Off-road traveling control device for vehicle

Abstract

To provide an off-road traveling control device for a vehicle for appropriately controlling air pressures of wheels according to a road surface state during off-road travelling of the vehicle.SOLUTION: When all or some of right / left front wheels 14 and right / left rear wheels 16 are determined to have been slipped by S2 corresponding to a slip determination part 90, in a state where it is determined that an off-road mode has been selected by an off-road mode determination part 88, an off-road travelling control part 92 enables lowering the air pressure(s) of the slipped wheel(s) or all of the wheels, and after that, when no wheel is determined to have been slipped by the slip determination part 90, the air pressures of the wheels are raised to a predetermined value and a driving control part 86 enables limiting driving forces of the wheels. This allows the air pressures and driving forces of the wheels to be appropriately controlled according to a road surface state during off-road travelling of a vehicle, thereby significantly enhancing the off-road travelling performance thereof.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an off-road driving control device for a vehicle that controls the air pressure and driving force of wheels (tires) according to the slip state of the wheels during off-road driving of the vehicle in order to improve off-road driving performance.

Background Art

[0002] When a vehicle is driving off-road, it has been proposed to reduce the air pressure of the wheels to increase the contact area of the wheels and improve the traction of the vehicle. For example, the vehicle described in Patent Document 1 is like this.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in off-road driving, the road surface state such as road surface μ and road surface properties (sand, soil, rock, ice and snow) changes randomly, and accordingly the wheels repeat slip and grip, and the appropriate air pressure also changes.

[0005] However, in the vehicle described in Patent Document 1, since the air pressure of the wheels when the off-road mode is selected is uniquely determined as a preset value, the optimization of the air pressure of the wheels is insufficient, and there is a problem that the driving performance cannot be sufficiently improved.

[0006] The present invention has been made based on the above circumstances, and an object thereof is to provide an off-road driving control device that appropriately controls the air pressure of wheels according to the road surface state when the vehicle is driving off-road.

Means for Solving the Problem

[0007] The gist of the present invention is: (a) an off-road driving control device for a vehicle that controls the air pressure and driving force of wheels during off-road driving of the vehicle, (b) an off-road mode determination unit that determines whether or not the off-road mode is selected, (c) a slip determination unit that determines whether or not the wheels are slipping, (d) in a state where it is determined by the off-road mode determination unit that the off-road mode is selected, when it is determined by the slip determination unit that the wheels are slipping, the air pressure of the wheels is lowered, and when it is determined that the wheels are not slipping, the air pressure of the wheels is raised to a predetermined value, an off-road driving control unit, and (e) a drive control unit that limits the driving force of the wheels that are determined not to be slipping and whose air pressure has been raised to the predetermined value.

Advantages of the Invention

[0008] According to the present invention, by the off-road driving control unit, in a state where it is determined by the off-road mode determination unit that the off-road mode is selected, when it is determined by the slip determination unit that the wheels are slipping, the air pressure of the wheels is lowered, and when it is determined that the wheels are not slipping, the air pressure of the wheels is raised to a predetermined value, and at the same time, the driving force of the wheels is limited by the drive control unit. Thereby, when the vehicle is driving off-road, the air pressure and driving force of the wheels are appropriately controlled according to the road surface conditions, so that the driving performance of off-road driving can be sufficiently improved.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Best Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

Embodiment

[0011] As shown in FIG. 1, a four-wheel drive vehicle (hereinafter referred to as a vehicle) 10 to which the present invention is applied includes an engine 12 that functions as a power source, and a power transmission device 18 that transmits the driving force output from the engine 12 to a pair of left and right front wheels 14 and a pair of left and right rear wheels 16. The power transmission device 18 includes a torque converter 20, an automatic transmission 22, a transfer 24 that can be switched between 2WD and 4WD, a front propeller shaft 26, a rear propeller shaft 28, a front differential 30, a rear differential 32, a pair of left and right front drive shafts 34, and a pair of left and right rear drive shafts 36. An engine control device 38 including a throttle actuator, a fuel injection device, an ignition device, etc. is controlled according to commands from an electronic control device 80 described later, so that the engine speed of the engine 12 and the engine torque Te, which is the output torque of the engine 12, are controlled.

[0012] This vehicle 10 includes a pneumatic supply device 40 that controls the air pressure of the front wheels 14 and the rear wheels 16. The pneumatic supply device 40 includes an air pump 42, a pressure accumulator 44 composed of a pressure-resistant container, a pressure accumulator pressure sensor 46 that detects the air pressure in the pressure accumulator 44, four supply pipes 48, 50, 52, 54 that supply the air in the pressure accumulator 44 to the pair of left and right front wheels 14 and the pair of left and right rear wheels 16 respectively, four pressure control valves 56, 58, 60, 62 that are respectively provided in these supply pipes 48, 50, 52, 54 and control the air pressure of the left and right front wheels 14 and the left and right rear wheels 16 respectively, and four tire air pressure sensors 64, 66, 68, 70 that detect the tire air pressure of these front wheels 14 and rear wheels 16.

[0013] Wheel speed sensors 72, 74, 76, and 78 for detecting the wheel speeds of the left and right front wheels 14 and the left and right rear wheels 16 are provided on the left and right front wheels 14 and the left and right rear wheels 16.

[0014] The vehicle 10 includes a so-called microcomputer and is equipped with an electronic control unit 80 as a controller including a control device for controlling the engine 12 and the like. The electronic control unit 80 is configured to include computers for engine control, shift control, shift change control, and the like.

[0015] Various signals etc. (for example, engine rotational speed Ne, AT input rotational speed Ni, AT output rotational speed No corresponding to the vehicle speed V, accelerator opening θacc which is the driver's accelerator operation amount representing the magnitude of the driver's acceleration operation, throttle valve opening θth which is the opening of the electronic throttle valve, longitudinal acceleration Gx and lateral acceleration Gy of the vehicle 10, etc.) based on the detection values by various sensors etc. provided on the vehicle 10 are respectively supplied to the electronic control unit 80. Also, signals representing the tire air pressures Pw1, Pw2, Pw3, Pw4 of the left and right front wheels 14 and the left and right rear wheels 16, the air pressure Pa in the accumulator 44, and the wheel speeds (km / h) Vw1, Vw2, Vw3, Vw4 of the left and right front wheels 14 and the left and right rear wheels 16 are respectively supplied to the electronic control unit 80.

[0016] An off-road mode selection switch 82 for selecting an off-road mode for traveling on road surfaces such as unpaved roads, sandy roads, and muddy roads is provided on the front panel of the vehicle 10.

[0017] The electronic control unit 80 corresponds to an off-road driving control device and functionally includes a wheel air pressure control unit 84, a drive control unit 86, an off-road mode determination unit 88, a slip determination unit 90, and an off-road driving control unit 92.

[0018] The wheel air pressure control unit 84 controls the air pump 42 to maintain the air pressure in the accumulator 44 at a preset constant original pressure SP. The original pressure SP is set higher than the normal air pressure preset for normal road surface driving. Also, the wheel air pressure control unit 84 controls the pressure control valves 56, 58, 60, 62 to set the air pressures of the left and right front wheels 14 and the left and right rear wheels 16 to the commanded air pressures. During normal road surface driving, the normal air pressure preset in advance is used.

[0019] When the off-road mode is selected in response to the operation of the off-road mode selection switch 82, the drive control unit 86 optimally controls the driving force and the braking force according to the driving environment so that the driving force during low-speed driving can be utilized to the maximum extent in order to enhance the off-road running performance. Also, when the slip is eliminated due to the decrease in the air pressure of the wheel where slip is determined, the drive control unit 86 restricts the driving force of that wheel.

[0020] The off-road mode determination unit 88 determines whether any one of a plurality of types of off-road modes, such as an unpaved road, a sandy road, and a muddy road, is selected in response to the operation of the off-road mode selection switch 82.

[0021] The slip determination unit 90 calculates the vehicle body speed (km / h) BV based on, for example, the average value of the wheel speeds Vw1, Vw2, Vw3, Vw4 of the left and right front wheels 14 and the left and right rear wheels 16, the average value of the values obtained by excluding the maximum value among the wheel speeds Vw1, Vw2, Vw3, Vw4, or the minimum value among the wheel speeds Vw1, Vw2, Vw3, Vw4. Then, the slip determination unit 90 calculates the slip amount, which is the difference between the wheel speeds Vw1, Vw2, Vw3, Vw4 and the vehicle body speed BV, and determines that the wheel corresponding to the value exceeding a preset slip determination value (for example, α km / h close to 0) is slipping.

[0022] When the off-road driving control unit 92 determines that any one of the left and right front wheels 14 and the left and right rear wheels 16 is slipping in a state where the off-road mode determination unit 88 has determined that the off-road mode is selected, it reduces the air pressure of that wheel or all of the left and right front wheels 14 and the left and right rear wheels 16. When it is determined that the wheel determined to be slipping is no longer slipping, it generates a commanded air pressure to increase the air pressure of the wheel whose air pressure has been reduced to a predetermined value.

[0023] Figure 2 is a flowchart for explaining the main part of the control operation of the electronic control unit 80. In Figure 2, in step S1 corresponding to the off-road mode determination unit 88 (hereinafter, steps are omitted), for example, it is determined whether the off-road mode has been selected by operating the off-road mode selection switch 82. If the determination in S1 is negative, this routine is terminated. If it is positive, in S2 corresponding to the slip determination unit 90, it is determined whether the wheel speeds Vw1, Vw2, Vw3, Vw4 match the vehicle body speed BV, that is, whether the slip amount, which is the difference between the wheel speeds Vw1, Vw2, Vw3, Vw4 and the vehicle body speed BV, is less than or equal to a preset slip determination value (for example, α km / h close to 0). If the determination in S2 is negative, that is, if it is determined that slip has occurred, in S3 corresponding to the off-road driving control unit 92, a commanded air pressure is generated to reduce the air pressure of the wheel determined to be slipping or all of the left and right front wheels 14 and the left and right rear wheels 16 below the normal air pressure for driving on a normal road surface, and this routine is terminated. As a result, the flipping force of the wheel whose air pressure has been reduced is increased. While such control is repeatedly executed, when the determination in S2 is positive, S4 corresponding to the off-road driving control unit 92 and S5 corresponding to the drive control unit 86 are executed. In S4, a commanded air pressure is generated to raise the air pressure of the wheel whose air pressure has been reduced in S3 to a predetermined value set lower than the normal air pressure. Then, in S5, in order to suppress slip, the drive control unit 86 suppresses the driving force of the wheel whose air pressure has been raised to the predetermined value.

[0024] As described above, according to the electronic control device 80 of the present embodiment, in a state where it is determined that the off-road mode is selected by S1 corresponding to the off-road mode determination unit 88, if it is determined by S2 corresponding to the slip determination unit 90 that all or part of the left and right front wheels 14 and the left and right rear wheels 16 are slipping, then by S3 and S4 corresponding to the off-road driving control unit 92, while the air pressure of the slipping wheel or all the wheels is decreased, and then, if it is determined by the slip determination unit 90 that the wheels are not slipping, the air pressure of the wheels is increased to a predetermined value and the driving force of the wheels is limited by S5 corresponding to the drive control unit 86. Thereby, When the vehicle is traveling off-road, since the air pressure and driving force of the wheels are appropriately controlled according to the road surface condition, the running performance of off-road driving can be sufficiently enhanced.

[0025] Note that the above is merely an embodiment of the present invention, and the present invention can be implemented in various modified forms without departing from the gist thereof.

[0026] For example, although the vehicle 10 of the foregoing embodiment is a vehicle having only the engine 12 as a drive source, it may be a hybrid vehicle equipped with the engine 12, the TM rotary machine, and the TF rotary machine as drive sources, or an electric vehicle having only the TF rotary machine as a drive source.

[0027] Also, the automatic transmission 22 may be any of a stepped transmission, a belt-type continuously variable transmission, an electric continuously variable transmission, and the like.

[0028] Note that the above is merely one embodiment, and the present invention can be implemented in a manner with various changes and improvements based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0029] 10: Vehicle (four-wheel drive vehicle), 12: Engine, 14: Front wheels, 16: Rear wheels, 18: Power transmission device, 22: Automatic transmission, 24: Transfer case, 40: Pneumatic supply device, 80: Electronic control device (off-road driving control device), 82: Off-road mode selection switch, 88: Off-road mode determination unit, 86: Drive control unit, 90: Slip determination unit, 92: Off-road driving control unit

Claims

【Claim 1】 An off-road driving control device for a vehicle that controls the air pressure and driving force of wheels during off-road driving of the vehicle, an off-road mode determination unit that determines whether an off-road mode is selected, a slip determination unit that determines whether the wheel is slipping, an off-road driving control unit that reduces the air pressure of the wheel when it is determined by the slip determination unit that the wheel is slipping in a state where it is determined by the off-road mode determination unit that the off-road mode is selected, and increases the air pressure of the wheel to a predetermined value when it is determined that the wheel is not slipping, and a drive control unit that limits the driving force of the wheel that is determined not to be slipping and whose air pressure has been increased to a predetermined value. An off-road driving control device for a vehicle, characterized by the above.

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