JPH03148380A - Running control device for vehicle - Google Patents

Abstract

PURPOSE:To enhance the turning performance of a vehicle by strengthening the steering inclination of a rear wheel steering mechanism toward the side of an anti-phase according to the actuation frequency of a drive torque reducing means driven to cancel the acceleration slip of each driving wheel when the vehicle is detected to be cornering. CONSTITUTION:In a four-wheel drive vehicle which is equipped with a rear wheel steering mechanism (c) allowing rear wheels to be steered in addition to front wheel steering, and is also equipped with a drive torque reducing means (a), the drive torque of driving wheels is reduced by the drive torque reducing means (a) based on a slipping condition between the driving wheels and the road surface when the acceleration slip of the vehicle occurs so that the slip between the driving wheels and the road surface is thereby cancelled. In this case, a cornering condition judging means (b) judging whether or not the vehicle is cornering, is provided. And when the vehicle is detected to be cornering, the aforesaid rear wheel steering mechanism (c) is controlled by a control means (d) to more strengthen the steering inclination of the rear wheel steering mechanism (c) toward the side of a reverse phase as the activation frequency of the drive torque reducing means (a) is higher.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vehicle capable of steering front wheels and rear wheels, and which controls the drive torque to the drive wheels according to the acceleration slip state of the vehicle, such as internal combustion control. The present invention relates to a vehicle travel control device that controls the output of an engine. Conventional technology In general, when a vehicle accelerates, the friction force between the drive wheels and the road surface is optimized to obtain sufficient acceleration while preventing the wheels from slipping and causing the vehicle body to skid or other unstable conditions. However, in this type of control device, drive shaft output torque reduction means such as means for reducing fuel consumption or delaying ignition timing, or means for controlling the amount of intake air to the internal combustion engine are known. It has been known. For example, JP-A-61-85248 and JP-A-61-
Japanese Patent No. 85249 discloses a drive torque reducing means for preventing the slippage of the drive wheels that occurs when the vehicle accelerates, and includes a drive torque reducing means provided in the intake passage upstream of the first throttle valve or linked to the accelerator pedal. A configuration is disclosed that includes opening/closing control means for a second throttle valve provided on the downstream side. Further, similar driving force control means for front wheel drive vehicles are disclosed in Japanese Patent Application Laid-open Nos. 63-309744 to 309748. In addition to reducing the engine output shaft torque, means for reducing the driving torque by applying braking to the driving wheels is also generally known as a driving torque reducing means. With this configuration, when acceleration slip occurs, the driving force transmitted from the internal combustion engine to the drive wheels via the drive shaft is
By controlling the drive torque reducing means, rotation of the drive wheels can be suppressed, and slips caused by acceleration can be prevented. Problems to be Solved by the Invention However, when such a conventional vehicle travel control device is applied to a front wheel drive vehicle, it is necessary to prevent acceleration slippage and slippage of the drive wheels when the vehicle starts or accelerates. However, as the vehicle speed increases when turning at high speed, the grip force of the front wheels, which is determined by the speed of the vehicle relative to the turning radius, reaches its limit, and the vehicle may drift out. There was a concern. On the other hand, there are also known vehicles that prevent the above-mentioned drift-out phenomenon by providing a steering mechanism not only for the front wheels but also for the rear wheels to change the steering characteristics of the front and rear wheels. In this case, for example, when driving on a low-friction road surface, the acceleration slip of the drive wheels increases, the lateral force decreases, and running stability tends to decrease, and the driving force of the wheels decreases. There was a problem in that acceleration performance could deteriorate due to Therefore, the present invention is directed to such a conventional vehicle travel control device,
In particular, it is possible to solve the problems that front and rear wheel steering vehicles have, and prevent the vehicle from drifting out even when the vehicle is turning at high speed, and also prevent a decrease in the driving force of the wheels. The purpose of this invention is to provide a vehicle running control device. Means for Solving the Problems In order to achieve the above object, the present invention provides a rear wheel steering system which enables steering of the rear wheels in addition to steering of the front wheels, as shown in the diagram corresponding to the claims in FIG. 11c, which prevents slip between the drive wheels and the road surface by a drive torque reducing means a that reduces the drive torque of the drive wheels based on the slip state between the drive wheels and the road surface when the vehicle accelerates and slips. In the vehicle running control device, when the turning state determining means detects that the vehicle is turning, the turning state determining means determines whether the vehicle is in a turning state. The vehicle running control system is provided with a control means d that controls the rear wheel steering mechanism C so that the tendency to steer the rear wheel steering mechanism C toward the opposite phase side becomes stronger as the frequency of operation of the drive torque reduction means a increases. According to this structure, when acceleration slip occurs in the drive wheel, the drive torque to the drive wheel is reduced based on the action of the drive torque reducing means a, the rotation of the drive wheel is reduced, and the slip is reduced. can be avoided. On the other hand, when the turning state determining means detects that the vehicle is turning, the control means d controls the rear wheel steering so that the steering direction of the iC is in the opposite phase to the steering direction of the front wheel steering mechanism. The rear wheel steering mechanism C is controlled to have a stronger tendency to steer toward the opposite phase side as the drive torque reduction means a is operated more frequently. Therefore, when turning at high speed when the vehicle is likely to drift out, steering the rear wheels so that they tend to be in the opposite phase to the front wheels increases the turning ability of the vehicle and prevents the vehicle from drifting out. is obtained. Embodiment Hereinafter, one embodiment of the vehicle travel control device according to the present invention will be described in detail with reference to the drawings. Note that the vehicle in this embodiment is a front-wheel drive vehicle. In the schematic diagram shown in FIG. 2, 1 is a steering wheel, 3 is a steering shaft, and a steering angle sensor 4 is attached to the steering shaft 3 as a turning state determining means that emits a pulse signal according to the steering angle. ing. Reference numeral 5 denotes a gear box for a front rotary boat, and a motion direction changing mechanism such as a rack and pinion is built in the gear box 5. Knuckle arms 9 are pivoted to both ends of a tie rod that protrudes from the gear box 5 in the vehicle width direction.
, 9 are respectively pivotally supported on pivot shafts 1-3a and 14a of a left front wheel 13 and a right front wheel I4 as driving wheels. On the other hand, 17 is an actuator for steering the rear wheels, and an output shaft 17a derived from this actuator 17 is connected to a gear box 19 on the rear wheel side. Inside this gear box 19, there is a rack &
A tie loft 2 that has a built-in motion direction conversion mechanism such as a binion and protrudes from this gear box 19 in the vehicle width direction.
The frame arm 23.23 pivoted on both ends of the left rear wheel 15 and the right rear wheel 16 as driven wheels
, 16a, respectively. Gear box 50 above. The tie loft 21 and the knuckle arms 23, 23 constitute a rear wheel steering mechanism 50. Further, rotation speed sensors 25 and 27 are attached to the left front wheel 13 and right front wheel 14 to detect the rotation speed of each wheel as a pulse signal, and the left rear wheel 15 and right rear wheel 16 also have rotation speed sensors 25 and 27 that detect the rotation speed of each wheel as a pulse signal. Several sensors 29, 31 are attached. Reference numeral 33 denotes a control circuit incorporating a CPU, and the control circuit 33 includes the rotation speed sensors 25, 2F. 29. Signal lines 25a, 2 taken out from 31, respectively.
7a, 29a, 31a and a signal line 4a taken out from the steering angle sensor 4 are connected, and a signal line 33a output from the control circuit 33 is connected to the actuator 17. The rotational speed sensor 25, 27, 29, 31 and the control circuit 33 constitute a slip state amount calculating means for calculating the slip state amount of the vehicle. On the other hand, 35 is an intake passage that supplies fuel to an engine (not shown), and a first throttle valve 37 and a second throttle valve 39 are arranged in parallel inside the intake passage 35. . The second throttle valve 39 may be located either upstream or downstream of the first throttle valve 37. This second throttle valve 39 constitutes a drive torque reducing means that reduces the output torque of the engine to reduce the drive torque of the left front wheel 13 and the right rear wheel 4. Reference numeral 41 denotes an accelerator pedal operated by the driver, and the opening degree of the first slit valve 37 is controlled by the accelerator pedal 41. Reference numeral 43 denotes a step motor for opening and closing the second slit throttle valve 39. A signal line 33b output from the control circuit 33 is connected to this step motor 43, and the operation of this step motor 43 causes The open/close state of the second throttle valve 39 is controlled. According to this configuration, as a basic operation, first, the left front wheel 1
3 and rotation speed sensors 25, 27 provided on the right front wheel 14
The signals obtained from the rotational speed sensors 29 and 31 provided on the left rear wheel 15 and the right rear wheel 16 are input to the control circuit 33, and the control circuit 33 determines the opening target value of the second throttle valve 37. is calculated, and a drive signal corresponding to this target opening value is input to the step motor 43 via the signal line 33b. The driving force of the step motor 43 drives the second throttle valve 39 disposed in the intake passage 35 to open and close, thereby controlling the driving torque of the engine. Therefore, when the slip state quantity calculating means detects that the vehicle is slipping or slipping, the rotational output of the engine is reduced by setting the opening target value of the second throttle valve 39 to fully closed. and the slip can be avoided. On the other hand, when it is determined that the vehicle is turning based on a signal obtained from the steering angle sensor 4 attached to the steering shaft 3, this signal is transmitted to the control circuit 3.
3, a rear wheel steering correction amount is calculated based on a calculation means built in the control circuit 33, which will be described later, and a drive signal corresponding to this rear wheel steering correction amount is sent to the actuator 17 via a line 33a. is man-powered. Then, the driving force of this actuator 17 is transferred from the gear box 19 to the tie loft 21. Tsukuru arm 23.23
The signal is transmitted to the left rear wheel 15 and the right rear wheel 16 through a rear wheel steering mechanism 50 consisting of the following: The steering is corrected by an angle corresponding to the rudder correction amount. At this time, the control circuit 33 controls the rear wheels so that the higher the frequency of operation of the second throttle valve 39 serving as the driving torque reducing means, the stronger the tendency of the rear wheel steering mechanism 50 to steer the rear wheel steering mechanism 50 to the opposite phase side. The operation of the steering mechanism 50 is controlled. Therefore, when the vehicle is making a high-speed turn where it is likely to drift out, the rear wheels 15, 16 are steered so that the tendency toward the opposite phase side becomes stronger, which increases the turning ability of the vehicle and prevents the vehicle from drifting out. You can get the effect of being Next, referring to FIG. 3, the actual control by the control circuit 33 will be explained in detail as a flowchart. Note that the processing within the main routine shown here is a fixed-time interrupt processing driven at a predetermined cycle (for example, 20 m5ec) by an operating system (not shown). In the same figure, when the engine key is inserted into the key cylinder and the ignition switch is turned from off to on, the microcomputer is powered on and a fixed time interrupt starts (step 100). It is determined whether it is the first flow after that, and if it is the first, a start signal is applied to step 102, and initialization processing such as clearing the memory built in the control circuit 33 is performed. Note that if it is not the first flow, the above initialization process is omitted and the process immediately proceeds to step 113. In step 103, wheel speeds V and L are calculated based on the rotational speed detected by the rotational speed sensor 25 of the left front wheel 13 as the slip state amount calculation means. Wheel speed V□ calculated based on the rotation speed detected by the right front wheel rotation speed sensor 27, rotation speed sensor 2 of the left rear wheel 15
Wheel speed v calculated based on the rotational speed detected in step 9
, L, the wheel speed V□ calculated based on the rotation speed detected by the rotation speed sensor 31 of the right rear wheel 16, and the steering angle θ detected by the steering angle sensor 4 are read. Next, in step l (14, the slip rate S as the slip state quantity between the tire and the road surface is calculated from the wheel speed of each wheel read in step 103 as follows: 3 = (V F V J / V F .However, L V F= ff F11+ V FL) /
2Vm=(Vmm+Vmt,)/2 That is, v, , vll are respectively the average wheel speeds of the front wheels and the rear wheels. Next, in step lO5, the slip ratio S obtained in step 104 is set to a set value S (for example, S, = 0-1).
It is determined whether or not the acceleration slip is greater than , and if it is larger, it is assumed that an acceleration slip has occurred and the process proceeds to step 106, whereas if it is smaller, it is assumed that an acceleration slip has not occurred and the process proceeds to step 107. In step 106, a command signal is issued via the signal line 33b to the step controller 431 to close the second throttle valve 39. Therefore, the second throttle valve 39 serving as a drive shaft output torque reducing means is closed, so the output to the drive wheels is reduced and acceleration slip of the vehicle is suppressed. Further, in the next step 10g, as will be described later, 1 is added to a counter for correcting the amount of steering of the rear wheels, and the non-slip timer is cleared, and the process proceeds to step 112. In step 1O1, since no acceleration slip has occurred in the vehicle, a command signal to release the second throttle valve 39 is issued to the step 1 motor 43 via the signal line 33b, and the steering amount is corrected. 1 is subtracted from the counter. Therefore, the second throttle valve 39 serving as drive shaft output torque reducing means opens, and the output torque of the drive shaft is restored to its normal state. Furthermore, in the next step 109, a non-slip timer indicating a non-slip state of the vehicle is set for a predetermined time T. For example, it is determined whether 3 seconds have elapsed or not, and if not, the process proceeds to step 110, where 1 is added to the non-slip timer, and the process proceeds to step 112. Further, when the non-slip timer has elapsed T01+ee in step 109, the process proceeds to step 109, where the counter for correcting the amount of steering of the rear wheels is cleared, and the process proceeds to step 1.
Proceed to step 12. Next, in step 112, the vehicle speed, especially the rear wheel speed v, j11
1 and the first rear wheel steering correction amounts δ,' are determined. In this example, as shown in the graph shown in the figure, when the rear wheel speed, that is, the vehicle speed is high, δ,' is on the same phase side as the front wheel steering direction (i.e., δ, > O
), and when the rear wheel speed is low, δ1' is set to be 11 m (δ,<o) opposite to the steering direction of the front wheels. Therefore, when the rear wheel speed is low, the steering direction of the rear wheels is opposite to the steering direction of the front wheels, so that the turning ability of the vehicle is improved. Next, in step 113, it is determined whether the absolute value 1θ1 of the steering angle θ detected by the steering angle sensor 4 serving as the vehicle turning state determination means is greater than or equal to the set value θ (for example, 10 degrees as θ), that is, the vehicle is turning. If it is determined that the vehicle is turning, the amount of steering is counted, and then the vehicle crawls to step y step 114. If it is determined that the vehicle is not turning, The process proceeds to step 115. In addition to the steering angle sensor 4 attached to the steering wheel l, the left front wheel 1 is used as a means for determining the turning state of the vehicle.
The turning state may be determined based on the difference in wheel speed between the right front wheel 14 and the right front wheel 14. - In step 114, the second rear wheel steering correction amount δ,'(δ,<o) is determined from the value of the counter for correcting the steering amount, and the process proceeds to step 116. In this example, the count value is set to become thicker as the time for reducing the output torque of the drive shaft in step 10g becomes thicker, and the amount of the opposite phase of the second rear wheel steering correction amount 62' becomes larger. has been done. In other words, the second rear wheel steering correction amount is determined such that the higher the frequency of operation of the drive torque reducing means, the stronger the tendency of the rear wheels to steer to the opposite phase side with respect to the front wheels. In this way, the larger the counter value, the stronger the tendency of the rear wheels toward the opposite phase side to be steered, thereby making it possible to improve the lateral direction of the vehicle. If it is determined that the vehicle is in a non-turning state, that is, in a straight-ahead state, the second rear wheel steering correction amount δ,' is set to 0 in step y step 115, and the process proceeds to step 1 step 116. . In step 116, the first and second rear wheel steering correction amounts δ1 determined in step l12 and step 114 above,
From δ, ′, the rear wheel steering total correction amount δ′ is δ′=δ, ′+δ,
' Then, in the next step 117, the rear wheel turning amount δ is calculated from the front wheel steering angle θ and the rear wheel turning total correction amount δ'.
is calculated as δ=θ+δ (where is a positive constant). In other words, when the vehicle is traveling straight, the rear wheels are steered by the front wheel steering angle calculated as θ + 61' to δ = and the steering angle determined by the vehicle speed (same phase except at very low vehicle speeds), while when the vehicle is turning, the counter value is Based on (by the second rear wheel steering correction amount δ,′,
The steering angle is corrected to tend toward the opposite phase side. By repeating such an interrupt flowchart, the steering amount δ of the rear wheels is determined, and the rear wheels 15 and 16 are steered via the steering mechanism. In the above description, the first throttle valve 3 is used as a drive torque reducing means for reducing the output torque of the drive shaft.
Although a means for reducing the engine output is shown using the second throttle valve 39 installed in parallel with the throttle valve 7, it is also possible to use means for controlling the amount of fuel supplied to the engine or controlling the ignition timing in addition to such means. be. In addition to the means for reducing the output of the engine, a braking control means for reducing the driving torque by means of a brake may be used. Furthermore, as a reference value for determining the slip rate S, for convenience, S@=
Although the slip ratio is set to 0.1, this slip ratio is determined by the vehicle, engine, etc., and can be changed freely. Further, although the step motor 43 is used as a means for opening and closing the second throttle valve 39, the step motor 4
A DC motor or servo motor may be used instead of 3. Furthermore, as a drive torque reduction means for preventing sliplift during vehicle drive, a throttle valve opening/closing means and an engine ignition timing or fuel supply amount control mechanism or braking control means may be used in combination. It's coming. In the above embodiment, the slip rate S was used as the slip state quantity for determining the degree of slip, but instead of this, the slip amount VRVF was used, each set value was determined accordingly, and similar control was performed. You can. Further, in this embodiment, the amount of steering correction for the rear wheels is determined based on the speed of the rear wheels, but the amount of steering correction may also be determined using the acceleration or lateral acceleration of the vehicle as a factor. Effects of the Invention According to the vehicle travel control device according to the present invention, which has been explained in detail above, the following effects are brought about. That is, when it is detected that acceleration slip has occurred in the drive wheel, the drive torque to the drive wheel is reduced based on the action of the drive torque reduction means, and the rotation of the drive wheel is reduced to avoid the slip. can do. On the other hand, when the turning state determining means detects that the vehicle is turning, the control means causes the rear wheel steering mechanism to shift to the opposite phase side as the drive torque reducing means operates more frequently. is controlled so that the steering tendency is strengthened. Therefore, when it is detected that the vehicle is making a high-speed turn where it is likely to triad out, the more frequently the drive torque reduction means is operated, the more the steering tendency of the rear wheel steering mechanism will be in the opposite phase to the steering direction of the front wheels. Since it is strengthened toward the side, the turning performance of the vehicle is improved and it is possible to prevent the vehicle from drifting out. Therefore, the triad-out prevention effect based on the steering characteristics of conventional front and rear wheel steering vehicles is further improved, and the ground contact force of the front wheels is not weakened by the action of the torque reduction means even during normal driving. For example, when driving on a low-friction road surface, there is no reduction in driving stability due to a decrease in the driving force and lateral force of the vehicle, and it is possible to maintain good acceleration performance.

[Brief explanation of the drawing]

FIG. 1 is a complaint response diagram of the vehicle cruise control device according to the present invention, FIG. 2 is a schematic diagram showing an embodiment of the vehicle cruise control device, and FIG. 3 is a flowchart showing an actual example of the same cruise control. . 1... Steering wheel, 3... Steering shaft, 4... Steering angle sensor (turning state determination means)
, 5.19...Gear box, 13...Left front wheel, 1
4-- Front right wheel, 15- Rear left wheel, 16... Rear right wheel, 2
5.27, 29.31... - Number of revolutions 7, 33...
control circuit, 35...intake passage, 37...-first throttle valve, 39...second throttle valve (driving torque reducing means), 41...accelerator pedal, 43...step motor, Figure 1 1C)

Claims (1)

[Claims] (1) A vehicle equipped with a rear wheel steering mechanism to enable rear wheel steering in addition to front wheel steering, and the drive torque of the drive wheels based on the slip condition between the drive wheels and the road surface when the vehicle accelerates and slips. By means of a drive torque reduction means that reduces
A vehicle travel control device that prevents slip between drive wheels and a road surface, including a turning state determining means for determining whether or not a vehicle is in a turning state, and a turning state determining means that determines whether the vehicle is in a turning state. The vehicle is characterized in that it is provided with a control means for controlling the rear wheel steering mechanism so that the higher the operating frequency of the drive torque reduction means is detected, the stronger the tendency of the rear wheel steering mechanism to steer toward the opposite phase side. Travel control device.