JP2017034907A - Vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a vehicle smoothly travel down even if the vehicle is stopped at an abrupt ramp such an off-road.SOLUTION: When a brake ECU detects a horizontal slide of a wheel at an upper side of a ramp when a vehicle stop state (state that the rotation of left and right front/rear wheels is stopped) is detected on the ramp (S11 to S14; YES), the brake ECU releases brake forces with respect to left and right single-wheels of the rear wheels so that a rotational motion of a vehicle body is generated in a direction opposite to a direction in which the vehicle body rotates by the horizontal slide, and imparts a drive force to a reward direction (S15 to S19). By this constitution, a vehicle can be oriented to a proper direction while a driver keeps to pedal a brake pedal.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vehicle control device applied to a vehicle that can drive and control front wheels and rear wheels independently of each other.

  Conventionally, a vehicle capable of driving and controlling front wheels and rear wheels independently of each other, for example, as proposed in Patent Document 1, four-wheel drive in which front wheels are driven by an engine and rear wheels are driven by an electric motor. A type of vehicle is known. When the vehicle proposed in Patent Document 1 detects rollback (the vehicle slides backward when driving force is generated in the forward direction), the running resistance acting on the vehicle from the outside is detected. A value (a force acting in a direction opposite to the direction in which the vehicle driving force is generated) is calculated, a front wheel slip is detected based on the running resistance value, and a rear wheel driving force is controlled based on the slip.

JP 2010-149697 A

  Even such a four-wheel drive vehicle may not be able to climb up the slope when the slope angle is large and the road surface frictional resistance is small during off-road climbing. It is difficult for the driver to determine in advance whether or not to climb the hill. For this reason, the following problems occur during off-road climbing.

  As shown in FIG. 3, when the vehicle 100 is climbing an off-road slope, each wheel is rotated by the driving force applied to the wheels WFL, WFR, WRL, and WRR. The force which corrects can be generated. If the driver determines that it is not possible to climb the hill, and depresses the brake pedal to stop the vehicle, the wheels WFL, WFR, WRL, and WRR are locked. As a result, a force for changing the direction of the vehicle body cannot be generated even when the steering operation is performed.

When the vehicle is stopped on an uphill, as shown in FIG. 4, a part of the load in the gravity direction acting on the front wheel WF (WFL, WFR) and the rear wheel WR (WRL, WRR) moves to the rear wheel WR side. doing. In this example, as shown in the following equation, the load acting on the front wheel WF side is reduced by ΔW and the load acting on the rear wheel WR side is increased by ΔW as compared to the case where the vehicle 100 is stopped horizontally.
ΔW = m × G × (H / L) × sin α
Here, m is the vehicle weight, G is the gravitational acceleration, H is the height of the center of gravity, L is the wheel base, and α is the vehicle tilt angle.

  For this reason, when the vehicle is stopped on an uphill, the frictional force on the road surface of the front wheel WF is smaller than the frictional force on the road surface of the rear wheel WR. Therefore, in this case, the front wheel WF is more slippery than the rear wheel WR. Therefore, as shown in FIG. 5, when the vehicle 100 stops obliquely with respect to the climbing slope, the front wheel WF slides on the slope. At this time, if the wheels WFL, WFR, WRL, and WRR are locked by the brake braking force, the direction of the vehicle body cannot be controlled even if the driver performs a steering operation. For this reason, the vehicle body may rotate about the intermediate position P between the left and right rear wheels WRL and WRR, become transverse to the tilt direction, and become unstable.

  The driver has advanced driving technology, adjusts the brake operation so that the wheels WFL, WFR, WRL, WRR do not lock, generates the appropriate driving force by the accelerator operation, and steers in the appropriate direction If you do, you can descend from the middle of the off-road climbing slope. However, such a driving operation is difficult for a normal driver.

  The present invention has been made in order to solve the above-described problem, and even when the vehicle stops on a steep slope such as off-road, the longitudinal axis of the vehicle is prevented from greatly deviating from the inclination direction of the slope. It is an object of the present invention to provide a vehicle control device that can be used.

In order to achieve the above object, the features of the present invention are:
A vehicle control device applied to a four-wheel drive vehicle capable of driving and controlling the rear wheels independently of the front wheels, and capable of braking control of at least the rear wheels independently of the left and right sides,
Stopping state detection means (40, 43, 44, 46, S11, S12) detects a stopping state on a slope where the rotation of the left and right front and rear wheels is stopped by the brake operation and the front and rear direction of the vehicle is not horizontal. , S13) and
Upper wheel slip detection means (40, 45, S14) for detecting a side slip of the wheel on the upper side of the slope when the stop state is detected;
When a side slip of the wheel on the upper side of the slope is detected, the left and right side wheels of the rear wheel are caused to generate a rotational movement of the vehicle body in a direction opposite to a direction in which the vehicle body rotates due to the side slip. And rear wheel control means (30, 40, S15 to S20) for releasing the braking force and applying the driving force in the reverse direction.

  The vehicle control device of the present invention is applied to a four-wheel drive vehicle in which the rear wheels can be driven and controlled independently of the front wheels, and at least the rear wheels can be braked independently of the left and right. The vehicle control device includes a stop state detection means, an upper wheel skid detection means, and a rear wheel control means. The stop state detecting means detects a stop state on a slope where the rotation of the left and right front and rear wheels is stopped by a brake operation and the front and rear direction of the vehicle does not face the horizontal direction. When the vehicle is stopped on a slope such as off-road, the wheels on the upper side of the slope tend to skid sideways. In that case, since the left and right front and rear wheels are locked by the brake operation, it is difficult to control the direction of the vehicle body even if the driver performs the steering operation.

  Therefore, the upper wheel skid detection means detects the skid of the wheel on the upper side of the slope when the stop state on the slope is detected. The rear wheel control means controls the left and right side wheels of the rear wheel so that when the side slip of the wheel on the upper side of the slope road is detected, the side wheel causes a rotational movement of the vehicle body in a direction opposite to the direction in which the vehicle body rotates. Thus, the braking force is released and the driving force is applied in the reverse direction. In this case, applying the driving force means that the wheel is finally driven to rotate in the reverse direction. For example, the braking force and the driving force applied to the driving shaft of the wheel In the relationship, the driving force may exceed the braking force. For example, even in a vehicle that cannot drive and control the left and right wheels of the rear wheel independently, the braking force is released for the left and right wheels on the left and right wheels with the drive force in the reverse direction applied to the drive shafts of the left and right wheels. By doing so, only the one side wheel can be driven in the reverse direction (rotated in the reverse direction). Of course, this is not necessary if the vehicle can drive and control the left and right rear wheels independently.

  By driving the rear wheels in the backward direction of the left and right side wheels, it is possible to cause the vehicle body to generate a rotational motion in a direction opposite to the direction in which the vehicle body rotates due to skidding. That is, it is possible to apply a force to the vehicle body so as to direct the vehicle body in the original direction (that is, the direction substantially coincident with the inclination direction of the slope and / or the direction before the occurrence of skidding). Thereby, even if the driver does not have advanced driving skills, the longitudinal axis of the vehicle can be prevented from greatly deviating from the inclination direction of the slope. That is, it is possible to suppress the vehicle body from rotating in the descending direction due to the skidding of the wheels on the slope. Therefore, according to the present invention, it is possible to satisfactorily get off a slope such as an off-road where the vehicle easily slips.

A feature of one aspect of the present invention is that
The stop state detection means is configured to detect the stop state on the uphill of the vehicle when rotation of the left and right front and rear wheels is stopped by a brake operation,
The upper wheel side slip detection means is configured to detect a side slip of the front wheel when the stopping state on the uphill is detected.
The rear wheel control means releases the braking force and drives the vehicle in the reverse direction with respect to the left and right rear wheels that are opposite to the direction in which the vehicle body rotates due to the side slip when the side slip of the front wheel is detected. It is configured to give power.

  For example, if the driver determines that it is not possible to climb on an uphill road such as off-road and steps on the brake pedal to stop the vehicle, the front wheels may skid and the vehicle body may rotate on the slope. In order to solve such a problem, in one aspect of the present invention, the stop state detection means detects the stop state on the uphill of the vehicle when rotation of the left and right front and rear wheels is stopped by a brake operation. It is configured. The upper wheel skid detecting means detects the skid of the front wheel when the stop state on the uphill is detected. The rear wheel control means releases the braking force and applies the driving force in the reverse direction to the left and right rear wheels, which are opposite to the direction in which the vehicle body rotates due to the side slip, when the front wheel side slip is detected. To do.

  Therefore, for example, when the vehicle body rotates in the right direction due to the side slip of the front wheel, the braking force of the left rear wheel is released while the braking force of the left and right front wheels and the right rear wheel is maintained, and the left rear wheel moves backward. Driven by. Conversely, when the vehicle body rotates leftward due to the side slip of the front wheel, the braking force of the right rear wheel is released while the braking force of the left and right front wheels and the left rear wheel is maintained, and the right rear wheel moves backward. Driven by.

  As a result, the vehicle body can generate a rotational movement in the opposite direction to the direction in which the vehicle body rotates due to skidding, and the vehicle's front and rear axes are inclined in the slope direction even if the driver does not have advanced driving skills. It can be prevented from greatly deviating from.

A feature of one aspect of the present invention is that
The stop state detection means is configured to detect the stop state on the downhill of the vehicle when rotation of the left and right front and rear wheels is stopped by a brake operation,
The upper wheel side slip detecting means is configured to detect a side slip of the rear wheel when the stop state on the downhill is detected,
The rear wheel control means releases the braking force and drives the vehicle in the reverse direction with respect to the left and right rear wheels that are in the same direction as the vehicle body rotates due to the side slip when the side slip of the rear wheel is detected. It is configured to give power.

  For example, if the vehicle needs to be stopped on the way downhill such as off-road, and the driver steps on the brake pedal to stop the vehicle, the rear wheel may skid and the vehicle body may rotate on the slope. In order to solve such a problem, in one aspect of the present invention, the stop state detection means detects the stop state on the downhill of the vehicle in which the rotation of the left and right front and rear wheels is stopped by a brake operation. It is configured. The upper wheel skid detecting means detects the skid of the rear wheel when the stop state on the downhill is detected. The rear wheel control means releases the braking force and applies the driving force in the backward direction to the left and right rear wheels that are in the same direction as the direction of rotation of the vehicle body due to the side slip when a side slip of the rear wheel is detected. To do.

  Therefore, for example, when the vehicle body rotates leftward due to a side slip of the rear wheel, the braking force of the left rear wheel is released and the left rear wheel moves backward while the braking force of the left and right front wheels and the right rear wheel is maintained. Driven in the direction. Conversely, when the vehicle body rotates in the right direction due to the side slip of the front wheel, the braking force of the right rear wheel is released while the braking force of the left and right front wheels and the left rear wheel is maintained, and the right rear wheel moves backward. Driven by.

  As a result, the vehicle body can generate a rotational movement in the opposite direction to the direction in which the vehicle body rotates due to skidding, and the vehicle's front and rear axes are inclined in the slope direction even if the driver does not have advanced driving skills. It can be prevented from greatly deviating from.

A feature of one aspect of the present invention is that
A lateral acceleration acquisition means (45) for acquiring lateral acceleration (Gy) which is a vehicle lateral direction component of gravitational acceleration;
The upper wheel skid detection means includes
Based on the change of the lateral acceleration acquired by the lateral acceleration acquisition means, it is configured to detect the side slip of the wheel (S14),
The rear wheel control means includes
When the magnitude of the lateral acceleration acquired by the lateral acceleration acquisition means reaches a value equal to or less than a threshold value (Gyref), the release of the braking force and the application of the driving force to the left and right rear wheels are terminated (S20). ) Is configured as follows.

  In one aspect of the present invention, the lateral acceleration acquisition means acquires a lateral acceleration that is a vehicle lateral component of gravitational acceleration. The upper wheel skid detection means detects a wheel skid based on a change in the lateral acceleration acquired by the lateral acceleration acquisition means. For example, the upper wheel side slip detecting means detects a wheel side slip based on a lateral acceleration change amount which is a change amount of the lateral acceleration per unit time. Therefore, it is possible to satisfactorily detect the side slip of the wheel on which the vehicle body rotates on the slope.

  The rear wheel control means finishes releasing the braking force and applying the driving force to the rear wheels on the left and right sides when the magnitude of the lateral acceleration obtained by the lateral acceleration obtaining means reaches a value equal to or less than the threshold value. This threshold value is the magnitude of the lateral acceleration when the rotational movement of the vehicle body generated by the driving force of the rear wheels is stopped, and may be set to, for example, zero or a value near zero. Thereby, the vehicle body can be rotated to a position where the vehicle body is properly oriented on the slope.

A feature of one aspect of the present invention is that
Direction acquisition means (45) for acquiring direction information indicating a direction in which a wheel on an upper side of the slope slides sideways;
Slope acquisition means (46) for acquiring slope information indicating whether the slope is an uphill or a downhill when the stop state is detected, and
The rear wheel control means includes
Based on the direction information and the slope information, the left and right side wheels of the rear wheel that release the braking force and apply the driving force in the reverse direction are specified (S15).

  According to one aspect of the present invention, the direction acquisition means acquires direction information indicating the direction in which the wheel on the upper side of the slope slides. For example, the direction in which the wheels slide sideways can be grasped based on the direction of the vehicle lateral component of the gravitational acceleration, the direction of the lateral acceleration of the vehicle, the direction of the yaw rate of the vehicle, and the like. The slope acquisition means acquires slope information indicating whether the slope when the stop state is detected is an uphill or a downhill. The rear wheel control means specifies the left and right side wheels of the rear wheel that releases the braking force and applies the driving force in the reverse direction based on the direction information and the slope information (specifies one of the left and right rear wheels). ). Therefore, even when the stop state is detected on the uphill or the stop state is detected on the downhill, the vehicle body can be properly rotated on the slope.

  In the above description, in order to assist the understanding of the invention, the reference numerals used in the embodiments are attached to the constituent elements of the invention corresponding to the embodiments in parentheses. It is not limited to the embodiment defined by.

It is a schematic system block diagram of the vehicle control apparatus of this embodiment. It is a flowchart showing an off-road slope vehicle control routine. It is explanatory drawing showing the state of the vehicle at the time of climbing. It is explanatory drawing showing the change of the load of the front-and-rear wheel in the uphill. It is explanatory drawing showing the state which a vehicle rotates by the skid of a front wheel in the uphill. It is explanatory drawing showing the state which a vehicle rotates by the skid of a rear wheel in a downhill. It is explanatory drawing showing the principle which orient | assigns a vehicle body to the original direction when the side slip of the front wheel generate | occur | produced on the uphill. It is explanatory drawing showing the principle which orient | assigns a vehicle body to the original direction when the side slip of a rear wheel generate | occur | produced in the downhill. It is explanatory drawing showing the vehicle left-right direction component (lateral acceleration Gy) of gravity acceleration G. FIG. It is explanatory drawing showing the matrix which sets a control object wheel from the lateral acceleration Gy and the inclination direction. It is a schematic system block diagram of the vehicle control apparatus of a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic system configuration of the vehicle control device of the present embodiment.

  A vehicle 1 including the vehicle control device of the present embodiment is a four-wheel drive hybrid vehicle, and includes an engine 11 and a front motor 12 that drive a left front wheel WFL and a right front wheel WFR, a left rear wheel WRL, and a right rear wheel. A hybrid system 10 having a rear motor 13 for driving WRR is provided. Hereinafter, the left front wheel WFL and the right front wheel WFR are referred to as a front wheel WF, and the left rear wheel WRL and the right rear wheel WRR are referred to as a rear wheel WR. Further, when there is no need to distinguish between the front wheel WF and the rear wheel WR, they are referred to as wheels W. The vehicle 1 is a general front-wheel steered vehicle having the front wheels WF as steered wheels, but illustration and description of the steered mechanism are omitted.

  In the hybrid system 10, the output shaft of the engine 11 and the output shaft of the front motor 12 are connected to the input shaft of a planetary gear 14 (including a power distribution planetary gear and a reduction planetary gear). The rotation of the output shaft of the planetary gear 14 is transmitted to the left and right front wheel axles 16L and 16R via the differential gear 15, whereby the left and right front wheels WFL and WFR are rotationally driven. In addition, since the vehicle control apparatus of this embodiment does not have the characteristic in the hybrid system 10, in this specification, only the simple description is given about the hybrid system 10. FIG. For example, as described in JP 2013-177026 A, the front motor 12 is connected to a power distribution planetary gear and is connected to a reduction planetary gear and a first motor generator that generates power mainly by rotation of the engine 11. And a second motor generator for applying a driving force to the front wheels WF by power running.

  The driving force of the rear motor 13 is transmitted to the left and right rear wheel axles 18L and 18R via a differential gear 17 (including a reduction gear), whereby the left and right rear wheels WRL and WRR are rotationally driven.

  The front motor 12 and the rear motor 13 are connected to the inverter 20. The inverter 20 is connected to the battery 22 via the DC / DC converter 21. The inverter 20 converts DC power supplied from the battery 22 (DC power whose voltage is adjusted by the DC / DC converter 21) into three-phase AC, and the converted AC power is independent of the front motor 12 and the rear motor 13. And supply. Therefore, the inverter 20 includes an inverter circuit connected to the front motor 12 and an inverter circuit connected to the rear motor 13 independently.

  The front motor 12 and the rear motor 13 are configured to be capable of being driven independently of forward rotation in the forward direction of the vehicle and reverse rotation in the reverse direction of the vehicle by energization control of the inverter 20. The inverter 20 also has a function of converting regenerative power generated by the front motor 12 and the rear motor 13 into direct current and charging the battery 22 via the DC / DC converter 21.

  The operations of the engine 11, the front motor 12, and the rear motor 13 are controlled by the drive ECU 30. The drive ECU 30 is an electronic control device including a microcomputer as a main part. Note that ECU is an abbreviation for Electric Control Unit. In the present specification, the microcomputer includes a CPU and a storage device such as a ROM and a RAM, and the CPU realizes various functions by executing instructions (programs) stored in the ROM.

  The drive ECU 30 inputs a detection signal of an accelerator sensor 31 that detects an accelerator operation amount, calculates a driver request driving force according to the accelerator operation amount, and calculates the driver request driving force between the front wheel WF side and the rear wheel WR side. The engine 11, the front motor 12 and the rear motor 13 are controlled so as to transmit the front wheel target driving force and the rear wheel target driving force distributed to the front wheel WF and the rear wheel WR, respectively. For example, the drive ECU 30 inputs detection signals output from various engine control sensors 32, and performs fuel injection control, ignition control, intake air amount control, and the like of the engine 11. Further, the drive ECU 30 inputs detection signals output from various motor control sensors 33, controls the operation of the inverter 20, and controls the energization of the front motor 12 and the rear motor 13.

  The vehicle 1 also includes friction brake mechanisms 41FL, 41FR, 41RL, and 41RR (referred to as friction brake mechanisms 41) provided on the left and right front and rear wheels WFL, WFR, WRL, and WRR, a brake actuator 42, and a brake ECU 40. ing. The friction brake mechanism 41 includes brake discs 41dFL, 41dFR, 41dRL, 41dRR (referred to as brake discs 41d) fixed to the wheels W, and brake calipers 41cFL, 41cFR, 41cRL, 41cRR (fixed to the vehicle body). And a brake cylinder is pressed against the brake disc 41d to generate a friction braking force by operating a wheel cylinder built in the brake caliper 41c by hydraulic pressure of hydraulic oil supplied from the brake actuator 42. .

  The brake actuator 42 is a known actuator that independently adjusts the hydraulic pressure supplied to the wheel cylinder built in the brake caliper 41c. The brake actuator 42, for example, provides a control hydraulic pressure that can be controlled independently of the brake pedal depression force in addition to a pedal hydraulic circuit that supplies hydraulic pressure to the wheel cylinder from a master cylinder that pressurizes hydraulic oil by the depression force of the brake pedal. Is equipped with a control hydraulic circuit that is supplied independently. The control hydraulic circuit has a booster pump and an accumulator to generate a high-pressure hydraulic pressure, adjusts the hydraulic pressure output from the power hydraulic pressure generator, and supplies the hydraulic pressure controlled to the target hydraulic pressure for each wheel cylinder. And a hydraulic pressure sensor for detecting the hydraulic pressure of each wheel cylinder (the elements constituting the brake actuator 42 are not shown).

  The brake ECU 40 is an electronic control device including a microcomputer as a main part, and is connected to the brake actuator 42 to control the operation of the brake actuator 42. The brake ECU 40 is connected to the drive ECU 30 via a CAN (Controller Area Network) (not shown) so as to be able to transmit and receive each other. The brake ECU 40 receives a detection signal from the brake sensor 43 that detects the brake operation amount, calculates a driver required braking force corresponding to the brake operation amount, and calculates the driver required braking force according to a preset distribution characteristic. The braking force and the requested regenerative braking force are distributed, and a regenerative braking request command representing the requested regenerative braking force is transmitted to the drive ECU 30. The drive ECU 30 generates a regenerative braking force by the front motor 12 and the rear motor 13 based on the required regenerative braking force, and transmits the actually generated regenerative braking force to the brake ECU 40. The brake ECU 40 corrects the required friction braking force with a difference value between the required regenerative braking force and the actual regenerative braking force, and calculates each wheel required friction braking force obtained by distributing the corrected required friction braking force to the four wheels. The brake ECU 40 controls the hydraulic pressure of each wheel cylinder so that each friction brake mechanism 41 generates each wheel required friction braking force by controlling energization of a linear control valve provided in the brake actuator 42. Thus, the brake ECU 40 can independently control the braking force of the left and right front and rear wheels 10.

  Also, a total of four wheel speed sensors 44 that detect the wheel speed of each wheel W are connected to the brake ECU 40. The brake ECU 40 calculates the vehicle speed V based on the wheel speed Vw of each wheel W detected by the wheel speed sensor 44, and transmits information representing the vehicle speed V to the drive ECU 30 via the CAN at a predetermined short cycle.

  The brake ECU 40 is connected to the lateral acceleration sensor 45. The lateral acceleration sensor 45 detects the vehicle left-right direction component of the gravitational acceleration G. The vehicle lateral direction component of the gravitational acceleration G detected by the lateral acceleration sensor 45 is referred to as a lateral acceleration Gy. The lateral acceleration Gy is identified by the sign (positive or negative) in the direction of the lateral acceleration (information indicating whether the gravitational acceleration is working in the left direction or the right direction of the vehicle). For example, as shown in FIG. 9A, when the longitudinal axis of the vehicle 1 is oriented in the slope direction of the slope, the magnitude | Gy | of the lateral acceleration Gy becomes zero, but the longitudinal axis of the vehicle Is not directed in the slope direction of the slope, the magnitude | Gy | of the lateral acceleration Gy is a value larger than zero. Moreover, although mentioned later, the code | symbol of lateral acceleration Gy is used as information which judges the skid direction of the wheel W of the upper side of a slope.

Further, the brake ECU 40 is connected to the inclination sensor 46. For example, the inclination sensor 46 detects the vehicle longitudinal direction component Gx of the gravitational acceleration G using an acceleration sensor that detects acceleration in the longitudinal direction of the vehicle, and the vehicle is inclined in the longitudinal direction. The direction in which the vehicle is inclined (uphill or downhill) is determined. For example, when the vehicle is stopped on an uphill, the vehicle longitudinal component Gx acts on the rear of the vehicle, and when the vehicle is stopped on a downhill, the vehicle longitudinal component Gx acts on the front of the vehicle. Therefore, it can be determined that the vehicle is tilted in the front-rear direction based on the magnitude of the vehicle front-rear direction component Gx, and the vehicle is tilted based on the direction of the vehicle front-rear direction component Gx (forward or backward). The direction can be determined. The inclination angle α can also be detected by the following equation.
α = sin ⁻¹ (Gx / G)

  Next, off-road slope vehicle control will be described. As described above, when off-road climbing or the like, if the inclination angle is large and the road surface friction resistance is small, the vehicle may not be able to climb up the slope. If the driver determines that the climbing is impossible during the climbing and stops the vehicle obliquely with respect to the tilting direction of the climbing slope by the brake operation, the front wheel WF may skid on the road surface as shown in FIG. When the wheel W is locked, the direction of the vehicle body cannot be controlled even if the driver performs a steering operation. For this reason, the vehicle body rotates with the intermediate position P of the rear wheels WRL and WRR as a fulcrum, becomes transverse to the tilt direction, and becomes unstable.

  Further, even when off-road downhill, when the inclination angle is large and the road surface friction resistance is small, if the vehicle is stopped obliquely with respect to the downhill inclination direction by a braking operation in the middle of FIG. As shown in FIG. 3, the rear wheel WR may slide sideways on the road surface. In this case, the vehicle body rotates with the intermediate position Q between the front wheels WFL and WFR as a fulcrum, becomes transverse to the tilt direction, and becomes unstable.

  The off-road hill vehicle control prevents the vehicle body from being sideways with respect to the tilt direction so that the vehicle 1 can properly descend from the off-road hill even in such a situation that a side skid of the wheel is likely to occur. Control. FIG. 2 represents an off-road hill vehicle control routine. The brake ECU 40 repeatedly executes the off-road slope vehicle control routine at a predetermined short calculation cycle. The brake ECU 40 outputs a drive command to the drive ECU 30 during the off-road slope vehicle control routine, and also controls the driving force of the rear wheels WR. Accordingly, the off-road hill vehicle control is performed by the cooperation of the brake ECU 40 and the drive ECU 30. Therefore, the off-road slope vehicle control routine may be executed mainly by the drive ECU 30 instead of the brake ECU 40. The off-road hill vehicle control routine is executed, for example, when an off-road mode in which braking / driving force suitable for off-road driving is set is selected by an operation of an off-road selection switch (not shown) by a driver. It is good to be done.

  When the off-road slope vehicle control routine is activated, the brake ECU 40 reads the detection signal of the brake sensor 43 in step S11 and determines whether or not the brake pedal is depressed. Hereinafter, a state in which the brake pedal is depressed is referred to as brake on, and a state in which the brake pedal is not depressed is referred to as brake off. The brake ECU 40 once ends the off-road slope vehicle control routine when the brake is off.

  The brake ECU 40 repeatedly performs the determination process of step S11, and when the brake-on is detected, the brake ECU 40 determines whether the four wheels W are based on the wheel speed information detected by the four wheel speed sensors 44 in step S12. It is determined whether or not the wheel speeds Vw are all zero, that is, whether or not all the four wheels W are locked. If any one of the wheel speeds Vw of the four wheels is not zero, the brake ECU 40 once ends this routine.

  The brake ECU 40 repeats such processing, and when it is detected that the rotation of the four wheels W has been stopped by the brake pedal operation (S12: Yes), the detection signal detected by the inclination angle sensor 46 in step S13. Based on this, it is determined whether or not the vehicle exists on a slope where the front-rear direction of the vehicle does not face the horizontal direction. In this case, since all the four wheels W are in the locked state, it is determined whether or not the vehicle is stopped on a slope (hereinafter simply referred to as a slope) in which the front-rear direction of the vehicle does not face the horizontal direction. When it is determined that the vehicle is not stopped on the slope, the brake ECU 40 once ends this routine.

  The brake ECU 40 repeats such processing, and when it is detected that the vehicle is stopped on a slope (S13: Yes), in the subsequent step S14, based on the lateral acceleration Gy detected by the lateral acceleration sensor 45, A lateral acceleration change amount ΔGy, which is a change amount of the lateral acceleration Gy, is calculated to determine whether the lateral acceleration change amount ΔGy is not zero. For example, the brake ECU 40 reads the lateral acceleration Gy at a predetermined calculation cycle, and calculates the difference value between the lateral acceleration Gy read this time and the lateral acceleration Gy read one calculation cycle before as the lateral acceleration change amount ΔGy. Note that the average value of the detected value group of the latest n (> 1) lateral acceleration Gy and the average value of the new detected value group of n lateral accelerations Gy n times before the detected value group. The influence of instantaneous noise fluctuation may be reduced by calculating the difference value as the lateral acceleration change amount ΔGy. In step S14, instead of comparing the lateral acceleration change amount ΔGy with zero, for example, it is determined whether or not the magnitude (absolute value) of the lateral acceleration change amount ΔGy is equal to or greater than the control start threshold (> 0). May be.

  If the lateral acceleration change amount ΔGy is zero, the brake ECU 40 once ends this routine. As described above, the lateral acceleration sensor 45 detects the vehicle left-right direction component of the gravitational acceleration G. Therefore, for example, as shown in FIG. 5, when the vehicle 1 is stopped while climbing (the state where the four wheels W are locked), the front wheels WFL, WFR slide sideways, and the vehicle body rotates on the slope in the direction of the arrow. Then, the magnitude | size (absolute value) of the vehicle left-right direction component of gravitational acceleration changes to an increase direction. Or, for example, as shown in FIG. 6, when the vehicle 1 is stopped in the middle of a downhill (a state where the four wheels W are locked), the rear wheels WRL and WRR slide sideways, and the vehicle body moves on the slope in the direction of the arrow. When rotating, the magnitude (absolute value) of gravitational acceleration changes in the vehicle left-right direction component in the increasing direction. Therefore, step S14 is a process of determining whether or not a side slip of the wheel W on the upper side of the slope has occurred based on the lateral acceleration change amount ΔGy.

  If it is determined as “Yes” in all of Steps S11 to S14, the brake ECU 40 estimates that the vehicle body has started rotating on the slope due to the side slip of the wheel W on the upper side of the slope as described above. Then, the process proceeds to step S15.

  In step S15, the brake ECU 40 determines the inclination direction of the slope (the slope where the vehicle is stopped) detected by the inclination sensor 46 (whether it is an uphill or a downhill) and the wheel W on the upper side of the slope. The wheel to be controlled is set based on the direction in which the vehicle slides sideways. The direction in which the wheel W on the upper side of the slope slides can be estimated as the direction in which the lateral acceleration Gy detected by the lateral acceleration sensor 45 acts. The direction in which the lateral acceleration Gy works is represented by the sign of the lateral acceleration Gy.

  For example, as shown in FIG. 5, when the vehicle 1 stops on an uphill and the vehicle body is rotating due to the side slip of the front wheel WF, as shown in FIG. 7, the rotation direction of the vehicle body (the lateral acceleration Gy By driving the rear wheel WR in the direction opposite to the direction) in the reverse direction, the vehicle body can be rotated in the direction to return to the original position. Further, for example, as shown in FIG. 6, when the vehicle 1 stops on a downhill and the vehicle 1 is rotationally moved by a side slip of the rear wheel WR, as shown in FIG. By driving the rear wheel WR in the same direction as the direction of the lateral acceleration Gy in the reverse direction, the vehicle body can be rotated in a direction to return the vehicle body to its original position. In step S15, the brake ECU 40 sets (specifies) one of the left and right rear wheels WRL and WRR to be driven in the reverse direction as a control target wheel in order to rotate the vehicle body in the direction to return the vehicle body.

  Specifically, as shown in FIG. 10, when the direction of the lateral acceleration Gy is the right direction, the wheel to be controlled is the left rear wheel WRL if it is uphill, and the right rear wheel WRR if it is downhill. Set to When the direction of the lateral acceleration Gy is the left direction, the wheel to be controlled is set to the right rear wheel WR if it is an uphill, and to the left rear wheel WRL if it is a downhill.

  When the control target wheel is set, the brake ECU 40 determines whether the control target wheel is the right rear wheel WRR or the left rear wheel WRL in the subsequent step S16. If the wheel to be controlled is the right rear wheel WRR, the brake ECU 40 controls the brake actuator 42 to reduce the hydraulic pressure of the wheel cylinder of the right rear wheel WRR in step S17. Thus, even when the driver is stepping on the brake pedal, the braking force of the right rear wheel WRR can be released. In this case, the braking forces of the other three wheels WFL, WFR, WRL are not released.

  On the other hand, if the wheel to be controlled is the left rear wheel WRL, the brake ECU 40 controls the brake actuator 42 in step S18 to reduce the hydraulic pressure of the wheel cylinder of the left rear wheel WRL. Thus, even when the driver is stepping on the brake pedal, the braking force of the left rear wheel WRL can be released. Also in this case, the braking forces of the other three wheels WFL, WFR, WRR are not released.

  When the braking force of the wheel to be controlled is released in this way, the brake ECU 40 transmits a drive command for driving the rear motor 13 in the reverse direction to the drive ECU 30 in step S19. Thus, the drive ECU 30 drives the rear motor 13 in the reverse direction with a predetermined driving force. However, the drive ECU 30 maintains the driving force of the front wheels WF at “0” and does not change it. In this case, in a state where the driver does not step on the accelerator pedal (state where the brake pedal is pressed), the wheel to be controlled is automatically driven in the reverse direction. Therefore, in a situation where the vehicle body is rotationally moving on the slope due to the side slip of the wheel W on the upper side of the slope, a force that causes the vehicle body to generate a rotational motion in a direction opposite to the direction of rotation is applied to the rear of the left and right sides. It can be given to the wheel WRL (WRR).

  For example, as shown in FIG. 5, when the vehicle body rotates in the right direction due to the skidding of the front wheel WF on an uphill, the braking force of the right rear wheel WRR is maintained as shown in FIG. The wheel WRL is driven in the reverse direction. As a result, the vehicle body is returned in a direction opposite to the direction in which the vehicle body is rotating due to the side slip of the front wheel WF. Further, for example, as shown in FIG. 6, when the vehicle body is rotated leftward due to the skidding of the rear wheel WR on the downhill, the braking force of the right rear wheel WRR is maintained as shown in FIG. The left rear wheel WRL is driven in the reverse direction. As a result, the vehicle body is returned in the direction opposite to the direction in which the vehicle body is rotating due to the side slip of the rear wheel WR.

  Subsequently, in step S20, the brake ECU 40 determines whether or not the magnitude | Gy | of the lateral acceleration Gy detected by the lateral acceleration sensor 45 is equal to or less than the control end threshold value Gyref. In the present embodiment, the control end threshold Gyref is set to zero (Gyref = 0), but is not limited to zero, and is preferably zero or a value near zero. If the lateral acceleration | Gy | is larger than the control end threshold value Gyref, the brake ECU 40 returns the process to step S15 and repeats the above-described process. The loop processing from step S15 to step S20 is also repeated at a predetermined short calculation cycle.

  When such a process is repeated, the vehicle body rotates on the slope so that the longitudinal axis thereof approaches the slope inclination direction. Accordingly, the lateral acceleration | Gy | gradually decreases. Thus, when the longitudinal axis of the vehicle body substantially coincides with the inclination direction of the slope, the lateral acceleration | Gy | reaches the control end threshold Gyref or less. When the brake ECU 40 detects that the lateral acceleration | Gy | is equal to or less than the control end threshold value Gyref (S20: Yes), the routine ends.

  When this routine is finished, the brake ECU 40 finishes releasing the braking force of the wheel to be controlled. Therefore, a braking force corresponding to the driver's braking operation is generated on the control target wheel (the braking force is maintained as it is except for the control target wheel). Further, when this routine is finished, the brake ECU 40 transmits a control end command to the drive ECU 30. As a result, the drive ECU 30 stops the rear motor 13. Thus, the rotational movement of the vehicle body is stopped.

  According to the vehicle control apparatus of the present embodiment described above, the vehicle 1 is stopped by a braking operation on an off-road or other slope (four wheels are locked), and the vehicle body is moved by the skidding of the wheel W on the upper side of the slope. Even if it starts to rotate on a slope, a rotational movement in a direction opposite to the rotational direction can be generated in the vehicle body. That is, a force that directs the vehicle body in the original direction can be applied to the vehicle body. Therefore, even if the driver does not have advanced driving skills, the front and rear axes of the vehicle can be prevented from greatly deviating from the inclination direction of the hill with the brake pedal depressed. Thus, according to the present embodiment, the vehicle 1 can be satisfactorily descended from a slope such as an off-road that easily slides.

  Further, in the present embodiment, since the side slip of the wheel W is detected based on the lateral acceleration change amount ΔGy that is the change amount of the lateral acceleration Gy that is the vehicle lateral direction component of the gravitational acceleration, the wheel on which the vehicle body rotates on the slope road. Can be detected satisfactorily. Further, since the wheel to be controlled is driven in the reverse direction until the magnitude | Gy | of the lateral acceleration Gy which is the vehicle lateral component of the gravitational acceleration becomes equal to or less than the control end threshold value Gyref, the direction of the vehicle body on the slope is appropriate. The vehicle body can be rotated to the position.

  Further, in the present embodiment, the inclination direction (whether uphill or downhill) of the slope (the slope where the vehicle is stopped) detected by the inclination sensor 46, and the wheels on the upper side of the slope The wheel to be controlled is set based on the direction in which W slides sideways. Therefore, even when the stop state is detected on the uphill or the stop state is detected on the downhill, the vehicle body can be properly rotated on the slope.

  Although the vehicle control apparatus according to the present embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in this embodiment, the rear wheels WRL and WRR are applied to the vehicle 1 driven by a single rear motor 13, but as shown in FIG. 11, the rear wheels WRL and WRR are incorporated in the rear wheels WRL and WRR. The present invention can also be applied to a vehicle 1 ′ of a type in which the left rear wheel WRL and the right rear wheel WRR are independently driven by the wheel motors 13L and 13R. In this case, in step S19, only the in-wheel motor 13L (or 13R) of the wheel to be controlled needs to be driven in the reverse direction. The in-wheel motor 13L (or 13R) of the wheel to be controlled is driven in the reverse direction, and simultaneously, the braking force of the wheel that is not the wheel to be controlled is released and the in-wheel motor 13R (or 13L) is driven in the forward direction. May be. In this case, the vehicle body can be rotated more satisfactorily.

  Further, in the present embodiment, both the case where the vehicle 1 stops on the uphill and the case where the vehicle 1 stops on the downhill prevent the skidding of the wheel W on the upper side of the slope, but instead, the vehicle 1 Only when the vehicle stops on the uphill, or only when the vehicle 1 stops on the downhill, skidding of the wheel W on the upper side of the slope may be prevented. For example, the off-road slope vehicle control routine may be executed only when the inclination sensor 46 detects that the vehicle is stopped on an uphill. Conversely, the off-road slope vehicle control routine may be performed only when the inclination sensor 46 detects that the vehicle has stopped on a downhill.

  In the present embodiment, the side slip of the wheel W on the upper side of the slope is detected based on the lateral acceleration change amount ΔGy. Instead, the upper side of the slope is detected based on the lateral acceleration of the vehicle body or the yaw rate of the vehicle body. A side slip of the wheel W on the side may be detected.

  In the present embodiment, the present invention is applied to a vehicle in which the front wheels WF are driven by the engine 11 and the front motor 12 and the rear wheels WR are driven by the rear motor 13. For example, for the front wheels WF, only the engine is used. Alternatively, it may be driven only by the motor, and the rear wheel WR may be driven only by the engine or by the engine and the motor.

  DESCRIPTION OF SYMBOLS 1,1 '... Vehicle, 10 ... Hybrid system, 11 ... Engine, 12 ... Front motor, 13 ... Rear motor, 13L, 13R ... In-wheel motor, 30 ... Drive ECU, 40 ... Brake ECU, 41FL, 41FR, 41RL, 41RR ... friction brake mechanism, 42 ... brake actuator, 43 ... brake sensor, 44 ... wheel speed sensor, 45 ... lateral acceleration sensor, 46 ... tilt sensor, WF ... front wheel, WR ... rear wheel, WFL, WFR, WRL, WRR ... left and right Front and rear wheels.

Claims (5)

A vehicle control device applied to a four-wheel drive vehicle capable of driving and controlling the rear wheels independently of the front wheels, and capable of braking control of at least the rear wheels independently of the left and right sides,
Stop state detection means for detecting a stop state on a slope where the rotation of the left and right front and rear wheels is stopped by a brake operation and the front and rear direction of the vehicle is not horizontal.
An upper wheel slip detection means for detecting a side slip of a wheel on an upper side of the slope when the stop state is detected;
When a side slip of the wheel on the upper side of the slope is detected, the left and right side wheels of the rear wheel are caused to generate a rotational movement of the vehicle body in a direction opposite to a direction in which the vehicle body rotates due to the side slip. A vehicle control device comprising: rear wheel control means for releasing braking force and applying driving force in the reverse direction. The vehicle control device according to claim 1,
The stop state detection means is configured to detect the stop state on the uphill of the vehicle when rotation of the left and right front and rear wheels is stopped by a brake operation,
The upper wheel side slip detection means is configured to detect a side slip of the front wheel when the stopping state on the uphill is detected.
The rear wheel control means releases the braking force and drives the vehicle in the reverse direction with respect to the left and right rear wheels that are opposite to the direction in which the vehicle body rotates due to the side slip when the side slip of the front wheel is detected. A vehicle control device configured to apply force. The vehicle control device according to claim 1,
The stop state detection means is configured to detect the stop state on the downhill of the vehicle when rotation of the left and right front and rear wheels is stopped by a brake operation,
The upper wheel side slip detecting means is configured to detect a side slip of the rear wheel when the stop state on the downhill is detected,
The rear wheel control means releases the braking force and drives the vehicle in the reverse direction with respect to the left and right rear wheels that are in the same direction as the vehicle body rotates due to the side slip when the side slip of the rear wheel is detected. A vehicle control device configured to apply force. In the vehicle control device according to any one of claims 1 to 3,
Lateral acceleration acquisition means for acquiring lateral acceleration which is a vehicle lateral direction component of gravitational acceleration;
The upper wheel skid detection means includes
Based on a change in lateral acceleration acquired by the lateral acceleration acquisition means, configured to detect a side slip of the wheel,
The rear wheel control means includes
When the lateral acceleration obtained by the lateral acceleration obtaining means reaches a value equal to or smaller than a threshold value, the release of the braking force and the application of the driving force to the rear wheels on the left and right sides are finished. Vehicle control device. The vehicle control device according to claim 1,
Direction acquisition means for acquiring direction information indicating a direction in which the wheels on the upper side of the slope slide sideways;
Slope acquisition means for acquiring slope information indicating whether the slope is an uphill or a downhill when the stop state is detected, and
The rear wheel control means includes
A vehicle control device configured to specify the left and right side wheels of the rear wheel that releases the braking force and applies a driving force in the reverse direction based on the direction information and the slope information.

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