JPH11173936A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor which can be assembled without deteriorating the accuracy of its output value. SOLUTION: The pressure sensor is constituted in such a way that a body 12 housing a detecting element 11 is arranged on one surface of a circuit board 20 and a thick film resistor 21 which adjusts the output value of the sensor is arranged on the other surface of the board 20. In addition, a pressure port 14 through which a pressure detecting fluid is introduced to the body 12 is protruded from the body 12 and a terminal board connected to the board 20 is fixed to the main body 31 of a case 30. Consequently, the terminal board can be connected to the circuit board 20 when the pressure port 14 is inserted into the main body 31. When the port 14 is inserted into the main body 31, the thick film resistor 21 is exposed on a lid 32 side. Therefore, when the lid 32 is put on the main body 31 after the resistor 21 is trimmed, the circuit board 20 can be housed in the case 30 without generating a stress in the circuit board 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor.

[0002]

2. Description of the Related Art Conventionally, there has been provided a pressure sensor in which a thin film diaphragm is formed on a silicon substrate by a semiconductor manufacturing technique, and a pressure acting on the diaphragm is converted into an electric signal using a strain gauge. As shown in FIG. 10, this type of pressure sensor includes a synthetic resin body 12 for accommodating a detection element 11 which is a sensor chip formed on a silicon substrate.
The lead 13 connected to 1 is fixed to a circuit board 20 made of a printed board by soldering, and the circuit board 20 on which the body 12 is mounted is housed in a case 30. The circuit board 20 is provided with an output circuit for amplifying the output of the detection element 11 or correcting the output value. As shown in FIG. 11, a thick film for adjusting the output value is provided. A resistor 21 (also serving as temperature compensation) is also provided.
The thick film resistor 21 is trimmed by a laser beam and adjusted to an appropriate resistance value. The case 30 is provided on the circuit board 2.
0, a box-shaped case body 31 that is open on one side,
The case 32 is formed by a lid 32 that covers the opening surface of the case body 31.

As shown in FIG. 12, a pipe-shaped pressure port 14 for introducing a pressure detection fluid to the detection element 11 is projected from the body 12, and the pressure port 14 is connected to the circuit board 2.
It is inserted through the through hole 22 formed at 0. Terminal pins 23 for connecting to an external circuit are provided on the circuit board 20 so as to protrude from the surface on which the body 12 is disposed. This circuit board 20 is shown in FIG.
The terminal pins 23 are inserted into the case main body 31 as shown in FIG. The trimming of the thick film resistor 21 is performed in this state.

When the thick film resistor 21 is trimmed,
A lid 32 is covered on the case main body 31, and the case main body 31 and the lid 32 are fixed by ultrasonic welding or the like. here,
A through-hole 33 through which the pressure port 14 is inserted is formed in the lid 32, and an O-ring 34 is mounted in the through-hole 33, and the pressure port 14 is pressed into the O-ring 34.

[0005]

In the conventional structure described above, the surface of the circuit board 20 on which the thick film resistor 21 is formed and the lid 32 of the case 30 into which the pressure port 14 is press-fitted.
Therefore, after correcting the output value by trimming the thick film resistor 21, the pressure port 14 is pressed into the O-ring 34 mounted on the lid 32. As a result, when the pressure port 14 is pressed into the O-ring 34, a stress is generated in the circuit board 20. Further, since the terminal pins 23 are fixed to the circuit board 20 by soldering and the terminal pins 23 are drawn out of the case 30 without being fixed to the case 30, when the terminal pins 23 are connected to an external circuit, stress is applied to the circuit board 20. May occur. As described above, when a stress is applied to the circuit board 20, the thick film resistor 21 is deformed and the output value changes. As a result, the output value varies from product to product and the accuracy of the output value decreases. Occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure sensor capable of preventing a decrease in output value accuracy due to an assembling operation.

[0007]

According to a first aspect of the present invention, there is provided a detection element for detecting a pressure, a body provided with a pressure port for accommodating the detection element and introducing a pressure detection fluid, and receiving an output of the detection element. An output circuit in which the output value is adjusted to a desired range by trimming the thick film resistor, a circuit board on which the body and the thick film resistor are arranged, a terminal plate for connecting the circuit board to an external circuit, a pressure port and a terminal plate A case for accommodating a circuit board in a form in which a part of the circuit board is pulled out to the outside, the case is formed by a case body and a lid, and a through hole through which a pressure port is inserted is formed in the case body, and a terminal plate is formed. Is fixed, the body and the thick film resistor are distributed separately on the front and back of the circuit board, and the thick film resistor provided on the circuit board with the pressure port inserted through the through hole formed in the case main body on the lid side It is intended to leave. According to this configuration, the thick film resistor can be exposed in a state where the pressure port is inserted into the through hole formed in the case body and the detection element and the terminal plate are connected to the circuit board. After adjusting the resistance of the thick-film resistor, the resistance does not change after the adjustment of the resistance of the thick-film resistor. The drop can be prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, the air introduction pipe for introducing the atmosphere into the body is connected to the body, and the through hole has a diameter larger than the outer diameter of the air introduction pipe provided on the lid. The air introduction pipe is drawn out of the case through the case, and the case is filled with a potting agent. According to this configuration, since the atmosphere is introduced into the detection element by the atmosphere introduction pipe, the pressure can be measured based on the atmospheric pressure. In addition, since the potting agent is filled in the case, the environment resistance is improved. Will be higher.

According to a third aspect of the present invention, in the first or second aspect, the terminal plate is inserted into a groove formed in the case main body and is held between the case main body and the lid. An external connection piece extending continuously from the piece and inserted into the lid, and a circuit connection piece extending continuously and integrally from the fixed piece, forming a substantially U-shape with the fixed piece, and having a tip connected to the circuit board. It is. According to this configuration, since the fixing piece is held between the case body and the lid, the fixing piece of the terminal plate can be firmly fixed to the case, and even if an external force acts on the external connection piece. No external force is transmitted to the circuit connecting piece, and as a result, no external force acts on the circuit board through the terminal plate, so that a change in the resistance value of the thick film resistor can be prevented.

According to a fourth aspect of the present invention, in the third aspect, the fixing piece and the external connection piece are formed by folding a sheet metal into two. In this configuration, since the portion where the external force acts on the terminal plate is folded in two, the strength of the portion where the external force acts is increased, and the deformation of the circuit board due to the external force can be prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) In the following description, members denoted by the same reference numerals as those of the conventional configuration have the same functions. As shown in FIG. 1, the present embodiment includes a synthetic resin body 12 that houses the detection element 11, and a lead 13 connected to the pull detection element 11 is drawn out of the body 12. The body 12 is formed in a box shape with one surface opened, a pressure port 14 protrudes from a bottom wall, and a cover plate 15 is covered on the opening surface. As shown in FIG. 2, an air introduction hole 16 is formed in the surface of the body 12 on which the pressure port 14 is provided so that the pressure can be measured based on the atmospheric pressure.
The lead 13 is drawn out of the body 12 in a direction opposite to the pressure port 14, and is fixed by soldering to a circuit board 20 on which an output circuit for amplifying the output of the detecting element 11 and adjusting the output value range is mounted. .

On the surface of the circuit board 20 opposite to the surface facing the body 12, a thick film resistor 2 for adjusting an output value is provided.
1 is provided. By the way, a terminal board 24 (see FIG. 4) is soldered to the circuit board 20 for connection to an external circuit. The terminal plate 24 is formed by bending a conductive sheet metal having the shape shown in FIG. 3A into the shape shown in FIG. That is, as shown in FIG. 3A, the terminal plate 24 extends from the rectangular fixing piece 24a, the external connection piece 24b extending from one side of the fixing piece 24a, and the other side of the fixing piece 24a. The fixed metal piece 24a and the external connection piece 24b are folded in two at the portion shown by the broken line in FIG. By bending into a substantially U-shape, the tip of the board connection piece 24c is extended in the same direction as the external connection piece 24b. By forming the terminal plate 24 into such a shape, the fixing piece 24a and the external connection piece 24 are formed.
b increases in strength.

The board connecting piece 24c is connected to the circuit board 20 by soldering so as to be inserted from the surface of the circuit board 20 on which the body 12 is arranged. In this state, the fixing piece 24a
Are partly opposed to the side surfaces of the circuit board 20, and the external connection pieces 24
b is extended to the side of the circuit board 20 on which the thick film resistor 21 is formed. By the way, the case 30 is
The case body 31 is provided with a box-shaped case body 31 having an opening on one side and a lid 32 covered on the opening surface of the case body 31.
A through-hole 33 through which the pressure port 14 is inserted is formed at the center of the bottom wall of the case body 31, and an O-ring 34 is mounted in the through-hole 33.
Press-fit. Here, the fixing piece 24 of the terminal plate 24 soldered and fixed to the circuit board 20 is provided on the peripheral wall of the case body 31.
a and a groove 35 for accommodating the circuit connecting piece 24c. The groove 35 is provided between the circuit connecting piece 24c and the fixing piece 24a.
Is formed in a substantially T-shape so as to be able to be introduced. That is, as shown in FIG. 4, when the circuit board 20 is housed in the case body 31, the thick film resistor 21 is exposed to the opening side of the case body 31, and the fixing piece 24 a of the terminal plate 24 is held in the groove 35. Will be.

In this state, the thick film resistor 21 is subjected to laser trimming to adjust the output value, and then the case body 31 is covered with the lid 32. The cover 32 has an insertion hole 36 through which the external connection piece 24b of the terminal plate 24 is inserted, and the fixing piece 24a of the terminal plate 24 is locked around the insertion hole 36. Further, a fixing hole 37 is formed in the lid 32, and a fixing protrusion 38 protruding from the case body 31 is passed through the fixing hole 37, and then heat caulked (the tip of the fixing protrusion 38 is melted by heat and crushed). ) To fix the case body 31 and the lid 32 together. Thus, a pressure sensor having a shape as shown in FIG. 5 can be formed.

The terminal plate 24 has the above-described shape to increase the strength of the fixing piece 24a and the external connection piece 24b, and the fixing piece 24a is sandwiched between the case body 31 and the lid 32 so that the terminal plate 24 Is fixed, no external force is transmitted to the circuit board 20 even when an external force acts on the external connection piece 24b, and no stress is generated on the circuit board 20 when an external circuit is connected.

That is, when assembling, the pressure port 14
Into the O-ring 34 and the terminal plate 24 into the groove 3
The circuit board 20 is mounted on the case main body 31 in a state where the circuit board 20 is press-fitted into the case 5, and the board connecting pieces 24 c and the leads 13 of the terminal board 24 are fixed to the circuit board 20 by soldering. After that, the thick film resistor 21 is trimmed to adjust the output value,
Is covered with the case body 31 and heat caulking is performed.
When assembled in such a procedure, the thick film resistor 21 is trimmed after the pressure port 14 is press-fitted into the O-ring 34 provided on the case main body 31, so that the circuit board 20 is not stressed after the trimming of the thick film resistor 21. Does not occur, the output value can be kept at the adjusted value, and the accuracy of the output value can be increased (variation can be reduced).

(Embodiment 2) In this embodiment, as shown in FIG. 6, an air introduction pipe 17 is protruded from a cover plate 15, and a through hole 22 provided in a circuit board 20 and a through hole provided in a lid 32. 39, the air introduction pipe 17 is inserted. Here, through hole 3
9 is formed to have a diameter larger than the outer diameter of the atmosphere introduction pipe 17. The atmosphere introduction pipe 17 is for introducing the atmosphere into the body 12, and the provision of the atmosphere introduction pipe 17 makes the atmosphere introduction hole 16 unnecessary. In a state where the cover plate 15 is connected to the body 12, as shown in FIG.
The pressure port 14 and the air introduction pipe 17 are respectively provided on both sides of the substrate.

The through hole 33 provided in the case body 31 has two holes.
O-rings 34a and 34b are attached, and both O-rings 3
The pressure port 14 is press-fitted into 4a, 34b. here,
The terminal plate 24 having the same shape as that of the first embodiment is
8, the circuit connecting piece 24c of the terminal board 24 and the lead 13 are connected to the circuit board 20 with the air introduction pipe 17 inserted through the through hole 22 of the circuit board 20 as shown in FIG. To the solder. In this state, the thick film resistor 21 is trimmed by laser to adjust the output value.

In this embodiment, the case body 31 is filled with a potting agent 40 of a synthetic resin and the circuit board 20 is potted and sealed as shown in FIG. 9 in order to improve environmental resistance. As described above, the through hole 33 of the case body 31
The reason why two O-rings 34b are mounted on the O-ring is to use one O-ring 34a to prevent leakage of the pressure detecting fluid and use the other O-ring 34b to prevent leakage of the potting agent 40. After potting sealing the case body 31 as described above, the air introduction pipe 17 is
A lid 32 is covered on the case body 31 so as to be inserted into the case body 31, and heat caulking is performed in the same manner as in the first embodiment so that the case body 31 and the lid 3 are covered.
And 2.

In the configuration of this embodiment, the pressure port 1
5 is pressed into the O-rings 34a and 34b, and the terminal plate 24 is pressed into the case body 31, and then the terminal plate 24 and the leads 13 are fixed to the circuit board 20 by soldering. Because it will be applied
After the trimming of the thick film resistor 21, no stress is generated in the circuit board 20, and the accuracy of the output value can be increased. Other configurations and operations are the same as those of the first embodiment.

[0021]

According to the first aspect of the present invention, there is provided a sensing element for detecting a pressure, a body provided with a pressure port for accommodating the sensing element and introducing a pressure sensing fluid, and a thick film resistor for receiving an output of the sensing element. An output circuit whose output value is adjusted to a desired range by trimming, a circuit board on which a body and a thick-film resistor are arranged, a terminal board for connecting the circuit board to an external circuit, and a part of the pressure port and the terminal board. A case for accommodating the circuit board in a form pulled out to the outside, the case is formed by a case body and a lid, a through hole through which a pressure port is inserted is formed in the case body, and a terminal plate is fixed, The body and the thick film resistor are distributed separately on the front and back of the circuit board, and the thick film resistor provided on the circuit board is exposed on the lid side with the pressure port inserted through the through hole formed in the case body. The thick film resistor can be exposed while the pressure port is inserted through the through hole formed in the case body and the detection element and the terminal board are connected to the circuit board. After the adjustment, there is no step in which an external force acts on the circuit board, and the resistance value does not change after adjusting the resistance value of the thick film resistor.
As a result, there is an advantage that a decrease in the accuracy of the output value can be prevented.

As in the second aspect of the present invention, an air introduction pipe for introducing air into the body is connected to the body, and the air introduction pipe is formed through a through hole having a diameter larger than the outer diameter of the air introduction pipe provided on the lid. If the pot is pulled out of the case and filled with a potting agent, the atmosphere is introduced into the detection element by the air introduction pipe, so that the pressure can be measured based on the atmospheric pressure. There is an advantage that environmental resistance is increased by filling the case with the agent.

According to the third aspect of the present invention, the terminal plate is inserted into the groove formed in the case body and held between the case body and the cover, and the terminal plate is extended continuously and integrally from the fixed piece to the cover. In the case of having an external connection piece to be inserted, and a circuit connection piece which is continuously and integrally extended from the fixed piece and has a substantially U-shape with the fixed piece and a tip end portion of which is connected to the circuit board, the fixed piece is made of a case body and a Since the fixing piece of the terminal plate can be firmly fixed to the case, even if an external force acts on the external connecting piece, the external force is not transmitted to the circuit connecting piece, As a result, there is no external force acting on the circuit board through the terminal plate, and there is an advantage that a change in the resistance value of the thick film resistor can be prevented.

According to the fourth aspect of the present invention, when the fixing piece and the external connection piece are formed by folding a sheet metal into two, the portion of the terminal plate where an external force acts is folded into two, so that the external force is reduced. The strength of the part where
There is an advantage that deformation of the circuit board due to external force can be prevented.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing Embodiment 1 of the present invention.

FIG. 2 is a perspective view of a main part of the above.

FIGS. 3A and 3B show a terminal plate used in the above, wherein FIG. 3A is a perspective view showing a state before formation, and FIG. 3B is a perspective view showing a state after formation.

FIG. 4 is a perspective view of a main part of the above.

FIG. 5 is a perspective view of the same.

FIG. 6 is an exploded perspective view showing Embodiment 2 of the present invention.

FIG. 7 is a perspective view of a main part of the above.

FIG. 8 is a perspective view of a main part of the above.

FIG. 9 is a perspective view of a main part of the above.

FIG. 10 is an exploded perspective view showing a conventional example.

FIG. 11 is an exploded perspective view of the same.

FIG. 12 is an exploded perspective view of a main part of the above.

FIG. 13 is a perspective view of a main part of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Detection element 12 Body 13 Lead 14 Pressure port 17 Atmospheric introduction pipe 20 Circuit board 21 Thick film resistor 22 Through hole 24 Terminal board 24a Fixed piece 24b External connection piece 24c Circuit connection piece 30 Case 31 Case main body 32 Cover 33 Through hole 35 Groove 40 Potting agent

Claims (4)

[Claims] An output value is obtained by trimming a thick-film resistor which receives an output of a detection element, a body housing the detection element and having a pressure port for introducing a pressure detection fluid, and receiving the output of the detection element. An output circuit adjusted to a desired range, a circuit board on which a body and a thick film resistor are arranged,
A terminal board for connecting the circuit board to an external circuit, and a case for housing the circuit board in a form in which a part of the pressure port and the terminal board are drawn out to the outside, wherein the case is formed by a case body and a lid; Is formed with a through-hole through which a pressure port is inserted, and a terminal plate is fixed.The body and the thick-film resistor are arranged separately on the front and back of the circuit board, and the pressure port is inserted through a through-hole formed in the case body. A pressure sensor, wherein a thick film resistor provided on a circuit board is exposed on a lid side in a state where the pressure sensor is in a state of being closed. 2. An air introduction pipe for introducing air into the body is coupled to the body, and the air introduction pipe is drawn out of the case through a through hole having a diameter larger than an outer diameter of the air introduction pipe provided on the lid. 2. The pressure sensor according to claim 1, wherein the pot is filled with a potting agent. 3. A fixing plate inserted into a groove formed in the case main body and held between the case main body and the lid,
An external connection piece extending continuously and integrally from the fixing piece and inserted into the lid, and a circuit connection piece extending continuously and integrally from the fixing piece and having a substantially U-shape with the fixing piece and a leading end connected to the circuit board. 3. The method according to claim 1, wherein
A pressure sensor as described. 4. The pressure sensor according to claim 3, wherein the fixing piece and the external connection piece are formed by folding a sheet metal into two.