Pressure sensor

Abstract

Pressure sensor (1) that detects a combustion pressure of an engine, which contains pressure sensor (1): a contact part (9) which is in direct or indirect contact with a motor housing when the pressure sensor (1) is attached to the motor; and a pressure sensing unit (5) which detects the combustion pressure and outputs a signal corresponding to the combustion pressure, wherein the pressure sensing unit (5) includes a pressure sensing element (5a) which detects the combustion pressure and outputs a signal, and a circuit unit (5b) which converts the signal received from the pressure sensing element (5a) into a signal corresponding to the combustion pressure, and wherein the pressure sensing unit (5) is located at a position further inside the motor than the contact part (9) when the pressure sensor (1) is attached to the motor, wherein the pressure sensor (1) further includes a pressure transmission mechanism (3) which transmits the combustion pressure to the pressure sensing element (5a), wherein at least a part of the pressure transmission mechanism (3) is provided at a location further inside the motor than the circuit unit (5b) when the pressure sensor (1) is attached to the motor, and wherein the pressure transmission mechanism (3) includes a part (3b) providing an element on which the pressure sensing element (5a) is provided, and a part (3c) of high stiffness provided between the part (3b) and the contact part (9) and having a higher stiffness than the part (3b).

Description

Technical area

[0001] The present invention relates to a pressure sensor. State of the art

[0002] A pressure sensor that detects the combustion pressure of an engine is known in the art. Patent 1 describes a pressure sensing plug having a sensor structure in which a measuring sensor and an electronic circuit are mounted, which processes a signal received from the sensor. The sensor structure is arranged at a position close to a combustion chamber of an internal combustion engine, and the electronic circuit is arranged outside the internal combustion engine, away from the sensor structure. Furthermore, US 2009 / 320 576 A1 (cf. Patent 2) discloses a piezoresistive pressure sensing plug for an internal combustion engine, wherein a sensor structure is integrated and arranged in the plug body, and a piezoresistive element is attached to the sensor structure, which is configured to provide a resistance change when a rod arranged in the plug body is moved in the axial direction. JP 2009-128 036 A (cf.PTL 3) discloses a pressure sensor having a special configuration whereby an influence of thermal stress due to different thermal expansion coefficients at a welded joint part between a cap and a metal case is suppressed. State-of-the-art publicationsPatent specifications PTL 1: JP 2014-182127 A PTL 2: US 2009 / 320 576 A1 PTL 3: JP 2009-128 036 A Brief description of the inventionTechnical problem

[0003] Since the pressure gauge according to PTL 1 has the sensor and electronic circuit arranged separately, there is the problem that interference signals from the environment are easily received in a wiring connection of the sensor and the electronic circuit and the detection accuracy is deteriorated. Solution to the problem

[0004] The problem is solved by the features of claim 1. Particular embodiments are described in the dependent claims. Beneficial effects

[0005] According to the invention, a pressure sensor can be provided which is resistant to external noise and has improved detection accuracy. Brief description of the drawings Fig. 1 is an appearance view of a pressure sensor according to an embodiment of the invention. Fig. 2 is an exploded view of the pressure sensor according to the embodiment of the invention. Fig. 3 is a cross-sectional view of the pressure sensor according to the embodiment of the invention. Fig. 4 is a view illustrating a schematic configuration of a pressure detection unit. Fig. 5 is an enlarged cross-sectional view of a pressure sensor according to a first embodiment of the invention. Fig. 6 is a graph illustrating an example of a relationship of a deformation amount of an element forming part and a temperature of a circuit unit with respect to a length L of a voltage receiving part. Fig. 7 is a view illustrating a modification of a contact part. Fig. 8 is an enlarged cross-sectional view of a pressure sensor according to a second embodiment of the invention. Fig. 9 is a schematic view showing a deformed state of the element forming part during pressure absorption in the first embodiment and the second embodiment of the invention. Fig. 10 is an enlarged cross-sectional view of a pressure sensor according to a third embodiment of the invention. Fig. 11 is a schematic view showing a deformed state of the element forming part during pressure absorption in the third embodiment of the invention. Fig. 12 is an enlarged cross-sectional view of a pressure sensor according to a fourth embodiment of the invention. Fig. 13 is a view showing a modification of a heat-conducting material. Description of the embodiments

[0006] Embodiments of the invention will be described below with reference to the drawings. First embodiment

[0007] A pressure sensor according to a first embodiment of the invention will be described with reference to Fig. 1 to Fig. 3 described. Fig. 1 is an appearance view of a pressure sensor according to an embodiment of the invention. Fig. 2 is an exploded view of the pressure sensor according to the embodiment of the invention. Fig. 3 is a cross-sectional view of the pressure sensor according to the embodiment of the invention.

[0008] A pressure sensor 1 is mounted on an engine, which is an internal combustion engine of a vehicle or the like, detects a combustion pressure of the engine, and outputs a sensor output signal corresponding to the combustion pressure to the outside. Fig. 1, the pressure sensor 1 includes a diaphragm 2, a cover 4, a housing 6, and a connecting part 7. The housing 6 is provided with a threaded part 10 configured to attach the pressure sensor 1 to the motor housing, and a contact part 9 that makes contact with the motor housing when the pressure sensor 1 is attached to the motor.

[0009] How Fig. 2 and Fig. 3, a pressure transmission rod 3 and a pressure sensing unit 5 are housed within the cover 4. The pressure sensing unit 5 and the connecting part 7 are connected via a signal line 8.

[0010] The diaphragm 2 is arranged in contact with the pressure transmission rod 3 and the cover 5. With this arrangement, the diaphragm 2 has the function of exerting a compressive force on the pressure transmission rod 3 by absorbing the combustion pressure of the engine and deforming, and the function of preventing combustion gas from the inside of the engine from entering the pressure sensor.

[0011] The pressure sensing unit 5 is provided in the pressure transmission rod 3. The pressure transmission rod 3 acts as a pressure transmission mechanism that transmits the combustion pressure of the engine to the pressure sensing unit 5 by generating a deformation within a range including the standby position of the pressure sensing unit 5 according to the pressing force received from the diaphragm 2. The pressure sensing unit 5 detects the combustion pressure of the engine by detecting the deformation of the pressure transmission rod 3 and outputs a pressure signal corresponding to the detection result to the connector 7 via the signal line 8. The pressure signal is output as a sensor output from the connector 7 to the outside of the pressure sensor 1.A circuit that generates a sensor output by performing signal processing such as output adjustment with respect to the pressure signal obtained from the pressure detecting unit 5 and outputs the sensor output to the outside may be provided in the connecting part 7.

[0012] Fig. 4 is a view illustrating a schematic configuration of the pressure detection unit 5. How Fig. As shown in Fig. 4, in the pressure detection unit 5, a pressure detection element 5a provided, for example, in a central part and a circuit unit 5b provided around the pressure detection element 5a are formed on the same substrate. The pressure detection element 5a is configured using, for example, a strain gauge and detects the combustion pressure of the engine by detecting a deformation amount generated in the pressure transmission rod 3 according to the combustion pressure of the engine. The pressure detection element 5a outputs a signal corresponding to the detected deformation amount, that is, the combustion pressure of the engine, to the circuit unit 5b. The circuit unit 5b performs signal processing on the signal received from the pressure detection element 5a, converts the signal into a pressure signal corresponding to the sensor output, and outputs the pressure signal to the terminal part 7.The circuit unit 5b has the function of performing analog amplification on a weak signal received from the pressure sensing element 5a and the function of converting a weak signal received from the pressure sensing element 5a into a digital signal. Furthermore, the circuit unit 5b can have the function of detecting an ambient temperature and performing temperature correction. Since the pressure sensing element 5a is located near the circuit unit 5b, the temperature correction can be performed on the signal output from the pressure sensing element 5a in the pressure sensing unit 5 using a temperature sensor built into the circuit unit 5b. Therefore, the temperature correction can be realized with a low-cost configuration.

[0013] In the pressure sensor 1 according to the present embodiment, as described above, the pressure sensing element 5a and the circuit unit 5b are formed on the same substrate in the pressure sensing unit 5. Therefore, the wiring length connecting the pressure sensing element 5a and the circuit unit 5b is greatly reduced, and as a result, the influence of external noise can be reduced. Although a configuration in which the pressure sensing element 5a and the circuit unit 5b are formed on the same substrate is illustrated in the present embodiment, they may be arranged separately on separate substrates as long as they are close enough to each other to sufficiently reduce the influence of noise.

[0014] Here, the pressure sensing unit 5 is provided at a location further inside the motor than the contact part 9 when the pressure sensor 1 is mounted on the motor. Since the circuit unit 5b generally has lower heat resistance than the pressure sensing element 5a, a structure capable of sufficiently dissipating heat in the circuit unit 5b is required in the pressure sensor 1, so that the circuit unit 5b can be disposed near the pressure sensing element 5a. In the present embodiment, as described above, a heat dissipation structure of the circuit unit 5b is realized by bringing the contact part 9 into contact with the casing of the motor when the pressure sensor 1 is mounted on the motor. That is,The contact part 9 is arranged near a pressure sensing structure formed by the pressure transmission rod 3 and the pressure sensing unit 5, and has a heat dissipation function for dissipating heat from the pressure sensing structure to the engine casing through thermal contact. Furthermore, the contact part 9 has a shielding function for blocking high-temperature combustion gas inside the engine by coming into close contact with the engine casing and preventing combustion gas from entering a rear end part of the pressure sensor 1, which is located further back than the contact part 9. Since the contact part 9 has these functions, it is possible to prevent a temperature rise of the circuit unit 5b, which has a relatively low heat-resistant temperature.The contact part 9 can only have one of the heat dissipation function and the shielding function if the temperature rise of the circuit unit 5b can be sufficiently suppressed. Furthermore, as long as the heat dissipation function and the shielding function can be sufficiently realized, the contact between the contact part 9 and the motor housing can be direct or indirect via another element.

[0015] Fig. Fig. 5 is an enlarged cross-sectional view of a part including the pressure detecting structure of the pressure sensor 1 according to the first embodiment of the invention. Fig. 5, the pressure transmission rod 3 includes a pressure transmission part 3a, an element forming part 3b and a high rigidity part 3c.

[0016] The pressure transmission part 3a is in contact with the diaphragm 2 and is provided at a location farther inside the engine than the element forming part 3b and the high-rigidity part 3c when the pressure sensor 1 is mounted on the engine. The pressure transmission part 3a transmits a pressure force received by the diaphragm 2 to the element forming part 3b.

[0017] The element formation part 3b has lower rigidity than the high-rigidity part 3c and is a part that generates deformation corresponding to the compressive force transmitted from the pressure transmission part 3a. A flat surface having a shape in which a part of the pressure transmission part 3a is cut out is formed on the element formation part 3b, and the pressure detection unit 5 is attached to the flat surface. Accordingly, the deformation amount of the pressure detection element 5a forming part in the element formation part 3b is detected by the pressure detection element 5a, and the combustion pressure of the engine corresponding to the deformation amount is detected. In addition, a flat surface having a shape in which a part of the pressure transmission part 3a is cut out is also formed on a side of the element formation part 3b opposite the surface to which the pressure detection unit 5 is attached.Accordingly, in an axial direction of the pressure sensor 1, that is, an insertion direction of the pressure sensor 1 when the pressure sensor 1 is mounted on the engine, the cross-sectional area of ​​the surface perpendicular to that direction is reduced, and the rigidity of the element configuration part 3b is relatively reduced. As a result, the deformation amount of the element configuration part 3b can be increased, and the detection sensitivity can be improved.

[0018] The high-rigidity part 3c is provided to have a cross-sectional area perpendicular to the axial direction of the pressure sensor 1 that is larger than that of the element configuration part 3b and to have a rigidity that is higher than that of the element configuration part 3b. Accordingly, the high-rigidity part 3c has the function of maximizing the amount of deformation in the element configuration part 3b after receiving the compressive force transmitted from the pressure transmission part 3a.

[0019] The high-rigidity part 3c is arranged between the element forming part 3b and the contact part 9, and is connected to the element forming part 3b further inside the engine than the contact part 9 when the pressure sensor 1 is mounted on the engine. Therefore, when the pressure sensor 1 is mounted on the engine, deformation of the pressure sensor 1 generated from the contact part 9 is mitigated in the high-rigidity part 3c, and the generation of deformation in the element forming part 3b can be inhibited. As a result, fluctuation in the sensor output generated during the mounting of the pressure sensor 1 can be suppressed. Fig. 3 and Fig. 5 shows a configuration in which the high-rigidity part 3c is arranged between the housing 6 and the cover 4, and the high-rigidity part 3c is in direct contact with the housing 6, but the high-rigidity part 3c may also be configured to be in indirect contact with the housing 6. For example, the high-rigidity part 3c may also be configured to be connected to the housing 6 via the cover 4 by joining the housing 6 and the cover 4 by welding or the like, and the high-rigidity part 3c is arranged in contact with the cover 4.

[0020] A stress-receiving part 11, which is a part of the housing 6, is provided between the high-rigidity part 3c and the contact part 9. The stress-receiving part 11 is a part that absorbs a deformation stress generated when the contact part 9 is brought into contact with the motor housing. The stress-receiving part 11 has a lower rigidity than the high-rigidity part 3c and thus has a stress-reducing function for reducing the stress applied to the high-rigidity part 3c due to the deformation of the pressure sensor 1, which is generated from the contact part 9 when the pressure sensor 1 is attached to the motor.

[0021] Fig. 6 is a graph showing an example of a relationship between the amount of deformation of the element forming part 3b generated when the pressure sensor 1 is mounted and the temperature of the circuit unit 5b in the pressure detecting unit 5 during engine combustion with respect to the length L of the voltage receiving part 11. In Fig. In Fig. 6, a curve 61 represents the deformation amount of the element configuration part 3b, and a curve 62 represents the temperature of the circuit unit 5b. As shown by curve 61, with the length L of the voltage receiving part 11 increasing, a greater effect can be achieved due to the stress reduction function, so that the deformation amount of the element configuration part 3b can be reduced. However, as shown by curve 62, with the length L of the voltage receiving part 11 increasing, the thermal conductivity from the pressure sensing unit 5 to the contact part 9 is reduced, so that the temperature of the circuit unit 5b increases. That is, the stress reduction effect of the voltage receiving part 11 is in conflict with the heat dissipation property of the pressure sensing unit 5.

[0022] In Fig. 6, the amount of deformation of the element forming part 3b generated when the pressure sensor 1 is mounted is substantially saturated when the length L of the voltage receiving part 11 is 3 mm or more, as shown in curve 61. On the other hand, the temperature of the circuit unit 5b rises in proportion to the length L of the voltage receiving part 11, as shown in curve 62. Therefore, if the pressure sensing unit 5 is designed so that the temperature of the circuit unit 5b is equal to or lower than the heat-resistant temperature when the length L of the voltage receiving part 11 is approximately 3 mm, it is possible to ensure the required heat dissipation property while maximizing the stress-reducing effect of the voltage receiving part 11.For example, by designing the heat-resistant temperature of the circuit unit 5b to 150°C, the amount of deformation of the element forming part 3b is inhibited when the length L of the voltage receiving part 11 is 3 mm, and the fluctuation in the sensor output generated during the mounting of the pressure sensor 1 can be minimized. When obtaining the required sensor output, it is advantageous in terms of cost if the heat-resistant temperature of the circuit unit 5 is as low as possible, so the above-mentioned length L of 3 mm or the heat-resistant temperature of 150°C is merely an example and not a limitation.

[0023] As described above, in the pressure sensor 1, the pressure transmission part 3a, the element configuration part 3b, and the high-rigidity part 3c are integrally formed as the pressure transmission rod 3. Moreover, the high-rigidity part 3c and the voltage receiving part 11 are firmly connected by welding or the like. Furthermore, the voltage receiving part 11 is continuously and integrally formed with the contact part 9. With such a configuration, the element configuration part 3b is thermally and continuously connected to the contact part 9 via the high-rigidity part 3c and the voltage receiving part 11, and the heat in the pressure detection unit 5 provided in the element configuration part 3b can be efficiently dissipated through the motor housing to which the pressure sensor 1 is attached.Accordingly, even in the circuit unit 5b having low heat resistance, the temperature rise of the circuit unit 5b can be inhibited to be equal to or lower than the heat resistance temperature. As long as the element forming part 3b, the high-rigidity part 3c, the stress-bearing part 11, and the contact part 9 can be thermally and continuously connected, any joining method, such as integral manufacturing, welding, soldering, brazing, press fitting, and shrink fitting, can be used. Furthermore, the high-rigidity part 3c can also be in direct contact with the contact part 9 without providing the stress-bearing part 11.

[0024] Furthermore, to efficiently dissipate heat in the pressure sensing unit 5, a heat transfer distance from the pressure sensing unit 5 to the contact part 9 should preferably be short. Since, in the configuration of the pressure sensor 1 according to the present embodiment, a path through which heat is transferred is formed without deviation from the pressure sensing unit 5 to the contact part 9, efficient heat dissipation can be achieved.

[0025] As described above, according to the pressure sensor 1 of the present embodiment, the wiring length connecting the pressure sensing element 5a and the circuit unit 5b is significantly shortened, while the temperature rise of the circuit unit 5b in the pressure sensing unit 5 is inhibited. Therefore, the influence of external noise can be reduced.

[0026] According to the first embodiment of the invention described above, the following effects can be achieved.

[0027] 1.) The pressure sensor 1, which detects the combustion pressure of the engine, includes: the contact part 9, which is in direct or indirect contact with the engine casing when the pressure sensor is mounted on the engine; and the pressure detection unit 5, which detects the combustion pressure of the engine and outputs the sensor output to the outside of the pressure sensor 1. The pressure detection unit 5 includes the pressure detection element 5a, which detects the combustion pressure of the engine and outputs a signal, and the circuit unit 5b, which converts the signal received from the pressure detection element 5a into a pressure signal corresponding to the sensor output. The pressure detection unit 5 is provided at a location positioned further inside the engine than the contact part 9 when the pressure sensor 1 is mounted on the engine. As a result, a pressure sensor can be provided that is resistant to external noise and has improved detection accuracy.

[0028] 2.) The pressure sensor 1 further includes the pressure transmission rod 3, which is a pressure transmission mechanism configured to transmit the engine's combustion pressure to the pressure sensing element 5a. At least a portion of the pressure transmission rod 3 is provided at a location positioned further inside the engine than the circuit unit 5b when the pressure sensor 1 is mounted on the engine. As a result, the engine's combustion pressure can be detected in the pressure sensing element 5a while largely inhibiting a temperature rise of the circuit unit 5b.

[0029] 3.) The pressure sensor 1 further includes the stress-absorbing part 11, which is located between the contact part 9 and the pressure sensing unit 5 and is configured to absorb the deformation stress generated when the contact part 9 is brought into contact with the motor housing. As a result, the amount of deformation of the element forming part 3b generated when the pressure sensor 1 is mounted can be reduced, and the fluctuation of the sensor output can be inhibited.

[0030] 4.) The pressure transmission rod 3 includes the element configuration part 3b, where the pressure sensing element 5a is provided, and the high-rigidity part 3c, which is arranged between the element configuration part 3b and the voltage receiving part 11 or between the element configuration part 3b and the contact part 9 and has a higher rigidity than the element configuration part 3b. As a result, the amount of deformation in the element configuration part 3b can be increased, and the detection of the pressure sensor 1 with respect to the engine combustion pressure can be improved. Modification of the contact part

[0031] In the first embodiment of the invention described above, as the shape of the contact part in contact with the motor housing when the pressure sensor 1 is mounted on the motor, an example of the contact part 9 is shown, which is formed by providing a step in the housing 6 of the pressure sensor, but the contact part in contact with the motor housing may also have a different shape. A modification of the contact part will be described below with reference to Fig. 7 described.

[0032] Fig. 7 shows the modifications of the contact part in the pressure sensor 1. Fig. 7(a) shows an example in which a contact element 12 formed of a member different from the housing 6 is provided on the side surface of the housing 6 as a contact part of the pressure sensor 1. The contact element 12 is formed of a heat-conductive elastic material such as metal and is fixed to the side surface of the housing 6 by brazing, adhesive, press-fitting, caulking, welding, or the like. An outer diameter of the contact element 12 is set to be slightly larger than a diameter of an insertion hole for the pressure sensor 1 provided in the motor housing. When the pressure sensor 1 is attached to the motor, contact with the motor housing is achieved by the elasticity of the contact element 12.

[0033] How Fig. Further, as shown in Fig. 7(b), an O-ring 13 may be provided as a contact part of the pressure sensor 1 on the side surface of the housing 6 of the pressure sensor 1. When the pressure sensor 1 is mounted on the engine, the O-ring 13 is brought into close contact with the engine housing, so that high-temperature combustion gas in the engine is prevented from intruding into a part of the pressure sensor 1 that is further rearward than the O-ring 13. Accordingly, the temperature rise of the circuit unit 5b in the pressure detection unit 5 can be inhibited.

[0034] Furthermore, as a contact part of the pressure sensor 1, a thermally conductive elastic body 14 as shown in Fig. 7(c), may be provided on the side surface of the housing 6 of the pressure sensor 1. The thermally conductive elastic body 14 is formed of an elastic material having high thermal conductivity, such as a resin material mixed with, for example, thermally conductive rubber, metal powder, or ceramic powder, and is attached to the side surface of the housing 6 by adhesive, press-fitting, insert molding, welding, or the like. An outer diameter of the thermally conductive elastic body 14 is set to be slightly larger than the diameter of the insertion hole for the pressure sensor 1 provided in the engine housing. When the pressure sensor 1 is attached to the engine, contact with the engine housing is established by the elasticity of the thermally conductive elastic body 14. Second embodiment

[0035] A second embodiment of the invention will be described below. In the present embodiment, an example will be described in which the pressure detection sensitivity of the pressure sensor 1 described in the first embodiment is further improved.

[0036] Fig. Fig. 8 is an enlarged cross-sectional view of a part of the pressure sensor 1 according to the second embodiment of the invention, which includes the pressure detection structure. In the present embodiment, the position at which the pressure detection unit 5 is provided in the element forming part 3b is different from that of the structure of the first embodiment described with reference to Fig. Fig. 5, is different. In particular, the Fig. 8, the pressure detection unit 5 including the pressure detection element 5a is provided at a position in the element configuration part 3b where the center of the pressure detection unit 5 (pressure detection element 5a) in the axial direction of the pressure sensor 1, that is, the insertion direction of the pressure sensor 1 when the pressure sensor 1 is mounted on the engine, is located closer to the pressure transmission part 3a than the center of the element configuration part 3b in this direction. Accordingly, the detection sensitivity of the pressure sensor 1 with respect to the combustion pressure of the engine is further improved compared to the first embodiment. The other structures are the same as those of the first embodiment.

[0037] The reason why the pressure detection sensitivity of the pressure sensor 1 is improved in the present embodiment will be explained below with reference to Fig. 9 described. Fig. 9 shows schematic views illustrating deformed states of the element forming part 3b during pressure absorption in the first embodiment and the second embodiment of the invention. Fig. Fig. 9(a) shows a deformed state in the configuration of the first embodiment and Fig. 9(b) shows a deformed state in the configuration of the present embodiment.

[0038] How Fig. 5, in the first embodiment, the pressure detection unit 5 is provided substantially in the center of the element forming part 3b in the axial direction of the pressure sensor 1. In this structure, in the deformed state of the element forming part 3b during pressure reception, as shown in Fig. 9(a), the pressure transmission part 3a is inclined with respect to the axial direction. Therefore, of the two flat surfaces formed on the element configuration part 3b, deformation occurs on a flat surface on the side where the pressure detection part 5 is provided, such that the vicinity of the configuration part of the pressure detection unit 5 becomes convex, and the vicinity of the connection part with the pressure transmission part 3a becomes concave. This is because when the pressure detection unit 5 is provided on a flat surface of the element configuration part 3b, the rigidity of the configuration part is relatively high, and the configuration part is less likely to be compressed.Accordingly, the element forming part 3b, which should be compressed in the axial direction after receiving the compressive force transmitted from the pressure transmitting part 3a, deforms into the shape described above, resulting in the compressive force being relieved and the amount of deformation generated in the pressure sensing element 5a being reduced. As a result, the pressure sensing sensitivity of the pressure sensor 1 can be reduced.

[0039] On the other hand, in the deformed state of the element forming part 3b during pressure absorption in the structure of the present invention as shown in Fig. 9(b), the deformation in which the pressure transmission part 3a is inclined with respect to the axial direction is prevented. The reason for this is that when the deployment position of the pressure detection unit 5 in the element forming part 3b is adjusted as described above, the pressure detection unit 5 in the vicinity of the connecting part with the Fig. 9 (a) is provided with a concavely deformed pressure transmission part 3a, so that the above-described deformation is prevented. As a result, the pressure detection sensitivity of the pressure sensor 1 can be improved compared to the first embodiment.

[0040] According to the second embodiment of the invention described above, the pressure transmission rod 3 is provided at a position further inside the engine than the element configuration part 3b when the pressure sensor 1 is mounted on the engine, and includes the pressure transmission part 3a that transmits pressure to the element configuration part 3b. The pressure sensing element 5a is provided in the element configuration part 3b, and the center of the pressure sensing element 5a is closer to the pressure transmission part 3a than the center of the element configuration part 3b in the insertion direction of the pressure sensor 1 when the pressure sensor is mounted on the engine. As a result, deformation with inclination of the pressure transmission part 3a is suppressed, and the pressure detection sensitivity of the pressure sensor 1 can be improved.

[0041] In the second embodiment of the invention described above, an example of improving pressure detection sensitivity is shown in which the length of the pressure transmission part 3a is the same as that of the first embodiment. However, the length of the pressure transmission part 3a can be longer than that of the first embodiment, and a resulting reduction in pressure detection sensitivity can be offset by the effect of improving pressure detection sensitivity according to the present embodiment. In this way, since the pressure detection unit 5 including the circuit unit 5b can be relocated away from the combustion chamber of the engine, the temperature rise of the circuit unit 5b can be inhibited while maintaining pressure detection sensitivity. Third embodiment

[0042] A third embodiment of the invention will be described below. In the present embodiment, an example will be described in which the pressure detection sensitivity is further improved by a method different from that described in the second embodiment based on the pressure sensor 1 described in the first embodiment.

[0043] Fig. Fig. 10 is an enlarged cross-sectional view of a part including the pressure detection structure of the pressure sensor 1 according to the third embodiment of the invention. In the present embodiment, the shape of the element forming part 3b differs from that of the pressure sensor 1 described with reference to Fig. Fig. 5 described structure of the first embodiment. In particular, in the Fig. 10, the element forming part 3b includes a flat mounting surface 3d on which the pressure sensing unit 5 including the pressure sensing element 5a is provided, and a cutout surface 3e provided on a side opposite to the mounting surface 3d and having a step portion 3f. The position of the step portion 3f on the cutout surface 3e is further rearward in the axial direction of the pressure sensor 1, that is, away from the combustion chamber of the engine, than the position of the step formed at a boundary portion between the pressure transmitting part 3a and the element forming part 3b on the mounting surface 3d on the opposite side.

[0044] The reason why the pressure detection sensitivity of the pressure sensor 1 is improved in the present embodiment will be explained below with reference to Fig. 11 explained. Fig. 11 is a schematic view showing a deformed state of the element forming part 3b during pressure absorption in the third embodiment of the invention.

[0045] In the deformed state of the element forming part 3b during pressure absorption in the structure of the present embodiment, as shown in Fig. 11, the deformation occurs in the element configuration part 3b, and the mounting surface 3d on which the pressure sensing element 5a is provided becomes concave. This is because when the element configuration part 3b is formed into a thick shape and has improved rigidity compared to the first embodiment, and the step part 3f is provided on the cutout surface 3e opposite to the mounting surface 3d in the element configuration part 3b, the mounting surface 3d is easily deformed into a concave shape. In this way, by deforming the surface on which the pressure sensing unit 5 is provided into a concave shape, pressure due to bending is applied to the pressure sensing element 5a in addition to the compressive load of the pressure sensor 1 in the axial direction. As a result, the pressure detection sensitivity of the pressure sensor 1 can be improved compared to the first embodiment.

[0046] According to the third embodiment of the invention described above, the pressure transmission rod 3 is provided at a location positioned further inside the engine than the element configuration part 3b when the pressure sensor 1 is mounted on the engine, and includes the pressure transmission part 3a that transmits the pressure to the element configuration part 3b. The element configuration part 3b has the mounting surface 3d on which the pressure sensing element 5a is provided, and the cutout surface 3e provided on a side opposite the mounting surface 3d and having the step part 3f. As a result, it is possible to apply the pressure by bending the pressure sensing element 5a to improve the pressure detection sensitivity of the pressure sensor 1.

[0047] In the third embodiment of the invention described above, similarly to the second embodiment, the length of the pressure transmission part 3a can be configured longer than that of the first embodiment. That is, in the third embodiment of the invention, an example of improving pressure detection sensitivity is shown in which the length of the pressure transmission part 3a is the same as that of the first embodiment, but the length of the pressure transmission part 3a can be longer than that of the first embodiment, and the resulting reduction in pressure detection sensitivity can be compensated for by the effect of improving pressure detection sensitivity according to the present embodiment.In this way, since the pressure detection unit 5 including the circuit unit 5b can be displaced away from the combustion chamber of the engine, the temperature rise of the circuit unit 5b can be inhibited while maintaining the pressure detection sensitivity.

[0048] Furthermore, in the third embodiment of the invention described above, the position where the pressure detection unit 5 is provided in the element configuration part 3b is the same as in the first embodiment, but may also be the same as in the second embodiment. Therefore, even in a configuration in which the second embodiment is modified, the same effects as described above can be achieved. Fourth embodiment

[0049] A fourth embodiment of the invention will be described below. In the present embodiment, an example will be described in which the temperature rise of the pressure detection circuit in the pressure sensor 1 described in the first embodiment is further inhibited.

[0050] Fig. Fig. 12 is an enlarged cross-sectional view of a part including the pressure detection structure of the pressure sensor 1 according to the fourth embodiment of the invention. In the present embodiment, compared to the pressure sensor shown in Fig. In the structure of the first embodiment described in FIG. 5, a thermally conductive material 15 is added between the pressure sensing unit 5 and the contact part 9. The thermally conductive material 15 is made, for example, of a resin material such as thermally conductive rubber, an epoxy resin, a silicone resin, and a urethane resin mixed with thermally conductive powder such as metal powder and ceramic powder, or of a material softer than the casing 6 and the high-rigidity part 3c, such as a thermally conductive grease. The thermally conductive material 15 is filled between the inside of the casing 6 and the high-rigidity part 3c and improves the heat dissipation characteristics of the pressure sensing unit 5 from the circuit unit 5b to the contact part 9 via the element configuration part 3b and the high-rigidity part 3c.

[0051] According to the fourth embodiment of the invention described above, the pressure sensor 1 further includes the thermally conductive material 15 disposed between the pressure sensing unit 5 including the circuit unit 5b and the contact part 9. In this way, the heat dissipation property from the circuit unit 5b can be improved, and the temperature rise of the circuit unit 5b can be inhibited. Furthermore, since the thermally conductive material 15 is softer than the case 6 and the high-rigidity part 3c, the influence of stress due to deformation of the case 6 or the like is small. Therefore, the temperature rise of the circuit unit 5b can be inhibited without adversely affecting the sensor output.

[0052] In the third embodiment of the invention described above, an example is shown in which the thermally conductive material 15 is filled up to the high-rigidity part 3c, but the thermally conductive material 15 may be further filled around the element configuration part 3b to cover the pressure detection unit 5. At this time, it is desirable that the thermally conductive material 15 not be in contact with the cover 4, so that the heat inside the engine is not transferred to the pressure detection unit 5 via the cover 4 and the thermally conductive material 15. With this configuration, the temperature rise of the pressure detection unit 5 can be further inhibited. Modification of the thermally conductive material

[0053] In the fourth embodiment of the invention described above, the thermally conductive material arranged between the pressure sensing unit 5 and the contact part 9 may have a different shape. A modification of the thermally conductive material will be described below with reference to Fig. 13 described.

[0054] Fig. 13 shows modifications of the thermally conductive material in the pressure sensor 1. How Fig. 13(a), a configuration can be achieved in which the high rigidity part 3c is extended to the inside of the housing 6 and a thermally conductive material 16 is filled therebetween. Furthermore, as shown in Fig. 13(b), a configuration can be achieved in which the interior of the housing 6 is expanded, and a thermally conductive material 17 can be filled between the interior of the housing 6 and the high-rigidity part 3c. The material of the thermally conductive material 16 and 17 is the same as that of the thermally conductive material 15 shown in Fig. 12 was described.

[0055] The above-described embodiments and various modifications are merely examples, and the invention is not limited to these contents as long as the features of the invention are not impaired. Furthermore, although various embodiments and modifications have been described above, the invention is not limited to these contents. Other embodiments considered to be within the scope of the technical idea of ​​the invention are also included within the scope of the invention.

[0056] The disclosure of the following priority application is incorporated herein by reference.

[0057] Japanese Patent Application No. 035081 (February 27, 2017). List of reference symbols 1 pressure sensor 2 membrane 3 pressure transmission rod 3a Pressure transmission part 3b Element formation part 3c Part of high stiffness 4 Cover 5 Pressure detection unit 5a Pressure sensing element 5b Circuit unit 6 housings 7 Connection part 8 Signal line 9 Contact part 10 threaded part 11 Voltage pickup part 12 Contact element 13 O-ring 14 thermally conductive elastic body 15, 16, 17 thermally conductive material

Claims

[1] Pressure sensor (1) which detects a combustion pressure of an engine, which pressure sensor (1) contains: a contact part (9) which is in direct or indirect contact with a motor housing when the pressure sensor (1) is attached to the motor; and a pressure detection unit (5) which detects the combustion pressure and outputs a signal corresponding to the combustion pressure, wherein the pressure detection unit (5) includes a pressure detection element (5a) which detects the combustion pressure and outputs a signal, and a circuit unit (5b) which converts the signal received from the pressure detection element (5a) into a signal corresponding to the combustion pressure, and wherein the pressure detection unit (5) is arranged at a location which is positioned further inside the motor than the contact part (9) when the pressure sensor (1) is attached to the motor, wherein the pressure sensor (1) further includes a pressure transmission mechanism (3) which transmits the combustion pressure to the pressure sensing element (5a), wherein at least a part of the pressure transmission mechanism (3) is provided at a location positioned further inside the engine than the circuit unit (5b) when the pressure sensor (1) is mounted on the engine, and wherein the pressure transmission mechanism (3) includes a part (3b) providing an element on which the pressure sensing element (5a) is provided, and a high-rigidity part (3c) provided between the part (3b) and the contact part (9) and having a higher rigidity than the part (3b). [2] Pressure sensor (1) according to claim 1, further comprising: a thermally conductive material (15, 16, 17) arranged between the circuit unit (5b) and the contact part (9). [3] Pressure sensor (1) according to claim 1, wherein the pressure transmission mechanism (3) is provided at a location positioned further inside the engine than the part (3b) when the pressure sensor (1) is attached to the engine, and further includes a pressure transmission part (3a) which transmits a pressure to the part (3b), and the pressure sensing element (5a) is provided at a position in the part (3b), wherein the center of the pressure sensing element (5a) in an insertion direction of the pressure sensor (1) when the pressure sensor (1) is attached to the engine is closer to the pressure transmitting part (3a) than a center of the part (3b). [4] Pressure sensor (1) according to claim 1, wherein the pressure transmission mechanism (3) is provided at a location positioned further inside the engine than the part (3b) when the pressure sensor (1) is attached to the engine, and further includes a pressure transmission part (3a) which transmits a pressure to the part (3b), and the part (3b) has a mounting surface (3d) on which the pressure detecting element (5a) is provided, and a cut-out surface (3e) provided on a side opposite to the mounting surface (3d) and having a step part (3f).

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