JP2000289633A - Power steering gear and servo valve therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten steering at the beginning of steering by reducing a steering angle until a hydraulic cylinder is actuated as a result of being steered at a steering neutral point under a small fluid flow condition. SOLUTION: Pressure oil is supplied from a pressure oil pump through a flow rate control valve to a plurality of drain oil chambers 75 of a servo valve, wherein at least one of them is communicated with a drain oil hole 74, at least one of the others is communicated with a drain oil hole 74a having a throttle part 80, and oil feed chambers 77, 79 adjacent to each other on both sides of the drain chamber 75 communicated with the drain oil hole 74a having the throttle part 80 are communicated with oil feed holes 76a, 78a having a throttle part 81. It is thus possible to reduce a drain oil flow rate from the drain oil hole earlier than that of a drain oil hole having the same hole area and an existing servo valve, and increase a feed flow rate from the servo valve to the oil pressure cylinder, thereby raising the oil pressure to a prescribed value promptly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus provided with a servo valve for switching and supplying hydraulic oil from a hydraulic pump to a chamber of a hydraulic cylinder for assisting steering based on steering, and a servo valve used therefor. About.

[0002]

2. Description of the Related Art Recent automobiles are equipped with a number of hydraulically operated devices such as a power steering device and an automatic transmission, and a hydraulic pump for supplying hydraulic oil to these hydraulic operating devices is mounted. ing. Many of these types of hydraulic pumps are driven by using a part of the output of an engine, for example, by rotating a rotor by belt transmission via a power take-off pulley attached to the output end of the engine, Although it is configured to generate oil pressure according to the rotation of the rotor, when such a simple transmission configuration is adopted,
When the engine speed is high and the vehicle runs at high speed, the power loss for driving the hydraulic pump is large, leading to a reduction in fuel efficiency. In addition, if the specifications of the hydraulic pump are determined to reduce this power loss, the engine speed When the vehicle is running at a low speed or when the vehicle is stopped, the capacity of the hydraulic pump is insufficient, and there is a problem that a sufficient amount of hydraulic oil cannot be supplied to the hydraulic operating device.

As described above, in a hydraulic pump for an automobile, it is required to reduce unnecessary power loss of an engine serving as a drive source while securing a sufficient hydraulic oil amount when necessary. Therefore, the applicant of the present application has proposed a method in which the transmission means can be switched between high and low stages in the transmission system from the engine to the rotor, and the transmission means is operated by the action of hydraulic pressure generated in the discharge oil passage in accordance with the rotation of the rotor. A switching clutch for performing a switching operation, and when the steering assist hydraulic cylinder is operated by steering the steering wheel, the speed change means is moved to a high speed side by the action of the hydraulic pressure in the oil supply passage which rises with this. When the hydraulic cylinder is not operated without switching and steering, a hydraulic pump unit configured to switch the transmission means to a lower speed side is disclosed in Japanese Patent Application No. 10-107.
No. 70 proposed.

However, in a power steering apparatus in which the hydraulic pump unit constructed as described above is incorporated, when the speed change means is switched from the low-speed side to the high-speed side by the operation of the switching clutch, it is responded accordingly. The rotation speed of the hydraulic pump changes suddenly, and the hydraulic pressure in the oil supply passage rises sharply. As a result, the hydraulic oil from the hydraulic pump is switched based on steering and supplied from the servo valve to the hydraulic cylinder. There is a problem in that the flow rate supplied to the steering wheel suddenly changes, the steering assist force generated by the hydraulic cylinder changes suddenly, the operation feeling of the steering wheel changes suddenly, and the driver holding the steering wheel feels strange.

[0005] In order to solve such a problem, the present applicant has improved the one proposed in Japanese Patent Application No. 10-10770, and branches the middle of the oil supply passage communicating with the hydraulic pump to a drain oil passage. A branch portion, a throttle means for generating a differential pressure according to a supply flow rate to the hydraulic cylinder, and arranged at the branch portion;
Japanese Patent Application No. 10-126470 has proposed a hydraulic pump unit provided with a flow control valve for controlling the supply flow rate by opening and closing the drain oil passage by the action of the differential pressure.

In Japanese Patent Application No. 10-126470, when the hydraulic cylinder is not operated without being steered, the flow control valve opens the drain oil passage, and a part of the hydraulic oil sent from the hydraulic pump is opened. Is discharged to the drain oil passage through the branch portion, the hydraulic cylinder is operated by steering, the oil pressure inside the oil supply passage is increased, and the speed change means is switched to the high speed side by the operation of the switching clutch. The flow control valve operates in response to the increase in the differential pressure before and after the throttle means that accompanies this, the drain oil passage is closed, and the oil discharge flow rate to the drain oil passage is gradually reduced, and the oil flow to the hydraulic cylinder is reduced. Supply flow gradually increases,
Since the sudden change in the supply hydraulic pressure can be suppressed, the uncomfortable feeling can be reduced.

[0007]

By the way, in the case where the rotation speed of the hydraulic pump is switched between high speed and low speed as described above, the hydraulic pump rotates at low speed when the steering is not performed, and the hydraulic pump rotates at low speed. Is greater than the supply flow sent to the hydraulic cylinder from the
The input torque-pressure characteristic line draws a flared curve.

Therefore, as proposed by the applicant of the present invention, the switching clutch is operated by the action of the hydraulic pressure in the oil supply passage which rises with the steering operation. Steering, the steering angle until the pressure oil in the oil supply passage rises to a predetermined value required for operating the switching clutch becomes larger than a predetermined angle, and the hydraulic cylinder is operated by being steered from the steering neutral point. It is feared that steering becomes too heavy in the early stage of steering because the steering angle until the steering angle becomes large.

The present invention has been made in view of the above-described circumstances, and it is preferable that a throttle portion be provided in an oil discharge hole and an oil supply hole of a servo valve to which pressure oil is supplied from a hydraulic pump via a flow control valve.
Alternatively, by closing a part of the oil drain hole and the oil feed hole, when the steering starts from the steering neutral point at a small flow rate, the oil drain by the oil drain hole and the oil feed hole communicating with the oil drain hole. The flow rate can be reduced early, and the supply flow rate from the servo valve to the hydraulic cylinder can be increased quickly, the hydraulic pressure can be raised to a predetermined value early, and until the hydraulic cylinder operates at the beginning of steering. It is an object of the present invention to provide a power steering device and a servo valve capable of reducing the steering angle of the vehicle and reducing the steering angle.

[0010]

According to a first aspect of the present invention, there is provided a power steering apparatus comprising: a hydraulic pump; a hydraulic cylinder for steering assistance which communicates with the hydraulic pump via an oil supply path; A flow control valve provided, and a servo valve for switching and supplying pressure oil from the flow control valve to the chamber of the hydraulic cylinder based on steering, the servo valve having a relative angular displacement to a valve body. A plurality of oil supply chambers, a first intermediate pressure chamber, a second intermediate pressure chamber, and a first intermediate pressure chamber are provided in this order between the valve spool and the valve body, which are fitted as a valve. In the power steering apparatus, at least one of the second intermediate pressure chambers communicates with the oil drain hole, and at least one of the second intermediate pressure chambers is cut off from communication with the oil drain hole (or communicates with the oil drain hole having a throttle portion). ), The blocked second intermediate pressure chamber or throttle The first intermediate pressure chamber adjacent on both sides of the second intermediate pressure chamber communicating with the oil discharge hole having the portion is communicated with the oil supply hole having the throttle portion (or the communication with the oil supply hole is interrupted), The remaining first intermediate pressure chamber except for the first intermediate pressure chamber communicates with the oil feed hole.

According to a second aspect of the present invention, there is provided a power steering apparatus comprising: a hydraulic pump interlocked with a driving source via a speed change means; a hydraulic cylinder for steering assistance which communicates with the hydraulic pump via an oil supply path; A flow control valve provided in an oil passage, a servo valve for switching and supplying pressure oil from the flow control valve to the chamber of the hydraulic cylinder based on steering, and performing a shift operation to the transmission means based on steering. An oil supply chamber communicating with an oil supply hole, between the valve spool and the valve body, the first intermediate pressure chamber being provided between the valve spool and the valve body. In a power steering device in which a plurality of second intermediate pressure chambers and a plurality of first intermediate pressure chambers are provided in this order, the second intermediate pressure chamber is
At least one communicates with the oil drain hole, and at least one other is disconnected from the oil drain hole (or communicates with the oil drain hole having the throttle portion), and the second intermediate pressure chamber or The first intermediate pressure chambers adjacent on both sides of the second intermediate pressure chamber communicating with the oil drain hole having the throttle portion are communicated with the oil feed hole having the throttle portion (or the communication with the oil feed hole is shut off). The remaining first intermediate pressure chamber except for the first intermediate pressure chamber communicates with the oil feed hole.

[0013] A servo valve according to a third aspect of the present invention is an oil supply chamber communicating with an oil supply hole between a valve spool fitted to the valve body so as to allow relative angular displacement, and the valve body.
In the servo valve in which a plurality of first intermediate pressure chambers, a second intermediate pressure chamber and a first intermediate pressure chamber are provided in this order,
At least one of the intermediate pressure chambers communicates with the oil drain hole, and at least one of the other is shut off from communication with the oil drain hole (or communicates with the oil drain hole having the throttle portion). 2
The first intermediate pressure chambers adjacent on both sides of the intermediate pressure chamber or the second intermediate pressure chamber communicating with the oil drain hole having the throttle portion are communicated with the oil feed hole having the throttle portion (or cut off the communication with the oil feed hole). And the other first intermediate pressure chamber except for the first intermediate pressure chamber is communicated with the oil feed hole.

In the first invention, the second invention and the third invention, since the magnitude of the load applied to the hydraulic cylinder is small when the steering is not performed, the hydraulic oil supplied to the servo valve via the flow control valve is small. The total flow rate is returned to the oil tank or the like from the oil drain hole having the throttle portion and the oil drain hole not having the throttle portion. When steering starts from the neutral point of steering in this small flow rate, the magnitude of the load applied to the hydraulic cylinder gradually increases, the supply flow from the flow control valve to the servo valve gradually increases, and the valve spool of the servo valve rotates. Then, the valve opening gradually increases, and the flow rate supplied to the servo valve gradually increases.

At this time, (a) at least one of the second intermediate pressure chambers communicates with the oil drain hole, and at least one of the other second intermediate pressure chambers communicates with the oil drain hole having the throttle portion, and the oil drain having the throttle portion. A first intermediate pressure chamber adjacent to both sides of a second intermediate pressure chamber communicating with the hole;
An intermediate pressure chamber communicating with an oil feed hole having a throttle portion,
(b) at least one of the second intermediate pressure chambers communicates with the oil drain hole, at least one of the second intermediate pressure chambers communicates with the oil drain hole having the throttle portion, and the second second pressure chamber communicates with the oil drain hole having the throttle portion. Communication between the oil supply holes of the adjacent first intermediate pressure chambers on both sides of the intermediate pressure chamber is interrupted; (c) at least one of the second intermediate pressure chambers communicates with the oil discharge hole and at least one of the other One of the first intermediate pressure chambers which is closed on both sides of the second intermediate pressure chamber whose communication with the oil drain hole is interrupted and whose communication with the oil drain hole is interrupted.
An intermediate pressure chamber communicating with an oil feed hole having a throttle portion,
, The oil discharge hole and the oil supply communicating with the oil discharge hole are compared with those having an existing servo valve in which the opening area of all the oil discharge holes and the opening area of the oil supply holes are the same. The flow rate of oil drained by the holes can be reduced early, the flow rate of supply from the servo valve to the hydraulic cylinder can be increased early, and the oil pressure can be quickly increased to a predetermined value. Therefore, the steering angle from when the steering is started from the neutral steering point to the start of the operation of the hydraulic cylinder in a small flow rate can be reduced, and the steering can be lightened in the early stage of the steering.

Further, in the first invention and the second invention,
After the hydraulic pressure of the hydraulic oil supplied from the servo valve to the hydraulic cylinder has increased to a predetermined value, the flow rate will increase according to the valve characteristics of the flow control valve, and therefore, when the hydraulic cylinder starts operating, It is possible to eliminate the discontinuity of the pressure, and it is possible to prevent the driver performing the steering from feeling uncomfortable.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments thereof. Embodiment 1 FIG. 1 is a hydraulic system diagram of a power steering device, and FIG. 2 is a cross-sectional view of a switching portion for switching a rotation speed of a hydraulic pump.

The power steering apparatus of the present invention communicates with a drive source 1 which is an engine of an automobile via a transmission means 2 and a hydraulic pump 3 which is interlocked with a drive source 1 via a transmission line 4. And a hydraulic cylinder 5 for assisting steering
, A flow control valve 6 for controlling the flow rate of pressure oil sent to the hydraulic cylinder 5 in accordance with the magnitude of the load applied to the hydraulic cylinder 5, and a pressure from the flow control valve 6 based on steering. A servo valve 7 for switching and supplying oil to the chamber of the hydraulic cylinder 5 and a switching clutch 8 for causing the transmission means 2 to perform a shift operation based on steering.

The speed changing means 2 changes the rotational speed of the hydraulic pump 3 between a high speed and a low speed, for example, a planetary gear transmission or a planetary roller transmission.

The flow control valve 6 is formed with a spool chamber 60 having a circular cross section in a manner crossing the oil supply passage 4 in the middle of the oil supply passage 4.
Is configured.

FIG. 3 is a sectional view showing a schematic configuration of the flow control valve 6 part. As shown in FIG. 3, the spool chamber 60 has one side in the longitudinal direction upstream of the oil guide path 10 provided for guiding the pressure of the switching clutch 8 to the pressure oil chamber 9. 4 is formed so as to communicate with the middle. The other side of the spool chamber 60 communicates with a throttle means provided in the middle of the oil feed passage 4, specifically, a downstream side of the fixed throttle 61, via a pressure guide path 62 between the spool chamber 60 and the branch portion. Further, an intermediate portion of the spool chamber 60 communicates with a suction oil passage 11 (see FIG. 2) of the hydraulic pump 3 maintained at a low pressure through a drain oil passage 63 opened at the position.

The flow control valve 6 is provided in the spool chamber 6 as described above.
0, a first spool 6a having a bottomed cylindrical shape and slidably fitted in the axial direction, and a first spool 6
and a second spool 6b in the form of a column, which is slidably fitted in the axial direction in the inside of the inner spool a. A through-hole having a predetermined inner diameter is formed at the bottom of the first spool 6a, and a connecting rod 6c coaxially protruding from one side of the second spool 6b is formed in the through-hole. Fitted, first
A pressure receiving plate 6d having an outer diameter equal to that of the second spool 6b is coaxially fixed to an end of a connecting rod 6c protruding outside the spool 6a.

First spool 6a and second spool 6b
Is biased in a direction away from each other by a biasing spring 64 interposed between an inner bottom surface of the former and an end surface of the latter opposed thereto, and is integrated with the opening side of the first spool 6a. Is mounted inside the spool chamber 60 with the bottom face facing the communication side with the pressure guiding path 62, and the pressure receiving plate 6d and the spool facing the same. By a control spring 65 interposed between the end face of the chamber 60 and
The first spool 6 a is biased toward the direction away from the end face, that is, toward the communication side with the oil supply passage 4, and the opening side peripheral portion of the first spool 6 a is positioned so as to close the drain oil passage 63.

That is, the inside of the spool chamber 60 faces the opening side of the first spool 6a, and the inside of the spool chamber 60 faces the first pressure chamber 60a communicating with the oil supply passage 4 and the bottom side of the first spool 6a. The pressure guide path 62 is divided into a second pressure chamber 60b which communicates with the first pressure chamber 60b, and the drain oil path 63 communicates with the first pressure chamber 60a by an opening-side peripheral portion of the first spool 6a. Is shut off.

The arrangement chamber of the biasing spring 64 inside the first spool 6a is communicated with the opening of the drain oil passage 63 by a through hole 66 penetrating the peripheral surface of the first spool 6a. The sliding of the second spool 6b, which occurs with respect to the first spool 6a as will be described later, can be performed without any trouble due to the ingress and egress of oil generated through the through hole 66.

FIGS. 4 and 5 are explanatory diagrams of the operation of the flow control valve 6 configured as described above. The pressure oil discharged by the operation of the hydraulic pump 3 flows into the first pressure chamber 60a on one side of the spool chamber 60 through the oil supply passage 4 as shown by arrows in these figures, and The oil is supplied to the hydraulic cylinder 5 through the fixed throttle 61 disposed in the middle of the oil supply passage 4 on the downstream side.

At this time, pressure oil of a hydraulic pressure P 1 is introduced into the first pressure chamber 60 a, and a fixed throttle is provided to the second pressure chamber 60 b on the other side of the spool chamber 60 via the pressure guide path 62. A hydraulic pressure P2 downstream of 61 is introduced. This oil pressure P
2 is generated when the pressure oil sent to the oil supply passage 4 having the oil pressure P1 is reduced in pressure by passing through the fixed throttle 61, and the amount of the reduced pressure is the amount of pressure oil passing through the fixed throttle 61, that is, the hydraulic cylinder 5 The pressure difference between the first pressure chamber 60a and the second pressure chamber 60b increases with an increase in the supply flow rate, so that the pressure difference ΔP (= P1−P2) increases between the first pressure chamber 60a and the second pressure chamber 60b. Occurs.

Here, the second spool 6b receives the oil pressure P1 of the first pressure chamber 60a on one end face exposed to the opening side of the first spool 6a, and receives the oil pressure P1 of the second pressure chamber 60b.
2 is received by the end face of the pressure receiving plate 6d integrated on the same side. The pressure receiving plate 6d has an outer diameter substantially equal to that of the second spool 6b as described above, and The pressure receiving areas 60a and 60b have the same pressure receiving area. Therefore, the second spool 6b moves the first spool 6b in accordance with the increase of the differential pressure ΔP.
Pressed from the pressure chamber 60a toward the second pressure chamber 60b,
It moves toward the second pressure chamber 60b according to the force balance between this pressing force and the spring force of the control spring 65.

On the other hand, the first spool 6a receives the oil pressure P1 of the first pressure chamber 60a on the peripheral edge on the opening side, and receives the oil pressure P2 of the second pressure chamber 60b on the bottom surface. The area is larger in the latter. Therefore the first
Of the second pressure chamber 60b due to the pressure P2 of the second pressure chamber 60b applied to the bottom surface side, that is, the pressure P2 of the downstream side of the fixed throttle 61, not the action of the differential pressure ΔP.
b toward the first pressure chamber 60a, and according to the force balance between the pressing force and the spring force of the urging spring 64,
The second spool 6b relatively moves toward the first pressure chamber 60a.

The hydraulic pressure P2 generated downstream of the fixed throttle 61, for example, when the hydraulic cylinder 5 is not operated without being steered.
Is sufficiently small, the hydraulic pressure P1 of the first pressure chamber 60a, the hydraulic pressure P2 of the second pressure chamber 60b, and the differential pressure ΔP therebetween.
Are small, the first spool 6a and the second spool 6b move integrally from the assembling position shown in FIG. 3 to the left, and the drain oil passage 63 is slightly opened. Most of the pressure oil sent from the hydraulic pump 3 into the oil supply passage 4 is supplied to the hydraulic cylinder 5 via the fixed throttle 61.

From this state, the hydraulic cylinder 5 is operated by steering.
Operates and the hydraulic pressure P2 rises, the differential pressure .DELTA.P before and after the fixed throttle 61 also increases, so that the second spool 6b
Is that the pressing force due to the action of the differential pressure ΔP exceeds the spring force of the control spring 65 and the outer first
4 starts moving integrally with the spool 6a, and as shown in FIG. 4, the opening area of the drain oil passage 63 to the inside of the spool chamber 60 increases in accordance with this movement. Most of the supply flow rate supplied to the inside is drained to the low pressure side through the drain oil passage 63.

At this time, the oil discharge flow rate increases with an increase in the differential pressure ΔP before and after the fixed throttle 61, that is, with an increase in the supply flow rate.
Is maintained substantially constant irrespective of the increase in the rotation speed of the motor.

On the other hand, as described above, the first spool 6 pressed by the action of the hydraulic pressure P2 of the second pressure chamber 60b
In the case a, the pressing force by the hydraulic pressure P2 exceeds the spring force of the urging spring 64, and the relative movement with respect to the second spool 6b is started. As a result, as shown in FIG. 5, the opening area of the drain oil passage 63 to the inside of the spool chamber 60 is reduced, and the amount of oil drained to the low-pressure side via the drain oil passage 63 is reduced. 5, the supply flow rate increases as the hydraulic pressure P2 increases.

FIG. 6 is a flow characteristic diagram showing the relationship between the pressure of the pressure oil downstream of the flow control valve 6 and its flow rate. As shown in the drawing, the amount of oil supplied from the hydraulic pump 3 is kept substantially constant as shown in FIG. 3A while the hydraulic pressure P2 on the downstream side is small and the flow control valve 6 undergoes the state change shown in FIGS. While the hydraulic pressure P2 exceeds the predetermined limit pressure Ps and the flow control valve 6 undergoes the state change shown in FIGS. 4 and 5, the hydraulic pressure P2 increases as shown in FIG. P2
When the pressure rises to a predetermined oil pressure P, the flow rate on the downstream side returns to a large flow rate as shown in C. Therefore, the critical pressure PS
Is set to substantially match the rotational speed at which the transmission means 2 is switched to the high-speed side by the operation of the switching clutch 8, whereby a sudden change in hydraulic pressure before and after the switching can be prevented. The above-described setting of the limit pressure PS can be realized by appropriately selecting the pressure receiving area difference on both sides of the first spool 6a and the spring force of the biasing spring 64.

The servo valve 7 has a valve spool 7a connected to a steering wheel via an input shaft, and a valve body 7b inserted around the valve spool 7a and connected to an output shaft. The basic configuration of the valve spool 7a and the valve body 7b is the same as the existing one, and
Uses eight equally distributed servo valves. On the inner peripheral surface of the cylindrical valve body 7b, eight first oil grooves 70, each having the same width, are arranged side by side in the circumferential direction at equal intervals.
Similarly, on the outer peripheral surface of a thick cylindrical valve spool 7a having an outer diameter substantially equal to the inner diameter of the valve body 7b, similarly, eight second oil grooves 71 having the same width are provided in the circumferential direction. They are arranged side by side with equal distribution.

The valve spool 7a is fitted inside the valve body 7b so as to be rotatable coaxially, and these are connected to each other by a torsion bar 12 inserted inside the valve spool 7a. ing. The first oil grooves 70 and the second oil grooves 71 are staggered in the circumferential direction as shown in the neutral state where the torsion bar 12 is not twisted, and are adjacent to each other on both sides. It is positioned so that it can communicate with.

With the above construction, each of the first oil grooves 70 of the valve body 7b faces the land between the second oil grooves 71 of the valve spool 7a, and the second oil grooves 70 of the valve spool 7a. Each of the oil grooves 71 is opposed to a land between the first oil grooves 70 of the valve body 7b, and on the periphery of the fitting between the valve body 7b and the valve spool 7a, the first oil grooves 70 are formed. And eight oil chambers inside (between the groove edges on both sides in the width direction) and eight oil chambers on the outside (between the groove edges on both sides in the width direction) of the second oil grooves 71. And alternately arranged.

The valve body 7b and the valve spool 7a are capable of relative angular displacement within the range of torsion of the torsion bar 12 connecting the valve body 7b and the valve body 7b and the valve spool 7a. , 71... Acts between the groove edges on both sides in the width direction of the groove portions a and b that increase or decrease their communication areas (diaphragm areas) in accordance with the relative angular displacement.

Out of the eight oil chambers formed by the second oil grooves 71 of the valve spool 7a, every other oil chamber 4
First, each oil groove 7 penetrates the peripheral wall of the valve body 7b.
Are connected to the downstream side of the flow rate control valve 6 via the fixed throttle 61 through respective oil supply holes 72 having openings outside the oil supply chambers 1 and are supplied with hydraulic oil from the hydraulic pump 3. 73... On the other hand, the remaining four oil chambers penetrate the valve spool 7a in the radial direction, each of the oil drain holes 74 having an opening at the bottom of each oil groove 71, and the hollow portion inside the valve spool 7a. A second intermediate pressure chamber (hereinafter, referred to as an oil discharge chamber) 75 which is connected to the oil tank 13 serving as an oil discharge destination through which the oil is discharged, and serves as a passage for the oil discharged to the oil tank 13.
Is composed.

On the other hand, of the eight oil chambers formed inside the first oil grooves 70, the four oil chambers adjacent to the oil supply chambers 73 on the same circumferential side are the valve body 7b. Hydraulic cylinder 5 which is a hydraulic oil supply destination through each of the oil supply holes 76 which has an opening at the bottom of each oil groove 70.
Is connected to one of the cylinder chambers 5R.
A first intermediate pressure chamber (hereinafter referred to as a first oil supply chamber) 77 to R 77.
The other four are connected to the other cylinder chamber 5L of the hydraulic cylinder 5 through the same oil feed holes 78, and a first intermediate pressure chamber (hereinafter referred to as a first pressure chamber) to the cylinder chamber 5L. 2
79) are constituted. Therefore, on both sides of the oil supply chambers 73, an oil path is formed to reach the oil discharge chamber 75 through the first oil supply chamber 77 or the second oil supply chamber 79, respectively. The oil discharge chamber 75 and the oil supply chamber 79 communicate with each other through the throttle portion a, and the oil supply chamber 73 and the oil supply chamber 7
9 and the oil discharge chamber 75 and the oil feed chamber 77 are communicated via the throttle portion b.

The servo valve 7 configured as described above is a basic configuration of an existing eight equally-distributed type. In the present invention, as described above, the throttle portion 80 is provided at every other oil drain hole 74. , A first oil drain hole 74a having a throttle portion 80 on one side for each oil supply hole 72, and a second oil drain hole 74a having no throttle portion 80 on the other side.
The first and second oil transfer chambers 77 adjacent to each other on both sides of an oil discharge chamber 75 communicating with the first oil discharge hole 74a having the throttle portion 80 are provided. , 79
The oil feed holes 76, 78 communicating with the oil feed holes 76, 78 are provided with throttle portions 81, 81, which are used as first oil feed holes 76a, 78a.
The oil supply holes 76 and 78 communicating with the first and second oil supply chambers 77 and 79 adjacent to each other on both sides of the oil discharge chamber 75 communicating with the second oil discharge hole 74b having no opening do not have a throttle portion. This is the second
And oil flow holes 76b, 78b, and the oil discharge flow rate of the pressure oil supplied to all the oil supply holes 72.
a, 74b and the oil discharge holes 74a, 74b
Oil feed holes 76a and 76b or oil feed holes 78 communicating with
The average oil discharge flow rate was obtained by averaging a and 78b.

The throttle portions 80 and 81 are formed by using a tubular member such as a pipe.
4 and a first oil drain hole 74a provided with the throttle portion 80.
The oil drain flow rate of the second oil drain hole 74 without the throttle 80
b. In addition, the throttle unit 81
Into the oil feed hole 76 or oil feed hole 78 of the existing servo valve 7, and the first oil feed holes 76 a and 78 a provided with the throttle portion 81.
The oil discharge flow rate of the second oil feed hole 76 without the throttle 81
b, 78b, compared to the oil discharge flow rate.

FIG. 7 is a hydraulic characteristic diagram showing the relationship between the steering angle and the opening area of the oil drain hole and the oil feed hole of the servo valve 7.
The broken line in (a) is the configuration of the present invention, the solid line (b) and (a) is the existing configuration, and the solid line (b) in (c) and (a) is all of the oil drain holes in the existing configuration. And a throttle section 81 is provided in all of the oil feed holes. Throttle portions 80, 8 are provided in all oil drain holes 74 and all oil feed holes 76, 78.
7 does not have a large amount of opening area reduction at the initial stage of steering as shown by the solid line A in FIGS. 7B and 7A. When the throttle portions 80 and 81 are provided at 78, the opening area decrease amount at the initial stage of steering is constant as shown by the solid line b in FIGS. 7 (c) and 7 (a), and it does not change at all. A throttle portion 80 is provided in each of the oil drain holes 74 to form first and second oil drain holes 74a and 74b.
Oil supply holes 7 communicating with the first and second oil supply chambers 77 and 79 adjacent on both sides of the oil discharge chamber 75 communicating with the oil discharge hole 74a
6, 78 are provided with throttle portions 81, 81 so that the first oil feed hole 76 is provided.
In the present invention in which the a and 78a and the second oil feed holes 76b and 78b are used, the opening areas (b) and (c) can be changed to the averaged opening area as shown by the broken line in FIG. 7 (a). .

FIG. 8 is a hydraulic characteristic diagram showing the relationship between the steering angle and the hydraulic pressure controlled by the servo valve. By changing the oil discharge holes 74a, 74b and the oil feed holes 76a, 76b or the oil feed holes 78a, 78b for all the oil supply holes 72 to the averaged opening area, the flow rate control valve 6 allows the flow rate on the downstream side to be changed. Is a steering angle required to increase the oil pressure to a predetermined oil pressure P, when the steering angle becomes θ, the oil drain holes 74a, 74b and the oil feed holes 76a, 76b or the oil feed holes 78a, 78b. The aperture area of the aperture section 80,
When the steering angle is smaller than θ degrees, the oil is drained under the influence of the throttle portions 80 and 81, and a hydraulic characteristic corresponding to a small flow rate is obtained. The oil is discharged without being affected by 80 and 81, and the oil pressure characteristic of the existing eight equally-distributed servo valves, that is, a large flow rate as shown in FIG.

FIGS. 9 and 10 are explanatory diagrams of the operation of the servo valve 7 when steering starts. For example, as shown in FIG. 9, when the steering is steered rightward from the neutral steering point, the valve spool 7a rotates clockwise with respect to the valve body 7b, and the throttle portion a is gradually opened and the throttle portion b is gradually closed. And oil drain holes 7 arranged on both sides of all oil supply holes 72.
4a and 74b, and oil supply holes 78 arranged counterclockwise with respect to all oil supply holes 72.
The oil is supplied from the oil discharge holes 74a and 74b to the oil supply holes 76a and 76b while being discharged from the oil discharge holes 74a and 74b through the oil discharge holes 74a and 78b. Oil drain holes 74a and 74b when the
And the opening area of the oil feed holes 78a and 78b is
It is possible to approach the opening area of 0.81.

When the steering wheel is steered leftward from the steering neutral point as shown in FIG. 10, the valve spool 7a rotates counterclockwise with respect to the valve body 7b, and the throttle portion b is gradually opened and the throttle portion b is gradually opened. a is gradually closed, and oil drain holes 74a, 74b arranged on both sides of all the oil supply holes 72.
From the oil drain holes 74a, 74b while being drained directly from the oil drain holes 74a, 74b via oil feed holes 76a, 76b arranged clockwise with respect to all the oil feed holes 72. The oil discharge holes 74a and 74b and the oil feed holes 76 when the steering angle becomes θ by changing the amount of throttle by the throttle portions a and b.
The opening areas of the apertures a and 76b can be made closer to the opening areas of the aperture portions 80 and 81.

Next, the operation of the power steering apparatus configured as described above will be described. When the steering wheel is not steered, such as during idling, the magnitude of the load applied to the hydraulic cylinder 5 is small. Therefore, the transmission clutch 2 is switched to the low-speed rotation side by the switching clutch 8, and the hydraulic pump 3 is rotating at low speed. The flow rate of the pressure oil supplied from the pump 3 to the oil feed passage 4 is small as shown in FIG. Accordingly, the pressure oil supplied to the servo valve 7 via the flow control valve 6 has a total flow rate from the first oil drain hole 74a having the throttle portion 80 and the second oil drain hole 74b not having the throttle portion 80. It is returned to the oil tank 13 and the like.

The flow rate at which the oil is guided from the oil supply hole 72 to the oil supply chamber 73 is a small flow rate. Is 4
The oil is equally distributed to the oil passages on both sides of the
The first and second oil drain holes 74 which reach the oil drain chamber 75 via the oil feed chamber 77 and the second oil feed chamber 79 of
a, and flows into the hollow portion inside the valve spool 7a through the valves 74a, 74b, merges in the hollow portion, and is discharged to the oil tank 13. Therefore, the two cylinder chambers SR and SL of the hydraulic cylinder 5 connected between the oil supply chambers 77 and 79 and connected to them, respectively.
No pressure difference occurs between them, and the hydraulic cylinder 5 does not generate any force.

When the steering is performed from the steering neutral point in the state of the small flow rate, the magnitude of the load applied to the hydraulic cylinder 5 gradually increases, and accordingly, the pressure supplied to the servo valve 7 by the flow control valve 6 is increased. As the flow rate of the oil gradually increases, the valve spool 7a of the servo valve 7 rotates as shown in FIG. 9 or 10, and the valve opening gradually increases, so that the flow rate supplied to the oil supply hole 72 gradually increases. At this time, a throttle portion 80 is provided in at least one oil drain hole 74, and the throttle portion 80
Since a pair of throttle portions 81 are provided in a pair of oil feed holes 76 and 78 arranged on both sides of the oil drain hole 74a having
The opening area of all oil drain holes 74 and all oil feed holes 76, 7
8 can reduce the flow rate of oil drained by the oil drain hole 74 at an earlier stage as compared with the one provided with an existing servo valve having the same opening area, and also has the oil feed hole 76 or the oil feed hole 78.
The supply flow rate to the hydraulic cylinder 5 can be increased early, and the hydraulic pressure can be increased to a predetermined value Ps required for operating the hydraulic cylinder 5 at an early stage.

Therefore, the steering angle from the steering neutral point to the start of the operation of the hydraulic cylinder 5 at a small flow rate can be reduced, and the steering can be lightened at the beginning of steering.

When the oil pressure in the oil feed hole 76 or the oil feed hole 78 rises to the predetermined value PS, the switching clutch 8 is operated, the transmission means 2 is switched to the high speed side and the flow control valve 6 is operated. Since the above-described operation is performed, the hydraulic pressure of the pressure oil supplied to the hydraulic cylinder 5 continuously changes from the change in the rotational speed before the switching as shown in FIG. As a result, the asymptotic characteristics are exhibited, and the discontinuous portion can be eliminated. Further, since the steering angle from the steering neutral point to the start of the operation of the hydraulic cylinder 5 in a small flow rate state can be reduced, the transition length H from the small flow rate curve A to the multi-flow rate curve B is set to the value of the present invention. The transition length H1 proposed by a person can be made shorter than the previously proposed transition length H1, and the steering assist force generated by the hydraulic cylinder 5 does not change suddenly before and after the predetermined value Ps, making the driver who is steering feel uncomfortable. Never give.

Embodiment 2 FIG. 11 is a hydraulic system diagram of a power steering device. The power steering device of the second embodiment and the servo valve 7 used for the power steering device are as follows.
Instead of providing the throttle portion 81 in the oil feed holes 76 and 78,
Oil drain chamber 75 communicating with oil drain hole 74a having throttle portion 80
Oil supply holes 7 of a pair of oil supply chambers 77, 79 adjacent on both sides of
6 and 78, in other words, the oil supply holes 76a and 78a of the first embodiment are eliminated, and the drainage flow rate of the pressure oil supplied to all the oil supply holes 72. Oil drain hole 74
a and 74b are averaged, and the other configurations and operations are the same as those in the first embodiment. Detailed description and structure, operation, and effects are omitted.

The communication between the oil supply chambers 77 and 79 and the oil supply holes 76 and 78 is interrupted by, for example, the existing valve body 7.
b does not drill at least one pair of oil feed holes 76, 78, or drills through existing valve body 7b,
Oil drain chamber 75 communicating with oil drain hole 74a having throttle portion 80
The buried object is inserted into the oil feed holes 76 and 78 adjacent to each other on both sides to close the oil feed holes.

In the second embodiment, the pressure oil supplied to all the oil supply holes 72 is supplied to a pair of oil pressure chambers 75 adjacent to each other on both sides of an oil discharge chamber 75 communicating with an oil discharge hole 74a having a throttle portion 80. From the oil supply chambers 77, 79 through the oil supply holes 76, 78
The pressure oil supplied to all the oil supply holes 72... Without being discharged to the oil supply holes 4a and 74b is directly discharged to the oil discharge holes 74a and 74b, and the same operation and effect as in the first embodiment can be obtained. Can be

Embodiment 3 FIG. 12 is a hydraulic system diagram of a power steering device. The power steering apparatus according to the third embodiment and the servo valve 7 used for the power steering apparatus
Instead of providing the throttle portion 80 in the oil drain hole 74, the communication with the oil drain hole 74 of at least one of the oil drain chambers 75 is interrupted, in other words, the oil drain provided with the throttle portion 80 in the first embodiment. A pair of oil supply chambers 7 adjacent on both sides of an oil discharge chamber 75 in which communication with the oil discharge hole 74 is cut off without the hole 74a
7, 79, the oil feed holes 76a, 7
8a, and the oil discharge flow rate of the pressure oil supplied to all the oil supply holes 72 is equal to the oil discharge hole 74 and the oil supply holes 76a, 76a.
76b or an average oil discharge flow rate obtained by averaging the oil discharge flow rates by the oil feed holes 78a and 78b. Since other configurations and operations are the same as those of the first embodiment,
The common components are denoted by the same reference numerals, and detailed description, structure, operation, and effects thereof will be omitted.

The communication between the oil drain chamber 75 and the oil drain hole 74 is interrupted, for example, by not forming at least one oil drain hole 74 in the existing valve spool 7a, or by closing the existing valve spool 7a. The buried object is inserted and closed in the oil drain hole 74 of the oil drain chamber between the oil feed chambers 77 and 79 communicating with the oil feed holes 76a and 78a having the throttle portion 81 formed in the hole. .

In the third embodiment, the pressurized oil supplied to all the oil supply holes 72 is directly discharged from the oil discharge holes 74 and the communication with the oil discharge holes 74 is cut off. The oil is discharged from a pair of oil supply chambers 77 and 79 adjacent on both sides of the oil discharge chamber 75 to the oil discharge hole 74 via the oil supply holes 76a and 76b or the oil supply holes 78a and 78b. The same operation and effect as those of 1 can be obtained.

Fourth Embodiment A power steering apparatus according to a fourth embodiment and a servo valve 7 used for the power steering apparatus are not shown, but are provided separately from the valve spool 7a in the oil drain holes 74 of the first and second embodiments. Instead of inserting and forming the formed throttle portion 80 and inserting and providing the throttle portion 81 formed separately from the valve body 7b in the oil feed holes 76 and 78 of the first and third embodiments, a throttle is provided. Portion 80 is formed integrally with valve spool 7a, and
1 is formed integrally with the valve body 7b, and the other structures and operations are the same as those of the first, second, and third embodiments.
3, the detailed description and structure, operation,
The effect is omitted. In the fourth embodiment, an inexpensive configuration can be made using an existing servo valve.

The power steering apparatus according to the present invention is provided with, for example, a small-flow type hydraulic pump and a large-flow type hydraulic pump 3 in place of the speed change means 2, so that the steering wheel is not steered. May be configured such that a hydraulic pump of a small flow type is selected, and a hydraulic pump of a large flow type is selected when the hydraulic pump is steered from a steering neutral point and rises to a predetermined value necessary for operating the hydraulic cylinder 5. And
The point is that the flow rate can be changed between the small flow rate and the large flow rate.

In the first to fourth embodiments,
The servo valve 7 has an even number of oil drain holes having a plurality of oil drain holes 74, such as four, eight, twelve, fourteen, sixteen, and sixteen, and preferably eight or more. However, a servo valve having an odd number of oil drain holes may be used. In other words, at least one of the oil drain holes communicates with the oil drain hole 74, and at least one other oil drain hole is provided. The communication with the hole 74 is interrupted or communicated with the oil drain hole 74 a having the throttle portion 80, and the interrupted oil drain chamber (second intermediate pressure chamber) 7.
5 or a pair of oil feed chambers (the first intermediate pressure chamber) 75 adjacent to each other on both sides of an oil discharge chamber (second intermediate pressure chamber) 75 communicating with the oil discharge hole
The intermediate pressure chambers 77, 79 are in communication with the oil feed holes 76 a, 78 a, which block or communicate with the oil feed holes 76, 78. Oil hole 7
Any configuration may be used as long as it is in communication with 6,78.

[0060]

As described in detail above, according to the first, second and third inventions, all the oil discharge holes have the same opening area, and all the oil supply holes have the same opening area. Oil flow through the oil drain hole can be reduced earlier compared to those equipped with the existing servo valve, and the supply flow from the servo valve to the hydraulic cylinder can be increased earlier.
Since the hydraulic pressure can be increased to a predetermined value at an early stage, the steering angle from the steering neutral point to the start of the operation of the hydraulic cylinder in a state of a small flow rate can be reduced, and the steering is lightened at the beginning of steering. be able to.

Further, according to the first invention and the second invention,
When the hydraulic cylinder starts operating, it is possible to eliminate a discontinuous portion of the hydraulic pressure, and it is possible to prevent a driver performing a steering operation from feeling uncomfortable.

[Brief description of the drawings]

FIG. 1 is a hydraulic diagram of a power steering device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a switching portion for switching a rotation speed of a hydraulic pump of the power steering device according to the present invention.

FIG. 3 is a sectional view showing a schematic configuration of a flow control valve portion of the power steering apparatus according to the present invention.

FIG. 4 is an operation explanatory view of a flow control valve of the power steering apparatus according to the present invention.

FIG. 5 is an operation explanatory view of a flow control valve of the power steering apparatus according to the present invention.

FIG. 6 is a flow characteristic diagram showing the relationship between the pressure of the downstream pressure oil of the flow control valve of the power steering apparatus according to the present invention and the flow rate thereof.

FIG. 7 is a hydraulic characteristic diagram showing the relationship between the steering angle of the power steering apparatus according to the present invention and the opening area of the oil drain hole of the servo valve.

FIG. 8 is a hydraulic characteristic diagram showing a relationship between a steering angle of the power steering apparatus according to the present invention and a hydraulic pressure controlled by a servo valve.

FIG. 9 is a diagram illustrating the operation of the servo valve when steering of the power steering apparatus according to the present invention is started.

FIG. 10 is an explanatory diagram of the operation of the servo valve when steering of the power steering apparatus according to the present invention is started.

FIG. 11 is a hydraulic system diagram of Embodiment 2 of the power steering device according to the present invention.

FIG. 12 is a hydraulic system diagram of a power steering device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive source 2 Transmission means 3 Hydraulic pump 4 Oil supply path 5 Hydraulic cylinder 6 Flow control valve 7 Servo valve 7a Valve spool 7b Valve body 72 Oil supply hole 73 Oil supply chamber 74 Oil discharge hole 75 Oil discharge chamber 76, 78 Oil supply hole 77 , 79 Oil chamber 8 Switching clutch 80 Throttle section 81 Throttle section

Claims (3)

[Claims] 1. A hydraulic pump, a steering assist hydraulic cylinder communicating with the hydraulic pump via an oil passage, a flow control valve provided in the oil passage, and the flow control valve based on steering. And a servo valve for switching and supplying pressure oil from the hydraulic cylinder to the chamber of the hydraulic cylinder, and the servo valve includes a valve spool between the valve spool and the valve body, which are fitted to the valve body to enable relative angular displacement. In a power steering apparatus provided with a plurality of oil supply chambers, a first intermediate pressure chamber, a second intermediate pressure chamber, and a first intermediate pressure chamber, which are provided in this order,
At least one of the second intermediate pressure chambers communicates with the oil drain hole, and at least one of the second intermediate pressure chambers is cut off from communication with the oil drain hole (or is communicated with the oil drain hole having a throttle portion). The first intermediate pressure chamber adjacent on both sides of the second intermediate pressure chamber or the second intermediate pressure chamber communicating with the oil drain hole having the throttle portion is communicated with the oil supply hole having the throttle portion (or the oil supply hole). ), And the remaining first intermediate pressure chamber except for the first intermediate pressure chamber communicates with the oil feed hole. 2. A hydraulic pump interlocked with a drive source via a speed change means, a hydraulic cylinder for steering assist which communicates with the hydraulic pump via an oil passage, and a flow control valve provided in the oil passage. A servo valve that switches and supplies the hydraulic oil from the flow control valve to the chamber of the hydraulic cylinder based on steering, and a switching clutch that causes the speed change means to perform a shift operation based on steering. The servo valve includes an oil supply chamber, a first intermediate pressure chamber, a second intermediate pressure chamber, and a first intermediate pressure chamber that communicate with an oil supply hole between the valve spool and the valve body that are fitted to the valve body so that relative angular displacement is possible. In a power steering device in which a plurality of intermediate pressure chambers are provided in this order,
At least one of the second intermediate pressure chambers communicates with the oil drain hole, and at least one of the second intermediate pressure chambers is cut off from communication with the oil drain hole (or is communicated with the oil drain hole having a throttle portion). The first intermediate pressure chamber adjacent on both sides of the second intermediate pressure chamber or the second intermediate pressure chamber communicating with the oil drain hole having the throttle portion is communicated with the oil supply hole having the throttle portion (or the oil supply hole). ), And the remaining first intermediate pressure chamber except for the first intermediate pressure chamber communicates with the oil feed hole. 3. An oil supply chamber, a first intermediate pressure chamber, a second intermediate pressure chamber, and a first intermediate pressure chamber communicating with an oil supply hole between a valve spool fitted to the valve body so as to be capable of relative angular displacement and the valve body. In the servo valve in which a plurality of intermediate pressure chambers are provided in this order, at least one of the second intermediate pressure chambers communicates with the oil drain hole, and at least one of the second intermediate pressure chambers is cut off from the oil drain hole ( Or a first intermediate pressure chamber adjacent to both sides of the shut-off second intermediate pressure chamber or the second intermediate pressure chamber communicating with the oil drain hole having the throttle portion. Is communicated with the oil feed hole having the throttle portion (or the communication with the oil feed hole is interrupted), and the other first intermediate pressure chambers except the first intermediate pressure chamber are communicated with the oil feed hole. A servo valve.