JPH0314772A - Course change preventive device for car in braking - Google Patents

Abstract

PURPOSE:To prevent unintentional change in the course of a car due to the braking torque difference between the left ad right wheels by sensing the braking torque difference, and controlling the aid steering angle so as to offset the yaw moment originating from the braking torque difference. CONSTITUTION:A car A is equipped with a device B for aid steering of either or both of the front and rear wheels independently from main steering on the front wheels. The braking torque difference between the left and right wheels is sensed by a means C. The aid steering device B is controlled by a means D so as to offset the yaw moment originating from the braking torque difference thus sensed. At this time, control is so made as to decrease the amount of the aid steering angle in the region where the amount of main steering is large. This prevents unintentional change in the course of the car A due to the braking torque difference, which should eliminate giving an anxious sense to the driver.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for preventing course changes during braking of a vehicle.

(Prior art) When a vehicle accelerates or decelerates while turning, the course inevitably changes to the inside or outside of the turning direction, although this differs depending on whether the front wheels or rear wheels are driven. Utility Model Publication No. 57-19172, Japanese Patent Application Publication No. 57-6
As described in Japanese Patent No. 0974, a technique has been proposed in which the rear wheels are assisted in steering to counteract the above-mentioned course changes during acceleration and deceleration during cornering.

(Problems to be Solved by the Invention) However, none of these methods could prevent the course of the vehicle from changing due to the difference in braking torque between the left and right wheels when braking the vehicle.

The difference in braking torque between the left and right wheels is determined by the variation in the friction coefficient of the brake pads and the road surface 1i between the left and right wheels! Caused by the difference in friction coefficient,
This difference in braking torque disturbs the course of the vehicle, and the driver notices this change in course particularly when braking while the vehicle is traveling straight.

Incidentally, as shown in Fig. 11, ΔF t (FrL
>F rR), and the left and right rear wheels are 2L. 2H braking torque reaction force F rL+F. are the same, the vehicle receives a counterclockwise yaw moment ψf around the center of gravity C and is changed course to the left. Further, as shown in FIG. 12, the braking torque reaction forces FfL and Ffll of the left and right front wheels are the same, and the braking torque reaction force FrL. of the left and right rear wheels is the same. Fril is Δ
When the difference is F2 (Frt>Fra), the vehicle receives a counterclockwise yaw moment ψ around the center of gravity C and is changed course to the left.

When such a course change occurs, the driver must operate the steering wheel to correct this change, which is troublesome.
Above all, it gives the driver a sense of anxiety.

Moreover, the above-mentioned tendency becomes stronger as the vehicle speed is higher and as the braking is more sudden.

An object of the present invention is to solve the above-mentioned problems by proposing a device that performs auxiliary steering according to the difference in braking torque between left and right wheels.

(Means for Solving the Problems) For this purpose, the device of the present invention is provided with an auxiliary steering device for auxiliary steering of at least one of the front wheels and the rear wheels, in addition to the main steering of the front wheels, as shown in the concept in FIG. The vehicle is equipped with a braking torque difference detection means for detecting a braking torque difference between left and right wheels, and an auxiliary steering angle control means for operating the auxiliary steering device to cancel the yaw moment accompanying this braking torque difference. It is what it is.

(Operation) The auxiliary steering angle control means operates the auxiliary steering device to perform predetermined auxiliary steering so as to cancel the yaw moment caused by the braking torque difference between the left and right wheels detected by the braking torque difference detection means.

Therefore, even if there is a restraining torque difference between the left and right wheels, the vehicle is prevented from changing its course by the auxiliary steering, thereby eliminating problems such as giving the driver a sense of anxiety.

(Example> Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which IL and IR indicate left and right front wheels, and 2L and 2R indicate left and right rear wheels. Left and right front wheels IL, I
R is steering gear 4 by steering wheel 3.
main steering is possible via the

In order to enable auxiliary steering of the front wheels IL and IR separately from the main steering, the steering gear 4 is not fixed to the vehicle body but is supported as a whole so that it can be stroked in the left and right direction.

In order to perform this stroke, the actuator 5 is installed between the steering gear 4 and the vehicle body 6. The actuator 5 has built-in springs 5a and 5b to resiliently support the steering gear 4 in a neutral position where the front wheels are not assisted, and when pressure is supplied to the chamber 5C or 5d, moves the steering gear 4 to the right or to the right by a distance corresponding to the pressure. It is assumed that by stroking to the left, the front wheels are auxiliary steered to the left or right by a corresponding angle.

The pressure in the actuator chambers 5c, 5d is controlled by a spring center type electromagnetic proportional pressure control valve 7, which is connected to a pressure source supply circuit 10 and a drain circuit 11 consisting of a pump 8 and a reservoir 9, and to the actuator chambers 5c, 5d. be inserted between. Is valve 7 a double solenoid? a, 7b OFF
When both the chambers 5c and 5d are in a pressure-free state, the solenoid 7a is
When the solenoid 7b is turned on, a pressure proportional to the drive current 1fL is generated in the chamber 5C, and when the solenoid 7b is turned on, a pressure proportional to the drive current trt is generated in the chamber 5d.

Current 1 fL. lf& are controlled by a controller 12, which includes brake rotors 13L, 13R for left and right front wheels and torque arms 14L,
Braking torque ε of the brake unit consisting of 14R,
、． ε. Enter. These braking torques are measured by strain gauges 15L, 15 attached to torque arms 14L, 14R.
Detected by R.

The controller 12 executes the control program shown in FIG. 3 based on this input information. First, in step 31, the braking torque εfL+ ε of the left and right front wheels is determined. Load and next step 3
2, the difference Δε,=εfL−εf, between these braking torques is calculated. In the next step 33, this braking torque difference Δε,
Check whether is positive or negative. If Δε,≧0, that is, the left front wheel braking torque ε,, is the right rear wheel braking torque ε. If it is determined that the above is the case, the current 1fL is set to 0 in step 34, and the current 1fL is set to 0 in step 35, as shown in FIG. A current 118 corresponding to the braking torque difference Δε is looked up from the corresponding table data, and in step 36 this 1 is output to the renoid 7b. By the way, FIG. 4 shows the current value 1 fl (1 fL) for obtaining the front wheel auxiliary steering amount that cancels out the yaw moment caused by the braking torque difference Δε, and for the corresponding Δε, 20, from the point mentioned above with respect to FIG. As is clear, a yaw moment ψ is generated in the counterclockwise direction, so in order to cancel this yaw moment, it is necessary to perform auxiliary steering of the front wheels to the right, so ire is applied.

Conversely, if it is determined in step 33 that Δε' is 0, that is, if the right front wheel braking torque ε,l is larger than the left front wheel braking torque ε,, then In+ is set to 0 in step 37, and the process shown in FIG. 4 is performed in step 38. A current 1fL corresponding to the braking torque difference Δε is looked up from the corresponding table data, and in step 39 this Irt is output to the solenoid 7a.

The current 1 fl or 1 ft is applied to the solenoid 7b of the pressure control valve 7.
or 7a, a pressure proportional to the current is generated in the chamber 5d or 5c, and the front wheels are auxiliarily steered to the right or left through the stroke of the steering gear 4. This cancels out the yaw moment caused by the braking torque difference Δε, and prevents the course of the vehicle from changing due to the braking torque difference.

5 and 6 show another example of the present invention, and in this example, a steering angle sensor l6 is added to the system of FIG. 2 as shown in FIG. This sensor 16 detects the steering angle θ of the steering wheel 3 and inputs the detected value to the controller 12, which executes the control program shown in FIG. 6 corresponding to FIG. 3.

That is, in step 31, the steering angle θ is also read, and in step 32, the braking torque difference Δ1,=εfL−ε. seek. Next, step 61 added in this example. At step 62, a correction coefficient k is looked up from the steering angle θ based on the table data corresponding to FIG. , is calculated using Δε, Δτ, ·k. By the way, as shown in FIG. 7, the correction coefficient k is 1 near the neutral position near the steering angle θ = 0, and rapidly decreases in other turning conditions, so that the auxiliary steering for preventing the course change is mainly performed during straight-ahead braking. Therefore, it is possible to prevent erroneous auxiliary steering in the direction of increased steering in response to the fact that the braking torque of the outer wheel becomes relatively larger than that of the inner wheel, which tends to lock in a turning state.

Figures 8 and 9 show not only the front wheels 1L and 1R but also the rear wheels 2.
An example in which auxiliary steering is also applied to L and 2R is shown. Therefore, in this example, the rear wheel 2L. 2R to actuator 1
7 enables steering, and this actuator l7 is normally operated by built-in springs 17a. 17b elastically supports the rear wheel in a non-steering neutral position, and when pressure is supplied to the chamber 17C or 17d, the rear wheel is auxiliary steered to the left or right by an angle corresponding to the pressure.

Actuator evening chamber 17c. The pressure at 17d is controlled by a spring center type electromagnetic proportional pressure control valve 18, which is inserted between the supply circuit 10, the drain circuit 1l, and the actuator chambers 17c and 17d. Valve l8 has both solenoids 18a. When the solenoid 18b is OFF, both the chambers 17c and 17d are in a pressureless state, and when the solenoid 18a is ON, a pressure proportional to the driving current 1rL is applied to the chamber 17c, and when the solenoid 18b is ON, the driving current i. Pressure proportional to chamber 1
7d.

The currents 1 rL + 1 rR are also respectively controlled by the controller 12. Therefore, this controller includes the brake rotors 19L=19R and the torque arm 2 of the left and right rear wheels.
Braking torque ε of the brake unit consisting of 0L and 2OR
．． ,ε. Also enter. Note that these braking torques are determined by the torque arm 2OL. Strain gauge 21L attached to 2OR
, 21H.

The controller 12 executes the control program shown in FIG. 9 to prevent course changes due to the difference in braking torque between the left and right wheels by auxiliary steering of the front and rear wheels. Steps 31 to 39 in Figure 9,
61. 62 is the same as the step indicated by the same reference numeral in FIG. 6, and the only difference is that in step 31, the braking torques εrL, ε, and R of the left and right rear wheels are also read.

In order to perform auxiliary steering of the rear wheels, in step 92, the braking torque difference Δτ between the left and right rear wheels is set to Δτ, -ε. -Δε. In the next step 92, calculate this and ST? From the correction coefficient k described above in FIG.
Calculate by calculating k.

In step 93, it is checked whether Δε,≧0, and Δε
, ≧0, that is, if it is determined that the left rear wheel braking torque is greater than or equal to the right rear wheel braking torque, the current 1r is set in step 94.
1 is set to 0, and in step 95, a current 1rL corresponding to the left and right rear wheel braking torque difference Δε is looked up from the table data corresponding to FIG. 10, and in step 96, this 1rL is output to the solenoid 18a.

By the way, Figure 10 shows the current value for obtaining the rear wheel auxiliary steering amount that cancels out the yaw moment caused by the difference in braking torque between the left and right rear wheels! ■(1■), and when Δε, ≧0, yaw moment ψ, is generated in the counterclockwise direction as is clear from the above-mentioned part of FIG. It is necessary to perform auxiliary steering to the left, so let us give rL.

Conversely, if it is determined in step 93 that Δε1<0, that is, if the right rear wheel braking torque is larger than the left rear wheel braking torque, 1rL is set to 0 in step 97, and the lth
Look up the current 1rl1 corresponding to the left and right rear wheel braking torque difference from the table data corresponding to the O diagram, and perform step 9.
At step 9, this lrl is output to the solenoid 18b.

Current j rL+ lrl is the pressure control valve solenoid 1
8a and 18b to generate a pressure proportional to the current in the chamber 17C or 17d, and auxiliary steering the rear wheels to the left or right via the actuator 17. This cancels the yaw moment caused by the difference in braking torque between the left and right rear wheels, and prevents the course of the vehicle from changing due to the difference in braking torque between the rear wheels.

The reason why the above-mentioned auxiliary steering is mainly performed when the steering wheel steering angle θ is around 0 using the correction coefficient k, and the above-mentioned auxiliary steering is not performed in a turning state is as follows.
The same as described above with respect to FIGS.

(Effects of the Invention) Thus, as described above, when there is a difference in braking torque between the left and right wheels, the device of the present invention is configured to carry out steady-assisted steering to cancel the accompanying yaw moment. This prevents the driver from changing course, thereby preventing the driver from feeling uneasy.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the device of the present invention, Fig. 2 is a diagram of a vehicle auxiliary steering system showing an embodiment of the present invention, Fig. 3 is a flowchart showing a control program of a controller in the same example, and Fig. 4 is a diagram of the auxiliary steering system of a vehicle showing an embodiment of the invention. A diagram showing the relationship between the left and right front wheel braking torque difference and the front wheel auxiliary steering control current in the example; Figure 5 is a system diagram similar to Figure 2 showing another example of the present invention; Figure 6 is the controller control in the same example. A flowchart showing the program, FIG. 7 is a characteristic diagram of the correction coefficient used in the same example, and FIGS. 8 and 9 are system diagrams and flowcharts similar to FIGS. 5 and 6, respectively, showing other examples of the present invention. , Figure 10 is a relationship diagram between the left and right rear wheel braking torque difference and the rear wheel auxiliary steering control current, and Figures 11 and 12 are diagrams explaining the occurrence of yaw moment due to the braking torque difference between the left and right wheels, respectively. . IL, IR...Front wheel 2L, 2R...
Rear wheel 3... Steering wheel 4... Steering gear 5, 17... Actuator 7.18... Pressure control valve 12... Controller 15L. 15R. ．． 21L. 21R...Strain gauge 16...Steering angle sensor. Figure 2 Figure 5 Lawyer τβθ Figure 6 Figure 8 Kuha

Claims (1)

[Claims] 1. In a vehicle equipped with an auxiliary steering device that performs auxiliary steering of at least one of the front wheels and the rear wheels in addition to the main steering of the front wheels, a braking torque difference detection means for detecting a braking torque difference between the left and right wheels. and auxiliary steering angle control means for operating the auxiliary steering device so as to cancel the yaw moment caused by the braking torque difference. A course change prevention device when braking a vehicle. 2. A course change prevention device when braking a vehicle according to claim 1, wherein the auxiliary steering angle control means is configured to reduce the auxiliary steering angle in a region where the amount of the main steering is large.