Patent Description:
A pressure detection device for detecting pressure of a fluid from an internal combustion engine is known (e.g., <CIT>). After a certain period of use of such a device, incomplete combustion products accumulate on a temperature reducing member that reduces the temperature of the fluid and supplies it to a pressure receiving member. Since the accumulation of incomplete combustion products may inhibit accurate pressure measurement, it is necessary to periodically remove the incomplete combustion products adhering to the temperature reducing member. Another device for measuring electrical pressures is disclosed by <CIT>.

However, it is difficult to remove incomplete combustion products from the temperature reducing member when the temperature reducing member and the pressure receiving member are tightly connected by being joined together by laser welding etc. or by being integrally molded.

It is an object of certain embodiments of the present invention to enable easy removal of incomplete combustion products adhering to the temperature reducing member even when the temperature reducing member and the pressure receiving member are tightly connected.

With the above object in view, the present invention, as defined by appended claim <NUM>, provides a pressure detection device comprising: a body configured to be mounted in a hole in an internal combustion engine; a pressure receiving member provided at one end of the body and configured to receive pressure of a fluid from the internal combustion engine; and a temperature reducing member located at the pressure receiving member on a leading end at the one end of the body and configured to supply the fluid to the pressure receiving member while reducing temperature of the fluid. The pressure receiving member comprises: a pressure receiving portion configured to be displaced under pressure; and a pressure receiving support portion joined to or integrated with a first member, the first member being joined to or integrated with the pressure receiving member and having an inner circumferential surface. The temperature reducing member comprises: the first member; and a second member having an outer circumferential surface facing the inner circumferential surface. Female threads formed on the inner circumferential surface of the first member and male threads formed on the outer circumferential surface of the second member are configured to threadably engage each other.

The first member may be integrally molded with the pressure receiving support portion.

The second member may comprise a plurality of communication holes configured to allow the fluid to be supplied to the pressure receiving portion.

The second member threaded with the first member may be located at a position where the second member does not contact the pressure receiving member.

The pressure detection device may further comprise a securing mechanism configured to secure the second member threaded with the first member.

The securing mechanism may comprise a combination of a threaded hole formed in a threaded engagement portion between the first member and the second member and a screw configured to be threaded into the threaded hole.

The threaded hole may be formed in the axial direction of the first member and the second members, and the first member may comprise a cut-away portion configured to mate with a portion of a head of the screw threaded into the threaded hole.

The head of the screw may be of a cylindrical shape.

The threaded hole may be formed in a direction perpendicular to the axial direction of the first member and the second member.

The head of the screw threaded into the threaded hole may be configured not to protrude from an entrance of the threaded hole.

The second member may comprise at least one straight groove on a leading end surface thereof.

The second member may be configured to be separated into a plurality of sub-members and assembled from the plurality of separated sub-members.

Each of the separated multiple sub-members may comprise a recess and a protrusion used for mating during assembly.

Certain embodiments of the present invention enable easy removal of incomplete combustion products adhering to the temperature reducing member even when the temperature reducing member and the pressure receiving member are tightly connected.

An exemplary embodiment of the present invention will now be described with reference to the drawings.

<FIG> is a side view of a pressure detection device <NUM> according to an exemplary embodiment. <FIG> illustrates a schematic configuration of the pressure detection device <NUM> as mounted in an internal combustion engine <NUM>, and <FIG> is an enlarged view of an area around a step 13b. <FIG> is a cross-sectional view of the pressure detection device <NUM> (taken along line III-III in <FIG>). <FIG> is an enlarged cross-sectional view of a leading end of the pressure detection device <NUM> (region IV in <FIG>).

The pressure detection device <NUM> according to the present embodiment is a device to detect pressure (combustion pressure) in a combustion chamber C in the internal combustion engine <NUM>. In response to the pressure detection device <NUM> detecting pressure in the combustion chamber C, a controller (not shown) controls the operation of the internal combustion engine <NUM> based on the detected pressure. The pressure detection device <NUM> and the controller are electrically connected via a connecting cable <NUM>.

The pressure detection device <NUM> includes an generally cylindrical enclosure assembly <NUM> exposed to the outside, a detection mechanism assembly <NUM> including various mechanisms for detecting pressure and housed in the enclosure assembly <NUM> in its substantial entirety with a portion thereof exposed to the outside, a sealing portion <NUM> attached to the outer circumference surface of the enclosure assembly <NUM>, and a buffer member <NUM> attached to one end of the enclosure assembly <NUM> (left side of the enclosure assembly <NUM> in <FIG>).

Here, the configuration of the internal combustion engine <NUM>, which is subject to pressure detection by the pressure detection device <NUM>, is described. The internal combustion engine <NUM> includes a cylinder block <NUM> with a cylinder formed therein, a piston <NUM> that reciprocates in the cylinder, and a cylinder head <NUM> that is fastened to the cylinder block <NUM> to constitute the combustion chamber C together with the piston <NUM> and other components. The cylinder head <NUM> includes a communication hole 13a providing communication of the combustion chamber C with the outside. The communication hole 13a includes a step 13c located in its intermediate position and a step 13b located closer to the combustion chamber C than the step 13c is. As such, the communication hole 13a consists of a small-diameter portion located closer to the combustion chamber C than the step 13b is and having a smaller inner diameter, a medium-diameter portion located outside relative to the step 13b and closer to the combustion chamber C than the step 13c is and having an inner diameter larger than the small-diameter portion, and a large-diameter portion located outside relative to the step 13c and having an inner diameter larger than the medium-diameter portion. The pressure detection device <NUM> is attached to the internal combustion engine <NUM> by inserting the leading end of the pressure detection device <NUM> into the communication hole 13a and securing the pressure detection device <NUM> to the cylinder head <NUM>. The cylinder block <NUM>, the piston <NUM>, and the cylinder head <NUM> constituting the internal combustion engine <NUM> are made of a conductive metal material such as cast iron and aluminum.

The pressure detection device <NUM> is attached to the above configured internal combustion engine <NUM> such that the left side of the pressure detection device <NUM> in <FIG> (buffer member <NUM> side) faces the combustion chamber C (bottom side in <FIG>) and the right side of the pressure detection device <NUM> in <FIG> (connecting cable <NUM> side) faces the outside (top side in <FIG>). In the following description, the leftward side of the pressure detection device <NUM> in <FIG> is referred to as the "leading end" thereof, and the rightward side of the pressure detection device <NUM> in <FIG> is referred to as the "trailing end" thereof. The direction of an axis along the centerline is referred to as the "axial direction. " The direction along a radius of the pressure detection device <NUM> is referred to as the "radial direction. " When referring to the radial direction, the direction toward the centerline of the pressure detection device <NUM> indicated by a dashed- and-dotted line in <FIG> and other figures is referred to as "inside" and the direction away from the centerline is referred to as "outside. " In the present embodiment, the "leading end" and the "trailing end" correspond to the "one end" and the "other end," respectively.

The enclosure assembly <NUM> as an example of the body includes a leading end external enclosure <NUM>, a diaphragm head <NUM> attached to the leading end of the leading end external enclosure <NUM>, an intermediate external enclosure <NUM> attached to the trailing end of the leading end external enclosure <NUM>, and a trailing end external enclosure <NUM> attached to the trailing end of the intermediate external enclosure <NUM>. The enclosure assembly <NUM> further includes a first internal enclosure <NUM> disposed within the leading end external enclosure <NUM> and attached to the trailing end of the diaphragm head <NUM>, and a second internal enclosure <NUM> disposed within the leading end external enclosure <NUM> and attached to the trailing end of the first internal enclosure <NUM>.

The leading end external enclosure <NUM> is a hollow and generally cylindrical member. The leading end external enclosure <NUM> is made of a conductive metal material with high heat and acid resistance, such as stainless steel. Examples of such metal materials include SUS630, known as a precipitation hardening stainless steel, and SUH660, known as an austenitic heat-resistant steel (heat-resistant alloy). However, any of various other metals or alloys (various stainless steels, various heat-resistant steels or various heat-resistant alloys) that satisfy the required characteristics may be employed.

The portion of the leading end external enclosure <NUM> to be inserted into the communication hole 13a has a constant outer diameter that is substantially the same as the inner diameter of the medium-diameter portion of the communication hole 13a close to the combustion chamber C. The leading end external enclosure <NUM> is provided at its trailing end with an overhang <NUM> having an outer diameter larger than the inner diameter of the medium-diameter portion of the communication hole 13a. When the pressure detection device <NUM> is mounted on the cylinder head <NUM>, the overhang <NUM> of the leading end external enclosure <NUM> abuts the step 13c in the communication hole 13a via a first sealing member <NUM>. A leading end surface of the overhang <NUM> is referred to as a seating surface <NUM>.

The leading end external enclosure <NUM> is provided with male threads (not shown) on its outer circumferential surface. In addition, the communication hole 13a in the cylinder head <NUM> shown in <FIG> is provided with female threads (not shown) on its inner wall, which can threadably engage the above male threads provided on the leading end external enclosure <NUM>. The communication hole 13a is provided with the step 13b in its portion that is closer to the leading end than its portion provided with the above female threads is. The leading end (buffer member <NUM>) of the pressure detection device <NUM> abuts this step.

The diaphragm head <NUM> as an example of the pressure receiving member is a generally disk-like member. The diaphragm head <NUM> is made of a conductive metal material with high heat and acid resistance, such as stainless steel. Examples of such metal materials include SUS630, known as a precipitation hardening stainless steel, and SUH660, known as an austenitic heat-resistant steel (heat-resistant alloy). However, any of various other metals or alloys (various stainless steels, various heat-resistant steels or various heat-resistant alloys) that satisfy the required characteristics may be employed. In this example, the diaphragm head <NUM> is made of the same material as the leading end external enclosure <NUM> (e.g., SUS630).

The diaphragm head <NUM> includes a pressure membrane 32a and a front side central recess 32b, which are an example of the pressure receiving portion, at the center of its leading end, where the pressure membrane 32a and the front side central recess 32b undergo pressure-dependent displacement by being exposed to the outside (toward the combustion chamber C). The diaphragm head <NUM> also includes a rear side annular recess 32c formed by annularly cutting away a portion of the rear surface opposite the pressure membrane 32a, and a rear side central protrusion 32d protruding from the center of the pressure membrane 32a (where the front side central recess 32b is formed) toward the trailing end as a result of the presence of the rear side annular recess 32c.

The diaphragm head <NUM> further includes a rear side annular protrusion 32e located in the trailing end around the periphery of the pressure membrane 32a, and a front side annular protrusion <NUM>, which is an example of the pressure receiving support portion, protruding from the entire periphery of the pressure membrane 32a toward the leading end. The front side annular protrusion <NUM> is located opposite the rear side annular protrusion 32e (i.e., on the front side). The front side annular protrusion <NUM> is joined to a portion of a first buffer member <NUM> of the buffer member <NUM> (described below) or integrally molded with the first buffer member <NUM>. From another perspective, the leading end of the diaphragm head <NUM> can be viewed as having the front side annular protrusion <NUM> and the pressure membrane 32a formed by circularly cutting away a central portion of the leading end of the diaphragm head <NUM>, and the front side central recess 32b formed by further cutting away a central portion of the pressure membrane 32a.

The diaphragm head <NUM> is disposed to close a leading end opening of the leading end external enclosure <NUM>. More specifically, a portion of the leading end of the leading end external enclosure <NUM> abuts the rear side annular protrusion 32e of the diaphragm head <NUM>. The diaphragm head <NUM> and the leading end external enclosure <NUM> are laser-welded at their interface around the entire outer circumference. The diaphragm head <NUM> of the present embodiment functions as a spring as the area around the rear side annular recess 32c, which is the thinnest portion thereof, is displaced in response to external forces. The diaphragm head <NUM> vibrates as it receives pressure (external pressure) from the combustion chamber C and the like.

The intermediate external enclosure <NUM> is a hollow and generally cylindrical member. The intermediate external enclosure <NUM> is made of a conductive metal material with high heat and acid resistance, such as stainless steel. Examples of such metal materials include SUS430LX, known as a ferritic stainless steel. However, any of various other metals or alloys (various stainless steels, various heat-resistant steels or various heat-resistant alloys) that satisfy the required characteristics may be employed. In this example, the intermediate external enclosure <NUM> is made of a different material (e.g., SUS430LX) from the leading end external enclosure <NUM>. The leading end of the intermediate external enclosure <NUM> is adapted to fit into the trailing end of the leading end external enclosure <NUM>. The intermediate external enclosure <NUM> and the leading end external enclosure <NUM> are laser-welded at their interface around the entire outer circumference.

The trailing end external enclosure <NUM> is a hollow and generally cylindrical member. The trailing end external enclosure <NUM> is made of a conductive metal material with high heat and acid resistance, such as stainless steel. Examples of such metal materials include SUS430LX, known as a ferritic stainless steel. However, any of various other metals or alloys (various stainless steels, various heat-resistant steels or various heat-resistant alloys) that satisfy the required characteristics may be employed. In this example, the trailing end external enclosure <NUM> is made of the same material (e.g., SUS430LX) as the intermediate external enclosure <NUM>. The leading end of the trailing end external enclosure <NUM> is adapted to fit into the trailing end of the intermediate external enclosure <NUM>. The trailing end external enclosure <NUM> and the intermediate external enclosure <NUM> are laser-welded at their interface around the entire outer circumference.

The detection mechanism assembly <NUM> includes a conducting member <NUM>, a retaining member <NUM>, a second coil spring <NUM>, a first housing member <NUM>, a second housing member <NUM>, a circuit-embedded member <NUM>, a connecting member <NUM>, a closing member <NUM>, and a third insulating member <NUM>. The detection mechanism assembly <NUM> further includes a piezoelectric element <NUM> including a piezoelectric body that demonstrates piezoelectric behavior of a longitudinal piezoelectric effect. The detection mechanism assembly <NUM> further includes a leading end electrode member <NUM>, a trailing end electrode member <NUM>, and a support member <NUM>, each of which is made of a conductive metal material. The detection mechanism assembly <NUM> further includes a leading end insulating member <NUM>, a trailing end insulating member <NUM>, a first insulating member <NUM>, and a second insulating member <NUM>, each of which is made of an insulating ceramic material.

The detection mechanism assembly <NUM> further includes a first coil spring <NUM> that expands and contracts in the axial direction, a pressure member <NUM> that functions as a spring by expanding and contracting in its side on the leading end, which is the thinnest portion thereof, in response to external forces, and an insulating tube <NUM> that functions to integrate (modularize) the leading end electrode member <NUM>, the piezoelectric element <NUM>, the trailing end electrode member <NUM>, and the trailing end insulating member <NUM> together with the insulating tube <NUM> by accommodating and securing these components in a contacting relationship.

The conducting member <NUM> is a generally rod-like member and disposed inside the leading end external enclosure <NUM>. The conducting member <NUM> is made of a conductive metal material, such as brass, and gold-plated on its surface. The conducting member <NUM> includes a leading end rod-like portion <NUM> located in the leading-most position, an intermediate rod-like portion <NUM> in a trailing position relative to the leading end rod-like portion <NUM>, and a trailing end rod-like portion <NUM> in a trailing position relative to the intermediate rod-like portion <NUM>. In the conducting member <NUM>, the trailing end rod-like portion <NUM> has the largest outer diameter, followed by the intermediate rod-like portion <NUM>, then by the leading end rod-like portion <NUM>.

The retaining member <NUM> is a hollow and generally cylindrical member. The retaining member <NUM> is made of a synthetic resin material with insulating properties such as polyphenylene sulfide (PPS) or polypropylene terephthalate (PPT). The retaining member <NUM> includes a leading end portion located in the leading-most position, an intermediate portion in a trailing position relative to the leading end portion, and a trailing end portion in a trailing position relative to the intermediate portion. In the retaining member <NUM>, the trailing end portion has the largest outer diameter, followed by the intermediate portion, then by the leading end portion. The retaining member <NUM> is disposed in both interiors of the leading end external enclosure <NUM> and the intermediate external enclosure <NUM>. The retaining member <NUM> accommodates and retains the above conducting member <NUM>.

The second coil spring <NUM> is a generally helical member and adapted to expand and contract in the centerline direction. The second coil spring <NUM> is made of a conductive metal material with high heat resistance, such as phosphor bronze, and gold-plated on its surface. In this example, the second coil spring <NUM> is made of the same material as the first coil spring (e.g., phosphor bronze). The second coil spring <NUM> is disposed inside the leading end external enclosure <NUM>.

The first housing member <NUM> is a hollow and generally cylindrical member. The first housing member <NUM> is made of a conductive metal material, such as brass or stainless steel, and gold-plated on its surface. The first housing member <NUM> is disposed inside the leading end external enclosure <NUM>.

The second housing member <NUM> is a hollow and generally cylindrical member. As with the first housing member <NUM>, the second housing member <NUM> is made of a conductive metal material, such as brass or stainless steel, and gold-plated on its surface. The second housing member <NUM> is disposed in both interiors of the leading end external enclosure <NUM> and the intermediate external enclosure <NUM>.

As shown in <FIG>, the circuit-embedded member <NUM> includes a circuit board <NUM> that applies various types of processing using electronic circuitry to electrical signals based on small electric charges output from the piezoelectric element <NUM>, and an encapsulating portion <NUM> that encapsulates the circuit board <NUM> by accommodating it therein. The circuit-embedded member <NUM> is disposed inside the intermediate external enclosure <NUM>, with almost the entirety of the circuit-embedded member <NUM>, except for the trailing end thereof, being disposed inside the second housing member <NUM>. In particular, the circuit board <NUM> in its entirety is disposed inside the second housing member <NUM>. The leading end of the circuit-embedded member <NUM> is adapted to fit into a recess in the trailing end of the retaining member <NUM>. A metal plate (electrode terminal) provided on the leading end of the circuit-embedded member <NUM> is adapted to connect to the trailing end of the conducting member <NUM>. Additionally, a metal plate (electrode terminal) provided on the outer circumferential surface of the circuit-embedded member <NUM> is adapted to contact the inner circumferential surface of the second housing member <NUM>.

The connecting member <NUM> is a generally columnar member. The connecting member <NUM> includes a base member made of a synthetic resin material with insulating properties, such as PPS or PPT, and wires and terminals made of a conductive metal material, such as copper. The connecting member <NUM> is disposed in both interiors of the intermediate external enclosure <NUM> and the trailing end external enclosure <NUM>. The portion of the connecting member <NUM> that confronts the intermediate external enclosure <NUM> or the trailing end external enclosure <NUM> (i.e., the outer circumferential surface of the connecting member <NUM>) is made of a synthetic resin material, so that no metal material is exposed in this portion. The leading end of the connecting member <NUM> confronts the trailing end of the circuit-embedded member <NUM>, and a metal plate (electrode terminal) provided on the circuit-embedded member <NUM> is adapted to fit into the terminal provided in the connecting member <NUM>. The trailing end of the connecting member <NUM> allows for insertion therein of respective conductor portions exposed on the leading ends of a power line <NUM>, a signal line <NUM>, and a ground line <NUM> (their details are described below), which constitute the connecting cable <NUM>. The intermediate external enclosure <NUM> and the connecting member <NUM> are integrated by press-fit (interference fit).

The closing member <NUM> is a generally columnar member. However, the closing member <NUM> is formed with three through-holes along the centerline direction. The closing member <NUM> is made of a rubber material with insulating properties. The closing member <NUM> has its leading end disposed inside the trailing end external enclosure <NUM> and has its trailing end protruding outward relative to the trailing end of the trailing end external enclosure <NUM>. The leading end of the closing member <NUM> confronts the trailing end of the connecting member <NUM>. The power line <NUM>, the signal line <NUM>, and the ground line <NUM> described above are inserted into the three through-holes in the closing member <NUM>. The trailing end external enclosure <NUM> and the closing member <NUM> are integrated by press-fit (interference fit).

The third insulating member <NUM> is a hollow and generally cylindrical member. However, the third insulating member <NUM> has a structure that integrates a cylindrical portion in a leading position and an annular portion in a trailing position. The third insulating member <NUM> is made of a synthetic resin material with insulating properties, such as PPS. The third insulating member <NUM> is disposed in both interiors of the leading end external enclosure <NUM> and the intermediate external enclosure <NUM>.

As shown in <FIG>, the sealing portion <NUM> includes a first sealing member <NUM> in a relative leading position and a second sealing member <NUM> in a relative trailing position.

The first sealing member <NUM> is a generally annular member and, in this example, configured with a square ring with a square cross-section. The first sealing member <NUM> is made of a copper material with high heat and acid resistance and a tin-plated surface. The first sealing member <NUM> is attached to the outer circumferential surface of the leading end external enclosure <NUM>, which constitutes the enclosure assembly <NUM>. More particularly, the first sealing member <NUM> is attached to the outer circumferential surface of the leading end external enclosure <NUM> so as to contact the seating surface <NUM> of the overhang <NUM>. Since the seating surface <NUM> is the leading end face of the overhang <NUM>, upon the pressure detection device <NUM> with the attached first sealing member <NUM> being mounted on the cylinder head <NUM>, the seating surface <NUM> faces the step 13c of the communication hole 13a with the first sealing member <NUM> in between.

The second sealing member <NUM> is a generally annular member and, in this example, configured with an O-ring with a circular cross-section. The second sealing member <NUM> is made of a synthetic rubber material with high mechanical resilience, such as fluororubber. The second sealing member <NUM> is attached to the outer circumferential surface of the trailing end external enclosure <NUM>, which constitutes the enclosure assembly <NUM>. The second sealing member <NUM> serves as a sealing member to prevent entry of water and the like from outside the internal combustion engine <NUM>, and also serves as a damping member to prevent the pressure detection device <NUM> from vibrating, which may otherwise occur during operation of the internal combustion engine <NUM> or due to vibrations in the installation environment, and thus hitting the inner surface of the communication hole 13a in the cylinder head <NUM>. Therefore, among the materials with high mechanical resilience, a fluororubber material is particularly suitable for the second sealing member <NUM> as it has high heat-resistant resilience and provides a long-lasting damping function.

The buffer member <NUM> as an example of the temperature reducing member is a generally cylindrical member and disposed in the leading end of the pressure detection device <NUM>. The buffer member <NUM> is composed of a first buffer member <NUM> as an example of the first member and a second buffer member <NUM> as an example of the second member detachably joined to the first member. When the pressure detection device <NUM> is mounted on the cylinder head <NUM>, the buffer member <NUM> abuts the step 13b in the communication hole 13a. More specifically, a front surface <NUM> of the first buffer member <NUM> (described below) of the buffer member <NUM> abuts the step 13b in the communication hole 13a.

The first buffer member <NUM> comprises a generally hollow cylindrical wall. The first buffer member <NUM> includes an annular front surface <NUM> on its leading end and an annular rear surface <NUM> on its trailing end. The first buffer member <NUM> also includes an outer circumferential surface <NUM> and an inner circumferential surface <NUM> that is provided with female threads. The inner circumferential surface <NUM> includes a cut-away portion <NUM> at its one end that is in a leading position relative to the female threads formed on the inner circumferential surface <NUM> and connects to the front surface <NUM>. The cut-away portion <NUM> has a larger inner diameter than that of the female threads.

The first buffer member <NUM> is made of a metal material (super heat-resistant alloy) with conductivity and higher heat resistance than the diaphragm head <NUM>. Examples of such metal materials include some kinds of iron-based, Gamma prime precipitation-strengthened super heat-resistant alloys. However, any of various other super heat-resistant alloys that satisfy the required characteristics may be employed. Examples of super heat-resistant alloys that can be used include matrix-reinforced super heat-resistant alloys, carbide precipitation-strengthened super heat-resistant alloys, and Gamma prime precipitation-strengthened super heat-resistant alloys. The super heat-resistant alloys that can be used may be iron-based alloys, nickel-based alloys, or cobalt-based alloys. The first buffer member <NUM> may be made of a copper alloy material with high thermal conductivity, such as a beryllium copper alloy (JIS C172, hereafter denoted as BeCu). Other choices than BeCu may include admiralty brass (JIS C4430), aluminum brass (JIS C6870), and naval brass (JIS C4640).

The second buffer member <NUM> is a generally columnar member. The second buffer member <NUM> includes a circular front surface <NUM> on its leading end and a circular rear surface <NUM> on its trailing end. The second buffer member <NUM> includes an outer circumferential surface <NUM> provided with male threads. The second buffer member <NUM> includes a collar <NUM> on the outer circumferential surface <NUM> that has a larger outer diameter than the male threads formed on the outer circumferential surface <NUM>. The collar <NUM> serves as a screw head of the male thread structure (described below) provided on the outer circumference surface <NUM>. The second buffer member <NUM> includes multiple columnar through-holes <NUM> running from the front surface <NUM> on the leading end to the rear surface <NUM> on the trailing end. The through-holes <NUM> are an example of the communication hole that allows combustion gas (an example of the fluid) generated in the combustion chamber C to pass therethrough to supply the combustion gas to the pressure membrane 32a of the diaphragm head <NUM> by passing through.

As with the first buffer member <NUM>, the second buffer member <NUM> is made of a metal material (super heat-resistant alloy) with conductivity and higher heat resistance than the diaphragm head <NUM>. Examples of such metal materials include some kinds of iron-based, Gamma prime precipitation-strengthened super heat-resistant alloys. However, any of various other super heat-resistant alloys that satisfy the required characteristics may be employed. Examples of super heat-resistant alloys that can be used include matrix-reinforced super heat-resistant alloys, carbide precipitation-strengthened super heat-resistant alloys, and Gamma prime precipitation-strengthened super heat-resistant alloys. The super heat-resistant alloys that can be used may be iron-based alloys, nickel-based alloys, or cobalt-based alloys. The second buffer member <NUM> may be made of a copper alloy material with high thermal conductivity, such as a beryllium copper alloy (BeCu). Other choices than BeCu may include admiralty brass (JIS C4430), aluminum brass (JIS C6870), and naval brass (JIS C4640). The material of the first buffer member <NUM> and the material of the second buffer member <NUM> may or may not be the same.

As described above, of the first and second buffer members <NUM>, <NUM> constituting the buffer member <NUM>, the first buffer member <NUM> is provided with female threads on the inner circumferential surface <NUM>, and the second buffer member <NUM> is provided with the mating male threads on the outer circumferential surface <NUM>. This screw mechanism allows the second buffer member <NUM> to be separated from the first buffer member <NUM> and allows the separated second buffer member <NUM> to be threaded with the first buffer member <NUM> again (i.e., attachment and detachment of the second buffer member <NUM>).

With the first and second buffer members <NUM>, <NUM> threaded with each other, the front surface <NUM> of the first buffer member <NUM> is in a leading position relative to the front surface <NUM> of the second buffer member <NUM>. The central portion of the leading front surface of the buffer member <NUM>, which is defined by the second buffer member <NUM>, is circular and recessed, and the peripheral portion of the leading end surface, which is defined by the first buffer member <NUM>, is annular and protruding around the entire circumference. The central portion of the trailing rear surface of the buffer member <NUM>, which is defined by the second buffer member <NUM>, is circular and recessed, and the peripheral portion of the trailing rear surface, which is defined by the first buffer member <NUM>, is annular and protruding around the entire circumference.

Although not shown in the figures, the central portion defined by the second buffer member <NUM> may not be recessed in the leading front surface of the buffer member <NUM> formed by the threadably engaged first and second buffer members <NUM>, <NUM>; in other words, the central portion and the peripheral portion in the leading front surface of the buffer member <NUM> may lie flush with each other, or the central portion may be protruding and the peripheral portion may be recessed. Whether the central portion defined by the second buffer member <NUM> is to be recessed, flush with the peripheral portion, or protruding in the leading front surface of the buffer member <NUM> formed by the threadably engaged first and second buffer members <NUM>, <NUM> depends on the axial position of the second buffer member <NUM> threaded with the first buffer member <NUM>. In other words, it depends on at which axial position the second buffer member <NUM> screwed into the first buffer member <NUM> is to be secured. Securing of the second buffer member <NUM> screwed into the first buffer member <NUM> is described below.

In the present embodiment, the trailing rear surface <NUM> of the first buffer member <NUM> of the buffer member <NUM> and the front side annular protrusion <NUM> of the diaphragm head <NUM> are laser-welded and integrated at their interface around the entire outer circumference in the state where the rear surface <NUM> and the front side annular protrusion <NUM> are abutted together. Thus, in this example, the diaphragm head <NUM> and the first buffer member <NUM> are secured (welded) in contact with each other. However, the trailing rear surface <NUM> of the second buffer member <NUM> constituting the buffer member <NUM> is in a spaced-apart, confronting relationship to the pressure membrane 32a and the front side central recess 32b on the leading end of the diaphragm head <NUM>.

In the pressure detection device <NUM>, the rear surface <NUM> of the second buffer member <NUM> of the buffer member <NUM> confronts the pressure membrane 32a and the front side central recess 32b of the diaphragm head <NUM> with a predetermined gap. For this purpose, the first buffer member <NUM> is provided with the cut-away portion <NUM>, and the second buffer member <NUM> is provided with the collar <NUM>. With this configuration, as the second buffer member <NUM> is threaded into the first buffer member <NUM>, the collar <NUM> abuts the cut-away portion <NUM>, blocking a further screwing-in of the second buffer member <NUM>. This enables the diaphragm head <NUM> and the second buffer member <NUM> to confront each other with a predetermined gap. As a result, this prevents degradation of the function of the diaphragm head <NUM> that may otherwise be caused by the second buffer member <NUM> contacting the diaphragm head <NUM>.

With the pressure detection device <NUM> mounted on the cylinder head <NUM>, the first buffer member <NUM> is in contact with the inner wall of the communication hole 13a. By threading the male threads provided on the leading end external enclosure <NUM> of the pressure detection device <NUM> into the female threads on the communication hole 13a, the side wall of the leading end external enclosure <NUM> and the inner wall of the communication hole 13a are brought into contact with each other. The side wall of the leading end external enclosure <NUM> and the inner wall of the communication hole 13a are in contact with each other as well even in a configuration where the central portion defined by the second buffer member <NUM> in the leading end surface of the buffer member <NUM> formed by the threadably engaged first and second buffer members <NUM>, <NUM> is not recessed.

The relationship between the material of the buffer member <NUM> and the material of the diaphragm head <NUM> will now be described. In the present embodiment, each of the buffer member <NUM> and the diaphragm head <NUM> is made of an alloy material. However, the buffer member <NUM> and the diaphragm head <NUM> are made of different alloy materials. An iron-based alloy (steel) is preferably used for the buffer member <NUM> and the diaphragm head <NUM>. Stainless steel containing <NUM>% or more Cr is preferably used for the diaphragm head <NUM>. On the other hand, an iron-based alloy (super heat-resistant alloy) that is not stainless steel is preferably used for the buffer member <NUM>. A copper alloy may also be used for the buffer member <NUM>.

The alloy material of the buffer member <NUM> preferably has a thermal expansion coefficient that is comparable, more preferably identical, to that of the alloy material of the diaphragm head <NUM>. The use of a high thermal conductivity material, such as copper alloy, as the alloy material of the buffer member <NUM> is less likely to provide a match between the thermal expansion coefficients, but instead is expected to exhibit highly responsive endothermic characteristics with respect to steep temperature changes in the combustion gas.

As shown in <FIG>, the connecting cable <NUM> includes the twisted power line <NUM>, signal line <NUM>, and ground line <NUM>, and a cover member (not shown) that covers the outer periphery of these power line <NUM>, signal line <NUM>, and ground line <NUM>. Each of the power line <NUM>, the signal line <NUM>, and the ground line <NUM> includes a conductor portion made of tin-plated soft copper strands, and an insulating portion made of polyethylene (cross-linked polyethylene) or the like having a cross-liked structure reinforced with electron beams or the like. The insulating portion covers and insulates the outer periphery of the conductor portion. The cover member is made of an insulating rubber or resin material. The connecting cable <NUM> may be provided with a shielding element that shields the power line <NUM>, the signal line <NUM>, and the ground line <NUM>, if necessary.

Referring to <FIG>, a procedure for mounting the above configured pressure detection device <NUM> on the internal combustion engine <NUM> will now be described. First, the pressure detection device <NUM> is placed such that its leading end, i.e., the buffer member <NUM> confronts the communication hole 13a in the cylinder head <NUM> of the internal combustion engine <NUM> from outside the internal combustion engine <NUM>. Following this, the leading end of the pressure detection device <NUM> is inserted into the communication hole 13a.

Then, the pressure detection device <NUM> is rotated clockwise around the axial direction with respect to the cylinder head <NUM> of the internal combustion engine <NUM>. This operation is preferably performed with a torque wrench. This results in threaded engagement between the female threads on the inner circumferential surface of the communication hole 13a in the cylinder head <NUM> and the male threads on the outer circumferential surface of the leading end external enclosure <NUM> of the pressure detection device <NUM>, causing the pressure detection device <NUM> to be screwed into the cylinder head <NUM>. As a result, the buffer member <NUM> on the leading end of the pressure detection device <NUM> moves toward the combustion chamber C in the internal combustion engine <NUM>.

Along with such a screwing-in, the leading front surface <NUM> of the first buffer member <NUM> of the buffer member <NUM> in the pressure detection device <NUM> abuts the step 13b in the communication hole 13a of the cylinder head <NUM> in the internal combustion engine <NUM>. Also, the seating surface <NUM> of the overhang <NUM> of the leading end external enclosure <NUM> in the pressure detection device <NUM> abuts the step 13c in the communication hole 13a via the first sealing member <NUM>. As a result, the pressure detection device <NUM> essentially cannot be screwed in any further, but by retightening with a torque wrench, a predetermined axial force (fastening axial force) is applied to the pressure detection device <NUM> and the cylinder head <NUM> along the axial direction.

In the pressure detection device <NUM> of the present embodiment, the first sealing member <NUM> is made of a material with greater elasticity than the buffer member <NUM>, so that the first sealing member <NUM> is deformed in response to abutment between the step 13c and the pressure detection device <NUM>. Therefore, the position of the pressure detection device <NUM> relative to the communication hole 13a depends on abutment between the step 13b and the buffer member <NUM>. The buffer member <NUM> is configured such that the front surface <NUM> of the first buffer member <NUM> is in a leading position relative to the front surface <NUM> of the second buffer member <NUM> when the first and second buffer members <NUM>, <NUM> are threaded with each other. As such, of the portions of buffer member <NUM>, only the first buffer member <NUM> contacts the communication hole 13a. Thus, the second buffer member <NUM>, which is another constituent of the buffer member <NUM>, is not subjected to the axial force for mounting the pressure detection device <NUM> on the internal combustion engine <NUM>. When the cylinder head <NUM> is not provided with the step 13b, the axial force is applied by the seating surface <NUM> of the overhang <NUM> and the threaded portion. The above completes the mounting of the pressure detection device <NUM> on the internal combustion engine <NUM>, or in other words, the fastening of the pressure detection device <NUM> to the cylinder head <NUM>.

The pressure detection operation by the pressure detection device <NUM> will now be described. During operation of the internal combustion engine <NUM>, the pressure generated in the combustion chamber C (combustion pressure) is applied to the pressure membrane 32a of the diaphragm head <NUM>. In the pressure detection device <NUM> of the present embodiment, the buffer member <NUM> is provided on the leading end of the diaphragm head <NUM>, so that the combustion gas generated in the combustion chamber C passes through the through-holes <NUM> in the second buffer member <NUM> of the buffer member <NUM> before reaching the pressure receiving portion of the diaphragm head <NUM> (the pressure membrane 32a and the front side central recess 32b). In other words, the buffer member <NUM> receives the combustion gas, reduces its temperature during its passing through the through-holes <NUM>, and supplies the temperature-reduced combustion gas to the diaphragm head <NUM>.

Meanwhile, in the diaphragm head <NUM>, the pressure received at the pressure receiving portion is transmitted to the opposite, rear side central protrusion 32d, and further from the rear side central protrusion 32d to the leading end electrode member <NUM> via the leading end insulating member <NUM>. The pressure transmitted to the leading end electrode member <NUM> acts on the piezoelectric element <NUM> held between the leading end electrode member <NUM> and the trailing end electrode member <NUM>, and the piezoelectric element <NUM> generates an electric charge according to the pressure received. The electric charge generated in the piezoelectric element <NUM> is supplied as a charge signal from the leading end electrode member <NUM> or the trailing end electrode member <NUM> to the circuit board <NUM> via the conductive elements such as the conducting member <NUM> or the second coil spring <NUM>. The charge signal supplied to the circuit board <NUM> undergoes various processes in processing circuitry (not shown) mounted on the circuit board <NUM> to yield an output signal. The output signal from the circuit board <NUM> is then transmitted to the controller via the wires and terminals of the connecting member <NUM> and the connecting cable <NUM>.

The combustion gas generated in the combustion chamber C has its heat taken away by the buffer member <NUM> as it passes through the through-holes <NUM> in the second buffer member <NUM> of the buffer member <NUM>. As such, the combustion gas having passed through the buffer member <NUM> has a lower temperature than it had before passing through the buffer member <NUM>. Specifically, the temperature of the combustion gas reaching the pressure receiving portion of the diaphragm head <NUM> can be reduced by, for example, <NUM> or more as compared to when the pressure detection device <NUM> is not provided with the buffer member <NUM>.

<FIG> illustrates accumulation of incomplete combustion products (hereinafter referred to as "deposits") on the buffer member <NUM> of the pressure detection device <NUM>. <FIG> illustrates removal of the second buffer member <NUM> from the pressure detection device <NUM>.

After a certain period of use of the pressure detection device <NUM>, deposits <NUM> accumulate on the surfaces of the buffer member <NUM> and the pressure receiving portion (the pressure membrane 32a and front side central recess 32b) of the diaphragm head <NUM>. In particular, the deposits are more likely to accumulate in and around the through-holes <NUM>, through which the combustion gas generated in the combustion chamber C passes. The deposits <NUM> are periodically removed by an operator because the accumulation of the deposits <NUM> may inhibit accurate pressure measurement by the pressure detection device <NUM>.

As described above, the pressure detection device <NUM> of the present embodiment allows for detachment of the second buffer member <NUM> including the through-holes <NUM> in which the deposits <NUM> are more likely to accumulate. Thus, the operator periodically removes only the second buffer member <NUM> from the pressure detection device <NUM>. Specifically, the operator removes the second buffer member <NUM> threaded with the first buffer member <NUM> by rotating the second buffer member <NUM> circumferentially in the screwing-out direction, and washes off the deposits <NUM> adhering to the second buffer member <NUM>. The operator then attaches the second buffer member <NUM>, from which the deposits have been removed, to the pressure detection device <NUM>. Specifically, the operator aligns the male threads on the outer circumferential surface <NUM> of the second buffer member <NUM> with the female threads on the inner circumferential surface <NUM> of the first buffer member <NUM>, and rotates the second buffer member <NUM> circumferentially in the screwing-in direction for threaded engagement. The operator then mounts the pressure detection device <NUM> on the cylinder head <NUM> in the manner described above.

Depending on the usage of the pressure detection device <NUM>, the second buffer member <NUM> threaded with the first buffer member <NUM> in the buffer member <NUM> may, for some reason, be unintentionally rotated circumferentially in the screwing-out direction. This leads to a displacement of the axial position of the second buffer member <NUM> relative to the first buffer member <NUM>, with a consequent risk of dislodgement of the second buffer member <NUM> from the first buffer member <NUM>. Therefore, the buffer member <NUM> may be provided with a securing mechanism for securing the second buffer member <NUM> threaded with the first buffer member <NUM>.

<FIG> is a perspective view of an example outer configuration of the buffer member <NUM> including screws <NUM> for securing the second buffer member <NUM> threaded with the first buffer member <NUM> to the first buffer member <NUM>. <FIG> is a cross-sectional perspective view of the buffer member <NUM> of <FIG> taken in the radial direction. While <FIG> shows an example where two screws <NUM> are provided, <FIG> does not show one of the two screws <NUM> for clarity of illustration. <FIG> is a cross-sectional view of the buffer member <NUM> of <FIG> taken in the radial direction.

The buffer member <NUM> shown in <FIG> includes a combination of threaded holes formed in threaded engagement portions between the first and second buffer members <NUM>, <NUM> and the screws <NUM> threaded into the respective threaded holes, as an example of the securing mechanism for securing of the second buffer member <NUM> threaded with the first buffer member <NUM>.

The threaded holes for screwing in of the respective screws <NUM> are formed in the axial direction of the first and second buffer members <NUM>, <NUM>. Specifically, the threaded holes extending in the axial direction are each formed in the portion including respective portions of the leading front surface <NUM> and the inner circumferential surface <NUM> of the first buffer member <NUM> and a portion of the second buffer member <NUM>. Of these, a portion of each threaded hole that is formed in the first buffer member <NUM> defines a cut-away portion <NUM> that mates with a portion of a head <NUM> of the screw <NUM> threaded into the threaded hole.

Upon screwing in of the screw <NUM> for securing the second buffer member <NUM> into the threaded engagement portion between the first and second buffer members <NUM>, <NUM>, a portion of the head <NUM> of the screw <NUM> mates with the cut-away portion <NUM>, whereby a threaded portion <NUM> of the screw <NUM> is disposed to lie across the first and second buffer members <NUM>, <NUM>. As a result, the head <NUM> of the screw <NUM> mated with the cut-away portion <NUM> and the threaded portion <NUM> disposed to lie across the first and second buffer members <NUM>, <NUM> serve as a wedge to prevent unintentional circumferential rotation of the second buffer member <NUM>. This in turn prevents displacement of the second buffer member <NUM> in the axial direction and dislodgement of the second buffer member <NUM>. In the example shown in <FIG>, two securing mechanisms each composed of the screw <NUM> and the threaded hole for screwing in of the screw <NUM> are disposed at opposite positions across the centerline. The number of securing mechanisms is not limited to two as in this example, and may be one or more than two. When providing multiple securing mechanisms, they are preferably disposed symmetrically with respect to the central axis of the second buffer member <NUM>. For example, when providing three securing mechanisms, the securing mechanisms are disposed at intervals of <NUM> degrees in the circumferential direction of the buffer member <NUM> around the central axis. When providing four securing mechanisms, the securing mechanisms are disposed at intervals of <NUM> degrees in the circumferential direction of the buffer member <NUM> around the central axis.

<FIG> illustrate variations in the shape of the head <NUM> of the screw <NUM>.

The screws <NUM> shown in <FIG> above are screws that are generally cylindrical and include the disk-shaped head <NUM>. However, screws of other shapes may be employed, provided that they satisfy the characteristics required as a securing mechanism for securing the second buffer member <NUM> threaded with the first buffer member <NUM>.

For example, <FIG> show a plan view and a front view, respectively, of an example outer configuration of the screw <NUM> with a cylindrical head <NUM>. <FIG> show a plan view and a front view, respectively, of an example outer configuration of the screw <NUM> with a head <NUM> whose side is inclined with respect to the longitudinal direction of the screw <NUM>. The use of the screw <NUM> with a cylindrical head <NUM> as a securing mechanism can, by virtue of such a cylindrical shape of the head <NUM>, prevent entry of combustion gas into the threaded hole and consequent sticking of the screw <NUM> more effectively than using the screw <NUM> with a head <NUM> whose side is inclined with respect to the longitudinal direction of the screw <NUM>.

<FIG> is a perspective view of an example outer configuration of the buffer member <NUM> including screws <NUM> for securing the second buffer member <NUM> threaded with the first buffer member <NUM> to the first buffer member <NUM>. <FIG> is a front view of the example outer configuration of the buffer member <NUM> of <FIG> is a cross-sectional view of the buffer member <NUM> of <FIG>, taken in the radial direction.

The buffer member <NUM> shown in <FIG> includes a combination of threaded holes formed in the threaded engagement portions between the first and second buffer members <NUM>, <NUM> and screws <NUM> threaded with the respective threaded holes, as an example of the securing mechanism for securing the second buffer member <NUM> threaded with the first buffer member <NUM>.

The threaded holes for screwing in of the respective screws <NUM> are formed in a direction perpendicular to the axial direction of the first and second buffer members <NUM>, <NUM>. Specifically, the threaded holes <NUM> extending radially relative to the axial direction in the axial direction are each formed in the portion including respective portions of the outer circumferential surface <NUM> and the inner circumferential surface <NUM> of the first buffer member <NUM> and a portion of the outer circumferential surface <NUM> of the second buffer member <NUM>. Of these, a portion of each threaded hole <NUM> that is formed in the inner circumferential surface <NUM> of the first buffer member <NUM> defines a cut-away portion <NUM> that mates with a portion of the screw <NUM> threaded into the threaded hole <NUM>. Also, a portion of each threaded hole <NUM> that is formed in the second buffer member <NUM> defines a cut-away portion <NUM> that mates with a portion of the screw <NUM> threaded into the threaded hole <NUM>.

In the example shown in <FIG>, two securing mechanisms each composed of the screw <NUM> and the threaded hole <NUM> for screwing in of the screw <NUM> are disposed at opposite positions across a predetermined plane that is parallel to and includes the centerline. However, the number of securing mechanisms is not limited to two as in this example, and may be one or more than two. For example, when providing three securing mechanisms, the respective threaded holes <NUM> are provided at three equally spaced-apart circumferential positions on the outer circumferential surface <NUM> of the first buffer member <NUM>. Also, when providing four securing mechanisms, the respective threaded holes <NUM> are preferably provided at four equally spaced-apart circumferential positions on the outer circumferential surface <NUM> of the first buffer member <NUM> for arrangement of these securing mechanisms.

Upon screwing in of the screw <NUM> for securing the second buffer member <NUM> into the threaded engagement portion between the first and second buffer members <NUM>, <NUM>, a portion of the screw <NUM> mates with the cut-away portion <NUM> of the first buffer member <NUM> and the cut-away portion <NUM> of the second buffer member <NUM>. As a result, the portion of the screw <NUM> mated with the cut-away portion <NUM> of the first buffer member <NUM> and the cut-away portion <NUM> of the second buffer member <NUM> serve as a wedge to prevent unintentional circumferential rotation of the second buffer member <NUM>. This in turn prevents dislodgement of the second buffer member <NUM> resulting from unintentional circumferential rotation of the second buffer member <NUM>. Additionally, when the threaded holes <NUM> are provided in a direction perpendicular to the axial direction, the threaded holes <NUM> will be located farther away from the combustion chamber C of the internal combustion engine <NUM> than when the threaded holes are provided in the axial direction as in the example in <FIG> described above. As such, the threaded holes <NUM> are not directly exposed to the combustion gas from the combustion chamber C. This reduces the risk of deformation or damage otherwise caused by repeated thermal expansion and contraction of the screws <NUM>, as well as accumulation of the deposits in the threaded holes <NUM>.

The screw <NUM> shown in <FIG> is a so-called set screw that has a cylindrical shape with no clear distinction between the head and the body. The screw <NUM> includes a face <NUM> on its one longitudinal end for receiving a jig such as a hexagonal wrench, and a face <NUM> on its other longitudinal end. The screw <NUM> also includes an outer circumferential surface <NUM>. The outer circumferential surface <NUM> is provided with male threads (not shown). The inner wall of the threaded hole <NUM> is provided with female threads (not shown) that can threadably engage the above male threads on the outer circumferential surface <NUM>.

The entire screw <NUM> is threaded into the threaded hole <NUM>, with no part of the screw <NUM> protruding outward from the entrance of the threaded hole <NUM>. This prevents the inner wall of the communication hole 13a of the internal combustion engine <NUM> from being damaged by the screw head otherwise protruding from the outer circumferential surface <NUM> of the buffer member <NUM> when mounting the pressure detection device <NUM> on the internal combustion engine <NUM>. Since the threaded holes <NUM> are provided in the outer circumferential surface <NUM> of the first buffer member <NUM> in the example of <FIG>, the sealing between the screw <NUM> and the threaded hole <NUM> may be disadvantageously reduced, compared to the example using the headed screw as in Modification <NUM> shown in <FIG> above. However, the use of a small-diameter set screw as the screw <NUM> can reduce the risk of such reduced sealing.

As described above, the present embodiment enables the detachment of the second buffer member <NUM>, making it possible to efficiently remove the deposits adhering to the second buffer member <NUM>. However, depending on the circumstances, the deposits adhering to the second buffer member <NUM> may accumulate and get stuck, which may prevent the second buffer member <NUM> from being rotated well circumferentially in the screwing-out direction.

<FIG> are perspective views of an example outer configuration of the buffer member <NUM> that allows the second buffer member <NUM> to be rotated using a jig.

The second buffer member <NUM> of the buffer member <NUM> shown in <FIG> is provided on its leading front surface <NUM> with two radially extending straight grooves <NUM> perpendicular to each other. The grooves <NUM> can receive a jig <NUM> such as a flathead screwdriver. An operator uses the jig <NUM> to scrape off the deposits until the grooves <NUM> are exposed, and then inserts the jig <NUM> into at least one of the exposed grooves <NUM>. This makes it easier to rotate the second buffer member <NUM> in the circumferential direction.

As described above, the present embodiment enables the detachment of the second buffer member <NUM>, making it possible to efficiently remove the deposits adhering to the second buffer member <NUM>. However, depending on the circumstances, even when the second buffer member <NUM> is removed from the first buffer member <NUM>, the through-holes <NUM> may be clogged with deposits, which may be hard to remove even by washing.

<FIG> are perspective views of an example outer configuration of the second buffer member <NUM> that can be separated into multiple sub-members and assembled from the separated multiple sub-members.

<FIG> shows the second buffer member <NUM> as formed by combining multiple sub-members. <FIG> shows the second buffer member <NUM> as separated into multiple sub-members.

The second buffer member <NUM> shown in <FIG> is formed of combinable sub-members <NUM>-<NUM> through <NUM>-<NUM>. Specifically, the sub-member <NUM>-<NUM> is combined with the sub-members <NUM>-<NUM> and <NUM>-<NUM> via joining surfaces <NUM>, and the sub-member <NUM>-<NUM> is combined with the sub-members <NUM>-<NUM> and <NUM>-<NUM> via the joining surfaces <NUM>. The sub-member <NUM>-<NUM> is combined with the sub-members <NUM>-<NUM> and <NUM>-<NUM> via the joining surfaces <NUM>, and the sub-member <NUM>-<NUM> is combined with the sub-members <NUM>-<NUM> and <NUM>-<NUM> via the joining surfaces <NUM>. These combinations result in the second buffer member <NUM>.

The joining surfaces <NUM> are ones of the surfaces forming each of the sub-members <NUM>-<NUM> through <NUM>-<NUM> that are provided with a recess 827a and a protrusion 827b that are mated during assembly. When assembling the multiple separated sub-members, the recesses 827a and the corresponding protrusions 827b are mated, permitting assembly without misalignment. This also permits assembly without considering the individual positions of the multiple sub-members.

Thus, the second buffer member <NUM> shown in <FIG> can be separated into the sub-members <NUM>-<NUM> through <NUM>-<NUM>, which facilitates the removal of deposits adhering to the second buffer member <NUM>. In addition, the separated sub-members <NUM>-<NUM> through <NUM>-<NUM> can be assembled via the joining surfaces <NUM>, so that after removing the deposits via separation into the sub-members <NUM>-<NUM> through <NUM>-<NUM>, the sub-members <NUM>-<NUM> through <NUM>-<NUM> can be reassembled and used again as the second buffer member <NUM>. The sub-members <NUM>-<NUM> through <NUM>-<NUM> can have the same shape. This eliminates the need for considering assembly counterparts during assembly. This also facilitates replacement due to damage, etc..

In summary, the pressure detection device <NUM> according to some embodiments of the present invention may be at least configured as follows, and may be implemented in a variety of embodiments.

That is, the pressure detection device <NUM> according to some embodiments of the present invention comprises: a body (enclosure assembly <NUM>) configured to be mounted in a communication hole 13a in an internal combustion engine <NUM>; a pressure receiving member (diaphragm head <NUM>) provided at one end of the body and configured to receive pressure of a fluid (combustion gas) from the internal combustion engine <NUM>; and a temperature reducing member (buffer member <NUM>) located at the pressure receiving member on a leading end at the one end of the body and configured to supply the fluid to the pressure receiving member while reducing temperature of the fluid. The pressure receiving member comprises: a pressure receiving portion (pressure membrane (front surface) 32a and front side central recess 32b) configured to be displaced under pressure; and a pressure receiving support portion (front side annular protrusion <NUM>) threaded or integrally molded with a first member (first buffer member <NUM>), the first member being joined to or integrally molded with the pressure receiving member and including an inner circumferential surface <NUM>. The temperature reducing member comprises: the first member; and a second member (second buffer member <NUM>) having an outer circumferential surface <NUM> facing the inner circumferential surface <NUM>. Female threads formed on the inner circumferential surface <NUM> of the first member and male threads formed on the outer circumferential surface <NUM> of the second member are configured to threadably engage each other.

Since the temperature reducing member that supplies the fluid from the internal combustion engine <NUM> to the pressure receiving member is composed of the first member joined to or integrally molded with the pressure receiving member and the second member threaded with the first member, the second member is detachable. This facilitates removal of the deposits <NUM> adhering to the temperature reducing member. In addition, in the configuration where the axial force is not applied to the second member when it is threaded with the first member, the effect of the attachment/detachment of the second member on the sealing between the pressure detection device and the internal combustion engine can be reduced.

Such integral molding of the first member and the pressure receiving support portion increases the sealing between the first member and the pressure receiving support portion.

The second member may comprise a plurality of communication holes (through-holes <NUM>) configured to allow the fluid to be supplied to the pressure receiving portion.

The deposits <NUM> are more likely to accumulate in the communication holes of the second member, which is detachable by virtue of the screw mechanism. Thus, the second member can be removed and washed, etc., to remove the deposits efficiently.

Disposing the second member threaded with the first member at a position where it does not contact the pressure receiving member can prevent the degradation of the function of the pressure receiving member that may otherwise be caused by the second member contacting the pressure receiving member.

Securing the second member threaded with the first member can prevent unintentional dislodgement of the second member.

The securing mechanism may comprise a combination of a threaded hole formed in a threaded engagement portion between the first member and the second member and a screw (e.g., screws <NUM>, <NUM>) configured to be threaded into the threaded hole.

This configuration, where the screw for securing the second member is threaded into the threaded engagement portion between the first and second members, can prevent the dislodgement of the second member that may otherwise result from unintentional rotation of the second member.

The threaded hole may be formed in the axial direction of the first member and the second member, and the first member may comprise a cut-away portion configured to mate with a portion of a head <NUM> of the screw (e.g., screw <NUM>) threaded into the threaded hole.

This configuration, where the first member includes a cut-away portion that mates with a portion of the head <NUM> of the screw of the securing mechanism, can prevent the dislodgement of the second member that may otherwise result from unintentional rotation of the second member.

The head <NUM> of the screw may be of a cylindrical shape (e.g., screw <NUM> in <FIG>).

By virtue of the screw as the securing mechanism having the cylindrical head <NUM>, entry of the supplied fluid into the threaded hole can be blocked more effectively than when the screw has a head <NUM> whose side is inclined with respect to the longitudinal direction of the screw (e.g., screw <NUM> in <FIG>).

The threaded hole may be formed in a direction perpendicular to the axial direction of the first member and the second member (e.g., threaded hole <NUM> in <FIG>).

With this configuration, where the threaded hole of the securing mechanism is provided in a direction perpendicular to the axial direction of the first and second members, the threaded hole is located farther from the combustion chamber of the internal combustion engine than when the threaded hole is provided in the axial direction of the first and second members (for example, the threaded hole into which the screw <NUM> is threaded in <FIG>). This reduces the risk of deformation or damage otherwise caused by repeated thermal expansion and contraction of the screw, as well as accumulation of the deposits in the threaded hole.

The head of the screw (e.g., part of screw <NUM> in <FIG>) threaded into the threaded hole may be configured not to protrude from an entrance of the threaded hole (e.g., threaded hole <NUM> in <FIG>).

This configuration, where the head of the screw threaded into the threaded hole of the securing mechanism does not protrude outward from the opening of the screw hole, can prevent the inner wall of the hole in the internal combustion engine from being damaged by the screw head when mounting the pressure detection device on the internal combustion engine.

The second member may comprise at least one straight groove <NUM> on its leading end surface.

This configuration, where a straight groove <NUM> is provided on the leading end surface of the second member prone to accumulation of the deposits <NUM>, facilitates scraping off the deposits <NUM> by insertion of a jig <NUM> into the groove <NUM>.

The second member may be configured to be separated into a plurality of sub-members (e.g., sub-members <NUM>-<NUM> through <NUM>-<NUM>) and assembled from the plurality of separated sub-members.

This configuration, where the second member can be separated into multiple sub-members, facilitates removal of the deposits <NUM> adhering to the second member. In addition, this configuration allows for assembling the separated multiple sub-members together, which allows them to be reassembled and used again as the second member after removal of the deposits <NUM> via separation into the multiple sub-members.

Each of the separated multiple sub-members may comprise a recess and a protrusion (e.g., joining surfaces <NUM> in <FIG>) used for mating during assembly.

When assembling the multiple separated sub-members, the recess and the corresponding protrusion are mated, permitting assembly without misalignment. This configuration also permits assembly without considering the individual positions of the multiple sub-members.

In the above embodiment, nineteen cylindrical through-holes <NUM> are provided in the second buffer member <NUM> of the buffer member <NUM>. However, this is not limiting. In other words, the shape, number, dimensions, and arrangement of the through-holes <NUM> may be modified as needed, provided that the buffer member <NUM> can reduce the temperature of the combustion gas as it passes through the buffer member <NUM>.

In <FIG>, the cross-head screws as the screws <NUM> are disposed at two opposing positions across the centerline. However, this is not limiting. In other words, the shape, dimensions, and arrangement of the screws <NUM> can be modified as needed, provided that the screws <NUM> can serve as the securing mechanism. For example, the screw <NUM> may be a set screw with a hexagonal bore, rather than the cross-head screw. When configured as a set screw with a hexagonal bore, the screw can have a reduced head diameter.

<FIG> illustrates the second buffer member <NUM> as being separated into the four sub-members. However, this is not limiting. In other words, the second buffer member <NUM> separated into any n sub-members (where n is an integer of two or greater) can be employed, as it is only required to be capable of being separated into multiple sub-members and assembled therefrom.

In the above embodiment, the central portion defined by the second buffer member <NUM> in the trailing rear surface of the buffer member <NUM> as formed by the threaded engagement of the first and second buffer members <NUM>, <NUM> is recessed. However, this is not limiting. In other words, the central portion defined by the second buffer member <NUM> in the trailing rear surface of the buffer member <NUM> as formed by the threaded engagement of the first and second buffer members <NUM>, <NUM> may not be recessed, or in other words, the central portion and the peripheral portion in the trailing rear surface of the buffer member <NUM> may lie flush with each other.

Although the present embodiment has been described above, the technical scope of the present invention is not limited to the above described embodiment. Various modifications and configuration alternatives that do not depart from the scope of the technical concept of the present invention are encompassed by the present invention as defined by the appended claims. While the above embodiment discussed employing the piezoelectric element <NUM> in the detection mechanism assembly <NUM> of the pressure detection device <NUM>, the configuration of the detection mechanism assembly <NUM> may be replaced with any of various conventionally known detection mechanisms. For example, a strain gauge or the like may be used instead of the piezoelectric element <NUM>. When using a strain gauge, it is necessary to provide the pressure detection device with a power line for power supply to the strain gauge, in addition to the components in the above embodiment.

Claim 1:
A pressure detection device (<NUM>) comprising:
a body (<NUM>) configured to be mounted in a hole (13a) in an internal combustion engine (<NUM>);
a pressure receiving member (<NUM>) provided at one end of the body (<NUM>) and configured to receive pressure of a fluid from the internal combustion engine (<NUM>); and
a temperature reducing member (<NUM>) located at the pressure receiving member (<NUM>) on a leading end at the one end of the body (<NUM>) and configured to supply the fluid to the pressure receiving member (<NUM>) while reducing temperature of the fluid, wherein
the pressure receiving member (<NUM>) comprises:
a pressure receiving portion (32a, 32b) configured to be displaced under pressure; and
a pressure receiving support portion (<NUM>) joined to or integrated with a first member (<NUM>), the first member (<NUM>) being joined to or integrated with the pressure receiving member (<NUM>) and having an inner circumferential surface (<NUM>),
the temperature reducing member (<NUM>) comprises:
the first member (<NUM>); and
a second member (<NUM>) having an outer circumferential surface (<NUM>) facing the inner circumferential surface (<NUM>),
characterized in that
female threads formed on the inner circumferential surface (<NUM>) of the first member (<NUM>) and male threads formed on the outer circumferential surface (<NUM>) of the second member (<NUM>) are configured to threadably engage each other.