JPH06329038A - Hydraulic power steering system - Google Patents

Abstract

PURPOSE:To clarify the neutral position of a steering system so as to obtain a feeling of moderation by setting the throttle area of a fixed throttle, provided on the second control part side, to the same value as or the less value than the throttle opening area regulated by the under lap quantity at the centering time of variable throttle valves provided on the second control part side. CONSTITUTION:Variable throttle valves forming a first control part 11 and a second control part 12 are all of a center-open type, and the variable throttle valve V1, V2 forming the first control part 11 is larger in the under lap quantity than the variable throttle valves V3, V4, V5, V6 forming the second control part 12. The factor for determining the oil pressure value of lateral cylinder chambers 9A, 9B is the throttle opening area of a right-side fixed throttle 14 provided at the second control part 12, that is, the oil pressure of the lateral cylinder chambers 9A, 9B is in the balanced state. A piston 91 in a power cylinder 9 is not thereby actuated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering device used in an automobile or the like, and more particularly, to prevent power assist force from working in the neutral position, thereby enabling the steering device to be in the neutral position. Clarify,
This is to try to get a sense of moderation.

[0002]

2. Description of the Related Art Generally, a hydraulic power steering apparatus is shown in FIG.
As shown in FIG. 5, a pump 50 for supplying hydraulic oil for power assist, a reservoir 990 for storing the hydraulic oil used for power assist, and the pump 50 and the reservoir 99.
0, a power assist unit having a control valve 100 that operates based on the operation of the steering device 40 and a power cylinder 90 that operates by receiving hydraulic oil supply from the pump 50 according to the operation of the control valve 100. Etc. And
In particular, when the control valve 100 is a rotary servo valve, the rotary servo valve has four variable throttle valves V _A , as shown in FIG.
The first control unit 10 based on a bridge circuit formed by a combination of V _B , V _C , and V _D and the one provided in the first control unit 10 have different throttle functions of the throttle valve. Four
The second control unit 20 is based on a bridge circuit formed by a combination of two variable throttle valves V _E , V _F , V _G , and V _H. These throttle functions, specifically, two sets of control units 10 and 20 each including a combination of variable throttle valves having different amounts of underlap in the valve land.
Are provided, and the power assist force is changed as shown in FIG. 6 by operating these based on the operation of the steering device 40. That is, the power assist force (P) is made to increase with an increase in the steering angle (θ) of the steering device 40, so that a comfortable steering feeling is given to the driver.

[0003]

In this conventional power steering apparatus, when the steering apparatus 40 is operated (steered) in FIG. 7, the control valve 1 is operated.
00, the control unit of either the first control unit 10 or the second control unit 20 forming the control valve 100 is immediately activated, and the power cylinder 9
Supply hydraulic oil to 0 to start power assist.
That is, as shown by the alternate long and short dash line in FIG. 6, the hydraulic oil is supplied to the power cylinder 90 even when the steering angle is at a small angle θ ₁ , and the power cylinder 90 has a small ΔP ₁ . The hydraulic fluid having hydraulic pressure is supplied. As a result, in the power steering apparatus, when the steering device (steering handle) 40 is steered even slightly in the neutral position, the power assist force having the value of ΔP ₁ is immediately applied. This may make the neutral position in steering unclear. Originally, in the neutral state, it is necessary to make the neutral position clear without giving power assist, thereby giving a feeling of moderation. However, in the related art, there is a possibility that such an ideal steering feeling (steering feeling) may be impaired. SUMMARY OF THE INVENTION It is an object (problem) of the present invention to provide a hydraulic power steering apparatus which solves such a problem and which provides a feeling of moderation at a neutral position.

[0004]

In order to solve the above-mentioned problems, the following measures are taken in the present invention. That is, a pump driven by an engine or the like to supply hydraulic oil to the power assist unit, and a supply path for guiding the hydraulic oil from the pump to the power assist unit,
From a power assist unit or the like having a control valve in the middle of the supply path that operates based on the operation of the steering device and a power cylinder that operates by receiving hydraulic oil supply from the pump in response to the operation of the control valve. In the above hydraulic power steering apparatus, the control valve is formed by a rotary servo valve, and a first control portion including two variable throttle valves is provided on a first land portion forming the rotary servo valve. And a second control unit including four variable throttle valves and two fixed throttles is provided on the left and right land portions (second land portion) of the first land portion. (2) The valve configurations of the variable throttle valves forming the control section are all center-open type, and the variable throttle valves on the first control section side are It is formed so that the amount of underlap in the valve mechanism section is larger than that of each variable throttle valve on the second control section side, and the throttle area of the fixed throttle provided on the second control section side is The variable throttle valve provided in the second controller is set to have a value equal to or smaller than the throttle opening area regulated by the amount of underlap during centering.

[0005]

With the above construction, the following actions are exhibited in the present invention. That is, in FIG. 1, when the pump 5, which is the hydraulic pressure supply source, starts operating, the hydraulic oil is discharged and supplied to the supply passage 52. This hydraulic oil is guided to the control valve 1 and further to the power assist section including the power cylinder 9 and the like via the supply passage 52. When the steering device 4 is operated (steered) in such a state, the control valve 1 operates via the steering shaft 41 connected to the steering device 4.

By the way, the control valve 1 is
Specifically, as shown in FIG. 2, the rotor 3 is composed of a rotary type servo valve mechanism, and is provided on the extension of the steering shaft 41, and the rotor 3.
And a sleeve 33 which forms a servo valve by performing relative rotational movement. The rotor 3 and the sleeve 33 are respectively provided with land portions 16 and 15 which form a variable throttle valve between them, and between the land portions, a first portion directly connected to the power cylinder 9 is provided. Center open type variable throttle valves V ₁ and V ₂ are provided on the land side, and the first control unit 1 has these two variable throttle valves V ₁ and V ₂ .
1 is formed. Therefore, by the operation of the first control unit 11, the operation of switching the hydraulic oil to the power cylinder 9 is performed.

Next, the hydraulic oil switched by the first control section 11 is controlled by the second control section 12 and sent to the cylinder chambers 9A and 9B of the power cylinder 9 to be used for power assist. Will be done. Then, in that case, in the next land portion (second land portion) provided on the left and right of the first land portion forming the first control portion 11,
As shown in FIG. 2, four variable throttle valves V ₃ , V ₄ , V ₅ ,
A second control unit 12 composed of V ₆ and two fixed throttles 13 and 14 is formed. Each of these variable throttle valves is of a center open type, and its underlap amount is shown in FIG. As described above, the variable throttle valves V ₁ and V ₂ forming the first control unit 11 are larger than the variable throttle valves V ₃ , V ₄ , V ₅ and V ₆ forming the second control unit 12. Therefore, the hydraulic oil is boosted by the second control unit 12 and sent to the power cylinder 9.

By the way, according to the present invention, since the first control section 11 and the second control section 12 having the above-mentioned structure are provided, the operation angle (steering angle) of the steering device 4 is obtained.
Within the range of a very small value of θ, that is, when the steering angle is small, the model of the hydraulic circuit is as shown in FIG. For example, in FIG. 2, when the rotor 3 is operated clockwise, the steering angle of the steering device 4,
That is, when the operating angle (θ) between the rotor 3 and the sleeve 33 is within the range of the value of θ ₁ in FIG. 4 or less, the pump 5 in FIG. The hydraulic oil supplied to 11 is distributed to the left and right by the first control unit 11, but at this time the variable throttle valve V ₂ is sufficiently open, so it also operates on the cylinder chamber 9B side of the power cylinder 9. Oil is supplied. Therefore, the left and right cylinder chambers 9A and 9B of the power cylinder 9 are hydraulically connected. The factor that determines the value of the hydraulic pressure in the left and right cylinder chambers 9A and 9B at this time is the throttle opening area of the right fixed throttle 14 provided in the second controller 12. That is, the hydraulic circuit model in FIG. 3 is established, and the hydraulic pressures of the left and right cylinder chambers 9A and 9B are in an equilibrium state here.

As a result, the differential pressure between the left and right cylinder chambers 9A and 9B in the power cylinder 9 becomes zero in the range where the valve operating angle is very small. Therefore, the relationship between the valve operating angle (θ) and the cylinder differential pressure (P) in the power cylinder 9 is as shown in FIG. 6, and within the range of the minute operating angle (θ ₁ ) the hydraulic pressure is as shown by the solid line. Does not stand up. As a result, the power assist force does not work near the neutral position of the steering device 4, and a moderation feeling in the neutral state can be obtained. This influence depends on how much the hydraulic oil is supplied to the power assist section, and becomes more remarkable as the hydraulic oil supply flow rate is smaller. Therefore, in general, a hydraulic power steering device is provided with a drooping function device that operates so as to reduce the amount of hydraulic oil supplied at high engine speeds or at high speeds, as shown in FIG. Therefore, the feeling of moderation at the neutral position can be remarkably obtained at high speed. Therefore, straight running stability can be obtained when traveling at high speed.

[0010]

Embodiments of the present invention will be described with reference to FIGS. As shown in FIG. 1, the configuration of the present embodiment has a pump 5 that is driven by an engine or the like to supply hydraulic oil to a power assist section, and a supply path for guiding the hydraulic oil from the pump 5 to the power assist section. 52, a vehicle speed-sensitive electromagnetic throttle valve 6 that reduces the throttle area when the vehicle speed detected by a vehicle speed sensor (not shown) becomes high in the middle of the supply path 52, and this electromagnetic throttle A bypass valve 7 for bypassing excess hydraulic oil to the reservoir 99 so as to maintain a constant differential pressure before and after throttling of the valve 6, and an operation (steering) of the steering device 4 on the downstream side of the electromagnetic throttle valve 6. And a power assist unit having a power cylinder 9 that operates by receiving the supply of hydraulic oil from the pump 5 in accordance with the operation of the control valve 1. The one in which the basic. By adopting such a configuration, the electromagnetic throttle valve 6 and the bypass valve 7 form a drooping function device that reduces the amount of hydraulic oil supplied to the power assist portion in response to an increase in vehicle speed. .

In such a basic structure, the control valve 1 which operates based on the steering of the steering device 4 is connected to the steering device 4 via the steering shaft 41 and is shown in FIGS. 1 and 2. As described above, the first control unit 11 that mainly performs the switching operation of the hydraulic oil and the second control unit 12 that controls the hydraulic pressure of the switched hydraulic oil are formed.

Further, the control valve 1
2 is a rotary type servo valve mechanism, as shown in FIG. 2. The rotor 3 is provided on an extension of the steering shaft 41, and a servo valve is formed by performing relative rotational movement with the rotor 3. It is composed of a sleeve 33 that operates. Then, the rotor 3 and the sleeve 33 are provided with a land portion which is between them and forms a variable throttle valve. That is, as shown in FIGS. 2 and 4, the land portion 1 is provided on the rotor 3 side.
6 and the land portion 16 are provided with a concave groove 18, and the sleeve 33 side is provided with the land portion 15 and the concave groove 17 is provided adjacent to the land portion 15. Further, in such a configuration, as shown in FIG. 2, among the concave grooves 17 provided in the sleeve 33, the side corresponding to the first land portion 16A of the rotor 3, that is, the first concave groove 17A, , A supply port 51 for receiving the supply of hydraulic oil from the pump 5, and further,
The land portions (first land portions) 15A and 15A ′ on the sleeve 33 side formed on the left and right of the first groove 17A are
The cylinders 9A and 9B of the power cylinder 9 are provided with distribution ports 39 and 39 'for distributing and supplying hydraulic oil. Further, between the land portions 16 and 15 having such a configuration, variable throttle valves V ₁ and V ₂ are provided between the first land portions 16A and 15A directly connected to the power cylinder 9, and these two variable valves are provided. The first control unit 11 is formed by the throttle valves V ₁ and V ₂ .

Next, the next land portions (second land portions) 16B, 16B 'provided on the left and right of the first land portion 16A on the rotor 3 side forming the first control portion 11 are shown in FIG. As shown in FIG. 2, discharge ports 82 connected to the return passages 8 that serve to return the hydraulic oil to the reservoir 99 are provided, and the fixed throttle 1 is provided in the middle of the discharge ports 82.
3 and 14 are provided. Between the rotor 3 and the sleeve 33 having such a configuration,
Land portions 16B, on both sides of 16B ', the variable throttle valve V ₃ as shown in FIG. _{2, V 4, V 5,} V 6 are provided, these four of the variable throttle valve V _3, V _4, V _5, The second control unit 12 is formed by V ₆ and the two fixed diaphragms 13, 14. The variable throttle valves forming the first control unit 11 and the second control unit 12 are both of the center open type, and their underlap amounts are as shown in FIG. The variable throttle valves V ₁ and V ₂ formed are larger than the variable throttle valves V ₃ , V ₄ , V ₅ , and V ₆ forming the second control unit 12. Note that, as shown in FIG. 2, such a control valve 1 is configured such that a plurality of sets (three sets in this embodiment) are provided on the shaft of the rotor 3 and the sleeve 33.

The operation mode of the present embodiment having such a configuration will be described. When the steering device 4 (see FIG. 1) is operated, the control valve 1 operates based on the operation. In that case, as shown in FIG. 2, the hydraulic oil is switched according to the operation of the first control unit 11 and the second control unit 12, and the variable throttle valves V _{1 to} V in the control units 11 and 12 are switched. _The hydraulic pressure is increased by the action of _{6 and the} like, and the hydraulic pressure is supplied to one of the left and right cylinder chambers 9A and 9B of the power cylinder 9. As a result, the power assist action is performed.

By the way, in this embodiment, since the first control section 11 and the second control section 12 having the above-mentioned configuration are provided, the first control section 11 and the second control section 12 are provided.
The throttle opening area (A) formed by each of the variable throttle valves V _{1 to} V ₆ constituting the above changes as shown in FIG. That is, in the range (θ ₁ ) where the steering angle (θ) is extremely small, the opening area (A) has a very large value, and the throttle portion in the control valve 1 at this time is a fixed throttle. Only 13 and 14 will exhibit the function. Therefore, when the steering angle (θ) of the steering device 4 is within a very small value range, that is, when the steering angle is small, the model of the hydraulic circuit is as shown in FIG.

From these facts, in FIG. 2, when the rotor 3 is operated clockwise, the steering angle of the steering device 4, that is, the operating angle (θ) between the rotor 3 and the sleeve 33 is as shown in FIG. 4, the hydraulic oil discharged from the pump 5 and supplied to the first control unit 11 is distributed to the left and right in the first control unit 11 in a range equal to or smaller than the value of θ ₁ in FIG. However, since the variable throttle valve V ₂ is still sufficiently open at this time, the hydraulic oil is also supplied to the cylinder chamber 9B side of the power cylinder 9. Therefore, the left and right cylinder chambers 9A of the power cylinder 9,
9B is hydraulically connected. The factor that determines the value of the hydraulic pressure in the left and right cylinder chambers 9A and 9B at this time is that the right fixed throttle 14 provided in the second control unit 12 is provided.
It becomes the aperture opening area of. That is, the hydraulic circuit model in FIG. 3 is established, and the hydraulic pressures of the left and right cylinder chambers 9A and 9B are in an equilibrium state here. Therefore, the piston 91 in the power cylinder 9 does not operate.

As a result, the differential pressure between the left and right cylinder chambers 9A and 9B in the power cylinder 9 becomes zero in the range where the valve operating angle is extremely small. Therefore, the relationship between the valve operating angle (θ) and the cylinder differential pressure (P) in the power cylinder 9 is as shown in FIG. 6, and within the range of the minute operating angle (θ ₁ ) the hydraulic pressure is as shown by the solid line. Does not stand up. As a result, the power assist force does not work near the neutral position of the steering device 4, and a moderation feeling in the neutral state can be obtained. This influence depends on how much the hydraulic oil is supplied to the power assist section, and becomes more remarkable as the hydraulic oil supply flow rate is smaller.

Therefore, in general, a hydraulic power steering system is provided with a drooping function device which operates so as to reduce the amount of hydraulic oil supplied during high-speed traveling, as shown in FIG. At times, a modest feeling at the neutral position can be remarkably obtained. Therefore, straight running stability can be obtained when traveling at high speed. Then, as the steering angle (θ) increases, the opening area of each variable throttle valve forming the control valve 1 sharply decreases as shown in FIG.
The left and right cylinder chambers 9A and 9B of the power cylinder 9 are hydraulically separated, and the hydraulic pressure of the hydraulic oil controlled by the control valve 1 is as shown by the solid line in FIG.
It will rise sharply. As a result, the steering angle (θ)
Becomes large, that is, when a certain amount of steering is performed, a sufficient power assist function is exhibited.

[0019]

According to the present invention, a pump driven by an engine or the like to supply hydraulic oil to a power assist section,
A supply path for guiding the hydraulic oil from the pump to the power assist section, a control valve that operates in the middle of the supply path based on the operation of a steering device, and the pump that operates according to the operation of the control valve. In a hydraulic power steering apparatus including a power cylinder and the like that operates by receiving hydraulic oil supply from the engine, the control valve is formed by a rotary servo valve, and a first land that forms the rotary servo valve. Is provided with a first control unit including two variable throttle valves,
A second control section including four variable throttle valves and two fixed throttles is provided on the left and right land sections (second land section) of the first land section, and the first control section and the second control section are provided. All of the variable throttle valves forming the above are configured as a center open type, and the variable throttle valves on the side of the first control unit are more variable than the variable throttle valves on the side of the second controller. It is formed so that the amount of underlap in the mechanism section is large, and the throttle area of the fixed throttle provided on the side of the second control section is the amount of underlap when the variable throttle valve provided in the second control section is centered. Therefore, when the steering angle of the steering device is small, that is, in the vicinity of the neutral position, Despite the rise in pump pressure, so as to prevent a rise in cylinder pressure difference, thereby,
The power assist force is not applied near the neutral position. Therefore, in the neutral state of the steering wheel, a feeling of moderation can be obtained, and straight running stability at high speed running can be obtained.

[Brief description of drawings]

FIG. 1 is a skeleton structure diagram showing an overall configuration of the present invention.

FIG. 2 is a skeleton structure diagram showing an overall configuration around a control valve according to the present invention.

FIG. 3 is an explanatory diagram showing a hydraulic circuit model in a neutral state in which a steering angle is within a range of a minute angle.

FIG. 4 is a diagram showing an underlap amount of a land portion of a variable throttle valve forming a control valve.

FIG. 5 is a diagram showing a change state of a throttle opening area of a variable throttle valve forming a control valve.

FIG. 6 is a diagram showing a relationship between a steering angle (valve operating angle) θ and a cylinder differential pressure P.

FIG. 7 is a skeleton structure diagram showing an overall configuration of a hydraulic power steering apparatus in a conventional example.

[Explanation of symbols]

1 Control valve 11 1st control part 12 2nd control part 13 Fixed throttle 14 Fixed throttle 15 Land part 16 Land part 17 Recessed groove 18 Recessed groove 3 Rotor 33 Sleeve 4 Steering device 41 Steering shaft 5 Pump 52 Supply path 6 Electromagnetic throttle valve 7 bypass valve 8 return path 81 exhaust port 82 exhaust port 9 power cylinder 9A cylinder chamber 9B cylinder chamber 91 a piston 99 reservoir V _1, V ₂ variable throttle valve (underlap Ryodai) V ₃ ~V ₆ variable throttle valve (underlap Small amount)

Claims (1)

[Claims] 1. A pump that is driven by an engine or the like to supply hydraulic oil to a power assist section, a supply path for guiding the hydraulic oil from the pump to the power assist section, and a midway point of the supply path. A hydraulic power steering system including a control valve that operates based on the operation of the steering device and a power assist unit that has a power cylinder that operates in response to the operation of the control valve by receiving hydraulic oil from the pump. In the device, the control valve is formed by a rotary servo valve, and a first control portion including two variable throttle valves is provided on a first land portion forming the rotary servo valve. Control consisting of four variable throttle valves and two fixed throttles on the left and right lands (second lands) of the And the valve configuration of each of the variable throttle valves forming the first control unit and the second control unit is a center open type, and each variable throttle valve on the side of the first control unit is The variable throttle valve on the second control unit side is formed so that the amount of underlap in its valve mechanism unit is larger, and the throttle area of the fixed throttle provided on the second control unit side is A hydraulic power steering characterized in that it is set to a value equal to or smaller than the throttle opening area regulated by the above-mentioned underlap amount at the time of centering the variable throttle valve provided on the control section side. Device.