JPS63188573A - Hydraulic control device for power steering - Google Patents

Abstract

PURPOSE:To enable the other actuator or oil pressure sensor to be ensured in both the intermediate working condition, by controlling an externally controlled throttle, provided in a bypass flow path, to be selected in an intermediate throttling area between the full closing and full opening. CONSTITUTION:A bridge circuit inserts inflow control throttles 1L, 1R, constituted of variable orifices, to be interposed in flow paths L1, L2 while outflow control throttles 2L, 2R to be interposed in flow paths L3, L4. Inserting variable throttles 3R, 3L to be interposed in the downstream of the inflow control throttles in the flow paths L1, L3, the first variable throttle communicates with the inflow control throttle by a bypass flow path L5. The bypass flow path L5 inserts an externally controlled variable throttle 5, controlling its throttling area in accordance with a car speed, to be interposed. The externally controlled variable throttle 5 is controlled by supplying a signal from a car speed sensor 16 to a control unit. And a differential pressure, generated between both ends of the externally controlled variable throttles 5, is supplied to a rear wheel steering power cylinder 18.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a hydraulic control device for power steering, and in particular, it is possible to control the hydraulic pressure of a power cylinder for front wheel steering by an actuator or a hydraulic pressure sensor other than the power steering for front wheel steering. The steering torque is supplied to the steering wheel, and these are operated according to the steering torque.

[Conventional technology]

Conventionally, as a hydraulic control device for power steering, the one described in, for example, Japanese Unexamined Patent Publication No. 85061/1988 is known.

In this conventional example, as an actuator other than the power steering for front wheel steering, an actuator of a rear wheel steering device is driven according to the steering torque to perform four-wheel steering.

[Problem that the invention seeks to solve]

However, in the conventional power steering hydraulic control device described above, a main pump dedicated to the power cylinder for front wheel steering and a sub pump dedicated to the power cylinder for rear wheel steering are connected in tandem on the output shaft of the engine. In addition, it is necessary to provide two types of hydraulic control valves, one for the front wheels and one for the rear wheels, which respond to the steering torque of the steering wheel, which increases the horsepower consumption of the engine due to both pumps, and requires two piping systems. Since the steering gear has two sets, the overall structure of the steering gear becomes large, making it difficult to install it in the engine compartment of the vehicle.In addition, the steering gear, pump, and piping are all special products, which increases manufacturing costs. There was a point.

[Means for solving problems]

In order to solve the above problems, the present invention connects four flow paths in an annular manner to form a hydraulic bridge circuit, and connects a front wheel steering power cylinder between connection points on one diagonal of the hydraulic bridge circuit. The left and right hydraulic chambers are connected, the connection point on the other diagonal is connected to a hydraulic power source, and an inflow control throttle that responds to the steering torque is connected to each flow path on the upstream side of the power cylinder for steering the front wheels. In a power steering hydraulic control device in which each flow path is provided with an outflow control throttle that responds to the steering torque, each of the upstream and downstream sides of at least one of the inflow control throttle and each outflow control throttle is provided. A first variable throttle that responds to the steering torque is inserted, and the throttle area is controlled by an external signal other than the steering torque in parallel with the front wheel steering power cylinder between the connection point between the first variable throttle and another control throttle. A bypass flow path is formed in which a controlled externally controlled variable throttle is inserted, and the differential pressure between both ends of the externally controlled variable throttle is supplied to an actuator or oil pressure sensor other than the front wheel steering power cylinder. It is said that

[Effect]

In this invention, the first
A variable throttle is inserted, a bypass flow path is provided between the connection point of the first variable throttle and the serial inflow control throttle or outflow control throttle, and an externally controlled variable throttle is provided in this bypass flow path,
The differential pressure generated at both ends of this external variable throttle is supplied to other actuators or oil pressure sensors other than the front wheel steering power cylinder, so by fully opening the externally controlled variable throttle, the differential pressure between both ends can be becomes zero and the actuator or oil pressure sensor becomes inactive.

On the other hand, when the external control throttle is fully closed, the differential pressure between both ends of the throttle becomes large, and the actuator or oil pressure sensor is activated.

Furthermore, by selecting the external control throttle to have a throttle area intermediate between fully closed and fully open, it is possible to ensure that other actuators or oil pressure sensors are in an operating state intermediate between the two.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a hydraulic system diagram showing a first embodiment of the present invention.

In the figure, 10 is a hydraulic pump and 11 is a reservoir tank, and these hydraulic pump 10 and reservoir tank 11 constitute a hydraulic power source.

A control valve 13 that controls a power cylinder 12 that generates a steering assist torque to a steering gear mechanism is inserted into the hydraulic pump 10 and the reservoir tank 11 can.

This control valve 13 has four flow paths, ~L4
It has a hydraulic bridge circuit 14 which is connected in an annular manner, and connection points CAI and CA2 on one diagonal line are connected to the hydraulic pump 1.
0 and the reservoir tank 11, and the other diagonal connection points C11l and CIl□ are connected to the left and right hydraulic chambers 12L and 12R of the power cylinder 12, respectively, so that the steering wheel 15 can be steered to the right or left. Correspondingly, the hydraulic oil from the hydraulic pump 10 is connected to the connection point C.
It is configured to act on the left and right hydraulic chambers 12L and 12R with a pressure difference via the flow path between AI and the connection points Cl11 and CIl□ and Lz.

Inflow control throttles IL and IR configured with variable orifices are inserted in the flow path and L2, and outflow control throttles 2L and IR configured with variable orifices are inserted in the flow path and L4, respectively. 2R is inserted. First variable throttles 3R and 3L are inserted in series with the flow path and downstream of the inflow control throttles IL and IR of L2, and these first variable throttles 3R and 3L are inserted in series therewith.
The variable throttles 3R, 3L and the inflow control throttles IL, IR are communicated by a bypass passage, and the bypass passage has a throttle area independent of the aforementioned throttles and determined according to the vehicle speed. An externally controlled variable diaphragm 5, which is an electromagnetic flow rate control diaphragm in which A is controlled, is inserted.

The inflow control throttles IL, IR1 and the outflow control throttles 2L, 2R
And the first variable throttles 3L and 3R are adjusted to the inflow control throttle LL by steering the steering wheel 15, for example, to the left.
, the outflow control throttle 2L and the first variable throttle 3L,
By steering in the right direction, the inflow control throttle IR, the outflow control throttle 2R, and the first variable throttle 3R are linked to each other, and the throttle area is changed in the direction of decreasing in response to the steering torque T, which will be described later. has been done. That is, based on the steering torque T caused by the torsional elastic force of a torsion bar (not shown) or the like generated by the steering operation of the steering wheel 15, the aperture area A r of each aperture IL, IR; 2L, 2R and 3L, 3R is determined. ; A z and A3 change. Here, the aperture characteristics representing the relationship between the aperture area and the steering torque T of each aperture IL, IR; 2L, 2R, 3L, and 3R are shown in FIG. 2(a), (bl and (), respectively.
They are selected as shown in C).

That is, each of the inflow control throttles IL and IR is
As shown in Figure (a), until the value of the steering torque T reaches the predetermined value T1, the line 1. As shown in , as the steering torque T increases, the aperture area decreases relatively steeply, and when it exceeds the predetermined value T1, it decreases relatively gently until the predetermined value T2, as shown by the straight line 11 □, and when it reaches the predetermined value T2 The aperture area is selected so that the aperture area is slightly larger than zero when it exceeds .

In addition, each of the outflow control throttles 2L and 2R is shown in Fig. 2 (
As shown in b), the predetermined value T of the steering torque T.

Until a larger predetermined value T1' is reached, the straight line 1. of the inflow control throttles IL and IR is maintained. The aperture area decreases relatively steeply as shown by a straight line "21" which is slightly gentler than that of , and the aperture area decreases from a predetermined value Ti' to a predetermined value T2' which is larger than the predetermined value T2.
The distance is the straight line mentioned above! ! , as shown by the straight line 12 □, which is slightly gentler than □, and the predetermined value T
2' or more, the aperture area is selected to be slightly larger than zero.

Furthermore, each of the first variable apertures 3L and 3R has a second
As shown in the figure (C1), the predetermined value T of the steering torque T, and
1' is a straight line "II" which is gentler than the straight line 121 of the outflow control throttles 2L and 2R.
As shown in , the aperture area decreases relatively steeply and reaches the predetermined value TI.
'' is selected so that the aperture area is slightly larger than zero.

Furthermore, the externally controlled variable diaphragm 5 receives the vehicle speed detection signal VD from the vehicle speed sensor 6 and supplies it to the control unit U, which converts it into an excitation current 9 whose current value corresponds to the value of the vehicle speed detection signal VD. By supplying this excitation current 9 to the externally controlled variable diaphragm 5, the
), the aperture area characteristics have been selected such that the aperture is fully open at low vehicle speeds, gradually decreases as the vehicle speed increases, and becomes fully closed at high vehicle speeds.

The differential pressure generated between both ends of the externally controlled variable throttle 5 is supplied to the rear wheel steering power cylinder 18 of the rear wheel steering device 17.

This rear wheel steering device 17 is configured such that driving force from an engine (not shown) is connected to a propeller shaft (not shown) and a differential gear device 1.
9 and a rear axle 20 and has a rear wheel 22 mounted, for example, on a semi-trailing arm 21, which semi-trailing arm 21 is mounted on a rear wheel member 23.

This rear wheel member 23 is attached to a vehicle body (not shown) via a bin 24 and a rubber insulator 25, and a piston rod 18a of a rear wheel steering power cylinder 18 is connected to a knuckle arm 26 via a tie rod 27. has. Note that 28 is an elastic body such as a return spring or a rubber bush for maintaining the rear wheel 22 in a neutral position.

The specific configuration of the control valve 13 is as follows:
As shown in FIGS. 6 to 6, it is composed of a rotary valve 30.

That is, within the valve housing 31, there is a valve body 32 connected to, for example, a binion of a rack-and-binion type steering gear, and a cylindrical valve rotatably disposed on the inner peripheral surface of the valve body 32 and connected to the steering wheel 15. It includes a shaft 33 and a torsion bar 34 disposed on the inner peripheral surface thereof and connected at one end to the steering wheel 15 and at the other end to a binion of a rack-and-binion type steering gear. Then, three sets of control valves 13 are attached to the low-resolution valve 30.
They are formed in parallel with an angular interval of 0 degrees.

Each of the control pulps 13 has three oil grooves -D3 extending in the axial direction and formed at equal angular intervals on the inner peripheral surface of the valve body 32, and three oil grooves -D3 formed on the outer peripheral surface of the valve shaft 33. Projections E1-E facing oil grooves ~D3
3, the outflow control throttle 2L is located at the counterclockwise edge of the oil groove D1 and the protrusion E, and the first variable throttle 3R is located at the clockwise edge of the oil groove D1 and the protrusion E1. The inflow control throttle IL is located at the counterclockwise edge of D2 and the protrusion E2, the inflow control throttle IR is located at the clockwise end of the oil groove D2 and the protrusion E2, and the inflow control throttle IR is located at the clockwise edge of the oil groove D2 and the protrusion E2.
The counterclockwise edges of the oil groove D3 and the protrusion E3 constitute a first variable throttle 3L, and the clockwise edges of the oil groove D3 and the protrusion E3 constitute an outflow control throttle 3R.

Then, the oil groove D2 of the valve body 32 is connected to the hydraulic pump 10.
The oil grooves F+ to F3 of the valve shaft 33 are connected to the reservoir tank 11 through oil passages and through holes formed in the valve shaft 33, and the oil grooves and the oil grooves are connected to the front wheel steering power cylinder. In the left pressure chamber 12L and right pressure chamber 12R of 12, oil grooves 01 to G3 between the protrusions E1 and 82 of the valve shaft 33 and oil grooves HI''H3 between the protrusions E2 and 83 are used as power cylinders for rear wheel steering. 18 left pressure chamber 18L and right pressure chamber 18H, respectively,
Furthermore, an externally controlled variable throttle 5 is connected between the oil grooves GA and 03. Here, valve shaft 3
The oil grooves F1 to Fff, G, to G3 and H3 to H3 formed on the outer circumferential surface of No. 3 are as shown in FIG. 5 and FIG. 6(a), respectively.
As shown in (b), adjacent oil grooves are formed by shifting their positions in the axial direction, and these oil grooves F, ~F3-Gl~G3
Hydraulic oil inlet/outlet holes J1-J formed in the valve body 32 and communicating with H1-H3 are bored straight in the radial direction.

On the other hand, the valve housing 31 includes a low-resolution valve 30.
A spool valve 35 that constitutes the externally controlled variable throttle 5 is formed integrally with the spool valve 35 . The spool valve 35 has a spool 37 that is slidably connected to an actuator 36a of an electromagnetic solenoid 36. An externally controlled variable throttle 5 is constituted by the oil groove M formed on the circumferential surface.

Note that the control valve 13 is not limited to the case where the control valve 13 is composed of the low-resolution valve 30, but as shown in FIGS. 7 and 8,
It may also be configured with a spool valve 40. That is, a spool valve 40 is formed in the steering gear housing 41 in a direction orthogonal to the pinion shaft 42, and a spool valve 42 that constitutes the externally controlled variable throttle 5 is formed orthogonal to the spool valve 40. There is.

The spool valve 40 has a spool 43 that slides in response to steering torque generated by steering the steering wheel 15, and has annular oil grooves P, ~P on the outer peripheral surface of the spool 43.
4 is formed. On the other hand, oil grooves Q1 to Q are formed on the inner circumferential surface of the housing 41 facing the spool 43 and communicate with each of the oil grooves P1 to P4 through slight gaps. Here, the inflow control throttle IR is in the communication part between the oil grooves P3 and Q2, the inflow control throttle IL is in the communication part between the oil grooves P2 and Q2, and the first variable throttle 3R is in the communication part between the oil grooves P2 and Q. , the first variable throttle 3L is in the communication part between the oil groove P3 and the oil groove Q3, the outflow control throttle 2R is in the communication part between the oil groove P4 and Q3, and the outflow control throttle 2R is in the communication part between the oil groove P
1 and Q constitute an outflow control throttle 2L, respectively.

Then, the oil groove Q2 is connected to the hydraulic pump lO, and the oil groove P and P
4 are connected to the reservoir tank 11 through an oil passage 46 bored in the spool 43, and oil grooves Q and Q3 are connected to the pressure chamber 12L of the front wheel steering power cylinder 12.
and 12R, oil grooves P2 and P3 are connected to pressure chambers 18L and 18R of the rear wheel steering power cylinder 18 and oil grooves K and M of a spool valve 42, which will be described later, respectively.

Further, the spool valve 42 is connected to the low re-valve 30.
It has exactly the same configuration as the spool valve 35 in
Corresponding parts are given the same reference numerals, and detailed description thereof will be omitted.

Next, the operation of the first embodiment will be explained. Assume that the vehicle is currently stopped, the steering wheel 15 is not being steered, and the front wheels and rear wheels are in a neutral position in which the vehicle is traveling straight. In this state, the throttles IL and IR to 3L of the control valve 13.

3R are fully open, and the vehicle speed detected by the vehicle speed sensor 16 is zero. Therefore, the external control variable throttle 5 is fully open, and the bypass flow path is closed. , and L2 are in communication.

Therefore, the entire amount of the hydraulic oil at a predetermined hydraulic pressure supplied from the hydraulic pump 10 is supplied to the hydraulic bridge circuit 14 of the control valve 13, and the flow path L4, the flow path L2, and the hydraulic bridge circuit 14 of the control valve 13 are Since the flow is divided into the same flow rate as L3, the front wheel steering power cylinder 12
The left and right hydraulic chambers 12L and 12R of the rear wheel steering power cylinder 18 and the left and right hydraulic chambers 18L and 18R of the rear wheel steering power cylinder 18 have the same pressure, and no differential pressure is generated between them. No steering assist torque is generated, and the front and rear wheels maintain a straight running state.

In this stopped state, if the steering wheel 15 is turned to the right, for example, to bring the vehicle to a stationary state, the apertures IR to 3R will interlock with each other in accordance with the steering torque at that time, and their aperture areas A and -A3 will move in the reduction direction. However, the other aperture IL
~3L remains fully open.

Therefore, the inflow control throttle IL is not inserted in the flow path L1, the first variable throttle 3L7!14 is not inserted in the flow path L2, and the outflow control throttle IL is not inserted in the flow path L4. 2L is not inserted, and the equivalent hydraulic circuit of the hydraulic bridge circuit 14 becomes as shown in FIG. 9(a).

Here, since the inflow control aperture IR and the externally controlled variable aperture 5 are in a parallel relationship, the aperture areas A+ and A of both can be regarded as a single equivalent variable aperture OA. The equivalent hydraulic circuit in a) can be rewritten as shown in FIG. 9(b).

In FIG. 9(b), the equivalent variable aperture OA is
Since the throttle area AA for the steering torque T is sufficiently large, it can be regarded as a simple flow path as shown in FIG. 9(C).

In this FIG. 9(C), since the first variable throttle 3R and the outflow control throttle 2R are in a parallel relationship, the total area of these throttle areas Az and As is the total area AI (=Az
+As> can be regarded as a single equivalent variable aperture OB, as shown in FIG. 9 (dl).

As is clear from FIG. 9(d), in the stationary state, both pressure chambers 18L, 1 of the rear wheel steering power cylinder 18
High-pressure hydraulic oil acts on each of 8R, and the differential pressure P between the two is zero, so the rear wheel steering power cylinder 18 maintains a neutral state and does not generate any steering force. However, regarding the front wheel steering power cylinder 12,
Equivalent variable aperture 0.0 mm inserted in parallel with this. Due to the existence of
When the above steering torque T is input, the left pressure chamber 12
The maximum oil pressure is supplied to L, and the right pressure chamber 12R becomes the drain pressure of the reservoir tank 11, so the differential pressure PF increases, and the steering assist torque generated in the power cylinder 12 increases accordingly, causing the steering wheel 15
The steering operation can be carried out lightly.

On the other hand, when the vehicle is traveling at a constant high speed, the vehicle speed sensor 16 outputs the high vehicle speed detection signal VD, and therefore the control unit U outputs an excitation current having a relatively high current value. Therefore, the aperture area A of the externally controlled variable aperture 5,
becomes fully closed. At this time, steering wheel 1
When the steering torque T is zero in a state where the power cylinder 12 is not steered and the steering torque T is zero, the corner throttle of the control valve 13 remains fully open as in the case of stationary operation, and the power cylinder 12.
There is no pressure difference between the two hydraulic chambers, and no steering force is generated by these power cylinders 12, 18.

However, when the steering wheel 15 is turned from the non-steering state to the right turning state, for example, when the steering wheel 15 is turned to the right, the control valve 13 is turned to the right.
The area of the aperture is reduced, and the apertures IL to 3L remain fully open. Therefore, the hydraulic bridge circuit 140 equivalent hydraulic circuit becomes as shown in FIG. 11(a).

Here, the first variable diaphragm 3R is fully closed due to a slight steering torque T, so in the normal steering state, it is fully closed and can be ignored.
The equivalent hydraulic circuit in a) can be rewritten as shown in FIG. 11(b).

Therefore, as is clear from this Figure 11 (bl),
Between the inflow control throttle IR and the outflow control throttle 2R, the former has a smaller throttle area with a smaller steering torque T than the latter, so as shown in FIG. With a small steering torque, the pressure difference between the left and right pressure chambers 18L and 18R becomes large, and a large steering force is generated to steer the rear wheels 23 in the same phase as the front wheels, and also to the power cylinder 12 for front wheel steering. is outflow control aperture 2R
As the steering torque T increases, the differential pressure between the left and right pressure chambers 12L and 12R gradually increases according to the throttle area characteristics of Steering wheel 1
The steering operation of No. 5 becomes heavy, and sudden steering can be prevented and steering stability can be improved.

In addition, in a running state intermediate between the stationary state and the high-speed running state, the pressure difference generated between the side pressure chambers of the front wheel steering power cylinders 1-2 and the rear wheel steering power cylinders 18 causes the front wheel steering power cylinders to 12 decreases as the driving state changes from low speed to high speed, and conversely, power cylinder 18 for rear wheel steering increases as the speed changes from low speed to high speed. Both front wheel steering and rear wheel steering functions, which require different hydraulic characteristics, can be reliably performed using two hydraulic power sources and one hydraulic bridge circuit.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this second embodiment, in the configuration of the first embodiment, a first variable throttle 3R is provided upstream of the power cylinder 12 of the hydraulic bridge circuit 14.

3L, and an outflow control throttle 2 on the downstream side of the power cylinder 12.
A first variable aperture 3R in series with L and 2R.

3L is arranged on the upstream side, and inflow control throttles IL, I
The aperture area characteristics of R and the aperture area characteristics of the outflow control apertures 2L and 2R are swapped, and the connection point between the first variable aperture 3L and the outflow control aperture 2R and the connection between the first variable aperture 3R and the outflow control aperture 2L are changed. It has the same configuration as the first embodiment described above, except that a bypass flow path with an externally controlled variable throttle 5 inserted between the point and the A detailed explanation thereof will be omitted.

According to this second embodiment, when the steering wheel 15 is turned to the right and the steering wheel is stationary, the equivalent circuit of the hydraulic bridge circuit 14 is as shown in FIG.
The first variable diaphragm 3L shown in Figure (a).

This means that the upstream and downstream sides of the other parts except 3R are reversed, but as in the first embodiment, the outflow control throttle 3R and the externally controlled variable throttle 5 are both in a parallel relationship,
In addition, since the externally controlled variable aperture 50 aperture area A is large,
These can be considered as mere oil passages, and as a result, the rear wheel steering power cylinder 18 is bypassed, as shown in FIG. 15, which corresponds to FIG. 10(d).
In addition, the equivalent variable aperture O6 of the aperture area Ac is expressed by the sum of the aperture area A2 of the first variable aperture 2R and the aperture area A3 of the first variable aperture 3R in parallel with the front wheel steering power cylinder 12. As a result, the front wheel steering power cylinder 12 has completely the same differential pressure characteristics with respect to the steering torque as in the first embodiment.

Similarly, even when driving at high speed, the front wheel steering power cylinder 12 and the rear wheel steering power cylinder 18 are connected in series.
The inflow control throttle IR and the outflow control throttle 2 are connected in parallel with each other.
R is connected, and a differential pressure is generated in the front wheel steering power cylinder 12 that gradually increases as the steering torque increases, and a differential pressure that gradually increases as the steering torque increases is generated in the rear wheel steering power cylinder 18. A differential pressure is generated which increases, and it is possible to generate a steering assist torque for the front wheels and a steering force for the rear wheels similar to those in the first embodiment.

Similarly, in intermediate driving conditions when stationary and high-speed driving,
The front wheel steering power cylinder 12 and the rear wheel steering power cylinder 18 can generate steering assist force and steering force exactly the same as in the first embodiment.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this third embodiment, in the first embodiment, the rear wheel steering device 17 is replaced with the rear wheel steering power cylinder 18.
Piston rods 51a of rear wheel steering power cylinders 51L and 51R fixed to vehicle body side members are connected to the left and right rubber insulators 25 of the rear wheel member 23, respectively.
Moreover, the pressure chamber 51b of the power cylinder 51L and the pressure chamber 51c of the power cylinder 51R are communicated with each other by a hydraulic pipe 52, and the pressure chamber 51b of the power cylinder 51L is connected to the pressure chamber 51c of the power cylinder 51R.
1c and the pressure chamber 51b of the power cylinder 51R are communicated with each other by a hydraulic pipe 53, and the power cylinder 51
The L pressure chamber 51b is connected to the externally controlled variable throttle 5 and the flow path L1.
It has the same configuration as the first embodiment except that the pressure chamber 51b of the power cylinder 51R is connected to the connection point between the externally controlled variable throttle 5 and the flow path L2. However, parts corresponding to those in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

Also in this third embodiment, the left and right rubber insulators 2 are
The structure is similar to that of the first embodiment, except that by pressing the rear wheels 22 in the opposite phase and slightly tilting the rear wheel members 23, the rear wheels 22 are steered in the same phase as the front wheels via the semi-trailing arm 21. Since the second embodiment has the following configuration, the same effects as those of the first embodiment can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

In this fourth embodiment, in the first embodiment,
A bypass flow path in which an externally controlled variable throttle 6 is inserted is connected in parallel with the power cylinder 12 for front wheel steering, and as shown in FIG. 18, the throttle area characteristics of the externally controlled variable throttle 6 change as the vehicle speed increases. The configuration is the same as that in FIG. 1 above, except that the number is selected to increase sequentially, and corresponding parts to those in FIG.

According to this fourth embodiment, when the vehicle speed is at or near zero and the steering wheel 15 is turned to the right, for example, in a stationary state, the externally controlled variable throttle 6 inserted in parallel with the front wheel steering power cylinder 12 is activated. Since it is in a fully closed state as shown in Fig. 18, the equivalent circuit is the 10th
Therefore, a large differential pressure is supplied to the front wheel steering power cylinder 12 in exactly the same way as in the first embodiment, so that the front wheel steering power cylinder 12 generates a large steering assist force. be able to.

On the other hand, when driving at high speed, the front wheel steering power cylinder 1
Aperture area A of externally controlled variable aperture 6 inserted in parallel with 2
6 is in an open state maintaining the predetermined value A, and its equivalent circuit becomes as shown in FIG. 19(a).

In this Fig. 19(al), the outflow control aperture 2R and the external control aperture 6 are in a parallel relationship, so if these are replaced with one equivalent variable aperture ○, the aperture will be as shown in Fig. 19(b). Area Ao is the aperture area A of the outflow control aperture 2R.
2 and the aperture area A6 of the externally controlled variable aperture 6. Therefore, the equivalent variable aperture is 0. Since the orifice area AC is sufficiently large, it can be considered as a mere oil passage, and therefore this equivalent variable orifice 0. The left and right pressure chambers 12L of the front wheel steering power cylinder 12,
Since 12R is bypassed, as shown in Figure 20,
The differential pressure between the pressure chambers 12L and 12R becomes approximately zero, which is equivalent to the manual steering state.

On the other hand, since the inflow control throttle IR is inserted in parallel with the power cylinder 18 for rear wheel steering, the differential pressure between the pressure chambers 18L and 18R depends on the throttle area characteristics of the inflow control throttle IR. As the steering torque increases, the power cylinder for rear wheel steering increases sharply.
8, it is possible to generate a large rear wheel steering force.

In addition, in intermediate driving conditions when stationary and high speed driving,
A steering assist force and a steering force intermediate between the two can be generated by the power cylinder 12 for steering one front wheel and the power cylinder 18 for steering the rear wheel.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

In this fifth embodiment, in the first embodiment,
Second variable throttles 4R and 4L are inserted in series on the downstream side of the outflow control throttles 2R and 2L in the flow paths L3 and L4 on the downstream side of the front wheel steering power cylinder 12, and the second variable throttles 4R and 4L are inserted in series therewith. A bypass flow path L6 is formed between the connection point and the connection point of the throttles 2L and 4L, and an externally controlled variable throttle 6 is inserted in this bypass flow path L6. It has a similar configuration, and corresponding parts to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. Here, the outflow control throttle 2L.

As shown in Fig. 22(a), the aperture area characteristics of 2R are relatively gentle so that the steering torque at the time of full closure is large compared to the aperture area characteristics of the outflow control apertures 2L and 2R in Fig. 1. The aperture area characteristics of the second variable apertures 4L and 4R are selected to have the same aperture area characteristics as the outflow control apertures 2L and 2R in FIG. 1, as shown in FIG. Similarly to the fourth embodiment, the aperture area characteristics of the externally controlled variable aperture 6 are selected such that the aperture area increases as the vehicle speed V increases, as shown in FIG. 18(b). .

According to the fifth embodiment, when the steering wheel 15 is turned to the right, for example, when the vehicle is stationary at a low vehicle speed running at or near zero, the external control variable throttle 6 is in the fully closed state, so that the bypass flow path is closed. is in a blocked state,
Therefore, in the flow path L3, the outflow control throttle 2R and the second variable throttle 4R are inserted in series. Therefore, if these two apertures 2R and 4R are regarded as a single equivalent variable aperture oE, the aperture area A-= can be expressed by the following equation.

At=□ ・・・・・・・・・・・・(1) J Hyakuro ■ Bow T Fu ■ 7 Here, the outflow control aperture 2R and the second variable aperture 4R are:
Since the throttle area A4 of the second variable throttle 4R is selected to be smaller for the same steering torque, the throttle area in the flow path L3 is dominated by the throttle area of the second variable throttle 4R, and is substantially Outflow control aperture 2 in the first embodiment
It becomes equal to R. Therefore, it is possible to generate a large steering assist force from the front wheel steering power cylinder 12, which is substantially the same as when the vehicle is stationary in the first embodiment.

In addition, during high-speed running, since the aperture area A6 of the externally controlled variable aperture 6 is a predetermined aperture area as shown in FIG. 19, the second variable aperture 4R and If the externally controlled variable aperture 6 is in a parallel relationship and both are considered as a single equivalent variable aperture OF, then the aperture area A,
F is expressed as the sum of the aperture area A4 of the second variable aperture 4R and the aperture area A6 of the externally controlled variable aperture 6, and since the aperture area is sufficiently large, it is possible to treat OF as a simple oil path. Therefore, it is equivalent to simply inserting only the outflow control throttle 2R in the flow path 3,
It is possible to generate a small steering assist force from the front wheel steering power cylinder 12, which is exactly the same as in the first embodiment, and to generate a large rear wheel steering force from the rear wheel steering power cylinder 1.
It can be generated from 8.

In this fifth embodiment as well, the bypass passage L6 is omitted and is replaced by a variable throttle 4L of the container cylinder 1.

Even if bypass channels are formed in parallel with 4R and externally controlled variable throttles 6 are inserted in each of these bypass channels, the same effect as described above can be obtained.

In addition, the above 4. Instead of providing the external variable throttle 6 in the fifth embodiment, the steering force of the power steering for steering the front wheels may be controlled based on the vehicle speed or the like using well-known reaction force control.

Next, a sixth embodiment of the present invention will be described with reference to FIG. 23.

This sixth embodiment is different from the hydraulic piping 5 in the third embodiment.
2.53, the hydraulic chamber 51C of the power cylinder 51R connected to the hydraulic pump 10 side and the power cylinder 5
It has the same structure as the third embodiment, except that it is connected to the 1L hydraulic chamber 51G by a hydraulic pipe 63, and can obtain the same functions and effects.

In addition, in the first to sixth embodiments described above, a case has been described in which the rear wheel steering power cylinder is applied as an actuator that utilizes the surplus hydraulic pressure of the front wheel steering power cylinder 12, but the present invention is not limited to this. , other vehicle-mounted actuators, etc. Also, surplus hydraulic pressure may be supplied to a pressure sensor to monitor the operating state of the front wheel steering power cylinder 12, and this pressure sensor may be supplied with surplus hydraulic pressure. It can also be used to diagnose abnormal conditions in the front wheel steering power cylinder 12 based on the detection signal, and in this case, it is possible to derive a smaller pressure than one that directly derives the pressure applied to the power cylinder, so the pressure sensor can be made smaller. It is also possible to use it as a steering torque sensor because it can produce linear hydraulic characteristics, unlike the hydraulic characteristics of power steering for front wheel steering.
It is also possible to actuate other actuators.

Further, in the first to sixth embodiments described above, a case has been described in which the externally controlled variable apertures 5 and 6 are controlled according to the vehicle speed, but the invention is not limited to this, and as shown in FIG. In place of the vehicle speed detection signal (2) from the vehicle speed sensor 16, the control unit U is supplied with a selection signal from a steering torque selector 60, which is comprised of a low-return switch, a variable resistor, etc., provided near the driver's seat, and this steering torque is By operating the selector 60, the excitation current Iv output from the control unit)
The value of is configured to be able to be changed arbitrarily, and the adjustment area A of the entire hydraulic bridge circuit 14 can be changed arbitrarily according to the driver's preference, and any steering torque can be applied to the power cylinder 12.18.
It may be generated by

Further, as shown in FIG. 25, a friction coefficient sensor 61 is provided to detect the friction coefficient of the road surface.
The optimum steering torque may be generated according to the friction coefficient of the road surface by changing the excitation current from the control unit U according to the friction coefficient detected value. That is, the friction coefficient detection value from the friction coefficient sensor 61 is supplied to the control unit l-U, and this control unit l-U sets the value of the excitation current Iv to a relatively small value when the friction coefficient is low, and to a large value when the friction coefficient is high. At the value, their intermediate friction coefficient is
Each is controlled to a value between the two. Here, the friction coefficient sensor 61 may be a changeover switch that works with a wiper switch, a raindrop sensor, or another device that indirectly detects the road surface friction coefficient, or one that detects the rotational speed of the front and rear wheels of the vehicle.
It is possible to directly detect the road surface friction coefficient by calculating the rotation speed difference between the two to calculate the friction coefficient, or by detecting the splash amount of the drive wheels to calculate the friction coefficient. In this case, the excitation current value calculated according to the vehicle speed may be corrected using the friction coefficient detection value of the friction coefficient sensor 61, not only when controlling the externally controlled variable throttles 5 and 6 only based on the road surface friction coefficient.

In addition, a sensor is provided to detect the operation of the acceleration/deceleration device of the vehicle, and the frequency of acceleration/deceleration of the vehicle is calculated based on the detected value of this sensor, and the running state of the vehicle is determined based on this, and the externally controlled variable aperture 5, 6 is determined. In the case where the vehicle speed is controlled by the vehicle speed, the vehicle speed sensitive pattern, that is, the aperture area characteristics with respect to the vehicle speed shown in FIGS. 2(d) and 18 may be changed. A sensor and a steering angular velocity calculation means for calculating a steering angular velocity by differentiating the output thereof are provided, and the vehicle speed sensitive pattern is changed based on the steering angle detection value of the steering angle sensor and the steering angular velocity calculation value of the steering angular velocity calculation means to cause a sudden turn. It may be possible to prevent the steering from occurring and improve the steering stability.Furthermore, a load sensor may be provided to detect the front wheel load of the vehicle, and the externally controlled variable apertures 5 and 6 may be controlled in accordance with changes in the front wheel load. It's okay.

Further, in the first to sixth embodiments described above, the case where a rack and pinion type was applied as the steering gear mechanism was described, but the invention is not limited to this, and other types of steering gear mechanisms may be applied. Needless to say.

〔Effect of the invention〕

As explained above, according to the present invention, the hydraulic pressure supplied to the front wheel steering power cylinder by one hydraulic bridge circuit has the necessary hydraulic characteristics as the rear wheel steering power cylinder. Since it can also be supplied to other actuators or hydraulic pressure sensors different from the above to operate them, only one hydraulic bridge circuit is required, and the overall configuration does not become large and manufacturing costs are reduced. Effects such as lower prices can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of a power steering hydraulic control device according to the present invention, and FIG.
d) is a characteristic diagram showing the throttle area characteristics of the inflow control throttle, the outflow control throttle, the first variable throttle, and the externally controlled variable throttle that can be applied to this invention, and FIG. 4 is a sectional view taken along the line B-B in FIG. 3, FIG. 5 is a perspective view showing an example of the valve shaft, and FIG. 7 is a sectional view showing an example of a spool valve applicable to the present invention; FIG. 8 is a sectional view taken along line ■-■ of FIG. 5; 9 (al to d) are explanatory diagrams for explaining the operation of the first embodiment in the stationary state, FIG. 10 is a characteristic diagram showing hydraulic characteristics with respect to the steering torque in the stationary state, and
Figures 1 (a) to (C) are explanatory diagrams for explaining the operation when turning right in a high-speed running state in the first embodiment, respectively, and Figure 12 is a characteristic line showing hydraulic characteristics with respect to steering torque during high-speed running. 13 are hydraulic circuit diagrams showing a second embodiment of the present invention, FIGS. 14 and 15 are explanatory diagrams for explaining the operation of the second embodiment in the stationary state, and FIG. 16 is a hydraulic circuit diagram of the second embodiment of the present invention. Fig. 17 is a hydraulic circuit diagram showing a fourth embodiment of the present invention, and Fig. 18 shows the aperture area characteristics with respect to steering torque of the externally controlled variable aperture 6 in the fourth embodiment. FIG. 19 (al and (b)) is an explanatory diagram for explaining the operation at the time of stationary steering in the fourth embodiment, and FIG. FIG. 21 is a hydraulic circuit diagram showing the fifth embodiment of the present invention, and FIGS. 22(a) and (bl are respectively the outflow control throttle and A characteristic diagram showing the aperture area characteristics with respect to the steering torque of the second variable aperture, FIG. 23 is a hydraulic circuit diagram showing a sixth embodiment of the present invention, and FIGS. 24 and 25 are respectively other embodiments of the present invention. In the figure, IL and IR are inflow control throttles, 2L and 2R are outflow control throttles, 3L and 3R are first variable throttles, 4L and 4R are second variable throttles, and 5 , 6 is an externally controlled variable throttle, 10 is a hydraulic pump, 11 is a reservoir tank, 12 is a front wheel steering power cylinder, 12L. 12R is a hydraulic chamber, 13 is a control valve, 14 is a hydraulic bridging circuit, and L1 to L4 are flow paths. , L5 is a bypass flow path, 15 is a steering wheel, 16 is a vehicle speed sensor,
U is a control unit, 17 is a rear wheel steering device, 18 is a power cylinder for rear wheel steering, 18L, 18R are hydraulic chambers, 30 is a rotary valve, 40 is a spool valve, 60 is a steering torque selector, and 61 is a friction coefficient sensor. be.

Claims (1)

[Claims] A hydraulic bridge circuit is constructed by connecting the four flow paths in an annular manner, and the left and right hydraulic chambers of the front wheel steering power cylinder are connected between the connection points on one diagonal of the hydraulic bridge circuit, and the hydraulic chambers on the other diagonal are The connection point is connected to a hydraulic power source, and an inflow control throttle that responds to the steering torque is provided in each flow path on the upstream side of the power cylinder for steering the front wheels, and an outflow control throttle that responds to the steering torque is provided in each flow path on the downstream side. In a power steering hydraulic control device each provided with a throttle, a first variable throttle that responds to steering torque is inserted on at least one of the upstream side and the downstream side of at least one of the inflow control throttle and each outflow control throttle, respectively. , a bypass flow in which an externally controlled variable throttle whose throttle area is controlled by an external signal other than the steering torque is inserted in parallel with the front wheel steering power cylinder between the connection point between the first variable throttle and the other control throttle; A hydraulic control device for power steering, characterized in that a pressure difference between both ends of the externally controlled variable throttle is supplied to an actuator or a hydraulic sensor other than a front wheel steering power cylinder.