JP6855367B2 - In-cylinder pressure sensor - Google Patents

Description

The present invention relates to an in-cylinder pressure sensor that detects the pressure in the combustion chamber of an internal combustion engine.

As an in-cylinder pressure sensor mounted on an internal combustion engine, a tubular housing extending in the axial direction, a diaphragm welded to the housing to close the opening of the housing, and a pressure receiving force that displaces in the axial direction according to the amount of deflection of the diaphragm. A rod is known to include a rod and a detection element for detecting the displacement of the pressure receiving rod (Patent Document 1). In the technique disclosed in Patent Document 1, the heat receiving portion is connected to the surface on the tip end side of the diaphragm. Since the heat receiving unit makes it difficult to transfer the heat of the combustion gas to the diaphragm, the thermal expansion of the diaphragm is suppressed. As a result, it is difficult to input the load due to the thermal expansion of the diaphragm to the detection element other than the load due to the deflection of the diaphragm according to the in-cylinder pressure, so that the pressure detection accuracy can be improved.

Japanese Unexamined Patent Publication No. 2017-40516

However, the above technology is required to further improve the pressure detection accuracy.

The present invention has been made in order to meet this demand, and an object of the present invention is to provide an in-cylinder pressure sensor capable of improving pressure detection accuracy.

In order to achieve this object, the in-cylinder pressure sensor of the present invention closes a tubular housing extending in the axial direction from the front end side to the rear end side and an opening on the front end side of the housing, and receives pressure from the front end side. It is provided with a diaphragm that bends according to the above, a pressure receiving rod that is connected to the diaphragm and is displaced in the axial direction according to the amount of bending of the diaphragm, and a detection element that detects the displacement of the pressure receiving rod. The diaphragm and the pressure receiving rod are integrally formed, and the diaphragm is provided with a press-fitting portion that contacts the inner peripheral surface of the housing.

Further, the in-cylinder pressure sensor of the present invention closes a tubular housing extending in the axial direction from the front end side to the rear end side and an opening on the front end side of the housing, and bends according to the pressure received from the front end side. It includes a diaphragm, a pressure receiving rod connected to the diaphragm and displaced in the axial direction according to the amount of deflection of the diaphragm, and a detection element for detecting the displacement of the pressure receiving rod. The diaphragm and the housing are integrally formed, the diaphragm is formed with a hole from the rear end surface to the tip end side, and the pressure receiving rod is provided with a press-fitting portion that contacts the inner peripheral surface of the diaphragm.

According to the in-cylinder pressure sensor according to claim 1, since the diaphragm integrally formed with the pressure receiving rod is joined to the inner peripheral surface of the housing by press fitting, the combustion gas is compared with the case where the diaphragm is welded to the housing. When the diaphragm is thermally expanded by receiving the heat of the above, the housing can make it difficult for the housing to restrain the press-fitted portion of the diaphragm. As a result, the stress of the diaphragm due to the restraint of the housing can be reduced, so that it is difficult to input the load due to the thermal expansion of the diaphragm to the detection element other than the load due to the deflection of the diaphragm according to the in-cylinder pressure. Therefore, the pressure detection accuracy can be improved.
The housing has a reduced inner diameter portion whose inner diameter is reduced from the front end side to the rear end side, and the press-fitted portion is reduced in diameter from the front end side to the rear end side. Since the press-fitting portion is in contact with the inner peripheral surface of the housing in the reduced inner diameter portion, it is possible to make it more difficult for the housing to restrain the press-fitting portion of the diaphragm when the diaphragm is thermally expanded. Therefore, the pressure detection accuracy can be further improved.

According to the in-cylinder pressure sensor according to claim 2, the diaphragm integrally formed with the housing has a hole formed from the rear end surface to the tip end side, and the pressure receiving rod is joined to the inner peripheral surface of the diaphragm by press fitting. Therefore, as compared with the case where the pressure receiving rod is welded to the diaphragm, when the diaphragm is thermally expanded by receiving the heat of the combustion gas, the press-fitting portion of the pressure receiving rod can make it difficult to restrain the diaphragm. As a result, the stress of the diaphragm due to the restraint of the pressure receiving rod can be reduced, so that it is difficult to input the load due to the thermal expansion of the diaphragm to the detection element other than the load due to the deflection of the diaphragm according to the in-cylinder pressure. Therefore, the pressure detection accuracy can be improved.

According to the in-cylinder pressure sensor according to claim 3 , the diaphragm has an enlarged inner diameter portion whose inner diameter increases from the front end side to the rear end side, and the press-fitting portion has its own outer diameter from the front end side to the rear end side. The diameter increases toward. Since the press-fitting portion is in contact with the inner peripheral surface of the diaphragm in the inner diameter expanding portion, it is possible to make it more difficult for the diaphragm to restrain the press-fitting portion of the pressure receiving rod when the diaphragm is thermally expanded. Therefore, in addition to the effect of claim 2, the pressure detection accuracy can be further improved.

According to the in-cylinder pressure sensor according to claim 4 , the tip of the pressure receiving rod exists at the same position as the tip of the housing or on the rear end side of the tip of the housing in the axial direction. As a result, the pressure receiving rod is less likely to be affected by the heat of the combustion gas, so that the temperature rise of the detection element due to heat conduction from the pressure receiving rod to the detection element can be suppressed. As a result, in addition to the effect of any one of claims 1 to 3 , it is possible to suppress a decrease in detection accuracy due to an increase in the temperature of the detection element.

It is sectional drawing of the tip side of the in-cylinder pressure sensor in 1st Embodiment of this invention. It is a partially enlarged view of the in-cylinder pressure sensor which illustrated the part shown by II of FIG. (A) is a cross-sectional view of the in-cylinder pressure sensor in the second embodiment, (b) is a cross-sectional view of the in-cylinder pressure sensor in the third embodiment, and (c) is an in-cylinder pressure in the fourth embodiment. It is sectional drawing of a sensor. It is sectional drawing of the tip side of the in-cylinder pressure sensor in 5th Embodiment. It is a partially enlarged view of the in-cylinder pressure sensor which illustrated the part shown by V of FIG. It is sectional drawing of the in-cylinder pressure sensor in 6th Embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of the tip end side of the in-cylinder pressure sensor 10 including the axis O according to the first embodiment of the present invention, and FIG. 2 is an enlarged view of the portion shown by II in FIG. It is a partially enlarged view. In FIGS. 1 and 2, the lower side of the paper surface is referred to as the front end side of the in-cylinder pressure sensor 10, and the upper side of the paper surface is referred to as the rear end side of the in-cylinder pressure sensor 10 (the same applies to FIGS. 3 to 6). In FIG. 1, the rear end side of the in-cylinder pressure sensor 10 is not shown. As shown in FIG. 1, the in-cylinder pressure sensor 10 includes a housing 20, a diaphragm 23, a pressure receiving rod 30, and a sensor unit 40.

The housing 20 is a cylindrical member made of a metal material having heat resistance or gas resistance (for example, stainless steel or the like). In the present embodiment, the first part 21 and the second part 22 are joined in order from the rear end side to the tip end side in the axis O direction to form the housing 20.

The first portion 21 is a cylindrical member provided with a screw and a tool engaging portion (neither of which is shown) on the outer peripheral surface on the rear end side. The screw of the first part 21 is a portion where the in-cylinder pressure sensor 10 is engaged with a screw hole of an internal combustion engine (not shown). The tool engaging portion is a portion for engaging a tool such as a wrench when tightening a screw into a screw hole of an internal combustion engine.

The second part 22 is a cylindrical member in which a female thread is formed on the inner peripheral surface on the rear end side. The sensor unit 40 is arranged inside the second unit 22. The diaphragm 23 projects inward in the radial direction from the inner peripheral surface of the second portion 22 on the tip 22a side. The diaphragm 23 is an annular film, and is provided over the entire circumference of the inner peripheral surface of the second part 22. In the present embodiment, the second part 22 and the diaphragm 23 are integrally formed by, for example, forging or cutting, using a metal material such as stainless steel. However, the present invention is not limited to this, and it is naturally possible to integrate the second portion 22 and the diaphragm 23 by welding or the like after forming the second portion 22 and the diaphragm 23 separately.

As shown in FIG. 2, the diaphragm 23 has a hole formed in the center from the rear end surface 24 to the front end surface 25 of the diaphragm 23. By forming a hole in the diaphragm 23, a conical surface-shaped enlarged inner diameter portion 26 whose inner diameter of the diaphragm 23 increases from the front end side to the rear end side is provided on the inner peripheral surface of the diaphragm 23.

The pressure receiving rod 30 is a columnar member arranged inside the second portion 22. Since the pressure receiving rod 30 is also used as a part of the energizing path, it is made of a conductive metal. The pressure receiving rod 30 is exposed without its tip surface 31 being covered by the diaphragm 23. In the present embodiment, the tip surface 31 of the pressure receiving rod 30 exists at the same position as the tip 22a of the housing 20 (second part 22) in the axis O direction.

The press-fitting portion 32 of the pressure receiving rod 30 is press-fitted into the expanding inner diameter portion 26 of the diaphragm 23. The press-fitting portion 32 is a conical surface portion adjacent to the tip surface 31, and the diameter is reduced from the rear end side to the tip side. By press-fitting the press-fitting portion 32 into the inner diameter expanding portion 26 and joining the press-fitting portion 32 to the expanding inner diameter portion 26, the airtightness of the pressure receiving rod 30 with respect to the diaphragm 23 can be ensured. In the cross section of the in-cylinder pressure sensor 10 cut on a plane (cutting surface) that passes through the press-fitting portion 32 and is perpendicular to the axis O, the entire circumference of the press-fitting portion 32 is the inner peripheral surface of the inner diameter portion 26 (diaphragm 23). ) Is in contact.

As shown in FIG. 2, when the press-fitting portion 32 is press-fitted into the inner diameter expanding portion 26 (see FIG. 1), plastic deformation or elastic deformation occurs in at least one of the press-fitting portion 32 and the expanding inner diameter portion 26. The press-fitting portion 32 press-fitted into the expanding inner diameter portion 26 receives a reaction force from the expanding inner diameter portion 26 toward the inside in the radial direction. The press-fitting portion 32 is held (joined) by the expanding inner diameter portion 26 by a frictional force corresponding to the reaction force. In the present embodiment, the angle θ1 of the press-fitting portion 32 with respect to the axis O is larger than the angle θ2 of the enlarged inner diameter portion 26 with respect to the axis O. As a result, the rear end side portion of the press-fitting portion 32 can be brought into close contact with the expanding inner diameter portion 26, so that the airtightness of the press-fitting portion 32 can be improved. The pressure receiving rod 30 in which the press-fitting portion 32 is joined to the expanding inner diameter portion 26 of the diaphragm 23 is displaced in the axis O direction according to the amount of bending of the diaphragm 23 according to the in-cylinder pressure.

It will be described back to FIG. The sensor unit 40 is arranged on the rear end side of the pressure receiving rod 30 in the axis O direction, and is sandwiched between the pressure receiving rod 30 and the bolt 50. The bolt 50 is a metal member having a through hole formed in the axis O direction, and is screwed into the second portion 22. The bolt 50 is a member that gives a preload to the sensor unit 40 in the axis O direction. The cable 51 arranged inside the first part 21 is connected to an electric circuit (not shown) that detects the pressure based on the output of the sensor part 40.

In the sensor unit 40, a pressing plate 44, an electrode 42, a detection element 41, an electrode 43, a terminal portion 45, a pressing plate 46, and an insulating plate 47 are laminated in this order from the front end side to the rear end side in the axis O direction. The terminal portion 45 electrically connected to the electrode 43 is insulated from the housing 20. A part of the terminal portion 45 enters the inside of the through hole of the bolt 50 and is connected to the inner conductor 52 of the cable 51. The outer conductor 53 (shield) of the cable 51 insulated from the inner conductor 52 is connected to the bolt 50. The electrode 42 is electrically connected to the second portion 22 (housing 20) through the pressing plate 44, the pressure receiving rod 30, and the diaphragm 23.

The detection element 41 generates an output value according to the load transmitted through the pressure receiving rod 30. The detection element 41 outputs an output value (for example, an electric signal) according to the load through the electrodes 42 and 43 and the terminal portion 45. The displacement of the pressure receiving rod 30, that is, the in-cylinder pressure can be detected based on the electric signal output to the electric circuit (not shown) through the cable 51. In the present embodiment, the detection element 41 uses a piezoelectric element (semiconductor pressure sensor) that utilizes the piezoresistive effect.

The in-cylinder pressure sensor 10 is manufactured by, for example, the following method. First, the pressure receiving rod 30 is inserted from the rear end side of the second portion 22 to the inside of the second portion 22, and then the press-fitting portion 32 of the pressure receiving rod 30 is press-fitted into the inner peripheral surface (inner diameter expanding portion 26) of the diaphragm 23. As a result, the pressure receiving rod 30 is held by the diaphragm 23.

Next, after inserting the sensor unit 40 into the second part 22 from the rear end side, the bolt 50 is screwed into the second part 22 from the rear end side, and the sensor unit 40 is inserted between the bolt 50 and the pressure receiving rod 30. Deploy. Next, the bolt 50 is rotated with respect to the second portion 22, and a compressive load in the axial direction O direction is applied to the sensor portion 40.

After connecting the cable 51 to the terminal portion 45 and the bolt 50, the cable 51 is inserted into the first portion 21. After welding the first part 21 and the second part 22, an insulator (not shown) such as softened rubber or synthetic resin is injected into the inside of the first part 21. When the injected insulator is cured, the in-cylinder pressure sensor 10 that ensures waterproofness and vibration isolation can be obtained.

In the in-cylinder pressure sensor 10, the pressure receiving rod 30 in which the press-fitting portion 32 is joined to the expanding inner diameter portion 26 of the diaphragm 23 is displaced in the axis O direction according to the in-cylinder pressure received by the diaphragm 23. Then, a compressive force is applied to the detection element 41 based on the displacement, and the resistance value of the detection element 41 changes due to the piezoresistive effect. If the energization path of the detection element 41 of the in-cylinder pressure sensor 10 is a constant current circuit, the voltage value of the energization path changes according to the in-cylinder pressure. The in-cylinder pressure can be detected by performing the necessary processing.

At this time, when the diaphragm 23 is thermally expanded by the high-temperature combustion gas, the diaphragm 23 extends inward in the radial direction, and the inner peripheral side of the diaphragm 23 tends to warp toward the tip side (lower side in FIG. 1) due to the reaction force. At this time, the diaphragm 23 can apply a force to the press-fitting portion 32 of the pressure receiving rod 30 toward the tip end side (lower side in FIG. 1) in the axis O direction. This force cancels out the displacement of the pressure receiving rod 30 toward the rear end side according to the in-cylinder pressure, and causes a decrease in pressure detection accuracy.

However, since the press-fitting portion 32 of the pressure receiving rod 30 press-fitted into the expanding inner diameter portion 26 of the diaphragm 23 is only in contact with the expanding inner diameter portion 26, compared with the case where the pressure receiving rod 30 is joined to the diaphragm 23 by welding. , The press-fitting portion 32 of the pressure receiving rod 30 can make it difficult to restrain the diaphragm 23. As a result, the stress of the diaphragm 23 due to the restraint of the pressure receiving rod 30 can be reduced, so that the load due to the thermal expansion of the diaphragm 23 other than the load due to the displacement of the pressure receiving rod 30 according to the deflection of the diaphragm according to the in-cylinder pressure is detected. It can be difficult to input to 41. Therefore, the pressure detection accuracy can be improved.

Further, since the press-fitting portion 32 of the pressure receiving rod 30 is in contact with the inner peripheral surface of the diaphragm 23 in the inner diameter expanding portion 26, when the diaphragm 23 thermally expands and tries to extend inward in the radial direction, the press-fitting portion 32 On the other hand, the enlarged inner diameter portion 26 can be easily escaped toward the tip side (lower side in FIG. 1) in the axis O direction. As a result, the stress of the diaphragm 23 due to the restraint of the pressure receiving rod 30 can be further reduced, so that the pressure detection accuracy can be further improved.

The tip surface 31 of the pressure receiving rod 30 exists at the same position as the tip 22a of the housing 20 in the axis O direction. As a result, since the pressure receiving rod 30 can be made less susceptible to the heat of the combustion gas by the housing 20, the temperature rise of the detection element 41 due to heat conduction from the pressure receiving rod 30 to the detection element 41 can be suppressed. Therefore, it is possible to suppress a decrease in detection accuracy due to an increase in the temperature of the detection element 41.

Next, the second to fourth embodiments will be described with reference to FIG. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 3A is a cross-sectional view including the axis O of the in-cylinder pressure sensor 60 in the second embodiment, and FIG. 3B is a cross-sectional view including the axis O of the in-cylinder pressure sensor 70 in the third embodiment. FIG. 3C is a cross-sectional view including the axis O of the in-cylinder pressure sensor 80 according to the fourth embodiment. 3 (a) to 3 (c) show the vicinity of the tips of the in-cylinder pressure sensors 60, 70, 80.

As shown in FIG. 3A, the in-cylinder pressure sensor 60 includes a second part 22 (housing 20), a diaphragm 61, and a pressure receiving rod 66. A sensor unit 40 (see FIG. 1) is arranged at the rear end of the pressure receiving rod 66. The diaphragm 61 is an annular portion that protrudes inward in the radial direction from the inner peripheral surface of the second portion 22 on the tip 22a side. The diaphragm 61 is provided over the entire circumference of the inner peripheral surface of the second part 22. The diaphragm 61 has a hole formed in the center from the rear end surface 62 to the front end surface 63 of the diaphragm 61. A conical surface-shaped enlarged inner diameter portion 65 whose inner diameter increases from the front end side to the rear end side is formed on a part of the inner peripheral surface 64 of the diaphragm 61. The enlarged inner diameter portion 65 communicates with the rear end surface 62 of the diaphragm 61.

The pressure receiving rod 66 is a columnar metal member, and the tip surface 67 of the pressure receiving rod 66 (the surface on the tip side of the press fitting portion 68) is arranged inside the inner peripheral surface 64 of the diaphragm 61. In the present embodiment, the tip surface 67 of the pressure receiving rod 66 exists on the rear end side of the position of the tip 22a of the housing 20 (second part 22) in the axis O direction. As a result, since the pressure receiving rod 66 can be made less susceptible to the heat of the combustion gas by the housing 20, the temperature rise of the detection element 41 due to heat conduction from the pressure receiving rod 66 to the detection element 41 can be suppressed. Therefore, it is possible to suppress a decrease in detection accuracy due to an increase in the temperature of the detection element 41.

The press-fitting portion 68 of the pressure receiving rod 66 is press-fitted into the expanding inner diameter portion 65 of the diaphragm 61. The press-fitting portion 68 is a conical surface portion adjacent to the tip surface 67, and the diameter is reduced from the rear end side to the tip side. The pressure receiving rod 66 to which the press-fitting portion 68 is joined to the expanding inner diameter portion 65 of the diaphragm 61 is displaced in the axis O direction according to the amount of bending of the diaphragm 61 according to the in-cylinder pressure. The in-cylinder pressure sensor 60 in the second embodiment can realize the same action and effect as the in-cylinder pressure sensor 10 in the first embodiment.

As shown in FIG. 3B, the in-cylinder pressure sensor 70 includes a second part 22 (housing 20), a diaphragm 71, and a pressure receiving rod 76. A sensor unit 40 (see FIG. 1) is arranged at the rear end of the pressure receiving rod 76. The diaphragm 71 is an annular portion that protrudes inward in the radial direction from the inner peripheral surface of the second portion 22 on the tip 22a side. The diaphragm 71 has a hole formed in the center from the rear end surface 72 to the front end surface 73 of the diaphragm 71. A conical surface-shaped enlarged inner diameter portion 75 whose inner diameter increases from the front end side to the rear end side is formed on a part of the inner peripheral surface 74 of the diaphragm 71. The enlarged inner diameter portion 75 communicates with the rear end surface 72 of the diaphragm 71.

The pressure receiving rod 76 is a columnar metal member, and the tip surface 77 of the pressure receiving rod 76 is arranged inside the inner peripheral surface 74 of the diaphragm 71. In the present embodiment, the tip surface 77 of the pressure receiving rod 76 exists at the same position as the tip 22a of the housing 20 (second part 22) in the axis O direction.

The press-fitting portion 78 of the pressure receiving rod 76 is press-fitted into the expanding inner diameter portion 75 of the diaphragm 71. The press-fitting portion 78 is a conical surface portion, and the diameter is reduced from the rear end side to the tip side. A cylindrical portion 79 is adjacent to the tip end side of the press-fit portion 78. The cylindrical portion 79 is a cylindrical surface facing the inner peripheral surface 74 of the diaphragm 61. The cylindrical portion 79 connects the tip surface 77 and the press-fit portion 78. The pressure receiving rod 76 in which the press-fitting portion 78 is joined to the expanding inner diameter portion 75 of the diaphragm 71 is displaced in the axis O direction according to the amount of bending of the diaphragm 71 according to the in-cylinder pressure. According to the in-cylinder pressure sensor 70 in the third embodiment, the same operation and effect as in the in-cylinder pressure sensor 10 in the first embodiment can be realized.

As shown in FIG. 3C, the in-cylinder pressure sensor 80 includes a second part 22 (housing 20), a diaphragm 81, and a pressure receiving rod 86. A sensor unit 40 (see FIG. 1) is arranged at the rear end of the pressure receiving rod 86. The diaphragm 81 is an annular portion that protrudes inward in the radial direction from the inner peripheral surface of the second portion 22 on the tip 22a side. The diaphragm 81 has a hole formed in the center from the rear end surface 82 to the front end surface 83 of the diaphragm 81. On the inner peripheral surface of the diaphragm 81, a conical surface-shaped enlarged inner diameter portion 84 whose inner diameter increases from the front end side to the rear end side is provided. The enlarged inner diameter portion 84 connects the rear end surface 82 and the front end surface 83 of the diaphragm 81.

The pressure receiving rod 86 is a columnar metal member, and the tip surface 87 of the pressure receiving rod 86 is arranged inside the inner diameter expanding portion 84 of the diaphragm 81. The tip surface 87 of the pressure receiving rod 86 is a spherical crown-shaped curved surface. In the present embodiment, the tip of the pressure receiving rod 86 (the position on the most tip side of the tip surface 87) exists on the tip side of the housing 20 (second part 22) with respect to the position of the tip 22a in the axis O direction. To do.

The press-fitting portion 88 of the pressure receiving rod 76 is press-fitted into the expanding inner diameter portion 84 of the diaphragm 81. The press-fitting portion 88 is a spherical band-shaped portion, and the diameter is reduced from the rear end side to the tip side. The tip surface 87 is adjacent to the tip side of the press-fitting portion 88. The pressure receiving rod 86 in which the press-fitting portion 88 is joined to the expanding inner diameter portion 84 of the diaphragm 81 is displaced in the axis O direction according to the amount of bending of the diaphragm 71 according to the in-cylinder pressure. The in-cylinder pressure sensor 80 in the fourth embodiment has the same operation as the in-cylinder pressure sensor 10 in the first embodiment, except for the effect due to the positional relationship between the tip surface 87 of the pressure receiving rod 86 and the tip surface 22a of the housing 20. The effect can be realized.

Next, a fifth embodiment will be described with reference to FIGS. 4 and 5. In the first to third embodiments, the press-fitting portions 32, 68, 78, 88 of the pressure receiving rods 30, 66, 76, 86 are press-fitted into the inner peripheral surfaces of the diaphragms 23, 61, 71, 81. The case was explained. On the other hand, in the fifth embodiment, the case where the press-fitting portion 98 of the diaphragm 97 integrally formed with the pressure receiving rod 95 is press-fitted into the inner peripheral surface of the housing 91 will be described. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 4 is a cross-sectional view of the tip end side of the in-cylinder pressure sensor 90 including the axis O in the fifth embodiment, and FIG. 5 is a partially enlarged view of the in-cylinder pressure sensor 90 shown by enlarging the portion shown by V in FIG. Is. As shown in FIG. 4, the in-cylinder pressure sensor 90 includes a housing 91, a pressure receiving rod 95, a diaphragm 97, and a sensor unit 40.

The housing 91 is a cylindrical member made of a metal material having heat resistance or gas resistance (for example, stainless steel or the like). In the present embodiment, the first part 21 and the second part 92 are joined in order from the rear end side to the tip end side in the axis O direction to form the housing 91. The second part 92 is a cylindrical member in which a female thread is formed on the inner peripheral surface on the rear end side. The sensor unit 40 is arranged inside the second unit 92. A reduced inner diameter portion 94 is formed on the inner peripheral surface of the second portion 92 on the tip 93 side. The reduced inner diameter portion 94 is a conical surface portion whose inner diameter is reduced from the front end side to the rear end side.

The pressure receiving rod 95 is a columnar metal (for example, stainless steel) member arranged inside the second part 92. The sensor unit 40 is arranged at the rear end of the pressure receiving rod 95. A diaphragm 97, which is an annular film centered on the axis O, is integrally formed around the tip surface 96 of the pressure receiving rod 95. In the present embodiment, the diaphragm 97 is integrally formed with the pressure receiving rod 95 by means such as forging or cutting. However, the present invention is not limited to this, and it is naturally possible to integrate the pressure receiving rod 95 and the diaphragm 97 by welding or the like after forming the pressure receiving rod 95 and the diaphragm 97 separately.

A press-fitting portion 98 that contacts the reduced inner diameter portion 94 of the second portion 92 (housing 91) is provided on the peripheral edge of the diaphragm 97. The outer diameter of the press-fitting portion 98 is reduced from the front end side to the rear end side. The press-fitting portion 98 is press-fitted into the reduced inner diameter portion 94 of the second portion 92. By press-fitting the press-fitting portion 98 into the shrinking inner diameter portion 94 and joining the press-fitting portion 98 to the shrinking inner diameter portion 94, the airtightness of the diaphragm 97 with respect to the second part 92 can be ensured. The position of the tip surface 96 of the pressure receiving rod 95 exists on the rear end side of the tip 93 of the housing 91 in the axis O direction. The pressure receiving rod 95 is displaced in the axis O direction according to the amount of deflection of the diaphragm 97 according to the in-cylinder pressure.

As shown in FIG. 5, when the press-fitting portion 98 is press-fitted into the shrinkage inner diameter portion 94, plastic deformation or elastic deformation occurs in at least one of the press-fitting portion 98 and the shrinkage inner diameter portion 94. In the present embodiment, the angle θ1 of the press-fitting portion 98 with respect to the axis O is smaller than the angle θ2 of the reduced inner diameter portion 94 with respect to the axis O. As a result, the rear end side portion of the press-fitting portion 98 can be brought into close contact with the reduced inner diameter portion 94, so that the airtightness of the press-fitting portion 98 can be improved.

It will be described back to FIG. The in-cylinder pressure sensor 90 is manufactured by, for example, the following method. First, the pressure receiving rod 95 is inserted from the tip end side of the second part 92 to the inside of the second part 92, and the press-fit portion 98 of the diaphragm 97 is press-fitted into the reduced inner diameter portion 94 of the second part 92. As a result, the pressure receiving rod 95 and the diaphragm 97 are held by the second part 92.

Next, after inserting the sensor unit 40 from the rear end side into the second part 92, the bolt 50 is screwed into the second part 22 from the rear end side, and the sensor unit 40 is inserted between the bolt 50 and the pressure receiving rod 95. Deploy. Next, the bolt 50 is rotated with respect to the second portion 22, and a compressive load in the axial direction O direction is applied to the sensor portion 40.

After connecting the cable 51 to the terminal portion 45 and the bolt 50, the cable 51 is inserted into the first portion 21. After welding the first part 21 and the second part 92, an insulator (not shown) such as softened rubber or synthetic resin is injected into the inside of the first part 21. When the injected insulator is cured, the in-cylinder pressure sensor 90 that ensures waterproofness and vibration isolation can be obtained.

In the in-cylinder pressure sensor 90, the pressure receiving rod 95 is displaced in the axis O direction according to the amount of deflection of the diaphragm 97 in which the press-fitting portion 98 is in contact with the reduced inner diameter portion 94 of the second portion 92. Then, a compressive force is applied to the detection element 41 based on the displacement, and the resistance value of the detection element 41 changes due to the piezoresistive effect. If the energization path of the detection element 41 of the in-cylinder pressure sensor 90 is a constant current circuit, the voltage value of the energization path changes according to the in-cylinder pressure. The in-cylinder pressure can be detected by performing the necessary processing.

At this time, when the diaphragm 97 is thermally expanded by the high-temperature combustion gas, the diaphragm 97 extends outward in the radial direction, and the outer peripheral side of the diaphragm 97 tends to warp toward the tip side (lower side in FIG. 5) due to the reaction force. At this time, the diaphragm 97 can apply a force to the pressure receiving rod 95 toward the rear end side (upper side in FIG. 5) in the axis O direction. This force is synergistic with the displacement of the pressure receiving rod 95 toward the rear end side according to the in-cylinder pressure, which causes a decrease in pressure detection accuracy.

However, since the press-fitted portion 98 of the diaphragm 97 press-fitted into the reduced inner diameter portion 94 of the second portion 92 (housing 91) is only in contact with the reduced inner diameter portion 94, the diaphragm 97 is welded to the second portion 92. The housing 91 can make it difficult for the housing 91 to restrain the press-fitting portion 98 of the diaphragm 97 as compared with the case where it is joined. As a result, the stress of the diaphragm 97 due to the restraint of the housing 91 can be reduced, so that it is difficult to input the load due to the thermal expansion of the diaphragm 97 to the detection element 41 other than the load due to the deflection of the diaphragm 97 according to the in-cylinder pressure. Therefore, the pressure detection accuracy can be improved.

Further, since the press-fitting portion 98 of the diaphragm 97 is in contact with the inner peripheral surface of the second portion 92 (housing 91) in the reduced inner diameter portion 94, the diaphragm 97 thermally expands and the press-fitting portion 98 moves outward in the radial direction. When trying to extend, the press-fitting portion 98 can be easily escaped to the tip side (lower side in FIG. 4) in the axis O direction with respect to the reduced inner diameter portion 94. As a result, the stress of the diaphragm 97 due to the restraint of the housing 91 can be further suppressed, so that the pressure detection accuracy can be further improved.

The tip surface 96 of the pressure receiving rod 95 exists on the rear end side of the position of the tip 93 of the housing 91 in the axis O direction. As a result, since the pressure receiving rod 95 can be made less susceptible to the heat of the combustion gas by the housing 91, the temperature rise of the detection element 41 due to heat conduction from the pressure receiving rod 95 to the detection element 41 can be suppressed. Therefore, it is possible to suppress a decrease in detection accuracy due to an increase in the temperature of the detection element 41.

Next, a sixth embodiment will be described with reference to FIG. The same parts as those in the first embodiment and the fifth embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 6 is a cross-sectional view including the axis O of the in-cylinder pressure sensor 100 according to the sixth embodiment. In FIG. 6, the rear end side of the in-cylinder pressure sensor 100 is not shown. As shown in FIG. 6, the in-cylinder pressure sensor 100 includes a housing 101, a pressure receiving rod 95, a diaphragm 97, and a sensor unit 40.

The housing 101 is a cylindrical member made of a metal material having heat resistance or gas resistance (for example, stainless steel or the like). In the present embodiment, the first part 21 and the second part 92 are joined in order from the rear end side to the tip end side in the axis O direction to form the housing 101. An annular overhanging portion 102 that projects inward in the radial direction is provided on the inner peripheral surface of the second portion 92 on the tip 93 side. A conical reduced inner diameter portion 103 whose inner diameter is reduced from the front end side to the rear end side is formed on the inner peripheral surface of the overhanging portion 102.

A diaphragm 104, which is an annular film centered on the axis O, is integrally formed around the tip surface 96 of the pressure receiving rod 95. A press-fitting portion 105 that contacts the reduced inner diameter portion 103 of the overhanging portion 102 (housing 101) is provided on the peripheral edge of the diaphragm 104. The outer diameter of the press-fitting portion 105 is reduced from the front end side to the rear end side. The press-fitting portion 105 is press-fitted into the reduced inner diameter portion 103. According to the sixth embodiment, the same operation and effect as the in-cylinder pressure sensor 90 in the fifth embodiment can be realized. Further, according to the in-cylinder pressure sensor 90, the area of the diaphragm 104 can be adjusted and the amount of bending of the diaphragm 104 can be adjusted by adjusting the length of the overhanging portion 102 in the radial direction.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily inferred. For example, the shapes of the diaphragms 23, 61, 71, 81 and the pressure receiving rods 30, 66, 76, 86 are examples and can be set as appropriate.

In the embodiment, the case where the piezoelectric element (semiconductor pressure sensor) utilizing the piezoresistive effect is used as the detection element 41 has been described, but the present invention is not necessarily limited to this. As the detection element 41, it is naturally possible to use a piezoelectric element that utilizes the piezoelectric effect (piezoelectric effect). Further, various elements having electrical characteristics (for example, voltage, resistance value, etc.) that change according to the load from the pressure receiving rods 30, 66, 76, 86, 95 can be adopted. Examples of such an element include a strain gauge.

In the embodiment, the case where the displacement of the pressure receiving rods 30, 66, 76, 86, 95 is directly transmitted to the sensor unit 40 has been described, but the present invention is not necessarily limited to this. It is natural that the displacement of the pressure receiving rods 30, 66, 76, 86, 95 is transmitted to the sensor unit 40 by interposing another member between the pressure receiving rods 30, 66, 76, 86, 95 and the sensor unit 40. It is possible.

Although the description is omitted in the embodiment, the heat of the combustion gas is received by the tips of the housings 20, 91, 101, the diaphragms 23, 61, 71, 81, and the pressure receiving rods 30, 66, 76, 86, 95. Of course, it is possible to arrange the heat receiving member. By arranging the heat receiving members, the amount of thermal deformation of the housings 20, 91, 101, the diaphragms 23, 61, 71, 81, and the diaphragms 97, 104 can be reduced, so that the pressure detection accuracy can be further improved accordingly.

In the first to fourth embodiments, when the positions of the tip surfaces 25, 63, 73, 83 of the diaphragms 23, 61, 71, 81 are at the same positions as the tip 22a of the housing 20 in the axis O direction. However, it is not necessarily limited to this. Of course, it is possible to provide the diaphragms 23, 61, 71, 81 so that the tip surfaces 25, 63, 73, 83 of the diaphragms 23, 61, 71, 81 are located on the rear end side of the tip 22a of the housing 20. Is. By doing so, a part of the tip 22a side of the housing 20 protrudes toward the tip side from the diaphragms 23, 61, 71, 81 over the entire circumference, so that the housing 20 causes the diaphragms 23, 61, 71. , 81 can be protected.

In addition, each embodiment is added by adding a part or a plurality of parts of the configuration of another embodiment to the embodiment or exchanging with a part or a plurality of parts of the configuration of the embodiment. The embodiment may be modified to form the configuration. For example, it is naturally possible that the position of the tip surface 67 of the pressure receiving rod 66 of the in-cylinder pressure sensor 60 in the second embodiment in the axis O direction is the same as the tip 22a of the housing 20 as in the first embodiment. is there. Similarly, the position of the tip end surface 87 of the pressure receiving rod 86 of the in-cylinder pressure sensor 80 in the fourth embodiment in the axial direction O direction is set to the same position as the tip end 22a of the housing 20 as in the first embodiment. Of course, it is possible to set the housing 20 on the rear end side of the front end 22a as in the second embodiment.

10,60,70,80,90,100 In-cylinder pressure sensor 20,91,101 Housing 22a Tip of housing 23,61,71,81 Diaphragm 26,65,75,84 Expanded inner diameter 30,66,76, 86 Pressure receiving rod 31, 67, 77, 87 Tip surface (tip of pressure receiving rod)
32, 68, 78, 88 Press-fitting part 41 Detection element 93 Tip of housing 94,103 Reduced inner diameter part 95 Pressure receiving rod 96 Tip surface (tip of pressure receiving rod)
97,104 Diaphragm 98,105 Press-fitting part

Claims (4)

A tubular housing that extends in the axial direction from the front end side to the rear end side,
A diaphragm that closes the opening on the tip side of the housing and bends according to the pressure received from the tip side.
A pressure receiving rod that is connected to the diaphragm and is displaced in the axial direction according to the amount of deflection of the diaphragm.
An in-cylinder pressure sensor including a detection element for detecting the displacement of the pressure receiving rod.
The diaphragm and the pressure receiving rod are integrally formed.
The diaphragm includes a press-fitting portion that contacts the inner peripheral surface of the housing .
The outer diameter of the press-fitting portion is reduced from the front end side to the rear end side.
The housing has a reduced inner diameter portion whose inner diameter is reduced from the front end side to the rear end side.
The press-fitting portion is an in-cylinder pressure sensor in contact with the inner peripheral surface of the housing in the reduced inner diameter portion. A tubular housing that extends in the axial direction from the front end side to the rear end side,
A diaphragm that closes the opening on the tip side of the housing and bends according to the pressure received from the tip side.
A pressure receiving rod that is connected to the diaphragm and is displaced in the axial direction according to the amount of deflection of the diaphragm.
An in-cylinder pressure sensor including a detection element for detecting the displacement of the pressure receiving rod.
The diaphragm and the housing are integrally formed.
The diaphragm has a hole formed from the rear end surface to the tip side.
The pressure receiving rod is an in-cylinder pressure sensor including a press-fitting portion that contacts the inner peripheral surface of the diaphragm. The outer diameter of the press-fitting portion increases from the front end side to the rear end side.
The diaphragm has an enlarged inner diameter portion whose inner diameter increases from the front end side to the rear end side.
The in-cylinder pressure sensor according to claim 2, wherein the press-fitting portion is in contact with the inner peripheral surface of the diaphragm in the enlarged inner diameter portion. The in-cylinder pressure sensor according to any one of claims 1 to 3 , wherein the tip of the pressure receiving rod is located at the same position as the tip of the housing or on the rear end side of the tip of the housing in the axial direction.

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