JP6420856B2 - Vehicle drive system - Google Patents

Description

  The present invention relates to a vehicle drive system. More specifically, the present invention relates to a vehicle drive system that detects the inclination of the vehicle or the road surface on which the vehicle is located while the vehicle is running, and limits the torque for driving the wheels of the vehicle when the inclination angle is large.

  2. Description of the Related Art Conventionally, a traction control system (hereinafter referred to as “TCS”) that has a plurality of electric motors and an internal combustion engine and restricts torque for driving left and right rear wheels in order to suppress slipping of left and right rear wheels is provided. Vehicles are known. When a slip occurs in any of the left and right rear wheels, the torque applied to the rear wheel where the slip has occurred is suppressed to suppress the slip (see, for example, Patent Document 1).

Japanese Patent No. 59777982

  Compared to the case of traveling on a flat road surface when the vehicle is climbing, slip is likely to occur, and it has been required to effectively suppress the occurrence of slip when the vehicle is climbing.

  The present invention is for solving the above-described problems, and an object of the present invention is to provide a vehicle drive system that can suppress slipping of wheels of a vehicle when climbing a steep slope while the vehicle is traveling. .

  In order to achieve the above-described object, the present invention is directed to any one of front wheels (for example, front wheels Wf, Wf described later) and rear wheels (for example, rear wheels Wr (RWr, LWr) described later) of a vehicle (for example, vehicle 3 described later). On the other hand, a first drive device (for example, a first drive device 1 to be described later) that drives the first drive wheel (for example, front wheels Wf and Wf to be described later) and the front wheel or the rear wheel of the vehicle. A second driving device (for example, a second driving device 2 described later) for driving a second driving wheel (for example, a rear wheel Wr (RWr, LWr) described later), the first driving device and the second driving device; A vehicle drive system (for example, a vehicle drive system 10 to be described later) including a control device (for example, an ECU 6 to be described later) that controls the drive states of the first drive wheel and the second drive wheel. , The control device during the traveling of the vehicle Detecting the inclination of the vehicle or the road surface on which the vehicle is located based on a correlation amount (for example, “wheel speed” described later, “detected value detected by the resolver 94”) correlated with the speed, Torque that performs control to limit the torque for driving the first drive wheel of the vehicle when it is detected that the inclination angle of the vehicle or the inclination angle of the road surface on which the vehicle is located is larger than a predetermined angle. It has a limiting part (for example, below-mentioned FrTCS62, steep climb control part 65), It is characterized by the above-mentioned.

  In the present invention, the torque limiting unit detects the inclination of the vehicle or the road surface on which the vehicle is located, and detects that the inclination angle of the vehicle or the road surface on which the vehicle is located is greater than a predetermined angle. In addition, in order to perform control to limit the torque for driving the first drive wheel of the vehicle, a high value torque is applied to the first drive wheel so that the first drive wheel slips when the vehicle climbs steeply. It is possible to suppress the occurrence of slipping, and the first driving wheel can be prevented from slipping.

For example, the torque limiting unit may calculate the difference between the actual wheel speed of the first drive wheel and the target wheel speed of the first drive wheel by calculating the terms I and D by PID control. It is preferable to determine the start and end timing of the control for limiting the torque.
This makes it possible to start traction control as soon as the vehicle starts to climb rapidly. Further, when the vehicle completes the steep climb, the traction control can be finished immediately. In addition, during a steep climb of the vehicle, it is possible to perform control to appropriately change the torque in response to a change in the slip condition of the first drive wheel. That is, it is possible to perform control to limit the torque with high responsiveness.

Further, it is preferable that the torque limiting unit sets a lower limit value of a target wheel speed of the first drive wheel corresponding to an inclination angle of the vehicle or a road surface on which the vehicle is located.
As a result, it is possible to flexibly cope with different accelerations that can be generated depending on the inclination angle of the road surface, and it is possible to suppress excessive torque limitation by the torque limiting unit.

The torque limiting unit limits the torque by changing a value of an allowable slip ratio of the first driving wheel with respect to a road surface in accordance with an inclination angle of the vehicle or an inclination angle of a road surface on which the vehicle is located. It is preferable to perform control.
As a result, when the vehicle starts to climb rapidly and the first drive wheel starts to slip, the torque limiting unit can immediately limit the torque. For this reason, it becomes possible to improve the responsiveness with respect to the steep climb of a vehicle.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle drive system which can suppress the slip of the wheel of a vehicle when climbing a steep slope during driving | running | working of a vehicle can be provided.

It is a figure showing a vehicle carrying a vehicle drive system concerning a 1st embodiment of the present invention. It is a figure which shows the state of the electric motor in the driving | running | working state of the vehicle which concerns on the said embodiment, and the state of a separation mechanism. It is a functional block diagram which shows the structure of ECU which concerns on the said embodiment. It is a flowchart which shows the process at the time of driving | running | working of the vehicle of the control in the uphill angle estimation part of ECU which concerns on the said embodiment. It is a time chart which shows the state at the time of climbing of the vehicle carrying the vehicle drive system which concerns on the said embodiment. It is a flowchart which shows the first half part of the process at the time of steep climbing of the vehicle of the control in the steep climbing control part of ECU which concerns on the said embodiment. It is a flowchart which shows the latter half part of the process at the time of steep climbing of the vehicle of the control in the steep climbing control part of ECU which concerns on the said embodiment. It is a time chart which shows the state at the time of steep climbing of the vehicle carrying the vehicle drive system which concerns on the said embodiment. It is a graph which shows the relationship between an inclination angle and the minimum wheel speed in the vehicle carrying the vehicle drive system which concerns on the said embodiment. It is a graph which shows the relationship between the estimated vehicle body speed and an allowable slip ratio in the vehicle carrying the vehicle drive system which concerns on the said embodiment. It is a graph which shows the relationship between an inclination angle and P gain in the vehicle carrying the vehicle drive system which concerns on the said embodiment. It is a time chart which shows the relationship between the wheel speed and the rotation speed of an electric motor in the state at the time of climbing of the vehicle carrying the vehicle drive system which concerns on 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a vehicle 3 equipped with a vehicle drive system 10 according to the present embodiment. The vehicle 3 equipped with the vehicle drive system 10 according to the present embodiment is a hybrid vehicle. As shown in FIG. 1, a vehicle drive system 10 mounted on a vehicle 3 includes a first drive device 1, a second drive device 2, and an electronic control unit as a control device that controls these drive devices 1 and 2. (Hereinafter referred to as “ECU”) 6, a PDU (power drive unit) 8, and a battery 9.

  The first drive device 1 is provided at the front portion of the vehicle 3 and drives the front wheels RWf and LWf as first drive wheels. The first drive device 1 includes an internal combustion engine (ENG) 4, an electric motor 5, and a transmission 7. The internal combustion engine 4 and the electric motor 5 are connected in series, and torques of the internal combustion engine 4 and the electric motor 5 are transmitted to the front wheels RWf and LWf via the transmission 7.

  The internal combustion engine 4 is a V-type 6-cylinder engine, for example, and generates torque for running the hybrid vehicle 3 by burning fuel. The crankshaft of the internal combustion engine 4 is connected to the output shaft of the electric motor 5.

  The electric motor 5 is, for example, a three-phase AC motor, and generates torque for causing the vehicle 3 to travel by using electric power stored in the battery 9. The electric motor 5 is connected to the battery 9 via a PDU 8 equipped with an inverter, and assists the driving force of the internal combustion engine 4.

  The transmission 7 converts the torque generated in the internal combustion engine 4 into a rotation speed and torque at a desired gear ratio, and transmits them to the front wheels LWf and RWf.

  The second drive device 2 is provided at the rear portion of the vehicle 3 and drives rear wheels Wr (RWr, LWr) as second drive wheels. The 2nd drive device 2 has electric motors 2A and 2B. The torques of these electric motors 2A and 2B are transmitted to the rear wheels Wr (RWr, LWr).

  Similarly to the electric motor 5, the electric motors 2 </ b> A and 2 </ b> B are, for example, three-phase AC motors, and generate torque for causing the vehicle 3 to travel using electric power stored in the battery 9. The electric motors 2A and 2B are connected to the battery 9 via the PDU 8 including an inverter. When a control signal from the ECU 6 is input to the PDU 8, power supply from the battery 9 and energy to the battery 9 are obtained. Regeneration is controlled.

  Each of the four front wheels Wf (RWf, LWf) and the rear wheels Wr (RWr, LWr) is provided with a friction brake (not shown). This friction brake is composed of, for example, a hydraulic disc brake. When the driver depresses the brake pedal, the depressing force is amplified and transmitted to the brake pad via a hydraulic cylinder, etc., and a frictional force is generated between the brake disk and the brake pad attached to each drive wheel. Each drive wheel is braked.

An operation during normal running of the second drive device 2 having the above configuration will be described. FIG. 2 is a diagram showing the state of the electric motors 2A and 2B and the state of the separation mechanism (one-way clutch and hydraulic brake) in the traveling state of the vehicle.
In FIG. 2, the front represents the first drive device 1 that drives the front wheels Wf (RWf, LWf), the rear represents the second drive device 2 that drives the rear wheels Wr (RWr, LWr), and ○ represents the operation (drive, X means inactive (stopped). Further, the MOT state represents the state of the electric motors 2A and 2B of the second drive device 2. The ON state of the separation mechanism means that the two ring gears for setting the MOT drive state or the MOT regeneration state are locked (engaged) by connecting the electric motors 2A, 2B and the rear wheels RWr, LWr. OFF means that each of the two ring gears is in a free state (ring free state). Moreover, OWC means the state of the one-way clutch which switches the state of these two ring gears, and BRK means the hydraulic brake which regulates rotation of a ring gear. The hydraulic brake is driven by driving a brake solenoid (BRKsol) under the control of the ECU 6.

First, since the first drive device 1 on the front wheel Wf (RWf, LWf) side and the second drive device 2 on the rear wheel Wr (RWr, LWr) side are both stopped, the electric motors 2A, 2B are stopped. It stops and the separation mechanism is inactive.
Next, after the key position is turned ON, the electric motors 2A and 2B of the second drive device 2 are driven when the EV starts. At this time, the separation mechanism is turned on by the one-way clutch, and the power of the electric motors 2A and 2B is transmitted to the rear wheels RWr and LWr.
Subsequently, at the time of acceleration, the two-wheel (four-wheel) drive state (AWD) in which both the first drive device 1 and the second drive device 2 are driven is set. At this time, the separation mechanism is turned on by the one-way clutch, The power of the electric motors 2A and 2B is transmitted to the rear wheels RWr and LWr.
In the EV cruise in the low / medium speed range, since the motor efficiency is good, the first driving device 1 is in the non-operating state, and the rear wheel single driving state (RWD) in which only the second driving device 2 is driven is set. Also at this time, the separation mechanism is turned on by the one-way clutch, and the power of the electric motors 2A and 2B is transmitted to the rear wheels RWr and LWr.

On the other hand, in the high speed cruise, the front drive single drive state (FWD) by the first drive device 1 is entered because the engine efficiency is good. At this time, the one-way clutch is turned off (OWC free) in the separation mechanism, the hydraulic brake is not activated, and the electric motors 2A and 2B are stopped.
In the case of natural deceleration, the one-way clutch is disengaged (OFFC free) in the disengaging mechanism, the hydraulic brake is not activated, and the electric motors 2A and 2B are stopped.

On the other hand, when decelerating and regenerating, for example, when driving by the driving force of the first drive device 1, the one-way clutch of the disengaging mechanism is disengaged and turned off (OWC free). However, when the hydraulic brake is engaged, the power of the output shaft for transmitting the driving force to each of the rear wheels Wr (RWr, LWr) is transmitted to the cylindrical shaft for transmitting the power of each of the electric motors 2A, 2B. Regenerative charging is performed by the electric motors 2A and 2B.
In normal running, the motor 2A, 2B regenerates and collects the running energy in cooperation with the braking control for the friction brake, but the regeneration of the motors 2A, 2B is prohibited when emergency braking is required (for example, during ABS operation). Thus, priority is given to the braking control by the friction brake. In this case, the one-way clutch is turned off (OWC free), and the hydraulic brake is not operated, thereby stopping the electric motors 2A and 2B.

  In the case of reverse travel, the first drive device 1 is stopped and the second drive device 2 is driven to become RWD, or the first drive device 1 and the second drive device 2 are both driven AWD. At this time, the electric motors 2A and 2B rotate in the reverse direction, and the one-way clutch of the separation mechanism is disengaged and turned off (OWC free). However, when the hydraulic brake is connected, the power for the electric motors 2A and 2B is output for transmitting the driving force from the cylindrical shaft for transmitting the power of each of the electric motors 2A and 2B to each of the rear wheels Wr (RWr and LWr). It is transmitted to the rear wheels RWr and LWr via the shaft.

Next, the configuration of the ECU 6 as the control device according to the present embodiment will be described.
The ECU 6 shapes an input signal waveform from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter referred to as a central processing unit). "CPU"). In addition, the ECU 6 includes a storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, and an output circuit that outputs a control signal to the PDU 8, the internal combustion engine 4, and the like.

  ECU6 which consists of the above hardware constitutions performs arithmetic processing based on the above-mentioned various arithmetic programs, and outputs a control signal according to the arithmetic result, thereby controlling the PDU 8, the internal combustion engine 4 and the like, Processing described below is performed.

Next, the ECU 6 will be described in more detail with reference to FIG. Here, FIG. 3 is a functional block diagram showing a configuration of the ECU 6 according to the present embodiment. As shown in FIG. 3, the ECU 6 includes a wheel speed sensor 91, an accelerator opening sensor 92, an engine speed sensor 93, a resolver 94, a lateral G sensor 95, a vehicle speed sensor 96, a steering angle sensor 97, a yaw rate sensor 98, and Detection signals from various sensors such as the front and rear G sensor 99 are input. On the other hand, as shown in FIG. 3, the ECU 6 outputs a control signal to the PDU 8 and the internal combustion engine (ENG) 4.
Further, the ECU 6 is a module for executing traction control unique to the present embodiment, a slip acquisition unit 61, a traction control system (hereinafter referred to as "FrTCS") 62, an uphill angle estimation unit 63, and a driving state. A switching unit 64 and a steep climbing control unit 65 are provided. Hereinafter, functions of these modules will be described.

The slip acquisition unit 61 acquires that an excess slip, which is a predetermined slip or more, has occurred on the front wheels Wf (RWf, LWf) as the first drive wheels. When the slip acquisition unit 61 acquires that an excess slip has occurred in the front wheels Wf (RWf, LWf), the slip determination flag is set to “1”, and an excess slip has occurred in the front wheels Wf (RWf, LWf). Is not acquired, the slip determination flag is set to “0”.
Here, it can be considered that the vehicle 3 is traveling while always generating minute slips on the drive wheels even on a dry road in a high μ state. However, if this is considered, the always-slip determination flag is set to “1”, and control according to the driving situation cannot be performed. Therefore, “excess slip” in the present embodiment excludes such minute slip. Hereinafter, occurrence of excess slip is also simply referred to as occurrence of slip.

  The FrTCS 62 is a part that performs traction control. The FrTCS 62 controls the front wheel Wf (RWf, LWf) by controlling the torque for driving the front wheel Wf (RWf, LWf) generated by the internal combustion engine 4 or the electric motor 5 based on the wheel rotational speed of the front wheel Wf (RWf, LWf). ) Is controlled.

Specifically, when the slip determination flag is set to “0” (that is, when the slip determination unit 612 has not acquired an excess slip), the FrTCS 62 performs a drive requested by the driver who operates the accelerator. By giving an instruction to the ECU 6 so as to satisfy a torque corresponding to the force (hereinafter referred to as “driver required torque”), the ECU 6 causes the internal combustion engine 4 and the electric motor 5 to output a command torque. The driver request torque can be calculated based on the current accelerator opening input from the accelerator opening sensor 82.
On the other hand, when the slip determination flag is set to “1” (that is, when the slip determination unit 612 has acquired an excess slip), the FrTCS 62 has the front wheel Wf (RWf, LWf) in which the excess slip has occurred. The command torque of the internal combustion engine 4 and the electric motor 5 connected to) is not a driver request torque but a predetermined torque.

The uphill angle estimation unit 63 is a part that detects the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located. The uphill angle estimation unit 63 estimates that a traveling direction uphill angle, which is an amount that increases as the traveling direction wheel of the vehicle 3 is tilted above the opposite side wheel, has occurred in the vehicle 3. Specifically, the uphill angle estimation unit 63 estimates the uphill angle by the front / rear G sensor 99 which is a G sensor separately disposed before and after the vehicle 3 when the vehicle 3 stops. When the vehicle 3 is traveling, the uphill angle is estimated based on the rotation speed of the electric motors 2A and 2B or the wheels ( rear wheels Wr (RWr, LWr) ).

The drive state switching unit 64 is based on either the slip condition or the lateral G condition, and either one of the front wheels RWf, LWf as the first drive wheels and the rear wheel Wr (RWr, LWr) as the second drive wheels. The vehicle 3 is driven by both the front wheels RWf and LWf as the first drive wheels and the rear wheels Wr (RWr and LWr) as the second drive wheels from the one-wheel single drive state (2WD) in which the vehicle 3 is driven only by Change the driving force distribution to AWD.
Here, the one-wheel single drive state includes FWD that drives the vehicle 3 only by the front wheels Wf (RWf, LWf) and RWD that drives the vehicle 3 only by the rear wheels Wr (RWr, LWr).
In addition to switching from 2WD to AWD, the driving state switching unit 64 executes switching of driving force distribution while maintaining AWD. Specifically, the drive state switching unit 64 switches the drive state of the vehicle 3 to AWD when the AWD request flag is set to “1”.

Here, the front / rear distribution setting means a distribution ratio of the driving force [N] between the traveling direction wheel of the vehicle 3 and its opposite side wheel. The driving force [N] is detected by the sensor, for example, the accelerator opening detected by the accelerator opening sensor 92, the engine speed detected by the engine speed sensor 93, and the electric motors 5, 2A, 2B, respectively. It is estimated and acquired based on each detection value detected by the resolver 94 provided.
Further, the front / rear distribution setting may be a distribution difference of the driving force [N] between the traveling direction wheel of the vehicle 3 and its opposite wheel.

Next, with reference to FIG. 4 and FIG. 5, the operation of detecting the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located and switching the driving state of the vehicle 3 to AWD will be described in more detail.
Here, FIG. 4 is a flowchart showing a process during traveling of the vehicle 3 in the control by the ECU 6 according to the embodiment.

  When the vehicle 3 is stopped, a detection signal is input from the front / rear G sensor 99 to the uphill angle estimation unit 63. In the uphill angle estimation unit 63, the detection signal is input to the filter unit 6311 of the uphill angle estimation unit 631 when the vehicle is stopped, and the noise component is removed. The filter unit 6311 has a low-pass filter, and in order to calculate the estimated inclination angle with higher accuracy, the pitching component is removed using the detection signal input to the previous filter unit 6311 as a reference value. The detection signal from which the pitching component has been removed is converted into an inclination angle value corresponding to the detection signal by subtracting a predetermined value from the detection signal in the inclination angle conversion unit 633, and output as an estimated value of the inclination angle. Is done.

  When the vehicle 3 is running and the above-described separation mechanism is in the ON state, the electric motors 2A and 2B and the rear wheels RWr and LWr are connected, and the MOT drive state or the MOT regeneration state in FIG. Sometimes, the detected value from the resolver 94 that can detect the rotational speed of the electric motors 2A and 2B by detecting the value according to the rotational speed of the electric motors 2A and 2B is input as a detection signal to the uphill angle estimating unit 63. Then, in the uphill angle estimation unit 63, the average value of the detection values from the resolvers 94 of the electric motors 2A and 2B is calculated, converted into the rotational speeds of the electric motors 2A and 2B, and used as the rotational speeds of the electric motors 2A and 2B. . In addition, when the vehicle 3 is traveling, the one-way clutch is disengaged and the electric motors 2A and 2B are separated from the rear wheels RWr and LWr because the disengagement mechanism is OFF. , The value of the wheel speed (the number of rotations of the rear wheels RWr, LWr) from the wheel speed sensor 91 is input as a detection signal to the uphill angle estimation unit 63. In the uphill angle estimation unit 63, the average value of the left and right wheel speeds (average value of the rotational speeds of the rear wheels RWr and LWr) is calculated and used as the rotational speed of the rear wheels RWr and LWr.

  In the uphill angle estimation unit 63, the detection signal from the wheel speed sensor 91 or the resolver 94 is input to the filter unit 6321 of the traveling uphill angle estimation unit 632, and noise components are removed. The filter unit 6321 has a low-pass filter, and in order to calculate the estimated tilt angle with higher accuracy, the pitching component is removed using the detection signal input to the previous filter unit 6321 as a reference value. The detection signal from which the pitching component has been removed is converted into a value of an inclination angle corresponding to the detection signal, and is output to the wheel acceleration calculation unit 6322 as an estimated value of the inclination angle.

In the wheel acceleration calculation unit 6322, the detection value or the wheel speed value from the resolver 94 of the electric motors 2A and 2B is converted into the acceleration value of the wheel (rear wheel RWr, LWr) and output to the wheel acceleration limit processing unit 6323. The
In the wheel acceleration limit processing unit 6323, when the acceleration value of the wheel (rear wheel RWr, LWr) obtained by the conversion in the wheel acceleration calculation unit 6322 is an abnormal value, the wheel acceleration value is converted into a predetermined value. Is done. Accordingly, the acceleration values of the wheels (rear wheels RWr, LWr) are suppressed within a predetermined value range so that an abnormal value that cannot be generated is not output from the wheel acceleration limit processing unit 6323. Then, the acceleration values of the wheels (rear wheels RWr, LWr) whose abnormal values have been corrected are output to the inclination angle conversion unit 633.
In the tilt angle conversion unit 633, a predetermined value is subtracted from the acceleration value, whereby the acceleration value is converted into a tilt angle value corresponding to the detection signal and output as an estimated tilt angle value.

  When the drive state switching unit 64 determines that the slope is above a predetermined slope based on the output estimated inclination angle, the separation mechanism is turned on by the one-way clutch. In this state, both the first driving device 1 and the second driving device 2 are driven, and the two-wheel (four-wheel) driving state (AWD) is set, and the power of the electric motors 2A and 2B is transmitted to the rear wheels RWr and LWr.

  The above operation will be described below with reference to a time chart along with the passage of time. FIG. 5 is a time chart showing the state of each part of the vehicle 3 equipped with the vehicle drive system 10 according to the embodiment. In the following description, “wheels” such as “wheel speed” and “wheel acceleration” mean the rear wheels RWr and LWr.

  When the vehicle 3 begins to climb, if the accelerator opening is constant, the wheel speed of the vehicle 3 gradually decreases at a constant rate as shown in FIG. The wheel acceleration remains at a constant value because the wheel speed decreases at a constant rate. Further, in the front-rear G sensor, an increase in value is detected when the posture of the vehicle 3 changes as the vehicle 3 climbs up. During this time, the uphill angle estimation unit 63 continues to calculate the estimated inclination angle, and the value of the estimated inclination angle continues to increase.

  Next, at time T1, when the climb angle estimation unit 63 calculates a value of the estimated tilt angle that exceeds a predetermined threshold indicated by a broken line, the ECU 6 recognizes that the vehicle 3 is climbing. At this time, the wheel speed that has continued to decrease due to the climbing of the vehicle 3 is constant, and therefore, the wheel acceleration temporarily increases to 0 at time T1, and then maintains the value of 0. Further, the ECU 6 starts to increase the climbing counter at a constant value per unit time. At this time, in the front-rear G sensor, the vehicle speed is kept constant, so a constant value is detected.

  Then, at time T2 after a predetermined time has elapsed from time T1, when the climbing counter exceeds a predetermined threshold indicated by a broken line, the flag for determination of traveling uphill is set to “1”. The drive state switching unit 64 sets the AWD request flag to the “1” state. Thus, by setting the AWD request flag to the state “1” at the time T2 after a predetermined time has elapsed from the time T1, the rear wheels RWr and LWr are less likely to follow the road surface and slip. When the state is reached, the drive state switching unit 64 performs switching from 2WD to AWD. A little later than this, at time T3, the wheel acceleration increases and the wheel speed starts to increase at a constant rate. The wheel acceleration remains a constant value. At this time, in the front and rear G sensors, the value temporarily increases, but a constant value is detected immediately thereafter. A constant value is also detected for the estimated inclination angle.

  Then, at time T4, when the wheel speed reaches a speed that does not require the AWD climbing, the climbing counter is reset, and the traveling climbing determination flag is set to “0”.

Next, with reference to FIGS. 6A and 6B, the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located is detected, and the vehicle 3 climbs a steep slope with a predetermined inclination angle or more (hereinafter referred to as “steep climb”). The operation of performing traction control will be described in more detail.
Here, FIG. 6A is a flowchart showing the first half of the processing at the time of steep climbing of the vehicle of the control in the steep climbing control unit of the ECU according to the embodiment. FIG. 6B is a flowchart showing the latter half of the processing at the time of the steep climb of the vehicle in the control of the steep climb control unit of the ECU according to the embodiment. FIG. 9 is a graph showing the relationship between the estimated vehicle speed and the allowable slip ratio in a vehicle equipped with the vehicle drive system according to the embodiment.

  In the steep climb control unit 65, the lateral G detected by the lateral G sensor is input to the filter unit 6501, and the noise component is removed. The detection signal from which the noise component has been removed is output to the allowable slip ratio calculation unit 6502. Further, the estimated inclination angle detected by the uphill angle estimation unit 63 is output to the allowable slip ratio calculation unit 6502. Allowable slip ratio calculating section 6502 calculates an allowable slip ratio of front wheels Wf (RWf, LWf) based on lateral G from which the noise component has been removed and the rotational speeds of electric motors 2A and 2B, and outputs the calculated allowable slip ratio to slip ratio selecting section 6503. .

  Specifically, for example, as shown in FIG. 9, when the vehicle 3 is traveling on a flat ground, if the estimated vehicle speed estimated by the rotation speed of the electric motors 2A and 2B is low, the allowable slip ratio Is set to a higher value, and the allowable slip ratio is set to be lower as the estimated vehicle speed becomes higher. The tendency of the value of the allowable slip ratio is the same when the vehicle 3 is climbing rapidly, but the estimated vehicle speed is low so that the difference between the case where the vehicle speed is low and the case where the vehicle speed is high is extremely small. In this case, the value of the allowable slip ratio is set small.

  The slip ratio selection unit 6503 sets the rapid climb determination flag to “1” when the estimated tilt angle detected by the climb angle estimation unit 63 is equal to or greater than a predetermined tilt angle and the vehicle 3 is climbing rapidly. Then, the value of the allowable slip ratio stored in the steep climb allowable slip ratio storage unit 6504 is selected and output to the target wheel speed calculation unit 6505. When the estimated inclination angle detected by the uphill angle estimation unit 63 is less than the predetermined inclination angle and the vehicle 3 is not making a steep uphill, the slip ratio selection unit 6503 sets the steep uphill determination flag to “0”. Then, the allowable slip ratio calculated by the allowable slip ratio calculation unit is selected and output to the target wheel speed calculation unit 6505.

When the target wheel speed calculation unit 6505 switches between a case where it is determined that the vehicle 3 is climbing rapidly and a case where it is determined that the vehicle 3 is not climbing rapidly, the target wheel speed calculation unit 6505 A target wheel speed is calculated based on the output allowable slip ratio and the wheel speed . By this calculated value, occurrence of hunting and shock is suppressed. This calculated value is output to the rate limit setting unit 6506 at the time of sudden climb determination determination switching.

  When the change rate of the calculated value of the target wheel speed calculating unit 6505 is out of a predetermined range, the rate limit setting unit 6506 at the time of sudden climb determination switching changes the calculated value of the target wheel speed calculating unit 6505 to the calculated value. It is converted into a predetermined value such that the rate of change is within a predetermined range, and is output to the target wheel speed lower limit setting unit 6507. This suppresses a rapid change in the change rate. When the rate of change of the calculated value of the target wheel speed calculating unit 6505 is within a predetermined range, the rapid climb determination determination rate limit setting unit 6506 directly uses the calculated value of the target wheel speed calculating unit 6505 as the target wheel speed. Output to lower limit setting unit 6507.

  The target wheel speed lower limit limit setting unit 6507 is configured to output the value output from the rate limit 6506 setting unit at the time of steep climb determination and the inclination of the vehicle 3 detected by the climb angle estimation unit 63 or the road surface on which the vehicle 3 is positioned ( Based on the value of the estimated inclination angle), the speed of the target front wheel Wf (RWf, LWf), that is, the lower limit value of the target wheel speed is set and output to the wheel speed difference calculation unit 6508. Thereby, it is suppressed that the restriction | limiting of the output torque becomes excessive by setting a target wheel speed low. This is because the acceleration that can be generated varies depending on the inclination angle of the road surface, and accordingly, the lower limit value of the target wheel speed needs to be variable. Specifically, as shown in FIG. 8, conventionally, the lower limit value (minimum wheel speed) of the target wheel speed is constant. In the present embodiment, the target wheel speed is increased as the inclination angle increases. When the lower limit value (minimum wheel speed) of the vehicle becomes small and reaches a predetermined value, it is set to a constant value. FIG. 8 is a graph showing the relationship between the tilt angle and the minimum wheel speed in a vehicle equipped with the vehicle drive system according to the embodiment.

  The front wheel speed low value selection unit 6509 selects a lower value of the speeds of the front wheels Wf (RWf, LWf) and outputs the selected value to the wheel speed difference calculation unit 6508. The wheel speed difference calculation unit 6508 calculates the difference between the actual wheel speed and the target wheel speed from the lower limit value of the target wheel speed from the target wheel speed lower limit setting unit 6507 and the value from the front wheel speed low value selection unit 6509. Is calculated. Then, the wheel speed difference calculation unit 6508 outputs the calculated value to the I-term D-term calculation unit 6511 when the vehicle 3 is steeply climbing, and the vehicle 3 is not climbing uphill or is flat. When the vehicle is traveling on the road surface, the calculated value is output to the P-term calculation unit 6512.

  The I-term D-term calculation unit 6511 calculates the I-term and D-term of the PID control for the value output from the wheel speed difference calculation unit 6508 and outputs the result to the down amount limit processing unit 6513. As a result, it is possible to determine the start and end timings of the control in which the torque is controlled by the traction control, and the responsiveness of the traction control is enhanced during a steep climb. That is, when the vehicle 3 starts a steep climb, it becomes possible to immediately apply the traction control. When the vehicle 3 completes the steep climb, the control of the torque limitation by the traction control can be terminated immediately. It becomes possible. In addition, it is possible to perform control to change the torque limit with high responsiveness in accordance with a change in the slip condition of the front wheels Wf (RWf, LWf) during the steep climb of the vehicle 2.

  The P term calculation unit 6512 is a value output from the wheel speed difference calculation unit 6508 based on the value of the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located (estimated inclination angle) detected by the uphill angle estimation unit 63. Is calculated for the P term of the PID control and output to the down amount limit processing unit 6513. For this reason, in this embodiment, as shown in FIG. 10, the P gain is configured to increase as the tilt angle increases. FIG. 10 is a graph showing the relationship between the tilt angle and the P gain in a vehicle equipped with the vehicle drive system according to the embodiment.

  The down amount limit processing unit 6513 limits the value of the torque limited by the traction control so that the limit value is not too large, and outputs it to the rate limit setting unit 6514. Thereby, it is prevented that the engine stall occurs due to the limit value of the torque value limited by the traction control being too large.

  When the rate of change of the value from the down amount limit processing unit 6513 is out of the predetermined range, the rate limit setting unit 6514 uses the value from the down amount limit processing unit 6513 as the rate of change of the value. The value is converted to a predetermined value that falls within the range, and is output to the FrTCS 62 as a torque value limited by the traction control (a value of the torque to be reduced) to control the traction control. Thereby, a rapid change in the rate of change is suppressed, and the occurrence of hunting or shock is suppressed. When the rate of change of the value from the down amount limit processing unit 6513 is within a predetermined range, the rate limit setting unit 6514 limits the value from the down amount limit processing unit 6513 as it is under the control of the traction control. The torque value (the torque value to be reduced) is output to the FrTCS 62 to perform traction control.

  The above operation will be described below with reference to a time chart along with the passage of time. FIG. 7 is a time chart showing a state at the time of steep climbing of a vehicle equipped with the vehicle drive system according to the above embodiment.

  When the vehicle 3 starts to climb and the value of the estimated climb angle becomes equal to or greater than a predetermined value at time T1, and the sudden climb control unit 65 determines that the vehicle 3 is climbing rapidly, the rapid climb determination flag is “1”. It becomes the state of. Then, at time T2 after a predetermined time has elapsed, the target torque value for driving the front wheels Wf (RWf, LWf) is increased. At this time, as shown by a one-dot chain line in FIG. 7, the target torque value is increased to a predetermined torque value at a constant increase rate and thereafter becomes a constant value. However, at time T3, the slip determination flag is “ When the traction control control is set to “1” and the target torque value is used as a reference, the target torque value limited (torque value reduced) as shown by the dotted line is actually output. Is done. That is, after the elapse of time T3, the wheel speed of the front wheel Wf (RWf, LWf) indicated by the broken line is a value that exceeds the wheel speed of the target front wheel Wf (RWf, LWf) temporarily based on the target slip ratio indicated by the dotted line. However, at this time, the target torque value is temporarily greatly reduced by the control of the traction control. As a result, the slip of the front wheel Wf (RWf, LWf) that has temporarily increased is suppressed to be small, and converges to the wheel speed of the target front wheel Wf (RWf, LWf) based on the target slip ratio.

  Even after the time T4 has elapsed, the target torque value is limited and reduced by an appropriate value under the control of the traction control. Thereby, the wheel speed of the front wheel Wf (RWf, LWf) gradually becomes smaller than the wheel speed of the target front wheel Wf (RWf, LWf) based on the target slip ratio. Then, when the vehicle 3 finishes the climbing and reaches a flat road surface at the time T5, the rapid climbing determination flag becomes “0”. Accordingly, the slip determination flag is set to “0”, and the traction control is not performed. Thereafter, at time T6, the wheel speeds of the front wheels Wf (RWf, LWf) and the wheel speeds of the rear wheels Wr (RWr, LWr) become constant values and coincide with each other.

According to this embodiment, the following effects are produced.
In the present embodiment, the climbing angle estimation unit 63 of the ECU causes the vehicle 3 to climb rapidly on the basis of the inclination of the vehicle 3 detected while the vehicle 3 is traveling or the inclination of the road surface on which the vehicle 3 is located (estimated inclination angle). Traction control is performed to detect the presence of the vehicle and to limit the torque for driving the first drive wheel of the vehicle.
For this reason, it is possible to suppress a high value torque from being applied to the front wheels Wf (RWf, LWf) during a steep climb, and to prevent the front wheels Wf (RWf, LWf) from slipping during a steep climb. It becomes possible.

In addition, the steep climbing control unit determines the difference between the actual wheel speed of the front wheel Wf (RWf, LWf) and the target wheel speed of the front wheel Wf (RWf, LWf) according to the terms I and D by PID control. The start and end timings of control for limiting the torque are determined by calculation.
For this reason, when the vehicle 3 starts to climb rapidly, traction control can be applied immediately, and responsiveness can be improved. As a result, the slip of the front wheels Wf (RWf, LWf) can be converged immediately after starting the steep climb.

Further, the steep climbing control unit sets a lower limit value of the target wheel speed of the front wheels Wf (RWf, LWf) according to the inclination angle of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located.
For this reason, it is possible to cope with the fact that the acceleration that can be generated varies depending on the inclination angle of the road surface, and it is possible to suppress excessive torque limitation by traction control.

Further, the steep climbing control unit 65 changes the value of the allowable slip ratio of the front wheels Wf (RWf, LWf) with respect to the road surface in accordance with the inclination angle of the vehicle 3 or the inclination angle of the road surface on which the vehicle 3 is located. Control is performed to limit the torque applied to Wf (RWf, LWf).
For this reason, when the vehicle 3 starts to climb rapidly and the front wheels Wf (RWf, LWf) begin to slip, it is possible to immediately limit the torque by controlling the traction control.

[Second Embodiment]
The vehicle according to the second embodiment of the present invention differs from the vehicle 3 according to the first embodiment only in the detection of the vehicle speed. FIG. 11 is a time chart showing the relationship between the wheel speed and the rotational speed of the electric motor when the vehicle equipped with the vehicle drive system according to the second embodiment of the present invention is in a climbing state.

  After time T3 shown in FIG. 5, the wheel speed increases, and at time T31 (see FIG. 11), which is the time between time T3 and time T4 in FIG. 5, the wheel speed is equal to or higher than a predetermined value (predetermined vehicle speed). Thus, when the vehicle exceeds the predetermined vehicle speed, the brake solenoid that was in the ON state before the time T31 is turned OFF and is in a ring-free state. Thereby, the drive by the electric motors 2A and 2B with respect to the wheels is interrupted. For this reason, the rotation speed of the motors 2A and 2B and the wheel speed, which were in a proportional relationship before time T31, are no longer in a proportional relationship. Here, the predetermined value of the wheel speed means, for example, the maximum number of rotations of the electric motors 2A and 2B.

  At this time, the uphill angle estimation unit 63 detects the estimated inclination angle based on the vehicle speed based on the detection value from the resolver 94 before the time T31. However, after the time T31, the uphill angle estimation unit 63 detects the estimated inclination angle from the wheel speed sensor 91. The estimated inclination angle is detected based on the vehicle speed based on the detection signal. As a result, the accuracy is lower than the vehicle speed based on the detection value from the resolver 94. However, even when the wheel speed becomes equal to or higher than a predetermined value after time T31, the uphill angle estimation unit 63 determines the approximate vehicle speed value. Continue to detect.

According to this embodiment, the following effects are produced.
The ECU 6 cuts off the driving of the wheels (rear wheels RWr, LWr) by the electric motors 2A, 2B when the vehicle 3 is at a predetermined vehicle speed or higher, and the uphill angle estimation unit 63 determines whether the vehicle 3 is at a predetermined vehicle speed or higher. Regardless, control is performed to detect the vehicle speed while the vehicle 3 is traveling.
When the front wheels Wf (RWf, LWf) or the rear wheels Wr (RWr, LWr) are driven by the electric motors 2A, 2B, that is, the separation mechanism is turned on by the one-way clutch, and the electric motors 2A, 2B Is transmitted to the rear wheels RWr and LWr, the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located (estimated inclination angle) is detected based on the rotational speeds of the electric motors 2A and 2B. The front wheels Wf (RWf, LWf) and the rear wheels Wr (RWr, LWr) are disconnected from the electric motors 2A, 2B, and the front wheels Wf (RWf, LWf) and the rear wheels Wr (RWr, LWr) by the electric motors 2A, 2B are separated. ) Is cut off, that is, when the separating mechanism is turned off by the one-way clutch (OWC free) and the power of the motors 2A and 2B is not transmitted to the rear wheels RWr and LWr, the rear wheel Wr ( Based on the number of rotations (RWr, LWr), the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located (estimated inclination angle) is detected.

  Therefore, when the vehicle 3 travels at a high speed and the rotational speed (wheel speed) of the rear wheels Wr (RWr, LWr) is higher than the maximum rotational speed of the electric motors 2A, 2B, the front wheels Wf (RWf, LWf) and rear wheels Wr (RWr, LWr) are disconnected from the electric motors 2A, 2B. Even in such a case, the inclination of the vehicle 3 or the inclination of the road surface on which the vehicle 3 is located (Estimated tilt angle) can be detected. For this reason, it is possible to detect the vehicle speed regardless of the vehicle speed. As a result, even when the vehicle speed is higher than the maximum rotation speed of the electric motors 2A and 2B, by continuously detecting the vehicle speed, the calculation speed of the estimated inclination angle when the vehicle speed suddenly becomes low is obtained. It becomes possible to improve.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the present embodiment, detection values from the wheel speed sensor 91 and the resolver 94 are used to obtain an estimated inclination angle during traveling, but the present invention is not limited to this. The estimated inclination angle during traveling may be obtained based on the correlation amount correlated with the vehicle speed.
Further, although the average value of the detection values detected from the electric motors 2A and 2B is used as the detection value from the resolver 94 input in the uphill angle estimation unit 63, it is not limited to this. Similarly, when the electric motors 2A, 2B and the rear wheels RWr, LWr are disconnected, the value of the wheel speed (rear wheel Wr (RWr, LWr) rotation speed) from the wheel speed sensor 91 is used as a detection signal for climbing An average value of the left and right wheel speeds is used as the wheel speed value that is input to the angle estimation unit 63, but is not limited thereto.
In addition, the first driving wheel is configured by the front wheel Wf (RWf, LWf) and the second driving wheel is configured by the rear wheel Wr (RWr, LWr), but is not limited thereto.
Moreover, in the said embodiment, although the 2nd drive device 2 on the rear-wheel side was made into the 2 motor system which comprises two electric motors 2A and 2B, a 1 motor system may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... 1st drive device 2 ... 2nd drive device 2A, 2B ... Electric motor 3 ... Vehicle 6 ... ECU (control apparatus)
62 ... FrTCS (torque controller)
63 ... Climbing angle estimation unit 65 ... Steep climbing control unit Wf (RWf, LWf) ... Front wheel Wr (RWr, LWr) ... Rear wheel

Claims (3)

A first drive device that drives a first drive wheel that is one of a front wheel and a rear wheel of the vehicle;
A second drive device for driving a second drive wheel which is either the front wheel or the rear wheel of the vehicle;
A vehicle drive system comprising: a control device that controls the first drive device and the second drive device and controls the drive states of the first drive wheel and the second drive wheel;
The control device includes:
An inclination of the vehicle or an inclination of a road surface on which the vehicle is located is detected based on a correlation amount correlated with a vehicle speed while the vehicle is running, and an inclination angle of the vehicle or an inclination angle of the road surface on which the vehicle is located is determined. , when it is detected that is greater than a predetermined angle, it has a torque limiting unit that performs control for limiting the torque for driving the first drive wheels of the vehicle,
The torque limiting unit is a vehicle drive system that sets a lower limit value of a target wheel speed of the first drive wheel to be smaller as an inclination angle of the vehicle or a road surface on which the vehicle is located increases .   The torque limiting unit calculates the torque by calculating the I term and the D term by PID control with respect to the wheel speed difference between the actual wheel speed of the first driving wheel and the target wheel speed of the first driving wheel. The vehicle drive system according to claim 1, wherein a start timing and an end timing of control to be limited are determined. The torque limiting unit limits the torque by setting a value of an allowable slip ratio of the first driving wheel with respect to a road surface to be smaller as an inclination angle of the vehicle or a road surface on which the vehicle is located increases . The vehicle drive system of Claim 1 or Claim 2 which performs control.

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