JP2797762B2 - Diaphragm welding method of pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm welding method for a pressure sensor, and more particularly, to a diaphragm which is covered on a pedestal so as to cover a pressure element provided on the pedestal and transmit pressure to the pressure element. The present invention relates to a diaphragm welding method for a pressure sensor which performs welding while applying a load in the axial direction.

[0002]

2. Description of the Related Art Conventionally, as a welding method, for example,
Japanese Patent Application Laid-Open No. 3-56366 discloses the following lap welding technique. That is, indirect spot welding for temporary attachment is performed by abutting and pressing a movable electrode on the end surface of another plate member superimposed on the plate member, and then build-up welding is performed on the spot weld portion. This ensures the welding strength and eliminates dents in spot welding.

[0003] The technique disclosed in the above-mentioned publication has improved the problem of spot welding performed for temporary attachment in connection with the welding of a plate member. Also, the following welding method employing spot welding for temporary attachment is known.

That is, as shown in FIG. 13, a cylindrical pedestal 21 constituting a pressure sensor is covered with a covered cylindrical diaphragm 22, and a pair of jigs 23 and 24 are provided. Supported by. A pressure element 25 is fixed to one side of the pedestal 21, and the diaphragm 22 is capable of transmitting pressure to the pressure element 25 via pressure transmission members 26 and 27. Then, in order to weld the pedestal 21 and the diaphragm 22, first, a plurality of spot weldings for temporary attachment are performed at the lower edge of the diaphragm 22. Thereafter, seam welding is performed on the entire periphery of the lower end edge of the diaphragm 22 at the same position where the spot welding is performed.
At this time, due to the thermal expansion of the pedestal 21 and the diaphragm 22, the pressure element 25, the pedestal 21, the pressure transmitting members 26, 2
In order to prevent a gap from occurring between the diaphragm 7 and the diaphragm 22, welding is performed while applying a load P in the axial direction of the diaphragm 22 by one jig 23.

[0005]

However, in the conventional diaphragm welding method described above, since melting and solidification occur at the welding location, a force (welding distortion) due to shrinkage has been generated. Therefore, after welding, as shown in FIG. 14, a force VP corresponding to the load P applied to the diaphragm 22 during welding, the spot welding distortion ΔVSP, and the seam welding distortion Δ
The sum with VSH is added to the pressure element 25 as a preload ΔVPR. The value of the preload ΔVPR is desirably stabilized at a constant value in view of the characteristics of the pressure element 25 and the strength of the diaphragm 22.
However, in the conventional diaphragm welding method, since the heat input is larger in the seam welding performed over the entire circumference of the diaphragm 22, the ratio of the seam welding strain ΔVSH to the preload ΔVPR is extremely large. Moreover, since the seam welding strain ΔVSH is unstable, there is a problem that the value of the preload ΔVPR fluctuates greatly and becomes inconsistent.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to reduce the influence of welding distortion and to stabilize the value of a preload applied to a pressure element after welding. To provide a diaphragm welding method.

[0007]

In order to achieve the above object, according to a first aspect of the present invention, a pressure element provided on a pedestal is covered by the pedestal so that pressure can be transmitted to the pressure element. In the diaphragm welding method of the pressure sensor for welding the obtained diaphragm while applying a load in the axial direction thereof, first, the diaphragm and the pedestal are spot-welded at a plurality of positions above the lower end edge of the diaphragm.
Thereafter, the diaphragm and the pedestal are seam-welded all around the lower edge of the diaphragm.

[0008] Similarly, in order to achieve the above object, the second
In the invention, a diaphragm of a pressure sensor for welding a diaphragm covered on the pedestal so as to cover a pressure element provided on the pedestal and capable of transmitting pressure to the pressure element while applying a load in an axial direction thereof. In the welding method, first, a predetermined load is applied to the diaphragm, and the diaphragm and the pedestal are spot-welded at a plurality of positions above the lower end edge of the diaphragm. Thereafter, the diaphragm and the pedestal are subjected to seam welding all around the lower edge of the diaphragm while applying a larger load to the diaphragm than during the previous spot welding.

[0009]

According to the structure of the first invention, first,
Since the diaphragm and the pedestal are spot-welded at a plurality of locations above the lower end edge of the diaphragm, the diaphragm and the pedestal are welded by spot welding with relatively small heat input. After that, seam welding is performed at the lower edge of the diaphragm below the spot welding spot,
Welding distortion due to seam welding having relatively large heat input is absorbed between the seam welded spot and the spot welded spot. Therefore, the proportion of welding distortion due to seam welding in the preload is reduced.

According to the configuration of the second aspect of the present invention, first, the diaphragm and the pedestal are spot-welded at a plurality of positions above the lower end edge of the diaphragm. The diaphragm and the pedestal are welded. After that, seam welding is performed at the lower edge of the diaphragm below the spot welding spot, so welding distortion due to seam welding with relatively large heat input,
It is absorbed between the seam weld and the spot weld. Moreover, since the load applied to the diaphragm during seam welding is greater than that during spot welding, welding distortion due to seam welding is further reduced. Therefore, the ratio of welding distortion due to seam welding to the preload is further reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a first embodiment of a diaphragm welding method for a pressure sensor according to the first invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view for explaining a welding method in this embodiment. That is, a cylindrical metal pedestal 1 having a cylindrical shape that covers a cylindrical metal pedestal 1 that constitutes a pressure sensor is covered with a jig 3 in which both of them 1 and 2 form an upper and lower pair.
Supported between four. A pressure element 5 is provided above the pedestal 1.
Is fixed, and a pair of leads 6 extending from the pressure element 5 extend downward through the hole 1a of the pedestal 1.
Diaphragm 2 is connected to pressure element 5 via pressure transmitting members 7 and 8 on the inner side thereof so that pressure can be transmitted. In performing welding, the diaphragm 2 is used to prevent a gap from being generated between the pressure element 5, the pedestal 1, the pressure transmitting members 7, 8 and the diaphragm 2 due to thermal expansion of the pedestal 1 and the diaphragm 2. Is applied in advance in the axial direction by the jig 3 on the upper side.

The welding method of this embodiment uses both spot welding and seam welding. In FIG. 1, the lower edge of the diaphragm 2 is a seam welding position Y1, and a slightly higher position is a spot welding position. Y2.

As shown in FIG. 8, the pressure sensor manufactured in this embodiment is assembled together with cases 9, 10, a terminal holder 11, a terminal 12, a packing 13 and the like to form a pressure sensor assembly 14. It is supposed to.

Next, the procedure of welding will be described. FIGS. 2 to 6 show the pedestal 1 and the diaphragm 2 (hereinafter collectively referred to as “workpieces 15”) supported by the jigs 3 and 4, and the welding laser unit 16 disposed therearound. The laser units 16 are arranged at equal angular intervals (in this embodiment, at 120 ° intervals) around the work 15.
Three output beams 17A extending toward the work 15,
17B and 17C are provided.

First, referring to FIG.
In a state where the work 15 is arranged so that the respective outgoing beams 17A to 17C correspond to the spot welding position Y2 of the diaphragm 2, the lasers are simultaneously emitted from the outgoing beams 17A to 17C to perform the first spot welding at three points simultaneously. Do.

Next, after only the laser unit 16 is rotated counterclockwise by 30 °, as shown in FIG.
A second spot welding is performed at the same time.

Subsequently, only the laser unit 16 is set at 30 °
Then, the laser beam is simultaneously emitted from each of the emitted beams 17A to 17C, and the third spot welding is performed simultaneously at three points as shown in FIG.

Further, after only the laser unit 16 is rotated counterclockwise by 30 °, as shown in FIG. 5, laser beams are simultaneously emitted from the respective outgoing beams 17A to 17C.
Fourth spot welding is performed at the same time.

In this manner, by performing spot welding at three points simultaneously and performing spot welding at a total of 12 points by performing spot welding four times at a time, the diaphragm 2 and the pedestal 1 can be welded while preventing the diaphragm 2 from tilting. it can. Here, spot welding is not employed for temporary attachment, but is performed to secure required mechanical strength.

Thereafter, as shown in FIG. 6, the laser unit 16 is fixed at a fixed position, and the output beam 17A is fixed.
The workpiece 15 is moved upward so that .about.17C corresponds to the seam welding position Y1 of the diaphragm 2. Then, at that position, the work 15 is rotated one turn in the counterclockwise direction while performing laser emission from one emission beam 17A to perform seam welding.

In this manner, the lower end edge of the diaphragm 2 is seam-welded, whereby the diaphragm 2 and the base 1 are welded.
And the sealing property between them can be secured. FIG. 7 shows the appearance of the work 15 after the completion of welding. A predetermined distance L is defined between a spot welding position Y2 where a total of 12 spot weldings are performed and a seam welding position Y1 where the seam welding is performed.
Just away. Since the heat input to the diaphragm 2 and the like during spot welding is relatively small, the influence of the welding distortion is small. On the other hand, heat input to the diaphragm 2 and the like during seam welding is relatively large, but the influence of welding distortion is caused by the spot welding position Y2 and the seam welding position Y.
It will be almost absorbed at a distance L between them.

FIG. 9 is a graph showing a change in the force applied to the pressure element 5 during the welding. The horizontal axis of the graph represents time, and the vertical axis represents pressure element 5 corresponding to the force applied to pressure element 5.
Respectively are shown. In this graph, VOFF is an offset value specific to the pressure element 5, and VP is a force corresponding to an axial load P applied during welding. 4
Spot welding distortion ΔV by a series of spot welding
It can be seen that SP occurs and then seam welding causes seam welding distortion ΔV SH. Here, the value obtained by adding the spot welding distortion ΔVSP and the seam welding distortion ΔVSH to the force VP corresponding to the load P is the preload ΔVPR. As is clear from comparison with the graph of the conventional example shown in FIG. 14, the seam welding strain ΔVSH in this embodiment is extremely small. As a result, it can be seen that the preload ΔVPR is reduced to about half that of the conventional example.

Therefore, according to the welding method of this embodiment,
Seam welding distortion due to seam welding with relatively large heat input Δ
Since VSH can be reduced, the ratio of welding distortion (ΔVSP + ΔVSH) to preload ΔVPR can be reduced. As a result, the influence of the unstable seam welding strain ΔVSH on the preload ΔVPR can be reduced, and the value of the preload ΔVPR can be stabilized at a substantially constant value.

Further, according to the welding method of this embodiment, since the value of the preload ΔVPR can be stabilized, even if the characteristics of the pressure element 5 are non-linear, it is possible to suppress the sensitivity variation of the pressure sensor. This makes it possible to realize a more accurate pressure sensor. Moreover, since the preload ΔVPR applied to the pressure element 5 and the diaphragm 2 becomes substantially constant between the sensors, the reliability and stable durability of the sensors can be ensured.

(Second Embodiment) Next, a second embodiment of the diaphragm welding method for a pressure sensor according to the second invention will be described.
Embodiments will be described with reference to the drawings.

FIG. 10 is a sectional view for explaining a welding method in this embodiment. Here, the basic structures of the jigs 3 and 4 used for welding, the work 15 to be welded, and the like are the same as those of the first embodiment, and the same reference numerals are used for the same members. The description is omitted here. Here, the work 1 performed using the above jigs 3 and 4
The description will focus on differences in the welding method of No. 5.

In the welding method according to this embodiment, spot welding and seam welding are used in the same manner as in the first embodiment. In FIG. 10, the lower edge of the diaphragm 2 is located at the seam welding position Y1. A slightly upper position is the spot welding position Y2. This embodiment differs from the first embodiment in the point of the load P applied in the axial direction of the diaphragm 2 during spot welding and seam welding.

That is, the spot welding performed first is the same as that of the first embodiment, and the spot welding position Y2
4 spot welding at the same time by laser unit
The process is repeated for a total of 12 spots. At this time, the load P applied in advance in the axial direction of the diaphragm 2 of the work 15 by the jigs 3 and 4 is set to a primary load P1 ("9 kg" in this embodiment). By this spot welding, the diaphragm 2 and the pedestal 1 can be welded while preventing the diaphragm 2 from tilting. Further, the mechanical strength required for joining the diaphragm 2 and the pedestal 1 can be secured by the spot welding.

The next seam welding is the same as that of the first embodiment. The seam welding is performed by the laser unit at the seam welding position Y1. At this time, the load P applied in the axial direction of the diaphragm 2 of the work 15 by the jigs 3 and 4 is changed to a secondary load P larger than the primary load P1.
2 (in this embodiment, “1” corresponding to twice the primary load P1)
8 kg ”). By this seam welding, a sealing property between the diaphragm 2 and the pedestal 1 can be ensured.

FIG. 11 is a graph showing a change in a force applied to the pressure element 5 during the welding. The horizontal axis of the graph indicates time, and the vertical axis indicates the output of the pressure element 5 corresponding to the force applied to the pressure element 5. In this graph, VOFF
Is an offset value inherent to the pressure element 5, VP1 is a force corresponding to a primary load P1 applied during spot welding, and VP2 is a force corresponding to a secondary load P2 applied during seam welding. It can be seen that spot welding distortion ΔVSP is generated by a series of four spot weldings, then load distortion ΔVL is generated by applying the secondary load P2, and then seam welding distortion ΔVSH is generated by seam welding. Here, the value obtained by adding the spot welding distortion ΔVSP, the load distortion ΔVL, and the seam welding distortion ΔVSH to the force VP1 corresponding to the primary load P1 during spot welding is the preload ΔVPR.
Becomes As is clear from comparison with the graph of the first embodiment shown in FIG. 9, the seam welding strain ΔVSH in this embodiment is clear.
Is about 20% smaller than that of the first embodiment. As a result, it can be seen that the preload ΔVPR is further reduced from that of the first embodiment.

Therefore, according to the welding method of this embodiment,
Seam welding distortion due to seam welding with relatively large heat input Δ
Since VSH can be further reduced, the ratio of welding distortion (ΔVSP + ΔVSH) to preload ΔVPR can be further reduced. As a result, the influence of the unstable seam welding distortion ΔVSH on the preload ΔVPR can be reduced, and the value of the preload ΔVPR can be stabilized more stably.

Further, according to the welding method of this embodiment, the value of the preload ΔVPR can be more properly stabilized.
It is possible to suppress the sensitivity variation of the pressure sensor,
It is possible to realize a more accurate pressure sensor.
In addition, since the preload VPR applied to the pressure element 5 and the diaphragm 2 becomes substantially constant between the sensors, the reliability and stable durability of the sensors can be ensured.

It should be noted that the present invention is not limited to the above-described embodiments, but may be carried out as follows by appropriately changing a part of the configuration without departing from the spirit of the invention. (1) In each of the embodiments described above, spot welding at three points
The spot welding was performed 12 times in total, and a total of 12 spots were welded.
As shown in the graph of FIG.
The welding may be performed once, and then the seam welding may be performed.
As is clear from the graph of FIG.
VSH is smaller than that in the graph of FIG. 9 in the first embodiment, and it can be seen that the seam welding distortion ΔVSH decreases as the number of spot welds increases. By the way, the number of spot welding at three points simultaneously is 4
The number of times is not limited to six or six, and may be any other number.

(2) In each of the above embodiments, the spot welding is performed at the same time at three points. However, the present invention is embodied as the spot welding at two points or at the same time, or the spot welding at only one point is performed. It may be embodied when performing a plurality of times. In this case, the mechanical strength of welding can be increased as the total number of spot welding points increases, but the total number of spot welding points may be two or more.

[0036]

As described above in detail, according to the first aspect, first, the diaphragm and the pedestal are spot-welded at a plurality of positions above the lower end edge of the diaphragm, and thereafter, the diaphragm and the pedestal are joined to each other. Since seam welding is performed on the entire circumference of the lower edge, distortion due to seam welding with large heat input can be reduced, the effect of welding distortion can be reduced, and the preload value applied to the pressure element after welding can be kept constant. Demonstrates excellent effects.

According to the second invention, first, while applying a predetermined load to the diaphragm, the diaphragm and the pedestal are spot-welded at a plurality of positions above the lower end edge of the diaphragm. While applying a larger load to the diaphragm, the diaphragm and the pedestal are seam welded all around the lower edge of the diaphragm, so the distortion due to seam welding with a large heat input is further reduced, and the effect of welding distortion is further reduced. As a result, the preload value applied to the pressure element after the welding can be more stably maintained.

[Brief description of the drawings]

FIG. 1 is a sectional view for explaining a diaphragm welding method for a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view for explaining a spot welding procedure in the first embodiment.

FIG. 3 is a plan view for explaining a procedure of spot welding in the first embodiment.

FIG. 4 is a plan view for explaining a procedure of spot welding in the first embodiment.

FIG. 5 is a plan view for explaining the procedure of spot welding in the first embodiment.

FIG. 6 is a plan view illustrating seam welding in the first embodiment.

FIG. 7 is a front view showing the appearance of the pressure sensor after welding is completed in the first embodiment.

FIG. 8 is a sectional view showing a pressure sensor assembly according to the first embodiment.

FIG. 9 is a graph illustrating a change in a force applied to a pressure element during welding in the first embodiment.

FIG. 10 is a sectional view for explaining a diaphragm welding method for a pressure sensor according to a second embodiment of the present invention.

FIG. 11 is a graph illustrating a change in a force applied to a pressure element during welding in a second embodiment.

FIG. 12 is a graph illustrating a change in a force applied to a pressure element during welding in another embodiment embodying the present invention.

FIG. 13 is a cross-sectional view illustrating a welding method in a conventional example.

FIG. 14 is a graph illustrating a change in a force applied to a pressure element during welding in a conventional example.

[Explanation of symbols]

1 pedestal, 2 diaphragm, 5 pressure element, Y1 seam welding position, Y2 spot welding position, P1 primary load, P2 secondary load.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01L 7/00 G01L 9/00 G01L 23/22

Claims (2)

(57) [Claims] 1. A diaphragm of a pressure sensor for welding a diaphragm covered on a pedestal so as to cover a pressure element provided on the pedestal and transmit pressure to the pressure element while applying a load in an axial direction thereof. In the welding method, first, the diaphragm and the pedestal are spot-welded at a plurality of positions above the lower edge of the diaphragm,
Thereafter, the diaphragm and the pedestal are seam-welded around the entire lower edge of the diaphragm. 2. A diaphragm of a pressure sensor for welding a diaphragm covered on a pedestal so as to cover a pressure element provided on the pedestal and transmit pressure to the pressure element while applying a load in an axial direction of the diaphragm. In the welding method, first, while applying a predetermined load to the diaphragm, the diaphragm and the pedestal are spot-welded at a plurality of positions above a lower end edge of the diaphragm, and thereafter, the diaphragm is subjected to a load larger than that at the time of the previous spot welding. A diaphragm welding method for a pressure sensor, wherein the diaphragm and the pedestal are seam-welded around the entire lower end edge of the diaphragm.