JP3767886B2 - Fluid control device for all hydraulic power steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a fluid control device used in conjunction with a hydraulic actuator such as a power steering cylinder operatively connected to a vehicle wheel, for example.
[0002]
[Prior art and problems to be solved by the invention]
For example, an all-hydraulic power steering system for an industrial machine such as a construction vehicle includes a fluid control device or fluid of the above type in cooperation with an actuator such as a double-acting power steering hydraulic cylinder operatively connected to wheels. Controllers are widely used. Such a fluid control device comprises a housing with two control ports leading to a hydraulic cylinder, an inlet port leading to a hydraulic source and an outlet port leading to a tank, and an inner cylinder mounted for rotation with a rotatable input means. A control valve or a switching valve set, which is composed of a shape spool and an outer sleeve which is nested with the spool and rotates following the spool, and determines a neutral position and a steering position according to the relative displacement of the spool and the sleeve A metering mechanism ("Gerotor set" or simply "Girotor") that measures the amount of pressurized oil metered in proportion to the rotational speed of the input means to the hydraulic actuator via the control valve by the cylinder circuit May be called). The gerotor is typically an internal tooth member (sometimes referred to as a ring) and an outer splined drive shaft that is eccentrically mounted within the internal tooth member and can rotate eccentrically. It includes a tooth member (sometimes called a star) and is adapted to meter the fluid flow through the control valve. As is well known, the number of teeth of the star of the gerotor is one less than the number of teeth of the ring. A measuring chamber is formed between the meshed inner teeth and outer teeth.
[0003]
The control valve is constituted by a pair of through grooves and holes provided in the spool and the sleeve, respectively, and further includes a variable orifice that forms a hydraulic circuit that bypasses the gerotor and thus the hydraulic actuator.
[0004]
The operation of the all-hydraulic power steering system incorporating the fluid control apparatus will be described with reference to a typical open center type hydraulic circuit shown in FIG. 1 and an exemplary control valve shown in FIG. Reference numeral 10 denotes a fluid control device used in an all-hydraulic power steering system, 12 denotes a gerotor incorporated in the fluid control device, 14 denotes a hydraulic actuator such as a double-acting cylinder connected to wheels, 16 denotes , the hydraulic pump 18, the reservoir or tank, 20 is a steering wheel, i.e. the handle, 22, the control valve, 24, a spool of the control valve, 26, the sleeve of the control valve 28 is connected to the handle Each input shaft is shown. Further, A2 to A5 are formed by a through hole 30 of the sleeve 26 of the control valve 22 and a through groove or hole 32 of the spool 24, and show variable orifices (see FIGS. 1 and 2) constituting a cylinder circuit, and An is A variable orifice (see FIGS. 1 and 2) formed by a through hole 34 of the sleeve 26 and a through groove or hole 36 of the spool 24 and constituting a cylinder bypass circuit is shown.
[0005]
When the user turns the handle 20 in either the left or right direction and the displacement angle of the spool with respect to the sleeve of the control valve exceeds a certain angle, the illustrated variable orifice A2 opens, and the high-pressure hydraulic oil from the hydraulic pump 16 enters the inlet port 38. Then, it flows to the gerotor 12. At substantially the same time, the variable orifices A3 and A4 are opened, and the high-pressure hydraulic oil of the amount Q1 measured by the gerotor flows through the control port 40 to the cylinder of the hydraulic actuator 14 to operate the hydraulic actuator. The amount Q1 of high-pressure hydraulic oil flowing through the cylinder circuit is proportional to the displacement of the gerotor and the rotational speed of the handle. On the other hand, a corresponding amount of hydraulic oil passes from the cylinder chamber on the opposite side of the hydraulic cylinder 14 through the control port 42 and returns to the tank 18 through the variable orifice A5 and the outlet port 44.
[0006]
The high-pressure hydraulic oil from the hydraulic pump that has not been diverted to the cylinder circuit bypasses the hydraulic actuator as the surplus flow Q2, and is returned to the tank 18 via the variable orifice An.
[0007]
By the way, when the excessive flow rate of the high-pressure hydraulic oil passes through the variable orifice An constituted by the through hole 34 of the sleeve 26 and the through groove or hole 36 of the spool 24, the conventional structure shown in FIG. It has been found that large and annoying noise is generated.
[0008]
FIG. 5 shows a partial cross-sectional view of a conventional variable orifice An with the spool and sleeve in a maximum relative displacement position of about 10 °, which comprises a stepped groove 36 'in the spool 24 and a sleeve hole 34'. In the structure of the variable orifice, as can be seen from the streamline indicated by the arrow, the flow field is turbulent (vortex, flow separation phenomenon, cavitation) at the edge shown in the figure. Conceivable.
[0009]
FIG. 6 shows another conventional variable orifice structure which also has a maximum relative displacement of about 10 ° between the spool and the sleeve, which variable orifice communicates with the through groove 34 ″ of the sleeve 26. The area of the spool groove 36 ″ that is open at the end is provided with a curved profile 37. In such a variable orifice structure, the use of the curved profile 37 avoids a rapid change in the flow path shape, and the noise level is improved as compared with FIG. However, forming the opening area of the spool groove in a curved shape in this way requires a special processing device, which increases the cost. Also, since two parts are used to form the sleeve groove, this also causes an increase in cost.
[0010]
An object of the present invention is to provide a fluid control device for an all-hydraulic power steering system that can be manufactured at a low cost with a very low noise level.
[0011]
[Means for Solving the Problems]
In view of the above object, the gist of the present invention is to rotate together with a housing having two control ports leading to a hydraulic actuator, an inlet port leading to a hydraulic source and an outlet port leading to a tank, and a rotatable input means. The inner cylindrical spool and the outer sleeve which are nested with the spool and rotate following the spool, and determines the neutral position and the steering position according to the relative displacement of the spool and the sleeve. And a metering mechanism for metering the amount of pressure oil measured in proportion to the rotational speed of the input means to the hydraulic actuator via the control valve. The control valve is provided in each of the spool and the sleeve. It has a variable orifice composed of through-grooves and through-holes. In all hydraulic fluid control apparatus for a power steering system for forming a hydraulic circuit for bypassing the metering mechanism and the hydraulic actuator office, so that noise generated when the hydraulic oil passes through the variable orifice becomes lower, cylindrical spool In the fluid control device, the outer peripheral surface is cut flat so that a flat surface is formed in a tangential direction in the opening region of the through groove.
[0012]
In a preferred embodiment, the angle formed by the radially extending side walls on both sides of the through groove of the spool and the flat surface of the spool is 90 °. A tapered clearance space is formed between the flat surface of the spool and the cylindrical inner peripheral surface of the sleeve.
[0013]
According to a feature of the invention, when the control valve is in the neutral position, the through groove of the spool and the through hole of the sleeve leading to the tank are aligned with each other, and when the control valve is in the steering position, The through hole of the sleeve communicates through a gap space, and the gap space, as viewed in cross section, smoothly spreads as a whole from the through hole of the sleeve toward the through groove of the spool. A part of returns to the tank via a hydraulic actuator bypass circuit including a gap space.
[0014]
In a preferred embodiment, the maximum clearance of the clearance space between the edge of the side wall of the through groove of the spool and the cylindrical inner peripheral surface of the sleeve is on the order of 0.1 mm.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
3 and 4 are partial cross-sectional views showing the structure of the variable orifice An of the present invention constituted by the slot-like through groove 36 (see FIG. 2) of the spool 24 and the circular through hole 34 of the sleeve 26. FIG. 3 shows the variable orifice An when the control valve is in the neutral position, that is, with the sleeve hole and spool through groove aligned. FIG. 4 shows the variable orifice An when the control valve is in the steering position, in other words, the spool groove center line L1 and the sleeve hole center line L2 form an angle of 0 to 10 °.
[0016]
According to an important feature of the present invention, the opening area of the spool through groove 36 to the cylindrical outer peripheral surface of the spool is cut flat in the tangential direction to form the flat surface 46, and the flat surface 46 and the sleeve of the spool are formed. Between the cylindrical inner peripheral surface 48, a tapered gap space 50 is formed as shown in the figure. It should also be noted that the angle α formed between the radially extending side walls 52a and 52b on both sides of the spool through groove 36 and the flat surface 46 of the spool is preferably about 90 °. The present inventor conducted experiments by setting the angle α to 90 °, 95 °, and 100 °. As a result, an excellent noise reduction effect was obtained when the angle α was 90 °. This will be described below with reference to FIG.
[0017]
Further, in the illustrated embodiment, the maximum clearance distance between the end edges 54 of the side walls 52a and 52b of the spool through groove 36 and the cylindrical inner peripheral surface 48 of the sleeve is in the 0.1 mm range.
[0018]
According to the above configuration of the present invention, even when the high pressure hydraulic oil passes from the sleeve through hole 34 through the clearance space 50 to the spool through groove 36 particularly at the steering position of the control valve of FIG. Significantly lower than the conventional configuration. A theoretical explanation of why the noise level is reduced by the configuration of the present invention is not given explicitly. However, it has been found that such noise reduction effect can be reliably obtained by the following experimental example.
[0019]
As described above, the results obtained by setting the angles α between the side walls 52a and 52b extending in the radial direction on both sides of the spool through groove 36 and the flat surface 46 of the spool to 90 °, 95 °, and 100 ° are obtained. This is shown in the graph of FIG. The vertical axis represents sound pressure (unit: dB (A)), and the horizontal axis represents load pressure (unit: MPa) at the inlet port 38. The outer diameter of the sleeve is about 42 mm, the diameter of the sleeve through hole is about 1.4 mm, the outer diameter of the spool is about 32 mm, and the width of the spool through groove (the distance between the side walls 52a and 52b) is about 1.2 mm. As described above, the maximum clearance distance between the end edges 54 of the side walls 52a and 52b of the through groove 36 and the cylindrical inner peripheral surface 48 of the sleeve was about 0.1 mm.
[0020]
In FIG. 7, the curve indicated by “x” indicates the noise level of the conventional configuration shown in FIG. 5, the curve indicated by “■” is the noise level when the angle α is 90 °, and the curve indicated by “Δ” is The noise level when the angle α is 95 °, and the curve indicated by “◇” indicates the noise level when the angle α is 100 °. As is apparent from the graph, it can be understood that a significant noise reduction effect is obtained when the angle α is 90 °.
[0021]
In the present invention, the flow path shape of the flow path of the high-pressure hydraulic oil probably flows from the sleeve through hole through the gap space to the spool through groove and is relatively smooth and widens toward the spool through groove. It seems that the disturbance of the flow field that causes it is limited, and noise generation is suppressed. Further, the processing for obtaining the tapered structure of the present invention is easier than the curved surface structure shown in FIG. 6, and the fluid control device can be manufactured at a low cost according to the present invention.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram of an open center type fully hydraulic power steering system.
FIG. 2 is an exploded perspective view of a control valve according to the present invention, showing a spool groove, a through groove or a through hole and a through hole of a sleeve forming a variable orifice.
FIG. 3 is a partial cross-sectional view showing a variable orifice constituted by a through groove of a spool of the present invention and a through hole of a sleeve in a state where a control valve is in a neutral position.
FIG. 4 is a partial cross-sectional view showing a variable orifice formed by a through hole of a spool and a sleeve of the present invention in a state where a control valve is in a steering position.
FIG. 5 is a partial cross-sectional view of a conventional variable orifice.
FIG. 6 is a partial cross-sectional view of another conventional variable orifice.
FIG. 7 is a noise level comparison diagram of the fluid control device of the present invention and the conventional fluid control device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fluid control apparatus or orbit roll 12 Metering mechanism part or gerotor 14 Hydraulic actuator 16 Hydraulic pump 18 Tank or reservoir 20 Handle 22 Control valve 24 Spool 26 Sleeve 28 Input shaft 30, 34 Sleeve through-hole 32 Spool groove or hole 36 Spool Through-groove A2, A3, A4, A5, An variable orifice

Claims (6)

A housing with two control ports leading to the hydraulic actuator, an inlet port leading to the hydraulic source and an outlet port leading to the tank, an inner cylindrical spool and spool and nesting mounted for rotation with a rotatable input means It is composed of an outer sleeve that rotates in response to the spool, and is controlled in proportion to the rotational speed of the input means, a control valve that determines a neutral position and a steering position according to the relative displacement of the spool and the sleeve. A metering mechanism that feeds a specified amount of pressurized oil to a hydraulic actuator via a control valve, and the control valve is a variable orifice composed of a through groove and a through hole, each of which is provided in a spool and a sleeve. The variable orifice has a metering mechanism and a hydraulic actuator. In all hydraulic fluid control apparatus for a power steering system for forming a hydraulic circuit which bypasses the over data,
The cylindrical outer peripheral surface of the spool should be cut flat so that a flat surface is formed tangentially in the opening area of the through groove so that the noise generated when the pressure oil passes through the variable orifice is reduced. A fluid control device.   The fluid control device according to claim 1, wherein the radially extending side walls on both sides of the through groove of the spool and the flat surface of the spool intersect at an angle of 90 °.   3. The fluid control device according to claim 1, wherein a tapered clearance space is formed between the flat surface of the spool and the cylindrical inner peripheral surface of the sleeve.   When the control valve is in the neutral position, the through groove of the spool and the through hole of the sleeve leading to the tank are aligned with each other, and a part of the pressure oil from the hydraulic source returns to the tank via the hydraulic actuator bypass circuit The fluid control apparatus according to claim 3.   When the control valve is in the steering position, the through-hole of the spool and the through-hole of the sleeve communicate with each other through a gap space, and the gap space is viewed from the cross-section and is entirely viewed from the through-hole of the sleeve toward the through-groove of the spool. 4. The fluid control device according to claim 3, wherein a part of the pressure oil from the hydraulic source returns to the tank via a hydraulic actuator bypass circuit including a gap space.   6. The fluid control apparatus according to claim 5, wherein the maximum clearance of the clearance space between the edge of the side wall of the through groove of the spool and the cylindrical inner peripheral surface of the sleeve is on the order of 0.1 mm.

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