JPS6383471A - Pressure valve for hydraulic system - Google Patents

Abstract

PURPOSE:To automatically change a set pressure of valve opening operation with a temperature change of a working liquid by increasing a set pressure when the temperature of the working liquid is low and decreasing a set pressure when the temperature is low by the shape memory action of a spring made of a shape memory alloy. CONSTITUTION:A spring 4 made of a shape memory alloy is disposed between the upper surface of a valve element 3 and a boss portion 1e and a compression coiled spring 6 made of a general spring material is disposed between the lower surface of the valve element 3 and a receiving seat provided on the lower end side of a mandrel 2 in such a manner as to surround the mandrel 2. If the temperature of a working liquid is low, the valve element 3 receives strong pushing-up force of the general spring 6, and if the temperature of the working liquid becomes higher, the spring 4 made of a shape memory alloy pushes down the valve element 3 against the general spring 6.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) The present invention relates to a pressure valve used as a bypass valve for hydraulic fluid in various hydraulic systems such as hydraulic press machines and construction machinery. Regarding.

(Prior art) In general, the above-mentioned hydraulic pressure system pumps hydraulic fluid and operates cylinders etc. using the hydraulic pressure to perform various tasks, so foreign matter such as sludge gradually gets mixed into the hydraulic fluid. I started coming here. Therefore, if the contaminated liquid containing foreign matter is sent into the cylinder etc., it may cause wear and breakdown, so normally a filter (i!1 filter) is installed in the middle of the liquid supply path to remove the foreign matter. ing. Furthermore, in a hydraulic system equipped with such a filter, if abnormal pressure is applied for some reason, the filter will be damaged or soaked, so in order to protect the filter, a bypass valve that is compatible with differential pressure, which is a type of pressure valve, is installed. When the differential pressure between the upstream side and the downstream side of the filter, that is, the pressure loss, exceeds a certain set value, the bypass valve opens and the hydraulic fluid bypasses the filter instead of passing through the filter.

(Problem to be solved by the invention) By the way, in the Koshida hydraulic system, there is a large difference in the liquid temperature between the time of startup and the subsequent stable operation, and at the time of startup, fi, the temperature is equal to the atmospheric temperature. The temperature is about 20℃ or less (room temperature), and during stable operation it is 50℃ or less, although it varies depending on the system.
It is often about ~120°C. This temperature difference generally causes a large change in the viscosity of the hydraulic fluid (particularly hydraulic oil) used in the hydraulic system, and this change in viscosity has a large impact on the pressure drop in the hydraulic system, hindering system operation. There is a problem that causes That is, the viscosity of the hydraulic fluid is high in a low temperature state at the time of startup, and the pressure drop resistance to the filter is correspondingly large, but the viscosity is low and the pressure drop resistance to the filter is low in a high temperature state during stable operation. On the other hand, the bypass valve has a set pressure so that it opens to protect the filter when abnormal pressure occurs due to some cause such as equipment failure during stable operation of the hydraulic system. For this reason, in the low-temperature condition at the time of startup mentioned above, the viscosity of the hydraulic fluid is high and the pressure drop resistance is large, so the set pressure of the bypass valve is exceeded, and as a result, the bypass valve is closed even though there is no abnormality in the hydraulic system. There was a problem in that when the valve opened, contaminated liquid would flow directly into the cylinder, etc., which would interfere with the operation of the hydraulic system.

The present invention was developed in view of the above circumstances, and although it has a very simple configuration, the set pressure for opening the valve automatically changes as the temperature of the hydraulic fluid changes. It is an object of the present invention to provide a pressure valve that has a high set pressure and a low set pressure at high temperatures with low viscosity, making it very convenient to apply to the bypass valve of the above-mentioned hydraulic system.

[Structure of the Invention] (Means and Effects for Solving the Problem) In order to achieve the above object, the pressure valve for a hydraulic system of the present invention includes a unidirectional or bidirectional shape memory alloy for the valve body. A spring made of a shape memory alloy or a combination of a spring made of one of the above shape memory alloys and a normal spring is provided, and the set pressure at which the valve body opens due to the shape memory action of the spring made of the shape memory alloy is set when the hydraulic fluid is at a low temperature. The structure is such that the hydraulic fluid automatically fluctuates to a low level when the temperature is high, and the hydraulic pressure is maintained not only during stable operation when the hydraulic fluid is high temperature, low viscosity, and low pressure drop, but also during startup when the hydraulic fluid is low temperature, high viscosity, and high pressure drop. The valve body does not open as long as the system is operating normally, and only when abnormal pressure occurs in the hydraulic system for some reason, the valve body opens to bypass the flow of hydraulic fluid. It is what it is.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

First of all, the power valve shown here is configured as a bypass valve for the purpose of protecting the filter in the middle of the fluid supply path of the hydraulic system (not shown), and 1 in the diagram is made of metal or reinforced plastic such as FRP. This cylindrical frame 1 has an inlet port 1a at the upper end and an outflow row b at the lower end, and the lower surface around the lower end outflow row b is a valve seat 1C. Further, a screw 1d is formed on the outer periphery, and it is fixed by screwing it into piping or a special case, and the inlet port 1a on the upper end side is connected to the filter upstream side of the liquid supply path, and the lower end outflow row b is connected to the bypass path. It is configured to be installed so that it communicates with the

A boss portion 1e is integrally provided at the center of the upper end of the frame 1 in the form of a three-sided horizontal structure, and the upper end portion is fitted into the boss portion 1e, so that eight rods 2 hang long downward from the center of the frame. Installed in condition.

A valve body 3 is slidably fitted into the eight rods 2, so that it can be moved toward and away from the valve seat 1C at the lower end of the frame 1, and between the upper surface of the valve body 3 and the boss portion 1e. A shape memory alloy spring 4 (described later) is placed between the lower surface of the valve body 4 and a seat 5 provided on the lower end side of the 8 rods 2, and a compression coil spring 6 made of a normal spring material is attached to each of the 8 rods 2. It is set up so as to surround it. The height of the catch seat 5 can be adjusted using a drop-preventing nut 7 screwed onto the threaded portion of the lower end of the 8-rod 2, or it can be positioned using a split pin (not shown) that passes through the 8-rod 2 in the diametrical direction. has been done.

Here, the shape memory alloy spring 4 is made of T1Ni alloy or C
It is an irreversible unidirectional product that has been molded and memory-treated into the shape of a compression coil spring using uZn alloy, etc., and when heated from a low temperature to a high temperature, it self-cuts from the close contact state shown in Figure 1.)
Accordingly, it is set to extend at equal pitch intervals as shown in FIG. In other words, at high temperatures (for example, 60° C.) it becomes austenite and maintains its memorized shape, and at low temperatures (for example, 20° C.) it becomes martensite and easily deforms in response to external forces. This unidirectional shape memory alloy spring 4 faces a normal coil spring 6 with the valve body 3 in between to form a bias type bidirectional element. That is, the shape memory alloy spring 4 exerts a spring force that presses the valve body 3 downward (in the opening direction) due to its shape recovery force when the temperature is high, and when the temperature drops from that state, the force of the normal spring 6 (paisuka) It is easily crushed and deformed so as to contract into a close contact state, and has almost no spring force.

To describe the function of the pressure valve for a hydraulic system with the above-mentioned configuration, if the temperature of the hydraulic fluid at the time of startup operation of the hydraulic system is as low as about 20°C (at room temperature), the shape will change. The spring 4 made of memory alloy becomes martensite and deforms into a state where it is crushed as shown in Fig. 1 by the force of the normal spring 6 (Piaska), and has almost no spring force, and the valve receives hydraulic pressure. The body 3 receives the strong pushing force of the normal spring 6 only from this back pressure side. Next, from this state, the hydraulic system becomes stable and the temperature of the hydraulic fluid reaches 60°C.
When the temperature rises above ℃, the shape memory alloy spring 4 becomes austenite and tries to recover its shape, and the shape recovery force becomes a spring force that, together with the hydraulic pressure, pushes the valve body 3 down against the normal spring 6. It comes to work. In other words, the set pressure as a pressure valve (hydraulic pressure required for the valve body 3 to open) is high when the hydraulic fluid is low during startup operation due to transformation due to the shape memory action of the shape memory alloy spring 4. When the working fluid is at a high temperature during stable operation, it will fluctuate low and self-help.

Here, during normal stable operation when the hydraulic fluid of the hydraulic system is in a high temperature, low viscosity, and low pressure drop state, the hydraulic pressure applied to the valve body 3 and the spring force of the shape memory alloy spring 4 are combined with the normal force in the opposite direction. The force balance with the spring force of the spring 6 is calculated in advance, and the valve body 3 is
If the set pressure is set so that the valve is kept closed,
Shape memory alloy spring 4 when the hydraulic fluid is low during startup operation.
The set pressure becomes higher than during stable operation due to the weakening of the spring force, and even if the pressure drop resistance against the filter increases due to the high viscosity of the low-temperature hydraulic fluid and the fluid pressure increases,
This eliminates the inconvenience of the valve body 3 opening and bypassing the hydraulic fluid and sending contaminated fluid directly to the downstream side.Also, when the hydraulic fluid is at a high temperature during stable operation, the shape memory alloy spring The spring force becomes stronger due to the recovery of the shape in step 4, and the pressure drops to the set pressure that exactly matches the low pressure drop resistance due to the low viscosity of the working fluid in step 14, and the valve body 3 balances with the fluid pressure and maintains the valve closed state to operate normally. Continue driving. If abnormal pressure actually occurs in the hydraulic system for some reason, only then the valve body 3 opens as shown in FIG. 2 to bypass the flow of hydraulic fluid as shown by the arrow.

Note that the present invention is not limited to the above-mentioned embodiments; for example, in the above-mentioned embodiments, a unidirectional shape memory alloy spring 4 is combined with an ordinary spring 6 to constitute a bias type bidirectional element. However, it is also possible to use only unidirectional shape memory alloy springs, bidirectional shape memory alloy springs, or various combinations thereof.
Moreover, the type of the pressure valve itself can be changed in various ways.

〔Effect of the invention〕

Since the present invention is made as described above, although it has a very simple configuration, the set pressure for opening the valve automatically changes according to the temperature change of the hydraulic fluid, and when the hydraulic fluid has high viscosity and low temperature, the set pressure The set pressure is low at high temperatures with low viscosity, making it a very convenient pressure valve to be applied to bypass valves in hydraulic systems that are affected by pressure loss that varies greatly depending on viscosity.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a sectional view showing the valve closed state during normal operation, FIG. 2 is a sectional view showing the valve opening state when abnormal pressure occurs, and FIG. 3 is a sectional view showing the valve opening state when abnormal pressure occurs. is in Figure 1! FIG. 3 is a plan view taken along line If-III. 1... Frame, 1C... Valve seat, 2... 8 rods, 3
... Valve body, 4... Shape memory alloy spring, 5... Seat, 6... Ordinary spring. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a pressure valve for a hydraulic system that automatically opens a valve body to change the flow when the hydraulic fluid exceeds a set pressure, a unidirectional or bidirectional shape memory alloy spring is attached to the valve body, Alternatively, one of the shape memory alloy springs described above and a normal spring may be provided in combination, and due to the shape memory action of the shape memory alloy spring, the set pressure at which the valve body opens is high when the hydraulic fluid is low temperature, and high when the hydraulic fluid is high temperature. A pressure valve for a hydraulic system, characterized in that it is configured to automatically fluctuate at a low level.