JP2007099209A - Vehicle turning device, and vehicle turning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle turning device, and a vehicle turning method capable of suppressing the protrusion of a vehicle when turning the vehicle, and turning the vehicle in a narrow space. <P>SOLUTION: In the vehicle turning device for turning a vehicle having a right front wheel 14FR, a left front wheel 14FL, a right rear wheel 14RR and a left rear wheel 14RL, a consolidated ECU moves at the turning center while the vehicle is turned in a vehicle inside area A<SB>O</SB>which is an area surrounded by a line extending the vehicular right-to-left direction from a front-most part of the vehicle, a line extending in the vehicular right-to-left direction from a rear-most part of the vehicle, a line passing through a right front wheel king pin position K<SB>FR</SB>and a right rear wheel king pin position K<SB>RR</SB>, and a line passing through the left front wheel king pin position K<SB>FL</SB>and the left rear wheel king pin position K<SB>RL</SB>. A turning device independently turns each wheel so as to be turned around the moved turning center. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle turning device and a vehicle turning method, and more particularly, to a vehicle turning device and a vehicle turning method including a turning unit that turns each of a plurality of wheels independently.

In recent years, development of a vehicle turning device that independently steers each front wheel and rear wheel has been underway. Such a vehicle turning device improves the operability of the driver by turning each of the front wheels and the rear wheels independently according to the operation of the driver, the state of the vehicle, and the like. On the other hand, in such a vehicle turning device, when the front wheels and the rear wheels are steered in opposite directions in order to turn the vehicle suddenly, one of the side surfaces of the vehicle protrudes during turning. For this reason, for example, Patent Document 1 proposes a vehicle turning device in which the target turning center position is set on the extension line of the rear end of the vehicle at the beginning of turning of the vehicle and the target turning center position is gradually moved forward as the turning proceeds thereafter. Has been.
JP 2001-334951 A

  However, even in the vehicle turning device described in the above-mentioned patent document, it is difficult to reduce the turning radius of the vehicle. For this reason, the trajectory in which the vehicle can turn is greatly restricted. In particular, when the direction is changed in a narrow space, it is difficult to provide the driver with good operability because the direction cannot be changed unless the steering wheel is turned over many times.

  The present invention has been made in view of these problems, and an object thereof is to suppress the amount of overhang of the vehicle when turning the vehicle and to turn the vehicle in a narrow space.

  In order to solve the above-described problem, a vehicle turning device according to an aspect of the present invention includes a vehicle turning device in a vehicle having a pair of front wheels and a pair of rear wheels, a straight line extending in the vehicle left-right direction from the frontmost portion of the vehicle, A straight line extending in the vehicle left-right direction from the rearmost part of the vehicle, a straight line passing through the turning center of the right front wheel and the turning center of the right rear wheel, and a straight line passing through the turning center of the left front wheel and the turning center of the left rear wheel And a turning control means for moving the turning center during turning of the vehicle, and a turning means for independently turning each wheel so as to turn about the moved turning center. Drive control means for determining the drive torque of each wheel so as to turn around the turning center, and drive means for independently driving each wheel by the determined drive torque.

  According to this aspect, since the turning center can be moved during the turning of the vehicle in such a region, the turning of the vehicle can be performed in a narrow space by reducing the turning radius of each wheel. Thus, it is possible to suppress the amount of the vehicle protruding to the outside of the vehicle during turning.

  The turning control means may set a turning center at the rear of the vehicle at the beginning of turning, and move the turning center forward of the vehicle as the turning angle increases. According to this aspect, the amount of protrusion of the rear part of the vehicle to the outside of the vehicle can be suppressed, and the vehicle can turn in a narrow space.

  The turning control means may set the turning center on a straight line connecting the respective turning centers of the pair of rear wheels at the beginning of turning, and may move the turning center forward of the vehicle as the turning angle increases. According to this aspect, it is possible to suppress the amount of the vehicle body around the rear wheel protruding to the outside of the vehicle, and to turn the vehicle in a narrow space.

  The turning control means may set the turning center on a straight line extending in the left-right direction from the rearmost part of the vehicle at the beginning of turning, and may move the turning center forward of the vehicle as the turning angle increases. According to this aspect, the amount of the vehicle body protruding to the outside of the vehicle can be suppressed, and the vehicle can turn in a narrow space.

  The turning control means turns on a vehicle center line that is a straight line passing through a midpoint of a straight line connecting the turning centers of each of the pair of front wheels and a midpoint of a straight line connecting each of the turning centers of the pair of rear wheels. You may move the center. According to this aspect, the turning radius of each wheel can be reduced, and it is possible to turn in a narrow space. Moreover, the balance of the driving torque of the two front wheels and the two rear wheels can be maintained, and it is possible to suppress a burden on any of the driving means provided on each wheel.

The turning angle is θ, the length of half of the straight line connecting the midpoint of the straight line connecting the turning centers of each of the pair of front wheels and the midpoint of the straight line connecting each of the turning centers of the pair of rear wheels, L, The midpoint of the straight line connecting the turning center of each of the pair of front wheels and the middle point of the straight line connecting each of the turning centers of the pair of rear wheels is set as the origin, and the vehicle front from the origin is x when the positive direction of the coordinate, the turning control means is a x-coordinate of the turning center x _P may be moved to pivot so as to satisfy _{x P = -L * cos (θ} ).

  According to this aspect, the amount of the vehicle body protruding to the outside of the vehicle can be suppressed, and the vehicle can be turned in a narrow space. Further, by turning the vehicle by 180 °, the vehicle can be moved to the side from the position of the vehicle at the beginning of the turn, and the vehicle can proceed smoothly after turning by 180 °.

  The vehicle turning device according to this aspect is a mode selection unit that accepts selection by the user between a first mode in which the turning center is set outside the region and a second mode in which the turning center is moved within the region while the vehicle is turning. May be further provided. The turning control means may move the turning center within the region when the second mode is selected. According to this aspect, it is possible to provide the user with an opportunity to select one of the first mode and the second mode according to the situation of the vehicle.

  The vehicle turning device according to this aspect is a mode selection unit that accepts selection by the user between a first mode in which the turning center is set outside the region and a second mode in which the turning center is moved within the region while the vehicle is turning. May be further provided. When the second mode is selected, the drive control means may determine the drive torque of each wheel so that the vehicle turns with a greater force as the steering angle of the steering increases. According to this aspect, since the force for turning the vehicle can be adjusted by adjusting the steering angle of the steering wheel, the operability of the driver can be improved.

  Another aspect of the present invention is a vehicle turning method. This method is a vehicle turning method for a vehicle having a pair of front wheels and a pair of rear wheels, a straight line extending in the left-right direction of the vehicle from the frontmost part of the vehicle, a straight line extending in the left-right direction of the vehicle from the rearmost part of the vehicle, During the turning of the vehicle in an area surrounded by a straight line passing through the turning center of the front wheel and the turning center of the right rear wheel and a straight line passing through the turning center of the left front wheel and the turning center of the left rear wheel A step of moving the turning center, a step of independently turning each wheel to turn about the moved turning center, and a driving torque of each wheel to turn about the moved turning center are determined. And independently driving each wheel with the determined driving torque.

  According to this aspect, since the turning center can be moved during the turning of the vehicle in such a region, the turning of the vehicle can be performed in a narrow space by reducing the turning radius of each wheel. Thus, it is possible to suppress the amount of the vehicle protruding to the outside of the vehicle during turning.

  According to the vehicle turning device and the vehicle turning method of the present invention, the amount of overhang of the vehicle when turning the vehicle can be suppressed, and the vehicle can be turned in a narrow space.

  Hereinafter, embodiments of the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.

  FIG. 1 is an overall configuration diagram of the vehicle turning device 200. This figure is a view of the vehicle as viewed from above. The vehicle 10 equipped with the vehicle turning device 200 includes a right front wheel 14FR, a left front wheel 14FL, a right rear wheel 14RR, and a left rear wheel 14RL (hereinafter collectively referred to as “wheel 14” as necessary) 4. It is composed of two wheels 14 and a vehicle body 12.

  Corresponding to each of the wheels 14, the vehicle body 12 includes a right front wheel in-wheel motor 20FR, a left front wheel in-wheel motor 20FL, a right rear wheel in-wheel motor 20RR, and a left rear wheel in-wheel motor 20RL (hereinafter referred to as necessary). These are collectively referred to as “in-wheel motor 20”).

  Each of the in-wheel motors 20 includes a rotor, a stator, a speed reduction mechanism, and the like (not shown). The rotor is provided so as to be rotatable coaxially with the wheel 14. The stator is composed of a coil wound in an annular shape so as to surround the rotor, and is fixed to the cover of the in-wheel motor 20. The speed reduction mechanism is constituted by a gear mechanism, and reduces the rotation of the rotor and transmits it to the wheel 14. Thereby, each of the wheels 14 can be driven independently by the in-wheel motor 20.

  Each of the in-wheel motors 20 is connected to a hybrid electronic control unit 42 (hereinafter referred to as “HV-ECU 42”). Each of the in-wheel motors 20 is also connected to a battery (not shown), and the HV-ECU 42 controls the supply of electric power from the battery to each of the in-wheel motors 20, whereby each of the wheels 14. Control the drive. The HV-ECU 42 is connected to an integrated electronic control unit 100 (hereinafter, “electronic control unit” is referred to as “ECU”), and electric power supplied to each of the in-wheel motors 20 in accordance with a calculation result input from the integrated ECU 100. To decide.

  Each in-wheel motor 20 is provided with a wheel speed sensor 22. In the present embodiment, the wheel speed sensor 22 employs an encoder that is a rotation sensor including a slit and an optical sensor that is provided with a slit and is rotatable with the operation of the motor. Of course, a rotation sensor based on a Hall IC method or a pickup coil method may be employed for the wheel speed sensor 22. Each of the wheel speed sensors 22 is connected to the integrated ECU 100, and the detection result of the wheel speed sensor 22 is input to the integrated ECU 100.

  Each of the wheels 14 is rotatably supported by a knuckle arm 40 provided on the vehicle body 12 corresponding to each of the wheels 14. The knuckle arm 40 is supported so as to be rotatable about a substantially vertical axis, with the joint portion of the upper arm in the upper portion and the joint portion of the lower arm in the lower portion. Thus, the king pin as a virtual axis is formed by the joint portion of the upper arm and the joint portion of the lower arm. The wheel 14 is steered around the kingpin formed in this way.

  Corresponding to each of the wheels 14, a right front wheel steering device 25FR, a left front wheel steering device 25FL, a right rear wheel steering device 25RR, a left rear wheel steering device 25RL (hereinafter referred to as these if necessary) Are collectively referred to as a “steering device 25”). Each of the steering devices 25 includes a right front wheel steering motor 24FR, a left front wheel steering motor 24FL, a right rear wheel steering motor 24RR, and a left rear wheel steering motor 24RL (hereinafter referred to as necessary). Are collectively referred to as "steering motor 24"). Each of the steering devices 25 includes a ball screw mechanism 27 and a tie rod 38 in addition to the steering motor 24.

  The wheel side end of the tie rod 38 is rotatably connected to the knuckle arm 40. A male screw groove is formed on the other outer periphery of the tie rod 38. A nut (not shown) formed in a cylindrical shape is arranged so as to cover the portion of the tie rod 38 where the male screw groove is formed. A female thread groove is formed on the inner periphery of the nut. A plurality of rolling balls are arranged in a rolling path formed by the male thread groove of the tie rod 38 and the female thread groove of the nut, and the ball screw mechanism 27 is configured. The steered motor 24 has a rotor and a stator, and the rotor of the steered motor 24 is fixed coaxially with the nut. When the rotor and the nut are rotated by the operation of the steering motor 24, the rotational motion of the steering motor 24 is converted into the axial motion of the tie rod 38 by the ball screw mechanism 27, and the tie rod 38 is propelled in the axial direction. Thereby, the knuckle arm 40 is rotated and the wheel 14 is steered around the kingpin.

  The right front wheel steering motor 24FR is connected to the right front wheel steering ECU 26FR. Similarly, the left front wheel steering motor 24FL is for the left front wheel steering ECU 26FL, the right rear wheel steering motor 24RR is for the right rear wheel steering ECU 26RR, and the left rear wheel steering motor 24RL is for the left rear wheel. The steering ECU 26RL is connected to the steering ECU 26RL. ECU26 "). Each of the steered motors 24 rotates an angle corresponding to the drive signal when the drive signal is input from the steered ECU 26. The steered ECU 26 independently controls the steered angle of each wheel 14 by controlling a drive signal input to the steered motor 24. Each of the steering ECUs 26 is connected to the integrated ECU 100, and determines a drive signal to be input to the steering motor 24 in accordance with a calculation result input from the integrated ECU 100.

  Corresponding to each of the wheels 14, a right front wheel brake 16FR, a left front wheel brake 16FL, a right rear wheel brake 16RR, a left rear wheel brake 16RL (hereinafter collectively referred to as “brake” if necessary) 16 ”). In the present embodiment, a disc brake is employed for the brake 16. In each caliper of the brake 16, a right front wheel wheel cylinder 18FR, a left front wheel wheel cylinder 18FL, a right rear wheel wheel cylinder 18RR, a left rear wheel wheel cylinder 18RL (hereinafter collectively referred to as necessary). (Referred to as “wheel cylinder 18”). The brake 16 has a disc rotor, a caliper, a brake pad, etc. (not shown). The disc rotor is rotatably fixed together with the wheel 14, and the caliper and the brake pad are fixed to the vehicle body 12 side. When the hydraulic pressure in the wheel cylinder 18 is increased, the brake pad as the pressing body is pressed against the brake pad as the rotating body, and a braking force is applied to the wheel 14.

  Each of the wheel cylinders 18 communicates with a brake fluid pressure generator 50. A later-described pressure increasing valve and pressure reducing valve included in the brake fluid pressure generating device 50 are connected to the ECB-ECU 44. The ECB-ECU 44 controls the hydraulic pressure of the wheel cylinder 18 independently for each of the wheels 14 by controlling the opening and closing of these valves. The ECB-ECU 44 is connected to the integrated ECU 100, and controls the opening and closing of these valves using the calculation result input from the integrated ECU 100.

  A brake pedal 28 is provided in the vehicle 10. The brake pedal 28 is connected to the brake sensor 30, and the brake sensor 30 is connected to the integrated ECU 100. When the brake pedal 28 is operated by a driver as a user, the brake sensor 30 detects an operation amount of the brake sensor 30 and inputs a detection result to the integrated ECU 100.

  A steering wheel 32 is provided in the vehicle 10. The steering 32 is fixed to a rotatable steering shaft, and a steering angle sensor 34 is provided on the steering shaft. The steering angle sensor 34 is connected to the integrated ECU 100. When the steering wheel 32 is steered by the driver, the steering angle sensor 34 detects the steering angle of the steering wheel 32 and inputs the detection result to the integrated ECU 100.

  A mode changeover switch 36 is provided in the vehicle 10. The mode changeover switch 36 functions as a mode selection unit that accepts selection by the driver in the 4WS mode and the direction change mode described later. The mode changeover switch 36 is connected to the integrated ECU 100, and when the driver accepts selection of either the 4WS mode or the direction change mode, the selection result is input to the integrated ECU 100.

  FIG. 2 is a functional block diagram of each ECU. As described above, the vehicle turning device 200 of the present embodiment includes the integrated ECU 100, the steering ECU 26, the ECB-ECU 44, the HV-ECU 42, and the like.

  The integrated ECU 100 includes an arithmetic unit 102, a RAM 104, a ROM 106, and the like. The ROM 106 stores data including programs for executing various calculations and maps such as a yaw angle-turning center map and a steering angle-braking / driving force map, which will be described later. The RAM 104 temporarily stores various data including detection results of the steering angle sensor 34, the brake sensor 30, and the wheel speed sensor 22, and is used as a work area for executing a program stored in the ROM 106. . The arithmetic unit 102 uses a program stored in the ROM 106, data stored in the RAM 104, and the like to perform a four-wheel turning angle calculation, a four-wheel turning radius calculation, a four-wheel driving force distribution calculation, a yaw rate estimation calculation, a yaw rate estimation calculation, which will be described later. Performs various calculations such as angle estimation calculations.

  The integrated ECU 100 is connected to the turning ECU 26 and inputs the calculated target turning angle of each wheel 14 to the turning ECU 26. The steering ECU 26 determines the target turning angle of each wheel 14 using the input calculation result, and inputs a drive signal to each of the turning motors 24 to turn the wheel 14 to the target turning angle. To do. Therefore, the integrated ECU 100 functions as a turning control unit that determines the turning angle of each wheel 14 so as to turn around the moved turning center P, and the turning device 25 uses the moved turning center P as the turning angle. It functions as a turning means for turning each wheel 14 independently so as to turn to the center.

  The brake fluid pressure generator 50 includes a right front wheel pressure increasing valve 52FR, a left front wheel pressure increasing valve 52FL, a right rear wheel pressure increasing valve 52RR, and a left rear wheel pressure increasing valve 52RL (hereinafter collectively referred to as necessary). A “pressure-increasing valve 52”). The pressure increasing valve 52 is constituted by a linear solenoid valve, and opens or closes according to the duty of the input current. When the pressure increasing valve 52 is opened, brake oil as hydraulic fluid is supplied from the accumulator (not shown) to the wheel cylinder 18, and the braking force applied to the wheel 14 by increasing the wheel cylinder pressure. Is increased.

  The brake fluid pressure generator 50 includes a right front wheel pressure reducing valve 54FR, a left front wheel pressure reducing valve 54FL, a right rear wheel pressure reducing valve 54RR, and a left rear wheel pressure reducing valve 54RL (hereinafter collectively referred to as necessary). (Referred to as “pressure reducing valve 54”). The pressure reducing valve 54 is constituted by a linear solenoid valve, and opens or closes according to the duty of the input current. When the pressure reducing valve 54 is opened, the hydraulic fluid in the wheel cylinder 18 is released to the reservoir, and the braking force applied to the wheel 14 is reduced by reducing the wheel cylinder pressure.

  The integrated ECU 100 is connected to the ECB-ECU 44 and inputs the calculated target wheel cylinder pressure of each wheel cylinder 18 to the ECB-ECU 44. The ECB-ECU 44 determines the target wheel cylinder pressure of each of the wheel cylinders 18 using the input calculation result, and supplies a control current to the drive circuit that drives each of the pressure increasing valves 52 and each of the pressure reducing valves 54. Supply. Each of the drive circuits supplies current to the pressure increasing valve 52 or the pressure reducing valve 54 at a duty according to the supplied control current. Thereby, the ECB-ECU 44 controls the hydraulic pressure of each wheel cylinder 18 to the target wheel cylinder pressure.

  The integrated ECU 100 is connected to the HV-ECU 42 and inputs the calculated target drive torque of each wheel 14 to the HV-ECU 42. The HV-ECU 42 determines the target drive torque of each of the wheels 14 using the input calculation result, and generates a current for generating the target drive torque for each of the in-wheel motors 20 from the battery. Each is supplied to generate a target drive torque. Therefore, the integrated ECU 100 functions as a drive control unit that determines the drive torque of each wheel 14 so as to turn around the moved turning center P, and the in-wheel motor 20 uses the determined drive torque to set each wheel. It functions as a driving means for driving 14 independently.

FIG. 3 is a diagram illustrating a turning angle, a turning center, and the like of each of the wheels 14 when the 4WS mode is selected. This figure is a view of the vehicle 10 as viewed from above. Passes through a straight line extending in the left-right direction of the vehicle 10 from the frontmost part of the vehicle 10, a straight line extending in the left-right direction of the vehicle 10 from the rearmost part of the vehicle 10, and the turning center of the right front wheel 14FR and the turning center of the right rear wheel 14RR. a straight line, a vehicle inner area a ₀ the region surrounded by the straight line passing through the turning center of the turning center and the left rear wheel 14RL of the left front wheel 14FL is.

The midpoint of the straight line connecting the right front wheel kingpin position K _FR and the left front wheel kingpin position K _FL and front wheel king pin center point M _1, in a straight line connecting the right rear wheel kingpin position K _RR and a left rear wheel kingpin position K _RL and the rear wheel kingpin middle point M ₂ a point. The middle point of a straight line connecting the front wheel kingpin midpoint M ₁ and rear wheels kingpin midpoint M ₂ as the origin O. Direction from the origin O to the front wheel kingpin midpoint M _1, that is, the vehicle front from the origin O to the positive direction of x. Further, the left direction of the vehicle from the origin O is defined as the positive direction of y. The wheel base indicating the distance between the king pin position of the front wheel and the king pin position of the rear wheel is 2L.

Right front wheel kingpin position _K right x-coordinate front wheel _FR kingpin x coordinate _{x FR,} the right front wheel king pin y-coordinate _{y FR} y coordinates. The x-coordinate of the left front wheel kingpin position _{K FL} to the left front wheel kingpin x coordinate _{x FL,} y coordinates and the left front wheel king pin y-coordinate _{y FL.} Right rear wheel the x coordinate of the right rear wheel kingpin position _{K RR} kingpin x coordinate _{x RR,} the right rear wheel kingpin y-coordinate _{y RR} y coordinates. The left rear wheel kingpin position _{K RL} of the left rear wheel of the x-coordinate kingpin x-coordinate _{x RL,} the y-coordinate and the left rear wheel kingpin y-coordinate _{y RL.} Note that the x coordinate of the turning center P is the turning center x coordinate x _P , and the y coordinate is the turning center y coordinate y _P.

Right front wheel speed _{V FR} wheel speed of the right front wheel 14FR, the left front wheel speed the wheel speed of the left front wheel 14FL _{V FL,} the right rear wheel 14RR right rear wheel speed _{V RR} of the wheel speed of the left wheel speed of the left rear wheel 14RL The rear wheel speed is _VRL . The wheel speed is a positive value when the wheel 14 rotates in the rotation direction when the vehicle moves forward. For example, if the front right wheel 14FR and rear-right wheel 14RR, the right front wheel speed V _FR and the right rear wheel speed V _RR is a positive value when right rotation viewed from the right side of the vehicle. Further, if the front left wheel 14FL and rear-left wheel 14RL, the left front wheel speed V _FL and the rear left wheel speed V _RL becomes a positive value when the counterclockwise rotation when viewed from the left side of the vehicle.

Further, the turning angle of the right front wheel 14FR is the right front wheel turning angle δ _FR , the turning angle of the left front wheel 14FL is the left front wheel turning angle δ _FL , the turning angle of the right rear wheel 14RR is the right rear wheel turning angle δ _RR , left rear the steered angle of the wheels 14RL and a left rear wheel steering angle [delta] _RL. When the rotation axis of the wheel 14 is parallel to the y-axis, the steering angle of the wheel 14 is a positive value when the wheel 14 is steered in the counterclockwise direction from a state where the steering angle of the wheel 14 is zero. It shall be Incidentally, the steering angle of the steering 32 is steered by the driver to the steering angle [delta] _MA.

When the driver operates the mode change switch 36 and selects the 4WS mode, the selection result for the mode change switch 36 is input to the integrated ECU 100. When the 4WS mode is selected, the integrated ECU 100 executes a program for calculating the turning center for the 4WS mode. In the 4WS mode, the integrated ECU 100 calculates the target turning angle so that the right front wheel 14FR and the left front wheel 14FL are turned in the same direction. That is, integration ECU100 the positive and negative of the right front wheel steering angle [delta] _FR and the right rear wheel steering angle [delta] _RR is to be the same, and calculates the target steering angle. Similarly, the integrated ECU 100 calculates a target turning angle so that the left front wheel 14FL and the left rear wheel 14RL are steered in the same direction. That is, integration ECU100 is positive and negative left front wheel steering angle [delta] _FL and the rear left wheel steering angle [delta] _RL is computed target turning angle to be the same.

Therefore, in the 4WS mode, integration ECU100 sets the turning center P outside the vehicle interior region _{A 0.} Therefore, 4WS mode functions as a first mode in which outside the turning center of the vehicle inner area A ₀ is set. In practice, 4WS mode turning area A ₁ as region capable of turning center P is positioned in the 4WS mode is determined by the turning angle of the wheels 14 that can be steered. For example, as shown in the figure, 4WS mode turning region A ₁ when the vehicle turns to the left, the extension line of the vehicle 10 outside the rotation axis of the left front wheel 14FL when turning the front left wheel 14FL This is an area where the locus drawn and the locus drawn by the extension line of the rotation axis of the left rear wheel 14RL to the outside of the vehicle 10 when the left rear wheel 14RL is steered overlap.

The integrated ECU 100 is suitable for steering the vehicle 10 by using the wheel speed of each of the wheels 14 detected by the wheel speed sensor 22 and the steering angle δ _MA of the steering 32 detected by the steering angle sensor 34. The turning center P is calculated. Thus, by selecting the 4WS mode when the vehicle 10 is traveling, the driver can turn the vehicle well.

Further, when the driver operates an accelerator pedal (not shown), the integrated ECU 100 uses the operation amount of the accelerator pedal, the steering angle δ _MA of the steering 32 detected by the steering angle sensor 34, and the like, A target drive torque to be applied to each of the wheels 14 is calculated. Further, when the driver operates the brake pedal 28, the integrated ECU 100 determines the operation amount of the brake pedal 28 detected by the brake sensor 30, the steering angle δ _MA of the steering 32 detected by the steering angle sensor 34, and the like. Utilizing this, the target wheel cylinder pressure of each wheel 14 is calculated. Thus, in the 4WS mode, the driver can adjust the driving force of the vehicle by operating the accelerator pedal, and can adjust the braking force of the vehicle by operating the brake pedal 28.

  FIG. 4 is a diagram showing a turning angle, a turning center, and the like of each of the wheels 14 when the direction change mode is selected. This figure is a view of the vehicle 10 as viewed from above. Note that a description of the same parts as in FIG. 3 is omitted.

  When the mode switch 36 is operated by the driver and the direction change mode is selected, the selection result for the mode switch 36 is input to the integrated ECU 100. When the direction change mode is selected, the integrated ECU 100 executes a program for calculating the turning center for the direction change mode.

In the direction change mode, the integrated ECU 100 calculates the target turning angle so that the right front wheel 14FR and the left front wheel 14FL are steered in different directions, that is, the right front wheel 14FR and the left front wheel 14FL are turned into a "C" shape. Specifically, integration ECU100 is positive and negative is different of the right front wheel steering angle [delta] _FR and the right rear wheel steering angle [delta] _RR, can be calculated target turning angle. Similarly, the integrated ECU 100 calculates the target turning angle so that the left front wheel 14FL and the left rear wheel 14RL are steered in different directions, that is, the right front wheel 14FR and the left front wheel 14FL are turned into a "C" shape. Specifically, integration ECU100 calculates the target steering angle so that the positive and negative different left front wheel steering angle [delta] _FL and the rear left wheel steering angle [delta] _RL.

Therefore, in the turning mode, integration ECU100 passes linearly, and the left front wheel kingpin position _{K FL} and the left rear wheel kingpin position _{K RL} passing right front wheel kingpin position _{K FR} and the right rear wheel kingpin position _{K RR} A turning center P is set in a region between the straight lines. Thereby, since the turning center P can be set between the left and right wheels 14, the turning radius of each of the wheels 14 can be reduced, and the vehicle 10 can be turned in a narrow space.

Further, in the present embodiment, the integrated ECU 100 has a turning center P in a region between a straight line extending in the left-right direction of the vehicle 10 from the frontmost part of the vehicle 10 and a straight line extending in the left-right direction of the vehicle 10 from the rearmost part of the vehicle 10. Set. As a result, for example, the turning center P can be moved forward from the straight line extending in the left-right direction of the vehicle 10 from the rearmost part of the vehicle 10 and the overhang of the vehicle body to the outside of the vehicle 10 can be suppressed. It becomes. Thus, in the turning mode, so that the turning center P in a vehicle interior region A within ₀ is moved. Therefore, the direction change mode functions as a second mode in which the turning center is moved in the vehicle interior area A ₀ while the vehicle 10 is turning.

In fact, turning mode the turning region A ₂ as region which can be positioned turning center P is in the turning mode is determined by the turning angle of the wheels 14 that can be steered. Turning mode the turning region A ₂ is a respective vehicle 10 region locus overlaps the extension line drawn to the inside of the rotation axis of the wheel 14 when the steering each wheel 14.

In the present embodiment, the right front wheel 14FR and the left front wheel 14FL, the angle that the extension line of the vehicle 10 inside the rotary shaft toward the rear wheel kingpin midpoint M ₂ is in the maximum steering angle. The right rear wheel 14RR, a left rear wheel 14RL, the angle of the vehicle 10 inside the extension line of the rotation axis toward the front wheel kingpin midpoint M ₁ is in the maximum steering angle. Therefore, as shown in the figure, the turnable area A ₂ in the direction change mode includes two straight lines from the rear wheel kingpin middle point M ₂ to the right front wheel kingpin position K _FR and the left front wheel kingpin position K _FL , and the front wheel kingpin. a diamond surrounded from the midpoint M ₁ by two straight lines toward the right rear wheel kingpin position K _RR and a left rear wheel kingpin position K _RL.

Incidentally, by increasing the maximum steering angle of each wheel 14, the direction change mode turning region A ₂ can be further increased. Even in this case, the integrated ECU 100 sets the turning center P in a region between a straight line extending in the left-right direction of the vehicle 10 from the frontmost part of the vehicle 10 and a straight line extending in the left-right direction of the vehicle 10 from the rearmost part of the vehicle 10. To do. Further, by configuring each of the wheels 14 so as to be able to steer 360 °, all the vehicle interior area A ₀ can be set as the turnable area A ₂ in the direction change mode. Thus, integrated ECU100 includes the automotive interior area A _0, and functions as a turning control means for moving the pivot in the turning of the vehicle. By setting the turning center P inside the vehicle, the turning radius of each of the wheels 14 can be reduced, and the vehicle 10 can be steered in a narrow space.

Mode switch 36 is operated by the driver, the turning mode is selected, setting the rear wheel kingpin midpoint M ₂ as the initial turning center P, upwardly of the steering ECU26 showing the turning center P set Enter each one. Each of the steering ECUs 26 steers the wheel 14 so that the rotation axis of the wheel 14 is directed to the rear wheel kingpin midpoint M ₂ in order to set the rear wheel kingpin midpoint M ₂ as the turning center P. As a result, as shown in the figure, the right front wheel 14FR and the left front wheel 14FL are steered into a letter C shape opened rearward of the vehicle 10, and the right rear wheel 14RR and the left rear wheel 14RL are steered in parallel.

  When turning the front end of the vehicle 10 to the right side from the state of this figure, as shown by the arrows in this figure, the left front wheel 14FL and the left rear wheel 14RL are given drive torque in the forward direction, and the right front wheel 14FR and the right The rear wheel 14RR is given drive torque in the reverse direction. Accordingly, the vehicle 10 can be turned around the turning center P while suppressing the side slip of each of the wheels 14.

  The integrated ECU 100 calculates the turning angle of the vehicle 10 from the wheel speed and turning radius of each wheel 14. The integrated ECU 100 refers to the yaw angle-turning center map stored in the ROM 106 and determines the turning center P from the calculated turning angle of the vehicle 10. Since the driver does not need to perform an operation for moving the turning center, the driver's operability can be prevented from being reduced in order to move the turning center.

In the present embodiment, in accordance with the yaw angle of the turning angle of the vehicle 10 increases, turning center P moves from the rear wheel kingpin midpoint M ₂ on the x-axis in front of the vehicle 10. Since the turning center P moves from the rear wheel kingpin midpoint M ₂ forward, while suppressing the projecting amount of the vehicle 10 outward, it is possible to reduce the space required to turn the vehicle 10. Therefore, for example, even when either the left or right side of the vehicle is close to an obstacle such as a wall, the vehicle 10 can be turned in a narrow space while avoiding contact with the obstacle. Further, since the turning center P moves on the x axis, it is possible to maintain the balance of driving torque between the right front wheel 14FR and the left front wheel 14FL and the balance of driving torque between the right rear wheel 14RR and the left rear wheel 14RL. It is possible to suppress a burden on the in-wheel motor 20 of any one of the wheels 14.

  When the turning center P moves to the front of the vehicle 10, the right rear wheel 14RR and the left rear wheel 14RL are steered into a letter C that opens to the front of the vehicle 10, and as the turning center P moves to the front, It is steered so that the opening of the character becomes large. The right front wheel 14FR and the left front wheel 14FL are steered so that the C-shaped opening becomes smaller as the turning center P moves forward of the vehicle 10.

FIG. 5 is a yaw angle-turning center map in the direction change mode. In the figure, the horizontal axis represents the yaw angle theta, the vertical axis represents the rotation center x coordinate x _P and pivot y-coordinate y _P.

Mode switch 36 is operated by the driver, the turning mode is selected, integrated ECU100 sets the rear wheel kingpin midpoint M ₂ as the initial turning center P. The yaw angle θ of the time as zero, when the vehicle is turning from this position, integration ECU100 is, y _P is moved the turning center P so as to satisfy y P _{= 0.} As a result, the turning center P moves on the x axis.

The integrated ECU100 is, _{x P moves} the rotation center so as to satisfy x P = -L * cos (θ ). Accordingly, the amount of the vehicle body protruding to the outside of the vehicle 10 can be suppressed, and the vehicle 10 can turn in a narrow space. Further, by turning the vehicle 10 by 180 °, the vehicle can be moved to the side from the position of the vehicle 10 at the beginning of the turn, and the vehicle can smoothly travel after the 180 ° turn.

  FIG. 6 is a flowchart showing a processing procedure of the vehicle turning device 200. The processing in this flowchart starts when the driver turns on the ignition key of the vehicle 10 and turns on the power source of the integrated ECU 100 and the like.

When the driver selects the direction change mode by operating the mode changeover switch 36 (S11), information indicating the selected mode is input to the integrated ECU 100. Integration ECU100, when turning mode is selected by the driver to set the turning center P to the rear wheel kingpin midpoint _{M 2} as the initial turning center (S12). When turning center P to the rear wheel kingpin midpoint _{M 2} is set, the steering ECU26, each of the rotation axis of the wheel 14 is steered wheels 14 to face the rear wheel kingpin midpoint _{M 2} (S13) . When the wheel 14 is steered, the integrated ECU 100 sets the yaw angle θ to zero (S14).

  Further, the integrated ECU 100 disables the accelerator pedal (S15). As a result, even if the driver operates the accelerator pedal, no driving torque is applied to the wheels 14. By the above, it will be in the initial state of direction change mode.

When the steering is steered by the driver after the direction change mode is in the initial state (S16), the integrated ECU 100 refers to the steering angle-braking / driving force map as shown in FIG. Determine T _ALL . The integrated ECU100 the yaw angle shown in FIG. 5 - with reference to the rotation center map, pivot x-coordinate x _P and pivot y-coordinate y _P, and the wheel 14 each 4-wheel turning radius by using the kingpin coordinates of Calculation is executed to calculate a right front wheel turning radius R _FR , a left front wheel turning radius R _FL , a right rear wheel turning radius R _RR , and a left rear wheel turning radius R _RL . The four-wheel turning radius calculation is executed by the following equation.

  Here, “**” means that FR indicating the right front wheel, FL indicating the left front wheel, RR indicating the right rear wheel, and RL indicating the left rear wheel are input when calculating the turning radius of each of the wheels 14. Indicates.

As shown in FIG. 7, the integrated ECU 100 uses the determined T _ALL and the calculated turning radius of each of the wheels 14 to execute a four-wheel driving force distribution calculation, and the right front wheel driving torque T _FR , The left front wheel driving torque T _FL , the right rear wheel driving torque T _RR , and the left rear wheel driving torque T _RL are calculated (S17). The four-wheel driving force distribution calculation is executed by the following equation. “**” is the same as described above.

At this time, the right front wheel 14FR and the left front wheel 14FL, and the right rear wheel 14RR and rear left wheel 14RL from rotating in the reverse direction to each other, running four-wheel driving force distribution calculation, right front wheel drive torque _{T FR,} the left The front wheel driving torque T _FL , the right rear wheel driving torque T _RR , and the left rear wheel driving torque T _RL are executed by the following equations.

  When the four-wheel driving force distribution calculation is executed, the integrated ECU 100 inputs the calculated driving torque of each wheel 14 to the HV-ECU 42. The HV-ECU 42 supplies electric power to the in-wheel motor 20 so as to generate the input drive torque, and generates the calculated drive torque for each of the wheels 14 (S18).

Thus, when it is in the turning mode, integration ECU100, like a large force for pivoting about a steering angle [delta] _MA of the steering 32 is large is given to the vehicle, determines the driving torque to be applied to each wheel 14 can do. As a result, a driving torque corresponding to the steering angle δ _MA of the steering wheel 32 and the turning radius of each wheel 14 can be generated in each wheel 14, and smooth turning of the vehicle 10 about the turning center P is realized. can do.

  As shown in FIG. 7, the integrated ECU 100 executes a yaw rate estimation calculation based on the detection result of the wheel speed sensor 22 and the calculated turning radius of each wheel 14 to calculate the yaw rate γ. The yaw rate estimation calculation is executed by the following equation.

  Next, the integrated ECU 100 uses the calculated yaw rate to execute a yaw angle estimation calculation to calculate the yaw angle θ. The yaw angle estimation calculation is executed by the following equation.

  The integrated ECU 100 refers to the yaw angle-turning center map again, moves the turning center P based on the calculated yaw angle θ, and uses the moved turning center P to calculate the four-wheel turning radius and to drive the four wheels. Perform force distribution operations. The integrated ECU 100 repeatedly executes these calculations while the steering wheel 32 is being steered by the driver, thereby determining the driving torque of each wheel 14 corresponding to the turning center P to be moved. Each drives each of the wheels 14 with a driving torque corresponding to the turning center P that moves.

The integrated ECU100, as shown in FIG. 7, the yaw angle - with reference to the turning center map, by using the turning center x coordinate x _P and pivot y-coordinate y _P, run the four-wheel steering angle calculation, The target right front wheel turning angle δ _FR , left front wheel turning angle δ _FL , right rear wheel turning angle δ _RR , and left rear wheel turning angle δ _RL are calculated (S19). The four-wheel turning angle calculation is executed by the following equation.

  The integrated ECU 100 inputs the calculated target turning angle of each wheel 14 to each of the turning ECUs 26. The steered ECU 26 steers the wheel 14 by inputting a drive signal to the steered motor 24 so as to steer the wheel 14 to the inputted target steered angle (S20). The integrated ECU 100 performs a four-wheel turning angle calculation every predetermined time, and turns each of the wheels 14 to an angle corresponding to the turning center P that has moved. As a result, smooth turning of the vehicle 10 around the turning center P can be realized.

Note that the driver, when it is steered in a direction to return the steering 32 is steered, integrated ECU100 the steering angle - braking-driving force with reference to the map, to determine the braking force corresponding to the returned steering angle [delta] _MA . The integrated ECU 100 inputs the determined braking force to the ECB-ECU 44. In order to generate the input braking force, the ECB-ECU 44 operates the pressure increasing valve 52 or the pressure reducing valve 54 to set the wheel cylinder pressure as the target wheel cylinder pressure. Thus, when steering action is taken in a direction to return the steering 32, it is possible to turn the vehicle 10 at a turning speed corresponding to the steering angle [delta] _MA.

  In the direction change mode, the driver can apply a braking force corresponding to the amount of operation of the brake pedal 28 to each of the wheels 14 by operating the brake pedal 28. When the brake sensor 30 is operated by the driver, the switch shown in FIG. 7 is switched, the ECB-ECU 44 is disconnected from the steering angle-braking / driving force map, and the ECB-ECU 44 and the brake sensor 30 are connected. Thereby, the operation amount information of the brake pedal 28 detected by the brake sensor 30 is input to the ECB-ECU 44. The ECB-ECU 44 determines the braking force to be applied to each of the wheels 14 based on the input operation amount information of the brake pedal 28 and operates the pressure increasing valve 52 or the pressure reducing valve 54 to target the wheel cylinder pressure. Use wheel cylinder pressure. Accordingly, the driver can apply a braking force to the vehicle 10 by operating the brake pedal 28.

By the driver, the steering angle [delta] _MA steering of the steering 32 to return to zero is is, or when the brake pedal 28 is operated (S21), ECB-ECU44 is boosts each wheel cylinder pressure of the wheel 14 The vehicle is stopped (S22). When the steering wheel 32 is steered again by the driver, the process is repeated from S16.

  When the driver determines that the vehicle 10 can be turned to a desired angle and operates the mode switch 36 to select another mode such as the 4WS mode (S23), the integrated ECU 100 operates in the direction change mode. Is released, and the process in the selected mode is executed (S24).

  FIG. 8 is a diagram illustrating a trajectory of turning of the vehicle 10 when the direction change mode is selected. As shown in this figure, when the direction change mode is selected, turning the vehicle 10 makes it possible to change the direction of the vehicle 10 in a narrow space while suppressing the amount of protrusion to the outside of the vehicle 10. It becomes. In addition, by performing the direction change of the vehicle 10 in the direction change mode, the vehicle 10 can be moved to the outside of the vehicle before turning. Thus, for example, when it is desired to change the direction to the opposite oblique line side in a narrow space or when the vehicle 10 is taken out from a narrow parking lot, the vehicle 10 can be effectively moved simultaneously with the change of direction of the vehicle 10.

  The present invention is not limited to the above-described embodiments, and an appropriate combination of the elements of each embodiment is also effective as an embodiment of the present invention. Various modifications such as design changes can be added to each embodiment based on the knowledge of those skilled in the art, and embodiments to which such modifications are added can also be included in the scope of the present invention. Here are some examples.

  When the direction change mode is selected, the integrated ECU 100 sets a straight turning center P that extends from the rear end of the vehicle 10 in the left-right direction of the vehicle 10, and sets the turning center P as the yaw angle θ increases. You may move 10 forward. As a result, the amount of the vehicle body protruding to the outside of the vehicle 10 can be suppressed, and the vehicle 10 can turn in a narrow space.

When the direction change mode is selected, the integrated ECU 100 may set the turning center P at the front portion of the vehicle 10 and move the turning center P toward the rear of the vehicle 10 as the yaw angle θ increases. For example, when the direction change mode is selected, the integrated ECU 100 sets the turning center P on a straight line connecting the right front wheel kingpin position _KFR and the left front wheel kingpin position _KFL, and as the yaw angle θ increases. The turning center P may be moved rearward of the vehicle 10. Further, for example, when the direction change mode is selected, a straight turning center P extending from the front end of the vehicle 10 in the left-right direction of the vehicle 10 is set, and the turning center P is set to the vehicle 10 as the yaw angle θ increases. You may move forward. As a result, the amount of protrusion of the rear portion of the vehicle 10 to the outside of the vehicle 10 can be suppressed, and the vehicle 10 can turn in a narrow space. Also in this case, integration ECU100, in vehicle center line passing through the rear wheel kingpin midpoint M ₂ a front wheel kingpin midpoint M _1, you may move the turning center P.

The integrated ECU100, in regions other than the on the x-axis or y-axis of the vehicle inner area A _0, the turning center P may be moved in turn. This also makes it possible to suppress the amount of protrusion to the outside of the vehicle 10.

In addition to the 4WS mode and the direction change mode, for example, a 2WS mode may be provided. The driver may operate the mode changeover switch 36 to select one of these modes, so that the integrated ECU 100 may execute processing in the selected mode. When the 2WS mode is selected, the integrated ECU 100 may set the right rear wheel steering angle δ _RR and the left rear wheel steering angle δ _RL to zero, and turn the vehicle 10 using only the right front wheel 14FR and the left front wheel 14FL. .

1 is an overall configuration diagram of a vehicle turning device. It is a functional block diagram of each ECU. It is a figure which shows the turning angle of each wheel, turning center, etc. when 4WS mode is selected. It is a figure which shows the turning angle of each wheel, turning center, etc. when a direction change mode is selected. It is a yaw angle-turning center map in the direction change mode. It is a flowchart which shows the process sequence of a vehicle turning apparatus. It is a figure which shows the outline | summary of the calculation which integrated ECU performs. It is a figure which shows the locus | trajectory in which a vehicle turns when the direction change mode is selected.

Explanation of symbols

  10 Vehicle, 14 Wheel, 18 Wheel Cylinder, 20 In-wheel Motor, 22 Wheel Speed Sensor, 24 Steering Motor, 26 Steering ECU, 28 Brake Pedal, 30 Brake Sensor, 32 Steering, 34 Steering Angle Sensor, 36 Mode Change Switch 38 tie rods, 40 knuckle arms, 42 HV-ECU, 44 ECB-ECU, 100 integrated ECU, 200 vehicle turning device.

Claims (9)

In a vehicle turning device for turning a vehicle having a pair of front wheels and a pair of rear wheels,
A straight line extending in the left-right direction of the vehicle from the frontmost part of the vehicle, a straight line extending in the left-right direction of the vehicle from the rearmost part of the vehicle, a straight line passing through the turning center of the right front wheel and the turning center of the right rear wheel, and the turning of the left front wheel A turning control means for moving the turning center during turning of the vehicle in an area surrounded by a rudder center and a straight line passing through the turning center of the left rear wheel;
Steering means for independently turning each wheel so as to turn around the moved turning center;
Drive control means for determining a drive torque of each wheel so as to turn about the moved turning center;
Driving means for independently driving each wheel by the determined driving torque;
A vehicle turning device comprising:   2. The vehicle turning device according to claim 1, wherein the turning control means sets a turning center at a rear portion of the vehicle at an early stage of turning, and moves the turning center forward of the vehicle as the turning angle increases.   The turning control means sets the turning center on a straight line connecting the turning centers of each of the pair of rear wheels at the beginning of turning, and moves the turning center forward of the vehicle as the turning angle increases. The vehicle turning device according to claim 1 or 2.   The turning control means sets a turning center on a straight line extending in the vehicle left-right direction from the rearmost part of the vehicle at the beginning of turning, and moves the turning center forward of the vehicle as the turning angle increases. The vehicle turning device according to 1 or 2.   The turning control means is a vehicle center that is a straight line passing through a midpoint of a straight line connecting the turning centers of each of the pair of front wheels and a midpoint of a straight line connecting each of the turning centers of the pair of rear wheels. The vehicle turning device according to any one of claims 1 to 4, wherein the turning center moves on a line. The turning angle is θ, and the half length of the straight line connecting the midpoint of the straight line connecting the turning centers of each of the pair of front wheels and the midpoint of the straight line connecting each of the turning centers of the pair of rear wheels is L, from the origin, with the midpoint of a straight line connecting the center of a straight line connecting the turning centers of each of the pair of front wheels and the midpoint of a line connecting each of the turning centers of the pair of rear wheels as an origin When the front of the vehicle is the positive direction of the x coordinate,
It said swing control means is the x-coordinate of the turning center x _P is,
x _P = −L * cos (θ)
The vehicle turning device according to claim 5, wherein the turning center is moved so as to satisfy the condition. A mode selection means for receiving selection by a user between a first mode in which the turning center is set outside the area and a second mode in which the turning center is moved in the area during turning of the vehicle;
The vehicle turning device according to any one of claims 1 to 6, wherein the turning control means moves a turning center within the region when the second mode is selected. A mode selection means for receiving selection by a user between a first mode in which the turning center is set outside the area and a second mode in which the turning center is moved in the area during turning of the vehicle;
The drive control means determines the drive torque of each wheel so that when the second mode is selected, the vehicle turns with a greater force as the steering angle increases. The vehicle turning device according to any one of 1 to 7. A vehicle turning method for a vehicle having a pair of front wheels and a pair of rear wheels,
A straight line extending in the left-right direction of the vehicle from the frontmost part of the vehicle, a straight line extending in the left-right direction of the vehicle from the rearmost part of the vehicle, a straight line passing through the turning center of the right front wheel and the turning center of the right rear wheel, and the turning of the left front wheel Moving the turning center during turning of the vehicle in an area surrounded by a rudder center and a straight line passing through the turning center of the left rear wheel;
Turning each wheel independently to turn about the moved turning center; and
Determining a driving torque of each wheel to turn about the moved turning center;
Independently driving each wheel with the determined drive torque;
A vehicle turning method comprising:

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