JPH09282991A - Pressure switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve hysteresis having a great width without any pressure sensor by providing a spring for setting a pressure required for moving a piston serving as one electric contact toward a terminal, and disposing a biting portion to the end of the piston in the terminal. SOLUTION: A large-diameter container hole 14 is formed at one end of a housing 17; in contrast, a slide hole 18, into which a piston 23 is fitted, is opened at the other end thereof. A slit 28 is formed at the center of an end 27 formed of an elastic portion of the piston 23. A coil spring 15 is held between a spacer 13 fitted into the container hole 14 and a holding ring 16 fitted around the piston 23. A tapered hole 29, an inner diameter of which becomes larger toward the piston 23, is formed as a biting portion at the end of a terminal 10 serving as one electric contact disposed in the spacer 13 via an electric insulating resin 12. The electric contact is switched based on a comparison of a pressure exerted on the piston 23 with a value obtained by subtracting biting force of the end 27 to the hole 29 from spring force of a spring 15. In this case, hysteresis having a great width can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure switch used to detect the pressure of a hydraulic system.

[0002]

2. Description of the Related Art A conventional pressure switch for detecting the pressure of a hydraulic system will be described with reference to FIG. Reference numeral 4 is a housing that forms the body of the pressure switch, and the piston 1 on which pressure is applied is slidably inserted into one of the housing 4.
A terminal 2 which is one electric contact is fixed to the other, and a disc spring 3 having a spring mechanism which is the other electric contact is provided between the piston 1 and the terminal 2.
Has been fixed. An O-ring 5 fitted to the outer circumference of the piston 1 is attached to the inner circumference of the housing 4, and one end 6 of the piston 1 extending toward a communication path to a hydraulic device (not shown) is mounted.
The pressure oil that acts on the disk spring 3 is prevented from leaking to the disk spring 3 side.

With this structure, the one end 6 of the piston 1 is
When the pressure P of the hydraulic device is applied to and the pressure P becomes larger than the sum of the spring force of the disc spring 3 and the sliding resistance of the O-ring 5, the piston 1 elastically moves the disc spring 3 toward the terminal 2. It deforms and moves, the disc spring 3 and the terminal 2 come into contact, and the electrical contact is closed (the switch is in the ON state). When the pressure P of the hydraulic device becomes smaller than the value obtained by subtracting the sliding resistance of the O-ring 5 from the spring force of the disc spring 3, the disc spring 3 separates from the terminal 2 and the electrical contact is opened (the switch is OFF). Status).
Thus, there is a difference (hysteresis) in the contact pressure between the disc spring 3 and the terminal 2 and the separation pressure, which is equivalent to the sliding resistance of the O-ring 5, so that the piston 1 will not move even if the pressure applied to the piston 1 drops a little. Since it does not move, it is possible to maintain the state where the disc spring 3 and the terminal 2 are in contact with each other, thereby preventing chattering due to minute pressure fluctuations.

The pressure switch of this construction detects, for example, an increase in the pressure of the hydraulic system when the pressure rises to a predetermined level, and a decrease in the pressure when the pressure decreases to a certain level. used.

[0005]

Since such a conventional pressure switch has a hysteresis due to the sliding resistance of the piston 1 and the O-ring 5, the hysteresis width is only several kgf / cm ² or less. . Therefore, in the conventional pressure switch, the hysteresis width is several tens of kgf / cm.
^I could not set it to a large range of ² . Also, if a pressure sensor is used, the width of hysteresis is several tens of k
Although a wide range of gf / cm ² can be controlled, the pressure sensor is expensive and the control circuit is complicated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a sliding hole is formed in a housing, and a piston forming one electric contact responsive to pressure is formed in the sliding hole. A terminal that is slidably fitted and that forms the other electrical contact is provided so as to face the end of the piston,
When the pressure of the hydraulic device acts on the piston and presses the terminal, the terminal includes a spring that sets a pressure for moving the piston in a direction to approach the terminal, and the terminal bites into the end of the piston. It is characterized in that a chamfered portion that obtains hysteresis by a pushing force is provided at either one of the end portion of the piston and the terminal.

(Operation) The pressure of the hydraulic device acts on the piston extending toward the communication passage to the hydraulic device, and when the pressure becomes larger than the spring force set by the spring, the piston moves toward the terminal to move the piston. The end contacts the terminal and the electrical contact closes. When the piston further moves and presses the terminal, the terminal bites into the end of the piston by the biting portion provided on either one of the end of the piston and the terminal. At this time, this state is maintained as long as the pressure applied to the piston is larger than the value obtained by subtracting the biting force between the piston and the terminal from the spring force of the spring, and the spring force of the spring causes the piston and the terminal to When it becomes smaller than the value obtained by subtracting the biting force between and, the piston separates from the terminal and the electrical contact opens.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 17 denotes a housing which constitutes the main body of the pressure switch, and has a large-diameter storage hole 14 opened at one end and a small-diameter sliding hole 18 communicating with the storage hole 14 at the other end. There is. A threaded portion 19 for attachment to a hydraulic device (not shown) is formed on the outer periphery of the housing 17 on the sliding hole 18 side.

A piston 23 is slidably fitted in the sliding hole 18, and the piston 23 has the receiving hole 1
A slit 28 is formed at the center of the end portion 27 on the fourth side, and the end portion 27 constitutes an elastic portion whose diameter can be reduced. A sliding hole 1 for accommodating a Teflon ring 20 and an O-ring 21 for preventing intrusion of pressure oil from the hydraulic device into the sliding hole 1
A recess 22 having a diameter larger than 8 is formed. Since the outer circumference of the piston 23 is in close contact with the inner circumference of the O-ring 21, the O-ring 21 and the piston 23 have some sliding resistance, which causes the piston 23 to move toward the housing hole 14 side. There is a slight hysteresis in the pressure and the pressure returning to the sliding hole 18 side. The Teflon ring 20 and the O-ring 21 are the end portions 2 of the recess 22 of the housing 17.
By being caulked and deformed to the concave portion 22 side, the movement in the axial direction is restricted. A stopper ring 24 is attached to the outer periphery of the piston 23 protruding from the sliding hole 18, and the stopper ring 24 engages with the end portion 25, so that the piston 23 can be protected against abnormal pressure. It is designed to limit excessive movement to the side.

A spacer 13 is fitted in the housing hole 14, and a retaining ring 16 engaged with the outer periphery of the piston 23 is provided inside the spacer 13, and the spacer 13 and the retaining ring 16 are connected to each other. A coil spring 15 is held between them. The terminal 10 is attached to the spacer 13 via a resin 12 which is an electrical insulator. The spacer 13 is fixed to the housing 17 by caulking and deforming the end portion 26 of the housing hole 14 of the housing 17 toward the housing hole 14 side. Then, after the caulking deformation, the resin 11 is molded and sealed in the opening of the storage hole 14. A taper hole 29 (a biting portion) whose inner diameter increases toward the piston 23 is formed at the end of the terminal 10 facing the piston 23.

Here, the state in which no pressure is acting on the piston 23 is shown on the left side of the axis O, and the state in which the piston 23 bites into the tapered hole 29 of the terminal 10 under pressure is shown on the right side. Show. The pressure switch having the above-mentioned configuration is used when the pressure change of the hydraulic system is several tens of kgf / cm ^2.
The operation in the case of being used for the pressure detection in the case of holding it in such a large range will be described based on FIGS.

When the pressure P of the hydraulic device rises from the uncontacted state shown in FIG. 2 and acts on one end 30 of the piston 23, the coil spring 15 is pressed through the holding ring 16.
When the pressure P acting on the one end 30 of the piston 23 becomes larger than the sum of the spring force set by the coil spring 15 and the sliding resistance of the O-ring 21, the piston 23 moves toward the terminal 10 and the piston 23 moves. When the other end 27 comes into contact with the tapered hole 29 of the terminal 10, the other end 27
It can be detected that the contact state shown in FIG.

When the piston 23 further moves toward the terminal 10, the other end 27 of the piston 23 having the slit 28 formed therein has the tapered hole 2 of the terminal 10.
The tapered hole 29 of the terminal 10 while being reduced in diameter by 9
It bites into and becomes the biting state shown in FIG. The pressure P applied to one end 30 of the piston 23 is obtained by subtracting the biting force between the piston 23 and the tapered hole 29 of the terminal 10 and the sliding resistance of the O-ring 21 from the spring force of the coil spring 15. 4 is maintained, the bite state of FIG.
3 becomes smaller than the value obtained by subtracting the biting force between the tapered hole 29 of the terminal 10 and the sliding resistance of the O-ring 21, the piston 23 separates from the terminal 10 and returns to the non-contact state shown in FIG. It can be detected that the pressure of the device has decreased from a predetermined level by several tens of kgf / cm ² .

As described above, since the slit 28 is formed in the end portion 27 of the piston 23 and the tapered hole 29 is formed in the end portion of the terminal 10 which comes into contact with the end portion 27, the end portion of the piston 23 is formed. When 27 comes into contact with the tapered hole 29 of the terminal 10 and further moves and presses, a force toward the central axis is applied to the end portion 27 by the tapered hole 29, and the end portion 27 is reduced in diameter and bites into the tapered hole 29. Therefore, when the end portion 27 of the piston 23 bites into the tapered hole 29 of the terminal 10, the end portion 27 of the piston 23 maintains a state of contact due to the biting force between the end portion 27 of the piston 23 and the tapered hole 29 of the terminal 10. The pressure P acting on 23 is several tens of kgf / c
The contact state can be maintained even if m ^{2 is} decreased, and the pressure switch can have a large hysteresis.

In the embodiment of the present invention, the piston is provided with the slit and the terminal is provided with the tapered portion.
You may form a slit in a terminal and provide a taper part in a piston. Further, any structure may be used as long as a biting force can be created by the biting force between the piston and the terminal.

[0016]

As described above, according to the present invention, when the pressure acts on the piston to press the terminal, the terminal bites into the end portion of the piston and the biting portion that obtains hysteresis by the biting force Since the pressure switch is provided at either one of the end and the terminal, the pressure switch can have a large hysteresis of several tens kgf / cm ² . Further, the control circuit is not complicated as compared with the case where an expensive pressure sensor is used.

[Brief description of drawings]

FIG. 1 is a sectional view of a pressure switch showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a non-contact state between the piston and the terminal in the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a contact state between the piston and the terminal according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a bite state of the piston and the terminal in the embodiment of the present invention.

FIG. 5 is a sectional view showing a conventional pressure switch.

[Explanation of symbols]

 10 Terminal 14 Storage Hole 15 Coil Spring 16 Retaining Ring 17 Housing 18 Sliding Hole 21 O-ring 23 Piston 27 End 28 Slit 29 Tapered Hole

Claims (2)

[Claims] 1. A pressure switch for detecting the pressure of a hydraulic system, wherein a sliding hole is formed in a housing, and a piston which is one electric contact responsive to the pressure is slidably inserted into the sliding hole, A terminal that makes the other electrical contact is provided so as to face the end of the piston, and a spring that sets the pressure for moving the piston in the direction approaching the terminal is provided, and the pressure of the hydraulic device acts on the piston to When the terminal is pressed, a biting part which is bitten by the terminal at the end of the piston to obtain hysteresis by the biting force is provided at either one of the end of the piston and the terminal. pressure switch. 2. The pressure switch according to claim 1, wherein the bite portion includes an elastic portion having a slit in either one of the end portion of the piston and the terminal.