JPH0239401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fully hydraulic power steering system, more specifically, wheels are steered by hydraulic pressure, and the ratio of the rotation angle of the steering wheel shaft to the actual steering angle of the wheels is
The present invention relates to a steering device that changes according to the magnitude of the rotation angle of a steering wheel shaft.

In the steering system of a vehicle, the ratio of the rotation angle of the steering wheel shaft to the actual steering angle of the wheels, that is, the rotation angle of the steering wheel shaft/the actual steering angle of the wheels (hereinafter abbreviated as "angle ratio"), is determined by the steering shaft. There are some that are variable depending on the magnitude of the rotation angle. In other words, the angle ratio becomes large in a range where the rotation angle of the handle shaft is small, and becomes small in a range where the rotation angle of the handle shaft is large. Changing the angle ratio according to the rotation angle of the steering wheel shaft in this way is dangerous (especially when driving at high speed) when the steering wheel is near the neutral position and the wheel tilts significantly with a slight steering wheel operation. On the other hand, when the steering wheel is turned to the left or right, it is easier to operate the steering wheel if the wheel tilts more with less steering wheel operation.

As means for changing the angle ratio, for example, a gear ratio variable type is known. this is,
A rack integrated into the wheel is moved by a pinion that rotates integrally with the handle shaft, and the gear ratio is changed by changing the meshing position of the rack and piston according to the rotation angle of the handle shaft. As a result, the actual steering angle of the wheels is changed. However, in a variable gear ratio steering device, it is not easy to mold the pinion and rack into a predetermined shape, and the disadvantage is that the processing cost increases.

The present invention has been made for the purpose of eliminating the drawbacks of the above-mentioned prior art, that is, providing an inexpensive and reliable steering device.
In order to achieve this objective, in the present invention,
The entire steering device is configured to be fully hydraulically powered (in this specification, this means that there is no mechanical linkage between the steering wheel and the wheels), and there are various types of steering devices that are interposed between the steering wheel and the wheels. Either the drive unit or the control unit has a non-linear characteristic of the output with respect to the input, so that the rotation angle of the handle shaft can be adjusted.
The ratio of the actual steering angle of the wheels is increased in a range where the rotation angle of the steering wheel shaft is small, and decreased in a range where the rotation angle is large.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, an external gear 14 is fixed to the lower end of a handle shaft 12 with a handle 10 fixed to its upper end, and the external gear 14 is meshed with a heart-shaped cam 16 having an internal gear. . cam 16
A ball 20 is biased and pressed by a spring 22 in the recess 18 on the outer peripheral surface of the recess 18, and a pin 24 is erected radially outward at a portion facing the recess 18. The compression of the ball 20 into the recess 18 causes the handle 10 to always tend to return to its neutral position. Further, the pin 24 can come into contact with a pair of stoppers 26 or 28 fixedly provided outside the cam 16, thereby causing the cam 16 to
That is, the maximum amount of rotation of the handle 10 is regulated. Furthermore, a slider 30 is biased and pressed by a spring 32 on the upper surface of the cam 16, and acts to brake the rotation of the cam 16, that is, the handle 10.

An upper end of a deceleration shaft 34 is fixed to the center of a disk (bottom plate) fixed to the lower surface of the external gear 16, and a handle angle sensor 36 is attached to the lower end thereof. The deceleration shaft 34 is decelerated by the gear 14 and the cam 16, and rotates about half of the rotation of the handle shaft 12. As the angle sensor 36, a potentiometer is used here, and outputs an electric signal (resistance value) proportional to the steering angle of the steering wheel.
This output is input to an arithmetic unit (controller) 38 via a line 35. Inside the calculator 38, as shown in FIG. 3, the angle sensor 3 is
Cylinder stroke sensor 4 corresponding to the output of 6
The target value of the output of 8 is selected.

That is, in the arithmetic unit 38, the characteristic map showing the relationship between the read value of the handle angle sensor 36 and the target value of the cylinder stroke is non-linear, and when the read value of the sensor 36 is small, that is, the amount of rotation of the handle 10 is When it is small, the target value is small;
When the read value of the sensor 36 is large, that is, when the amount of rotation of the handle 10 is large, the target value is selected to be large. Note that Fig. 3 shows only the case where the read value of the handle angle sensor is positive (for example, when the handle 10 turns to the right), and the target value of the cylinder stroke when the read value is negative is point symmetrical with this. Become.

The output from the computing unit 38 is input to coils 42 and 44 of a hydraulically operated four-port three-position switching valve 40 through lines 37 and 39. The pressure oil in the tank 42 is transferred to the switching valve 40.
It is designed to be supplied with oil by a pump 45.
In addition, 46 in the figure is a relief valve. Switching valve 40
A cylinder stroke sensor 48 for detecting the amount of movement of the piston 46 is fixed to the cylinder 47 of the hydraulic cylinder 41, which operates by controlling the supply and discharge of pressure oil. This sensor 48 uses a linear potentiometer and outputs an electric signal (resistance value) proportional to the cylinder stroke, and this output is input to the arithmetic unit 38 through a line 43. Note that the piston rod 50 is operatively connected to a wheel (not shown).
By protruding and retreating, the wheels are rotated to the left or to the right.

Next, the operation of this embodiment will be explained.

When the handle 10 is turned left or right, the cam 16 rotates in the same direction through engagement with the internal gear 14, and the rotation angle of the handle shaft 12 is read by the handle position sensor 36. From the handle position sensor 36, a predetermined electric signal is inputted to the calculator 38 from the line 35 in proportion to the direction and amount of rotation of the handle 10.

The calculator 38 includes a cylinder stroke sensor 48.
An electric signal is also input from the coil 42 of the switching valve 40, and the signal from the handle position sensor 36 and the signal from the cylinder stroke sensor 48 are compared and predetermined processing (this will be described later) is performed. or 44 is selectively energized to switch the switching valve 40 to either position or (neutral). The coil 42 is energized and the switching valve 4
0 switches to the side, pressure oil is supplied to the piston rod 50 side of the hydraulic cylinder 41 and the piston rod 50 is drawn in, and when the opposite coil 44 is energized and switches to the side, the piston rod 5
Pressure oil is supplied to the opposite side of piston rod 5.
0 will be pushed out. Hydraulic cylinder 41
The amount of movement of the piston 46 during operation is detected by a cylinder stroke sensor 48, and the result is fed back to the calculator 38. If the amount of movement of the piston rod 50 has not yet reached the target value, the switching valve 40 is further actuated by the signal from the calculator 38, and this is repeated until the target value and the momentum of the piston rod 50 finally match. (See Figure 3).

Here, since the characteristic map of the calculator 38 is set as described above, while the rotation angle of the steering wheel shaft 12 is small, the piston rod 50 is moved only a little with respect to the unit steering angle of the steering wheel 10, and the wheels are moved slightly. On the other hand, if the rotation angle of the steering wheel shaft 12 increases, the piston rod 50 will be moved largely relative to the unit steering angle of the steering wheel 10, and the wheels will tilt a lot. In other words, it functions as the variable gear ratio steering device (see FIG. 2).

In the above embodiment, the arithmetic unit 38 has a nonlinear characteristic map, and the characteristic maps of the handle position sensor 36 and the cylinder stroke sensor 48 are both linear. However, it is not essential to do so. That is, in the present invention, it is sufficient that there is a signal processing means with non-linear characteristics between the handle 10 and the wheels, and the characteristic map of the handle position sensor 36 or the cylinder stroke sensor 48 in the above embodiments may also be made non-linear. It is possible.

Next, such an example will be described.

In the second embodiment, a characteristic map showing the relationship between the steering wheel steering angle and the resistance value inside the steering wheel position sensor 36 is as shown in FIG. That is, the resistance value as a whole is designed to gradually decrease when the steering wheel 10 is turned to the left and gradually increase when the steering wheel 10 is turned to the right. Time)
In this case, the rate of change in the resistance value with respect to changes in the steering wheel steering angle is reduced, and conversely, as the steering wheel 10 is turned left or right, the rate of change is increased. In this case, the characteristic maps of the computing unit 38 and the piston position sensor 36 are both linear.

In this way, when the steering wheel steering angle is in a small range, the rate of change in resistance as an electric signal input to the calculator 38 becomes small, and the switching valve 40 switches accordingly, so that the hydraulic cylinder 4
The amount of movement of the first piston 46 is reduced. On the other hand, as the steering angle of the steering wheel increases, the rate of change in the resistance value input to the calculator 38 increases, so the amount of movement of the piston rod 50 increases.

Further, in the third embodiment, a characteristic map showing the relationship between the cylinder stroke and the resistance value inside the piston position sensor 36 is as shown in FIG. To be more specific, the overall resistance value is small when the cylinder stroke is small, and gradually increases as the cylinder stroke becomes large, but in the range where the cylinder stroke is medium, that is, when the wheels are moving straight, the resistance value increases The rate of change is increased,
The rate of change is made small when the cylinder stroke is small and large. In this case, the characteristic maps of the handle position sensor 36 and the computing unit 38 are both linear.

The fact that the characteristic map of the cylinder stroke sensor 48 is as described above means that when the cylinder stroke is medium, the sensitivity of the movement of the piston rod 50 is high, and therefore the amount of movement is small. When a linear scale is used as the cylinder stroke sensor 48, as shown in FIG. 6, the pattern of the slits 48b of the movable plate 48a can be made dense near the center position in the longitudinal direction and coarse on both sides. This is effective in terms of actual steering and reduction of the amount of information to be handled.
The same applies when an encoder is used as the handle angle sensor 36.

It should be noted that the present invention should not be interpreted as being limited to the above embodiments, but can be modified and improved as appropriate without departing from the spirit thereof. For example, the overall system of the steering device shown in FIG. 1 is not limited to what is shown in the figure, and the specific configuration of the steering wheel position sensor 36, computing unit 38, or cylinder stroke sensor 48 and the shape of the characteristic map may be changed as desired. can be added.

Further, it is also possible to make the ratio of the rotation angle of the steering wheel shaft/actual turning angle of the wheels, that is, the value of the angle ratio, variable according to the vehicle speed. That is, as shown in FIG.
The angle ratio increases as the vehicle speed increases. To this end, a plurality of characteristic maps (Fig. 3) of the computing unit 38 are set in consideration of the vehicle speed, and a vehicle speed sensor 65 (indicated by a two-dot chain line in Fig. 1) is provided, and its output is sent to the computing unit. 38 and select one of the characteristic maps according to this input. It is desired that the steering wheel 10 be easy to steer at low speeds, but if the angle ratio is the same at medium and high speeds as at low speeds, the steering wheel sensitivity will become too sensitive (the wheels will turn easily with a small amount of steering wheel operation). ) is dangerous.

As described above, according to the present invention, in a fully hydraulic power steering system, it is possible to obtain steering characteristics similar to the conventional so-called variable gear ratio steering system by controlling electric signals. Since there is no need for troublesome machining of gears, the manufacturing cost of the entire system can be reduced.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention;
FIG. 2 is a graph showing the relationship between the steering wheel steering angle and the angle ratio, and FIG. 3 is a graph showing the arithmetic unit 38 in the above embodiment.
FIG. 4 is a graph showing the characteristic map of the handle angle sensor 36 as the second embodiment. FIG. 5 is a graph showing the characteristic map of the cylinder stroke sensor 48 as the third embodiment. 7 is a plan view showing a slit pattern when a linear scale is used as a cylinder stroke sensor, and FIG. 7 is a graph showing the relationship between vehicle speed and angle ratio in the fourth embodiment. [Explanation of symbols of main parts], 10...Handle,
36...Handle angle sensor, 38...Calculation unit, 4
0...Switching valve, 41...Hydraulic cylinder, 48...
Cylinder stroke sensor, 50...Piston rod.

Claims (1)

[Claims] 1. Operating the switching valve by rotating the handle shaft,
In a fully hydraulic power steering system for a vehicle that steers wheels by the movement of a hydraulic piston, the rotation angle of the handle provided on a deceleration shaft interlocked with the handle shaft via a deceleration means is detected. angle detection means for outputting an angle signal; momentum detection means for detecting the momentum of the piston and outputting a momentum signal; and controlling the operation of the piston by comparing both the angle and momentum signals. A control means is provided, and the output characteristic of any one of the angle detection means, the momentum detection means, or the control means is set to be non-linear, and the rotation angle/of the handle shaft is controlled.
A fully hydraulic power steering device characterized in that the ratio of the actual steering angle of the wheels is large in a region where the rotation angle of the steering wheel shaft is small and small in a region where the rotation angle of the steering wheel shaft is large. 2 Operate the switching valve by rotating the handle shaft,
In a fully hydraulic power steering system for a vehicle that steers wheels by the movement of a hydraulic piston, the rotation angle of the handle provided on a deceleration shaft interlocked with the handle shaft via a deceleration means is detected. angle detection means for outputting an angle signal; momentum detection means for detecting the momentum of the piston and outputting a momentum signal; speed detection means for detecting the speed of the vehicle and outputting a speed signal; and the angle and momentum. and a control means for controlling the operation of the piston by comparing both the signals and the speed signal, and the output characteristic of any one of the angle detecting means, the momentum detecting means, or the control means is made non-linear, and the output characteristic of the handle shaft is A fully hydraulic power steering device characterized in that the ratio of rotation angle/actual steering angle of the wheels is large in a region where the rotation angle of the steering wheel shaft is small and small in a region where the rotation angle of the steering wheel shaft is large.