JP4968161B2 - Driving force control device - Google Patents

Description

  The present invention relates to a driving force control apparatus capable of controlling a driving torque generated between a wheel and a road surface and a brake torque applied to the wheel.

  Generally, a driving force source is mounted on a vehicle, and torque of the driving force source is transmitted to wheels, and driving torque is generated between the wheels and the road surface. Also, brake torque can be applied to the wheels. An example of a technique for controlling the drive torque generated at the wheel and the brake torque applied to the wheel is described in Patent Document 1.

  In the vehicle drive torque control device described in Patent Document 1, the drive device is connected to the left and right front wheels so that torque can be transmitted. The drive device includes an electric motor or an engine and includes a transmission. The torque of the driving device is controlled by the electronic control unit based on the depression amount of the accelerator pedal detected by the accelerator opening sensor. A differential is provided in the torque transmission path from the drive device to the left and right front wheels. Furthermore, in addition to the front wheels, left and right rear wheels are provided, and a braking device that applies brake torque to the front wheels and the rear wheels is provided. This braking device is not limited to the brake pedal operated by the driver, the wheel cylinders provided separately for the left and right front wheels and the left and right rear wheels, and the brake pedal depression amount or the brake pedal depression amount. And a hydraulic circuit for controlling the hydraulic pressure of the wheel cylinder.

  Then, when torque is transmitted from the driving device to the front wheels and driving torque is generated, if one of the left and right front wheels slips, the driving torque of the non-slipping wheel determines the slipping wheel. By subtracting the drive torque, the brake torque applied to the slipped wheel is obtained. As a result, the sum of the drive torque and brake torque in the slipped wheel becomes equal to the drive torque of the non-slip wheel, and the brake torque is given to the slipped wheel without excess or deficiency without requiring adaptation for each vehicle type. It is said that wheel slip can be reliably suppressed. Patent Document 2 describes a technology for suppressing wheel slip by controlling the engine speed when a wheel slip is detected in a vehicle configured to transmit engine torque to the wheel. Yes.

JP 2007-50753 A JP-A-4-166628

  However, in the drive control device described in Patent Document 1, there is a response delay in the brake torque applied to the slipped wheel, and the slip of the wheel is suppressed by reducing the drive torque of the slipped wheel. When the wheel slip is eliminated and the driving torque of the wheel is increased again, the wheel may eventually slip again, and the acceleration performance cannot be improved.

  The present invention has been made paying attention to the above technical problem, and can improve the acceleration of the vehicle when one of the first wheels or the second wheels slips. An object of the present invention is to provide a driving force control device.

  In order to achieve the above-mentioned object, the invention of claim 1 includes a first wheel and a second wheel arranged at different positions in the left-right direction or the front-rear direction of the vehicle, and the first wheel and the second wheel. A driving force source for transmitting torque to the wheel; and a braking device for applying a braking torque to the first wheel and the second wheel, wherein torque is transmitted from the driving force source to the first wheel. Driving torque generated between the first wheel and the road surface, braking torque applied to the first wheel by the braking device, and torque transmitted from the driving force source to the second wheel, the second The driving torque generated between the wheel and the road surface and the braking torque applied to the second wheel by the braking device can be individually changed between the first wheel and the second wheel. In the force control device When there is a difference between the slip amount of the first wheel and the slip amount of the second wheel, the maximum value of the drive torque generated in the wheel with the larger slip amount and the wheel with the smaller slip amount A calculating means for obtaining a difference from the maximum value of the driving torque, and a brake torque applied to the wheel having the larger slip amount based on a difference between the maximum values of the driving torque obtained by the calculating means. And brake torque control means.

  In addition to the structure of claim 1, the invention of claim 2 provides the brake torque applied to the wheel after the slip of the wheel with the larger slip amount is eliminated by the processing of the first brake torque control means. It further has a second brake torque control means for limiting the torque to a value equal to or less than the torque applied to the wheel from the driving force source.

  According to the first aspect of the present invention, when there is a difference between the slip amount of the first wheel and the slip amount of the second wheel, the maximum value of the drive torque generated in the wheel having the large slip amount and the slip amount are Find the difference from the maximum value of the driving torque of the small wheels. Next, the brake torque applied to the wheel having the large slip amount is controlled based on the difference between the obtained maximum values of the drive torque. For this reason, when the driving torque of a wheel with a large slip amount is temporarily reduced to eliminate the slipping of the wheel and then the driving torque of the wheel is increased, the driving torque does not slip until the driving torque reaches the maximum value. Therefore, the driving torque generated at the other wheel can be relatively increased. Therefore, the acceleration performance of the vehicle is improved.

  According to the invention of claim 2, in addition to obtaining the same effect as that of the invention of claim 1, if one wheel slips and then the wheel no longer slips, the total torque transmitted to the wheel The value does not become the value on the braking side, and the vehicle can be prevented from being decelerated more than the driver's intention.

  In this invention, the front-rear direction of the vehicle is a direction along the traveling direction of the vehicle, and the left-right direction of the vehicle is a direction orthogonal to the traveling direction of the vehicle. The driving force source in the present invention is a device that generates torque to be transmitted to the wheels and can control the torque. The driving force source includes an engine, an electric motor, a hydraulic motor, a flywheel, and the like. The engine is a power unit that burns fuel and converts the thermal energy into kinetic energy. As this engine, an internal combustion engine such as a gasoline engine, a diesel engine, or an LPG engine can be used. The electric motor is a power device that converts electric energy into kinetic energy, and a DC motor or an AC motor can be used as the motor. The hydraulic motor is a power device that converts fluid energy of oil into kinetic energy of a rotating shaft. The flywheel is a power device that converts the rotational inertia force of the rotating member into the kinetic energy of the output member and outputs the kinetic energy. In the present invention, the torque of the driving force source is distributed to the first wheel and the second wheel via the differential. For this reason, the rotational speed difference between the first wheel and the second wheel is absorbed by the differential. In the present invention, the driving torque generated between the wheel and the road surface can be rephrased as driving force. The first wheel and the second wheel in the present invention are drive wheels to which the torque of the drive force source is transmitted. The first wheel and the second wheel include a right wheel and a left wheel arranged at different positions on the left and right, or a front wheel and a rear wheel arranged at different positions in the front-rear direction. The magnitude relationship between the slip amounts of the wheels in the present invention is determined, for example, based on whether the wheels have slipped or the magnitude of the slip rate. The first brake torque control means and the second brake torque control means mean that the first brake torque control means and the second brake torque control means are means for controlling the brake torque.

  Next, an embodiment of the present invention will be described with reference to the drawings. The vehicle 1 shown in FIG. 1 is equipped with a driving force source 2 and is connected to an output shaft of the driving force source 2 and an input shaft of the transmission 3 so as to transmit torque. As the driving force source 2, at least one of an engine or an electric motor can be used. This engine can control the engine torque by controlling the fuel injection amount or the intake air amount ignition timing. The electric motor can control the output torque by controlling the current value. The transmission 3 is a power transmission device that can change the ratio between the input rotation speed and the output rotation speed, that is, the transmission gear ratio. As the transmission 3, either a continuously variable transmission or a stepped transmission is used. Also good. A continuously variable transmission is a continuously variable transmission, that is, a transmission that can be continuously changed, and a continuously variable transmission that uses a toroidal continuously variable transmission or a belt-type continuously variable transmission. Can do. On the other hand, a stepped transmission is a transmission in which the gear ratio can be changed stepwise, that is, discontinuously. As a stepped transmission, a selection gear type transmission, a constantly meshing transmission, a planetary gear, and the like. A gear transmission can be used.

  Further, a differential 4 is connected to the output side of the transmission 3 via a propeller shaft 20 so that power can be transmitted. The differential 4 includes a differential case provided rotatably, a pinion gear attached to the differential case, and two side gears meshed with the pinion gear. Axle shafts 5 and 6 are separately connected to the two side gears. The left rear wheel 7 is connected to the axle shaft 5 so that power can be transmitted, and the right rear wheel 8 can be transmitted to the axle shaft 6. It is connected. A left front wheel 9 is provided in front of the left front wheel 7 in the front-rear direction of the vehicle 1, and a right front wheel 10 is provided in front of the right front wheel 8 in the front-rear direction of the vehicle 1. Note that the torque of the driving force source 2 is not transmitted to the right front wheel 10 and the left front wheel 9. Each wheel is configured by attaching a tire mainly made of a rubber material to the outer periphery of a metal wheel.

  Further, a braking device 11 is provided that can individually control the brake torque applied to the right front wheel 10, the left front wheel 9, the right rear wheel 8, and the left rear wheel 7. The braking device 11 includes a brake pedal 12 operated by a driver, a wheel cylinder 13 provided on the right front wheel 10, a wheel cylinder 14 provided on the left front wheel 9, and a wheel provided on the right rear wheel 8. A cylinder 15, a wheel cylinder 16 provided on the left rear wheel 7, and a hydraulic circuit 17 capable of individually controlling the hydraulic pressure of the wheel cylinders 13, 14, 15, 16 are provided. The hydraulic circuit 17 is a known circuit having a master cylinder and a solenoid valve. The hydraulic circuit 17 is a hydraulic actuator and controls the oil pressure of the wheel cylinders 13, 14, 15, and 16 to individually control the right front wheel 10, the left front wheel 9, the right rear wheel 8, and the left rear wheel 7. The applied brake torque can be adjusted individually. Specifically, when the hydraulic pressure of the wheel cylinder is decreased, the brake torque applied to the wheel is decreased, and when the hydraulic pressure of the wheel cylinder is increased, the brake torque applied to the wheel is increased.

  In the vehicle 1 configured as described above, the required driving force in the vehicle 1 is determined based on the depression amount of the accelerator pedal and the vehicle speed, and the rotational speed and torque of the driving force source 2 are determined based on the required driving force. And the gear ratio of the transmission 3 is controlled. In the vehicle shown in FIG. 2, the torque of the driving force source 2 is transmitted to the axle shafts 5 and 6 via the transmission 3 and the differential 4. When torque is transmitted to the right rear wheel 8, as shown in FIG. 3, driving torque (driving force) is generated at the contact portion between the right rear wheel 8 and the road surface 19, and torque is transmitted to the left rear wheel 7. Then, a driving torque (driving force) is generated at the contact portion between the left rear wheel 7 and the road surface 19. Further, when the brake pedal 12 is depressed, the hydraulic pressure of the wheel cylinders 13, 14, 15, 16 is increased, and brake torque is applied to the right front wheel 10, the left front wheel 9, the right rear wheel 8, and the left rear wheel 7. Here, torque transmitted to each wheel, brake torque, and drive torque generated at each wheel will be described with reference to FIG. For example, when the vehicle 1 travels forward, counterclockwise torque is applied from the driving force source 2 to the right rear wheel 8 and the left rear wheel 7, and leftward driving torque is generated in FIG. On the other hand, the brake torque is applied to the right rear wheel 8 and the left rear wheel 7 in the clockwise direction in FIG. Further, in this embodiment, the brake torque applied to each wheel can be individually controlled when the accelerator pedal is depressed and the brake pedal 12 is not depressed. Therefore, a control example in the case where brake torque is applied to each wheel when the brake pedal is not depressed will be described.

(First control example)
In this first control example, the accelerator pedal is depressed to generate an acceleration request, and the torque of the driving force source 2 is transmitted to the right rear wheel 8 and the left rear wheel 7 so that the right rear wheel 8 and the left rear wheel 7 are transmitted. This is an example when a driving force is generated. First, the driving torque generated between the tire of the right rear wheel 8 and the road surface 19 and the driving torque generated between the tire of the left rear wheel 7 and the road surface 19 are calculated (step S1). In this step S1, for example, the following equation can be used.
Twr = (Td−IdVdd) Rg / 2−IwVwd−Tb (1)
Here, Twr is the driving torque for each wheel, Td is the torque of the driving force source 2, Id is the moment of inertia of the power transmission member, Vdd is the rotational acceleration of the power transmission member, and Rg is the gear ratio of the transmission 3 and the differential 4. , Iw is the inertia moment of the wheel, Vwd is the rotational acceleration of the wheel, and Tb is the brake torque applied to the wheel. The power transmission member includes the axle shafts 5 and 6 and the propeller shaft 20.

Following this step S1, it is determined whether or not slip has occurred on the wheels, specifically the rear wheels (step S2). Whether the wheel slips or not
Slip rate = ((wheel rotation speed−vehicle speed) / wheel rotation speed) × 100
For example, a known determination device described in JP-A-2003-204534, JP-A-2003-204536, JP-A-2003-20374, or the like may be used. If the determination in step S2 is affirmative, it is determined whether or not there is a non-slip wheel in the drive wheel (step S3). If either the right rear wheel 8 or the left rear wheel 7 is slipping and the other is not slipping, an affirmative determination is made in step S3. For example, when one drive wheel is in contact with a snowy road or a freezing road and the other drive wheel is in contact with a paved road, the determination is positive in step S3. And since the slip ratio of a wheel is larger than a predetermined value, it is judged whether the torque of the driving force source 2 was reduced (step S4).

  The technical meaning of step S4 will be described. In this embodiment, when the wheel slips, the brake torque is applied to the slipped wheel to reduce the slip ratio of the wheel, but when the slip ratio is larger than a predetermined value, the brake torque is applied. Since the wheel slip may not be suppressed, control for reducing the torque of the driving force source 2 is performed in addition to the application of the brake torque. When an affirmative determination is made in step S4, the maximum value of the drive torque generated between the tire of the non-slip wheel (high μ wheel) and the road surface 19 is stored in the electronic control unit 18 ( Step S5). Further, the maximum value of the driving torque generated between the tire of the slipping wheel (low μ wheel) and the road surface 19 is stored in the electronic control unit 18 (step S6). Either of the processes of step S5 and step S6 may be performed first, or may be performed simultaneously.

  The processing in steps S5 and S6 will be described with reference to the map of FIG. In the map of FIG. 4, the abscissa indicates the wheel slip ratio, and the ordinate indicates the drive torque. FIG. 4 shows the characteristics of the high μ wheel and the characteristics of the low μ wheel. The high μ wheel shows the characteristic of a wheel that does not slip, and the low μ wheel shows the characteristic of a wheel that slips. When the slip ratio is the same, the driving torque of the high μ wheel is higher than the driving torque of the low μ wheel. Note that the driving torque increases as the slip ratio increases, and the characteristic that the driving torque decreases when the slip ratio exceeds a predetermined slip ratio is common to the high μ wheel and the low μ wheel. As shown in FIG. 4, when slip occurs in the low μ wheel in step S5, the maximum value of the driving torque of the high μ wheel is stored. In step S6, the maximum value of the driving torque of the low μ wheel is stored. That is, what is stored in step S6 is not the actual driving torque of the slipped wheel. Next, the brake torque applied to the slipped wheel is calculated by subtracting the drive torque maximum value obtained in step S6 from the drive torque maximum value obtained in step S5 (step S7). That is, in step S7, the brake torque corresponding to the difference between the drive torques in FIG. 4 is obtained. And the signal which gives brake torque to the wheel which is slipping is output (step S8), and this control routine is complete | finished.

  On the other hand, if the slip ratio is equal to or less than a predetermined value at the time of determination in step S4, control for reducing the torque of the driving force source 2 is not performed, and a negative determination is made in step S4. Thus, if a negative determination is made in step S4, the braking torque applied to the slipping wheel is calculated by subtracting the driving torque of the wheel that is slipping from the driving torque of the wheel that is not slipping. (Step S9), the process proceeds to Step S8. Further, when the process proceeds to step S10 via step S3, the brake torque applied to the left and right rear wheels is determined so that both the left and right rear wheels do not slip. Further, when the process proceeds to step S10 via step S2, the brake torque applied to the left and right rear wheels is calculated based on the depression amount of the brake pedal 12. That is, in step S10, the brake torque applied to the wheels in the current routine is the same as the brake force applied to the wheels in the previous routine.

  As described above, either the right rear wheel 8 or the left rear wheel 7 slips and the other does not slip, and the brake torque application response in the slipping wheel is relatively low. In this case, the torque-down control of the driving force source 2 is performed, a positive determination is made in step S4, and the processes in steps S5, S6, S7, and S8 are performed. In other words, the brake torque applied to the slipped wheel is a value based on the maximum value of the drive torque. Therefore, the brake torque is applied to the stepped wheel to eliminate the slip of the wheel, and the torque of the drive force source 2 is again applied. When the brake torque is increased and the brake torque is reduced, the previously slipped wheel is less likely to slip this time. More specifically, since the drive torque at which the wheel has slipped does not slip, the current drive torque at the wheel that has not slipped at the previous time can be relatively increased. Therefore, the acceleration performance of the vehicle 1 can be improved.

  In the above specific example, the case where one wheel slips and the other wheel does not slip is described, but when both the left and right rear wheels slip, the slip ratio is relatively high and low. The flowcharts of FIGS. 1 and 5 can be executed separately for each wheel. In this case, in step S3, it is determined whether there is a difference between the slip ratios of the left and right drive wheels. If the determination in step S3 is affirmative, the process proceeds to step S4, and the determination in step S3 is negative. In this case, the routine proceeds to step S10. Here, the correspondence between the functional means shown in FIG. 1 and the configuration of the present invention will be described. The processing of steps S2, S3, S4, S5 and S6 in FIG. 1 corresponds to the calculating means of the present invention. The processes in steps S7 and S8 correspond to the first brake torque control means of the present invention.

(Second control example)
Next, a second control example including individual control of brake torque applied to each wheel when the accelerator pedal is depressed and the brake pedal 12 is not depressed will be described with reference to FIG. In particular, the second control example includes processing performed when the wheel slips to reduce brake torque and when the accelerator pedal depression amount is reduced after the wheel slip is eliminated. In the steps shown in FIG. 5, the same step numbers as those in FIG. In this second control example, if a negative determination is made in step S2, the brake torque applied to the slipped wheel in the previous routine and the torque transmitted to the slipped wheel from the driving force source were added. It is determined whether the value was less than zero Newton meters (step S11). “Transmission torque” shown in step S11 of FIG. 5 means the torque transmitted from the driving force source to the slipped wheel. If a negative determination is made in step S11, the process proceeds to step S10.

On the other hand, if the determination in step S11 is affirmative, the current brake torque applied to the previously slipped wheel is limited to the magnitude of the torque transmitted to the slipped wheel or less ( Step S12), the process proceeds to step S8. The process of step S12 is shown in FIG. 5 as brake torque output amount = −1 × transmission torque. Even in the second control example, the same processing portion as in the first control example can obtain the same effect as in the first control example. Further, in the second control example, when the wheel slips and then the wheel does not slip, and when the process proceeds from step S2 to step S12 via step S11, the total value of the torque transmitted to the individual wheels is calculated. Therefore, the braking side value is not set, and the vehicle 1 can be prevented from being decelerated more than the driver's intention. Further, the brake torque applied to the slipped wheel does not become more than necessary. Here, the correspondence between the functional means shown in FIG. 5 and the configuration of the present invention will be described. The processing of steps S2, S11, and S12 corresponds to the second brake torque control means of the present invention.

  The vehicle 1 shown in FIG. 2 is a two-wheel drive vehicle configured such that the torque of the driving force source is transmitted to the rear wheels, but the control of FIGS. It can also be implemented in a two-wheel drive vehicle configured to be transmitted to the front wheels. In this case, in the above description, the right rear wheel 8 may be read as the right front wheel 10, and the left rear wheel 7 may be read as the left front wheel 9. Furthermore, the present invention can also be used in a four-wheel drive vehicle having a configuration in which the torque of the driving force source is distributed to the front wheels and the rear wheels via the transfer and the center differential. In this case, in the description of the flowcharts of FIGS. 1 and 5, the right rear wheel and the left rear wheel may be read as the front wheel and the rear wheel. That is, based on the difference between the slip ratio of the front wheels and the slip ratio of the rear wheels, the torque transmitted from the driving force source to the front wheels and the rear wheels is controlled, and the brake torque applied to the front wheels and the rear wheels is controlled from the braking device. By doing so, the slip of a wheel can be suppressed and acceleration performance can be improved.

  The brake device shown in FIG. 2 has a structure in which brake torque is generated by a hydraulic actuator, but the present invention can also be applied to a vehicle having a brake device that generates brake torque by electromagnetic force. Furthermore, in this specific example, an accelerator pedal that is operated by the driver's foot is used to determine the acceleration request for the vehicle, but based on the operation amount of the lever, knob, switch, etc. that the driver operates by hand. Thus, the present invention can also be implemented in a vehicle that determines an acceleration request for the vehicle. Furthermore, in this specific example, in order to determine the braking request for the vehicle, a brake pedal that the driver operates with his / her foot is cited, but based on the operation amount of a lever, knob, switch, etc., which the driver operates with his hand. Thus, the present invention can also be implemented in a vehicle that determines a braking request for the vehicle.

It is a flowchart which shows the 1st example of control which can be performed with the driving force control apparatus of this invention. It is a conceptual diagram of the vehicle used as the object of the driving force control apparatus of this invention. It is a conceptual diagram which shows the torque in the wheel shown by FIG. It is a map which shows the relationship between the slip ratio of a wheel shown by FIG. 2, and drive torque. It is a flowchart which shows the 2nd example of control which can be performed with the driving force control apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Driving force source, 7 ... Left rear wheel, 8 ... Right rear wheel, 11 ... Braking device, 19 ... Road surface.

Claims (2)

A first wheel and a second wheel disposed at different positions in the left-right direction or the front-rear direction of the vehicle; a driving force source for transmitting torque to the first wheel and the second wheel; and the first wheel And a braking device for applying a braking torque to the second wheel, the driving torque generated between the first wheel and the road surface when torque is transmitted from the driving force source to the first wheel, and Brake torque applied to the first wheel by a braking device, driving torque generated between the second wheel and the road surface when torque is transmitted from the driving force source to the second wheel, and the braking device In the driving force control device capable of individually changing the brake torque applied to the second wheel by the first wheel and the second wheel,
When there is a difference between the slip amount of the first wheel and the slip amount of the second wheel, the maximum value of the drive torque generated in the wheel with the larger slip amount and the drive of the wheel with the smaller slip amount A calculating means for obtaining a difference from the maximum value of the torque;
And a first brake torque control means for controlling the brake torque applied to the wheel having the larger slip amount based on the difference between the maximum values of the drive torque obtained by the calculation means. Driving force control device.   After the slip of the wheel having the larger slip amount is eliminated by the processing of the first brake torque control means, the brake torque applied to the wheel is a value equal to or less than the torque applied to the wheel from the driving force source. The driving force control device according to claim 1, further comprising second brake torque control means for limiting to the above.

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