JP4720883B2 - Pressure sensor output processing device and pressure sensor device - Google Patents

Description

  The present invention relates to a sensor output processing device for a pressure sensor. The present invention also relates to a pressure sensor device including a pressure sensor and its sensor output processing device.

  For example, a pulsating combustion pressure in an engine cylinder is detected by a pressure sensor, and the ignition timing of the engine is controlled using the sensor output value. In general, the sensor output value is obtained by superimposing an offset value due to various factors (a value that appears as a sensor output despite the applied pressure being zero) on a value corresponding to the magnitude of the pressure. ing. This offset value appears as the bottom value of the pulsation waveform when the acting pressure changes pulsatingly like the combustion pressure.

If this offset value is always constant, there is no problem because a value corresponding to the magnitude of pressure can be uniquely determined from the sensor output value. However, this offset value is generally temperature dependent. That is, the offset value changes depending on the temperature change in the environment where the pressure sensor is placed. Therefore, when the pressure is detected in an environment where the temperature change is large due to the engine load fluctuation as in the engine cylinder, the offset value can also change greatly.
Therefore, in order to accurately detect the magnitude of the acting pressure, it is desired to detect the magnitude of the pressure from a value obtained by reducing the influence of the offset value from the sensor output value.

  A configuration of a sensor output processing circuit for reducing the influence of an offset value from an output value of a pressure sensor is disclosed in Patent Document 1 by the present applicant. FIG. 24 shows a configuration diagram of the sensor output processing circuit. FIG. 25 shows an output voltage waveform of the pressure sensor 224 shown in FIG.

JP-A-6-34455

Sensor output processing circuit shown in FIG. 24, a current source 222, a voltage detector 206 for detecting an output voltage V1 of the pressure sensor 224, for sampling the voltage detected by the voltage detector 206 at the timing _{T 0} and _{T 1} a sampling signal generator 204 for generating a sampling signal, a register (digital memory) 208 for storing the detected voltage value _V 1 _{(T 0)} at the timing _{T 0,} the detected voltage value _V 1 at the timing _{T 1} (T ₁ ) and a calculation unit 212 that calculates a difference between the detection voltage value V ₁ (T ₁ ) and the detection voltage value V ₁ (T ₀ ).
Incidentally, in FIG. 25, the timing of the sensor output voltages V ₁ which varies in a pulsatile manner reaches a peak value of T _1. One of the timing in which the sensor output voltage V ₁ is the bottom value is a T _0.

This sensor signal processing circuit stores the detection voltage data V ₁ (T ₀ ) at timing T _{0 in} the register 208 in synchronization with the sampling signal generated at timing T ₀ from the sampling signal generator 204. Further, the detection voltage data V ₁ (T ₀ ) at the timing T ₁ is stored in the register 210 in synchronization with the sampling signal generated at the timing T ₁ from the sampling signal generator 204. In addition, the arithmetic unit 212 obtains a difference between the detected voltage value V ₁ (T ₁ ) at the timing T ₁ stored in the register 210 and the detected voltage V ₁ (T ₀ ) at the timing T ₀ stored in the register 208. . As a result, a value V ₂ = V ₁ (T ₁ ) −V ₁ (T ₀ ) obtained by substantially removing the influence of the offset value V ₁ (T ₀ ) from the detected voltage value V ₁ (T ₁ ) can be obtained. .

The sensor signal processing circuit, the detected voltage value _{V 1 (T} 1) at the timing _{T 1,} has a configuration that takes the difference between the detected voltage value _V 1 _{(T 0)} at the timing _{T 0} before the time _{T 1.} Therefore, a configuration (sampling signal generator 204 or the like) for sampling the detected voltage values V ₁ (T ₀ ) and V ₁ (T ₁ ) at the timings T ₀ and T ₁ is necessary. In addition, there is a problem that sampling noise occurs during sampling. Furthermore, a configuration (registers 208, 210, etc.) for storing the detection voltage values V ₁ (T ₀ ) and V ₁ (T ₁ ) at the timings T ₀ and T ₁ is necessary. Thus, according to the conventional sensor output processing circuit, there is a problem that a complicated configuration is required to reduce the influence of the offset value from the output value of the pressure sensor.

An object of this invention is to provide the pressure sensor output processing apparatus or pressure sensor apparatus which can reduce the influence of an offset value from the output value of a pressure sensor with a simple structure compared with the past.
Another object of the present invention is to provide a technique in which this sensor output processing device or pressure sensor device is further improved.
The present invention seeks to achieve at least one of the above objects.

A pressure sensor output device embodying the present invention includes bottom value hold means, timing detection means, hold means, and differential means. The bottom value holding means has a capacitor. The capacitor is charged following the output of the pressure sensor when the output of the bottom value hold means exceeds the output of the pressure sensor, and spontaneously discharges when the output of the bottom value hold means falls below the output of the pressure sensor. The timing detection means detects the timing at which the output of the bottom value hold means switches from a state exceeding the output of the pressure sensor to a state below it. The hold means holds the output of the bottom value hold means at the timing detected by the timing detection means. The differential means takes the difference between the output of the pressure sensor and the output of the hold means.
Here, it referred to herein as "differential unit" may be such as to amplify the difference with a difference of outputs of the hold condition means of the pressure sensor. Further, the value after predetermined processing (such as amplification) is applied to the output value of the pressure sensor may be such as to take the difference between the values after the predetermined processing has been performed on-hold means .

The apparatus of the present invention, in the steep discharge characteristics of the capacitor of the bottom value holding means (by shortening the discharge time), increasing the responsiveness of the output of the bottom-value hold means, the bottom value of the output of the pressure sensor even when the variation is large, there is a merit that it is possible to follow the output of the bottom-value hold means to the variation. On the other hand, increasing the responsiveness of the output of the bottom-value hold means has the disadvantage that it becomes progressively away value from the bottom value of the output of the pressure sensor over time.

In contrast, the present inventors have found that by providing the-hold means and timing detecting means, has succeeded in improving its disadvantages. That is, high response of the output of the bottom-value hold means, even when the output of the bottom-value hold means is gradually away value from the bottom value of the output of the pressure sensor, bottom value holding using a timing detection means timing output means is switched to a state below the state exceeds the output of the pressure sensor, that detects the timing at which the output of the pressure sensor becomes the new bottom value, hold condition means of Rubo Tom value hold means put on the timing Hold the output. Thus, it is possible to sufficiently follow the output of the bottom-value hold means to the variation of the bottom value of the output of the pressure sensor, the output of the-hold means, be accurately detects the bottom value of the output of the pressure sensor it can. Therefore, the magnitude of the acting pressure can be detected with high accuracy from the difference between the output of the pressure sensor obtained by the differential means and the output of the hold means.
Therefore, according to the apparatus of the present invention, even when high responsiveness of the output of the bottom-value hold means, while enjoying the benefits can improve the disadvantage.

  The correction means preferably corrects the change in the device output by adjusting the current value or voltage value of the driving current source or voltage source of the pressure sensor. Alternatively, the correction means preferably corrects the change in the device output by adjusting the resistance value of the variable resistor provided in the device. Alternatively, the correction unit preferably corrects the change in the device output by adjusting the amplification degree of the amplification unit provided in the device.

The present invention is also embodied in any of the pressure sensor output processing devices described above and a pressure sensor device including a pressure sensor.
According to the present invention, a pressure sensor output processing device having the above-described utility and a useful pressure sensor device including the pressure sensor are realized.

In the above apparatus, pressure sensor preferably has a piezoresistive element whose electric resistance value varies according to the stress applied.
The electrical resistance value of the piezoresistive element changes depending on the temperature. Therefore, in the pressure sensor using this piezoresistive element, the offset value is likely to change according to the temperature change. For this reason, when the pressure sensor output processing device described above is used for a pressure sensor having such a piezoresistive element, a more useful effect can be exhibited.

  Here, the pressure sensor includes a force detection block having a piezoresistive element, and a force transmission block that is arranged adjacent to the force detection block and transmits a force due to acting pressure to the piezoresistive element. It is preferable that the force detection element which has is provided.

In the above apparatus, the piezo resistive element is preferably a single gauge configuration. However, it can also be applied to a Wheatstone bridge configuration.
The single gauge configuration has the advantage of being able to have two to four wires connecting the electrodes and terminals, compared to the Wheatstone bridge configuration, which normally requires four electrodes. On the other hand, there is no temperature compensation structure as in the Wheatstone bridge configuration. Therefore, in a pressure sensor using a piezoresistive element having a single gauge configuration, the offset value is likely to change greatly according to a temperature change as compared with the sensor output. For this reason, when any of the pressure sensor output processing devices described above is used for a pressure sensor having such a piezoresistive element having a single gauge configuration, a more useful effect can be exhibited.
The “single gauge configuration” here is not limited to one piezoresistive element. For example, even if four piezoresistive elements are formed, they can be regarded as equivalently one piezoresistive element. included.

(First Reference Embodiment) FIG. 1 shows a configuration diagram of a combustion pressure sensor device of a first reference embodiment.
The combustion pressure sensor device of the first reference form includes a combustion pressure sensor 24 and a sensor output processing circuit for the combustion pressure sensor 24. The sensor output processing circuit includes a current source 22, a bottom value hold circuit 50, and a differential amplifier 62.
The combustion pressure sensor 24 has a piezoresistive element 46 whose electric resistance value changes according to the applied stress as a gauge part. A constant current is passed from the current source 22 to the piezoresistive element 46. When pressure (stress) is applied to the piezoresistive element 46 in a state where a constant current is passed through the piezoresistive element 46 and its resistance value changes, the voltage (output voltage) V ₁ appearing at both ends also changes in resistance value. It changes according to.

The output voltage V ₁ of the combustion pressure sensor 24 is input to the positive phase input terminal of the differential amplifier 58 that constitutes the bottom value hold circuit 50. The output voltage V ₁ branches and is also input to the positive phase input terminal of the differential amplifier 62. The output voltage V ₂ of the bottom value hold circuit 50 is input to the negative phase input terminal of the differential amplifier 62. Further, the output voltage V ₂ is branched and can be taken out from the output terminal 66. Differential amplifier 62 takes an output voltage V ₁ of the combustion pressure sensor 24 is input to the positive phase input terminal, the difference between the output voltage V ₂ of the bottom value hold circuit 50 which is input to the inverting input terminal, a predetermined amplified by the amplification degree, and outputs it to the terminal 68 as _{V 3.} The differential amplifier 62 is provided with a terminal 64 for setting the base voltage _Vbb .

FIG. 2 shows a configuration example of the combustion pressure sensor 24. The combustion pressure sensor 24 includes an outer housing 26, an inner housing 28, a heat insulating member 30, a sensor portion 32, a hermetic terminal 36, an elongated terminal 38, a wire 34, and the like. Note that the right side in FIG. 2 is the front end side, and the left side is the rear end side.
An inner housing 28 is accommodated in the outer housing 26. The inner housing 28 is made of metal, and includes a diaphragm portion 28a formed at the front end portion and a cylindrical portion 28b. The heat insulating member 30 is attached to the rear end surface of the diaphragm portion 28a. The sensor unit 32 is placed on and fixed to the hermetic terminal 36. The elongated terminal 38 extends through the cavity of the hermetic terminal 36 toward the rear end side. The front end (front end of the hemisphere) of the sensor unit 32 is in contact with the rear end surface of the heat insulating member 30.

  FIG. 3 shows a schematic perspective view of the sensor portion (force detection element) 32 of the combustion pressure sensor 24. FIG. 4 shows an electrical configuration of the sensor section (force detection element) 32 of the combustion pressure sensor 24. The force detection element 32 as a sensor unit includes a force detection block 48 and force transmission blocks 40 and 42. The force detection block 48 is made of a silicon substrate and has four elongated and mesa stepped protrusions, and piezoresistive elements 46a to 46d are formed in the protrusions. Among these, the resistance values of the piezoresistive elements 46a and 46c change when stress is applied, and the resistance values of the piezoresistive elements 46b and 46d hardly change even when the stress is applied (FIG. 4A). )reference). The rectangular parallelepiped first force transmission block 42 is made of glass and is anodically bonded to the force detection block 48. The hemispherical second force transmission block 40 is made of metal such as iron and is bonded to the first force transmission block 42. Note that the second force transmission block 40 may also be formed of silicon or glass.

  The four piezoresistive elements 46a to 46d are arranged in a square shape. Electrodes 44a to 44d are formed at positions extending outward from the four corners of the square piezoresistive elements 46a to 46d. As shown in FIG. 4A, the electrodes 44a and 44d are both connected to the current source 22 (see FIG. 1). The electrodes 44b and 44c are both grounded. For this reason, the electrical configuration of the force detection element 32 is equivalent to the configuration shown in FIG. That is, the configuration of FIG. 4A is equivalent to the configuration in which the current source 22 is connected to the piezoresistive element 46 having a single gauge configuration in which the piezoresistive elements 46a and 46c are connected in parallel as shown in FIG. 4B. It becomes.

  As shown in FIG. 2, a part of the elongated terminal 38 protrudes from the front end face of the hermetic terminal 14. Although only two elongated terminals 38 are shown in FIG. 2, there are actually four terminals 38. The four electrodes 34 a to 34 d (see FIG. 3) and the four elongated terminals 38 are associated with each other in a one-to-one relationship via the wires 34.

In the combustion pressure sensor 24, when pressure is applied to the diaphragm portion 28a, the heat insulating member 30 is displaced to the rear end side by the deflection of the diaphragm portion 28a. When the heat insulating member 30 is displaced to the rear end side, compressive stress acts on the piezoresistive elements 46 (46a, 46c) of the force detecting block 48 of the sensor unit (force detecting element) 32 that contacts the heat insulating member 30. As a result, the resistance value of the piezoresistive element 46 (46a, 46c) changes. The output voltage corresponding to the change in the resistance value appears as V ₁ at the electrode 44a (or 44d) as shown in FIG. 4B. By using this output voltage V _1, it can detect the amount of pressure applied to the diaphragm portion 28a.

  Next, the bottom value hold circuit 50 shown in FIG. 1 will be described in detail. The bottom value hold circuit 50 includes a differential amplifier 58, a diode 60, a bottom value hold capacitor 54, a resistor 56 as a discharging means for the capacitor 54, and a power source 52. The negative phase input terminal of the differential amplifier 58 is connected to the output unit 61 of the bottom value hold circuit 50. The cathode side of the diode 60 is connected to the output terminal of the differential amplifier 58. The anode side of the diode 60 is connected to the output unit 61 of the bottom value hold circuit 50. The output unit 61 is further connected to one end of a capacitor 54 and a resistor 56 connected in parallel. A power source 52 is connected to the other end of the capacitor 54 and the resistor 56 connected in parallel.

The operation of the bottom value hold circuit 50 will be described with reference to FIGS. FIG. 5 shows voltage waveforms at various parts of the combustion pressure sensor device of the first reference embodiment. FIG. 6 is an explanatory diagram of the operation of the bottom value hold circuit 50.
_V 1 _~V 3, _{V X} of FIG. 5 is the same as the _V 1 _~V 3, _{V X} in FIG. That is, V ₁ is the output voltage of the combustion pressure sensor 24. V ₂ is an output voltage of the bottom value hold circuit 50. V ₃ is an output voltage of the differential amplifier 62. V _X is an output voltage of the differential amplifier 58 constituting the bottom value hold circuit 50.
The bottom value hold circuit 50 is broadly different in operation when V ₂ <V ₁ and when V ₂ = V ₁ .
As shown in FIG. 5, in one cycle of the pulsation waveform constituting the output voltage V ₁ of the combustion pressure sensor 24, V ₂ <V ₁ in about 90% from the beginning, and V in the remaining about 10%. ₂ = _{V 1} to become. However, this ratio changes depending on a time constant determined by element values of a capacitor 54 and a resistor 56 described later.

As shown in FIG. 6A, when V ₂ <V ₁ , the differential amplifier 58 is in the comparator state, and the output voltage V _X of the differential amplifier 58 is V _Hi . V _X = (regarded as equivalent to the switch) is diode when _{V Hi} so 60 is turned off, the voltage value _{V P} of the power supply or the like 52 is set. When the diode 60 is off, the charge accumulated in the capacitor 54 is discharged through the resistor (discharge means) 56 when the diode 60 described later is on. In the state where the diode 60 is off, the output voltage V ₂ of the bottom value hold circuit 50 is the difference V _P −V _C between the voltage value V _P of the power supply 52 and the voltage across the capacitor 54. V _P is constant, _{V C} is because gradually decreases due to the discharge of the capacitor 54, _{V 2} gradually increases (see FIG. 5). The degree of increase in V ₂ (the slope of the _{V 2)} is determined by the time constant of the capacitor 54 the resistor 56. When the time constant is increased, the response of V ₂ is lowered. In other words, the degree of increase of V ₂ becomes gentle. Conversely, when the time constant is reduced, the response of V ₂ increases. In other words, the degree of increase of V ₂ will be steep.

On the other hand, when the diode 60 is off, as shown in FIG. 5, when V ₂ gradually increases and V ₁ gradually decreases beyond the peak value, a state where V ₂ > V ₁ occurs. , _{V 2} is larger than _{V X,} the diode 60 is turned on.
When the diode 60 is turned on, as shown in FIG. 6B, the circuit including the differential amplifier 58 is in a voltage follower state. As a result, when the forward voltage (ON voltage) of the diode 60 is V _D , V ₂ = V ₁ = V _X + V _D. When the diode 60 is on, the capacitor 54 is charged so that the voltage V _C between both ends thereof becomes the difference V _P −V ₂ between the voltage value V _P of the power supply 52 and the output voltage V ₂ of the bottom value hold circuit 50. Is done.

Furthermore, as shown in FIG. 5, when V ₁ gradually decreases and reaches a bottom value and then starts to rise again, V ₂ <V ₁ again, and the diode 60 is turned off. Thus, the bottom value hold circuit 50, and the boundary of the bottom value of the output voltage V ₁ of the combustion pressure sensor 24, the diode 60 is switched from ON to OFF. As a result, V ₂ gradually increases according to the time constant of the capacitor 54 and the resistor 56 described above due to the discharge of the capacitor 54.
In this way, the bottom value hold circuit 50 is configured to hold the bottom value of the pulsation waveform V _{1 that} changes intermittently and greatly as the output of the combustion pressure sensor 24 using the capacitor 54 for holding the bottom value. ing.

As shown in FIG. 7 (a), the output voltage _{V 1} of the combustion pressure sensor 24, respectively to a voltage value _{V A1, V A2, V A3} corresponding to the magnitude of the combustion pressure, the offset voltage value (bottom voltage value) V _B1 , V _B2 , and V _B3 are superposed values. The offset voltage values V _B1 , V _B2 , and V _B3 vary depending on the temperature of the environment where the combustion pressure sensor 24 is disposed.
There are various factors that cause the offset value, but it can be roughly divided into the following two factors. The first is a case where the applied pressure is zero, but force is applied to the sensor unit (force detection element 32) for some reason. Second, although the acting pressure and the force applied to the sensor unit 32 are zero, the resistance value of the sensor element (piezoresistive element 46) when the acting pressure is zero is a reference value assumed in advance. It is a case where it deviates from.

  As an example of the former, there is a preload applied to the force detection element 32 shown in FIG. That is, by applying a preload to the force detection element 30, an offset value is superimposed on the output of the combustion pressure sensor 24. This amount of preload varies with temperature. This is because the coefficient of thermal expansion of the metal constituting the inner housing 28 is larger than that of the silicon substrate 48 or the like constituting the force detection element 32. For example, when the temperature becomes high, the length that the cylindrical portion 28b of the inner housing 28 thermally expands to the front end side is longer than the length that the force detection element 32 thermally expands to the front end side (right side in FIG. 2). Therefore, the preload amount is reduced. As a result, the offset value also decreases. Conversely, when the temperature is low, the offset value increases in this case.

  As an example of the latter, when the resistance value of the sensor element has temperature dependence and the actual resistance value changes from the reference resistance value that is assumed in advance due to the temperature change, the change amount is offset. Value. In addition, for a sensor element whose actual resistance value has changed from a preliminarily assumed reference resistance value due to variations in manufacturing of the sensor element, the amount of change becomes an offset value.

  In particular, the offset value due to the latter factor changes greatly depending on the temperature change when the sensor element is a piezoresistive element and has a single gauge configuration. This is because the single gauge configuration has a useful advantage that the number of wires can be reduced to two, but the temperature compensation structure is not taken. For this reason, when a piezoresistive element having a single gauge configuration is used, it is strongly desired to take measures against an offset value that varies greatly according to temperature.

In the combustion pressure sensor device of the first reference embodiment, measures against this offset value are effectively taken. The combustion pressure sensor device, in the differential amplifier 62, the output voltage V ₁ of the combustion pressure sensor 24 that the offset voltage value is superimposed, the difference between the output voltage (corresponding to an offset voltage value) V ₂ of the bottom value bold circuit 50 Then, it is amplified at a predetermined amplification degree. As a result, from the differential amplifier 62, as shown in FIG. _7B , a constant base set by the base voltage setting terminal 64 to values V _C1 , V _C2 and V _{C3 obtained} by amplifying V ₁ -V ₂ is obtained. the value _{V 3} the voltage value _{V bb} superimposed is output. Thus, according to the combustion pressure sensor device of the first reference embodiment, it is possible to obtain the voltage value V ₃ from which the influence of the offset voltage value included in the output voltage V ₁ of the combustion pressure sensor 24 is substantially removed. Thus, from the voltage value V _3, it can be accurately detect the magnitude of the combustion pressure.

The combustion pressure sensor device of the first reference embodiment, as described above, by the bottom value hold circuit 50 having a capacitor 54 for bottom value holding, the bottom value from the hold value of the output voltage V ₁ of the combustion pressure sensor 24, The offset voltage value is obtained approximately. Therefore, as in the conventional sensor output processing circuit shown in FIG. 22, the configuration for sampling the output of the pressure sensor 224 (sampling signal generator 204, etc.) and the output value of the pressure sensor sampled at a predetermined timing are stored. For this purpose (registers 208, 210, etc.) are not required.
Therefore, according to the combustion pressure sensor device of the first reference embodiment, the influence of the offset voltage value can be almost eliminated from the output voltage V1 of the combustion pressure sensor 24 with a simpler configuration than the conventional _one .

(Modification of First Reference Embodiment) The piezoresistive element of the sensor section 32 of the combustion pressure sensor device of the first reference embodiment may be configured as a Wheatstone bridge as shown in FIG. In the configuration of FIG. 8, the voltage V1a at the connection between the piezoresistive elements 47a and 47d and the voltage V1b at the connection between the piezoresistive elements 47b and 47c are input to the differential amplifier 57, and the difference V1a−V1b between them is amplified. The value is the output V1. In the combustion pressure sensor device having the Wheatstone bridge configuration as shown in FIG. 8, since the resistance temperature characteristic is compensated, the configuration as in the first reference embodiment seems unnecessary. However, even in the combustion pressure sensor device having the Wheatstone bridge configuration, the offset due to the preload (preload) as described above occurs. This offset varies with temperature. Therefore, the configuration of the first reference embodiment is also effective for a combustion pressure sensor device having a Wheatstone bridge configuration. However, since the offset output of the Wheatstone bridge configuration is basically only for the preload, the offset amount with respect to the sensor output is small compared with the single gauge configuration, and its influence is small. Therefore, the configuration of the first reference embodiment is also effective in the Wheatstone bridge configuration, but can be more effective in the single gauge configuration.

(Problem to be improved) In the combustion pressure sensor device according to the first reference embodiment, the bottom value hold circuit 50 is increased by increasing the time constant C _B R _B of the capacitor 54 having the capacitance value C _B and the resistor 56 having the resistance value R _B. The output responsiveness of the becomes low. That is, increase of the output voltage V ₂ becomes gentle. Therefore, when the fluctuation of the bottom value of the output voltage V ₁ of the combustion pressure sensor 24 is small, the output voltage V ₂ of the bottom value hold circuit 50, the offset value of the output voltage V ₁ of the combustion pressure sensor 24 accurately detects it can. Therefore, there is a merit that the output voltage V ₃ of differential amplifier 62, the magnitude of the pressure applied to the combustion pressure sensor 24 can be accurately detected.
On the other hand, the time increasing the constant C _B R _B, Lowering the responsiveness, as shown in FIG. 8 (a), in the direction in which the bottom value V _B of the output voltage V ₁ of the combustion pressure sensor 24 rises when fluctuations, the output voltage V ₂ of the bottom value hold circuit 50 to the change that is sufficiently follow difficult. Number of cycles of this result, even if it constant in each period of the magnitude of the applied combustion pressure (the magnitude of the pressure variation) is pulsation waveform, the output voltage V ₃ of differential amplifier 62, the pulsation waveform As the value increases, the bottom value gradually increases as shown in FIG. For this reason, there exists a demerit that the detection precision of the magnitude | size of the combustion pressure which acts on the combustion pressure sensor 24 falls. If the magnitude of the acting combustion pressure is constant in each cycle of the pulsation waveform, as shown in FIG. 9B, the output voltage V _{3 of the} differential amplifier 62 even if the number of cycles of the pulsation waveform increases. Ideally, the peak value and the bottom value are constant.

In contrast, reducing the constant C _B R _B when the capacitor 54 resistor 56, the response of the output of the bottom value hold circuit 50 becomes high. That is, increase of the output voltage V ₂ becomes steeper. Therefore, even when the bottom value V _B of the output voltage V ₁ of the combustion pressure sensor 24 changes in the increasing direction, there is an advantage that the output voltage V ₂ of the bottom value hold circuit 50 can follow the fluctuation.
On the other hand, the time decrease the constant C _B R _B, the higher the above response, if rising of the bottom value of the output voltage V ₁ of the combustion pressure sensor 24 is gradual, the output voltage of the bottom value hold circuit 50 V ₂ has a demerit that it gradually becomes away from the bottom value of the output voltage V ₁ of the combustion pressure sensor 24 as time elapses.

The following second reference embodiment to the fourth reference embodiment and the first embodiment is to provide a technique or the like may improve the trade-off problem of the constant C _B R _B when the.

(Second Reference Embodiment) FIG. 10 shows the configuration of the combustion pressure sensor device of the second reference embodiment. In FIG. 11, the voltage waveform of each part of the combustion pressure sensor apparatus of 2nd reference form is shown.
The combustion pressure sensor device of the second reference embodiment further includes adders 85 and 87, differential amplifiers 86 and 88, and a reset signal generation circuit 90 in addition to the configuration provided in the combustion pressure sensor device of the first reference embodiment. ing. Further, the bottom value hold circuit 50 is provided with a reset switch 84. The reset switch 84 is constituted by a MOSFET, and its drain terminal and source terminal are connected to one end and the other end of a capacitor 54 and a resistor 56 connected in parallel, respectively. The gate terminal is connected to the output terminal of the reset signal generation circuit 90.
In the second reference embodiment, the time constant C _B R _B determined by the capacitance value C _B of the capacitor 54 and the resistance value R _B of the resistor 56 of the bottom value hold circuit 50 is increased, and the output of the bottom value hold circuit 50 is increased. The response of the voltage V ₂ is lowered (see the output voltage waveform V _{2 in} FIG. 11).

First adder 85 adds the output voltage _{V 2} and the first reference voltage _{V K1} of the bottom value hold circuit 50, and outputs the first determination voltage _{V TH1 = V 2 + V K1} . The first determination voltage V _TH1 is input to the negative phase input terminal of the first differential amplifier 86. The output voltage V ₁ of the combustion pressure sensor 24 is input to the positive phase input terminal of the first differential amplifier 86. Output voltage _{V 4} of the first differential amplifier 86, if _{V 1} is greater than _{V TH1} becomes high value, if _{V 1} is _{V TH1} smaller becomes the low value.
The second adder 87 adds the output voltage _{V 2} and the second reference voltage _{V K2} of the bottom value hold circuit 50, outputs a second determination voltage _{V TH2 = V 2 + V K2} . The second determination voltage V _TH2 is input to the negative phase input terminal of the second differential amplifier 88. The output voltage V ₁ of the combustion pressure sensor 24 is input to the positive phase input terminal of the second differential amplifier 88. The output voltage _{V 5} of the second differential amplifier 88, if _{V 1} is greater than _{V TH2} becomes high value, if _{V 1} is _{V TH2} smaller becomes the low value.

The reset signal generation circuit 90 receives the outputs of the first and second differential amplifiers 86 and 88. Reset signal generating circuit 90, while the output voltage V ₅ of the second differential amplifier 88 is low value, when the output voltage V ₄ of the first differential amplifier 86 was always high value, pulsed reset signal V _RST is output (see FIG. 11). According to this configuration, even without knowing the timing at which the output voltage V ₁ is a bottom value which changes pulsating combustion pressure sensor 24 (without providing a circuit for detecting the timing), the combustion pressure sensor 24 the bottom value of the output voltages _{V 1} is larger than _{V TH1} (i.e., the difference between the bottom value and _{V 2} of _{V 1} is becomes greater than _{V K1)} can be detected. Further, as shown in FIG. 11, the pulse-shaped reset signal V _RST is output at a timing when the output voltage V ₄ is switched from the high value to the low value.
When the reset signal _VRST is input to the gate terminal of the reset switch 84 of the bottom value hold circuit 50, the reset switch 84 is turned on, and both ends of the resistor 56 and the capacitor 54 connected in parallel are short-circuited. As a result, the electric charge accumulated in the capacitor 54 is instantaneously discharged.

As mentioned earlier, in the second referential embodiment, since the lower the responsiveness of the output voltage V ₂ of the bottom value hold circuit 50, a basically V _{2 <V 1,} as shown in FIG. 11 ing. When V ₂ <V ₁ , the diode 60 is off as described in the first reference embodiment. In a state in which the diode 60 is turned off, the both ends of the resistor 56 and the capacitor 54 are short-circuited as described above, V ₂ becomes V _P. 11, by a pulsed reset signal V _RST is outputted to the reset switch 84, the state in which V ₂ is changed in a pulse-like peak value V _P is shown. The change in _{V 2} is completed, the value of _{V 2} is _reduced, the condition to be V 2 = _{V 1} occurs. In this state, as described in the first reference embodiment, the diode 60 is on. Then, when the value of V ₁ decreases and reaches the bottom value and then starts to increase, the diode 60 is turned off, and V ₂ is set to the bottom value where V ₁ has increased, and then the bottom value is held. .

According to the second reference embodiment, as described above, the reset signal V _RST is output at the timing when the output voltage V ₄ is switched from the high value to the low value, so that the voltage V ₂ falls to the decreasing V _1. Can be made to follow. Therefore, V ₂ can be reliably set to the bottom value of V ₁ . Further, according to the second reference embodiment, as described above, the both ends of the resistor 56 and the capacitor 54 connected in parallel are short-circuited by the reset switch 84, so that the V ₂ can be reliably connected with a relatively simple configuration. it is possible to set the bottom value of V _1.
Note that, after V ₂ is set to the bottom value where V ₁ has increased, the values of V _TH1 (= V ₂ + V _K1 ) and V _TH2 (= V ₂ + V _K2 ) also increase accordingly. Therefore, even if the value of V ₂ changes, it can be reliably detected that the difference between the bottom value of V ₁ and V ₂ is greater than V _K1 .

As described above, the combustion pressure sensor device according to the second reference embodiment detects V ₂ when the reset signal generation circuit 90 detects that the difference between the bottom value of V ₁ and V ₂ is larger than the predetermined value V _K1. set the bottom value of V _1, is configured to hold the bottom value. Therefore, it is possible to avoid a situation where the difference between the bottom value and V ₂ of V ₁ is too large, a V _2, the bottom value of V ₁ can be accurately detected. Therefore, the magnitude of the acting pressure can be accurately detected from V ₆ obtained by amplifying the difference between V ₁ and V ₂ obtained by the differential amplifier 62.
Therefore, according to the combustion pressure sensor device of the second reference embodiment, even when the responsiveness of the output of the bottom value hold circuit 50 is lowered, the demerit can be improved while enjoying the merit.

(3rd reference form) The structure of the combustion pressure sensor apparatus of a 3rd reference form is shown in FIG.
In FIG. 13, the voltage waveform of each part of the combustion pressure sensor apparatus of 3rd reference form is shown.
The combustion pressure sensor device of the third reference form further includes a first bottom value hold circuit 50A, a second bottom value hold circuit 50B, and a reset signal generation circuit 91. The configuration of the bottom value hold circuits 50A and 50B is basically the same as that of the bottom value hold circuit of the first reference form, but the second bottom value hold circuit 50B includes the bottom value hold circuit of the second reference form. Similarly, a reset switch 84B is provided. The time constant determined by the capacitor 54A and the resistor 56A of the first bottom value hold circuit 50A is small (fast), and the discharge characteristics of the capacitor 54A are steep (the discharge time is short). That is, high response of the circuit output _{V 2} (see _{V 2} in FIG. 13). On the other hand, the time constant determined by the capacitor 54B and the resistor 56B of the second bottom value hold circuit 50B is large (slow), and the discharge characteristics of the capacitor 54B are gradual (discharge time is long). That is, the response of the circuit output V ₄ is low (see V _{4 in} FIG. 13).
The inverting input terminal of the differential amplifier 58A of the first bottom value holding circuit 50A, the output voltage V ₁ of the combustion pressure sensor 24 is input. Output voltage V ₂ of the first bottom value holding circuit 50A is input to the positive phase input terminal of the differential amplifier 58B of the second bottom value holding circuit 50B. The output voltage V ₄ of the second bottom value hold circuit 50 B is input to the negative phase input terminal of the differential amplifier 62 and output to the output terminal 67.

The reset signal generation circuit 91 includes an error amplifier (differential amplifier) 102, a comparator 104, and a reference power source 106. The outputs of the first and second bottom value hold circuits 50A and 50B are input to the positive phase input terminal and the negative phase input terminal of the error amplifier 102, respectively. The output of the error amplifier 102 is input to the positive phase input terminal of the comparator 104. The reference voltage V _r is input to the negative phase input terminal of the comparator 104 by the reference power source 106. The output V _RST of the comparator 104 is input to the gate terminal of the reset switch 84.

As shown in FIG. 13, as the output voltage V ₁ of the combustion pressure sensor 24 gradually increases, the first bottom value hold circuit 50 </ b> A is a value obtained by holding the bottom value of the output voltage V ₁ of the combustion pressure sensor 24. output voltage _{V 2} is also gradually increased. Since high responsiveness of the output voltage V _2, which follows well the rise of the output voltage V _1. On the other hand, the output voltage V ₄ of the second bottom value holding circuit 50B is a value obtained by holding a bottom value of the output voltage V ₂ of the first bottom value holding circuit 50A is nearly constant over the medium term from the initial 13. This is because the set lower the responsiveness of the output voltage V _4.
The difference between the output voltages V ₂ and V ₄ is amplified K times by the error amplifier 102. When the comparator 104 detects that the output K (V ₂ −V ₄ ) of the error amplifier 102 has become larger than the reference value V _r , the reset signal V _RST is output from the comparator 104 (reset signal generation circuit 91). Is output. Then, the electric charge accumulated in the capacitor 54B of the second bottom value hold circuit 50B is instantaneously discharged. The output voltage V ₄ of the second bottom value holding circuit 50B follows the variation of the output voltage V ₂ of the first bottom value holding circuit 50A, the output bottom value of the voltage V ₂ (the output voltage V ₁ of the bottom value Substantially equal).

Therefore, it is possible to avoid a situation where the difference between the bottom value and V ₄ of the V ₁ is too large, a V _4, the bottom value of V ₁ can be accurately detected. Therefore, the magnitude of the acting pressure can be accurately detected from V ₃ obtained by amplifying the difference between V ₁ and V ₄ obtained by the differential amplifier 62.
Therefore, according to the combustion pressure sensor device of the third reference embodiment, even when the output responsiveness of the second bottom value hold circuit 50B is lowered, the demerit can be improved while enjoying the merit.

(4th reference form) The structure of the combustion pressure sensor apparatus of the 4th reference form is shown in FIG. In FIG. 15, the voltage waveform of each part of the combustion pressure sensor apparatus of 4th reference form is shown.
The combustion pressure sensor device of the fourth reference embodiment further includes a timer-type reset signal generation circuit 92 in addition to the configuration provided in the combustion pressure sensor device of the first reference embodiment. Further, the bottom value hold circuit 50 is provided with a reset switch 84. The configuration of the reset switch 84 is the same as that of the second reference embodiment, and its gate terminal is connected to the output terminal of the timer-type reset signal generating circuit 92 described above.
As shown in FIG. 15, the combustion pressure sensor device of the fourth reference embodiment is configured to output a reset signal V _RST from a timer-type reset signal generation circuit 92 to the reset switch 84 every predetermined time T. The operation after the reset signal _VRST is output to the reset switch 84 is the same as in the second reference embodiment.

Fourth According to the combustion pressure sensor device of the reference embodiment, since the state in which the difference between the bottom value and V ₂ of V ₁ is spread can be avoided a situation that is left for a long time, from V _2, the V ₁ Bottom The value can be detected with high accuracy.
Therefore, according to the combustion pressure sensor device of the fourth reference embodiment, as in the second reference embodiment, even when the output responsiveness of the bottom value hold circuit 50 is lowered, the disadvantage is improved while enjoying the advantages. be able to.

(First Embodiment) FIG. 16 shows the configuration of a combustion pressure sensor device of the first embodiment. In FIG. 17 , the voltage waveform of each part of the combustion pressure sensor apparatus of 1st Embodiment is shown.
Combustion pressure sensor device of the first embodiment, in addition to the configuration combustion pressure sensor device of the first reference embodiment comprises a pulse edge detection circuit 70 further comprises a sample and hold circuit 76.
The pulse end detection circuit 70 is configured by a differentiation circuit. This differentiation circuit is constituted by a capacitor 72 and a resistor 74. One end of the capacitor 72 is connected to the output terminal of the differential amplifier 58 of the bottom value hold circuit 50. The other end of the capacitor 72 is connected to one end of the resistor 74. The other end of the resistor 74 is grounded. A connection point between the capacitor 72 and the resistor 74 is an output of the pulse end detection circuit 70.

  The sample and hold circuit 76 includes a switching element (MOSFET in this example) 78, a capacitor 80, and a voltage follower circuit 82. The gate terminal of the switching element 78 is connected to the output of the pulse end detection circuit 70 (the connection point between the capacitor 72 and the resistor 74). The drain terminal of the switching element 78 is connected to the output of the bottom value hold circuit 50. One end of a capacitor 80 is connected to the source terminal of the switching element 78 and also connected to the input terminal of the voltage follower circuit 82. The other end of the capacitor 80 is grounded.

Further, in the first embodiment, the time constant C _B R _B determined by the capacitance value C _B of the capacitor 54 and the resistance value R _B of the resistor 56 of the bottom value hold circuit 50 is reduced, and the output of the bottom value hold circuit 50 is reduced. The responsiveness of the voltage V ₂ is increased (see the output voltage waveform V _{2 in} FIG. 17).

The operation of the combustion pressure sensor device of the first embodiment will be described. The output _{V X} of the differential amplifier 58 of the bottom value hold circuit 50, as described in the first referential embodiment, _V X _{= V Hi} becomes a diode-off state, the diode ON state _{V X + V D = V 1} = V ₂ (see FIG. 17). V _D is a forward voltage of the diode 60. And when _{V X} = V _Hi, because there is a difference in the magnitude of the _{V X} in the case of _{V X + V D = V 1} = V 2, V X is a approximately a pulse-like waveform.
This V _X is input to the pulse end detection circuit 70. Since the pulse edge detection circuit 70 is constituted by a differentiation circuit, if the pulse waveform V _X is input, and outputs the waveform V ₃ of the peak-shaped part of the pulse edge of the waveform V _X. At the falling pulse end of the pulse waveform V _X , the peak waveform V ₃ is output in the negative direction. The rising pulse edge of the pulse-like waveform V _X, a positive peak-like waveform V ₃ in the direction is output. Among these, the peak-like waveform V ₃ in the negative direction is disregarded.

When a positive peak-like waveform V ₃ in the direction is input to the gate terminal of the switching element 78 of the sample-and-hold circuit 76, the switching element 78 is turned on. The timing when the switching element 78 is turned ON, a timing at which the output voltage V ₁ is a bottom value. Thus, the pulse edge detection circuit 70, the output voltages V ₁ plays a role of detecting the timing at which the bottom value.
As a result, the output voltage V ₂ (= V ₄ ) of the bottom value hold circuit 50 at the timing when the switching element 78 is turned on (the timing when the output voltage V ₁ becomes the bottom value) is the voltage follower of the sample and hold circuit 76. It is transmitted to the input unit 81 of the circuit 82. As a result, the capacitor 80 having one end connected to the input unit 81, a charge as the voltage across it becomes V ₄ is accumulated, the voltage across the hold state of V _4.

The voltage follower circuit 82 serves as a buffer, and the voltage V ₄ is output as it is to the output of the voltage follower circuit 82. This output voltage V ₄ is input to the negative phase input terminal of the differential amplifier 62. The value of the output voltage V ₄ is the same value until ON the switching element 78 again is held. That is, as shown in FIG. 17, when the bottom value of V ₁ gradually increases, the value of the output voltage V ₄ has a stepped waveform with a step at the bottom value of V ₁ . Here, the positive-phase input terminal of the differential amplifier 62, similarly to the first reference embodiment, the output voltage V ₁ of the combustion pressure sensor 24 is input.
Therefore, the output voltage V ₅ of the differential amplifier 62 is superposed with a constant base voltage V _bb on the value obtained by amplifying the difference between the output voltage V ₁ of the combustion pressure sensor 24 and the output voltage V ₄ of the sample and hold circuit 76. It becomes the value. This output voltage waveform is shown in FIG.

According to the combustion pressure sensor device of the first embodiment, even when the responsiveness of the output voltage V ₂ of the bottom value hold circuit 50 is high and V ₂ becomes a value gradually away from the bottom value of V ₁ , the sample hold from the output voltage V ₄ of the circuit 76, the bottom value of V ₁ can be accurately detected. For this reason, the magnitude of the acting pressure can be accurately detected from the value V ₅ obtained by amplifying the difference between V ₁ and V ₄ obtained by the differential amplifier 62. In addition, since the time constant C _B R _B can be reduced, an effect that the capacitor 54 having a small capacitance value C _B or the resistor 56 having a small resistance value R _B can be used can be obtained.
Therefore, according to the combustion pressure sensor device of the first embodiment, even when the responsiveness of the output of the bottom value hold circuit 50 is increased, the demerit can be improved while enjoying the merit.

( 5th reference form) The structure of the combustion pressure sensor apparatus of a 5th reference form is shown in FIG.
The combustion pressure sensor device of the fifth reference embodiment further includes a control circuit (correction circuit) 94a in addition to the configuration provided in the combustion pressure sensor device of the first reference embodiment.
The control circuit 94a detects the output voltage V ₂ of the bottom value hold circuit 50, and controls the current value of the current source 22 in response to the output voltage value V _2. More specifically, the control circuit 94a is how different or the output voltage value V ₂ detected from the reference value (or greater, including be small) is detected. If the detected output voltage value V ₂ by a predetermined value greater than the reference value decreases in accordance with value of the current flowing from the current source 22 to the size of the predetermined value. That is, even when the temperature coefficient of resistance and sensitivity temperature coefficient of the piezoresistive element 46 is positive, if the output voltage value V ₂ detected is larger than the reference value, the arrangement environment of the combustion pressure sensor 24 and a high temperature It can be assumed that the sensitivity of the piezoresistive element 46 is higher than the reference sensitivity. Therefore, in order to correct the increase in the output voltage (device output) V3 of the differential amplifier 62 accompanying the increase in sensitivity of the combustion pressure sensor 24, the value of the current flowing from the current source 22 is decreased. As a result, an increase in the output voltage V1 of the combustion pressure sensor 24 when a predetermined pressure is applied, and consequently the output voltage V3 of the differential amplifier 62, is suppressed.
On the other hand, if the output voltage value V ₂ detected is smaller by a predetermined value than the reference value, increases in accordance with value of the current flowing from the current source 22 to the size of the predetermined value, when a predetermined pressure is applied suppress decrease in the output voltage _{V 3} of differential amplifier 62.
Note that the current source 22 may be replaced with a voltage source whose voltage value can be adjusted by the control circuit 94a.

( 6th reference form) In FIG. 19, the structure of the combustion pressure sensor apparatus of the 6th reference form is shown. The combustion pressure sensor device of the sixth reference embodiment further includes a control circuit (correction circuit) 94b in addition to the configuration provided in the combustion pressure sensor device of the first reference embodiment. A variable resistor 96 is provided between the input / output terminal of the piezoresistive element 46 and the terminal of the voltage source 23.
The control circuit 94b detects the output voltage V ₂ of the bottom value hold circuit 50, adjusting the resistance value of the variable resistor 96 in accordance with the output voltage value V _2. More specifically, the control circuit 94b is a case where the resistance temperature coefficient and temperature coefficient of sensitivity of the piezoresistive element 46 is positive, if the output voltage value V ₂ detected by a predetermined value greater than the reference value, The resistance value of the variable resistor 96 is increased according to the magnitude of the predetermined value. As a result, an increase in the output voltage V ₁ of the combustion pressure sensor 24 when a predetermined pressure is applied, and consequently the output voltage V ₃ of the differential amplifier 62 is suppressed.
On the other hand, the difference in the case where the output voltage value V ₂ detected is smaller by a predetermined value than the reference value, the resistance value of the variable resistor 96 is decreased in accordance with the magnitude of the predetermined value, when a predetermined pressure is applied suppress decrease in the output voltage _{V 3} of the dynamic amplifier 62.
The variable resistor 96 may be inserted on the ground side (ground side) of the combustion pressure sensor 24.

( 7th reference form) The structure of the combustion pressure sensor apparatus of 7th reference form is shown in FIG. The combustion pressure sensor device of the seventh reference embodiment further includes a control circuit (correction circuit) 94c in addition to the configuration provided in the combustion pressure sensor device of the first reference embodiment. A variable resistor 98 and a fixed resistor 100 are connected in series between the output terminal 68 of the differential amplifier 62 and the terminal 64 for setting the base voltage _Vbb . A correction output terminal 68 a is provided at a connection portion between the variable resistor 98 and the fixed resistor 100.
The control circuit 94c detects the output voltage V ₂ of the bottom value hold circuit 50, in accordance with the output voltage value V _2, similarly to the sixth reference embodiment, by adjusting the resistance value of the variable resistor 98, the combustion pressure A value V3a obtained by correcting the change in the output voltage V3 of the differential amplifier 62 accompanying the change in sensitivity of the sensor 24 (piezoresistive element 46) is output from the correction output terminal 68a.

( Eighth Reference Embodiment) FIG. 21 shows the configuration of the combustion pressure sensor device of the eighth reference embodiment. The combustion pressure sensor device of the eighth reference embodiment further includes a control circuit (correction circuit) 94d in addition to the configuration provided in the combustion pressure sensor device of the first reference embodiment.
The control circuit 94d detects the output voltage V ₂ of the bottom value hold circuit 50, in accordance with the output voltage value V _2, adjust the amplification degree of the differential amplifier 62. More specifically, the control circuit 94d, when the output voltage value V ₂ detected by a predetermined value greater than the reference value, reduces in accordance with the amplification degree of the differential amplifier 62 to the magnitude of the predetermined value suppresses the increase in the output voltage V ₃ of differential amplifier 62 when a predetermined pressure is applied.
On the other hand, if the output voltage value V ₂ detected is smaller by a predetermined value than the reference value, increases in accordance with the amplification degree of the differential amplifier 62 to the magnitude of the predetermined value, when a predetermined pressure is applied suppress decrease in the output voltage _{V 3} of differential amplifier 62.

According to the combustion pressure sensor devices of the fifth to eighth reference embodiments, even when there is a temperature change in the environment where the combustion pressure sensor device is arranged and the sensitivity change of the combustion pressure sensor 24 occurs, a predetermined pressure is applied. The device output (output voltages V ₃ and V3a of the differential amplifier 62 in the above example) can be kept substantially constant.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
(1) In the above reference embodiment and embodiment, the combustion pressure sensor using a piezoresistive element as a sensor element has been described as an example. However, a piezoelectric element may be used as the sensor element.
(2) In the reference embodiment and the embodiment described above, the piezoresistive element has been described as having a single gauge configuration, but may have a full bridge configuration or a half bridge configuration.
(3) a second reference embodiment (see FIGS. 10 and 11) in detects the timing at which the output voltage _{V 1} is a bottom value, detects that the value of _{V 1} at the timing becomes _{V TH1} or It is good also as a structure.
(4) In the second reference mode (see FIGS. 10 and 11), the capacitor 54 and the resistor 56 of the bottom value hold circuit 50 are short-circuited by the switch element 84, so that the charge accumulated in the capacitor 54 is discharged. set V ₂ to _{V P,} to follow the _{V 1} are lowered to _{V 2,} it is to set the _{V 2} to the bottom value of _{V 1} (see FIG. 11). However, for example, V ₂ may be set to the bottom value of V ₁ by improving the response of V ₂ by switching to a sufficiently small time constant by the configuration of FIG. 22 or FIG. That is, as shown in FIG. 22, the switch 85a is turned on by a reset signal from the reset signal generation circuit 90, and a resistor 56a having a small resistance value is connected in parallel to the resistor 56, thereby switching to a small time constant. Good. Further, as shown in FIG. 23, the switch 85b may be turned off by a reset signal from the reset signal generation circuit 90, and the capacitor 54a connected in parallel to the capacitor 54 may be disconnected to switch to a small time constant. .
(5) In the fourth reference mode (see FIGS. 14 and 15), the reset signal V _RST from the reset signal generation circuit 92 is output to the reset switch 84 every predetermined time T, but the pulsation waveform V ₁ A circuit (pulsation frequency detection circuit) that counts the number of pulsations (pulse number) may be provided so that the reset signal V _RST is output to the reset switch 84 every time a predetermined number is counted. Further, the time constant determined by the capacitor and the resistance of the bottom value hold circuit 50 may be controlled (for example, switched to a plurality of stages) according to the pulsation frequency detected by the pulsation frequency detection circuit. For example, when the pulsation frequency is small, the bottom value hold circuit 50 can hold the bottom value of the pulsation waveform V ₁ even if the time constant is increased to reduce the responsiveness. Therefore, by increasing the responsiveness by reducing the time constant unnecessarily it can be avoided that an error (difference between the output V ₂ of the actual bottom value and the bottom value hold circuit 50 of the pulsation waveform V ₁₎ is increased .

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

The structure of the combustion pressure sensor apparatus of a 1st reference form is shown. The structure of a combustion pressure sensor is shown. The schematic perspective view of the sensor part (force detection element) of a combustion pressure sensor is shown. The electrical structure of the sensor part (force detection element) of a combustion pressure sensor is shown. The voltage waveform of each part of the combustion pressure sensor apparatus of a 1st reference form is shown. An explanatory view of the operation of the bottom value hold circuit is shown. The output voltage waveform of a combustion pressure sensor and the output voltage waveform of a sensor output processing circuit are shown. The structure of the combustion pressure sensor apparatus of the modification of a 1st reference form is shown. The voltage waveform of each part of the combustion pressure sensor apparatus of the first reference form when the output voltage waveform of the combustion pressure sensor gradually increases is shown. The structure of the combustion pressure sensor apparatus of a 2nd reference form is shown. The voltage waveform of each part of the combustion pressure sensor apparatus of the 2nd reference form is shown. The structure of the combustion pressure sensor apparatus of the 3rd reference form is shown. The voltage waveform of each part of the combustion pressure sensor apparatus of the 3rd reference form is shown. The structure of the combustion pressure sensor apparatus of a 4th reference form is shown. The voltage waveform of each part of the combustion pressure sensor apparatus of a 4th reference form is shown. The structure of the combustion pressure sensor apparatus of 1st Embodiment is shown. The voltage waveform of each part of the combustion pressure sensor apparatus of 1st Embodiment is shown. The structure of the combustion pressure sensor apparatus of the 5th reference form is shown. The structure of the combustion pressure sensor apparatus of the 6th reference form is shown. The structure of the combustion pressure sensor apparatus of the 7th reference form is shown. The structure of the combustion pressure sensor apparatus of the 8th reference form is shown. The structure of the combustion pressure sensor apparatus of 1st modifications, such as a 2nd reference form, is shown partially. The structure of the combustion pressure sensor apparatus of 2nd modification examples, such as a 2nd reference form, is shown partially. The structure of the sensor output processing circuit of the conventional pressure sensor is shown. The output voltage waveform of a pressure sensor is shown.

Explanation of symbols

22 Current source 24 Combustion pressure sensor 26 Piezoresistive element 50 Bottom value hold circuit 62 Differential amplifier

Claims (4)

A bottom value hold means that having a capacitor, the capacitor, the output of the bottom value hold means is charged to follow the output of the pressure sensor when exceeds the output of the pressure sensor, said bottom value holding Bottom value holding means for spontaneous discharge when the output of the means falls below the output of the pressure sensor ;
Timing detection means for detecting timing at which the output of the bottom value hold means switches from a state exceeding the output of the pressure sensor to a state below it;
Output and hold sulfo Rudo means before Kibo Tom value holding means in said timing,
The pressure sensor output processing apparatus comprising: a differential means for taking the difference between outputs of the front Kiho Rudo means of the pressure sensor. The pressure sensor output processing apparatus according to claim 1, and a pressure sensor apparatus including the pressure sensor . The pressure sensor device according to claim 2, wherein the pressure sensor includes a piezoresistive element whose electric resistance value changes according to an applied stress . The pressure sensor device according to claim 3, wherein the piezoresistive element has a single gauge configuration .

Images