlling the actuator 15 in consideration of the energy efficiency of the motors Ml and Mr. The control example shown here is an example of control applied to an autonomous vehicle that can automatically travel by determining a route ahead and a travel plan (output torque, vehicle speed, etc.) for traveling the route without the driver's driving operation. In this control example, the travel route and the state of surrounding traveling vehicles are detected (step S41). This step S41 is a step for determining whether or not the situation allows straight-line cruising. The travel route is a trajectory of positions within a traveling lane when traveling toward a predetermined destination, and can be obtained in advance by an electronic control device. The state of surrounding traveling vehicles can be detected based on signals from communication devices such as vehicle-to-vehicle communication, in addition to detectors such as radar and lasers provided in the vehicle.

[0054] Next, it is determined whether or not there is a need to turn or avoid danger (step S42). In other words, it is determined whether or not the vehicle can travel straight ahead. This step S42 can be determined based on the signal detected in step S41.

[0055] If the answer to step S42 is YES because of the need to turn or avoid danger, the vehicle turns or travels to avoid danger (step S43) and returns to step S42. On the other hand, if the answer to step S42 is NO, the vehicle can travel straight ahead, with the left and right drive wheels running at the same rotation speed and torque. Therefore, if the answer to step S42 is NO, the actuator 15 moves the support member 14 forward (step S44). This step S44 is an execution step for engaging the clutch mechanism C, and therefore the control amount of the actuator 15 is set so that the movement amount of the support member 14 is equal to or greater than the first predetermined amount L1 and less than the second predetermined amount L2.

[0056] Then, torque is output from only one of the left motor Ml and the right motor Mr (Mr) to travel straight ahead (step S45).

[0057] Next, it is determined whether or not to continue traveling straight ahead with the clutch mechanism C engaged. Specifically, similar to step S41, the traveling route and the state of surrounding traveling vehicles are detected (step S46), and similar to step S42, it is determined whether or not there is a need to turn or avoid danger (step S47).

[0058] If the answer to step S47 is affirmative because of the need to turn or avoid danger, the clutch mechanism C is released. That is, the support member 14 is moved backward by the actuator 15. By moving the support member 14 backward in this manner, the rolling element 4 is released from the annular groove 6 (step S48), and then the movable member 5 is pressed by the spring 7 to release the friction materials 10, 11 (step S49), and the process returns to step S42.

[0059] On the other hand, if the answer to step S47 is negative because there is no need to turn or avoid danger, the clutch mechanism C is kept engaged and torque is output from only one of the left motor Ml and the right motor Mr (Mr) to drive straight ahead (step S50).

[0060] Next, the straight ahead cruising mode is released by an electronic control device or the like (step S51), and preparations for driving are started to output torque from each of the motors Ml and Mr (step S52). Therefore, the actuator 15 moves the support member 14 backward. As a result, the rolling element 4 is released from the annular groove 6 (step S53), and the movable member 5 is pressed by the spring 7 to release the friction materials 10 and 11. That is, the clutch mechanism C is released (step S54).

[0061] 1, when traveling straight ahead, the clutch mechanism C is engaged and torque is output from only one of the motors Ml (Mr), thereby allowing the vehicle to travel. Therefore, the operating point of the motor Ml (Mr) can be set to an operating point with good energy efficiency, thereby improving the energy efficiency of the entire drive system 1. [Explanation of symbols]

[0062] 1 Drive unit 2l Left cylindrical shaft 2r Right-hand cylindrical shaft 4 Rolling elements 5 Movable parts 6 Annular groove 10,11 Friction material 12 Pressing mechanism 14 Support member 15 Actuators 16 Parking Gear 17 Parking Pole C Clutch mechanism Ml, Mr motor Sl, Sr drive shaft Tl,Tr Power transmission section

Claims

[Claim 1] A drive unit including a left motor, a left power transmission unit that transmits torque of the left motor, a left drive shaft connected to the left power transmission unit, a right motor, a right power transmission unit that transmits torque of the right motor, and a right drive shaft connected to the right power transmission unit, a parking gear in one of the left side power transmission unit and the right side power transmission unit, and a movable member in frictional contact with the other of the left side power transmission unit and the right side power transmission unit, A parking pole is provided which meshes with the parking gear, A pressing mechanism is provided that presses the movable member toward the other power transmission part as the parking pole moves in a locking direction to engage with the parking gear. A drive device characterized by:

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