JPH0764263B2 - Power steering hydraulic control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic control device for a power steering.

(Prior Art) Conventionally, as a hydraulic control device for power steering of a vehicle such as an automobile, for example, “Symposium on recent chassis technology and vehicle dynamic performance” edited by the Society of Automotive Engineers of Japan (Showa era)
(June 29, 1984), known as "flow control method (adopted for Isuzu Motors Piazza)" and hydraulic reaction force control method (used for Mitsubishi Motors Galant) announced as "electronic control of power steering". There is. In both of the above-mentioned vehicle systems, the steering force at the time of stationary steering is light, and at the time of high speed traveling, a proper steering reaction force is provided to enable stable traveling, and the hydraulic pressure of a general type power steering that only obtains unique throttle characteristics. A steering characteristic superior to that of the control device can be obtained.

(Problems to be Solved by the Invention) However, in the case of controlling the increase / decrease of the hydraulic fluid flow rate at a predetermined ratio corresponding to the vehicle speed like the above-mentioned flow rate control method, the oil required for rapid steering during high speed traveling If it is set so that the amount can be secured, the oil amount at the time of stationary operation will be supplied more than necessary, and the discharge capacity of the hydraulic pump must be increased more than necessary. That is, when making the steering force lighter or heavier depending on the amount of hydraulic oil introduced to the hydraulic control valve, for example, the amount of oil is set to an appropriate weight so that the steering force during high-speed traveling is not too light. If the amount is reduced, the absolute amount of oil supplied to the hydraulic control valve at the time of sudden turning becomes insufficient, and the steering force at the time of turning the steering wheel becomes extremely heavy, which is not preferable in terms of safe traveling. In order to solve this problem, if the amount of oil required at the time of sudden turning is secured, the amount of oil at the time of stationary steering will unintentionally increase excessively because of proportional control. As a result, the discharge capacity of the hydraulic pump increases as described above,
There has been a problem that an excessive heat countermeasure is required due to an increase in the heat generation amount of the entire hydraulic control device, which causes a rise in manufacturing cost and the like.

Further, in the hydraulic control device for power steering using the above hydraulic reaction force control system, in order to generate a hydraulic reaction force, components corresponding to the reaction force chamber and the reaction force piston, and further, the working oil is circulated for switching the hydraulic pressure. In addition to the hydraulic pressure control valve, a hydraulic pressure switching valve to be used is required. as a result,
Since the entire structure and the piping system are large and complicated, there is a problem that a large assembly space is required and the hydraulic control device as a whole is soared.

The present invention has been made to solve the problems of the conventional hydraulic control device for a power steering. The steering force at the time of stationary steering is light, and the vehicle speed from the low to medium speed range to the high speed range during traveling. In addition, it is possible to obtain a suitable steering force corresponding to the above, and there is no need to increase the discharge capacity of the hydraulic pump more than necessary unlike the conventional flow rate control method, and there is no need for excessive heat countermeasures accompanying it. It is an object of the present invention to provide a simple and inexpensive hydraulic control device for power steering that does not require a complicated structure such as a hydraulic reaction force control system.

(Means for Solving Problems) In order to solve the above problems and achieve the object, a hydraulic control device for a power steering according to the present invention includes first and second hydraulic communication units that communicate with a hydraulic power source and a reservoir tank. The oil passages communicate with the left and right hydraulic chambers in the power cylinder, respectively, and the hydraulic pressure from the hydraulic source acts on the left and right hydraulic chambers in the power cylinder with a pressure difference corresponding to the steering operation of the steering wheel. A steering hydraulic control device, comprising: a pair of first-system throttle valves which are provided in the first and second oil passages on the upstream side of the hydraulic chamber and whose throttle area changes in accordance with steering torque; A pair of throttle valves of the second system which are provided in the first and second oil passages on the downstream side of the hydraulic chamber and whose throttle cross-sectional area changes in association with the throttle valve of the first system in response to the steering torque. And Both are provided in parallel with a third system throttle valve whose throttle area changes in association with the first and second throttle valves corresponding to the steering torque, and in parallel with the third system throttle valve. A fourth system throttle valve whose throttle area changes independently of the other throttle valve in response to an external signal is at least one side of the first and second oil passages upstream or downstream of the hydraulic chamber. It is configured to be provided in a pair.

(Embodiment) An embodiment of a hydraulic control device for a power steering according to the present invention will be described below with reference to the drawings.

In FIG. 1, 10 is a hydraulic pump as a hydraulic source, and 11 is a reservoir tank. The oil passage C between the hydraulic pump 10 and the reservoir tank 11 branches into a first oil passage (I) and a second oil passage (II) on the way, and the inside of a power cylinder 12 separated by a piston 13 The left and right hydraulic chambers L and R communicate with each other. Corresponding to the right or left steering operation of the steering wheel 14, the hydraulic pressure from the hydraulic pump 10 is applied to the left and right hydraulic chambers R and L via the first and second oil passages (I) and (II). It works with a difference. In the first and second oil passages (I) and (II), the throttle valve 1 of the first system including variable orifices on the upstream sides of the left and right hydraulic chambers L and R, respectively.
R, 1L is the second, which is also a variable orifice on the downstream side
System throttle valves 2R and 2L are provided. Further, on the respective downstream sides of the second system throttle valves 2R, 2L, the third system throttle valves 3R, 3L composed of variable orifices and the fourth system throttle valve 4R,
4L are provided in parallel in pairs.

Further, in each of the first to third system throttle valves, for example, the three valves of the first system throttle valve 1L, the second system throttle valve 2L, and the third system throttle valve 3L are interlocked by steering in one direction. The throttle area changes in the reducing direction in response to the steering torque T described later. Ie steering wheel
The throttle areas A to A of the throttle valves 1L, 2L, 3L are changed based on the steering torque T due to the torsional elastic force of a torsion bar (not shown) generated by the turning operation of 14. . On the other hand, the vehicle speed v as an external signal
The operation signal Ov from the control unit U based on is input to the fourth system throttle valve 4L. That is, the detection signal Iv of the vehicle speed v detected by the vehicle speed sensor 16 is input to the control unit U, and the operation signal Ov controlled by the control unit U based on the detection signal Iv is the fourth system throttle valve 4L.
Is input to the throttle valve, the throttle area A is reduced and changed to a direction in which the throttle area is closed independently without being related to the three throttle valves of the first system to the third system. Depending on the steering in the opposite direction, the first system throttle valve 1R, the second system throttle valve 2R, the third system throttle valve 3R, and the fourth system throttle valve 4R operate in the same manner as above. 2 (a) to 2 (c) are characteristic line diagrams showing the correlation between the throttle areas A to A of the first to third throttle valves and the steering torque T, and FIG. 2 (d) is the fourth diagram. FIG. 6 is a characteristic diagram showing the correlation between the throttle area A of the throttle valves 4R and 4L of the system and the steering torque T.
As shown in FIGS. 2A to 2C, the throttle valve 1 of the first system 1
The R, 1L and the throttle valves 3R, 3L of the third system have a characteristic that they are closed by the steering torque T having a smaller value than the throttle valves 2R, 2L of the second system, respectively.

The third system throttle valve 3L and the fourth system throttle valve 4L are either upstream of the first throttle valve 1L (position a) or the first system throttle valve.
Between 1L and the hydraulic chamber R of the power cylinder 1 (position b), or between the second throttle valve 2L and the hydraulic chamber R (reference f)
Position). Similarly, the throttle valve 3R of the third system and the throttle valve 4R of the fourth system may be installed at any positions of d, e, and c in the figure. However, when installing at each value of a or b (d or e), it is assumed that the hydraulic characteristics of the first system throttle valve 1R (1L) and the second system throttle valve 2L (2R) are interchanged. Become.

Further, this is an embodiment in which a rotary valve 20 is adopted as the hydraulic control valve of FIG. 3, and the throttle valve 1R,
1L, 2R, 2L, 3R, 3L, 4R and 4L correspond to the throttle valves having the same signs as those in FIG. 1, respectively. The throttle valves 4R and 4L have the same throttle structure as the second spool valve 31 and the electromagnetic solenoid 32 shown in FIG. .

FIG. 4 shows an embodiment in which first and second spool valves 30 and 31 are adopted in place of the rotary valve 20. The throttle valves in the first and second spool valves 30 and 31 are designated by the same reference numerals in correspondence with the rotary valve 20 shown in FIG. That is, the opening degree of each throttle valve of the first system to the third system is changed by the movement of the first spool valve 30 which is interlocked with the steering operation of the steering wheel 14. Further, when the electromagnetic solenoid 32 is operated by the input of the operation signal Ov from the control unit U based on the vehicle speed v, the second spool valve 31
Moves to change the opening of the throttle valves 4R and 4L of the fourth system. As an actuator for moving the second spool valve 31, a stepping motor may be used instead of the electromagnetic solenoid 32 as in the embodiment.

Next, the operation will be described.

When the vehicle speed v is zero or when the vehicle is stationary, the steering torque T generated by one-directional steering operation of the steering wheel 14 corresponds to, for example, the throttle valve 1L of the first system.
Then, the throttle valve 2L of the second system and the throttle valve 3L of the third system are interlocked with each other to operate in the direction of reducing the throttle areas A, A, A. At this time, a detection signal Iv of zero or a vehicle speed v close to this detected by the vehicle speed sensor 16 is sent to the control unit U for control, and an operation signal from this control unit U is sent.
When Ov is input to the fourth system throttle valve 4L via the electromagnetic solenoid 32 of FIG. 4, etc., these fourth system throttle valve 4L act in the direction of contraction, and as shown in FIG. 2 (d). As shown, the diaphragm area A = 0 is closed. On the other hand, with the first system throttle valve 1R,
Each of the second system throttle valve 2R and the third system throttle valve 3R is in an open state. Therefore, in this case, only the throttle area A of the throttle valve 3L of the third system needs to be controlled,
If the throttle areas are sequentially added up from the second system to the first system and replaced by equivalent ones, the hydraulic characteristics of the entire hydraulic circuit show the closed state of the third system throttle valve 3L and the first system throttle valve 1L. The steering torque T in FIG. That is, the second
The system throttle valve 2L and the third throttle valve 3L are the fourth throttle valve 4L
Since the throttle area of A is A = 0, it can be regarded as a single throttle valve arranged in series and having an equal pressure loss. In this case, the throttle areas A and A of the throttle valves of the second system and the third system are PKg / c for the pressure drop in the second system.
If m ² and the pressure drop in the third system are PKg / cm ² , it can be obtained from the relational expression by P = K · Q ² / A ² and P = K · Q ² / A ² . However, K is ρ / 2g (ρ:
Oil specific gravity, g: gravitational acceleration), and Q represents the amount of passing oil.

From this, the total pressure drop PKg / cm ² is And the equivalent throttle area Ao when it is regarded as a single throttle valve
Is As a result, the aperture area characteristic as shown in FIG. 5, which is obtained by combining FIGS. 2 (b) and 2 (c), is obtained. Also, the equivalent aperture area above
The throttle area characteristic and the hydraulic characteristic seen from the whole hydraulic circuit by adding Ao and the throttle area A of the first system throttle valve 1R are as shown in Fig. 6 (a) and (b) from the relation of A = Ao + A. . That is, as is clear from this, when the vehicle speed v is zero or close to that when the vehicle is stationary, a high hydraulic pressure Po can be obtained with a relatively small steering torque Tc, and the steering wheel 14
The steering operation of can be performed lightly.

Further, during high-speed traveling, for example, the first system throttle valve 1L, the second system throttle valve 2L, the third system throttle valve
The throttle valve 3L of the system operates in the direction of reducing the throttle area A, A, A. Further, the vehicle speed v detected by the vehicle speed sensor 16 is controlled by the control unit U, and the operation signal Ov from the control unit U is input to the throttle valve 4L of the fourth system via the electromagnetic solenoid 32 of FIG. 4 or the like. When the throttle valve 4L of the fourth system is operated in a direction to expand the throttle area A, the throttle valve 4L in the open state is maintained to be linear with a constant throttle area A as shown in FIG. . In this case, the throttle area A of the throttle valve 3L of the third system and the throttle area A of the throttle valve 4L of the fourth system shown in FIG. The equivalent aperture area Ao can be the sum of A and A. That is, Ao = A + A, as shown in FIG. Further, the equivalent throttle area Ab obtained by adding the equivalent throttle area Ao and the throttle area A of the second system throttle valve 2L shown in FIG. 2B is as shown in FIG. 9, and is calculated by the following equation.

Further, the equivalent throttle area A seen from the entire hydraulic circuit by summing the above-mentioned equivalent throttle area Ab and the throttle area A of the throttle valve 1R of the first system is A = Ab + A, and FIGS. 10 (a) and 10 (b) As shown in Fig. 3, the characteristics of the entire hydraulic circuit are similar to those of the throttle valve 2L of the second system, and the steering operation of the steering wheel 14 is performed with a proper reaction force during high speed running. ing.

At low and medium speeds, the hydraulic characteristics corresponding to the region between zero and high vehicle speed in FIG. 10 (b) are obtained.
For steering operation in the opposite direction, the throttle valve 1 of the 1st system
The characteristics similar to the above can be obtained by R, the second system throttle valve 2R, the third system throttle valve 3R, and the fourth system throttle valve 4R.

(Effects of the Invention) As can be understood from the above, the hydraulic control device for the power steering according to the present invention communicates with each of the left and right hydraulic chambers of the power cylinder in which a hydraulic pressure difference is generated by the steering operation of the steering wheel. First and second
In the oil passage, the hydraulic circuit provided with the four throttle valves of the first system to the second system that changes corresponding to the steering torque as in the conventional device, and the third circuit that changes corresponding to the steering torque.
Since it has a configuration in which two throttle valves of the system and an external signal, for example, two throttle valves of the fourth system that change according to the vehicle speed are added, the oil can be used at a predetermined ratio corresponding to the conventional vehicle speed. Like the flow rate control method that controls the flow rate, if you set to secure the necessary amount of oil to perform sudden steering operation at high speed with a light steering force, the amount of oil at the time of stationary operation will be excessive, following this. Since it is supplied, it is possible to solve the problem that an excessive heat countermeasure is required due to the increase of the discharge capacity of the hydraulic pump. That is, in the present invention, if the minimum amount of oil required during stationary operation is secured, only the area of the throttle valve is controlled according to the vehicle speed during traveling, so that an insufficient amount of oil will occur during rapid steering at high speed. In comparison with the conventional flow rate control system, the hydraulic pump can be suppressed to the minimum necessary discharge capacity, so heat measures for the entire hydraulic control system due to the increase in the hydraulic pump discharge capacity can be taken. Reduce
In addition, it is possible to prevent an increase in size and reduce costs.
In addition, compared to the conventional hydraulic reaction force control method, a hydraulic reaction force piston is not required in addition to the hydraulic pressure control valve. Therefore, the number of members attached to this hydraulic pressure switching valve is reduced and the overall hydraulic control device is made compact. Can be realized.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a power steering hydraulic control device according to the present invention, and FIGS. 2 (a) to 2 (d) are area characteristic diagrams of throttle valves with variable orifices of first to fourth systems according to an embodiment. FIG. 3 is a hydraulic circuit diagram of an embodiment when a rotary valve is used as a hydraulic control valve, FIG. 4 is a hydraulic circuit diagram of an embodiment when a spool valve is used as a hydraulic control valve, and FIG. Is zero, the equivalent throttle area characteristic diagram in which the fourth system throttle valve, the third system throttle valve, and the second system throttle valve are sequentially added, and FIGS. 6 (a) and 6 (b) show the above fifth example.
FIG. 7 is a characteristic diagram showing the equivalent throttle area between the equivalent throttle area and the throttle area of the first system throttle valve, and the correlation between the hydraulic pressure and the steering torque. FIG. 7 is the area characteristic of the fourth system throttle valve at high speed. Fig. 8 is a characteristic diagram of the equivalent throttle area of the fourth system throttle valve and the third system throttle valve at high speed, and Fig. 9 is the equivalent throttle area of Fig. 8 and the throttle of the second system throttle valve. Equivalent area characteristic diagram with area,
FIGS. 10 (a) and 10 (b) are characteristic line diagrams showing the equivalent throttle area of the equivalent throttle area of FIG. 9 and the throttle area of the first system throttle valve and the correlation between the hydraulic pressure and the steering torque. 1R, 1L: 1st system throttle valve, 2R, 2L: 2nd system throttle valve, 3R, 3L: 3rd system throttle valve, 4R, 4L: 4th system throttle valve, 10 ... … Hydraulic source hydraulic pump, 11 …… Reservoir tank, 12 …… Power cylinder, R, L …… Left and right hydraulic chambers, 14 …… Steering wheel, 15 …… Torsion bar, 16 …… Vehicle speed sensor, 20 …… Rotary valve, 30, 31 ... First and second spool valves 32 ... Electromagnetic solenoid, U ... Control unit, A to A ... throttle area, T ... Steering torque.

Claims (1)

[Claims] 1. A first communicating with a hydraulic source and a reservoir tank
And the second oil passage communicates with the left and right hydraulic chambers in the power cylinder, respectively, and the hydraulic pressure from the hydraulic source causes a pressure difference between the left and right hydraulic chambers in the power cylinder in response to the steering operation of the steering wheel. And a pair of first-type throttles provided in the first and second oil passages on the upstream side of the hydraulic chamber and having a throttle area that changes in accordance with steering torque. Valve and a pair of second systems provided in the first and second oil passages on the downstream side of the hydraulic chamber and having a throttle area that changes in association with the throttle valve of the first system in response to the steering torque. And a throttle valve of No. 3, and the throttle area changes in association with the steering torque in association with the throttle valves of the first system and the second system.
A throttle valve of a system and a throttle valve of a fourth system which is provided in parallel with the throttle valve of the third system and whose throttle area changes independently of the other throttle valves in response to an external signal. And a pair of second oil passages that are provided on at least one of the upstream side and the downstream side of the hydraulic chamber with respect to the hydraulic chamber, and are provided in series with the throttle valves of the first system and the second system. Hydraulic control device.