JP4138352B2 - Spool selector valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a large-capacity spool switching valve used in a machine having a plurality of actuators such as a construction machine such as a hydraulic excavator, and particularly relates to improvement in reliability thereof.
[0002]
[Prior art]
Hereinafter, conventional techniques will be described with reference to the drawings. FIG. 3 is a view schematically showing a cross section on one end side of the spool switching valve according to the prior art. In the figure, 1 is a housing, 2 is a spool, 3 is a tank line, and 6B is a cylinder port. In a spool switching valve applied to a hydraulic excavator or the like, for example, when the boom of the hydraulic excavator is lowered, the lowering speed of the boom depends on the opening degree of the passage communicating from the return side cylinder port 6B to the tank line 3 from the boom. Some are configured to be controlled. In such a switching valve, a notch portion 5-1 having a relatively large opening area and a notch portion 5-2 having a relatively small opening area are provided adjacent to the shoulder portion of the large diameter portion of the spool. As the spool moves, the notch portion 5-2 having a small opening area is first opened to the tank line 3 and then the notch portion 5-1 having a large opening area is opened, that is, the cylinder port 6B is sequentially increased as the spool moves. To the tank line 3 is configured to be large.
[0003]
However, when working with an actual hydraulic excavator, because of the matching in performance between the size of the hydraulic excavator and the switching valve that switches the operation, only the notch with a small opening area is spooled near the fully opened position. It is very often used in a state where the is moved.
[0004]
In such a case, when the boom descends, the pressure oil discharged from the cylinder port to the tank line through the notch 5-2 having a small opening area becomes a high-speed jet and collides with the wall of the housing. Become. Moreover, since this jet flow is suddenly released from the relatively high pressure cylinder port 6B to the tank line 3 having a low pressure of almost the back pressure (nearly 0), the energy of the pressure oil is very large. Become. Therefore, the hydraulic oil collides with the wall portion of the housing 1 at a high speed and with a large force. Such a state of fluid energy is schematically shown in FIG. By passing through the notch 5-2, the speed rapidly decreases, but in contrast, the kinetic energy increases and has a magnitude of h1. This energy of h1 causes erosion of the wall portion of the housing 1.
[0005]
Since the housing 1 is generally composed of a tough cast iron material, it is difficult to increase its hardness by heat treatment or the like. Therefore, when this switching valve is used for a long time, the wall portion is eroded by the jet, and in the worst case, the erosion may even penetrate to the outer surface of the housing 1. Moreover, it has been found that the degree of erosion of the housing 1 is more remarkable as the hydraulic excavator on which the switching valve is mounted is larger.
[0006]
[Problems to be solved by the invention]
An object of the present invention is a highly reliable switching valve that has excellent operability and can suppress erosion of component parts due to fluid force even when used under conditions that require switching of a large capacity such as a large construction machine. Is to provide.
[0007]
[Means for Solving the Problems]
The spool switching valve according to the present invention includes a housing having a plurality of oil chambers including a pump line, a cylinder port, and a tank line, and is slidably liquid-tightly inserted into the housing to supply oil to the plurality of oil chambers. A spool having a large-diameter portion and a small-diameter portion for switching supply, and an auxiliary oil chamber provided between the cylinder port of the housing and the tank line, and the auxiliary oil chamber is connected to the cylinder port. And the opening area between the tank line and the tank line are configured to be variable according to the movement of the spool , and pressure oil is supplied from the cylinder port to the auxiliary oil chamber and from the auxiliary oil chamber to the tank line. As the pressure flows, the cylinder port pressure is successively reduced and discharged to the tank line.
[0008]
In the spool switching valve configured as described above, the discharge flow rate to the tank line when the spool moves to a position where only the small notch of the conventional valve is fully opened to the tank port, and the cylinder when the spool moves to the same position When the flow rate from the port to the auxiliary oil chamber and from the auxiliary oil chamber to the tank line is set to be almost the same, the speed control characteristics of the actuator are not different from conventional ones, and the pressure oil discharged to the tank line is is not such collide at high pressure in the wall of the housing sufficiently has a pressure drop, when it is discharged into the tank line while passing port from the auxiliary oil chamber, and from the auxiliary oil chamber to the tank line.
[0009]
The spool switching valve of the present invention is
Between the cylinder port and the auxiliary oil chamber,
And between auxiliary oil chamber and tank line,
The sequential pressure reduction means
Notches that change the opening area between the oil chambers according to the movement of the spool are provided on the shoulder of the large-diameter portion of the spool, these notches are arranged in series, and the pressure oil from the cylinder port is notched. It can comprise so that a part may be passed.
[0010]
Furthermore, the spool switching valve of the present invention is
This notch can be arranged so that the resultant force of the reaction force of the fluid force when the fluid passes through the notch becomes zero.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 is a cross-sectional view of a spool switching valve according to an embodiment of the present invention. In the drawing, 1 is a housing, 2 is a spool, 3 and 13 are tank lines, 33 is an auxiliary oil chamber, 4 is a pump line, 2A, 2B, 2C, 2D and 2H are large diameter portions of the spool 2, 2E, 2F and 2G. , 2J are small diameter portions of the spool 2, and 6 is a cylinder port. Both ends of the spool 2 are housed in caps 14A and 14B, and oil chambers 8A and 8B are formed between both ends of the spool 2 and the caps 14A and 14B. Pilot pressure oil from a pilot valve (not shown) is supplied to the oil chambers 8A and 8B via the ports 10A and 10B. A spring 9 for returning the spool 2 to neutral is provided in the oil chamber 8A. A variable displacement pump 7 is connected to the pump line 4, and each port of the actuator 15 is connected to the cylinder ports 6A and 6B. FIG. 1 illustrates a neutral state of the spool, and the pressure oil from the variable displacement pump 7 is discharged from the pump line 4 to the tank through the small diameter portions 2E and 2F of the spool 2 and the tank lines 13A and 13B. .
[0013]
Notches 5-1 and 5-2 are provided on the shoulder of the large-diameter portion 2D of the spool 2 on the small-diameter portion 2J side. Further, notches 5-3 and 5-4 are provided on the shoulder of the large-diameter portion 2H of the spool 2 on the small-diameter portion 2G side. As for the position and size of each notch, when the spool 2 moves to the right in FIG. 1, the notch 5-2 first opens into the tank line 3, and then the notch 5-4 assists. When the spool 2 opens to the oil chamber 33 and further moves to the right, the notch portion 5-2 opens to the tank line 3, and then the notch portion 5-3 opens to the auxiliary oil chamber 33. ing. In FIG. 2, the spool 2 moves to the right in the figure, the notch 5-2 opens to the tank line 3, and the notch 5-4 opens to the auxiliary oil chamber 33. 5-1 shows a state where the tank line 3 has not been opened yet, and the notch 5-3 is not opened to the auxiliary oil chamber 33.
[0014]
In such a configuration shown in FIG. 1, when a signal pressure from a pilot valve (not shown) is supplied to the oil chamber 8A and the spool 2 is moved to the position shown in FIG. The passage communicated with the tank line 13A via the portion 2E is blocked by the large diameter portion 2A of the spool 2, and further communicated with the tank line 13B from the pump line 4 via the small diameter portion 2F of the spool 2. Is blocked by the large-diameter portion 2B of the spool 2, so that the pressure oil from the variable displacement pump 7 is supplied to the actuator 15 through the passages 11 and 12A and the cylinder port 6A. Further, the return oil from the actuator 15 is discharged to the tank line 3 through the notches 5-3 and 5-4, the auxiliary oil chamber 33, and the notches 5-1 and 5-2.
[0015]
Here, the amount of pressure oil discharged to the tank line 3 through the notches 5-3 and 5-4, the auxiliary oil chamber 33, and the notches 5-1 and 5-2 is the same as that of conventional switching. In the spool 2 of the valve and the switching valve according to the present invention, if the movement amount of the spool 2 is the same, the area of each notch is such that the amount of oil discharged from the cylinder port 6B to the tank line 3 is substantially the same. Is set. Accordingly, assuming that the actuator 15 is, for example, a boom cylinder of a hydraulic excavator and the boom is lowered, the lowering speed of the boom can be controlled in the same manner as in the conventional case. Further, in the conventional switching valve, the pressure oil discharged through the notch 5-2 having a small opening area is ejected as a high-speed jet due to a sudden pressure change. However, in the switching valve according to the present invention, the pressure gradually decreases while passing through the notches 5-3 and 5-4, the auxiliary oil chamber 33, and the notches 5-1 and 5-2. Therefore, the differential pressure between the pressurized oil and the tank line 3 at the time of being discharged from the notch 5-2 to the tank line 3 is considerably smaller than that of the conventional switching valve. As a result, fluid energy when colliding with the wall portion of the housing 1 is reduced, and erosion of the wall portion of the housing 1 can be suppressed. The material of the spool 2 is generally a steel material, and the hardness can be easily increased by heat treatment, so that the erosion inside the spool 2 can be easily suppressed.
[0016]
Here, the pressure energy of the fluid flowing out to the tank line 3 is schematically shown in FIG. In the switching valve according to the present invention, when the fluid passes through the notches 5-3 and 5-4 and flows into the trapping oil chamber 33, the pressure energy of the fluid is significantly reduced and the kinetic energy is increased instead. Further, in the flow path from the auxiliary oil chamber 33 to the flow into the cutout portion 5-1, the pressure energy and the kinetic energy reach the cutout portion 5-2 with almost no change. Then, when passing through the notch 5-2, the pressure energy is reduced to nearly “0 (zero)”, and the kinetic energy is slightly increased, but the magnitude thereof is h2. Is much smaller than h1. Therefore, in the switching valve according to the present invention, erosion of the wall portion of the housing 1 can be suppressed.
[0017]
Further, the radial direction component of the fluid force when passing through the notches 5-1, 5-2, 5-3, 5-4 through the notches 5-1, 5-2, 5-3, 5-4. If the force is provided at a position where the forces are balanced, the spool 2 is not bent by the fluid force, and the spool 2 is smoothly moved. Specifically, for example, the notch portions may be provided at two places where the passage 20 is provided at a symmetrical position with respect to the central axis of the spool 2. Furthermore, a notch may be provided at three places where the angle between the passages is 120 degrees, or may be provided at four places where the angle is 90 degrees.
[0018]
【The invention's effect】
As described above, in the spool switching valve, the auxiliary oil chamber is provided between the cylinder port and the tank line , and the respective openings between the cylinder port and the auxiliary oil chamber and between the auxiliary oil chamber and the tank line are provided. The area can be changed according to the movement of the spool , and the pressure oil is passed from the cylinder port to the auxiliary oil chamber and from the auxiliary oil chamber to the tank line, so that the pressure at the cylinder port is gradually reduced. can be discharged to the tank line, excellent operability, it is possible to obtain a highly reliable spool switching valve.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an embodiment of a spool switching valve according to the present invention.
FIG. 2 is a diagram showing details near the right end of the spool 2 in FIG. 1 and changes in fluid energy.
FIG. 3 is a schematic diagram showing changes in fluid energy in a conventional spool valve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Spool 3, 13 Tank line 5-1, 5-2, 5-3, 5-4 Notch part 4 Pump line 6 Cylinder port 7 Variable capacity pump 8 Oil chamber 11, 12 Passage 15 Actuator 33 Auxiliary oil chamber

Claims (3)

A housing having a plurality of oil chambers including a pump line, a cylinder port and a tank line;
A spool that is slidably liquid-tightly inserted into the housing and includes a large-diameter portion and a small-diameter portion that switch the supply of oil to the plurality of oil chambers;
An auxiliary oil chamber provided between the cylinder port of the housing and the tank line;
With
The auxiliary oil chamber is configured to be capable of changing an opening area between the cylinder port and the tank line in accordance with movement of the spool, from the cylinder port to the auxiliary oil chamber, and A spool switching valve characterized in that, as pressure oil flows from the auxiliary oil chamber to the tank line, the pressure of the cylinder port is successively reduced and discharged to the tank line. Between the auxiliary oil chamber and the cylinder port,
And the inter auxiliary oil chamber and the tank line,
The sequential pressure reduction means
Provided notch changing an opening area between the respective oil chambers in accordance with the movement of the spool shoulder portion of the large diameter portion of the spool, and place these notches in series, the hydraulic fluid from the cylinder port 2. The spool switching valve according to claim 1, wherein the spool switching valve is configured to pass through these notches. The notch is
When the notch is fluid passes, the spool switching valve according to claim 1 or 2, characterized in that the sum of the reaction force of the fluid force is disposed so as to be zero.

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