JPH04290938A - Pressure sensing device - Google Patents

Abstract

PURPOSE:To obtain the output of a pressure-sensitive element which is temp. compensated properly using a relatively simple constitution by equipping the pressure-sensitive element with a resistance value which varies with changing temp. and changing outer pressure. CONSTITUTION:A pressure sensing device according to the invention comprises a pressure-sensitive element 39 which is formed linearly and whose resistance value varies with changing temp. and changing outer pressure, No.1 and No.2 insulating members 35, 37 which have different coefficient of thermal expansion from that of the pressure-sensitive element 39 and which assume a condition contacting so as to give outer pressure to the element 39 and thereby generate therein such a shape change as to set off the change of the resistance value originating from temp. change, and a sensing output forming part 34 to generate in the element 39 a sensing output corresponding to the change of the resistance value resulting from change of the outer pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detection device using a linear pressure sensing element that changes its resistance value in response to changes in external pressure.

0002

[Prior Art] In an engine mounted on a vehicle, a cylinder head is joined to a cylinder block, which is a main component of the engine. A gasket is interposed between the mutually opposing surfaces of the parts, and the parts are bolted together. The gasket is formed with openings corresponding to each of the cylinder bore and various passages provided in the cylinder block, and seals each of the cylinder bore and various passages at the joint between the cylinder block and the cylinder head.

[0003] It is particularly desirable that the gasket disposed at the joint between the cylinder block and cylinder head in such an engine maintain a good sealing condition for the cylinder bore in the cylinder block. , the peripheral part of the opening to the cylinder bore is,
Regardless of fluctuations in the combustion pressure within the combustion chamber formed in the upper part of the cylinder bore at the joint between the joined cylinder block and cylinder head, it is possible to reliably seal the mutually opposing surfaces of the cylinder block and cylinder head. is required. Therefore, even under conditions where the maximum combustion pressure in the combustion chamber that acts on the cylinder block and cylinder head in a direction that separates them from each other is sufficiently high, the gasket has an opening corresponding to the cylinder bore. The material, structure, etc. of the peripheral portion of the cylinder block are selected so that a surface pressure of a predetermined value or more can be applied to each of the mutually opposing surfaces of the cylinder block and the cylinder head. Conventionally, as such a gasket, an asbestos gasket whose main component is an asbestos plate-like member, for example, the asbestos gasket manufactured in 1983
As shown in Japanese Patent Publication No. 74158, there are known metal gaskets whose main component is a metal laminate plate member formed by overlapping a plurality of metal plate bodies. Stronger than gaskets,
It has excellent properties such as rigidity.

On the other hand, metal gaskets deform to follow the change in the distance between the opposing surfaces of the cylinder block and cylinder head due to fluctuations in the combustion pressure in the combustion chamber, resulting in the sealing state of the cylinder bore in the cylinder block. It is disadvantageous compared to asbestos gaskets in terms of flexibility to maintain Therefore, when using a metal gasket, the surface pressure received from each of the mutually opposing surfaces of the cylinder block and cylinder head is detected in advance, and it is determined whether the detected surface pressure is equal to or higher than a predetermined value. In order to detect the surface pressure acting on such a metal gasket, it is desirable to use an extremely thin,
Additionally, there is a need for a pressure detection device that includes a pressure sensing portion that does not affect the external pressure acting on the metal gasket.

[0005]

[Problem to be Solved by the Invention] An extremely thin pressure sensitive part that can be used to detect surface pressure acting on such a metal gasket and does not affect external pressure acting on the metal gasket. The pressure sensing device that has been proposed so far has a pressure sensing part formed by a pressure sensing element made of a metal material whose resistance value changes according to changes in external force, and the pressure sensing device detects pressure based on the output from the pressure sensing element. There is something that gets the output. However, a pressure-sensitive element made of a metal material whose resistance value changes in response to external force has a resistance value that changes not only in response to a change in external force acting on it, but also in response to a change in temperature. In order to obtain a pressure detection output based on the output obtained from the pressure sensing element, temperature compensation processing is required for the output obtained from the pressure sensitive element.

[0006] Therefore, a pressure detection device equipped with a pressure sensing element made of such a metal material is used, and the pressure sensing element is attached to a gasket disposed at the joint between the cylinder block and the cylinder head. When the surface pressure acting on the pressure sensitive element is detected, the temperature of the pressure sensitive element will be changed according to the temperature change of the gasket, so the temperature compensation process for the output obtained from the pressure sensitive element is The problem is that it is complicated to deal with temperature changes, and it is difficult to obtain a highly accurate temperature compensation effect.

In view of the above, the present invention uses a pressure sensitive element whose resistance value changes according to changes in external pressure and temperature, and in obtaining a pressure detection output based on the output obtained from the pressure sensitive element, It is an object of the present invention to provide a pressure detection device having a relatively simple configuration, in which the output obtained from a pressure sensitive element is subjected to appropriate temperature compensation.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the pressure detection device according to the present invention is formed into a linear body, and the resistance value changes according to changes in external pressure and temperature. A pressure-sensitive element, an insulating member that has a coefficient of linear expansion different from that of the pressure-sensitive element and comes into contact with the pressure-sensitive element in order to apply an external pressure to the pressure-sensitive element, and a change in resistance value due to a change in external pressure on the pressure-sensitive element. and a detection output forming section that generates a detection output corresponding to the pressure sensing element, and the insulating member is configured to cause the pressure sensitive element to undergo a shape change that cancels a change in resistance value due to a temperature change.

[0009]

[Operation] In the pressure sensing device according to the present invention configured as described above, the pressure sensing element is formed into a linear body, so that the pressure sensing element and the insulation that come into contact with it are formed. The part including the member has a small overall thickness, so that it can be easily attached to, for example, a gasket disposed at the joint between the cylinder block and cylinder head of an engine, and is substantially free from external pressure acting on the gasket. It is assumed that there will be no significant impact. Additionally, when the pressure-sensitive element attempts to reduce or increase its resistance value due to temperature changes,
The insulating member that comes into contact with the pressure-sensitive element expands or contracts in response to temperature changes, changing the pressure applied to the pressure-sensitive element, thereby changing the thickness and length of the pressure-sensitive element, and creating a pressure-sensitive element. This acts to cancel out the reduction or increase in resistance value caused by temperature changes in the element. As a result, the detection output obtained from the pressure-sensitive element is subjected to appropriate temperature compensation, and is made to appropriately correspond to changes in resistance value caused by changes in external pressure acting on the pressure-sensitive element.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show an example of a pressure detection device according to the present invention together with a metal gasket to which it is applied.

The metal gaskets 1 shown in FIGS. 1 and 2 are arranged between mutually opposing surfaces of a cylinder block and a cylinder head, which are the main components of an engine, and are arranged and formed on the cylinder block. A combustion chamber opening 3 having approximately the same diameter as the cylinder bore is formed at a position corresponding to each of the plurality of cylinder bores, and a combustion chamber opening 3 is formed at one end along the arrangement direction of the plurality of combustion chamber openings 3. A plurality of head bolt through holes 6 and one lubricating oil supply passage through hole 8 are provided, and a plurality of head bolt through holes 6 and three lubricating oil return passage through holes 9 are provided at the other end edge. In addition, a plurality of through holes for cooling water passages each having a relatively small diameter are provided at positions surrounding the combustion chamber opening 3.

As shown in FIG. 1, the entire metal gasket 1 consists of relatively thin first and second plate members 11 and 1 made of a metal material such as stainless steel.
The outer surface of the first plate member 11 and the second plate member 11 are made of a laminated metal plate member formed by overlapping the first plate member 11 and the second plate member 11 when placed at the joint between the cylinder block and the cylinder head. The outer surfaces of the shaped members 12 are in contact with mutually opposing surfaces of the cylinder head and cylinder block, respectively. An annular grommet portion 15 that surrounds the combustion chamber opening 3 is provided around each combustion chamber opening 3 in such a metal gasket 1 . In the grommet portion 15, the portion of the second plate member 12 that forms the combustion chamber opening 3 is the same as that of the first plate member 11.
It is formed by being folded back to the outer surface side of the holder to form a U-shaped bent part.

Further, the outer peripheral edge portion of the first plate member 11, the position surrounding each of the head bolt through holes 6, the position surrounding the lubricating oil supply passage through hole 8, and each lubricating oil return passage. At the position surrounding each of the through holes 9, respectively,
A bead portion 16 is provided as a relatively small raised portion, and the bead portion 16 provided on the outer peripheral edge portion of the first plate member 11 is continuous so as to form an annular body as a whole. It is said that Further, around each of the grommet parts 15 in the first plate member 11, an annular bead part 20 which is a raised part larger than the bead part 16 is provided to surround the grommet part 15.

For the metal gasket 1 constructed as described above, an example of the pressure detection device according to the present invention is installed corresponding to each of the four combustion chamber openings 3, as shown in FIG. A pressure detection device 30 is provided. Each of these four pressure detection devices 30 includes a pressure sensing section 33 located on the outer surface of the first plate member 11 in the metal gasket 1 and a detection output forming section 34 connected to the pressure sensing section 33.
It is said to include. As shown in FIGS. 1 and 2, the pressure sensitive parts 33 are each formed into a thin film shape, and are overlapped to form the first plate member 11 in the metal gasket 1.
first and second insulating members 35 and 37 arranged corresponding to the combustion chamber opening 3 on the outer surface of the combustion chamber, and sandwiched between the first insulating member 35 and the second insulating member 37 bead part 2
0 and a pressure sensitive element 39 made of a metal material and formed into a linear body.

The first and second insulating members 35 and 37 are
Each synthetic resin material has a predetermined coefficient of linear expansion and a relatively small thickness, for example, 60 to 65 x 10-6 cm/
It is made of a polyimide resin material having a linear expansion coefficient of °C and a thickness of 25 μm, and passes from the grommet part 15 surrounding the combustion chamber opening 3 to the bead part 20 surrounding the grommet part 15. It is arranged so as to extend to the peripheral edge portion of the first plate member 11. Pressure sensitive element 39
is the linear expansion coefficient of the first and second insulating members 35 and 37.
The bead portion 20 is made of a smaller metal material, such as manganin, and has a relatively small thickness, for example, 25 μm, and surrounds the grommet portion 15.
It extends in the direction along. Both ends of the pressure sensitive element 39 in the direction along the bead portion 20 are connected to the detection output forming portion 34 through a pair of lead wires 41 and 43 that protrude and extend from the first and second insulating members 35 and 37. There is. In this way, the first and second insulating members 35 and 37, and the first insulating member 35 and the second insulating member 3
The pressure sensitive part 33 consisting of the pressure sensitive element 39 sandwiched between the metal gasket 7 and the metal gasket 1 has a small thickness as a whole, and therefore does not have a substantial effect on the external force acting on the metal gasket 1. Become.

The linear expansion coefficients of the first and second insulating members 35 and 37 forming the pressure-sensitive section 33 and the pressure-sensitive element 39 are selected based on the selection of the linear expansion coefficients of the first and second insulating members 35 and 37, respectively, and the pressure-sensitive element 39. Assuming that the linear expansion coefficient is Bp and the linear expansion coefficient of the pressure sensitive element 39 is Bs, the formula: α+K[Βg-(Bp-Bs)]=0 (however,
α is the resistance temperature coefficient of the pressure-sensitive element 39, K is the sensitivity of the pressure-sensitive element 39, that is, a coefficient according to the strain cage ratio; for example, in the case of manganin, it is 0.5, and Bg is the first plate-shaped This is the linear expansion coefficient of the member 11. ) is assumed to satisfy the relationship expressed by By doing so, when the resistance value of the pressure sensitive element 39 is about to decrease or increase due to a temperature change, the first and second insulating members 35 and 37 contract or expand according to the temperature change. and thereby change the pressure applied to the pressure sensitive element 39,
The resistance value caused by the temperature change of the pressure-sensitive element 39 is caused by causing the pressure-sensitive element 39 to undergo deformation that reduces its cross-sectional area and increases its length, or deforms that increases its cross-sectional area and shortens its length. The result is that the decrease or increase in is canceled out. That is, the resistance value of the pressure sensitive element 39 is made substantially independent of temperature changes, and the resistance value change of the pressure sensitive element 39 is caused by the change in the resistance value of the pressure sensitive element 39.
This will occur in response to changes in the external pressure exerted through 5 and 37.

FIG. 3 shows a detection output forming section 3 to which pressure sensitive elements 39 forming each of the four pressure detecting devices 30 are connected.
FIG. 4 is an equivalent circuit diagram showing an example of a specific configuration of No. 4; This figure 3
In the example of the specific configuration shown in FIG.
5 to one end of a battery 47 constituting a constant voltage source, and the other end of the pressure sensitive element 39 is connected to the other end of the battery 47 through a lead wire 43. A connection point Q between the fixed resistance element 45 and the pressure sensitive element 39 is connected to a comparison input terminal of the level comparison section 49.
A reference voltage source 51 is connected between the reference input terminal of the battery 47 and the other end of the battery 47 , and an output terminal 53 is led out from the level comparison section 49 .

Under such circumstances, a constant voltage Vb supplied by the battery 47 is applied across the series connection of the fixed resistance element 45 and the pressure sensitive element 39, and the fixed resistance element 45 and the pressure sensitive element 39 are connected in series.
The constant voltage Vb supplied by the battery 47 is divided between the connection point Q between the terminals Q and the other end of the battery 47, that is, between both ends of the pressure sensitive element 39 by the fixed resistance element 45 and the pressure sensitive element 39. voltage Vq is obtained. Since the resistance value of the fixed resistance element 45 is always maintained constant, the value of the voltage Vq is assumed to change according to the change in the resistance value of the pressure sensitive element 39. Pressure sensitive element 3
As described above, the resistance value change 9 occurs not substantially due to temperature change, but in response to external pressure change applied to pressure sensitive element 39 via first and second insulating members 35 and 37. Therefore, the voltage Vq is a temperature-compensated detection output obtained from the pressure-sensitive element 39 in response to a change in resistance value of the pressure-sensitive element 39 due to a change in external pressure.

The voltage Vq obtained at the connection point Q is supplied to the comparison input terminal of the level comparison section 49.
It is compared with a reference voltage Vr from a reference voltage source 51 supplied to the reference input terminal of. The value of the reference voltage Vr is such that the combustion pressure in the combustion chamber corresponding to the pressure sensitive element 39 is zero, which is formed inside the cylinder block and cylinder head in which the metal gasket 1 is interposed. It is set to a value corresponding to the value of voltage Vq obtained by . Then, the output terminal 5 derived from the level comparison section 49
3, a comparison output VP having a level corresponding to the difference between the voltage Vq and the reference voltage Vr is obtained.

Under such circumstances, when the combustion pressure Pi in the combustion chamber changes as shown by A in FIG. 4 (horizontal axis: time t, vertical axis: pressure P), the level of comparison output VP is as shown in FIG. B (horizontal axis: time t, vertical axis: level L), and the comparative output VP is the external pressure acting on the pressure sensitive element 39 attached to the metal gasket 1,
Therefore, as the combustion pressure Pi in the combustion chamber changes, the pressure detection output represents the surface pressure acting on the metal gasket 1 disposed at the joint between the cylinder block and the cylinder head.

In the pressure detecting device 30 which is an example of the pressure detecting device according to the present invention as described above, one of the four combustion chamber openings 3 provided in each of the four combustion chamber openings 3 arranged in the metal gasket 1 is provided. However, the pressure sensing device 30 has a plurality of pressure sensing portions 33 arranged to surround each of the four combustion chamber openings 3. It can also be used as a thing. In such a case, the surface pressure acting around each of the four combustion chamber openings 3 arranged in the metal gasket 1 will be detected more precisely.

[0022]

Effects of the Invention As is clear from the above description, the pressure sensing device according to the present invention uses a pressure sensing element whose resistance value changes according to external pressure changes and temperature changes, and the output obtained from the pressure sensing element is improved. When obtaining a pressure detection output based on the pressure sensing element, the pressure sensing element is formed into a linear body, so that the entire thickness of the part including the pressure sensing element and the insulating member that is in contact with it is small. For example, the gasket can be easily attached to a gasket disposed at a joint between a cylinder block and a cylinder head of an engine, and has no substantial effect on the external pressure acting on the gasket. Additionally, when the pressure-sensitive element attempts to reduce or increase its resistance value due to a temperature change, the insulating member that is in contact with the pressure-sensitive element expands or contracts in response to the temperature change, causing the resistance value to decrease or increase. The pressure sensitive element changes the pressure applied to the pressure element, thereby changing the thickness and length of the pressure sensitive element, which acts to cancel out the reduction or increase in resistance value caused by temperature changes in the pressure sensitive element. The detection output obtained from the element is
Appropriate temperature compensation is performed to appropriately cope with changes in resistance value caused by changes in external pressure acting on the pressure sensitive element.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a pressure sensitive part in an example of a pressure detection device according to the present invention together with a gasket in which the pressure sensitive part is arranged.

FIG. 2 is a plan view showing an example of the pressure detection device according to the present invention together with a gasket to which the pressure detection device is applied.

FIG. 3 is an equivalent circuit diagram showing an example of a specific configuration of a detection output forming section to which a pressure sensitive element is connected in the example shown in FIG. 2;

FIG. 4 is a time chart used to explain the operation of an example of a specific configuration of the detection output forming section shown in FIG. 3;

[Explanation of symbols]

1 Metal gasket 3 Opening for combustion chamber 15 Grommet part 20 Bead part 30 Pressure detection device 33 Pressure sensitive part 34 Detection output forming section 35 First insulation member 37 Second insulation member 39 Pressure sensitive element 45 Fixed resistance element 47 Battery 49 Level comparison section 51 Reference voltage source 53 Output terminal

Claims (2)

[Claims] Claims: 1. A pressure-sensitive element that is formed into a linear body and whose resistance value changes in response to changes in external pressure and temperature; and a pressure-sensitive element having a linear expansion coefficient different from that of the pressure-sensitive element; an insulating member that brings about a shape change in the pressure-sensitive element that cancels out a change in resistance value caused by a change in temperature by coming into contact with the pressure-sensitive element in order to apply an external pressure to the element; A pressure detection device comprising: a detection output forming section that generates a detection output corresponding to a change in the pressure. 2. The insulating member is made of a synthetic resin material that shrinks or expands in response to temperature changes when the pressure sensitive element increases or decreases its resistance value in response to temperature changes. The pressure detection device according to claim 1.