JP5853837B2 - Pressure sensor - Google Patents

Description

  The technology disclosed in the present specification relates to a pressure sensor.

  For example, the development of a pressure sensor for measuring the combustion pressure of an internal combustion engine is in progress. Patent Document 1 discloses a pressure sensor that transmits a combustion pressure to a force detection element via a pressure receiving rod disposed in a housing. In such a pressure sensor, a seal structure is provided in order to prevent deposit (soot) generated by combustion from entering between the pressure receiving rod and the housing. In the seal structure of Patent Document 1, an O-ring fitted into a groove on the outer peripheral surface of the pressure receiving rod is used.

JP-A-6-265430

  When manufacturing the pressure sensor of Patent Document 1, the pressure receiving rod is inserted into the housing in a state where the O-ring is fitted in the groove on the outer peripheral surface of the pressure receiving rod. In order to smoothly insert the pressure receiving rod into the housing, the seal load applied to the O-ring cannot be set large. In such a low seal load state, the seal load applied to the O-ring varies greatly due to manufacturing variations in the outer diameter of the pressure receiving rod, the groove depth of the pressure receiving rod, and the inner diameter of the housing. In particular, in a miniaturized pressure sensor, the manufacturing variation with respect to the design dimension increases, so that the seal load applied to the O-ring varies greatly. For this reason, in the pressure sensor of patent document 1, the reliability of a seal structure is low.

  An object of the technology disclosed in this specification is to provide a pressure sensor having a seal structure that is not easily affected by manufacturing variations.

  The pressure sensor disclosed in this specification includes a housing, a pressure receiving rod, a force detection element, a first fixing member, and an elastic seal member. The housing has an inner peripheral surface including a step surface. The housing is hollow and has at least one end opened. The pressure receiving rod is disposed in the housing, and one end face is exposed at one end of the housing. The pressure receiving rod is provided with a jaw portion on the outer peripheral surface facing the step surface of the housing in the axial direction. The force detection element faces the other end face of the pressure receiving rod. The first fixing member is fixed to the housing and faces the stepped surface of the housing through the jaw portion of the pressure receiving rod in the axial direction. The elastic seal member may be provided between the jaw portion of the pressure receiving rod and the stepped surface of the housing, may be provided between the jaw portion of the pressure receiving rod and the first fixing member, and is provided therebetween. May be. In the pressure sensor disclosed in this specification, a sealing load is applied to the elastic sealing member by a compressive load acting between the first fixing member and the stepped surface of the housing.

  In the pressure sensor of the above aspect, the seal load applied to the elastic seal member can be adjusted by a compressive load acting between the first fixing member and the stepped surface of the housing. For this reason, it is hard to receive to the influence of the manufacture variation of the design dimension of each member. In the pressure sensor of the above aspect, the reliability of the seal structure is high.

The schematic sectional drawing of the pressure sensor of 1st Example is typically shown. The principal part enlarged view of the jaw part periphery of a pressure receiving rod is shown. The schematic sectional drawing of another example of the pressure sensor of 1st Example is typically shown. The schematic sectional drawing of another example of the pressure sensor of 1st Example is typically shown. The schematic sectional drawing of another example of the pressure sensor of 1st Example is typically shown.

Some of the technical features disclosed in the present specification are summarized below. The items described below have technical usefulness independently.
(Feature 1) The pressure sensor may include a hollow housing. The housing may have an inner peripheral surface including a step surface. The step surface is a surface extending in a direction different from the axial direction, and may extend in a direction orthogonal to the axial direction, or may extend in a direction inclined with respect to the axial direction. The step surface may be formed between a portion having a small inner diameter and a portion having a large inner diameter. At least one end of the housing may be open.
(Feature 2) The pressure sensor may be provided in the housing, and may include a pressure receiving rod having one end face exposed at one end of the housing. The pressure receiving rod may be provided on the outer peripheral surface with a jaw portion facing the step surface of the housing in the axial direction. The jaw part may have a surface facing the step surface. In particular, the jaw part may have a surface facing the step surface and parallel to the step surface.
(Feature 3) The pressure sensor may include a force detection element facing the other end surface of the pressure receiving rod. The force detection element is an element that varies the output value according to the compression force. In one example, the force sensing element can be a piezoelectric effect, a piezoresistive effect, a magnetostrictive effect, a capacitance change, an optical change such as an optical fiber, or an element using a metal wire.
(Feature 4) The pressure sensor may be provided with a first fixing member that is fixed to the housing and faces the stepped surface of the housing in the axial direction through the jaw portion of the pressure receiving rod. The first fixing member may be fixed to the inner peripheral surface of the housing. In one example, the first fixing member may be fixed to the housing by welding, screwing, caulking, press fitting, or adhesion.
(Feature 5) The pressure sensor may include an elastic seal member. The elastic seal member may be provided between the jaw portion of the pressure receiving rod and the stepped surface of the housing, may be provided between the jaw portion of the pressure receiving rod and the first fixing member, or provided between each. May be. The elastic seal member is desirably a material that can be elastically deformed. In one example, a metal seal member, a resin seal member, or a composite seal member made of metal and resin can be used. The elastic seal member is desirably provided between the jaw portion of the pressure receiving rod and the first fixing member. The pressure transmitted through the pressure receiving rod can be efficiently transmitted to the force detection element.
(Feature 6) In the pressure sensor, a sealing load is applied to the elastic seal member by a compressive load acting between the first fixing member and the stepped surface of the housing. Moreover, the compressive load which acts between the 1st fixing member and the level | step difference surface of a housing is adjusted with the fixing position with respect to the housing of a 1st fixing member.
(Characteristic 7) A through hole may be formed in the first fixing member. In this case, the pressure receiving rod may be arranged so as to pass through the through hole of the first fixing member.
(Feature 8) The pressure sensor according to the seventh aspect may be further provided with a second fixing member that is fixed to the housing and is opposed to the other end surface of the pressure receiving rod in the axial direction via a force detection element. In this case, a preload is applied to the force detection element by a compressive load acting between the second fixing member and the pressure receiving rod. Further, the compressive load acting between the second fixing member and the pressure receiving rod is adjusted by the fixing position of the second fixing member with respect to the housing. In the pressure sensor of this aspect, the seal load and the preload can be adjusted to different sizes. For example, the seal load can be adjusted to be larger than the preload. For this reason, the pressure sensor of this aspect can achieve both the reliability of the seal structure and the pressure detection sensitivity.

  The pressure sensor 1A shown in FIG. 1 is for measuring the combustion pressure of the internal combustion engine, and is attached to the combustion engine so that the lower side in the drawing is exposed in the cylinder of the internal combustion engine. The pressure sensor 1 </ b> A includes a housing 2, a pressure receiving rod 3, an elastic seal member 4, a first fixing member 5, a force detection element 6, and a second fixing member 7. Hereinafter, for convenience of explanation, the lower side in the figure is referred to as the front end side, and the upper side in the figure is referred to as the rear end side.

  As shown in FIG. 1, the housing 2 has a hollow shape in which both ends of the front end side and the rear end side are open. The housing 2 has a first cylindrical portion 2a having a small inner diameter and a second cylindrical portion 2b having a large inner diameter. The first cylindrical portion 2a is located on the front end side, and the second cylindrical portion 2b is on the rear end side. Is located. 2, the inner peripheral surface of the housing 2 includes a first inner peripheral surface 21 corresponding to the first cylindrical portion 2a, a second inner peripheral surface 23 corresponding to the second cylindrical portion 2b, and a first A step surface 22 is provided between the inner peripheral surface 21 and the second inner peripheral surface 23. The first inner peripheral surface 21 and the second inner peripheral surface 23 extend parallel to the axial direction (the vertical direction on the paper surface), and the step surface 22 is a direction orthogonal to the axial direction (the horizontal direction on the paper surface). ).

  As shown in FIG. 1, the pressure receiving rod 3 is disposed in the housing 2, and the end surface on the front end side is exposed from the opening on the front end side of the housing 2. The pressure receiving rod 3 has a substantially columnar shape, and a jaw portion 3a is provided on the outer peripheral surface thereof. As shown in FIG. 2, the jaw portion 3 a of the pressure receiving rod 3 includes a front end surface 31 facing the front end side, a rear end surface 33 facing the rear end side, and a side surface 32 positioned between the front end surface 31 and the rear end surface 33. have. The front end surface 31 and the rear end surface 33 extend in a direction orthogonal to the axial direction, and the side surface 32 extends in parallel to the axial direction. The distal end surface 31 of the jaw portion 3 a of the pressure receiving rod 3 is in contact with the step surface 22 on the inner peripheral surface of the housing 2. The pressure receiving rod 3 is preferably formed of a material having high heat insulation. In one example, zirconia, silicon nitride, or the like is used as the material of the pressure receiving rod 3.

  As shown in FIG. 1, the elastic seal member 4 is disposed between the first fixing member 5 and the jaw portion 3 a of the pressure receiving rod 3, and both the first fixing member 5 and the jaw portion 3 a of the pressure receiving rod 3. Touching. The elastic seal member 4 is an elastically deformable material and is provided so as to close the gap between the first fixing member 5 and the pressure receiving rod 3. In this example, a metal C ring is used for the elastic seal member 4, and stainless steel is used as the material thereof. Further, the seal opening of the elastic seal member 4 faces outward. Instead of this example, the elastic seal member 4 may be a metal E ring, a metal O ring, or a resin seal member.

  As shown in FIG. 1, the first fixing member 5 is disposed in the housing 2 and has a ring shape having a through hole 5 a. The first fixing member 5 faces the stepped surface of the housing 2 through the jaw portion 3 a of the pressure receiving rod 3. In this example, stainless steel is used as the material of the first fixing member 5. The first fixing member 5 is fixed to the second cylindrical portion 2b of the housing 2 by a welded portion 5W. The welded portion 5W can be formed by laser welding from the outer peripheral surface side of the housing 2.

  As shown in FIG. 1, the force detection element 6 is disposed between the end surface on the rear end side of the pressure receiving rod 3 and the second fixing member 7, and the end surface on the rear end side of the pressure receiving rod 3 and the second fixing member 7. Both members 7 are in contact. The force detection element 6 provides an output value depending on a change in applied load. In this example, a semiconductor pressure sensor using a piezoresistance effect is used for the force detection element 6.

  As shown in FIG. 1, the second fixing member 7 is disposed in the housing 2 and has a disk shape having a through hole 7 a in part. The second fixing member 7 is fixed to the second cylindrical portion 2b of the housing 2 by a welded portion 7W. The welded portion 7 </ b> W can be formed by laser welding from the outer peripheral surface side of the housing 2. A wiring (not shown) that is electrically connected to the force detection element 6 is disposed in the through hole 7 a formed in the second fixing member 7.

  Next, the assembly process of the pressure sensor 1A will be described. First, the pressure receiving rod 3, the elastic seal member 4, and the first fixing member 5 are inserted from the rear end side of the housing 2. The first fixing member 5 is pressed toward the distal end side, and the first fixing member 5 is fixed to the housing 2 using laser welding at a position where a desired sealing load is applied to the elastic seal member 4. Next, the force detection element 6 and the second fixing member 7 are inserted from the rear end side of the housing 2. The second fixing member 7 is pressed toward the distal end side, and the second fixing member 7 is fixed to the housing 2 using laser welding at a position where a desired preload is applied to the force detection element 6.

  Next, the operation of the pressure sensor 1A will be described. When combustion pressure is applied to the end face on the front end side of the pressure receiving rod 3, the pressure receiving rod 3 is displaced about several μm toward the rear end side in the housing 2. When the pressure receiving rod 3 is displaced to the rear end side, a compressive force is applied to the force detection element 6 based on the displacement. When compressive force is transmitted to the force detection element 6, the electric resistance value of the force detection element 6 changes due to the piezoresistance effect, and the output value of the force detection element 6 changes. This change in output value is provided to an external circuit via wiring (not shown) and used for necessary processing.

Hereinafter, features and modifications of the pressure sensor 1A will be described.
(1) In the pressure sensor 1 </ b> A, the elastic seal member 4 prevents a deposit (soot) generated by combustion from entering between the pressure receiving rod 3 and the housing 2. The elastic seal member 4 prevents the deposit (gutter) from diffusing to the rear end side in the housing 2. In particular, the pressure sensor 1 </ b> A is characterized in that the seal load applied to the elastic seal member 4 can be adjusted by a compressive load acting between the first fixing member 5 and the stepped surface of the housing 2. For this reason, the seal load applied to the elastic seal member 4 is not affected by manufacturing variations in the design dimensions of each member. In the pressure sensor 1A, the reliability of the seal structure is high.

(2) In the pressure sensor 1A, it is possible to adjust the seal load applied to the elastic seal member 4 by pressing the first fixing member 5, and further pressing the second fixing member 7 to the force detection element 6. The preload to be applied can be adjusted. For this reason, the seal load and the preload can be adjusted to different sizes. As a result, the pressure sensor 1A can achieve both the reliability of the seal structure and the pressure detection sensitivity.

(3) The pressure sensor 1A is characterized in that the jaw portion 3a of the pressure receiving rod 3 and the stepped surface of the housing 2 are in contact with each other, and a load is also applied to this contact portion. For this reason, the deposit (soot) generated by combustion is prevented from entering even at the contact portion. For this reason, it is suppressed that the elastic seal member 4 is directly exposed to the deposit (煤), and the durability of the elastic seal member 4 is improved. That is, in the pressure sensor 1A, a double seal structure is configured, and the reliability of the seal structure is high.

(4) The pressure sensor 1A is characterized in that a metal C ring is used for the elastic seal member 4 and the seal opening portion faces the high pressure side. For this reason, the sealing performance of the elastic seal member 4 is high.

(5) The pressure sensor 1A is characterized in that the elastic seal member 4 is provided between the jaw portion 3a of the pressure receiving rod 3 and the first fixing member 5. Since the spring constant of the elastic seal member 4 is small, most of the combustion pressure applied to the pressure receiving rod 3 is transmitted to the force detection element 6. The pressure sensor 1A can achieve both high sealing performance and high pressure detection sensitivity.

(6) The pressure sensor 1B of the modified example shown in FIG. 3 is characterized in that the jaw 3a of the pressure receiving rod 3 and the stepped surface of the housing 2 are processed into a tapered shape. In this case, the pressure receiving rod 3 can be easily accommodated in a predetermined position in the housing 2.

(7) The pressure sensor 1 </ b> C of the modification shown in FIG. 4 is characterized in that the elastic seal member 14 is provided between the jaw portion 3 a of the pressure receiving rod 3 and the stepped surface of the housing 2. In this case, the seal opening of the elastic seal member 14 faces inward (that is, the high pressure side). For this reason, the sealing performance of the elastic seal member 14 is high.

(8) The pressure sensor 1D of the modification shown in FIG. 5 is characterized in that two elastic seal members 4 and 14 are provided above and below the pressure receiving rod 3. In this case, both of the features of the elastic seal members 4 and 14 described above can be provided.

(9) In each of the pressure sensors 1A, 1B, 1C, 1D, the first fixing member 5 and the second fixing member 7 are fixed by welding, but instead of this example, screwing, caulking, press fitting, adhesion Or the like.

  As mentioned above, although the specific example of this application was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

1A, 1B, 1C, 1D: Pressure sensor 2: Housing 2a: First cylindrical portion 2b: Second cylindrical portion 3: Pressure receiving rod 3a: Jaw portion 4, 14: Elastic seal member 5: First fixing member 6: Force detection Element 7: second fixing member

Claims (4)

A hollow housing having an inner peripheral surface including a stepped surface and having at least one end opened;
A pressure receiving rod disposed in the housing, with one end surface exposed at the one end portion of the housing, and a jaw portion facing the step surface of the housing in the axial direction provided on the outer peripheral surface;
A force detection element facing the other end face of the pressure receiving rod;
A first fixing member fixed to the housing and facing the stepped surface of the housing through the jaw portion of the pressure receiving rod in the axial direction;
Equipped with an elastic sealing member provided between the jaw of the front Symbol pressure receiving rod the first fixing member,
The jaw portion of the pressure receiving rod is in contact with the stepped surface of the housing;
A pressure sensor in which a seal load is applied to the elastic seal member by a compressive load acting between the first fixing member and the stepped surface of the housing. The pressure sensor according to claim 1, wherein the jaw portion of the pressure receiving rod and the stepped surface of the housing are processed into a tapered shape. A through hole is formed in the first fixing member,
The pressure sensor according to claim 1, wherein the pressure receiving rod is disposed so as to pass through the through hole of the first fixing member. A second fixing member fixed to the housing and facing the other end face of the pressure receiving rod via the force detection element in the axial direction;
The pressure sensor according to claim 3, wherein a preload is applied to the force detection element by a compressive load acting between the second fixing member and the pressure receiving rod.

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