JPH0416336Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Field of the invention This invention is applicable to, for example, 20 to 80 mm water column (mmH ₂
The present invention relates to a pressure switch that operates at a low pressure of O) and detects gas leakage and the like.

(b) Background of the invention As the pressure switch in the above example, the movement of a pressure receiving element (for example, a metal bellows) that expands and contracts in response to changes in the pressure of the fluid is transmitted to the plunger, and the action switch is activated in conjunction with the forward and backward movement of the plunger. One that opens and closes the contact part is being considered.

In this case, as shown in FIG. 3, the plunger A is supported by the switch case B so that it can move forward and backward, the protrusion C of the plunger A faces the pressure receiving element D, and the pusher E corresponds to the action switch F. , when the temperature of the atmosphere in which this pressure switch is used increases and the plunger A and switch case B expand, the pushing force of the projection C against the pressure receiving element D and the pushing force of the pusher E against the action switch F change. Therefore, the pressure-switching stroke characteristics of the pressure switch change depending on the temperature, which causes switching accuracy to deteriorate.

Therefore, it was considered to use a metal material for the plunger, but since the switch case is made of resin, it is still susceptible to expansion due to temperature changes and deterioration of switching accuracy. It is bound to cause sexual problems.

(c) Purpose of the invention This invention effectively maintains the positional relationship and pushing force relationship among the pressure receiving element, plunger, and action switch even if the operating atmosphere temperature fluctuates and the plunger and switch case expand. The object of the present invention is to provide a pressure switch that maintains the pressure-switching stroke characteristics with high accuracy.

(d) Summary of the invention This invention features a pressure switch in which a synthetic resin material with a large coefficient of linear expansion is used for the switch case that holds the plunger so that it can move forward and backward, and a synthetic resin material with a small coefficient of linear expansion is used for the plunger. do.

(e) Effects of the invention According to this invention, when the temperature of the atmosphere in which the pressure switch is used rises and both the switch case and the plunger expand, the activation On the action switch side, the distance between the plunger and the action switch increases, and the action switch cannot be opened or closed unless the plunger moves back and forth significantly. In other words, the switching stroke becomes longer and the set pressure for opening and closing the switch must increase.

However, on the pressure-receiving element side, the forward and backward movement of the pressure-receiving element depends entirely on the relative pressing force relationship with the plunger, and the expansion of the switch base does not reach the above-mentioned relative pressing relationship, so the expansion of the plunger causes the pressure-receiving element to move. Press the plunger hard to lower the set pressure. In other words, the pressure receiving element can operate the plunger with a small amount of movement (pressure).

In this way, on the one hand, the switching stroke becomes longer and the set pressure increases, and on the other hand, the set pressure for driving the plunger by the pressure receiving element decreases, resulting in a positive and negative zero relationship.
The pressure-switching stroke characteristics of the pressure switch no longer change.

Therefore, a highly accurate pressure switch whose switch characteristics change little with respect to changes in the operating atmosphere temperature can be obtained, and stable reliability can be obtained because the contact pressure does not change.

(F) Embodiment of the invention An embodiment of the invention will be described below in detail based on the drawings.

The drawing shows a pressure switch, in FIG.
This pressure switch includes a cylindrical pressure receiving flange 1 and a disk-shaped protective cap 4 having a pressure receiving port 3 attached to the upper end flange portion 2 of the pressure receiving flange 1.
A switch case 5 made of synthetic resin, a ring-shaped metal holding plate 7 attached to an annular recess 6 in the vertically intermediate portion of the switch case 5, and a pressure receiving port communicating with the pressure receiving port 3 described above. Located in room 8,
A pressure receiving element 9 that expands and contracts in response to changes in gas or other fluid pressure; A plunger 11 that moves forward and backward in conjunction with the pressure receiving element 9 and is disposed within the plunger sliding hole 10 of the switch case 5; Skirt portion 1 in switch case 5 of
By engaging the locking protrusions 14, 14 in the locking holes 13, 13, the switch base 15, which is fixed to the switch case 5, and the plunger 11, which is assembled to the switch base 15, are assembled. It is provided with an action switch 16 that opens and closes between the contact portions in conjunction with forward and backward movement.

Here, the aforementioned pressure receiving flange 1 has its lower end
It is fixed to the upper outer periphery of the holding plate 7 in an airtight manner.

Further, the aforementioned pressure receiving element 9 includes a cylindrical metal bellows 17 whose lower end is fixed to the holding plate 7, a bellows top plate 18 that seals the upper end opening of this metal bellows 17, and a tightly fixed fixation to the top surface of this bellows top plate 18. The outside of the pressure receiving element 9 is set as the above-mentioned pressure receiving chamber 8, and the inside of the pressure receiving element 9 is set as an atmospheric pressure chamber 20.

Further, an input fixed terminal 21 is formed as an insert on the right side of the switch base 15, and an output fixed terminal 22 is formed as an insert on the left side.

Then, by extending the upper end of the input fixed terminal 21 into the switch internal space 23 and bending this extended upper end in the horizontal direction, a fixed piece 24 integrally formed with the input fixed terminal 21 is attached to the upper end of the input fixed terminal 21. is forming.

The above-mentioned fixing piece 24 has its free end connected to the plunger 1.
1, and by forming an opening 25 in this extending portion, the extending end portion 26 is configured to be movable in the vertical direction.

On the other hand, the upper end of the aforementioned output fixed terminal 22 similarly extends into the switch internal space 23, and by bending this extended upper end in the horizontal direction, a fixed tongue piece 27 is integrally formed.

Then, the right inner end of the leaf spring movable piece 28 is locked in the approximately V-shaped notch in the right bent part 30 of the fixed piece 24, and the right end fulcrum part of the biasing spring 29 is It is engaged with the substantially V-shaped notch of the extending end 26 corresponding to the left bent part of the fixed piece 24, and the left end of the biasing spring 29 is engaged with the inside of the left side of the movable piece 28, The above-mentioned elements 21 to 30 constitute the action switch 16.

This action switch 16 is connected to the plunger 1
This is a normally open switch that opens and closes between the fixed contact 31 on the lower surface of the fixed tongue piece 27 and the movable contact 32 on the left upper surface of the movable piece 28 in conjunction with the forward and backward movement of the movable piece 28. The figure shows a state in which the action switch 16 is turned on.

Furthermore, switch case 1 and plunger 11
are both manufactured using synthetic resin materials, and the material used is one with a large coefficient of linear expansion (for example, PON) on the switch case 1 side, and the plunger 1
A material with a small coefficient of linear expansion on the 1 side (e.g. PBT)
_is used to determine the position of the action switch ₁₆ relative to the plunger 11 as shown in FIG. , the amount of change in L ₁ and L ₂ due to temperature rise (amount of elongation)
are made to be the same.

That is, if both the switch case 1 and the plunger 11 expand due to an increase in the temperature of the atmosphere in which the pressure switch is used, the coefficient of linear expansion of the switch case 1 will be larger than that of the plunger 11 if only the action switch 16 side is considered. So,
The distance between the action switch 16 and the pusher 33 of the plunger 11 increases, and the switching stroke becomes longer (the set pressure increases).

However, on the pressure receiving element 9 side, the metal bellows 17
Since the upper end of the switch case 1 is separated from the switch case 1, the expansion of the switch case 1 does not affect the position change of the pressure receiving element 9, and the plunger 1
1, the plunger protrusion 34 strongly presses the bellows top plate 18, and the set pressure decreases.

Therefore, the set pressure increases on the action switch 16 side, and the set pressure decreases on the pressure receiving element 9 side, resulting in positive and negative pressure of the pressure switch.
The switching characteristics no longer change.

In other words, if the plunger protrusion 44 presses the bellows top plate 18, the plunger 11 will operate (move upward) with a lower pressure, but at the same time, the plunger 11 must not move upward over a long distance (the set pressure must increase). (b) Since the action switch 16 cannot be turned ON, the side length of the switch case expands from l ₁ to L ₁ , and the plunger 1
If the relationship L ₁ −l ₁ =L ₂ −l ₂ is maintained when L ₁ expands from l ₂ to L 2 , the action switch 16 will always operate at the desired set pressure. Become.

Note that the contacts within the scope of the utility model registration claims correspond to the fixed contact 31 and the movable contact 32 of the embodiment, but the invention is not limited to the configuration of this embodiment.

[Brief explanation of the drawing]

The drawings show one embodiment of this invention; Fig. 1 is a longitudinal sectional view of a pressure switch, Fig. 2 is an explanatory diagram of the operation of the configuration shown in Fig. 1, and Fig. 3 is a diagram illustrating problems in the conventional pressure switch. be. 5...Switch case, 9...Pressure receiving element, 10
...Plunger, 16...Action switch,
31...Fixed contact, 32...Movable contact.

Claims (1)

[Claims for Utility Model Registration] A pressure receiving element that expands and contracts in response to changes in fluid pressure, a plunger that moves forward and backward in conjunction with this pressure receiving element, and an action that opens and closes a contact portion in conjunction with the forward and backward movement of this plunger. A pressure switch equipped with a switch, in which a switch case that holds the plunger so that it can move forward and backward is made of a synthetic resin material with a large coefficient of linear expansion, and the plunger is made of a synthetic resin material with a small coefficient of linear expansion. .