JPS6127605B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic servo valve, and more particularly to a servo valve that uses an oil-in-water type hydraulic fluid consisting mainly of water and mixed with oil.

Hydraulic servo valves require extremely high precision machining, and cannot fully demonstrate their functions unless they maintain precision on the micron order. Therefore, conventionally, mineral oil, which has good lubricity and low anti-wear properties, has been used as the hydraulic oil. However, the use of hydraulic servo valves is increasingly becoming necessary in environments where there is a risk of fire, and in such cases conventionally very expensive synthetic hydraulic fluids have been used. Although this type of fire-resistant synthetic hydraulic oil has good lubricity and wear resistance, it is extremely expensive, has an adverse physiological effect on the human body, and is extremely troublesome to maintain. It had a major drawback.

For this reason, the use of oil-in-water (soluble oil, 5-10% oil in water), which is also fire-resistant, was considered, but since it is mainly water, it suffers from poor lubrication, severe cavitation, and Due to erosion caused by water droplets, the right angle land, which is the lifeblood of the servo valve, becomes rounded, resulting in a problem in which the pressure gain decreases and the valve becomes unusable in a very short period of time.

An object of the present invention is to provide a hydraulic servo valve that can stably perform its function as a servo valve for a long period of time even when inexpensive submerged oil is used as the hydraulic oil.

The present inventors conducted various experiments in order to investigate the reason why conventional servo valves could not withstand use in oil-in-water. As a result, it was discovered that there was a problem with the materials used for the spool and sleeve. In other words, conventional spools and sleeves have been made of high-hardness metals, such as gauge steel and bearing steel. It was discovered that the part that controls the flow of water (the part that controls the flow of water) becomes rounded and quickly becomes unusable. This is particularly important for sleeves that cannot be easily shaped by polishing the outer periphery or easily replaced like spools.

Additionally, experiments have revealed that ceramics such as TiC or WC are resistant to erosion.

The present invention was made based on the above considerations, and the sleeve is divided into a plurality of parts in a direction perpendicular to the axis of the spool, and the divided part having a metering edge at the end contains carbide. The adjoining divided portion adjacent to the divided portion formed of ceramic and having the metering edge is formed of a high hardness material other than the ceramic, and the spool is formed of ceramic containing carbide to achieve the above object. It is something.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

Although FIG. 1 shows an example of a three-way servo valve, in particular a configuration in which the spool is directly driven by a force motor, the present invention is not necessarily limited to this, and a servo valve using any driving method may be used. .

In FIG. 1, a spool 1 is held at its outer periphery by a sleeve 2 so as to be slidable in the axial direction, and the sleeve 2 is surrounded by a body 3 at its outer periphery. A force motor 4 is connected to one end of the spool 1, and the spool 1 is directly driven by the force motor 4.
Reference numeral 5 indicates a coil of the force motor 4. The axis of the force motor 4 is extended, and a speedometer 6 is provided at the end thereof for damping the spool 1.
is provided. Further, reference numeral 7 indicates a magnet, and this magnet 7 is held between a flange 9 of the drive section and a yoke 8 for forming a magnetic path. An adjuster 10 for adjusting the neutral point of the spool 1 is provided at the center of the yoke 8, and an end of the adjuster 10 is connected to an elastic body 11.
is pressed against the force motor 4 via.

A displacement meter core 12 for monitoring the movement of the spool 1 is provided at the other end of the spool 1, and a detection winding 1 is provided on the outer periphery of the core 12.
3 are arranged.

In addition, the code|symbol 14 in a figure shows a pump port, 15 is a load port, and 16 is a tank port, respectively.

FIG. 2 illustrates the lands of the spool 1 and sleeve 2 in the above embodiment.

Metering edge 1 with two l in Figure 2
It is the land length of the spool 1 between A and 1B, and L is the land length of the sleeve 2 between the two metering edges 2A and 2B. The distances between l and L are required to be maintained with extremely high accuracy, and the metering edges 1A, 1B, 2A,
2B is required to always maintain a right angle without being rounded.

Therefore, as shown in FIG.
A sleeve central portion 20 having both ends of the metering edges 2A and 2B, and a port 21 on the outside thereof.
22, and a sleeve outer end 24, forming both outer ends of the sleeve 2.
The central part 20 of the sleeve is made of ceramic such as TiC or WC. Here, the sleeve central portion 20 is cylindrical and only has an oil hole 25 formed therein, so that it has a simple shape and is easy to mold.

The sleeve intermediate portions 23, 23 and the sleeve outer end portions 24, 24 have a bucket structure and are complicated in structure, but it is not difficult to mold them if they are made of ordinary high hardness metal.

The spool 1 has a simpler shape than the sleeve 2, and its outer surface can be cut and polished, so it can be entirely made of ceramic.

According to this embodiment, even in cases where maintenance is difficult and severe usage conditions are required, such as a hydraulic servo valve for a rolling mill, almost no maintenance is required, and the hydraulic servo valve for the rolling mill has excellent environmental resistance. Suitable for valves.

Further, it is desirable that the spool 1 of the above-mentioned direct acting type hydraulic servo valve is lightweight, but in that case, the spool 1 may be made of TiC ceramic.

In addition, in the above embodiment, the sleeve intermediate portion 23,
23 and the sleeve outer end portions 24, 24 are made separate bodies, but there is no need to limit it to this, and these may be constructed integrally.

4 and 5 show other embodiments of the invention,
This embodiment shows the case of a four-way servo valve. A four-way servo valve has a structure as shown in FIG.

Pressure oil from the source pressure port Ps is sent to the control ports C ₁ and C ₂ and returned to the T port.

Here, if you can move spool 1 to the right in the diagram, Ps
→ Pressure oil flows to C ₂ and is returned from C ₁ to T port. When spool 1 is moved to the left, pressure oil flows from Ps to C ₁ and is returned from C ₂ to T port.

The dimensions that require high precision in this 4-way servo valve are the lengths of L ₁ , L ₂ , and L ₃ in sleeve 2;
Spool 1 has lengths l ₁ , l ₂ , and l ₃ , and it is important to finish these accurately.

Therefore, in slube 2, the parts that require highly accurate squareness are the metering edges 2A, 2B, 2C, and 2D, and it is strictly required to protect these parts from wear and maintain the squareness. Ru.

Therefore, as shown in FIG. 5, the sleeve 2 has a central portion 30 having the metering edges 2B, 2C at both ends, side portions 31, 31 having the metering edges 2A, 2D, and the central portion 30 and the sides. Part 3
1 and 31, and is divided into an intermediate part 32, 32 having ports C ₁ and C ₂ , and an outer end part 33, 33, and the central part 30 and the side parts 31, 31 are all
It is made of TiC or WC ceramic.
The other intermediate portions 32, 32 and outer end portions 33, 33 have complicated structures and are therefore made of ordinary metal materials.

As described above, according to the present invention, since the part having the metering edge part is made of ceramic containing carbide, the edge hardly becomes round even when used against a large flow of erosion like soluble oil. It has the excellent effect of being able to be used stably for a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the entire embodiment of the hydraulic servo valve according to the present invention, Fig. 2 is an enlarged sectional view showing the fitted state of the spool and sleeve, and Fig. 3 shows the structure of the sleeve. 4 is an enlarged sectional view showing a fitted state of a spool and a sleeve according to another embodiment of the present invention, and FIG. 5 is a sectional view showing the structure of the sleeve. Explanation of symbols: 1...Spool, 2...Sleeve, 2A, 2B, 2C, 2D...Sleeve metering edge.

Claims (1)

[Claims] 1. A hydraulic servo valve comprising a spool and a sleeve movably supporting the spool in the axial direction, and using underwater oil as hydraulic fluid, the sleeve being divided into a plurality of pieces in a direction perpendicular to the axis of the spool, The divided portion having the metering edge at its end is formed of ceramic containing carbide, and the side adjacent divided portion adjacent to the divided portion having the metering edge is formed of a high hardness material other than the ceramic. Also, a hydraulic servo valve characterized in that the spool is formed of ceramic containing carbide.