JP2008275525A - Reset timing generating device and cylinder internal pressure detecting device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reset timing generating device for generating the timing to reset the offset drift of a cylinder internal pressure sensor, and a cylinder internal pressure detecting device capable of accurately detecting the cylinder internal pressure of an internal combustion engine using the reset timing generating device. <P>SOLUTION: The cylinder internal pressure detecting device 12 comprises a detecting circuit part 200 detecting the variation of resistance of a piezoresistance element 138 as an electric signal, an amplifying circuit part 201 amplifying and outputting the electric signal, and a correcting circuit part 202 correcting the output value. The correcting circuit part 202 comprises a peak hold circuit part 205 holding a peak value of output voltage of the amplifying circuit part 201; a voltage dividing circuit part 206 dividing the output voltage of the peak hold circuit part 205; a comparing circuit part 207 comparing the output voltage of the voltage dividing circuit part 206 with the output voltage of the amplifying circuit part 201; and an operation part 208 computing the timing to reset the output voltage of the amplifying circuit part 201 based on an output signal of the comparing circuit part 207. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reset timing generation device that generates a timing for resetting an output voltage of an in-cylinder pressure sensor that detects an in-cylinder pressure of an internal combustion engine, and an in-cylinder pressure detection device including the reset timing generation device.

  In recent years, in an internal combustion engine such as a diesel engine, in order to respond to demands such as improvement of fuel consumption and reduction of emissions in exhaust gas, precise operation control according to the combustion state such as control of fuel injection amount by electronic control is performed. It has become common.

  One method for grasping the combustion state of the internal combustion engine is to detect the pressure in the cylinder (hereinafter referred to as in-cylinder pressure). Therefore, the internal combustion engine is provided with an in-cylinder pressure sensor, and an electric signal corresponding to the in-cylinder pressure is output.

  However, in an environment where an abrupt temperature change occurs as in an internal combustion engine, the drift of the output voltage of the in-cylinder pressure sensor due to factors such as temperature, the so-called offset drift, cannot be avoided. Correction is essential.

As a technique for correcting such a drift, for example, a technique (for example, refer to Patent Document 1) that corrects from a value of a temperature sensor that is separately installed based on a temperature characteristic of an in-cylinder pressure sensor, or a crank angle sensor provided in an internal combustion engine Is detected from the outside, and the output voltage of the in-cylinder pressure sensor is reset to a reference value at a timing corresponding to a predetermined crank angle (for example, see Patent Document 2).
JP 2004-257888 A JP-A-7-280686

  When correcting using a temperature sensor, it is necessary to accurately detect the temperature of the drift generation factor, but in reality, the accurate temperature cannot be adjusted due to various factors such as the inability to install a temperature sensor near the drift generation factor. In many cases, it cannot be measured. Therefore, the measurement error is reflected in drift correction and may appear as a correction error. In addition, when there are multiple factors that cause drift, it is necessary to install multiple temperature sensors corresponding to all the factors, which complicates the configuration and correction processing, and increases the circuit scale associated with this. There is a risk.

  On the other hand, when the correction is performed using the crank angle sensor, a terminal for inputting a signal from the crank angle sensor must be separately provided on the in-cylinder pressure detection device (in-cylinder pressure sensor) side. Is done.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reset timing generation device that generates timing for resetting an offset drift of an in-cylinder pressure sensor, and to accurately detect the in-cylinder pressure of an internal combustion engine using the reset timing generator. An object of the present invention is to provide an in-cylinder pressure detecting device.

  Hereinafter, each configuration suitable for solving the above-described problems will be described in terms of items. In addition, the effect etc. peculiar to the structure which respond | corresponds as needed are added.

Configuration 1. The reset timing generator of this configuration is
A reset timing generation device for generating a timing for resetting an output voltage of an in-cylinder pressure sensor output in accordance with a cylinder pressure of an internal combustion engine or a change rate of the cylinder pressure of the internal combustion engine to a reference value,
Peak hold means for holding the peak value of the output voltage of the in-cylinder pressure sensor;
Voltage dividing means for dividing the output voltage of the peak hold means;
Comparing means for comparing the output voltage of the voltage dividing means and the output voltage of the in-cylinder pressure sensor, and outputting a rectangular wave signal whose output voltage level is switched according to the comparison result;
Reset timing calculation means for calculating reset timing based on an output signal of the comparison means.

  According to the configuration 1, the in-cylinder pressure waveform detected by the in-cylinder pressure sensor can be detected as a rectangular wave signal by shaping it through the peak hold means, the voltage dividing means, and the comparison means. Thereby, for example, the timing immediately after combustion of the internal combustion engine (immediately after detection of the peak value) or the like can be detected as the rising (or falling) of the rectangular wave signal. That is, information necessary for calculating the reset timing, for example, the cycle of the combustion cycle and the timing as the base point, can be obtained based on the rising edge of the rectangular wave signal. As a result, the reset timing can be calculated without using the information of the crank angle sensor, and the offset drift of the sensor output can be eliminated at the desired timing of the combustion cycle. As a result, since it is not necessary to separately provide a terminal for inputting a signal from the crank angle sensor, an increase in size of the reset timing generation device and the reset correction device including the reset timing generation device can be suppressed. In particular, when an in-cylinder pressure detection device in which the reset correction device and the in-cylinder pressure sensor are integrated is installed in an internal combustion engine, the effect of the device must be reduced in consideration of vibration durability and the like. In the above configuration, since the sensor output is corrected by resetting the output voltage of the in-cylinder pressure sensor to the reference value without grasping the temperature, it is not necessary to provide a separate temperature sensor. As a result, the in-cylinder pressure of the internal combustion engine can be accurately detected without complicating the configuration and the correction process.

  If the output voltage of the in-cylinder pressure sensor exceeds the preset voltage threshold to detect information necessary for calculating the reset timing, the drift amount is large, etc. For example, unless resetting is forcibly performed, it is feared that the output voltage of the in-cylinder pressure sensor cannot be detected and the appropriate information cannot be obtained. On the other hand, if the configuration is such that the peak value of the output waveform of the in-cylinder pressure sensor is detected as in the configuration 1, the information can be obtained more reliably even when the drift amount is large.

Configuration 2. The reset timing generation device of this configuration is the above configuration 1,
The reset timing calculating means measures the period of the rectangular wave signal output from the comparing means, and calculates the reset timing based on the period.

  According to Configuration 2, the timing for performing the reset process is obtained from the period of the rectangular wave signal corresponding to the combustion cycle of the internal combustion engine (the output waveform period of the in-cylinder pressure sensor). Note that the reset timing calculation means calculates the reset timing based on a preset arithmetic expression using the period of the rectangular wave signal as a variable. For example, a timing t + nΔt at which a time nΔt calculated by multiplying the rectangular wave period Δt by a predetermined coefficient n from a predetermined base point t (such as the rising time of the rectangular wave signal or the previous reset time) is set as the reset timing Rt. To do. In this case, an arithmetic expression necessary for calculating the reset timing from the rectangular wave period, such as Rt = t + nΔt, is a combustion cycle in which the in-cylinder pressure of the internal combustion engine becomes the lowest so that the offset drift of the sensor output is properly eliminated. The reset timing is adjusted to the desired timing. Therefore, by adopting a measurement value (variable) having a relatively long measurement time, such as the rectangular wave period Δt, as a variable for obtaining a reset timing that matches the desired timing of one combustion cycle of the internal combustion engine, The ratio of the measurement error to the value (variable) can be reduced. As a result, the measurement error of the measured value (variable) hardly affects the calculation error of the reset timing, the deviation between the actual reset timing and the desired timing can be suppressed relatively small, and the sensor output can be improved at a better timing. Correction can be performed.

Configuration 3. The reset timing generation device of the present configuration is the above-described configuration 2,
The time interval from the rising or falling point of a predetermined rectangular wave signal where the output voltage of the voltage dividing means is equal to or higher than the output voltage of the in-cylinder pressure sensor to the rising or falling point of the next rectangular wave signal is reset. The timing calculation means measures the period of the rectangular wave signal.

  According to the configuration 3, the reset timing calculation means is based on the timing when the output voltage of the voltage dividing means becomes equal to or higher than the output voltage of the in-cylinder pressure sensor, that is, the timing immediately after combustion of the internal combustion engine (immediately after detection of the peak value). The period of the square wave signal is measured.

  The timing at which the output voltage of the voltage dividing means becomes equal to or lower than the output voltage of the in-cylinder pressure sensor (for example, when the rectangular wave signal falls) is the timing at which the output voltage of the voltage dividing means becomes equal to or higher than the output voltage of the in-cylinder pressure sensor (for example, Since the peak value is farther than the detection time of the rectangular wave signal, the variation is large due to a difference in the rotational speed of the internal combustion engine. That is, according to the configuration 3, the detection error at the rising or falling time of the rectangular wave signal that is the base point of the period measurement can be suppressed to a small value. Therefore, the detection error hardly affects the calculation error of the reset timing, the deviation between the actual reset timing and the desired timing can be suppressed relatively small, and the sensor output can be corrected at a better timing. .

Configuration 4. The in-cylinder pressure detection device of this configuration is
An in-cylinder pressure sensor that outputs an electric signal in accordance with the in-cylinder pressure of the internal combustion engine or the change rate of the in-cylinder pressure of the internal combustion engine;
The reset timing generation device according to any one of configurations 1 to 3,
Reset signal output means for outputting a reset signal at the timing generated by the reset timing generator;
And reset means for resetting the output voltage of the in-cylinder pressure sensor to a reference value based on an input of a reset signal from the reset signal output means.

  According to the configuration 4, by integrating the in-cylinder pressure sensor, the reset timing generation device, and the like, it is possible to effectively use a limited installation space of the internal combustion engine and improve convenience. In addition, when this in-cylinder pressure detecting device is integrated with a glow plug or the like, the operational effect can be further enhanced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of an internal combustion engine to which an in-cylinder pressure detecting apparatus according to the present invention is attached will be described with reference to FIG. 2 taking a four-cycle diesel engine (hereinafter simply referred to as an engine) as an example. FIG. 2 is a schematic diagram showing the configuration of the engine control system.

  An intake pipe 3 and an exhaust pipe 4 are connected to the cylinder 2 of the engine 1. An intake valve 5 is provided in the intake port 3 a of the cylinder 2 connected to the intake pipe 3, and an exhaust valve 6 is provided in the exhaust port 4 a of the cylinder 2 connected to the exhaust pipe 4.

  A piston 7 is accommodated in the cylinder 2, and the piston 7 is connected to a crankshaft 9 via a connecting rod 8. In addition to the intake valve 5 and the exhaust valve 6, the tip of the glow plug 10 and the fuel injection nozzle 11 faces the space surrounded by the upper part of the piston 7 and the wall surface of the cylinder 2, that is, the combustion chamber 2a.

  The glow plug 10 incorporates an in-cylinder pressure detecting device 12 for detecting a pressure in the combustion chamber 2a of the cylinder 2 (hereinafter referred to as an in-cylinder pressure) as will be described later. The crankshaft 9 is provided with a crank angle sensor 15 that detects its rotation angle (crank angle). Detection signals from various sensors including the in-cylinder pressure detection device 12 and the crank angle sensor 15 are input to an engine control electronic control unit (hereinafter referred to as “ECU”) 18. The ECU 18 controls the fuel injection amount from the fuel injection nozzle 11 and the like based on these detection signals and a detection signal proportional to the movement of the accelerator pedal input from the throttle sensor 19.

  When fuel is injected from the fuel injection nozzle 11 with the glow plug 10 energized to generate heat, the fuel 1 is ignited and the engine 1 is started.

  Next, the structure of the glow plug 10 incorporating the in-cylinder pressure detecting device 12 according to the present invention and its mounting mode will be described with reference to FIG. FIG. 1 is a partial cross-sectional view of a cylinder head 2b to which a glow plug 10 is attached.

  The glow plug 10 is mounted in a plug mounting hole 2c formed in the sinter head 2b, and is positioned so that the tip side protrudes into the combustion chamber 2a.

  The glow plug 10 is disposed on the distal end side of the central shaft 101, a cylindrical metallic shell 100 extending along the axis C direction, a conductive rod-shaped middle shaft 101 held in the metallic shell 100, and a main body. And a rod-shaped heater member 102 protruding outward from the tip of the metal fitting 100.

  On the outer peripheral surface on the base end side of the metal shell 100, there is a male thread portion 111 for fixing the glow plug 10 to the plug mounting hole 2c of the cylinder head 2b, and a hexagonal shape for engaging a tool such as a wrench at the time of screwing. A tool engaging portion 112 is formed.

  A cylindrical heater holding member 114 in which the heater member 102 is press-fitted and held, and a seal member 115 that closes the gap between the heater holding member 114 and the tip of the metal shell 100 are provided on the front end side of the metal shell 100. ing.

  The proximal end portion of the heater member 102 is connected to the distal end portion of the middle shaft 101 by a cylindrical electrode member 116 having conductivity.

  The heater member 102 includes a base body 120 made of an insulating ceramic and a heating element 121 embedded in the base body 120. One end of the heating element 121 is electrically connected to the central shaft 101 via the electrode member 116, and the other end is electrically connected to the metal shell 100 via the heater holding member 114. As a result, when the temperature of the heater member 102 is raised, the current supplied to the heat generating element 121 through the middle shaft 101 flows through the metallic shell 100 to the sinter head 2b.

  The heater holding portion 114 is held in a state displaceable in the direction of the axis C by a holding member 119 made of self-lubricating graphite. As a result, the heater holding member 114 and the heater member 102 press-fitted into the heater holding member 114 are displaced in the direction of the axis C according to the change in the in-cylinder pressure in the combustion chamber 2a.

  A cylindrical slide pipe 126 is slidably disposed in the shaft hole 125 of the metal shell 100. The front end of the slide pipe 126 is connected to the proximal end portion of the heater holding member 114, and the push pipe 127 is connected to the rear end. Therefore, when the heater holding member 114 is displaced, the slide pipe 126 and the push pipe 127 are also displaced in the axis C direction.

  The push pipe 127 protrudes from the base end portion of the metal shell 100, and an O-ring 129 that closes the gap with the base end portion of the metal shell 100 is fitted around the push pipe 127.

  The above-described in-cylinder pressure detecting device 12 is provided on the base end side of the metal shell 100. The outer shell of the in-cylinder pressure detecting device 12 includes a cylindrical housing 131 surrounding the periphery thereof and a grommet 132 that closes the proximal end side of the housing 131. A plurality of connecting wires 133 are drawn into the in-cylinder pressure detecting device 12 through the grommet 132.

  The in-cylinder pressure detecting device 12 includes an annular base 135 attached to the base end portion of the metal shell 100 so as to surround the push pipe 127 and a base 135 in contact with the base end portion of the push pipe 127. And a diaphragm member 136 mounted on the substrate.

  The diaphragm member 136 has a thin diaphragm portion 136a, and is deformed by being pushed by the push pipe 127. Further, a piezoresistive element 138 is affixed to the diaphragm portion 136a, and the resistance value of the piezoresistive element 138 changes due to the deformation of the diaphragm member 136.

  A printed circuit board 140 is disposed on the base end side of the diaphragm member 136. On the printed circuit board 140, electronic components such as an IC are mounted, and various electronic circuits are formed. Then, when the pressure received by the heater member 102 is transmitted to the piezoresistive element 138 due to the change in the in-cylinder pressure in the combustion chamber 2a, the pressure on the printed circuit board 140 connected to the piezoresistive element 138 via the bonding wire 143 is increased. The detection circuit unit detects a change in resistance of the piezoresistive element 138 as an electric signal. The detected electrical signal is amplified by the amplification circuit unit and output to the outside as a detection signal proportional to the in-cylinder pressure. However, since a drift due to factors such as temperature occurs in the detection signal, a correction circuit section for eliminating this drift is also provided on the printed circuit board 140. Since the process of eliminating this drift is performed by resetting the output value of the amplifier circuit unit to the reference value as will be described later, this process is hereinafter referred to as “reset (reset process)”.

  One of the plurality of connection lines 133 described above is electrically connected to the proximal end portion of the central shaft 101 for supplying power to the heater member 102. The other connection lines 133 are electrically connected to the printed circuit board 140 and are used for outputting detection signals or supplying power to the printed circuit board 140.

  Here, the circuit configuration of the in-cylinder pressure detecting device 12 will be described with reference to FIG. FIG. 3 is a functional block diagram showing a circuit configuration.

  The in-cylinder pressure detection device 12 includes a detection circuit unit 200 that detects a change in resistance of the piezoresistive element 138 as an electrical signal, an amplification circuit unit 201 that amplifies and outputs the electrical signal, and a correction circuit that corrects the output value. Part 202. Among these, the piezoresistive element 138, the detection circuit unit 200, and the amplification circuit unit 201 constitute the in-cylinder pressure sensor in the present embodiment, and the correction circuit unit 202 constitutes a reset correction device.

  The correction circuit unit 202 includes a peak hold circuit unit 205 as a peak hold unit that holds the peak value of the output voltage of the amplifier circuit unit 201, and a voltage dividing circuit as a voltage dividing unit that divides the output voltage of the peak hold circuit unit 205. The comparison circuit unit as a comparison unit that compares the output voltage of the unit 206 with the output voltage of the voltage dividing circuit unit 206 and the output voltage of the amplification circuit unit 201 and outputs a rectangular wave signal whose output voltage level is switched according to the comparison result 207, a calculation unit 208 as a reset timing calculation unit that calculates a reset timing based on an output signal of the comparison circuit unit 207, and a reset signal output unit 209 as a reset signal output unit that outputs a reset signal at the calculated timing And the output power of the amplifier circuit unit 201 based on the input of the reset signal from the reset signal output unit 209. And a reset circuit section 210 as a reset means for resetting to the reference value. Among them, the peak hold circuit unit 205, the voltage dividing circuit unit 206, the comparison circuit unit 207, and the calculation unit 208 constitute a reset timing generation device in the present embodiment.

  Here, the circuit configuration of the peak hold circuit unit 205, the voltage dividing circuit unit 206, and the comparison circuit unit 207, which are main parts of the present invention, will be described in detail with reference to the circuit diagram of FIG.

  The peak hold circuit unit 205 includes two operational amplifiers OP1 and OP2 for converting input and output impedances, and a capacitor C1 that holds the peak value of the output voltage of the amplifier circuit unit 201.

  The operational amplifier OP1 functions as a buffer circuit for signal input from the amplifier circuit unit 201, and the output terminal 201a of the amplifier circuit unit 201 is connected to the non-inverting input terminal.

  The anode side of the rectifying diode D1 is connected to the output terminal of the operational amplifier OP1. The non-inverting input terminal of the operational amplifier OP2 is connected to the cathode side of the diode D1, and one end of the capacitor C1 is connected. The other end of the capacitor C1 is grounded.

  A discharge resistor R1 is connected in parallel to the capacitor C1. The resistor R1 discharges the electric charge stored in the capacitor C1 with a constant time constant determined by the capacitance of the capacitor C1 and its own resistance value.

  The operational amplifier OP2 has its output terminal connected to its inverting input terminal and also connected to the inverting input terminal of the operational amplifier OP1 via the resistor R2, and functions as a buffer circuit for signal output.

  A rectifying diode D2 is connected in parallel between the output terminal and the inverting input terminal of the operational amplifier OP1. Specifically, the anode side of the diode D2 is connected to the inverting input terminal of the operational amplifier OP1, and the cathode side is connected to the output terminal of the operational amplifier OP1 and the anode side of the diode D1.

  The voltage dividing circuit unit 206 includes two resistors R3 and R4 connected in series. The output terminal of the operational amplifier OP2 is connected to one end of the resistor R3, and one end of the resistor R4 is grounded.

  A non-inverting input terminal of a comparator CMP constituting the comparison circuit unit 207 is connected between the resistors R3 and R4. The output terminal 201a of the amplifier circuit unit 201 is connected to the inverting input terminal of the comparator CMP, and the input terminal 208a of the arithmetic unit 208 is connected to the output terminal of the comparator CMP.

  Next, the flow of reset timing generation processing performed in the correction circuit unit 202 will be described with reference to FIG.

  FIG. 5A shows an in-cylinder pressure output waveform output from the amplifier circuit unit 201. However, for convenience, FIG. 5A shows an output waveform when there is no drift. As shown here, the signal level (output voltage) of the output signal S1 output from the amplification circuit unit 201 is a change in the in-cylinder pressure in the combustion chamber 2a, that is, the combustion cycle (combustion, exhaust, intake, compression) of the engine 1. It changes according to. The output signal S1 of the amplifier circuit unit 201 is output to the outside of the in-cylinder pressure detection device 12 through the connection line 133 and is input to the peak hold circuit unit 205 and the comparison circuit unit 207 (the operational amplifier OP1 and the comparator CMP), respectively. Is done.

  In the peak hold circuit unit 205 to which the output signal S1 of the amplifier circuit unit 201 is input, the charge corresponding to the peak value of the signal level of the output signal S1 is stored in the capacitor C1, and the charge is predetermined by the resistor R1. Discharge in time. FIG. 5B shows a peak hold output waveform output from the peak hold circuit unit 205. As shown here, the signal level of the output signal S2 of the peak hold circuit unit 205 increases as the signal level of the output signal S1 of the amplifier circuit unit 201 increases, and then the signal level of the output signal S1 decreases. Then, it will descend with a certain slope. Note that any value can be set as the capacitance of the capacitor C1, the resistance value of the resistor R1, and the time constant (discharge time) determined by these, but at least from the peak of the output signal S1 of the amplifier circuit unit 201, It is preferable to set a value at which all the charges of the capacitor C1 are surely discharged until the peak.

  The output signal S2 of the peak hold circuit unit 205 is input to the voltage dividing circuit unit 206. FIG. 5C shows a divided voltage output waveform output from the voltage dividing circuit unit 206. As shown here, the output signal S2 of the peak hold circuit unit 205 is divided by the voltage dividing circuit unit 206 at a predetermined voltage dividing ratio determined by the resistance values of the resistors R3 and R4, so that the original signal level can be obtained. Is also converted to a signal level lower by a certain ratio and output as an output signal S3. Note that any value can be set as the resistance values of the resistors R3 and R4 and the voltage dividing ratio determined by them, but the timing at which the magnitude determination result by the comparator CMP described later is switched is a desired value in the combustion cycle of the engine 1. It is preferable to set a value that can be detected as the timing.

  The output signal S3 of the voltage dividing circuit unit 206 is input to the non-inverting input terminal of the comparator CMP. The comparator CMP compares the level of the signal level between the output signal S3 of the voltage dividing circuit unit 206 and the output signal S1 of the amplifier circuit unit 201 input to the inverting input terminal.

  FIG. 5D shows a comparator output waveform output from the comparator CMP. As shown here, the output signal S4 output from the comparator CMP is a rectangular wave signal whose signal level is switched according to the magnitude comparison result. More specifically, when the signal level of the output signal S3 of the voltage dividing circuit unit 206 is equal to or higher than the signal level of the output signal S1 of the amplifier circuit unit 201, the output level is high, and the signal level of the output signal S3 is the output signal S1. When the signal level is lower than the output level, a low level output is obtained. Accordingly, in the present embodiment, the timing immediately after combustion of the engine 1 (immediately after detection of the peak value) appears as the rising edge of the rectangular wave of the output signal S4, and the timing during the intake air appears as the falling edge of the rectangular wave.

  Then, based on the output signal S4 output from the comparator CMP, the calculation unit 208 calculates the reset timing.

  Here, the reset timing calculation process executed by the calculation unit 208 will be described in more detail.

  The arithmetic unit 208 constantly detects the rising edge of the rectangular wave of the output signal S4 output from the comparator CMP. Then, the calculation unit 208 calculates the rectangular wave period Δt, that is, the combustion cycle period of the engine 1 from the difference t2−t1 between the rising timings t1 and t2 of two continuous rectangular waves. The reset timing Rt is calculated based on a simple arithmetic expression.

Rt = nΔt + t2
= N (t2-t1) + t2 (1)
That is, the reset timing Rt is the timing at which the time nΔt calculated by multiplying the rectangular wave period Δt by the predetermined coefficient n from the rising timing t2 of the second rectangular wave. Here, the coefficient n is a coefficient arbitrarily set in the range of 0 <n <1. The reset timing Rt is less affected by combustion and compression and is preferably a timing at which the in-cylinder pressure is close to atmospheric pressure. Therefore, in this embodiment, in the intake process immediately before switching to the compression process in one combustion cycle of the engine 1. Thus, the coefficient n is set to 0.5 so that the reset process is performed.

  Then, the reset signal output unit 209 outputs the reset signal S5 at the reset timing Rt calculated by the calculation unit 208, as shown in FIG. Upon receiving the reset signal S5, the reset circuit unit 210, for example, turns on the switch element to discharge the charge of the capacitor connected in parallel to the amplifier of the amplifier circuit unit 201, thereby eliminating the potential difference between the input and output of the amplifier. Perform reset processing.

  Thereafter, the calculation unit 208 shifts the value of the rising timing t2 of the second rectangular wave to the value of the rising timing t1 of the first rectangular wave. When the rising of a new rectangular wave is detected, the value of the rising timing t3 of the rectangular wave is set as the rising timing t2 of the second rectangular wave, and the same processing as described above is repeatedly executed. Therefore, thereafter, reset is executed for each combustion cycle of the engine 1.

  As described in detail above, in this embodiment, the in-cylinder pressure output waveform output from the amplifier circuit unit 201 is shaped through the peak hold circuit unit 205, the voltage divider circuit unit 206, and the comparison circuit unit 207, It is detected as a rectangular wave signal. Thereby, the timing immediately after combustion of the engine 1 (immediately after detection of the peak value) can be detected as the rising edge of the rectangular wave. That is, information necessary for calculating the reset timing Rt, such as the combustion cycle period and the base point timing, can be obtained based on the rising timing t1 of the rectangular wave. As a result, the reset timing Rt can be calculated without using the information of the crank angle sensor 15, and the offset drift of the amplification circuit unit 201 can be eliminated at the desired timing of the combustion cycle. As a result, since it is not necessary to separately provide a terminal for signal input from the crank angle sensor 15, an increase in the size of the in-cylinder pressure detection device 12 (correction circuit unit 202) can be suppressed. Further, in this embodiment, output correction is performed by resetting the output voltage of the amplifier circuit unit 201 to a reference value without grasping the temperature, so there is no need to provide a separate temperature sensor. As a result, the in-cylinder pressure of the engine 1 can be detected with high accuracy without complicating the configuration and the correction process.

  In addition, when it is set as the structure which acquires information required in calculating reset timing Rt by detecting whether the signal level of the amplifier circuit part 201 exceeded the preset threshold value, when drift amount is large, etc. For example, there is a concern that unless the signal is forcibly reset, it cannot be detected that the signal level of the amplifier circuit unit 201 exceeds the threshold value, and appropriate information cannot be obtained. On the other hand, when the peak value of the in-cylinder pressure output waveform of the amplification circuit unit 201 is detected as in the present embodiment, the above information can be obtained more reliably even when the drift amount is large.

  Furthermore, in the present embodiment, as a variable for obtaining the reset timing Rt that matches the desired timing of one combustion cycle of the engine 1, the period of the output signal S4 of the comparator CMP corresponding to the combustion cycle of the engine 1 (rectangular wave period) By adopting a measurement value (variable) having a relatively long measurement time, such as Δt), the ratio of the measurement error to the measurement value (variable) can be reduced. As a result, the measurement error of the measurement value (variable) hardly affects the calculation error of the reset timing Rt, the deviation between the actual reset timing and the desired timing can be suppressed relatively small, and the amplifier circuit at a better timing The output of the unit 201 can be corrected.

  In addition, it is not limited to the description content of embodiment mentioned above, For example, you may implement as follows.

  (A) In the above embodiment, the in-cylinder pressure detecting device 12 in which the in-cylinder pressure sensor including the piezoresistive element 138 and the reset correction device including the correction circuit unit 202 and the like are integrated is illustrated. However, the configuration is not limited thereto, and the reset correction device may be provided separately from the in-cylinder pressure sensor. For example, the cylinder pressure sensor reset correction device may be provided in the electronic control unit (ECU) 18. The in-cylinder pressure detecting device 12 may be provided separately from the glow plug 10. Of course, only the reset timing generation device portion including the peak hold circuit unit 205 and the like may be provided separately from the in-cylinder pressure sensor and the in-cylinder pressure detection device 12.

  (B) In the above-described embodiment, the piezoresistive element 138 is employed as the pressure-sensitive means for detecting the in-cylinder pressure of the engine 1, but the present invention is not limited to this, and offset drift such as a piezoelectric element or a metal resistance strain gauge occurs. Even in a configuration employing other pressure-sensitive means, the present invention has the same effects as the above-described embodiment.

  (C) In the above embodiment, the rectangular wave period Δt is obtained from the rising timings t1 and t2 of two continuous rectangular waves of the output signal S4 output from the comparator CMP. The method for obtaining the rectangular wave period Δt is not limited to this. For example, the rectangular wave period Δt may be obtained from the falling timing of two rectangular waves. However, since the falling timing of the rectangular wave of the output signal S4 of the comparator CMP is farther from the detection time of the peak value than the rising timing, the variation is large due to the difference in the rotational speed of the engine 1 and the like. Therefore, the detection error can be suppressed to a smaller extent when the rising timing of the rectangular wave is used as a base point for period measurement or reset timing calculation as in the above embodiment. As a result, the detection error hardly affects the calculation error of the reset timing Rt, the deviation between the actual reset timing and the desired timing can be suppressed relatively small, and the sensor output can be corrected at a better timing. Can do.

  (D) In the above embodiment, the output signal S3 of the voltage divider circuit unit 206 is input to the non-inverting input terminal of the comparator CMP, and the output signal S1 of the amplifier circuit unit 201 is input to the inverting input terminal. However, the terminal to which each signal is input may be reversed. In this case, when the signal level of the output signal S3 of the voltage divider circuit unit 206 is equal to or higher than the signal level of the output signal S1 of the amplifier circuit unit 201, the output level is low, and the signal level of the output signal S3 is the level of the output signal S1. When it is lower than the signal level, it becomes a high level output. Therefore, the timing immediately after the combustion of the engine 1 (immediately after the detection of the peak value) appears as the falling edge of the rectangular wave of the output signal S4.

  (E) The calculation formula for calculating the reset timing Rt is not limited to the calculation formula (1). For example, if more accuracy is required, the number of calculation terms may be increased. Further, the reset timing Rt may not be adjusted to the intake process as in the above embodiment, but may be set to the timing at which the in-cylinder pressure is close to the atmospheric pressure at the end of the exhaust process or the start of the compression process. Therefore, the coefficient n can be arbitrarily set according to a desired timing in one combustion cycle of the engine 1. Also, the time point that becomes the base point for obtaining the reset timing Rt may be the time point when the previous reset is executed, that is, the previous reset timing Rt, instead of the rising timing t2 of the rectangular wave.

  (F) The comparator CMP may be provided with a positive feedback so that the comparison circuit unit 207 has hysteresis characteristics. With such a configuration, a stable output can be obtained even when noise is included in the input signal.

  (G) The peak hold circuit unit 205 may have a circuit configuration that can vary the discharge time. The in-cylinder pressure output waveform output from the amplifying circuit unit 201 varies in various ways depending on the rotational speed of the engine 1, but with the above configuration, a substantially constant peak hold output waveform can always be obtained. For example, it is possible to respond in real time according to a change in the number of revolutions by performing a control to increase the discharge time at high rotation speed and to delay the discharge time at low rotation speed. Therefore, a stable output signal S4 of the comparator CMP can be obtained regardless of a change in the rotational speed of the engine 1, and the rising timing of the rectangular wave can be detected with high accuracy. As a result, the difference between the actual reset timing and the desired timing can be kept relatively small, and the output correction of the amplifier circuit unit 201 can be performed at a better timing.

It is a fragmentary sectional view of the cylinder head to which the glow plug was attached. It is the schematic which shows the structure of an engine control system. It is a functional block diagram which shows the circuit structure of a cylinder pressure detection apparatus. It is a circuit diagram of a peak hold circuit part, a voltage dividing circuit part, and a comparison circuit part. (A) is a diagram showing an in-cylinder pressure output waveform, (b) is a diagram showing a peak hold output waveform, (c) is a diagram showing a partial pressure output waveform, and (d) is a comparator. It is the figure which showed the output waveform, (e) is the figure which showed the waveform of the reset signal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 10 ... Glow plug, 12 ... In-cylinder pressure detection apparatus, 138 ... Piezoresistive element, 201 ... Amplification circuit part, 202 ... Correction circuit part, 205 ... Peak hold circuit part, 206 ... Voltage division circuit part, 207 ... Comparison circuit unit 208... Arithmetic unit 209 reset signal output unit 210 reset circuit unit

Claims (4)

A reset timing generation device for generating a timing for resetting an output voltage of an in-cylinder pressure sensor output in accordance with a cylinder pressure of an internal combustion engine or a change rate of the cylinder pressure of the internal combustion engine to a reference value,
Peak hold means for holding the peak value of the output voltage of the in-cylinder pressure sensor;
Voltage dividing means for dividing the output voltage of the peak hold means;
Comparing means for comparing the output voltage of the voltage dividing means and the output voltage of the in-cylinder pressure sensor, and outputting a rectangular wave signal whose output voltage level is switched according to the comparison result;
A reset timing generation device comprising: reset timing calculation means for calculating reset timing based on an output signal of the comparison means.   The reset timing generation apparatus according to claim 1, wherein the reset timing calculation unit measures a period of a rectangular wave signal output from the comparison unit and calculates a reset timing based on the period.   The time interval from the rising or falling point of a predetermined rectangular wave signal where the output voltage of the voltage dividing means is equal to or higher than the output voltage of the in-cylinder pressure sensor to the rising or falling point of the next rectangular wave signal is reset. The reset timing generation apparatus according to claim 2, wherein the timing calculation unit measures the period of the rectangular wave signal. An in-cylinder pressure sensor that outputs an electric signal in accordance with the in-cylinder pressure of the internal combustion engine or the change rate of the in-cylinder pressure of the internal combustion engine;
The reset timing generation device according to any one of claims 1 to 3,
Reset signal output means for outputting a reset signal at the timing generated by the reset timing generator;
An in-cylinder pressure detecting device comprising: reset means for resetting an output voltage of the in-cylinder pressure sensor to a reference value based on an input of a reset signal from the reset signal output means.

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