JP2000180286A - Cylinder inner pressure sensor for engine and measuring device for air quantity flowing in cylinder using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and simplify the construction by structuring pressure detecting elements between a diaphragm and the extreme end part of a housing through the protrusion of the diaphragm into a load receiving structure for receiving pressure in a cylinder, and supported. SOLUTION: A diaphragm 25 provided on the extreme end of a housing 2 is provided with a protrusion 24 protruding on the housing 2 side, formed on one end of a cylindrical member 26 formed into a cap shape out of deposited reinforced metallic material, and the cylindrical member 26 is fitted to the extreme end of the housing 2 so as to enclose the respective elements 7a and the like of a pressure detecting part 7. The pressure detecting elements 7a receive a load due to cylinder inner pressure between the diaphragm 25 and the extreme end part the of the housing 2, through the projection of the diaphragm, and is supported with a ceramics base plate 17 to be constructed into a load receiver generating compressive stress. By such constitution, the pressure detecting elements 7a generate compressive stress in proportion to the cylinder inner pressure, and it is converted to an electric signal and input to a signal processing circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder pressure sensor for detecting the in-cylinder pressure of an automobile engine with high accuracy, and an apparatus for measuring an in-cylinder air flow rate for each cylinder using the sensor.

[0002]

2. Description of the Related Art An in-cylinder pressure sensor is suitable for detecting abnormal combustion (for example, knocking, misfiring, etc.) of an automobile engine, and has conventionally used a metal diaphragm to detect the pressure in a cylinder forming a combustion chamber of the engine. There is known a flush mount type in-cylinder pressure sensor that directly detects a pressure using a pressure sensor.

[0003] This type of in-cylinder pressure sensor is a method in which a force proportional to the in-cylinder pressure received by a metal diaphragm is transmitted to a pressure detecting unit via an elongated load transmitting rod, and a member of the pressure detecting unit is compressed. The pressure detecting unit is configured by, for example, a piezoelectric element.

Recently, a method of estimating the amount of air flowing into a cylinder using an in-cylinder pressure sensor has been studied. For example, in Japanese Patent Application Laid-Open No. 9-53503, the amount of air flowing into a cylinder is calculated from the pressure difference between the cylinder pressures at two specific crank angles in a compression stroke.

[0005]

The in-cylinder pressure sensor of the type in which the received pressure of the diaphragm responsive to the in-cylinder pressure is transmitted to a pressure detecting portion in the sensor housing through an elongated load transmission rod, the load transmission rod is relatively It is difficult to match the elongation due to temperature change between the load transmitting rod and the sensor housing that houses the load transmitting rod due to the difference in material (difference in linear expansion coefficient). For this reason,
It was necessary to eliminate the measurement error due to the difference in the elongation rate by making the displacement of the metal diaphragm due to the in-cylinder pressure large, and the diameter of the metal diaphragm had to be increased. As a result, there has been a limit to miniaturization of the in-cylinder pressure sensor. Also, the mounting structure of the load transmission rod was complicated.

One of the objects of the present invention is to realize a small and simple structure of an in-cylinder pressure sensor for an engine, which detects an in-cylinder pressure using a diaphragm, and realize a highly durable and highly reliable product. It is to plan.

The other is to improve the measurement accuracy of a device for measuring the amount of air flowing into a cylinder using an in-cylinder pressure sensor. In particular, the amount of residual gas Mr, An object of the present invention is to reduce the measurement error caused by the amount of fuel Mf supplied from the injector and the amount of exhaust gas circulation Me from the exhaust gas controller, and to improve the measurement accuracy of the substantial air amount (true air amount) flowing into the cylinder.

[0008]

The first invention is basically configured as follows.

In other words, in an in-cylinder pressure sensor for detecting the pressure in a cylinder forming a combustion chamber of an engine using a diaphragm, the diaphragm is provided at the tip of a sensor housing, and the diaphragm has a projection protruding toward the sensor housing. A pressure detecting element that outputs an electric signal by compressive stress, receives a load due to an in-cylinder pressure between the diaphragm and a tip end of the sensor housing through a projection of the diaphragm, and generates a compressive stress. It is characterized by being supported in a structure.

According to the above configuration, a force proportional to the in-cylinder pressure received by the diaphragm (for example, a metal diaphragm) is directly transmitted to the pressure detecting portion at only the tip end of the sensor housing without using the load transmitting rod. A possible mounting structure becomes possible. In particular, the projection provided on the diaphragm is much shorter than the load transmitting rod, and the distance between the pressure sensing element receiving the compressive load from this projection and the diaphragm can be shorter than that of the load transmitting rod type. It is possible to limit the difference in elongation due to the temperature change of the diaphragm, the sensor housing, and the like to a small difference that does not hinder the measurement accuracy.

In the present invention, the pressure detecting element is constituted by an element (transducer) for outputting an electric signal by a compressive stress, and the pressure detecting element is supported by a supporting member in a load receiving structure in which a compressive stress is generated. Therefore, it is possible to adopt a structure in which the pressure detecting element does not bend (bend) even when a load due to the cylinder pressure is applied from the projection of the diaphragm, and the pressure detecting element is deformed and the resulting damage due to fatigue over time. There is no risk of occurrence.

As a result, measurement accuracy and durability are improved with a small and simple structure.

The in-cylinder pressure sensor having such a small and simple structure is inexpensive and can be economically mounted on all cylinders of the engine.

The second invention relates to a device for measuring the amount of inflow of air in a cylinder using an in-cylinder pressure sensor, and is basically configured as follows.

That is, in an in-cylinder air inflow measuring device for calculating an in-cylinder air inflow amount using an in-cylinder pressure sensor for detecting an in-cylinder pressure of an engine, When calculating the amount of air flowing into a cylinder using information, the amount of residual gas in the pre-combustion process of the engine, the amount of fuel supplied by the injector, and the amount of exhaust gas circulation are obtained. It is characterized in that it is provided with a calculating means for taking the amount of circulation as a subtraction factor into the calculation formula for the amount of air flowing into the cylinder.

According to the above configuration, the measurement error element of the air flow rate flowing into the cylinder can be eliminated, and the measurement accuracy of the substantial air amount can be improved.

The following is proposed as a specific method of the calculating means for measuring the inflow amount of air in the cylinder.

For example, if (a) the crank angle at the start of the compression stroke is θ1, and the crank angle immediately before the ignition timing is θ2,
The internal volumes V1 and V2 of the cylinder at 1 and θ2 are estimated, the absolute temperature T1 of the gas in the cylinder is estimated from the combustion state information of the engine, and the in-cylinder pressure P2 at θ2 is obtained from the pressure information from the in-cylinder pressure sensor. , The _total mass M _total flowing into the cylinder is calculated, and (b) the residual gas amount Mr in the previous combustion stroke is estimated from the combustion state information of the engine.
The supply fuel amount Mf is estimated based on the fuel supply information from the injector controller, and the exhaust gas circulation amount Me is estimated based on the exhaust gas circulation amount information from the exhaust gas circulation controller.
Calculate the sum M of r, Mf and Me, and (c) M
By subtracting M from _{total, the} amount of _air M _air flowing into the cylinder is calculated.

The details of the arithmetic expression will be described in the following embodiments of the present invention.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows an overall configuration diagram of a flush mount type in-cylinder pressure sensor (hereinafter, simply referred to as an in-cylinder pressure sensor) according to the present invention.

An elongated cylindrical sensor housing (hereinafter, referred to as a housing) 2 is made of a heat-resistant and gas-resistant metal material.
A screw portion 5 for attaching to the cylinder head 1 of the automobile engine is formed thereunder, and the hexagonal portion 4 is mounted on the cylinder head 1 via the screw portion 5 by turning with a tool.

In FIG. 1, the tip end of the in-cylinder pressure sensor 6 shown in a non-sectional structure has the same surface as the inner wall of the cylinder head 1, that is, a flush mount structure. The in-cylinder pressure detecting unit 7 is mounted on the control unit.

A metal diaphragm, which will be described later, is provided at the sensor tip 6, ie, at the forefront of the sensor housing 2, so that a pressure proportional to the in-cylinder pressure P can be received. When the housing 2 is mounted on the cylinder head 1, the packing 3 is sealed so that the leakage of the combustion gas does not occur.

The signal processing circuit 12 of the in-cylinder pressure sensor is fixed on the ceramic substrate 11. Ceramic substrate 11
Is fixed to the inside of the housing 2 while being held by a plug 13 for terminal extraction provided at the upper end of the housing 2. The signal processing circuit 12 is electrically connected to the pressure detector 7 provided at the tip of the housing 2 via lead wires 10a and 10b.

In order to prevent a short circuit between the lead wires 10a and 10b and the housing 2, an insulating member 8 is loaded between the ceramic substrate 11 (signal processing unit) and the front end portion 6 of the housing 2 in the housing 2, and the insulation is performed. Lead wires 10a and 10b are inserted through lead wire holes 9 provided in the member 8. The power supply terminal, output terminal and diagnostic terminal of the in-cylinder pressure sensor
These terminals are collectively indicated by reference numeral 14, and one end of each of these terminals is connected to the signal processing circuit 12 on the ceramic substrate 11, and is drawn out through the plug 13.

FIG. 2 shows a specific example of a mounting structure of the in-cylinder pressure detecting section 7 provided inside the distal end portion 6 of the in-cylinder pressure sensor of FIG.

As shown in FIG. 2, a diaphragm 25 is provided at the tip of the housing 2, and the diaphragm 25 has a projection 24 protruding toward the housing 2. The diaphragm 25 is made of SUS631 or Inconel, which is a precipitation-strengthened metal material having high strength even at a high temperature, and the thickness of the diaphragm 25 is about several hundred microns. The diaphragm 25 is formed at one end of a cylindrical member 26 formed in the form of a cap from the above-described deposited metal material.
a, 17 and 18 are enclosed.
This attachment is performed by airtightly joining the cylindrical member 26 to the outer peripheral surface of the front end of the housing 2 by welding or press fitting.

The pressure detecting section 7 is composed of the diaphragm 25, the ceramic substrates 17, 18 and the piezoelectric element 7a serving as a pressure detecting element. Basically, the pressure detecting element 7a, which outputs an electric signal by compressive stress, receives a load due to the in-cylinder pressure between the diaphragm 25 and the tip of the sensor housing 2 via the projection 24 of the diaphragm 25, and receives the electrode lead. It has a load receiving structure in which a compressive stress is generated by being supported by the ceramic substrate 17 for pulling out 20, 21. The specific mode is as follows.

The pressure detecting element 7a is made of quartz, lithium niobate (LiNbO ₃ ), lithium tantalate (LiTa
O ₃ ) and the like, and the Curie points of these materials are about 570 ° C., 1100 ° C.,
It is as high as 600 ° C.

Electrodes 15 and 16 are formed on both surfaces of the pressure detecting element (piezoelectric element) 7a by a method such as vapor deposition or sputtering to take out charges generated when the pressure detecting element 7a is compressed. I have. Using this electrode material,
Both surfaces of the pressure detecting element 7a are joined to ceramic substrates 17 and 18 for leading out electrode leads. This bonding is performed on the bonding surfaces of the ceramic substrates 17 and 18 (the electrodes 15 and
A metal material of the same type as the electrode materials 15 and 16 is previously formed on the surface (the surface facing the surface 16), and a laminate composed of the ceramic substrate 18, the pressure detecting element 7a, and the ceramic substrate 17 is weighted at a temperature of several hundred degrees. By applying a thermocompression bonding step of applying a pressure-sensitive adhesive, these laminated elements can be firmly joined. This laminate is fixed to the front end surface of the housing 2 by the joining member 19.

Of the opposing surfaces of the ceramic substrates 17 and 18, the former is entirely flat, and the latter is formed with a concave portion 18a, in which the pressure detecting element 7a is located. The ceramic substrate 1 and the ceramic substrate 1
A bonding member 23 made of a metal material for bonding the members 7 and 18 to each other is formed, and the bonding member 23 is simultaneously thermocompression-bonded during the step of bonding the electrodes 15 and 16 to the ceramic substrates 17 and 18. 18 are joined.

A conductor (electrode lead) 2 for guiding an electric signal of the pressure detecting element is provided in the ceramics substrates 17 and 18.
0, 21 and 22 are integrally formed with the ceramic substrate. Among them, one end of the conductor 20 faces the electrode 15 of the pressure detecting element 7a, and the other end thereof is the lead wire 10 on the housing 2 side.
It faces the end face of a. On the other hand, the conductors 21 and 22 are for leading the electrode 16 of the pressure detecting element 7a,
Is formed in the ceramics substrate 18, the conductor 21 is formed in the ceramics substrate 17, the conductor 22 and the conductor 21 are connected via the joining member 23, and the other end of the conductor 21 is connected to the lead wire 10b. .

The electrodes 15, 16 and the joining member 23 are made of a noble metal material such as gold or silver. The lead wire 10a
And 10b are fixed to the ceramic substrate 17 by a method such as silver brazing, and the conductors 20 and 2 of the ceramic substrate 17 are fixed.
1 is connected to one end. Lead wires 10a, 10b
Is passed through a hole 9 ′ provided in the housing 2 at the tip of the housing 2, and lead wires 10 a and 10
An insulating material 60 is filled in order to prevent b from short-circuiting by contacting the housing 2.

Ceramic substrate 18, pressure detecting element 7
a, the laminated body composed of the ceramic substrate 17 is joined to the joining member 1
After joining to the front end of the housing 2 at 9, a cylindrical member 26 having a diaphragm 25 with a projection 24 so as to compress the laminate is hermetically joined to the housing 2 by welding or press fitting. Even when the in-cylinder pressure is zero, the pressure detecting element 7
The cylindrical member 26 is joined to the housing 2 so as to apply a compressive load to a.

The diaphragm 25 is mounted on a flash mount in the combustion chamber of the engine, and applies a force proportional to the in-cylinder pressure received by the diaphragm 25 to the pressure detecting element via the protrusion 24 and the ceramic substrate 18 having a thickness of about 1 mm or less. 7a. In order to accurately transmit the compression load proportional to the in-cylinder pressure to the pressure detection element 7a,
The projection 24 is provided so as to coincide with the axis of the housing 2, and the tip of the projection 24 is formed into a spherical surface as shown in the figure.

With the above configuration, a compressive stress proportional to the in-cylinder pressure is generated in the pressure detecting element 7a, and this is converted into an electric signal, which is transmitted through the conductors 20, 21, 22 and the leads 10a, 10b. Input to the signal processing circuit 12.

FIG. 10 shows a detection circuit when a single crystal piezoelectric material such as quartz, lithium niobate, lithium tantalate or the like is used for the pressure detecting element 7a of the in-cylinder pressure detecting section 7.
Feedback capacitor 41 of high impedance amplifier 42
Is proportional to Cg and the in-cylinder pressure P.
Assuming that the charge generated at a is Q, −Q /
An output signal Vo of Cg is obtained. The amplifier 42, the feedback capacitor 41, and the capacitance Cg correspond to the signal processing circuit 12.

According to this embodiment, an elongated load transmitting rod as described in the prior art is unnecessary, and a force proportional to the in-cylinder pressure received by the diaphragm 25 is applied to the pressure detecting section 7 at a position only at the tip of the sensor housing. A mounting structure capable of directly transmitting is possible. Since the distance between the diaphragm 25 and the pressure detecting element 7a is as short as several millimeters or less at most, the protrusions 24, the diaphragm 25, the cylindrical member 26, the housing 2, the detecting unit laminates 7a, 17, and 18 are heated by the combustion gas of the engine. However, the pressure detecting element 7a associated with the thermal expansion of these members
Of the pre-compression load can be made as small as possible. As a result, the diameter of the diaphragm 25 is several millimeters or less, and the in-cylinder pressure sensor can be downsized. Further, the in-cylinder pressure sensor has a simple mounting structure.

As described above, the diaphragm 25 is made of SUS, which is a precipitation-strengthened metal material having high strength even at high temperatures.
631 or Inconel is used, and the thickness of the diaphragm 25 is about several hundred microns. The temperature of the combustion gas of the automobile engine becomes 1000 ° C. or more, and the surface temperature of the diaphragm 25 rises up to about 700 ° C. depending on the operation state. The above-described precipitation strengthened metallic material has high reliability even at this temperature. At this time, the pressure detecting element 7a
Although heated to a temperature of 0 ° C. or higher, the Curie points of quartz, lithium niobate, and lithium tantalate are higher than these temperatures, so that the in-cylinder pressure can be detected with high accuracy.

Further, according to this embodiment, since the pressure detecting element 7a is supported by the supporting member (the ceramic substrate 17 and the end face of the housing 2) in a load receiving structure in which a compressive stress is generated, the diaphragm 25 is attached to the pressure detecting element 7a.
Even if a load due to the in-cylinder pressure is applied from the protrusion 24, a structure in which the pressure detecting element 7a does not bend (bend) can be adopted, and thus the pressure detecting element 7a is deformed and the resulting time-dependent fatigue causes damage. There is no risk of occurrence.

As a result, measurement accuracy and durability are improved with a small and simple structure.

Next, another embodiment of the in-cylinder pressure sensor according to the present invention will be described with reference to FIGS. In the drawings, the same reference numerals as those in FIGS. 1 and 2 indicate the same elements.

In this embodiment, basically, a diaphragm 25 with a projection 24 is provided at the tip of the housing 2, and the pressure detecting element 7 b for outputting an electric signal by compressive stress is provided between the diaphragm 25 and the tip of the housing 2. The load is supported by a load receiving structure that receives a load due to the in-cylinder pressure and generates a compressive stress through the projection 24 of the diaphragm 25 therebetween.

In this embodiment, the pressure detecting element 7b of the in-cylinder pressure detecting section 7 is an SOI (Silicon On Insulator).
A thermal oxide film 3 on a single crystal silicon substrate 32
3 is formed by laminating a P-type silicon element formation substrate 34 having a plane orientation of (110) whose resistance changes due to compressive stress on the thermal oxide film 33, and the principle is maintained even if it is heated to 500 ° C. or more. It is a material that does not hinder the detection of the in-cylinder pressure.

FIGS. 4 and 7 show a detailed view of the pressure detecting element 7b using the silicon SOI substrate according to the present invention. FIG. 4 is a sectional view taken along line AB in FIG. FIG.
FIG. 4 is a plan view of an I-substrate 7b, particularly a view in which the insulating film 39 is removed and the pressure detection element 7b is viewed in an unfolded state.

A single crystal silicon substrate 32, a thermal oxide film 33,
The thickness of the element forming substrate 34 is several hundred microns, about one micron, and several to several tens of microns.

By etching the element forming substrate 34,
A strain gauge 38, an extraction resistor (lead portion) 37, and a pad 36 are formed. Strain gauge 38, extraction resistance 3
7 and a part of the surface of the pad 36 are covered with an insulating film 39 such as a thermal oxide film. Bonding members 31 and 40 made of a noble metal material are formed on the surfaces of the pad 36 and the strain gauge 38 by a method such as vapor deposition or sputtering. The joining members 31 and 40 on the insulating film 39 have the same height.

More specifically, as shown in FIG. 7, the strain gauge 38 comprises strain gauges 38a and 38b. Here, the strain gauge in the direction of the crystal axis <110> is 38a and the crystal axis is <10.
The strain gauge in the 0> direction is defined as 38b. The bridge circuit composed of two strain gauges 38a and 38b is a thermal oxide film 3
3 is formed on the surface.

The strain gauge 38 (= 38a, 38b) and the pad 36 have the same height as shown in FIG. 4, but the lead-out resistance (lead) 37 is set to be several microns lower than this. Etched. That is, in the SOI substrate 7b, the P-type silicon element formation substrate 34 is etched to form a convex strain gauge 38 and a convex lead lead-out pad 36 on the surface of the thermal oxide film 33 on the single crystal silicon substrate 32. Is formed.

The SOI substrate 7b is a single crystal silicon substrate 3
The second side is a pressure receiving surface pressed by the projection 24 of the diaphragm 25, and the element forming substrate 34 side is supported by the ceramic substrate 27 for lead extraction with only the strain gauge portion 38 and the pad 36 bonded thereto. Therefore, since the force proportional to the in-cylinder pressure received by the diaphragm 25 acts only on the strain gage portion 38 and the pad portion 36 having a small area, the compressive stress of the strain gage portion 38 can be set to an extremely large value. As a result, the in-cylinder pressure can be detected with high sensitivity.

Ceramic substrate 27 for lead extraction
The number of leads (conductors) 29 corresponding to the number of the pads 36 and the lead wires 10 is integrally formed with the ceramic substrate 27.
As shown in FIG. 3, a joining member 30 made of a noble metal material,
28 are formed. Among them, the joining member 30 is formed at a position corresponding to the pad 36 and the strain gauge 38 of the pressure detecting element (SOI substrate) 7b. The joining member 31 is formed on one surface of the pressure detecting element 7b at a position corresponding to the strain gauge 38 and a position corresponding to the pad 36.
By the thermocompression bonding between the joining member 31 and the joining member 30,
The pressure detecting element 7b and the ceramic substrate 27 are firmly joined.

The laminate composed of the pressure detecting element 7b and the ceramic substrate 27 is fixed to the front end of the housing 2 via the joining member 28. The pressure detecting element 7b is electrically connected to a lead wire 10 inserted through the housing 2 through a conductor 29 formed in the ceramic substrate 27.

FIG. 8 shows the theoretical sensitivity of the strain gauge when compressive stress is applied to P-type silicon having a plane orientation of (110). As shown in the figure, the sensitivity in the direction of the crystal axis <100> is zero, and the sensitivity is maximum in the direction of the crystal axis <110>. Therefore, when compressive stress is generated in the strain gauges 38a, 38b via the projections of the diaphragm 25 in proportion to the in-cylinder pressure P, the resistance value of the strain gauge 38a greatly changes, but the resistance value of the strain gauge 38b does not change at all. It does not change.

FIG. 9 shows an equivalent circuit of the pressure detecting element 7b using the SOI substrate. If the resistance value of the extraction resistor 37 is sufficiently small, an equivalent circuit can be written as shown in FIG. As described above, the change in the resistance value with respect to the in-cylinder pressure P is caused by the strain gauge 38 arranged in the crystal axis <110> direction.
a only.

In this embodiment, in addition to the same effects as those of the first embodiment, the following effects can be obtained.

As described above, by applying the pressure (compression load) of the in-cylinder pressure to the strain gauge portion 38 having a small area, the compressive stress of the strain gauge 38a can be made extremely large. High sensitivity detection of internal pressure becomes possible. According to the results of the trial production, when Vcc was 5 volts, a sensitivity of ΔV = several hundred mV was obtained for a change in the in-cylinder pressure of 100 atm.

Further, the strain gauge 38 (= 38a, 38b)
Since the bridge circuit is formed on the surface of the thermal oxide film 33, the leakage current between the strain gauges has a very small value up to a considerably high temperature. As a result, even if the pressure detecting element was heated to 500 ° C. or higher, the in-cylinder pressure could be detected with high accuracy.

FIG. 5 shows another embodiment (application example) of the pressure detecting element 7b using the silicon SOI substrate according to the present invention. FIG. 5 is a cross-sectional view of the pressure detecting element taken along line AB as in FIG. FIG. 6 is a plan view of the pressure detecting element 7b of FIG.

In this embodiment, a single crystal silicon substrate 32 is etched to form a trapezoidal silicon projection 35 at the center of the substrate 32. The projection 24 of the diaphragm 25 comes into contact with the silicon projection 35, and a concentrated compressive load due to the in-cylinder pressure is transmitted to the silicon projection 35 via the projection 24. If the silicon projection 35 is sufficiently small, the projection 24 provided on the metal diaphragm 25 does not necessarily have to be spherical. The height of the projection 35 is
About half the thickness of

FIG. 11 schematically shows another mounting mode of the in-cylinder pressure sensor according to each of the above embodiments. In this example, a DI (direct injection; in-cylinder injection) type injector 44 for directly supplying fuel to the combustion chamber of an automobile engine is mounted on the cylinder head 1 so as to be mounted in a flash mount on the combustion chamber.

When the drive rod 46 directly connected to the ball valve 45 moves upward by electromagnetic force or the like, fuel is supplied into the combustion chamber as shown by the arrow. If the pressure detecting element 7 is sufficiently small as in the present invention, it is possible to easily mount the in-cylinder pressure detecting section 7 at the tip of the injector as shown in the figure. Since it is not always easy to provide a hole in the engine for mounting the in-cylinder pressure sensor on the engine, it is very effective if a flash mount type in-cylinder pressure sensor can be mounted on the injector.

Next, a method for measuring the amount of new air flowing into each cylinder with high accuracy by using the in-cylinder pressure sensor will be described.

FIG. 12 shows the relationship between the crank angle and the in-cylinder pressure. This figure shows the in-cylinder pressure waveforms during the compression stroke and the explosion stroke. The crank angle at the start of the compression stroke is θ1,
Assume that the crank angle immediately before the ignition timing is θ2, the in-cylinder pressures at θ1 and θ2 are P1 and P2, respectively, and the cylinder internal volume V1 and P2.
Assuming that the absolute temperature T1 of the gas in the cylinder at V2 and θ1 and the gas constant is R1, from the state equation in the cylinder,

[0065]

P1 · V1 = M _total · R1 · T1 (1) is obtained. Here, M _total is the _total mass flowing into the cylinder.

If the polytropic index is n,

[0067]

(Equation 2)

Is obtained.

If the amount of residual gas is Mr, the amount of fuel supplied from the injector is Mf, the amount of exhaust gas circulation is Me, and the amount of new air flowing into the cylinder is Mair,

[0070]

M _total = Mr + Mf + Me + M _air (3) From equations (1), (2) and (3), the amount M _{air of} new air flowing into the cylinder is:

[0071]

(Equation 4)

Is obtained. Therefore, if the parameters on the right side of the equation (4) can be accurately estimated, the true M _air can be measured.

FIG. 13 shows a highly accurate measuring device for a new amount of air flowing into a cylinder according to the present invention. As can be understood from the equation (4), it is possible to detect the amount M _{air of} new air flowing into the cylinder with high accuracy by the following procedure.

(A) The crank angle θ1 at the start of the compression stroke and the crank angle θ2 immediately before the ignition timing are read from the crank angle sensor 48, and the internal volume V1,
V2 is estimated, the absolute temperature T1 of the in-cylinder gas is estimated from the combustion state in the combustion stroke immediately before the engine, and the in-cylinder pressure P at the crank angle θ2 is detected by the flash mount type in-cylinder pressure sensor 47.
2 is detected, and the _total mass M _total flowing into the cylinder is calculated from these values.

(B) With the help of the engine control microcomputer 51, the amount Mr of the residual gas in the previous combustion stroke is estimated from the immediately preceding combustion state of the engine, the amount Mf of the supplied fuel is estimated from the injector controller 49, The exhaust gas circulation amount Me is estimated from the circulation controller 50, and M
Calculate the sum M of r, Mf and Me.

(C) By subtracting M from M _total ,
The new air amount Air that has flowed into each cylinder can be measured with high accuracy.

The measurement of the new air amount M _air flowing into the cylinder is executed by the signal processor 52 in real time. Note that the signal processor 52 can be substituted by the engine control microcomputer 51.

According to this embodiment, the amount of air flowing into each cylinder can be directly measured, and the measurement accuracy of the device for measuring the amount of air flowing into the cylinder using the in-cylinder pressure sensor 47 is improved. The amount of residual air in the pre-combustion process, the amount of fuel supplied from the injector Mf, and the amount of exhaust air circulating from the exhaust gas controller Me, which has not been taken into account so far, reduces measurement errors and flows into the cylinder. (True air volume) measurement accuracy can be improved.

[0079]

As described above in detail, according to the first aspect, the in-cylinder pressure sensor for the engine for detecting the in-cylinder pressure using the diaphragm has a small and simple structure, and has excellent durability. A highly reliable product can be realized.

According to the second aspect of the invention, the measurement accuracy of the device for measuring the amount of air flowing into the cylinder using the in-cylinder pressure sensor can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an in-cylinder pressure sensor according to the present invention.

FIG. 2 is a partial sectional view showing a mounting structure of an in-cylinder pressure detecting unit of the in-cylinder pressure sensor according to the present invention.

FIG. 3 is a partial cross-sectional view showing another mounting structure of the in-cylinder pressure detector of the in-cylinder pressure sensor according to the present invention.

FIG. 4 is a detailed view of an in-cylinder pressure detecting element using a silicon SOI substrate according to the present invention.

FIG. 5 is a view showing another embodiment of the in-cylinder pressure detecting element using the silicon SOI substrate according to the present invention.

FIG. 6 is a plan view of an SOI substrate having silicon projections.

FIG. 7 is a plan view showing an element forming substrate of an in-cylinder pressure detecting element using a silicon SOI substrate according to the present invention.

FIG. 8 is a diagram showing the theoretical sensitivity of a P-type strain gauge when compressive stress is applied.

FIG. 9 is an equivalent circuit diagram of an in-cylinder pressure detecting member using a silicon SOI substrate.

FIG. 10 is a detection circuit diagram when a piezoelectric material is used for the in-cylinder pressure detection element.

FIG. 11 is a schematic diagram in which a flush mount type in-cylinder pressure sensor according to the present invention is mounted on an injector.

FIG. 12 is a diagram showing a relationship between a crank angle and an in-cylinder pressure.

FIG. 13 is a view showing a method for measuring a new air amount flowing into a cylinder according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 2 ... Housing, 6 ... Sensor tip part, 7 ... In-cylinder pressure detection part, 7a ... Pressure detection element, 7b ... Pressure detection element (SOI board), 10 ... Lead wire, 10 (1
0a, 10b) lead wire, 11 ceramic substrate,
12: signal processing circuit, 17, 18: ceramic substrate,
20, 21, 22 ... conductor, 24 ... projection, 25 ... diaphragm, 27 ... ceramic substrate, 36 ... pad, 38 ...
Strain gauge, 47… Flush mount type in-cylinder pressure sensor,
48: crank angle sensor, 49: injector controller, 50: exhaust gas circulation amount controller, 51: microcomputer for engine control, 52: signal processor (arithmetic means).

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenji Tsuchida 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Yasuhiro Asano 2477 Takaba, Hitachinaka City, Ibaraki Stock F term in Hitachi Car Engineering (reference) 2F055 AA23 CC02 DD01 EE13 EE23 FF43 GG11 GG12 GG25 HH03 3G084 DA04 DA13 EC04 FA00 FA07 FA13 FA19 FA21 FA37 FA38

Claims (11)

[Claims] An in-cylinder pressure sensor for detecting the pressure in a cylinder forming a combustion chamber of an engine using a diaphragm, wherein the diaphragm is provided at a tip of a sensor housing, and the diaphragm has a projection protruding toward the sensor housing. A pressure detecting element that outputs an electric signal by a compressive stress, receives a load due to an in-cylinder pressure between the diaphragm and a tip of the sensor housing via a protrusion of the diaphragm, and generates a compressive stress. An in-cylinder pressure sensor for an engine, which is supported in a structure. 2. The pressure detecting element is made of quartz, LiNbO.
_3, cylinder pressure sensor for of claim 1 engine comprising a single crystal piezoelectric material such as LiTaO _3. 3. A support for supporting the pressure detecting element is formed of a ceramic substrate, and a conductor for guiding an electric signal of the pressure detecting element is formed integrally with the ceramic substrate in the ceramic substrate. 3. The in-cylinder pressure sensor for an engine according to claim 1, wherein one end of the conductor in the ceramic substrate is connected to a lead wire passed through the sensor housing. 4. The in-cylinder pressure sensor for an engine according to claim 3, wherein the pressure detecting element and the ceramic substrate are joined by thermocompression bonding via a joining member made of a noble metal material such as gold. 5. The in-cylinder pressure sensor for an engine according to claim 1, wherein the diaphragm is made of SUS631 or Inconel which is a precipitation strengthening metal material. 6. The in-cylinder pressure sensor for an engine according to claim 1, wherein the pressure detection element is formed of an SOI substrate. 7. The SOI substrate is formed by laminating a single crystal silicon substrate, a thermal oxide film formed on the single crystal silicon substrate, and a P-type silicon element formation substrate having a plane orientation of (110). 7. An in-cylinder pressure sensor for an engine according to claim 6, comprising a body. 8. The SOI substrate has a convex strain gauge and a convex lead drawing pad formed on the surface of a thermal oxide film on the single crystal silicon substrate by etching the P-type silicon element formation substrate. The in-cylinder pressure sensor for an engine according to claim 7, wherein the sensor is formed. 9. The in-cylinder pressure sensor for an engine according to claim 8, wherein the strain gauge and the pad are joined to a ceramic substrate by thermocompression bonding via a joining member. 10. An in-cylinder air inflow measuring device that calculates an in-cylinder air inflow amount using an in-cylinder pressure sensor that detects an in-cylinder pressure of an engine. When calculating the amount of air flowing into a cylinder using information, the amount of residual gas in the pre-combustion process of the engine, the amount of fuel supplied by the injector, and the amount of exhaust gas circulation are obtained. An apparatus for measuring the amount of air flowing into a cylinder, comprising a calculating means for taking the amount of circulation as a subtraction factor into a formula for calculating the amount of air flowing into a cylinder. 11. The calculating means includes: pressure information detected by the in-cylinder pressure sensor; crank angle information of an engine crank angle sensor; combustion state information from a means for detecting a combustion state of the engine; and fuel from an injector controller. Based on the supply amount information and the exhaust gas circulation amount information from the exhaust gas circulation controller, based on these information, the following calculations (a) to (c) are performed, that is, (a) the crank angle at the start of the compression stroke is θ1, The crank angle just before the ignition timing is θ
2, the internal volumes V1, V of the cylinder at θ1, θ2
2 is estimated, the absolute temperature T1 of the in-cylinder gas is estimated from the combustion state information of the engine, the in-cylinder pressure P2 at θ2 is obtained from the pressure information from the in-cylinder pressure sensor. Calculate the mass M _total ,
(B) The residual gas amount Mr in the pre-combustion process is estimated from the combustion state information of the engine, the supplied fuel amount Mf is estimated from the fuel supply information from the injector controller, and the exhaust gas circulation amount is estimated from the exhaust gas circulation information from the exhaust gas circulation controller. 11. The in-cylinder according to claim 10, wherein Me is estimated, an amount M obtained by adding Mr, Mf, and Me is calculated, and (c) M is subtracted from M _total to calculate an air amount M _air flowing into the cylinder. Measurement device for air inflow.