JPH01115774A - Steering angle ratio control device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of vehicle's behavior being inexpectable by a driver, by a method wherein a means to set a plurality of steering angle ratio modes having different steering angle ratios responding to a car speed is provided, and a steering angle ratio is switched to a value responding to a car speed according to the steering angle ratio mode selected by a mode switch. CONSTITUTION:In a steering angle ratio control mechanism A in which an input link 14 is coupled to a drop arm 8 so as to interlock with a front wheel steering mechanism 7, an output link 27 coupled to a control lever 30, pivotally mounted at 23 to a car body, by means of a pin 28 is provided. A longitudinally movable rod 31 pivotally supported at 27a to the output link 27 is coupled to the one valve element of a servo control valve 32 of a rear wheel steering mechanism 34. A gear 17 rotated with the aid of a steering angle ratio control motor 18 is engaged with a partial gear 22 on an arc of a circle formed to the output link 27. The steering angle ratio control motor 18 is controlled by an electronic control device 51 according to a steering ratio determined in response to a car speed according to one, selected by a mode switch 54, out of a plurality of steering ratio modes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steering angle ratio control device for a four-wheel steering vehicle.

[Prior Art] As disclosed in Japanese Unexamined Patent Publication No. 60-85070, in a four-wheel steering vehicle in which the rear wheels are steered in the opposite phase to the front wheels when running at low speed, if the rear wheel steering angle ratio is too large, Since this gives the driver a sense of discomfort during normal driving, the steering angle ratio mode can be selected with assistance depending on road conditions that require particularly tight turning ability. However, when equipped with multiple steering angle ratio modes, if the steering angle ratio mode suddenly switches while driving, the rear wheels may be steered suddenly even when the steering wheel is stopped, causing the vehicle to become unpredictable to the driver. This behavior is unfavorable from a safety standpoint.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, the object of the present invention is to develop a vehicle speed range in which the steering angle ratio does not change even if the steering angle ratio mode is selected during driving (where the steering angle ratio mode is common). It is an object of the present invention to provide a steering angle ratio control motor in which the steering angle ratio mode is not switched unless the steering angle ratio mode is in the region).

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention includes a means for detecting vehicle speed, a means for detecting a steering angle ratio, and a plurality of steering wheels having different steering angle ratios corresponding to vehicle speeds. means for setting an angle ratio mode;
A control lever that rotates in relation to front wheel steering is equipped with a steering angle ratio control motor that changes the connection point of the output link that drives the rear wheel steering member, and the steering angle ratio selected by the mode switch. The mode setting means switches at a predetermined vehicle speed or higher.

[Function] When the vehicle speed is lower than the predetermined value V3, the mode switch 5
Even if a new selection is made using 4, the steering is performed in the previous steering angle ratio mode, and there will be no sudden switching.

When the vehicle speed becomes higher than VS, the steering angle ratio mode is switched to the selected steering angle ratio mode. In this vehicle speed range, the steering angle ratio before and after mode switching is almost the same, so the rear wheels will not be suddenly steered, and sudden changes in vehicle behavior will cause spin, etc.
problems are avoided.

[Embodiment of the Invention] As shown in FIG. 1, a knuckle arm 3 that supports each of the left and right front wheels 2 is rotatably supported on the vehicle body by a support shaft 3a, and is operatively connected by a tie rod 4. An arm of the right knuckle arm 3 is connected to the front wheel steering mechanism 7 via a drag link 10. The front wheel steering mechanism 7 is a handle 5
When the steering shaft 6 is rotated, the output shaft 7a is rotated,
The drag link 1o is moved back and forth by swinging of the drop arm 8 coupled thereto. A rod 12 is connected to a pin 9 connected to the middle part of the drop arm 8, and the rear end of the rod 12 is connected to an input link 14 of the steering angle ratio control mechanism A by a pin 13.
is connected with.

The input link 14 is connected to the end of the control lever 30 by a pin 15. A control lever 30 rotatably supported on the vehicle body by a support shaft 23 is connected to an output link 2 by a connecting pin 28.
7 is connected. The output link 27 is connected to a rod 31 that moves back and forth by a pin 27a. The rod 31 is connected to one valve element of a servo control valve 32 of a rear wheel steering mechanism 34.

The rear wheel steering mechanism 34 is integrally configured with a servo control valve 32 and an actuator. Actuator is cylinder 3
A piston 35 is fitted into the rod 3, and the outer end of the rod connected to the piston 35 is supported by the vehicle body. Servo control valve 3
The other valve element of 2 is integral with the cylinder 33 and the rod 3
Combine 6.

A rod 36 is connected to one end of a lever 37 supported by a support shaft 38 on the vehicle body, and a rod 39 that moves back and forth is connected to the other end. The rear end of the rod 39 is connected to an arm of a knuckle arm 41 that supports a rear wheel 40. The left and right knuckle arms 41 are interlocked and connected by tie rods 42.

The control lever 30 of the steering angle ratio control mechanism A is provided with an arcuate groove 29 centered on the pin 27a, and the connecting pin 28 is slidably engaged along the groove 29. In order to slide the connecting pin 28, an arc-shaped partial gear 22 is integrally formed at the end of the output link 27, and the gear 17 that meshes with the arc-shaped partial gear 22 is integrally formed at the end of the output link 27.
is driven by the steering angle ratio control motor 18. For this reason,
A worm shaft 21 of a steering angle ratio control motor 18 is meshed with the gear 16 coaxially connected to the gear 17 . The steering angle ratio control motor 18 and the gear 17 are integrally supported by a frame, and this frame is slid by an actuator 19 along a guide groove 20 of the vehicle body. The actuator 19 is made up of a cylinder fitted with a piston, and this piston is connected to the frame of the steering angle ratio control motor 18 by a rod, and is normally moved forward (
(a direction in which the gear 17 and the partial gear 22 are disengaged).

The support shaft 23 of the control lever 30 has a groove continuous with the groove 29. When the lever 24 connected to the control lever 30 is rotated clockwise by the actuator 25, the groove of the support shaft 23 moves to l! i It is blocked from the groove 29 of the control lever 3o. The actuator 25 is formed by fitting a piston into a cylinder, and the piston and the lever 24 are connected by a rod. Normally, the lever 24 is pressed against the stopper 26 by the spring force of the actuator 25, and the groove of the support shaft 23 and the control lever 3
0 grooves 29 are continuous.

Now, when the steering wheel 5 is turned to the right, the drag link 10 of the front wheel steering mechanism 7 moves forward, the knuckle arm 3 rotates clockwise about the support shaft 3a, and the front wheel 2 is deflected to the right. Ru. At the same time, the rod 12 also moves forward, and the control lever 30 rotates counterclockwise about the support shaft 23. The rod 31 is pulled forward by the output link 27,
Under the action of the servo control valve 32, pressure oil is supplied to the upper chamber in the diagram of the actuator. The cylinder 33 moves forward, the rod 39 moves backward via the lever 37, the knuckle arm 41 rotates counterclockwise around the support shaft 41a, and the rear wheel 40 moves to the left (in opposite phase to the front wheel). deflected to At this time, since the turning radius of the vehicle becomes smaller, the ability to turn around at low speeds is improved. When the gear 17 is rotated by the steering angle ratio control motor 18 in relation to the vehicle speed and the output link 27 is rotated counterclockwise about the pin 27a, the connecting bin 28 moves to the left side of the support shaft 23.

At this time, the rear wheels are deflected in the same phase as the front wheels, improving steering stability when changing lanes at high speeds.

The steering angle control motor 18 is connected to the electronic i control system [5] in relation to the vehicle speed.
1. A plurality of steering angle ratio setting means having different steering angle ratios corresponding to the vehicle speed are stored and set in the electronic control device 51, and the steering angle ratio mode is selected by the mode switch 54. In order to detect the vehicle speed, for example, a signal from a vehicle speed sensor 55 disposed facing the output shaft of the transmission is input, and a signal from a steering angle ratio sensor 56 disposed facing the partial gear 22 is input, for example. and are added to the electronic #Jtl device 51, respectively. The steering angle ratio setting means sets the steering angle ratio mode to be common or substantially equal in a high speed range, and sets a plurality of steering angle ratios corresponding to road conditions in a low speed range lower than a predetermined value.

An electronic control device 51 consisting of a microcomputer calculates a steering angle ratio corresponding to the vehicle speed from a control map based on a steering angle ratio mode selected in advance by a mode switch 54, and adjusts the steering angle so that this steering angle ratio is achieved. Ratio control motor 1
When the steering angle ratio detected by the steering angle ratio sensor 56 becomes equal to the steering angle ratio corresponding to the vehicle speed determined from the control map, the steering angle ratio 11Jtll motor 18 is stopped at that position. .

When the mode switch 54 is newly selected while driving, the steering angle ratio control motor 18 is controlled in the previous steering angle ratio mode if the vehicle speed is below a predetermined value. The wheels are never steered. When the vehicle speed becomes higher than the predetermined @VS, the steering angle ratio control motor 18 is controlled based on the newly selected steering angle ratio mode, so the rear wheels are not substantially suddenly steered. , unnatural behavior of the 11 cars is avoided.

As shown in FIG. 2, when the vehicle speed is higher than the predetermined value VS (region where steering angle ratio control modes -1 and -2 are common), operating the mode switch 54 switches the steering angle ratio control mode. . When the vehicle speed becomes lower than the predetermined value VS,
The steering angle ratio control mode is automatically selected, and the steering angle ratio does not suddenly change, and smooth steering angle ratio control can be obtained without causing any discomfort.

3-5 are flowcharts of the above-mentioned control program. In the figure, p11 to p36 and p61 to p66 represent each step of the program. This program starts at Dll, initializes at p12, and reads the vehicle speed ■ based on the signal from the vehicle speed sensor 55 at p13. At p14, the signal i of the mode switch 54 is read. The steering angle ratio control mode selected by the mode switch 54 at p15 is -1.
Determine whether or not. If the steering angle ratio control mode selected by the mode switch 54 is -1, the address A of the backup RAM is set to 1 in p16, and the process advances to p18. The steering angle ratio control mode selected by the mode switch 54 is -
If it is not 1 (s2), address A (steering angle ratio III) is set to 0 in p17.

At p18, it is determined whether the mode switching flag is OFF.

If the mode switching flag is ON, the process advances to p22; if the mode switching flag is OFF, it is determined in p19 whether address A is equal to 0 or not. If address A is not equal to O, the mode lamp of m2 is lit in p20, the mode lamp of 1 is extinguished in p21, and the process proceeds to p24. If address A is O in p19, the -1 mode lamp is lit in p22, and the moto lamp in m2 is extinguished in p23.

At p24, it is determined whether address A is equal to address 8 (value of steering angle ratio). If address A is equal to address B, it is determined in step 1) 25 whether the vehicle speed ■ is greater than a predetermined value VS. If the vehicle speed V is smaller than the predetermined value VS, proceed to p29. If the vehicle speed V is greater than the predetermined value VS, it is determined in p2B whether the vehicle speed 1 before the mode switch 54 is newly selected is greater than the predetermined value VS. If the vehicle speed ■1 is greater than the predetermined value VS, proceed to p29. If vehicle speed ■1 is smaller than the predetermined value VS, 1)2
At step 7, turn on the mode switching flag and proceed to page 29.

If address A is not equal to address B in p24,
At step 928, the mode switching flag is turned OFF, at p29, A is assigned to address B of the backup RAM, and at p30, it is determined whether the mode switching flag is OFF. If the mode switching flag is ON, proceed to p33. If the mode switching flag is OFF, it is determined in p31 whether address B is O or not. If the address B is not O, the steering angle ratio k is determined based on the steering angle ratio control mode I2 in p32, and the process proceeds to p34. If the address B is O in p31, the steering angle ratio k is determined based on the steering angle ratio control mode 1 in p33. At p34, the steering angle ratio k is set to one mark steering angle ratio kt. At p35, the vehicle speed is set to 1, and at p36, the steering angle ratio control motor 18 is driven by the interrupt program shown in FIG. 5 to obtain the required steering angle ratio.

The interrupt program shown in Figure 5 starts at p61,
At p62, the steering angle ratio control motor 18 is driven so that the steering angle ratio becomes the target steering angle ratio kt. At p63, the actual steering angle ratio ks is read based on the signal from the steering angle ratio sensor 19. At p64, it is determined whether the target steering angle ratio kt is equal to the actual steering angle ratio ka. If the target steering angle ratio kt is not equal to the actual steering angle ratio ks, the process returns to p62. If the target steering angle ratio kt is equal to the actual steering angle ratio ks, 1) the steering angle ratio control motor 18 is stopped at 65, and the steering angle ratio control motor 18 is stopped at 65;
At 66, the program returns to RTI, ie, the program shown in FIG. 3-4. The above program is repeatedly executed at predetermined time intervals. As a result, the steering angle ratio control motor 18 sets the steering angle ratio according to the vehicle speed from time to time.

In the modified embodiment shown in FIG. 6, the programs p24 to p36 following p11 to p23 are replaced with p41 to p56, and a reset switch is provided, and when the reset switch is turned on, the mode switching flag is turned off. , the mode returns to normal mode 1. p
41 to p56 represent each step of the program. p41
It is determined whether address A is equal to address B or not. If address A is equal to address B, p42
It is determined whether the vehicle speed ■ is greater than the predetermined value VS.

If the vehicle speed ■ is smaller than the predetermined value VS, proceed to p46.

If the vehicle speed V is larger than the predetermined value VS, 1) Vehicle speed before newly selecting the mode switch in 43■1 is the predetermined value V
It is determined whether the value is larger than 8 or not. Vehicle speed v1 is a predetermined value V
If it is smaller than S, set the mode switching flag to O in p44.
Set N and proceed to page 46. If the vehicle speed v1 is greater than the predetermined value VS, the process advances to p46.

If address A is not equal to address B in p41,
The mode switching flag is turned OFF in p45, and the reset switch signal is read in p46. At p47, it is determined whether the reset switch is ON or not. Reset switch is ON
In this case, turn off the mode switching flag with p4Jl, and set p4Jl to OFF.
Proceed to 40. If the reset switch is OFF, p.49
Assign A to address B in the backup RAM. p
At step 50, it is determined whether the mode switching flag is OFF. If the mode switching flag is ON, the process advances to p53; if the mode switching flag is OFF, it is determined in p51 whether address B is O or not. If address B is not O, p52
Find the steering angle ratio k based on the steering angle ratio control mode 12 in p5.
Proceed to step 4. If the address B is 0 in p51, the steering angle ratio k is determined based on the steering angle ratio control mode -1 in p53, and the steering angle ratio k is determined in p54.
The steering angle ratio is set to the target steering angle ratio kt. Vehicle speed vl with p55
Then, at p56, the steering angle ratio control motor 18 is driven by the interrupt program shown at p61 to p966 in FIG.

[Effects of the Invention] As described above, the present invention includes a means for detecting vehicle speed, a means for detecting a steering angle ratio, a means for setting a plurality of steering angle ratio modes having different steering angle ratios corresponding to vehicle speed, A control lever that rotates in relation to front wheel steering is equipped with a steering angle ratio control motor that changes the connection point of the output link that drives the rear wheel steering member, and the steering angle ratio mode selected by the mode switch is provided. Since the setting means is configured to switch at a predetermined vehicle speed or higher, even if a new steering angle ratio mode is selected by the mode switch at a low vehicle speed below a predetermined value, the steering angle ratio mode will not be switched immediately. Therefore, accidents such as the rear wheels being steered even when the driver is not operating the steering wheel (while the steering wheel is stopped) and the vehicle being steered against the driver's breath and spinning out can be avoided.The mode switch When a new steering angle ratio mode is selected, the steering angle ratio mode switches here when the vehicle speed increases above a predetermined value.However, in practice, when the vehicle speed exceeds a predetermined value, the steering angle ratio corresponding to the vehicle speed changes. Because they are equal or almost equal, the rear wheel steering angle does not change suddenly, and only when the vehicle speed drops below a predetermined value does the rear wheel steering angle smoothly change according to the vehicle speed based on the new steering angle ratio mode. , and does not cause any discomfort to the driver.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a schematic configuration of a four-wheel steering vehicle equipped with a steering angle ratio control mechanism according to the present invention, FIG. 2 is an operating characteristic diagram of the steering angle ratio control mechanism, and FIG. Flowchart of a program for controlling the steering angle ratio control mechanism by an electronic control device, 5th.
FIG. 6 is a flowchart of a modified example of the same block O-gram. 6: Steering shaft 17: Gear 18: Steering angle ratio i control motor
19.25: 7 cutuator 22: Partial gear 23:
Support shaft 27: Output link 28: Connection pin 30: ll+
1tlD lever 34: 1 wheel steering 11111140:
1 wheel 51: Electronic control device 54: Mode switch 5
5: Vehicle speed sensor 56: Steering angle ratio sensor Patent applicant Isuzu Motors Co., Ltd.

Claims (1)

[Claims] means for detecting vehicle speed; means for detecting steering angle ratio; means for setting a plurality of steering angle ratio modes having different steering angle ratios corresponding to vehicle speed; and a control lever that rotates in relation to front wheel steering. , and a steering angle ratio control motor that changes the connection point of the output link that drives the rear wheel steering member, and is characterized in that the steering angle ratio mode setting means selected by the mode switch is switched at a predetermined vehicle speed or higher. A steering angle ratio control device.