JP4246317B2 - Electric drive device for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle electric drive device provided between left and right driven wheels of a vehicle in which one of a front wheel and a rear wheel is driven by an engine and the other is a driven wheel.
[0002]
[Prior art]
Conventionally, as this type of electric drive device, as seen in Japanese Patent Application Laid-Open No. 9-79347 and Japanese Patent Application Laid-Open No. 9-79348, both the output torque of the electric motor and the electric motor are applied to the left and right driven wheels. A power transmission mechanism that is switchable between a first state that transmits the output torque of the electric motor as a driving force to one of the left and right driven wheels and a second state that transmits the output torque as a braking force to the other, and a power transmission mechanism A dog clutch that is switched between a first state and a second state and that is switched by a solenoid. When the vehicle starts, the power transmission mechanism is switched to the first state and the electric motor is driven to drive the left and right slaves. Start assist control is performed to assist the start by driving the driving wheel. After the start, the power transmission mechanism is switched to the second state, and the electric motor is driven while the power transmission mechanism is maintained in the second state when the vehicle turns. Driving force to the driven wheels of the turning outer wheel side, it is to perform a turning assist control for assisting the turning by applying a braking force to the driven wheels of the inner ring has been known by.
[0003]
[Problems to be solved by the invention]
In the above conventional example, the turn assist control may be executed following the start assist control. In this case, even if the energization to the solenoid of the dog clutch is stopped and the power transmission mechanism is switched from the first state to the second state, the torque from the electric motor is applied to the dog clutch by the driving of the electric motor by the turning assist control. By acting, the dog clutch is self-locked to the previous state due to the friction between the tooth clutch side surfaces, and the turning assist control is performed with the power transmission mechanism held in the first state, which adversely affects the behavior of the vehicle. In some cases, the electric motor may be damaged.
[0004]
An object of the present invention is to provide an apparatus capable of preventing the turning assist control from being performed while the power transmission mechanism is held in the first state.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is an electric drive device for a vehicle provided between left and right driven wheels of a vehicle in which one of a front wheel and a rear wheel is driven by an engine and the other is a driven wheel. The first state where both the electric motor and the output torque of the electric motor are transmitted to the left and right driven wheels as driving force, and the output torque of the electric motor as the driving force to one of the left and right driven wheels and the braking force to the other A power transmission mechanism that is switchable between a second state for transmission and a dog clutch that is switched by a solenoid for switching the power transmission mechanism between the first state and the second state; When the transmission mechanism is switched to the first state and the electric motor is driven, the left and right driven wheels are driven to perform start assist control to assist the start. After the start, the power transmission mechanism is switched to the second state and the vehicle Power when turning Driving assist control that assists turning by applying driving force to the driven wheel on the turning outer wheel side and applying braking force to the driven wheel on the inner ring side by driving the electric motor while holding the reach mechanism in the second state Are provided with prohibiting means for prohibiting execution of the turning assist control immediately after the start assist control is completed.
[0006]
According to the present invention, a period from the completion of the start assist control to the start of the turn assist control is secured, and the dog clutch is reliably switched without receiving torque within this period, and thus the power transmission mechanism is It is possible to prevent the turning assist control from being performed while being held in the first state.
[0007]
Further, the prohibiting means of the present invention prohibits the execution of the turning assist control until a predetermined time elapses after the completion of the start assist control , or the vehicle speed is set higher than a first predetermined value for completing the start assist control. The turning assist control is prohibited from being executed until the second predetermined value or more is reached .
[0008]
By the way, when the prohibiting means is provided as described above, turning assist control is started during turning, and driving force is suddenly applied to the outer wheel driven wheel and braking force is applied to the inner wheel driven wheel, which may cause a shock in the vehicle behavior. There is sex.
[0009]
For this reason, it is desirable to provide a torque gradually increasing means for gradually increasing the output torque of the electric motor when the turning assist control is started so as not to shock the vehicle behavior.
[0010]
In this case, it is possible to gradually increase the output torque of the electric motor over time. However, when the execution of the turn assist control is prohibited until the vehicle speed becomes equal to or higher than the second predetermined value, the second predetermined value is used. And a third predetermined value set higher than this, the output torque of the electric motor may be gradually increased as the vehicle speed increases.
[0011]
Note that to correspond to the inhibiting means in the embodiment described later, a process to S21 ₂ steps from step S17 in FIG. 4, to correspond to the torque increasing means from S23 in the steps of FIG. 4 This is the process up to step S25.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a front wheel drive vehicle that drives left and right front wheels 3L, 3R via a transmission 2 by an engine 1, and an electric drive device 5 is provided between left and right rear wheels 4L, 4R as driven wheels. Yes.
[0013]
As shown in FIG. 2, the electric drive device 5 includes a pair of left and right electric motors 7L and 7R attached to a gear case 6, and a pair of left and right differential devices 8L and 8R as a power transmission mechanism in the gear case 6. It has.
[0014]
Each electric motor 7L, 7R is constituted by a DC brush motor having a rotor 7a, a stator 7b, and a brush 7c, and a reduction gear train 9L, 9R is connected to an output shaft 7d of each electric motor 7L, 7R. .
[0015]
Each differential device 8L, 8R is composed of a planetary gear type differential device having a sun gear 8a, a ring gear 8b, and a carrier 8d carrying a planetary pinion 8c meshing with both the gears 8a, 8b. The sun gear 8a of each differential device 8L, 8R is connected to each reduction gear train 9L, 9R, and the carrier 8d of each differential device 8L, 8R is connected to the axle of each rear wheel 4L, 4R via a constant velocity joint 10. Are connected. Further, the ring gears 8b and 8b of the left and right differential devices 8L and 8R are connected to each other so that the rotation of the ring gear 8b can be restrained by the brake means 11.
[0016]
The brake means 11 is constituted by a dog clutch including a movable dog 110 that is spline-engaged with the outer periphery of the ring gear 8b, and a fixed dog 111 that is fixed in the gear case 6 so as to face the movable dog 110 in the axial direction. Then, by engaging the dog tooth 110a at one end (left end) of the movable dog 110 with the dog tooth 111a of the fixed dog 111, the brake means 11 is turned on and the rotation of the ring gear 8b is restricted. A solenoid 112 is provided to move the movable dog 110 toward and away from the fixed dog 111 in the axial direction, and the brake means 11 is turned on and off by the solenoid 112.
[0017]
The solenoid 112 includes a rod 112c that is moved in one axial direction (leftward) against the spring 112b by energizing the coil 112a, and a fork 112d that engages the movable dog 110 is attached to the rod 112c. The movable dog 110 is moved back and forth in the axial direction integrally with the rod 112c.
[0018]
As shown in FIG. 3, the electric motors 7L and 7R and the solenoid 112 include left and right front wheel speed sensors 12L and 12R that detect rotational speeds VFL and VFR of the left and right front wheels 3L and 3R, and left and right rear wheels 4L and Left and right rear wheel speed sensors 13L, 13R that detect 4R rotational speeds VRL, VRR, brake switch 14, accelerator switch 15, sensor 16 that detects engine speed NE, and throttle opening of engine 1 A sensor 17 that detects θ, a shift position sensor 18 of the transmission 2, a longitudinal G sensor 19 that detects longitudinal acceleration acting on the vehicle, and a lateral G that senses lateral acceleration acting on the vehicle. It is controlled by a controller 21 that inputs a signal from the sensor 20. The controller 21 performs start assist control and turning assist. Performing the door control.
[0019]
The details are as shown in FIG. 4. The brake switch 14 is off (S1), the accelerator switch 15 is on (S2), the transmission 2 is in a non-neutral state (S3), and the average rear wheel speed VR (= (VRL + VRR) / 2) is determined to be a start when the four conditions of less than the first predetermined value VS1 (for example, 11 km / h) (S4), which is a reference for the start determination, are satisfied, and when it is determined to be a start, It is determined whether or not the assist flag F is set to “1” (S5). If F = 0, the difference between the average front wheel speed VF (= (VFL + VFR) / 2) and the average rear wheel speed VR Δ It is determined whether or not V is greater than or equal to a predetermined reference value ΔVS (S6). If ΔV ≧ ΔVS, it is determined that the front wheels 3L, 3R are slipping, the start assist flag F is set to “1” (S7), and then the solenoid 112 is energized to turn on the brake means 11. While turning on (S8), the electric motors 7L and 7R are driven in the forward rotation direction (forward movement) or in the reverse rotation direction (reverse movement). According to this, the output torque of each electric motor 7L, 7R is transmitted as driving force to each rear wheel 4L, 4R via each reduction gear train 9L, 9R and each differential device 8L, 8R, and the rear wheel 4L , 4R is driven to assist the start.
[0020]
By the way, in starting assistance, it is desired to control the output torque of the electric motors 7L and 7R so that the rear wheels 4L and 4R do not slip. Therefore, in this embodiment, the corners of the left and right rear wheels 4L and 4R are desired. Accelerations dVRL, dVRR are calculated based on signal changes of the rear wheel speed sensors 13L, 13R, and dVRL, dVRR is a first set value dVRS1 (for example, 0.8G and G are gravitational accelerations in terms of vehicle speed) that serve as a slip discrimination criterion. Whether dVRL and dVRR are less than dVRS1 is determined (S9 ₁ , S9 ₂ ). If dVRL and dVRR are grip recovery determination criteria, the second set value dVRS2 (for example, 0. 4G) It is determined whether it is equal to or less (S10 ₁ , S10 ₂ ) If dVRL and dVRR are equal to or lower than dVRS2, the slip determination flags FLS and FRS of the left and right rear wheels 4L and 4R are reset to “0” (S11 ₁ and S11 ₂ ), and the outputs of the left and right electric motors 7L and 7R are reset. The target torque value is set to a higher set value TH (for example, 40 kgfm) (S12 ₁ , S12 ₂ ). On the other hand, when dVRL and dVRR are equal to or higher than dVRS1, FLS and FRS are set to “1” (S13 ₁ and S13 ₂ ), and the target value of the output torque of each electric motor 7L and 7R is set to the lower setting value. TL (for example, 10 kgfm) is set (S14 ₁ , S14 ₂ ). When dVRS2 <dVRL and dVRR <dVRS1, it is determined whether FLS and FRS are set to “1” (S15 ₁ , S15 ₂ ). If FLS and FRS = 1, S14 ₁ , The process proceeds to step S14 ₂ , and if FLS and FRS = 0, the process proceeds to steps S 12 ₁ and S 12 ₂ . After setting the target value in this way, the electric motors 7L and 7R are driven and controlled so that the output torque becomes the target value (S16 ₁ , S16 ₂ ).
[0021]
Thus, until dVRL and dVRR are equal to or higher than dVRS1, that is, until the rear wheels 4L and 4R slip, the output torques of the electric motors 7L and 7R are maintained at TH, and the rear wheels 4L and 4R are once slipped. Then, the output torque of each electric motor 7L, 7R is reduced to TL until dVRL, dVRR becomes dVRS2 or less, that is, until the grip of each rear wheel 4L, 4R is recovered. The target value changes stepwise as shown by the dotted line in FIG. 5, but if the motor current is changed stepwise as it is, a shock due to a sudden torque change occurs, so the output torque is shown by the solid line in FIG. Thus, the electric motors 7L and 7R are controlled so as to gradually change toward the target value.
[0022]
When it is determined that the vehicle has started with VR ≧ VS1, or when it is determined that ΔV <ΔVS in step S6 even when starting, the start assist flag F is reset to “0” (S17). ), Energization of the solenoid 112 is stopped and the brake means 11 is turned off (S18). Next, it is determined whether or not VR has become equal to or higher than a second predetermined value VS2 (for example, 20 km / h) set higher than VS1. Otherwise (S19), if VR <VS2, the slip determination flags FLS and FRS of the rear wheels 4L and 4R are reset to "0" (S20 ₁ and S20 ₂ ), and the electric motors 7L and 7R are reset. The driving is stopped (S21 ₁ , S21 ₂ ). When the brake means 11 is turned off and the restraint of the ring gear 8b is released, the ring gear 8b idles in the same direction as the carrier 8d of the differential devices 8L and 8R, and no differential rotation occurs between the left and right rear wheels 4L and 4R. As long as the sun gear 8a of the differential devices 8L and 8R does not rotate, reverse driving from the rear wheels 4L and 4R side of the electric motors 7L and 7R does not occur.
[0023]
When VR ≧ VS2, the driving force of the front wheels 3L, 3R is calculated from the longitudinal acceleration acting on the vehicle, the engine speed NE, the throttle opening θ, and the transmission gear ratio of the transmission 2. Then, the target value MA of the turning assist moment set as shown in FIG. 6 is calculated by map search using the front wheel driving force and the lateral acceleration acting on the vehicle as parameters (S22). The target value MA is set to be zero when the vehicle is traveling straight ahead when the lateral acceleration is zero, and is increased as the lateral acceleration and the front wheel driving force increase.
[0024]
When the turning assist moment is requested, the electric motor on the outer ring side of the left and right electric motors 7L, 7R is rotated forward and the electric motor on the inner ring side is reversed while the brake means 11 is turned off. For example, when turning right, the left electric motor 7L is rotated forward and the right electric motor 7R is rotated reversely. According to this, the sun gear 8a of the left differential device 8L is rotated forward and the carrier 7d is rotated forward with respect to the ring gear 7b, and the sun gear 8a of the right differential device 8R is rotated reversely and the carrier 8d. Is reversed with respect to the ring gear 8b. In this case, a reaction force in the reverse direction acts on the ring gear 8b of the left differential device 8L, and a reaction force in the forward direction acts on the ring gear 8b of the right differential device 8R. Since 8b and 8b are connected to each other, both reaction forces are canceled out. Accordingly, with reference to the rotational speed of the ring gear 8b, the carrier 8d of the left differential 8L, that is, the left rear wheel 4L is accelerated, and the carrier 8d of the right differential 8R, that is, the right rear wheel 4R. Is slowed down. Thus, a driving force is applied to the left rear wheel 4L, which is the outer wheel, and a braking force is applied to the right rear wheel 4R, which is the inner wheel, generating a yawment in the right turning direction and assisting the turning.
[0025]
Here, when the turn assist control is performed following the start assist control, even if the energization to the solenoid 112 is stopped, the torque is applied to the brake means 11 by driving the left and right electric motors 7L and 7R for the turn assist. Due to this torque, the tooth side surfaces of the dog teeth 110a and 111a of the movable dog 110 and the fixed dog 111 are pressed against each other, and the friction between the tooth side surfaces prevents the movable dog 110 from being detached from the fixed dog 111 by the biasing force of the spring 112b. The brake means 11 remains on. However, in this embodiment, the turning assist control is not executed until VR rises to VS2 after VR ≧ VS1 is satisfied and the start assist control is completed. It is possible to prevent the turning assist control from being executed while the means 11 is on.
[0026]
If the output torque of the electric motors 7L and 7R is raised so that the turning assist moment of the target value MA calculated in step S22 is obtained from the beginning of the turning assist control, VR ≧ VS2 during turning acceleration. As a result, the vehicle suddenly bends and shocks the vehicle behavior. Therefore, in the present embodiment, as a correction coefficient for the turning assist moment, as shown in FIG. 7, from 0 as the VR increases between VS2 and a third predetermined value VS3 (for example, 30 km / h) set higher than VS2. A vehicle speed coefficient K that gradually increases to 1 is set, and it is determined whether or not VR is equal to or higher than VS3 (S23). If VR <VS3, a vehicle speed coefficient K corresponding to VR is calculated by table search (S24). ), The target value MA of the turning assist moment is corrected to a value multiplied by the vehicle speed coefficient K (S25).
[0027]
Then, it calculates a target value of the reverse torque of the electric motor target value and inner side of the normal rotation torque of the electric motor required outer ring to obtain a turn assist moment target value MA (S26 _1, S26 ₂₎ The outer ring-side electric motor is driven to rotate in the forward direction and the inner ring-side electric motor is driven in the reverse direction so that the target value torque is output (S27 ₁ , S27 ₂ ). Thus, when the turning assist control is started when VR ≧ VS2 during turning acceleration, the turning assist moment is gradually increased toward the target value MA until the vehicle is accelerated from VS2 to VS3. The turning assist is performed smoothly without causing a shock of behavior.
[0028]
By the way, FIG. 6 shows a map in which an ideal turning assist moment required in the driving state of the vehicle defined by using the front wheel driving force and the lateral acceleration as parameters is set as the turning assist moment target value MA. . According to FIG. 6, even in a straight traveling state where the lateral acceleration is nearly zero, MA ≠ 0 at the time of large acceleration of the front wheel driving force, and turning assist control is performed. As a result, turning assist control is frequently executed, and the charge / discharge balance of the battery is deteriorated by energization of the motors 7L and 7R.
[0029]
In order to solve such a problem, a dead zone is set to the target value MA of the turning assist moment within a range that does not impair the turning performance of the vehicle, and in the MA calculation process in step S22 of FIG. 4, as shown in FIG. After searching for the MA from the map of FIG. 6 (S22-1), it is determined whether the MA is equal to or less than the upper limit value MAS of the dead zone (S22-2), and when MA ≦ MAS, MA is set to zero. rewriting (S22-3), it may be calculated target value of the motor torque in S26 _1, S26 ₂ steps based on MA calculated in this way. According to this, even when the MA retrieved from the map of FIG. 6 becomes MA ≠ 0 during acceleration in a straight-ahead state where the lateral acceleration is almost zero, MA is rewritten to zero because MA ≦ MAS. S26 is _1, S26 target value of the motor torque calculated in _two steps zero, motor 7L, the 7R not energized, deterioration in charge-discharge balance of the battery is prevented. Note that the MA map may be set so that MA = 0 regardless of the front wheel driving force when the lateral acceleration is below a predetermined value.
[0030]
The first embodiment that performs the start assist and the turn assist using the pair of left and right electric motors 7L and 7R has been described above. However, as in the second embodiment shown in FIG. 9, one electric motor 7 is used. It is also possible to perform start assist and turn assist. In the second embodiment, the power transmission mechanism between the electric motor 7 and the left and right rear wheels 4L, 4R is constituted by a pair of bevel gear type differential devices 80L, 80R.
[0031]
Each differential device 80L, 80R is formed by pivotally supporting a differential case 80a with a pair of side gears 80b, 80c made of bevel gears and a pinion 80d meshing with both side gears 80b, 80c. The first side gears 80b and 80b on the inner side in the axial direction of 80R are connected to each other. The electric motor 7 is connected to one of the differential devices 80L and 80R, for example, the differential case 80a of the right differential device 80R via a gear train 9, and the second side gear on the axially outer side of the differential device 80R. 80c is connected to the axle of the right rear wheel 4R through the constant velocity joint 10. The differential case 80a of the left differential device 80L is prevented from rotating, and is connected to the axle of the left rear wheel 4L with the first side gear 80b and the second side gear 80c on the inner side in the axial direction of the differential device 80L. The speed joint 10 is selectively connected via the switching means 22. The switching means 22 includes a movable dog 22a that is slidably engaged with the constant velocity joint 10 for the left rear wheel 4L in an axial direction, and a first side gear 80b and a second side gear 80c of the left differential gear 80L. And the fixed dogs 22b and 22c respectively attached thereto, and the movable dog 22a is advanced and retracted by a solenoid 22d controlled by a controller (not shown) to selectively engage the fixed dogs 22b and 22c. I try to match.
[0032]
When the constant velocity joint 10 for the left rear wheel 4L is connected to the first side gear 80b of the left differential 80L, the left rear wheel 4L is directly connected to the first side gear 80b of the right differential 80R, When the differential case 80a of the right differential device 80R is rotated forward or reverse by the electric motor 7, both the left and right rear wheels 4L and 4R are rotated forward or reversely to perform forward or reverse start assistance.
[0033]
When the constant velocity joint 10 for the left rear wheel 4L is connected to the second side gear 80c of the left differential 80L, the first side gear 80b rotates in the opposite direction at the same speed as the left rear wheel 4L, and the left and right rear wheels 4L As long as 4R rotates at a constant speed, the differential case 80a of the right differential 80R does not rotate. When the differential motor 80a of the right differential device 80R is rotated forward by the electric motor 7, the second side gear 80c of the differential device 80R is rotated at an increased speed relative to the first side gear 80b, and the right rear wheel 4R is moved to the left rear. If the speed of the differential case 80a of the differential gear 80R on the right side is reversed, the first side gear 80b is rotated at a higher speed than the second side gear 80c of the differential gear 80R. Is increased more than the right rear wheel 4R, and turning assist is performed.
[0034]
In the second embodiment as well, as described above, the output torque of the electric motor 7 is controlled according to the angular acceleration of the rear wheels 4L and 4R, thereby suppressing the slip of the rear wheels and the reliability of the start assist. In addition, by prohibiting the execution of the turning assist control until VR ≧ VS2, the switching means 22 moves the constant velocity joint 10 for the left rear wheel 4L to the first side gear 80b of the left differential 80L. It is possible to prevent the turning assist control from being executed while being held in a directly connected state. Further, by correcting the target value MA of the turning assist moment using the vehicle speed coefficient K, the vehicle action can be smoothly performed without causing a shock. The turning assist can be performed.
[0035]
In the above embodiment, the turn assist control prohibition period after the start assist control is completed and the gradual increase of the turn assist moment after the start of the turn assist control are defined based on VR (vehicle speed). Execution of the turn assist control may be prohibited until a predetermined time has elapsed from the completion of the control, and the turn assist moment may be gradually increased from the start time of the turn assist control toward the target value MA.
[0036]
【The invention's effect】
As is apparent from the above description, according to the present invention, the turning assist control is executed while the power transmission mechanism is in the start assist state (first state), and the vehicle behavior and the electric motor are adversely affected. Can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of use of the apparatus of the present invention. FIG. 2 is a sectional view of a first embodiment of the apparatus of the present invention. FIG. 3 is a block diagram of a control system of the first embodiment. [Fig. 5] Graph showing the torque change of the electric motor during start assist [Fig. 6] Graph showing the setting of the target value of the turning assist moment [Fig. 7] Graph showing the setting of the vehicle speed coefficient [Fig. FIG. 8 is a flowchart showing processing for calculating a target value of a turning assist moment. FIG. 9 is a skeleton diagram showing a second embodiment of the device of the present invention.
1 Engine 3L, 3R Front wheels (drive wheels)
4L, 4R Rear wheel (driven wheel) 5 Electric drive device 7L, 7R, 7 Electric motor 8L, 8R, 80L, 80R Differential device (power transmission mechanism)
11 Brake means (Dog clutch) 21 Controller 22 Switching means (Dog clutch) 112, 22d Solenoid

Claims (3)

An electric drive device for a vehicle provided between left and right driven wheels of a vehicle in which one of a front wheel and a rear wheel is driven by an engine and the other is a driven wheel,
A first state in which the electric motor and the output torque of the electric motor are both transmitted to the left and right driven wheels as a driving force, and the output torque of the electric motor is transmitted to one of the left and right driven wheels as a driving force and the other as a braking force A power transmission mechanism that is switchable between a second state and a dog clutch that is switched by a solenoid to switch the power transmission mechanism between the first state and the second state;
When the vehicle starts, the power transmission mechanism is switched to the first state and the electric motor is driven to drive the left and right driven wheels to perform start assist control. After the start, the power transmission mechanism is set to the second state. When the vehicle is turning, the electric motor is driven while the power transmission mechanism is held in the second state, thereby applying driving force to the driven wheel on the outer wheel side and braking force to the driven wheel on the inner wheel side. For performing turn assist control to assist
Providing a prohibition means to prohibit the execution of the turning assist control immediately after the completion of the start assist control,
The prohibiting means is configured to prohibit the execution of the turn assist control until the vehicle speed becomes equal to or higher than a second predetermined value set higher than a first predetermined value for completing the start assist control. Electric drive device for vehicles.   2. The vehicle electric drive device according to claim 1, further comprising a torque gradually increasing means for gradually increasing the output torque of the electric motor when the turning assist control is started.   When the vehicle speed becomes equal to or higher than the second predetermined value and the turn assist control is started, an increase in the vehicle speed increases between the second predetermined value and a third predetermined value set higher than the second predetermined value. 2. The vehicle electric drive device according to claim 1, further comprising torque gradually increasing means for gradually increasing the output torque.

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