JPH05264390A - Combustion pressure sensor - Google Patents

Abstract

PURPOSE:To give an previously specified electric potential difference between a positive side output electrode and a negative side output electrode of the combustion pressure sensor and set off offset voltage caused by stress and preload in a production process on a semiconductor type combustion pressure sensor arranged in the cylinder of an internal combustion engine and for converting the combustion pressure of the cylinder into an electric signal. CONSTITUTION:The (110) face of an Si monocrystal body 1 is made a pressure detection face, and a positive side input electrode 4 and a negative side input electrode 5 are provided at one opposite angle opposed to the direction of 45 deg. from the (001) direction of a crystal. A negative side output electrode 2 offset at the side of the positive side input electrode 4 and a positive side output electrode 3 offset at the side of the negative side input electrode 5 from a diagonal line thereof are provided at the other opposite angle and previously negative voltage is set on a combustion pressure sensor 10 itself for the purpose of setting off offset voltage caused by an additional part (preload) given at the time of assembly of the combustion pressure sensor 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion pressure sensor, and more particularly to a semiconductor combustion pressure sensor which is provided in a cylinder of an internal combustion engine and converts combustion pressure in the cylinder into an electric signal.

[0002]

2. Description of the Related Art Conventionally, two pairs of electrodes are provided on a silicon (Si) single crystal body, one of which is used as an output electrode,
There is known a semiconductor combustion pressure sensor which uses another pair as an input electrode for driving a constant voltage and converts a pressure applied on a Si single crystal body into an electric signal and outputs the electric signal (JP-A-64-3).
No. 6081).

FIG. 5 is a front view of the combustion pressure sensor disclosed in the above publication. In the figure, reference numeral 1 denotes a Si single crystal body that constitutes a main part of the combustion pressure sensor 20, and the (110) plane of this Si single crystal body 1 is a surface to which pressure is applied. On this (110) plane, as shown in FIG.
1) The positive side input electrode 4 and the negative side input electrode 5 are provided on the diagonal opposite to each other in the direction of 45 °, and

[0004]

[Outside 2]

Positive side output electrodes 13 and negative side output electrodes 12 are provided diagonally opposite each other at a direction of 45 °.

When a predetermined constant voltage is applied to the positive side input electrode 4 and the negative side input electrode 5 of the combustion pressure sensor 20 having the above-described structure in a non-pressurized state, the Si single crystal body 1 is homogenous, so that it is positive. The potentials of the positive side output electrode 13 and the negative side input electrode 5, which are in a symmetrical positional relationship with the side input electrode 4 and the negative side input electrode 5, become equal.

In general, when pressure is applied to the crystal plane of a semiconductor single crystal, the piezoresistance coefficient, which is one of the factors that determines the electrical conductivity of the semiconductor single crystal, changes according to the applied pressure. The Si single crystal body 1 has a piezo effect which causes the positive side output electrode 1 arranged at the above position to be generated by the piezo resistance effect when pressure is applied to the (110) plane.
3 and the negative side output electrode 12 so that a potential difference according to the pressure appears between the positive side input electrode 4 and the negative side output electrode 12,
Negative side output electrode 12 and negative side input electrode 5, negative side input electrode 5 and positive side output electrode 13, positive side output electrode 13 and positive side input electrode 4
Change the electric resistance value between.

Therefore, the combustion pressure sensor 2 having the above structure
0 produces a potential difference between the positive side output electrode 13 and the negative side output electrode 12 in accordance with the pressure applied to the (110) plane of the Si single crystal body 1, whereby the cylinder internal pressure of the internal combustion engine is converted into an electric signal. It is converted into and taken out.

[0009]

However, the conventional combustion pressure sensor 20 described above has a residual stress in the manufacturing process and generally has a distortion, so that the output is not affected even in a non-pressurized state.
When the combustion pressure sensor 20 is held by a housing or the like in order to dispose the combustion pressure sensor 20 in the cylinder of the internal combustion engine, in order to efficiently receive the pressure transmission from the pressure detection surface of the housing, a pressure transmission member is used. It is necessary to apply a predetermined pressure (preload) to the (110) plane of the Si single crystal body 1 in advance,
A pressure is applied that is independent of the pressure to be detected.

On the other hand, the output voltage of the combustion pressure sensor 20 is a minute voltage (0 to several hundred [mV]), and it is necessary to amplify it by an amplifier in order to use it for control. 6 shows the output when the output of the combustion pressure sensor 20 is amplified by an amplifier, FIG. 6A shows the amplified voltage V ₁ for the offset voltage due to the stress in the above manufacturing process, and FIG. The amplified voltage V ₂ when the offset voltage due to the preload is added to this is shown.

FIG. 1C shows the upper limit amplification voltage (output range) V ₃ determined by the driving voltage of the amplifier. The amplification factor of the amplifier is determined so that the amplified voltage of the maximum input voltage obtained by adding the output voltage when the combustion pressure sensor 20 detects the maximum pressure to the above two types of offset voltages falls within this output range. Therefore, the above conventional combustion pressure sensor 20
However, there is a problem that the change range of the pressure detection signal in the output range of the amplifier is restricted by the offset voltage and becomes narrow.

The present invention has been made in view of the above points, and in order to improve the pressure detection accuracy by widening the change range of the pressure detection signal in the output range of the amplifier, the positive side output electrode and the negative side are provided. An object of the present invention is to provide a combustion pressure sensor that offsets an offset voltage caused by stress and preload in a manufacturing process by applying a predetermined potential difference between the output electrode and the output electrode.

[0013]

In order to solve the above problems, the present invention provides a Si single crystal body having a (110) plane of a crystal as a surface to which a pressure is applied, and the Si single crystal body. A pair of first electrodes provided to face each other at a direction of 45 ° from the (001) direction of the crystal;

[0014]

[Outside 3]

In a pressure sensor comprising a pair of second electrodes provided opposite to each other at a direction of 45 ° from each other, one of the first and second electrodes being an output electrode and the other being an input electrode. The electrodes are arranged such that the potential of the positive output electrode during the non-pressurized constant voltage drive is lower than the potential of the negative output electrode by a predetermined potential.

[0016]

According to the above structure, the potential of the positive side output electrode of the combustion pressure sensor becomes a potential lower than the potential of the negative side output electrode by a predetermined potential during the non-pressurized constant voltage drive.
The offset voltage of the combustion pressure sensor itself is set to the negative side. Therefore, the stress and the offset voltage due to the preload in the manufacturing process are canceled out, and the output of the combustion pressure sensor is only the pressure detection voltage, and the change range of the pressure detection signal in the output range of the amplifier can be made large.

[0017]

1 shows a front view of an embodiment of a combustion pressure sensor according to the present invention. The same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In the figure, 10 is a combustion pressure sensor of this embodiment, and two pairs of electrodes are provided on the (110) plane of the Si single crystal body 1 as in the conventional combustion pressure sensor. 3 in the figure
Indicates a positive-side output electrode, which is disposed on the (110) plane of the Si single crystal body 1 and faces the corner portion where the positive-side output electrode 3 is disposed on the (110) plane of the Si single crystal body 1. The negative side output electrode 2 is arranged at the corner.

The positive-side output electrode 3 and the negative-side output electrode 2 have protrusions 2a and 3a in opposite directions. As shown in the figure, the protrusion 3a is a diagonal line connecting the opposite corners. 11 is provided in a region closer to the negative side input electrode 5, and the protrusion 2a is provided in a region closer to the positive side input electrode 4 than the diagonal line 11 and are offset from each other by a predetermined width.

The Si single crystal body 1 is homogeneous, and the positive side input electrode 4 and the negative side input electrode 5 are lined with respect to the diagonal line 11 at the corners facing each other in the direction of 45 ° from the (001) direction of the crystal. Since the power supply voltage is supplied to the positive side input electrode 4 and a constant voltage is applied between both electrodes by grounding the negative side input electrode 5, the positive side output electrode 3 and the negative side output electrode are arranged symmetrically. When there is no 2, the potential on the diagonal line 11 becomes an equipotential, which is half the applied constant voltage.

As described above, in the combustion pressure sensor 10 according to this embodiment, the positive side output electrode 3 and the negative side output electrode 2 are provided with the protrusions 2a and 3a offset from the diagonal line 11, so that the positive side output electrode The potential of 3 becomes lower than the potential of 1/2 of the applied constant voltage, and the potential of the negative output electrode 2 becomes
It becomes higher than half the potential of the applied constant voltage. Therefore, a predetermined potential difference is generated between the positive output electrode 3 and the negative output electrode 2, and when the positive output electrode 3 is the positive electrode and the negative output electrode 2 is the negative electrode, a negative offset voltage is generated. Become.

FIG. 2 shows a combustion pressure sensor 10 according to this embodiment.
An example of the simulation result of the electrode arrangement and the electric potential distribution (equipotential gland) is shown. The numbers in parentheses in the figure indicate the potential of the equipotential lines at that position. In the figure, the positive side output electrode 3 and the negative side output electrode 2 have a square shape for simplification, and the positive side output electrode 3 has a negative side with respect to the Si single crystal body 1 of 1.7 [mm] angle. The input electrode 5 is shifted by 100 [μm], and the negative output electrode 12 is shifted by 100 [μm] in the positive input electrode 4 direction. As a driving condition of the combustion pressure sensor 10, the power supply voltage supplied to the positive side input electrode 4 is 5 [V], and the negative side output electrode 2 is grounded.

In this case, the potentials of the positive output electrode 3 and the negative output electrode 2 do not become equal as shown in the figure, the potential of the positive output electrode 3 is 2.38 [V], and the negative output is The potential of the electrode 2 is 2.62 [V], and the combustion pressure sensor 10 has a potential of −24.
This means that the negative offset voltage of 0 [mV] is generated. With the same type of combustion pressure sensor, the offset voltage generated by residual stress and preload in the manufacturing process is 10
Since it is about 0 [mV], the offset voltage after assembling the combustion pressure sensor by the electrode arrangement used in this simulation is about -140 [mV].

As described above, by shifting the electrodes, the offset voltage of the combustion pressure sensor 10 can be arbitrarily changed. Therefore, in the combustion pressure sensor 10, the shift amount of the electrodes is appropriately set to change the combustion pressure. When the offset voltage of the sensor 10 itself is set to −100 [mV], the output voltage of the combustion pressure sensor 10 is, as shown in FIG. 3, due to the offset voltage due to stress in the manufacturing process (V _{1 in} FIG. 3A) and the preload. The offset voltage (V _{2 in the} same figure (B)) is canceled out, and only the pressure detection voltage becomes,
Output voltage when maximum pressure is detected (V _{3 in} the figure (C))
Is reduced by the offset voltage offset, and the amplification factor of the amplifier can be increased.

The combustion pressure sensor 10 according to this embodiment has a working pressure range of 0 to 10 [MPa] and a pressure detection voltage at that time of 0 to 50 [mV]. 4A shows the relationship between the pressure value detected by the combustion pressure sensor 10 and the output of the combustion pressure sensor 10, and FIG. 4B shows the pressure detected by the combustion pressure sensor 10 and the combustion pressure sensor 10. Shows the relationship with the output amplified by an amplifier. The solid line in the figure shows the relationship when the offset voltage is canceled, and the broken line in the figure shows the relationship when the offset voltage is 100 [mV]. Show.

As shown in FIG. 1A, the combustion pressure sensor 10
Outputs a voltage proportional to the applied pressure within the working pressure range. As shown by the broken line in the figure, when the offset voltage of the combustion pressure sensor 10 is 100 [mV], the maximum output voltage is 150 [ mV]. When the driving voltage of the amplifier is 5 [V], its output range is generally 0 to 3
Since it is about [V], the amplification factor is determined to be 20 times as shown in FIG. 7B, and the pressure detection signal is 2 to 3 [V] in the output range of the amplifier.

In this case, when the output of the amplifier is quantized by a 10-bit A / D converter in the 5 [V] range, the pressure detection signal has a change range of only 1 [V], so the pressure resolution is 10 [MPa]. / (2 ¹⁰ /5)=0.049 [MP
a].

Similarly, when the offset voltage of the combustion pressure sensor 10 is canceled, the maximum value of the output voltage is 50.
[MV], the amplification factor of the amplifier is determined to be 60 times,
Since the entire range of the output range 0 to 3 [V] of the amplifier can be set as the change range of the pressure detection signal, if the 10-bit A / D converter in the 5 [V] range is quantized, the change range of the pressure detection signal is changed. Becomes 3 [V], the pressure resolution is tripled, and the capacity is 0.016 [MPa].

Thus, the combustion pressure sensor 1 according to this embodiment
0 indicates the offset voltage of the combustion pressure sensor 10 itself by offsetting the positive output electrode 3 to the negative input electrode 5 side and the negative output electrode 2 to the positive input electrode 4 side, respectively. Since it can be set to the negative side, the offset voltage due to the preload or the like can be canceled and the change range of the pressure detection signal can be widened.

In this embodiment, as a method of giving a predetermined potential difference to the positive output electrode 3 and the negative output electrode 2, a means for offsetting the arrangement positions of the positive output electrode 3 and the negative output electrode 2 is used. However, the present invention is not limited to this, and for example, the arrangement positions of the positive side input electrode 4 and the negative side input electrode 5 are changed, or the shape of each electrode is changed to arrange each electrode so as to give the same effect. Just set it up.

Further, since a method such as sputtering is generally used as a method for forming an electrode on the Si single crystal body 1, the electrode position can be easily changed by changing the mask, and thus the electrode is formed. By cutting the electrodes by laser scribing, the same effect as changing the position can be provided. In this way, the combustion pressure sensor 10 according to the present embodiment can easily improve the pressure detection accuracy without any circuit change or addition in the system.

[0031]

As described above, according to the present invention, by setting a negative offset voltage in advance between the positive output electrode and the negative output electrode, the offset voltage due to stress in the manufacturing process of the combustion pressure sensor, and It is possible to cancel the offset voltage due to the preload generated when the combustion pressure sensor is assembled. Therefore, the change range of the pressure detection signal based on the pressure detection voltage output from the combustion pressure sensor can be set large, and the detection accuracy of the in-cylinder pressure of the internal combustion engine is improved.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a combustion pressure sensor according to the present invention.

FIG. 2 is an example of a simulation result of an electrode arrangement and an electric potential distribution (equipotential line) of an embodiment of the combustion pressure sensor according to the present invention.

FIG. 3 is a diagram showing an output voltage of an embodiment of a combustion pressure sensor according to the present invention.

FIG. 4 is a diagram showing a relationship between a pressurizing force and an output of an embodiment of a combustion pressure sensor according to the present invention.

FIG. 5 is a front view of a conventional combustion pressure sensor.

FIG. 6 is a diagram showing an output voltage after amplification of an output of a conventional combustion pressure sensor.

[Explanation of symbols]

 1 Si single crystal body 2 Negative side output electrode 3 Positive side output electrode 4 Positive side input electrode 5 Negative side output electrode 10 Combustion pressure sensor

Claims (1)

[Claims] 1. A (110) plane of a crystal is formed as a surface to which a pressure is applied, and a Si single crystal body is opposed to the Si single crystal body in a direction of 45 ° from a (001) direction of the crystal. A pair of first electrodes provided as A pair of second electrodes provided opposite to each other in a direction of 45 ° from the direction, and one of these first and second electrodes is used as an output electrode and the other is used as an input electrode. A combustion pressure sensor, wherein each electrode is arranged so that the potential of the positive side output electrode when driven by a constant voltage is lower than the potential of the negative side output electrode by a predetermined potential.