JP2000028023A - Ball screw driven hydraulic control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with the discrimination between a lubricating oil for sliding a ball screw and a working fluid for hydraulic operation, to reduce the number of parts, and to simplify the structure by arranging a ball screw slide part of a hydraulic control valve to be suitably used in a hydraulic circuit of an ejection device of an ejection molding machine in a hydraulic control part. SOLUTION: An output shaft of a servo motor 210 in a drive motor part 200 is connected to a ball screw shaft 350 to constitute a ball screw slide part in a hydraulic control part 300 through a coupling 230. In the hydraulic control part 300, valve chests 320 (320a-320c) are formed in a cylindrical valve casing 310, and an approximately cylindrical spool 330 is fitted therein. The spool 330 is moved in the longitudinal direction by the rotation of the drive motor part 200 through the ball screw slide part, and the spool 330 is retracted to control the flow rate of the working fluid according to the clearance formed between a projection part P of the valve casing 310 and an outer circumferential part Q of the spool.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric pressure control valve and an electric flow control valve used for pressure control and flow control of hydraulic oil used in a hydraulic circuit of an injection device of a die casting machine and an injection molding machine.

[0002]

2. Description of the Related Art In a hydraulic circuit of an injection device of a die casting machine or an injection molding machine, a high-response, high-accuracy, large-capacity pressure control valve and a flow control valve are indispensable. For this reason, a spool type hydraulic control valve using a servo motor or a pulse motor excellent in response speed and position control performance and a ball screw mechanism with little hysteresis is frequently used. For example, Japanese Patent Application No. 8-222844, Japanese Patent Application No.
There is a hydraulic control valve described in -98180.

In Japanese Patent Application No. 8-222844, as shown in FIG. 4, the ball screw sliding portion and the hydraulic control portion are arranged in tandem, and the ball screw sliding portion has a hermetic structure. Not. Therefore, foreign matter such as dust floating in the air enters the sliding portion and causes wear and abrasion, thereby shortening the life of the ball screw sliding portion. Further, it is necessary to apply grease or periodically spray lubricating oil to a sliding portion between the ball screw shaft and the ball screw nut. Therefore, regular maintenance is indispensable, and the lubrication state of the sliding portion is not perfect. In addition, the control valve itself has become large, and there has been a demand for a compact control valve from the viewpoint of piping design.

On the other hand, the one described in Japanese Patent Application No. 8-98180 as a conventional example has the ball screw sliding portion sealed in a casing as shown in FIG.
Oil bath lubrication. For this reason, the reliability of the lubrication of the sliding portion is significantly improved as compared with Japanese Patent Application No. 8-222844. However, because of the oil bath system in which the lubricating oil does not circulate, the abrasion powder generated in the sliding portion accumulates without being removed. Further, since the lubricating oil itself is in a closed state, the cooling is not sufficient, and the oil deteriorates quickly and the life of the lubricating oil itself is shortened. Therefore, periodic replacement of the lubricating oil and purification of the sliding portion of the ball screw are required. In addition, the abrasion powder and the like become foreign matters, causing wear and abrasion of the ball screw sliding portion. Further, since the ball screw sliding portion and the hydraulic control portion are arranged in tandem and are housed in independent casings, respectively, the shaft through portion on the hydraulic control portion side of the casing for the ball screw sliding portion is lubricated. A seal mechanism to prevent oil leakage is required,
The structure became complicated and the length of the control valve itself became longer.

[0005]

As described above, the structure of the conventional ball screw drive hydraulic control valve is complicated, the length of the control valve itself is increased, and the lubrication state of the ball screw sliding portion is also ensured. Instead, it took time to replace the lubricating oil and clean the sliding part of the ball screw. An object of the present invention is to solve such a problem, and to provide a ball screw driven hydraulic control valve having a simple structure, a compact control valve itself, a good lubrication state, and maintenance-free.

[0006]

In order to solve the above problems, according to the present invention, in the first invention, a spool driven forward and backward by a combination of a servo motor or a pulse motor and a ball screw mechanism is provided. Hydraulic pressure control valve for controlling the fluid pressure or flow rate by the movement position of
A communication hole (valve chamber) for communicating a pair of ports formed in the outer periphery of the valve casing is formed in the valve casing, and the spool is inserted into the communication hole (valve chamber) formed in a cylindrical shape in the axial direction. At the forward limit position of the spool, a pair of ports are shut off by the spool, and at the retreat limit position of the spool, the pair of ports communicate with each other. The configuration is such that the valve opening is adjusted, and the ball screw sliding portion is disposed in the casing and can be lubricated with the fluid.
According to a second aspect, in the first aspect, the space including the ball screw sliding portion including the ball screw shaft and the ball screw nut is communicated with a low-pressure tank port or a drain port. Further, in the third invention, the first invention
In the invention, the nut of the ball screw sliding portion and the spool are directly connected.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1, 2 and 3
FIG. 1 is a longitudinal sectional view showing an embodiment of a hydraulic control valve according to an embodiment of the present invention, and FIG. 2 is a transverse sectional view taken along lines A to B in FIG. FIG. 3 is an embodiment of a hydraulic circuit incorporating the hydraulic control valve of FIG. 1, and FIGS. 4 and 5 are longitudinal sectional views of a conventional hydraulic control valve.

[0008] As shown in FIG.
It is roughly divided into a drive motor unit 200 located on one end side and a hydraulic control unit 300 including a ball screw sliding unit and configured. In the drive motor unit 200, a servomotor (or a pulse motor) 210 having a rotation amount detection device (not shown) is connected to a valve casing 31 via a frame 220.
0, and the valve casing 310 is fixed to a structure (manifold) of a mechanical device (not shown). The output shaft of the servo motor 210 is connected to one end of the ball screw shaft 350 via the coupling 230. The other end of the ball screw shaft 350 forms a ball screw sliding portion together with the ball screw nut.

[0009] As shown in FIG.
A valve chamber 320 (320a, 320b, 320c) formed of a communication hole formed in a cylindrical valve casing 310 is formed. In this valve chamber 320, a substantially cylindrical spool 330 having a groove on the outer periphery is slidably disposed. The spool 330 is integrally connected to the ball screw nut 340, and moves forward and backward in the valve chamber 320 in accordance with the rotation of the ball screw shaft 350.

That is, the ball screw shaft 350 that receives the rotational motion of the drive motor 210 via the coupling 230 is rotatably supported by the ball screw nut 340 via the bearing 240 and the spool 330. On the other hand, the spool 330 including the ball screw nut 340 is shown in FIG.
As shown in (A), two notches (grooves) 342 are formed in the outer peripheral portion in the axial direction, and a ball screw nut detent 341 is slidably fitted in these notches (grooves). Have been. Therefore, the ball screw nut can only perform reciprocating motion by the rotational motion of the ball screw shaft, and the rotational motion of the drive motor unit is converted into the forward and backward motion of the spool.

Further, since the ball screw shaft 350 penetrates the frame 220 serving as a closing plate on one end surface of the valve casing 310 on the drive motor side, it is necessary to take measures against leakage of hydraulic oil in the valve chamber 320c. . As shown in FIG. 1, an oil seal 361 was incorporated on the drive motor side of the bearing nut as a measure for sealing this portion. Valve room 320
When the pressure c is high, it is necessary to use a pressure-resistant seal structure such as U packing. In this embodiment, an oil seal type having a simple seal structure is used. That is, when a high oil pressure is applied to the inflow port R (when the spool is at the forward limit), the valve chamber 320c is isolated from the high pressure side by the spool 330, so that the high pressure is not applied. ing. When the spool 330 moves backward and the valve chamber 320c communicates with the inlet R,
Since the oil pressure in this portion acts only on the discharge resistance of the working oil, the oil seal structure can sufficiently fulfill the sealing function.

Next, the relationship between the movement of the spool 330 and the control of the hydraulic oil flow will be described. At the forward limit position of the spool 330 (the lower half in FIG. 1), the hydraulic oil that has entered through the inlet R is blocked by the spool 330 and the flow path is blocked. On the other hand, at the retreat limit position (the upper half in FIG. 1), the inflow port R and the discharge port T are communicated, and the hydraulic oil is discharged outside the control valve. In this manner, the flow rate of the hydraulic oil is controlled by the amount of the gap formed by the protrusion P of the valve casing and the outer peripheral portion Q of the spool due to the backward movement of the spool 330. That is, when the retreat amount of the spool 330 is reduced, the hydraulic oil flow rate decreases, and when the retreat amount is increased, the hydraulic oil flow rate increases,
In addition, since the spool retreat amount and the valve opening have a certain relationship, the flow rate of the hydraulic oil can be arbitrarily controlled.

Further, the pressure can be controlled instead of the flow rate. That is, if the gap amount is reduced, the flow rate is reduced, the throttle effect is increased, the pressure loss in this portion is increased, and the pressure on the inlet R side can be kept high. . Controlling the flow rate in this way also controls the pressure. The reason why the center of the spool 330 is the cavity 321 (through hole in the spool) is to prevent the hydraulic oil in the portion 320a from being closed in response to the movement of the spool. That is, the valve chamber 320a and the discharge port T communicate with each other through the through hole 321 in the spool. The same applies to the hydraulic fluid in the portion 320c. That is, the notch (groove) 342
The valve chamber 320c and the discharge port T communicate with each other via the communication groove 331. In this way, since the resistance of the hydraulic oil due to the movement of the spool is small, high-speed movement of the spool can be achieved.

Next, lubrication of the sliding portion of the ball screw, which is an important item of the present invention, will be described. Since the ball screw sliding portion is disposed in the valve chamber 320, it is always immersed in hydraulic oil. That is, when the spool is near the forward limit, the inflow port R is isolated from the outflow port T by the spool 330. In this case, the hydraulic oil in the valve chamber 320c communicates with the tank port or the drain port, and the ball screw sliding portion is immersed in the hydraulic oil. Next, the spool 330 retreats, and near the retreat limit, the inflow port R and the outflow port T are in a communicating state. In this state, as shown in FIG. 2 (B), the valve chamber 3 is connected through a communication groove 331 formed in the outer periphery of the spool.
Since 20c communicates with the outlet T, the working oil lubricating the sliding portion of the ball screw circulates.

In this manner, the sliding portion of the ball screw provided in the valve chamber 320 is lubricated with the operating oil, and the operating oil lubricating the sliding portion is returned to the tank (not shown) through the discharge port T. . A filtering device such as a wire mesh is installed at the return port to the tank, and the abrasion powder generated at the sliding portion of the ball screw is automatically removed. As a result, lubrication of the maintenance-free ball screw sliding portion becomes possible. It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

As described above, according to the present invention,
Since the ball screw sliding portion is disposed in the hydraulic control portion, that is, in the valve casing, it is not necessary to distinguish between the ball screw sliding lubricating oil and the hydraulic operating oil. Further, by connecting and integrating the ball screw nut and the spool, the number of parts is reduced and the structure is simplified, and the length of the control valve itself can be greatly reduced. In addition, since the operating oil circulates in the lubricating state of the sliding part, there is no accumulation of wear powder, the oil temperature is controlled, and there is no need to change the lubricating oil. A control valve is obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a ball screw driven hydraulic control valve according to an embodiment of the present invention. The upper half of the drawing shows the state where the spool is at the retreat limit position, and the lower half shows the state where the spool is at the forward limit position.

FIG. 2 is a cross-sectional view taken along A- and B- in FIG.

FIG. 3 is an embodiment of a hydraulic circuit incorporating a hydraulic control valve according to an embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a conventional hydraulic control valve.

FIG. 5 is a longitudinal sectional view of a conventional hydraulic control valve.

[Explanation of symbols]

 Reference Signs List 100 Hydraulic control valve 200 Drive motor unit 210 Servo motor (or pulse motor) 220 Frame 230 Coupling 240 Bearing 241 Bearing nut 300 Hydraulic control unit 310 Valve casing 320 (320a, 320b, 320c) Valve chamber 321 Spool through hole 330 Spool 331 Communication groove 340 Ball screw nut 341 Ball screw nut detent 342 Notch (groove) 350 Ball screw shaft 360 Bearing retainer 361 Oil seal P Projection of valve casing Q Spool outer periphery R Inlet S Through hole T Outlet

Claims (3)

[Claims] 1. A hydraulic control valve for controlling a fluid pressure or a flow rate according to a moving position of a spool driven forward and backward by a combination of a servo motor or a pulse motor and a ball screw mechanism, and is provided on an outer periphery of a valve casing. A communication hole (valve chamber) for communicating the pair of ports is formed in the valve casing, and the spool is slidably moved forward and backward in the communication hole (valve chamber) formed in a cylindrical shape in the axial direction. At the same time, the pair of ports are blocked by the spool at the forward limit position of the spool, the pair of ports are communicated at the retract position of the spool, and the valve opening is adjusted according to the retreat amount of the spool. A ball screw driven hydraulic control valve, wherein the ball screw sliding portion is disposed in the casing and lubricated by the fluid. 2. The ball screw driven hydraulic control valve according to claim 1, wherein a space including said ball screw sliding portion comprising a ball screw shaft and a ball screw nut communicates with a low pressure tank port or a drain port. 3. The ball screw driven hydraulic control valve according to claim 1, wherein the nut of the ball screw sliding portion is directly connected to the spool.