JP3453841B2 - Hydraulic power steering - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering device used for an automobile or the like, and in particular, a power assist force does not work at a neutral position. The present invention relates to a hydraulic power steering apparatus in which neutral stiffness is increased as described above, and in an initial stage of steering, a power assist force is linearly exerted in accordance with a steering angle. 2. Description of the Related Art Generally, a hydraulic power steering apparatus is shown in FIG.
As shown in FIG. 7, a pump 50 for supplying hydraulic fluid for power assist, a reservoir 990 for storing hydraulic fluid for power assist, a pump 50 and a reservoir 99
The control valve 100 includes a control valve 100 that operates based on the operation of the steering device 40 and a power cylinder 90 that operates by receiving a supply of hydraulic oil from the pump 50 in accordance with the operation of the control valve 100. Note that in FIG.
Are shown in two places, but these are single. Then, in particular, when one in which the control valve 100 is composed of a rotary type servo valve, the rotary servo valve, as shown in FIG. 7, four of the variable throttle valve _{V A, V B, V C} , the V _D It is based on a bridge circuit formed in combination. By providing the control units 10 and 20 formed by these two sets of bridge circuits and operating them based on the operation of the steering device 40, the power assist force is changed as shown in FIG. . That is, the power assist pressure (P) increases as the valve operating angle (θ) based on the steering of the steering device 40 increases. [0003] In the above-mentioned conventional power steering device, as shown in FIG.
Is operated, the control valve 10
0 operates to supply hydraulic oil to the power cylinder 90. Based on these operations, a differential pressure is generated in the left and right cylinder chambers 90A and 90B in the power cylinder 90, and power assist is performed according to the differential pressure. Incidentally, the variable throttle valve forming the first control unit 10 and the second control unit 20 is not configured so that the state of the valve opening of the variable throttle valve changes linearly. Therefore, the hydraulic pressure (cylinder differential pressure) controlled by the control valve 100 and supplied to the power cylinder 90 and the power assist pressure formed by the cylinder differential pressure change in a quadratic curve as shown in FIG. It will be. That is, the change in the power assist pressure caused by the steering of the steering device 40 becomes non-linear and does not become linear as shown in FIG. This does not provide the steering operator with an accurate cutting feeling, which is not preferable in terms of steering feeling.
SUMMARY OF THE INVENTION It is an object (problem) of the present invention to provide a hydraulic power steering apparatus capable of obtaining a linear power assist effect in order to solve these problems. [0004] In order to solve the above problems, the present invention takes the following means. That is, a pump for supplying hydraulic oil to the power cylinder, a supply path for guiding hydraulic oil from the pump to the power cylinder, and a supply path provided in the middle of the supply path,
In a hydraulic power steering device including a control valve that operates based on the steering of a steering device and a power cylinder or the like that operates by receiving hydraulic oil from the pump in accordance with the operation of the control valve, the control valve includes: A first control unit comprising a center-open type variable throttle valve which is provided in a flow path connected to the pump and the reservoir and throttle-controls the hydraulic oil supplied from the pump in accordance with steering of the steering wheel, and the pump and the power cylinder An overlap-type variable throttle valve that is provided in a flow path connecting between the two oil chambers and controls throttle of hydraulic oil supplied from a pump to a power cylinder in accordance with steering of the steering device; and A sensor provided between the pump and the reservoir and provided in parallel with the power cylinder. A second control unit comprising an open type variable throttle valve, and further, the throttle area change ratio of the variable throttle valve in the first control unit, in which the throttle area is reduced and changed in accordance with steering, and the throttle area is In the initial stage of steering, the pump pressure introduced into the second control unit is a flat characteristic having a constant value. It was decided to adopt a configuration that was set to be as follows. [0005] By adopting the above configuration, the present invention has the following functions. When the steering device is steered, the respective variable throttle valves of the first control unit and the second control unit of the control valve are operated in response thereto. However, in the initial state of the steering operation, since the overlap type variable throttle valve forming the second control unit is closed or throttled, the cylinder differential pressure does not increase, and therefore, the power assist does not work. As a result, the steering rigidity near the neutral position is increased. In such a state, when the steering device is further operated, the variable throttle valve of the second control unit is gradually opened, and at the same time, the variable throttle valve of the first control unit is gradually closed. By controlling the rate of decrease and change in the throttle area of the variable throttle valve of the first control unit and the rate of increase and decrease of the throttle area of the variable throttle valve of the second control unit, in a state where the valve operating angle is relatively small, The pressure of the hydraulic oil introduced into the second control unit, that is, the pump pressure is set to a constant value, and does not change depending on the change in the steering angle.
Flat characteristics will be obtained. Accordingly, the hydraulic pressure introduced into the power cylinder changes linearly due to the throttle action of the center-open type variable throttle valve of the second control unit by the steering operation, and the moderator in accordance with the increase in the steering is provided to the driver. As a result, a long assist force is given. An embodiment of the present invention will be described with reference to FIGS. 1 to 6. As shown in FIG. 1, the configuration of the present embodiment supplies a pump 5 that is driven by an engine or the like and discharges a constant flow of hydraulic oil, and supplies the hydraulic oil from the pump 5 to a power assist unit including a power cylinder 9. Supply path 51
And provided in the middle of the supply path 51,
Control valve 1 connected to steering device 4
It is based on the following. In such a basic configuration, the control valve 1 is connected to a steering device 4 via a steering shaft 41 as shown in FIG. 1, and a rotary type servo valve which operates based on the operation of the steering device 4. It consists of The rotary type servo valve 1 mainly includes the pump 5 and the reservoir 99.
And a first control unit 11 that is connected to the pump 5, the power cylinder 9, and the reservoir 99, and controls the throttle of the hydraulic oil from the pump 5, The second control unit 12 supplies the pressure oil to the cylinder chambers 9A and 9B of the power cylinder 9. Each of the control units 11, 1
2, the first control unit 11 has a valve of the same form, that is, a land unit 35, as shown in FIG. 2, FIG. 3, and FIG.
The four center-open type variable throttle valves V ₁ , V ₂ , V ₃ , which have the same chamfer amount (chamfer angle) in A,
V ₄ , and these variable throttle valves V ₁ , V
₂ , V ₃ and V ₄ form a bridge circuit. Next, as shown in FIGS. 2, 3 and 4, the second control unit 12 also has four variable throttle valves V _{5 of} a center closed type on the upstream side and a center open type on the downstream side,
V ₆ , V ₇ and V ₈ , which form a bridge circuit. The first control unit 11 and the second control unit 12
The control valve 1 is provided with a rotary servo valve as shown in FIG. 2, and basically has a steering shaft 4 of a steering device 4.
1, a rotor 3 which operates in conjunction with the operation of the steering device 4 and a sleeve 2 which makes a relative rotational movement with the rotor 3 and forms a servo valve. The rotor 3 and the sleeve 2 include:
A land portion 3 which forms a variable throttle valve between them.
5, 25 are provided. The land portion 25 provided on the sleeve 2 side is provided with a supply port 29 connected to the supply path 51.
Reference numeral 9 denotes a structure in which four pieces are provided on the circumference of the sleeve 2 at 90 ° intervals. Further, the land portion 35 provided on the rotor 3 side is provided with chamfers forming a variable throttle valve, and the chamfer amount (chamfer angle) of these chamfers is as shown in FIGS. 4 and 5. What is provided on the land portion 35A of the first control unit 11 (V _{1 to} V
_The components (V ₇ , V ₈ ) provided on the land 35C of the second control unit 12 are formed to be larger (larger inclination angles) than ₄ ). A center-open type variable throttle valve (V _{1 to} V ₄ ) of the first control unit 11 and a center-close type variable throttle valve (V ₅ , V
Bevel angle of the relationship between _6), the steering and percentage reduction changes the aperture area of the variable throttle valve (V ₁ ~V ₄₎ by the percentage of expansion changes the aperture area of the variable throttle valve (V _5, V ₆₎ Is constant, that is, the total throttle area for controlling the pressure is kept constant regardless of the change in the steering angle. The sleeve 2 and the rotor 3 having the above-described construction are provided with grooves 26, 36 alternately with the lands 25, 35 next to the lands 25, 35. Groove 36 provided on the rotor 3 side
Has a configuration in which discharge ports 39 connected to the reservoir 99 are provided at 90 ° intervals. The operation of the embodiment having the above-described configuration will be described. That is, as shown in FIG. 1, when the steering device 4 is steered, the hydraulic oil discharged from the pump 5 and supplied to the control valve 1 via the supply path 51 changes according to the steering of the steering device 4. Aperture control. By the way, in this case, the control valve 1 has the first control unit 11 which does not directly supply the hydraulic oil to the power cylinder 9 and the steering angle of the steering device 4, that is, the valve operation angle has a certain value. And the second control unit 12 that supplies the hydraulic oil to one of the cylinder chambers 9A and 9B of the power cylinder 9 when the steering operation is performed. By the throttle control 11, the pump pressure introduced into the second control unit 12 has a certain pressure (P ₀ ) as shown by the broken line in FIG. 6, but as shown by the solid line in FIG. Does not go up, so power assist does not work. As a result, steering rigidity (handle rigidity) near the neutral position is increased. In such a state, when the steering device 4 is further steered, that is, when the valve operating angle (θ) of the control valve 1 increases, the second control unit 12 in FIG. 2 and FIG. The formed center-closed type variable throttle valves V ₅ and V ₆ are opened, and the hydraulic oil discharged from the pump 5 flows to the reservoir 99 via the variable throttle valves V ₇ and V ₈ . As a result, the pump pressure acts to increase due to the throttling action of the first control unit 11, but acts to decrease due to the opening of the second control unit 12. Then, the ratio of the reduction change of the variable throttle valve of the first control unit 11 and the ratio of the expansion change of the variable throttle valves (V ₅ , V ₆ ) of the second control unit 12 corresponding to the steering angle are made constant, and the total By keeping the throttle area constant, the steering angle of the steering device 4, that is, the valve operating angle (θ)
During a relatively small value of the pump pressure, the pump pressure will be kept constant. That is, as shown by the broken line in FIG. 6, the pump pressure introduced into the second control unit 12 is a constant value, does not change, and is in a flat state. As a result, the hydraulic pressure throttled by the hydraulic control valves V ₇ and V ₈ of the second control unit 12 and supplied to the power cylinder 9 changes linearly as shown by the solid line in FIG. That is, the power assist force changes linearly, and the power assist force changes linearly. As a result, the steering operator can obtain a comfortable assist feeling. In the above-described embodiment, an example has been described in which the upstream variable throttle valves (V ₅ , V ₆ ) in the second control unit 12 are configured as a center closed type, but this embodiment (the present invention). Does not necessarily need to be a center-closed type variable throttle valve, but may be a center-open type as shown in FIG. 5B or an overlap type. In short, the first control unit 1 by steering
Any variable throttle valve that can expand and change in accordance with the reduction and change of the first variable throttle valve and can make the pump pressure flat characteristics may be used. According to the present invention, the control valve is provided in the flow path connected to the pump and the reservoir, respectively, and the hydraulic oil supplied from the pump in response to the steering of the steering wheel is restricted. A first control unit comprising a center-open type variable throttle valve to be controlled, and a flow passage connecting between the pump and the oil chambers of the power cylinder,
An overlap-type variable throttle valve for throttle-controlling hydraulic oil supplied from a pump to a power cylinder in accordance with steering of a steering device, and a power cylinder provided in a flow path connecting between a pump and a reservoir; And a second control unit comprising a center-open type variable throttle valve provided in parallel to
A variable throttle valve in the first control unit in which the throttle area decreases and changes in accordance with the steering operation, and a variable throttle valve on the pump side among the variable throttle valves in the second control unit in which the throttle area expands and changes. The change rate of the aperture area
In the initial stage of the steering operation, the pump pressure introduced into the second control unit is set to have a constant flat characteristic, so that the differential pressure is applied to the power cylinder near the neutral position. Does not occur, therefore, the neutral rigidity is increased, and in a state where the steering device is steered, a cylinder pressure difference corresponding to the steering angle is generated linearly (linearly), giving the driver a sense of moderation. Power assist can now be applied.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an overall configuration of the present invention. FIG. 2 is a skeleton structure diagram showing a structure around a control valve according to the present invention. FIG. 3 is a development view in which a half circumference around a control valve according to the present invention is developed. FIG. 4 is a view showing an operation state of a land portion when the control valve according to the present invention is of a center closed type. FIG. 5 is a view showing an operation state of a land portion when the control valve according to the present invention is of a center open type. FIG. 6 is a diagram showing a relationship between a steering angle (valve operating angle) and generated pressure in the present invention. FIG. 7 is a block diagram showing the entire configuration of a conventional example. FIG. 8 is a diagram showing a relationship between a steering angle (valve operating angle) and power assist pressure in a conventional example. [Description of Signs] 1 control valve (rotary type servo valve) 11 first control unit 12 second control unit 2 sleeve 25 land 26 concave groove 29 supply port 3 rotor 35 land 36 concave groove 39 discharge port 4 steering device 41 Steering shaft 5 Pump 51 Supply path 9 Power cylinder 9A Cylinder chamber 9B Cylinder chamber 99 Reservoir

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideaki Sugiyama 1-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture Inside Toyota Koki Co., Ltd. JP-A-215462 (JP, A) JP-A-1-311955 (JP, A) JP-A-6-18149 (JP, U) JP-A-2-26974 (JP, U) (58) Fields investigated (Int. Cl) . ^7, DB name) B62D 5/083

Claims (1)

(57) [Claim 1] A pump for supplying hydraulic oil to a power cylinder, a supply path for guiding hydraulic oil from the pump to the power cylinder, and a supply path provided in the supply path And
In a hydraulic power steering apparatus comprising a control valve that operates based on steering of a steering device and a power cylinder that operates by receiving hydraulic oil from the pump in accordance with operation of the control valve, the control valve includes a pump. A first control unit including a center-open type variable throttle valve that is provided in a flow path connected to the pump and the reservoir, and that controls throttle of hydraulic oil supplied from the pump in accordance with steering of the steering device; An overlap type variable throttle which is provided in a flow path connected to each of the oil chambers and the reservoir of the cylinder and controls throttle of hydraulic oil supplied from the pump to the power cylinder in accordance with steering of the steering device. Provided in the flow path connecting the valve and the pump and the reservoir, A variable throttle in the first control unit, which is formed by a second control unit comprising a center-open type variable throttle valve provided in parallel with the power cylinder, and further has a throttle area reduced and changed in accordance with the steering of the steering device. The throttle area change rate of the valve and the throttle area change rate of the overlap type variable throttle valve in the second control section in which the throttle area expands and changes are introduced into the second control section in the initial stage of steering. A hydraulic power steering apparatus characterized in that the pump pressure is set so as to have a constant value and flat characteristics.