JP4506518B2 - Driving force control device - Google Patents

Description

  The present invention relates to a driving force control device that prevents a driving slip caused by an excessive driving force being transmitted to the wheels of an all-wheel drive vehicle in which all front wheels and rear wheels are driven.

  Conventionally, based on the detection signals of the wheel speed sensors provided on the front wheels and the rear wheels respectively, the rotational speed of the driving wheel consisting of one of the front and rear wheels and the rotational speed of the driven wheel consisting of the other of the front and rear wheels are determined. When the slip amount is calculated and it is determined that a predetermined spin is generated according to the calculated value of the slip amount, it is excessive by reducing the driving force of the engine or applying a braking force to the driving wheel. It has been attempted to improve the acceleration responsiveness of a vehicle while preventing the occurrence of a spin and ensuring the running stability of the vehicle. Thus, in a two-wheel drive vehicle in which one of the front and rear wheels is set as a driven wheel, the vehicle speed can be determined to some extent accurately based on the rotational speed of the driven wheel. It is possible to determine substantially accurately whether or not it is.

  However, in an all-wheel drive vehicle in which all of the front wheels and rear wheels are driven, all wheels may slip when traveling on a low μ road, etc. Therefore, there is a problem that it is difficult to accurately determine the vehicle speed based on the above, and it is not possible to properly determine whether or not each wheel is in a slip state. In order to solve such a problem, when it is confirmed that all the wheels have slipped, the detected value of the acceleration sensor for detecting the acceleration of the wheel or the rotational speed of the wheel having the lowest rotational speed among the wheels. The vehicle speed is estimated based on the above, and the slip control corresponding to the estimated value of the vehicle speed is performed.

For example, as shown in Patent Document 1, a four-wheel drive force distribution control device that distributes and controls the drive force to the four wheels by controlling the differential limiting amount according to the slip amount between the front and rear wheels. Longitudinal acceleration detecting means for estimating or detecting longitudinal acceleration generated in the vehicle, and minimum longitudinal acceleration calculating means for calculating the minimum longitudinal acceleration in accordance with the differential control amount of the four-wheel driving force distribution control device. When the vehicle is accelerating, the vehicle body speed is estimated by the vehicle body speed estimator using the larger of the minimum longitudinal acceleration value and the longitudinal acceleration detected by the longitudinal acceleration detector as the amount of change in the vehicle body speed. In addition, a driving force control device that executes control of the driving force transmitted from each wheel to the road surface by the driving force estimation means based on the driving slip determination using the estimated vehicle body speed is provided. It is.
JP 2001-80376 A

  As disclosed in Patent Document 1, the vehicle body speed is estimated using the minimum value of the longitudinal acceleration as the amount of change in the vehicle body speed in accordance with the differential limit amount of the front and rear wheels controlled by the four-wheel drive force distribution control device. With this configuration, it is possible to accurately estimate the vehicle speed and improve the driving force controllability when the estimated vehicle speed on an extremely low μ road suddenly increases. However, if a driver with excellent skills slips each wheel little by little while traveling on an extremely low μ road, etc., and the vehicle is traveling, all the wheels may be in a gradual slip state. Therefore, it is inevitable that the estimated value of the vehicle speed obtained by the vehicle body speed estimating means will gradually deviate from the actual vehicle speed, and even if the above configuration is adopted, an appropriate value corresponding to the estimated value of the vehicle speed is required. Therefore, there is a problem that it is difficult to suppress the driving slip.

  The present invention has been made in view of the above-described problems, and is based on the accurately estimated vehicle speed even when the vehicle is traveled while slipping each wheel little by little when traveling on an extremely low μ road or the like. An object of the present invention is to provide a driving force control device that can appropriately suppress driving slip.

  The invention according to claim 1 adjusts the distribution of the driving force to the front and rear wheels, and the slip control means for preventing the driving slip of each wheel caused by the excessive driving force being transmitted to the wheels of the all-wheel drive vehicle. A driving force control device having a driving force distribution mechanism provided with a hydraulic coupling, wherein the slip control means determines whether or not a situation in which all the wheels slip has occurred, Driving force for controlling the driving force distribution mechanism so that one of the front and rear wheels is a driving wheel and the other is a driven wheel for a predetermined time when it is determined that all the wheels slip. A distribution control unit, a braking force application control unit that applies a braking force for canceling the driving force input from the hydraulic coupling to the wheels that are driven wheels when a situation where all the wheels slip occurs, and With estimating the vehicle speed based on the rotational speed of the driving wheel, it is provided with a driving slip suppression unit that performs control to suppress the driving slippage of each wheel based on the estimated value of the vehicle speed.

  According to a second aspect of the present invention, in the driving force control apparatus according to the first aspect, the slip condition determining unit is configured such that a state where the rotational speeds of all the wheels are equal to or lower than a preset reference speed is over a certain time. In addition, when it is confirmed that the rotational speeds of all the wheels tend to increase, it is determined that a situation in which all the wheels slip has occurred.

  According to a third aspect of the present invention, in the driving force control apparatus according to the first or second aspect, the braking force application control is performed simultaneously with the execution of the control in which one of the front and rear wheels is a driven wheel by the driving force distribution control unit. In this configuration, the braking force is applied to the driven wheel side by the portion.

  According to a fourth aspect of the present invention, in the driving force control device according to any one of the first to third aspects, a temperature detection unit that detects the temperature of the driving force distribution mechanism is provided, and the temperature detection unit detects the temperature. The braking force applied to the wheel on the driven wheel side by the braking force application control unit is adjusted based on the generated temperature.

  According to a fifth aspect of the present invention, in the driving force control device according to any one of the first to fourth aspects, a hydraulic pump that raises the hydraulic pressure supplied to a brake device that applies a braking force to each wheel is provided. And a brake pressure adjusting means for adjusting the hydraulic pressure supplied to the brake device. The braking force applying portion controls the wheel on the driven wheel side. When applying power, the hydraulic pump is operated, and the hydraulic pressure supplied from the boosting means to the brake device on the driven wheel side is reduced by the brake pressure adjusting means.

  The invention according to claim 6 is the driving force control device according to any one of claims 1 to 5, wherein the front wheel brake device for applying a braking force to the front wheels and the braking force applied to the front wheels are provided. A rear wheel brake device that applies a low braking force to the rear wheel, and when it is determined that a situation where all the wheels slip occurs, the driving force distribution control unit sets the rear wheel side as a driven wheel. The driving force distribution control is executed, and the braking force is applied to the rear wheels by the braking force application control unit.

  According to the first aspect of the present invention, when it is determined that a situation in which all the wheels slip has occurred, one of the front and rear wheels is used as a drive wheel and the other of the front and rear wheels is a driven wheel over a predetermined time. The driving force distribution mechanism is controlled so that a braking force for canceling the driving force input from the hydraulic coupling is applied to the driven wheel, so that the vehicle speed is based on the rotational speed of the driven wheel. There is an advantage that the driving slip of each wheel can be effectively prevented based on the estimated value of the vehicle speed.

  According to the invention of claim 2, the state where the rotational speeds of all the wheels are not more than a preset reference speed is continued for a certain time or more, and the rotational speeds of all the wheels tend to increase. When it is confirmed, it is determined that the situation where all the wheels slip is generated, so when a driver with excellent skills travels on an extremely low μ road, each wheel is slipped little by little. However, there is an advantage that it is possible to accurately determine whether or not the vehicle is shifting to a state where all the wheels are slipping at the same time under a situation where the vehicle is traveling.

  According to the invention of claim 3, since it is configured to apply the braking force to the driven wheel by the braking force application control unit simultaneously with the execution of the control in which one of the front and rear wheels is driven wheel by the driving force distribution control, Since the vehicle speed can be estimated quickly and accurately based on the rotational speed of the driven wheel in a situation where all the wheels slip, the driving slip of each wheel can be more effectively determined based on the estimated value of the vehicle speed. There is an advantage that it can be prevented.

  According to the fourth aspect of the present invention, when the drag torque transmitted to the driven wheel fluctuates in accordance with the viscosity of the oil filled in the hydraulic coupling that changes corresponding to the temperature of the driving force distribution mechanism. By applying a braking force corresponding to this to the driven wheel, there is an advantage that the vehicle speed can be accurately estimated based on the rotational speed of the driven wheel under a situation where all the wheels slip.

  According to the fifth aspect of the present invention, when a braking force is applied to a wheel that is a driven wheel, the hydraulic pressure supplied from the pressure-increasing means to the brake device on the driven wheel side is reduced, thereby increasing the braking device. In order to prevent the hydraulic pressure from being supplied, and to apply an appropriate braking force to counteract the drag torque transmitted to the driven wheel according to the viscosity of the oil filled in the hydraulic coupling. The oil pressure can be finely adjusted accurately.

  According to the sixth aspect of the present invention, the braking force applied by the rear wheel braking device is set to a lower value than the braking force applied by the front wheel braking device in terms of braking efficiency. When it is determined that a situation in which all the wheels slip has occurred, the driving force distribution control unit executes driving force distribution control so that the left and right rear wheels are driven wheels, and the braking force application control is performed. By applying braking force to the left and right rear wheels by the unit, the hydraulic pressure supplied to the brake device can be accurately fine-tuned, so that the rotational speed of the left and right rear wheels can be adjusted under the condition that all wheels slip. There is an advantage that the vehicle speed can be accurately estimated based on this.

  FIG. 1 shows a schematic configuration of an all-wheel drive vehicle including a drive control device according to an embodiment of the present invention. This vehicle drive system has an engine 1, left and right front wheels 2, 3 and left and right rear wheels 4, 5. The driving force of the engine 1 is directly transmitted to the left and right front wheels 2, 3 and the left and right rear wheels The driving force of the engine 1 is transmitted to 4 and 5 via the driving force distribution mechanism 6. The driving force distribution mechanism 6 includes a hydraulic coupling 7 provided with a multi-plate clutch driven by a hydraulic actuator, and the driving of the engine 1 distributed to the left and right rear wheels 4 and 5 by the hydraulic coupling 7. By controlling the force according to the driving state of the vehicle, the front wheel driving state in which the total driving force is distributed to the front wheels 2, 3 side is changed to the all wheel driving state in which the driving force is uniformly distributed to all the wheels 2-5. It is configured to be migrated.

  Further, the vehicle includes wheel speed sensors 8 to 11 that detect rotational speeds of the wheels 2 to 5, brake devices 12 to 15 that apply braking force to the wheels 2 to 5, and the hydraulic coupling 7. Temperature detecting means comprising a temperature sensor 16 for detecting temperature, slip control means 17 for preventing driving slip of each wheel due to excessive driving force being transmitted to each wheel 2 to 5, and this slip control means A braking system 18 is provided for operating the brake devices 12 to 15 in response to a control signal output from 17.

  In the slip control means 17, it is determined that a situation in which all the wheels 2 to 5 slip has occurred and a situation in which all the wheels 2 to 5 have slipped are determined. A driving force distribution control unit 20 for controlling the driving force distribution mechanism 6 so that the left and right front wheels 2 and 3 are driven wheels and the left and right rear wheels 4 and 5 are driven wheels over a predetermined time. A braking force applying unit 21 that applies a braking force for canceling the driving force input from the hydraulic coupling 7 to the left and right rear wheels 7 and 8 that are driven wheels when a situation occurs in which the wheels 2 to 5 slip. A driving slip suppression unit 22 that estimates the vehicle speed based on the rotational speed of the driven wheels including the left and right rear wheels 4 and 5 and executes control for suppressing the driving slip of each wheel based on the estimated value of the vehicle speed. Is provided.

  The slip condition determination unit 19 continues a state in which the rotational speeds of all the wheels 2 to 5 are equal to or lower than a preset reference vehicle speed for a predetermined time or more according to detection signals of the wheel speed sensors 8 to 11. When it is confirmed that the rotational speeds of all the wheels 2 to 5 are increasing, it is determined that a situation in which all the wheels 2 to 5 slip is generated. The reference vehicle speed is set to a maximum speed that is considered to occur when a driver with excellent skills travels on an extremely low μ road or the like while slipping each wheel little by little.

  Further, the driving force distribution control unit 20 sets the multi-plate clutch of the hydraulic coupling 7 at a predetermined time when it is determined in the slip condition determining means 19 that a situation where all the wheels 2 to 5 slip occurs. By outputting a control signal for setting the detachment state to the driving force distribution mechanism 6, transmission of the driving force from the engine 1 to the left and right rear wheels 4, 5 is cut off and the left and right rear wheels 7, 8 are used as driven wheels. It is configured to perform control.

  The braking force application unit 21 applies the left and right rear wheels 4, 5 by the driving force distribution control unit 20 when it is determined in the slip condition determination means 19 that a situation has occurred in which all the wheels 2-5 slip. Simultaneously with the control of the driving wheels, a control signal is output to the braking system 18 to apply a predetermined braking force to the left and right rear wheels 4, 5, so that the driving force applied to the left and right rear wheels 4, 5 from the engine 1 is increased. In a state in which the transmission is cut off, a control for canceling the drag torque transmitted to the left and right rear wheels 4 and 5 according to the viscosity of the oil filled in the hydraulic coupling 7 is executed. The braking force applying unit 21 is a driven wheel based on the temperature of the hydraulic coupling 7 detected by the temperature sensor 16 when it is determined that all the wheels 2 to 5 slip. The braking force applied to the left and right rear wheels 4 and 5 is adjusted as described later.

  As shown in FIG. 2, the braking system 18 controlled by the braking force applying unit 21 controls the supply and discharge of hydraulic pressure to the brake devices 12 to 15 provided on the left and right front wheels 2 and 3 and the left and right rear wheels 4 and 5. By doing so, the front-wheel-side slip control hydraulic system 23a that prevents the drive slip from occurring on the left and right front wheels 2 and 3 and the rear-wheel-side slip control that prevents the left and right rear wheels 4 and 5 from generating a drive slip. And a hydraulic system 23b. The braking system 18 includes a tandem master cylinder 25 operated by a brake pedal 24, and a front wheel side slip control hydraulic system 23a and a rear wheel side slip control hydraulic system 23b from the master cylinder 25. There are provided a main passage 26 extending in the direction and a pump drive motor 28 for driving a hydraulic pump 27 provided in each of the slip control hydraulic systems 23a and 23b.

  Since the front wheel side slip control hydraulic system 23a has the same configuration as the rear wheel side slip control hydraulic system 23b, a specific configuration of the rear wheel side slip control hydraulic system 23b is described below. The description of the front wheel side slip control hydraulic system 23a will be omitted. The rear wheel side slip control hydraulic system 23b is provided with branch passages 29, 30 branched from the main passage 26 and connected to the brake devices 14, 15 of the left and right rear wheels 4, 5, respectively. A cut valve 31 composed of a solenoid valve for opening and closing the passage 26 and bypass passages 32 and 33 for bypassing the cut valve 31 are provided, and one of the bypass passages 32 allows only a hydraulic flow to the downstream side thereof. A check valve 34 is provided, and when the hydraulic pressure higher than the brake hydraulic pressure generated when the slip control is performed is applied to the other bypass passage 33, only a flow of the hydraulic pressure upstream is allowed. A valve 35 is provided.

  Further, the rear wheel side slip control hydraulic system 23b is provided with a pressure increasing cylinder 36 for increasing the hydraulic pressure of the main passage 26 when the slip control is executed. A discharge port 37 of the pressure increasing cylinder 36 is connected to the main passage 26 via a pressure increasing passage 38, and an input oil chamber 39 of the pressure increasing cylinder 36 is a hydraulic input path in which a hydraulic pump 27 is disposed. It is connected to the reservoir 41 via 40. The hydraulic input path 40 is provided with check valves 42 and 43 that allow only the flow of hydraulic pressure from the reservoir 41 to the hydraulic pump 27 side.

  A return passage 44 connected to the input oil chamber 39 of the pressure increasing cylinder 36 is connected to the reservoir 41. The return passage 44 includes a control valve 45 for opening and closing the return passage 44, an open / close type A relief valve 46 including a solenoid valve is provided. The piston 47 of the pressure-increasing cylinder 36 is biased toward the input oil chamber 39 by a return spring 48, and resists the biasing force of the return spring 48 when a predetermined hydraulic pressure is supplied to the input oil chamber 39. Thus, the hydraulic pressure is displaced in the direction of discharging from the discharge port 37. The hydraulic pump 27, the pump drive motor 28, the pressure-increasing cylinder 36, and the like constitute pressure increasing means for increasing the hydraulic pressure that applies a braking force to the wheels 2-5.

  The control valve 45 adjusts the hydraulic pressure supplied to the brake devices 14 and 15 of the left and right rear wheels 4 and 5, that is, the brake pressure, by opening and closing a return passage 44 connected to the reservoir 41. When the control valve 45 is fully opened, the hydraulic pressure returned from the hydraulic pump 27 to the reservoir 41 is maximized, and the hydraulic pressure supplied to the brake devices 14 and 15 is greatly reduced.

  The basic control operation of the driving force control apparatus will be described based on the flowchart shown in FIG. When this basic control operation starts, first, various data including the detection values of the wheel speed sensors 8 to 11 and the temperature sensor 16 are read (step S1), and the rotation speeds of all the wheels 2 to 5 are set in advance. It is determined whether or not the vehicle speed is below the reference speed (step S2). If YES is determined, it is determined whether or not the state below the reference vehicle speed is continued for a certain time (step S3). If YES is determined in step S3, the rotational speeds of all the wheels 2 to 5 are increased by determining whether or not the amount of change in the rotational speeds of all the wheels 2 to 5 is equal to or greater than a certain value. It is determined whether or not there is a tendency (step S4).

  While it is determined as YES in step S4 and the rotation speeds of all the wheels 2 to 5 are not more than a preset reference speed for a predetermined time or more, the rotation speeds of all the wheels 2 to 5 are increased. If the slip condition determining unit 19 confirms that all the wheels 2 to 5 slip due to the tendency, the driving force applied to the left and right rear wheels 4 and 5 over a predetermined time. A control signal for stopping the distribution is output from the driving force distribution control unit 20 to the driving force distribution mechanism 6 (step S5). Further, based on the temperature of the hydraulic coupling 7 detected by the temperature sensor 16, the braking force to be applied to the left and right rear wheels 4, 5 is read from a preset map, and a target value of the braking force is set (step) S6), the opening control of the control valve 45 corresponding to the target value of the braking force is executed (step S7).

  The map is transmitted to the left and right rear wheels 4 and 5 according to the viscosity of the oil filled in the hydraulic coupling 7 in a state where the transmission of the driving force from the engine 1 to the left and right rear wheels 4 and 5 is cut off. This is set based on experiments and the like conducted in advance so that a braking force for canceling the drag torque can be obtained. Specifically, the lower the temperature of the hydraulic coupling 7, the higher the viscosity of the oil and the greater the drag torque transmitted to the left and right rear wheels 4 and 5, which is shown in FIG. As described above, the braking force applied to the left and right rear wheels 4 and 5 is set to a large value.

  Next, the hydraulic pump 27 is operated for a predetermined time to apply a braking force to the left and right rear wheels 4, 5 (step S8). In this way, the distribution of the driving force to the left and right rear wheels 4 and 5 is stopped, and at the same time, a predetermined braking force is applied to the left and right rear wheels 4 and 5, and then the left and right rear wheels 4 and 5 that have become driven wheels. The vehicle body speed is estimated based on the rotation speed (step S9). Allocation of driving force to the predetermined time, that is, the left and right rear wheels 4 and 5, so that the vehicle body speed can be accurately estimated based on the rotational speeds of the left and right rear wheels 4 and 5 that are the driven wheels. The time for applying the braking force applied to the left and right rear wheels 4 and 5 by operating the hydraulic pump 27 is set.

  When it is determined NO in step S2 or S4 and it is confirmed that all the wheels 2 to 5 are not in a state of slipping, the process proceeds to step S9 and the rotation speed is the highest among the wheels 2 to 5. Normal vehicle speed estimation control is executed to estimate the vehicle speed based on the rotational speed of the wheel having a low speed. Based on the vehicle body speed estimated in step S9, the driving force transmitted from the engine 1 to each driving wheel is controlled according to the slip amount of each wheel, or each driving wheel is controlled by the brake devices 12-15. By controlling the input braking force, slip control that suppresses slipping of the drive wheels, that is, traction control, is executed in the drive slip suppression unit 22 (step S10).

  As described above, the slip control means 17 for controlling the wheels 2 to 5 to prevent the driving slip caused by the excessive driving force being transmitted to the wheels 2 to 5 of the all-wheel drive vehicle, and the front and rear wheels 2 In the driving force control device including the driving force distribution mechanism 6 including the hydraulic coupling 7 that adjusts the distribution of the driving force with respect to ˜5, the slip control means 17 has a situation in which all the wheels 2 to 5 slip. When it is determined that a situation in which all the wheels 2 to 5 slip has occurred and one of the front and rear wheels 2 to 5 is used as a drive wheel for a predetermined time when it is determined that a slip situation determination unit 19 that determines whether or not it has occurred. However, the driving force distribution control unit 20 that controls the driving force distribution mechanism 6 so that the other is a driven wheel, and the left and right rear wheels 4 and 5 that are driven wheels when all the wheels 2 to 5 slip. From hydraulic coupling 7 The vehicle speed is estimated based on the braking force application control unit 21 that applies a braking force for canceling the applied driving force, and the rotational speeds of the driven wheels (left and right rear wheels 4 and 5). And a driving slip suppression unit 22 that controls the driving force applied to each wheel 2 to 5 to prevent driving slip, and slips each wheel 2 to 5 little by little when traveling on an extremely low μ road or the like. Even when the vehicle is driven while the vehicle is running, it is possible to appropriately execute the control for suppressing the drive slip based on the accurately estimated vehicle speed.

  That is, in an all-wheel drive vehicle that drives both the front wheels 2 and 3 and the rear wheels 4 and 5, when a driver having excellent skills travels on an extremely low μ road, the wheels 2 to 5 are slightly changed. In a situation where the vehicle is driven while slipping, all the wheels 2 to 5 may slowly shift to a state where they are slipping simultaneously, and the most of the wheels 2 to 5 is conventionally performed. If the vehicle body speed is estimated on the basis of the rotational speed of the wheel having a low rotational speed, as shown in FIG. 5, the estimated vehicle speed Vp tends to gradually deviate from the actual vehicle speed Vr, and the drive slip is based on the estimated vehicle speed Vp. It is difficult to properly execute control for suppressing the above. In FIG. 5, a broken line S represents a target rotational speed at the time of slip control (traction control) for each of the wheels 2 to 5 set based on the estimated vehicle speed Vp.

  On the other hand, as shown in FIG. 6, at the time t1 when it is determined that the situation in which all the wheels 2 to 5 of the all-wheel drive vehicle slip is generated, the left and right front wheels 2 and 3 are driven wheels for a predetermined time T. The driving force distribution mechanism 6 is controlled so that the left and right rear wheels 4 and 5 are driven wheels, and the driving force input from the hydraulic coupling 7 to the left and right rear wheels 4 and 5 that are driven wheels is canceled. In the case where the braking force is applied, the occurrence of the situation where the estimated vehicle speed Vp gradually deviates from the actual vehicle speed Vr is effectively prevented, and based on the rotational speeds of the left and right rear wheels 4 and 5. Since the vehicle speed can be accurately estimated, there is an advantage that the driving slip of each wheel can be effectively prevented based on the estimated value of the vehicle speed.

  Moreover, in the said embodiment, while the rotational speed of all the wheels 2-5 is below the preset reference speed for a fixed time or more, the rotational speed of all the wheels 2-5 tends to increase. When it is confirmed by the slip condition determination unit 19 that there is a situation in which all the wheels 2 to 5 slip, it is determined that a driver having excellent skills can use an extremely low μ road, etc. It is possible to accurately determine whether or not all the wheels 2 to 5 are in a slip state at the same time under a situation where the vehicle is driven while slipping the wheels 2 to 5 little by little. . Therefore, it is possible to easily and accurately determine the occurrence of a situation in which the estimated vehicle speed Vp gradually deviates from the actual vehicle speed Vr when traveling on an extremely low μ road or the like, which has been difficult to determine in the past. There is an advantage that the driving slip of each wheel can be properly executed.

  Further, as shown in the above-described embodiment, at the same time as the driving force distribution control 20 performs the control to make the rear wheels 4 and 5 driven wheels, the braking force application control unit 21 applies a predetermined braking force to the rear wheels 4 and 5. In the situation where all the wheels 2 to 5 slip, the vehicle speed can be estimated quickly and accurately based on the rotational speeds of the left and right rear wheels 4 and 5. There is an advantage that the driving slip of each of the wheels 2 to 5 can be more effectively prevented based on the estimated value.

  Further, in the above-described embodiment, the temperature detection means including the temperature sensor 16 that detects the temperature of the driving force distribution mechanism 6 is provided, and the braking force is applied based on the temperature of the driving force distribution mechanism 6 detected by the temperature detection means. Since the controller 21 is configured to adjust the braking force applied to the rear wheels 4, 5 on the driven wheel side, it is transmitted to the left and right rear wheels 4, 5 according to the viscosity of the oil filled in the hydraulic coupling 7. The vehicle speed can be accurately estimated based on the rotational speeds of the left and right rear wheels 4 and 5 in a situation where all the wheels 2 to 5 slip by properly applying a braking force for canceling the drag torque that is generated. There are advantages.

  Further, as described above, the pressure increasing means provided with the hydraulic pump 27 for increasing the hydraulic pressure supplied to the brake devices 12 to 15 of the wheels 2 to 5 and the brake devices 12 to 15 side of the pressure increasing means are disposed. In addition, in the driving force control device including a brake pressure adjusting means including the control valve 45 for adjusting the hydraulic pressure supplied to the brake devices 12 to 15, the rear wheel 4 serving as a driven wheel by the braking force applying unit 21. , 5, when the braking force is applied, the hydraulic pump 27 is operated, and the hydraulic pressure supplied from the boosting means to the brake devices 14, 15 on the driven wheels (rear wheels 4, 5) by the brake pressure adjusting means. When the pressure is reduced, it is possible to prevent high pressure hydraulic pressure from being supplied to the brake devices 14 and 15. Therefore, the hydraulic pressure can be accurately finely adjusted so as to apply an appropriate braking force for canceling the drag torque transmitted to the driven wheel according to the viscosity of the oil filled in the hydraulic coupling 7. There are advantages.

  When it is determined that a situation in which all the wheels 2 to 5 slip is generated, the left and right rear wheels 4 and 5 are used as driven wheels, and a braking force is applied to the left and right rear wheels 4 and 5. Instead of the above embodiment configured as described above, it is also possible to execute a driving force distribution control using the left and right front wheels 2 and 3 as driven wheels and to apply a braking force to the left and right front wheels 2 and 3. . However, the brake devices 14 for the left and right rear wheels 4 and 5 are usually compared to the braking force applied to the left and right front wheels 2 and 3 by the brake devices 12 and 13 for the left and right front wheels 2 and 3 in terms of brake efficiency. 15, the braking force applied to the left and right front wheels 2 and 3 is often set to a low value.

  Therefore, in the vehicle in which the braking force is set as described above, when it is determined that a situation in which all the wheels 2 to 5 slip occurs, the left and right rear wheels 4 and 5 are moved by the driving force distribution control unit 20. By controlling the distribution of the driving force so as to be driven wheels, and by applying the braking force to the left and right rear wheels 4, 5 by the braking force application control unit 21, Correctly finely adjust the supplied hydraulic pressure and appropriately apply a braking force for canceling the drag torque transmitted to the left and right rear wheels 4 and 5 according to the viscosity of the oil filled in the hydraulic coupling 7 Thus, there is an advantage that the vehicle speed can be accurately estimated based on the rotational speeds of the left and right rear wheels 4 and 5 in a situation where all the wheels 2 to 5 slip.

It is explanatory drawing which shows embodiment of the driving force control apparatus which concerns on this invention. It is a hydraulic circuit diagram which shows the specific structure of a braking system. It is a flowchart which shows the control action by the said driving force control means. It is a graph which shows an example of the map for setting the target value of braking force. It is a time chart which shows the slip state in the comparative example of this invention. It is a time chart which shows the slip state in the example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2, 3 Front wheel 4, 5 Rear wheel 6 Driving force distribution mechanism 7 Hydraulic clutch 8-11 Wheel speed sensor 12-15 Brake device 16 Temperature sensor (temperature detection means)
DESCRIPTION OF SYMBOLS 17 Slip control means 18 Braking system 19 Slip condition determination part 20 Drive force distribution control part 21 Braking force provision control part 22 Drive slip suppression part 27 Hydraulic pump (pressure | voltage rise means)
28 Pump drive motor (pressure booster)
36 Cylinder for pressure increase (pressure increase means)

Claims (6)

  Drive provided with slip control means for preventing drive slip of each wheel due to excessive drive force being transmitted to the wheels of all-wheel drive vehicle, and hydraulic coupling for adjusting the distribution of drive force to the front and rear wheels A driving force control device having a force distribution mechanism, wherein the slip control means includes a slip condition determination unit that determines whether or not a situation in which all wheels slip is generated, and a situation in which all wheels slip. A driving force distribution control unit that controls the driving force distribution mechanism to control one of the front and rear wheels as a driving wheel and the other as a driven wheel for a predetermined period of time when all the wheels are determined to have occurred. Based on the rotation speed of the driven wheel, and a braking force application control unit that applies a braking force to cancel the driving force input from the hydraulic coupling to the wheel that is set as the driven wheel at the time of occurrence of a slipping situation. Estimating the vehicle speed converting mechanism, the vehicle speed estimate driving force control apparatus being characterized in that provided a drive slip suppression unit that performs control to suppress the driving slippage of each wheel based on.   The slip condition determination unit has confirmed that the rotation speeds of all the wheels are maintained for a predetermined time or more in a state where the rotation speeds of all the wheels are equal to or lower than a preset reference speed, and that the rotation speeds of all the wheels tend to increase. The driving force control device according to claim 1, wherein the driving force control device is configured to determine that a situation in which all the wheels slip is generated.   The driving force distribution control unit is configured to apply a braking force to the wheel on the driven wheel side by the braking force application control unit simultaneously with the execution of the control to make one of the front and rear wheels a driven wheel. Item 3. The driving force control device according to Item 1 or 2.   Temperature detecting means for detecting the temperature of the driving force distribution mechanism is provided, and the braking force applied to the wheel on the driven wheel side is adjusted by the braking force application control unit based on the temperature detected by the temperature detecting means. The driving force control apparatus according to any one of claims 1 to 3, wherein the driving force control apparatus is configured as described above.   A pressure increasing means having a hydraulic pump for increasing the hydraulic pressure supplied to the brake device of each wheel; a brake pressure adjusting means provided on the brake device side of the pressure increasing means and for adjusting the hydraulic pressure supplied to the brake device; When the braking force is applied to the driven wheel side wheel by the braking force applying unit, the hydraulic pump is operated, and the brake pressure adjusting means is supplied from the boosting means to the driven wheel side brake device. The driving force control apparatus according to any one of claims 1 to 4, wherein the hydraulic pressure is reduced.   There is a front wheel brake device that applies braking force to the front wheels, and a rear wheel brake device that applies lower braking force to the rear wheels than the braking force applied to the front wheels, causing a situation where all wheels slip. When it is determined that the driving force is distributed, the driving force distribution control unit executes the driving force distribution control with the rear wheel side as the driven wheel, and the braking force application control unit applies the braking force to the rear wheel. The driving force control apparatus according to any one of claims 1 to 5, wherein the driving force control apparatus is configured.

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