KR960010537B1 - Switching valve and its spool milling method - Google Patents

Abstract

None.

Description

Spool Processing Method of Switching Valve and Switching Valve

1 is a front view showing a spool impregnated in an embodiment of the present invention.

2 is a cross-sectional view of FIG.

3 is a circuit diagram showing a switching valve in the embodiment.

4 is a perspective view showing the shape of the notch in the spool of the embodiment.

5 is the same cross section.

6 is an elevation view.

7 to 12 show another embodiment of the present invention.

7 is a perspective view of the notch shape.

8 is a perspective view at the time of notch processing.

9 is a longitudinal sectional view of the spool during notch processing.

10 is a spool top view at the time of notch processing.

11 is a spool front view at the time of notch processing.

12 is an explanatory view of the flow force.

FIG. 13 shows another embodiment of the present invention and corresponds to FIG. 12. FIG.

14 is a circuit diagram showing a conventional switching valve.

15 is a front view showing a conventional spool.

16 is a front view showing another conventional spool.

* Explanation of symbols for main parts of the drawings

2: pump 3: tank

4,11 spool 4a, 12 land part

8,15: end mill 13a: start end

13b: first slope 13c: second slope

13d: termination 13e: notch bottom

14: switching part

The present invention relates to a switching valve and a spool processing method of the switching valve which is preferably used for cylinder driving and the like.

As a specific apparatus provided with the switching valve for cylinder drive, a forklift is mentioned, for example. Forklifts include various cylinders such as lift cylinders for lifting and lowering the pallet along the mast, tilt cylinders for changing the angle of the pallet by tilting the mast forward and backward, and reach cylinders that project the mast against the body. It is common to provide it, and a switching valve is correspondingly connected to each cylinder. As shown in the circuit diagram in FIG. 14, the switching valve communicates with a pair of operation ports A and B connected to both rooms 1a and 1b of the cylinder 1, and a high pressure source 2 such as a pump. The switch has a high pressure port P and a low pressure port T communicating with the tank 3, and performs a switching function of three positions in accordance with the slide position of the inner spool 4 as shown in FIG. Specifically, the two operation ports A and B are blocked at the sensor position of the spool 4 shown in FIG. 14, and the operation ports A or B are connected to the high pressure port P at the right or left position of the spool 4, respectively. At the same time, connect operating port B or A to low pressure port T. When the spool 4 blocks both operation ports A and B at the center position, the high pressure port P and the low pressure port T communicate with each other via the oil passage 5, and the high pressure pressurized liquid passes through the oil passage 5 with the tank. Return to (3). This flow path 5 is blocked in the right position and the left position of the spool 4. In addition, since the tilt cylinder and the rich cylinder are normally double acting, the switching valve may have the above-described configuration. However, since the lift cylinder is usually single-acting, the switching valve is closed by the appropriate means of the operation ports A or B.

By the way, it is common that each cylinder 1 of said forklift is connected to the pump 2 which is a common high pressure source, and is comprised so that it may operate using the discharge pressure liquid of this pump 2. In that case, the capacity | capacitance of the pump 2 and the electric motor which drives it is selected based on the lift cylinder which high speed and high power are calculated | required, and it is a thing with large output and a large capacity generally. In such a configuration, the equal pressure liquid is supplied from the pump at the time of driving to the tilt cylinder and the rich cylinder, which may be relatively low speed and low power, and an unfavorable situation arises in terms of operation and safety. In addition, increase the pipe resistance by thinning the pipe around the tilt cylinder or the rich cylinder, and when operating these cylinders, open the relief valve attached to the switching valve to return a small amount of liquid to the tank. Although it is conceivable to reduce the speed by sending it to the cylinder, in this case, the hydraulic pressure always rises to the relief pressure unnecessarily when the tilt cylinder or the reach cylinder is operated, which increases the current consumption of the motor and increases the life of the mounted battery. At the same time, the liquid temperature rises rapidly, causing inconvenience in the adverse effects in the circuit.

In view of the above facts, for example, those shown in Japanese Patent Application Laid-Open No. 60-54238, and the like, indicated by broken lines in Figs. 14 and 15, the right of the spool 4 to the switching valve. The bypass passage 6 is formed in which the high pressure port P and the low pressure port T communicate with each other via the throttle at the position and the left position. According to this, when driving the cylinder 1, such as a tilt cylinder or a lift cylinder, partial pressure liquid is returned to the tank 3 via the bypass passage 16, and the flow volume to each cylinder 1 can be restrict | limited. Therefore, the pump 2 can be operated at the pressure level according to the load of the cylinder 1, and it becomes possible to improve power efficiency significantly.

By the way, in the above-mentioned prior art, as shown in FIG. 15, the bypass passage 6 is realized by providing the bleed-off throttle 6a which opens on both sides of the land portion 4a of the spool 4. Doing. For this reason, when machining this bleed-off drawer 6a, a completely separate processing step is required after lathe processing, which increases the number of processing steps, and at the same time, the bleed-off throttle 6a has a throttle effect. Since it is easy to go, it comes with the inconvenience that it is extremely difficult to set a throttle amount to a precise value. In addition, as shown in FIG. 16, the bypass passage 6 is made smaller in diameter on the outer circumference of the land portion 4a of the spool 4 to form a slight gap 6b between the sleeve 7 and the sleeve 7. In this case, it is necessary to perform the polishing step of the spool 4 twice, and on the actual use thereof, the gap between the gaps 6b is generated. ), Fine clearance control in units of radius gap 1 / 1000mm is required, which not only increases the number of machining steps but also inevitably increases the cost in terms of dimensional accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and in general, a hydraulic circuit, a hydraulic device from a fixed-capacity hydraulic source by a switching operation of hydraulic pressure such as a forklift, a hydraulic machine, a construction machine, an industrial vehicle, a special vehicle, etc. It is an object of the present invention to provide a method for spooling of a switching valve and a switching valve that can supply a flow rate according to a load to the hydraulic circuit through a switching valve, and at the same time, it is possible to easily and precisely manufacture the hydraulic fluid. It is done.

The switching valve according to the present invention is characterized in that a notch is formed in the inner circumferential land portion of the spool to cross the land portion in the axial direction to achieve the above object.

In this case, as a notch processing method, the end mill is disposed at a position offset in a direction perpendicular to both shaft centers based on the center position of which the shaft core is orthogonal to the shaft center of the spool. The method of carrying out the relative conveyance operation | movement of an end mill along a axial center along a land part, and then carrying an end mill away from a spool becomes effective. Hereinafter, this processing method is called an end milling method.

The notch shape of the spool is formed in the land portion of the spool, and the start end portion is opened to the switching portion, and forms a cross-sectional V-shape in which the first slope and the second slope are opened therebetween, and the first slope is a surface up to the end portion. The second slope is coincident but is characterized in that the end portion is bent up toward the first slope.

The switching valve using a normal spool blocks the high and low pressure ports by the land portion at the rightward or leftward position of the spool, but the switching valve to which the spool of the present invention is applied is at the rightward or leftward position of the spool. The high and low pressure ports communicate with each other through the notches, and a predetermined flow rate of the pressurized liquid is bypassed from the high pressure port toward the low pressure port according to the throttle amount of the notch, and the remaining pressurized liquid is supplied to the load circuit. As a result, the pump can be operated at the pressure level according to the load, and the power efficiency can be improved significantly. In addition, when the bypass passage is formed by the notch passing through the land portion as in the present invention, it is possible to apply the end milling method, and the cross section is only required to scan the end mill along the land portion on the same shelf. The notches forming the triangular groove shape can be easily formed. As an advantage of the end milling method at that time, it is possible to freely control the cross sectional area of the notch simply by adjusting two independent parameters such as the offset position and the cutting amount of the end mill. The processing becomes very simple, and the precision can be improved without difficulty.

In the notch shape as described above, as the end portion of the notch cutting is curved toward the first slope of the second slope, the width thereof becomes smaller and the bottom becomes shallower. For this reason, when this spool is fitted to the sleeve, the opening area with the port can be increased very smoothly from the end of notch cutting toward the switching part.

In the notch processing method as described above, when the end mill is transported along the axial direction of the spool, the first slope is formed at the position where the tip end surface portion of the end mill passes, and the tip outer circumference of the end mill passes. The second slope is formed. For this reason, the first slope is coincided with the end portion, but since the end portion is determined by two independent elements of the offset position and the cutting amount of the end mill, the cross section area of the notch can be controlled freely by their combination. It is also possible to adjust the shape of the notch end portion separately from the cross sectional area of the notch. Since the end mill has a smaller radius than that of the milling cutter, the ejection angle at the notch end can be increased.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

This switching valve is for example applied to operate a cylinder of a forklift. Basically, as shown in FIG. 3, the said switching valve is connected to the pair of operation ports A and B connected to the both rooms 1a and 1b of the cylinder 1, and the pump 2 which is a high pressure source. It has the high pressure port P which communicates with, and the low pressure port T which communicates with the tank 3, and switches to 3 positions according to the slide position of the inner snow spool 4 as shown in FIG. That is, the two operation ports A and B are blocked at the center position of the spool 4, and the operation port A or B is connected to the high pressure port P at the right or left position thereof and the operation port B or A is connected to the low pressure port T. Connect. In the state of FIG. 3, in which the spool 4 is at the center position and blocks both operation ports A and B, the high pressure port P and the low pressure port T communicate with each other via the flow path 5, and pressurize the high pressure liquid to the flow path. It returns to tank 3 via (5).

In such a switching valve, the spool 4 shown in FIG. 1 and FIG. 2 forms the notch 6c which transverses this land part 4a in the axial direction in the outer peripheral land part 4a. As shown in FIG. 3, the notch 6c is used as the bypass passage 6 for communicating the high pressure port P and the low pressure port T via the flow path 5. As shown in Figs. 4 to 6, the processing procedure of this notch 6c is applied to both shafts m and n based on the center position where the shaft center n is orthogonal to the shaft center m of the spool. Exposed at a position offset in the vertical direction x, the relative transfer operation of the end mill 8 in the direction of the land portion 4a is performed along the axis center m of the spool 4 at a predetermined cutting amount d from the position, and then The end mill 8 is separated from the spool 4, and in this embodiment, the transfer operation is performed until the end mill 8 completely crosses the land portion 4a of the spool 4. I'm trying to. Thereby, as shown in FIG. 1, FIG. 2, and FIG. 6, the spool 4 is formed by engraving the triangular notch 6c which forms a cross-sectional V shape. In this embodiment, The same notch 6c is arrange | positioned at four conformal places of the land part 4a.

When such a spool 4 is applied to the switching valve of FIG. 3, the high pressure port P and the low pressure port T communicate with each other via the notch 6c at the right position or the left position of the spool 4, and the notch ( Along with the throttle amount of 6c), a predetermined flow rate of the pressurized liquid is bypassed from the high pressure port P toward the low pressure port T, and the remaining pressurized liquid is supplied to the cylinder 1. For this reason, the pump 2 can be operated at the pressure level according to load, and it becomes possible to improve power efficiency especially. In addition, when the notch 6c which transverses the land part 4a is formed using the end milling method like this embodiment, and the notch 6c is used as the bypass pass 6, Not only the machining on the same lathe is possible, but the end milling method also benefits, that is, by adjusting two independent parameters such as the offset position x and the cutting amount d of the end mill 8, the notches 6c. The advantage that the cross-sectional area of the material can be controlled freely is obtained. For this reason, the process for setting the bypass flow rate according to the load of the cylinder 1 becomes very simple, and the precision can also be improved without difficulty.

Next, another Example of this invention is described with reference to FIGS.

As shown in FIG. 7, the spool 11 which concerns on this Example has the notch 13 formed in the land part 2, and the start end part 13a opened to the switching part 14. As shown in FIG. The notch 13 forms a cross-sectional V-shape opening between the first slope 13b and the second slope 13c, and the first slope 13b extends to the end portion 13d along the axial center m direction of the spool. As for the 2nd slope 13c which extends face-surfacely, the terminal part 13d is bent and curved to the 1st slope 13b.

In such a notched shape, the width between the second slope 13c and the first slope 13b becomes narrower as the closer to the end portion 13d along the cutting direction of the notch 13, and both slopes ( The notch bottom 13e formed in the position where 13b) and 13c intersected becomes shallow. Therefore, the opening area with the high pressure port P is gradually increased from the cutting end portion 13d toward the start end portion 13a, whereby the inching function almost equivalent to that of the V-shaped notch can be exhibited.

On the other hand, in this embodiment, in order to process such a notch, the milling function generally provided in the NC lathe is used, and as shown in FIGS. 8 and 9, the end mill 15 has an axis n. Based on the center position A orthogonal to the axis center m of the spool 11, it is disposed at the position B offset by the distance l in the direction perpendicular to the two axis centers m and n. And as shown in FIG. 9 from the position B, the cutting amount d with respect to the land part 12 of the spool 11 is hold | maintained, and it shows in FIGS. 10 and 11 along the axial center m of the spool 11 As described above, the end mill 15 is transferred in the land portion 12 direction (arrow Y direction). Thereafter, the end mill 15 is separated from the spool 11 (in the direction of arrow Z in FIG. 11), and the spool 11 is rotated 90 degrees, and then transferred to the processing of the next notch.

According to the notch processing method as described above, the first slope 13b is formed at the position where the tip surface 15a of the end mill 15 passes along with the transfer operation of the end mill 15, and the end mill 15 The second slope 13c is formed at the position where the tip outer periphery 15b passes. For this reason, although the 1st slope 13b is made to coincide with the termination part 13d, as for the 2nd slope 13c, as shown to FIG. 7 and FIG. 10, the termination part 13d has the end mill 15 It is curved toward the first slope 13b along the outer circumferential portion 15b of the c) and is scraped off. Further, since the shape of the notch 13 is determined by two independent elements of the offset position B and the cutting amount d of the end mill 15, it is possible to freely control the cross sectional area of the notch 13 by their combination. It is also possible to adjust the shape of the notch end portion 13d separately from the cross sectional area of the notch 13. As shown in FIG. 12, the longitudinal cross section of the notch 13 is cut along the radius of the end mill 15, which is much smaller than that of the mill cutter. For this reason, the ejection angle of a fluid is large compared with the past, Therefore, the flow force F represented by the cosine of an ejection angle becomes small, and it becomes possible to improve control precision and stability.

Although the other embodiments of the present invention have been described above, various notch shapes can be realized by changing the offset position and the cutting amount. In addition, by using the present invention, when notching is performed several times by changing the offset position or the cutting amount for one notch, it is possible to realize a notch shape accompanied by a stepped cross-sectional area change, which is effective for applications requiring subtle cross-sectional area changes. . In addition, the end mill may be fixed, and the spool may be moved to be processed. In addition, in the above embodiment, when the offset amount of the end mill 15 is made small, as shown in FIG. 13, it may be processed so that the ejection angle is 90 degrees or more, and the flow force may be completely canceled. do. In addition, various modifications are possible in the range which does not deviate from the meaning of this invention.

As described above, the switching valve according to the present invention is preferably applicable to cylinder driving or the like by forming the notch passing through the land portion on the spool. In addition, also in the shape of the notch and the processing method thereof, it is possible to process simply and with high precision by using the end milling method or the like. In other words, as a post-processing of the spool, only one machining step is basically performed on one notch on the same machine, and a notch having a function equivalent to that of a notch manufactured through a conventional multi-process operation can be made extremely simple. . In addition, since the cross sectional area of the notch and the shape of the end portion can be easily controlled, the degree of freedom in design is improved, and the reproducibility in manufacturing the notch of the same characteristic is also improved. For this reason, the above-mentioned switching valve is applied to a hydraulic fluid, a hydraulic machine, a construction vehicle, an industrial vehicle, a special vehicle, etc., in the case where it is desired to supply hydraulic fluid to a hydraulic circuit, a hydraulic device, etc., from a fixed capacity hydraulic source generally. This is very useful.

Claims (4)

A spool comprising a land portion fitted to the inner circumference of the sleeve and a switching portion formed between the valleys of the land portion, and moving the spool in the axial direction to change its relative position with the sleeve, whereby the switching portion is selectively formed on the sleeve side. A switching valve for opening a port and switching flow paths, the switching valve having a notch for transversely passing the land portion in the axial direction. The end mill is disposed at a position offset in the direction perpendicular to both shaft centers with respect to the center position of which the shaft center is orthogonal to the shaft center of the spool, and ends in the land portion direction along the shaft center of the spool at a predetermined cutting amount from the position. And a notch for transversely passing the land portion in the axial direction to the land portion by carrying out a relative transfer operation of the mill and then transferring the end mill from the spool. A spool comprising a land portion fitted to the inner circumference of the sleeve and a switching portion formed between the valleys of the land portion, and moving the spool in the axial direction to change its relative position with the sleeve, whereby the switching portion is selectively formed on the sleeve side. In the switching valve for opening the port and switching the flow path, the spool has a cross-sectional V-shape which opens the start end of the land portion of the spool, and opens between the first slope and the second slope, and the first slope The switching valve, characterized in that the surface is identical to the end of the silver, but the second slope formed a notch having a shape in which the end is curved by the first slope. The end mill is disposed at a position offset in the direction perpendicular to both shaft centers with respect to the center position of which the shaft center is orthogonal to the shaft center of the spool. By carrying out a relative conveyance operation, thereafter, the end mill is separated from the spool, thereby opening a four-sided end portion of the end portion of the spool to the switching portion, and opening a cross-sectional V-shaped opening between the first and second slopes. The first slope is coincident with the end of the first slope, but the second slope processes the notch having a shape in which the end portion is bent and raised on the first slope.