JP5351425B2 - Output correction device for in-cylinder pressure sensor and in-cylinder pressure detection device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an output correction device which can correct the offset drift of a cylinder pressure sensor and a cylinder pressure detecting device which uses it and can detect the cylinder pressure of an internal combustion engine with high precision. <P>SOLUTION: The cylinder pressure detecting device 12 includes a detection section 203 for detecting a change in the resistance of a piezoelectric element 138 as an electric signal and a correction circuit section 204 for correcting it and outputting it to the outside. The correction circuit section 204 includes a signal correction section 211 for correcting an electric signal output from the detection section 203, an output circuit section 212 for amplifying an electric signal output from the signal correction section 211 and outputting it to the outside, and a reset control section 213 for resetting the output value of the signal correction section 211 to be a standard value. The correction circuit section 204 is further provided with an internal reset function in which the reset control section 213 resets with reset timing calculated on the basis of the output signal of the detection section 203 and an external reset function in which the reset control section 213 resets on the basis of an external reset command signal. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an output correction device for 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 same.

  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 drift, for example, a technique for correcting from the value of a separately installed temperature sensor based on the temperature characteristics of the in-cylinder pressure sensor is disclosed (see, for example, Patent Document 1).
JP 2004-257888 A

  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.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an output correction device that can correct an offset drift of an in-cylinder pressure sensor, and an in-cylinder pressure detection device that can accurately detect the in-cylinder pressure of an internal combustion engine. Is to provide.

  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 output correction device of this configuration is
An output correction device for an in-cylinder pressure sensor that outputs an electrical signal in accordance with the in-cylinder pressure of the internal combustion engine or the rate of change of the in-cylinder pressure of the internal combustion engine,
An internal reset means for calculating a reset timing based on an output signal of the in-cylinder pressure sensor and resetting an output value of the in-cylinder pressure sensor to a reference value at the reset timing;
An external reset means for detecting an external reset command signal and resetting the output value of the in-cylinder pressure sensor to a reference value based on the reset command signal ;
An output terminal electrically connected to a predetermined external device;
Current determination means for determining the direction of current at the output terminal;
Command signal detecting means for detecting the reset command signal based on a determination result by the current determining means is provided.

  According to the configuration 1, by providing the means for resetting the output value of the in-cylinder pressure sensor to the reference value, it is possible to eliminate the offset drift of the sensor output without depending on the temperature information.

  Among the reset means, the internal reset means predicts a desired timing of the combustion cycle of the internal combustion engine as a reset timing based on, for example, the output signal of the in-cylinder pressure sensor, and executes the reset process at the timing. To do.

  However, when obtaining the reset timing from the output signal of the in-cylinder pressure sensor, it may be difficult to calculate the optimal reset timing in the process in which the rotational speed of the internal combustion engine is changing (acceleration / deceleration). For this reason, there is a concern that a correction error occurs only with the internal reset means.

  In this regard, the present configuration 1 includes not only internal reset means but also external reset means for executing reset processing based on an external reset command signal. Therefore, the reset process can be executed at a desired timing in accordance with the combustion cycle of the internal combustion engine without being affected by the change in the rotational speed of the internal combustion engine. For example, if the reset process is executed based on information of a crank angle sensor provided in the internal combustion engine, the reset process can be executed at a timing corresponding to a predetermined crank angle.

  Conversely, a correction error can occur even when only the external reset means is used. Usually, an external reset command signal is given from an electronic control unit (hereinafter referred to as “ECU”) that controls the internal combustion engine. The ECU outputs a reset command signal only when the sensor output is determined to be abnormal based on its own determination criteria. That is, the reset process may not be performed unless the ECU determines that there is an abnormality. Therefore, there may be a case where the reset command signal is not output at all until the level of the in-cylinder pressure sensor actually has an offset drift until it becomes large. If the ECU outputs the reset command signal and resets every combustion cycle of the internal combustion engine, the detection accuracy can be increased, but the burden on the ECU increases remarkably. On the other hand, according to the present configuration 1, since the internal reset means is provided, the reset process can be periodically performed at a relatively short interval even when there is no reset command signal from the outside.

  As a result, by providing the both reset means, the in-cylinder pressure of the internal combustion engine can always be detected with better accuracy.

In general, the output correction device for the in-cylinder pressure sensor includes an output terminal for outputting a detection signal of the in-cylinder pressure sensor to an external device such as an ECU for controlling the internal combustion engine.

  On the other hand, when an external reset command signal such as an ECU is input to the output correction device, it is conceivable to provide a signal input terminal separately on the output correction device side. There is a concern that the manufacturing cost will increase.

On the other hand, according to the above configuration 1 , since the presence or absence of the reset command signal can be detected by determining the direction of the current at the existing output terminal, it is not necessary to separately provide a terminal for signal input and the like. An increase in the size of the apparatus can be suppressed. In particular, when an in-cylinder pressure detection device in which an in-cylinder pressure sensor and an output correction device 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.

Configuration 2 . Output correction device of this configuration, Oite the above configuration 1,
The apparatus further comprises delay means for delaying a time from detection of the reset command signal to execution of the reset by a predetermined time.

  Since the output signal of the in-cylinder pressure sensor is taken into the output correction device and the signal is actually reset, a predetermined time is required since various processing steps such as signal conversion are performed. Therefore, the signal that is reset at the predetermined time point t1 is actually a signal output at the time point t2 before the time point t1. Therefore, when reset processing is performed based on an external reset command signal, even if the reset command signal is sent in real time at an appropriate timing, for example, corresponding to a crank angle of 10 °, it is actually Prior to this timing, for example, a signal output at a time when the crank angle is 0 ° is reset. That is, there is a possibility that a difference occurs between the timing at which the reset process is actually performed and the desired reset timing at which the reset process is to be performed. In particular, when processing such as digital conversion of the output signal of the in-cylinder pressure sensor is involved, the delay time becomes large, and such a problem may appear remarkably.

On the other hand, if the delay means is provided as in the present configuration 2 and the difference between the timing at which the reset command signal is detected and the desired reset timing at which the reset processing is to be performed is adjusted, the above-described problem can be alleviated. Can do. For example, the delay means delays reset execution by the time required until the output signal of the in-cylinder pressure sensor is taken and the signal is reset.

Configuration 3 . The output correction apparatus of this configuration is the above configuration 1 or 2 ,
A mode switching means capable of switching between an internal reset mode for performing only reset by the internal reset means, an external reset mode for performing only reset by the external reset means, and a dual reset mode for performing reset by the both reset means. It is characterized by that.

According to the configuration 3, since it is possible to meet various needs of the internal combustion engine by switching to various modes, the convenience is increased and the versatility of the output correction device is also increased. For example, if you want to reduce the burden on the ECU, use the internal reset mode, use the external reset mode if you want to leave it to the ECU, and if you want to perform an external reset only when an abnormality occurs, usually based on an internal reset Can be switched to use both reset modes.

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 output correction apparatus according to any one of the above configurations 1 to 3 is provided.

According to the configuration 4 , by integrating the in-cylinder pressure sensor and the output correction device, 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 cylinder 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, 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 when the screw is fixed. The 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. Thus, when the temperature of the heater member 102 is raised, the current supplied to the heating element 121 through the middle shaft 101 flows to the cylinder head 2b through the metal shell 100.

  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 connection lines 133 a, 133 b, 133 c 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 board 140, electronic components such as an IC and a memory 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 unit detects a change in resistance of the piezoresistive element 138 as an electric signal. The detected electrical signal is amplified 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 for eliminating the drift is performed by resetting the output value of the detection unit to the reference value as described later, this process is hereinafter referred to as “reset (reset process)”.

  Note that the connection line 133 a among the plurality of connection lines 133 a to 133 c 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 133b and 133c are electrically connected to the printed circuit board 140, and are used for outputting a detection signal (connection line 133b) and for supplying power to the printed circuit board 140 (connection line 133c).

  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 detecting device 12 includes the piezoresistive element 138 as a pressure detecting element, a temperature detecting element 201 that outputs an electric characteristic that changes depending on temperature as an electric signal, and an element control unit that controls both the elements 138 and 201. 202, a detection unit 203 that detects a resistance change of the piezoresistive element 138 as an electrical signal, and a correction circuit unit 204 that corrects the electrical signal detected by the detection unit 203 and outputs the corrected electrical signal to the outside. Among these, the piezoresistive element 138 and the detection unit 203 constitute an in-cylinder pressure sensor in the present embodiment, and the correction circuit unit 204 constitutes an output correction device.

  The correction circuit unit 204 includes a signal correction unit 211 that corrects the electric signal output from the detection unit 203, an output circuit unit 212 that amplifies the electric signal output from the signal correction unit 211 and outputs the amplified signal to the outside. A reset control unit 213 that resets the output value of the signal correction unit 211 to a reference value.

  In the present embodiment, the reset control unit 213 performs a reset function at the reset timing calculated based on the output signal of the detection unit 203, and the reset control unit 213 performs the reset based on the reset command signal from the ECU 18. Has a reset function.

  More specifically, the correction circuit unit 204 includes an internal reset timing detection unit 214 that calculates a reset timing based on an output signal output from the output circuit unit 212. The internal reset timing detection unit 214 outputs a reset signal to the reset control unit 213 at the calculated reset timing. Therefore, the reset control unit 213 and the reset timing detection unit 214 constitute an internal reset unit in the present embodiment.

  The correction circuit unit 204 includes an external reset timing detection unit 215 that detects a reset timing based on a reset command signal from the ECU 18. The external reset timing detection unit 215 is electrically connected to the output circuit unit 212 and has a function of determining the direction of current at the output terminal 212a of the output circuit unit 212. As will be described in detail later, with this function, the external reset timing detector 215 detects the presence or absence of a reset command signal from the ECU 18. If detected, a reset signal is output to the reset control unit 213 and the internal reset timing detection unit 214 via the delay circuit unit 216 as delay means at the timing. Therefore, the external reset timing detection unit 215 constitutes a current determination unit and a command signal detection unit in the present embodiment, and the external reset timing detection unit 215 and the reset control unit 213 constitute an external reset unit.

  The correction circuit unit 204 includes a mode switching unit 217 as mode switching means for properly using the internal reset function and the external reset function described above. In the present embodiment, the mode is switched between an internal reset mode in which only the internal reset function is enabled, an external reset mode in which only the external reset function is enabled, and a dual reset mode in which both reset functions are enabled.

  Next, the flow of correction processing performed in the correction circuit unit 204 will be described. 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 piezoresistive element 138 is deformed and the resistance value changes. This resistance change is converted into a voltage change by electrically controlling the piezoresistive element 138 by the element control unit 202. Then, the voltage change is detected by the detection unit 203 and output to the signal correction unit 211 as an electrical signal.

  On the other hand, the temperature detection element 201 outputs an electrical characteristic that varies depending on the temperature to the signal correction unit 211 as an electrical signal.

  In the signal correction unit 211, various corrections are performed on the electrical signal output from the detection unit 203. For example, span correction for adjusting the amplification factor of the electric signal according to the output value of the temperature detection element 201, offset correction for adjusting the offset voltage, and the like are performed.

  The electric signal corrected by the signal correction unit 211 is amplified or the like via the output circuit unit 212 and is externally output from the in-cylinder pressure detection device 12 as a detection signal of the in-cylinder pressure.

  Next, the flow of processing performed in each reset mode will be described in detail. Note that the reset mode is switched by setting in advance in the memory or the like provided on the printed circuit board 140. Then, the mode switching unit 217 performs connection switching control corresponding to each reset mode based on the mode information set in the memory or the like.

  When the internal reset mode is set, the corrected electric signal is input from the output circuit unit 212 to the internal reset timing detection unit 214 by the connection switching control of the mode switching unit 217. The internal reset timing detection unit 214 that receives this signal calculates the reset timing from the signal. For example, the waveform period is measured based on the output waveform (in-cylinder pressure waveform) output from the output circuit unit 212, and the reset timing is calculated by substituting the waveform period into a predetermined arithmetic expression.

  The internal reset timing detection unit 214 temporarily stores the reset timing calculated as described above in a memory or the like, and outputs a reset signal to the reset control unit 213 at the reset timing by timer management.

  Upon receiving this, the reset control unit 213 turns on the switching element, for example, and discharges the capacitor connected in parallel to the amplifier of the signal correction unit 211, thereby eliminating the potential difference between the input and output of the amplifier. Process. By the reset process, the output value of the signal correction unit 211 becomes the reference value, and drift is eliminated.

  In the internal reset mode, the reset process is executed every time one combustion cycle of the engine 1 along the above flow unless an abnormality or the like occurs.

  On the other hand, when the external reset mode is set, a reset process is performed based on a reset command signal from the ECU 18.

  First, a configuration in which the external reset timing detection unit 215 detects a reset command signal from the ECU 18 will be described with reference to FIG. FIG. 4 is an equivalent circuit diagram showing an electrical connection configuration between the correction circuit unit 204 and the ECU 18.

  The ECU 18 includes a power supply circuit unit (not shown) that outputs a constant voltage (for example, +5 [V]), and the power supply circuit unit corrects the power supply line 301 including the power supply connection line 133c and the like. The circuit unit 204 is electrically connected.

  The correction circuit unit 204 is grounded to the ground via the metal shell 100 and the like by attaching the glow plug 10 to the cylinder head 2b that is electrically grounded.

  An output terminal 212a of the correction circuit unit 204 (output circuit unit 212) is electrically connected to the ECU 18 via an output line 302 including the detection signal output connection line 133b and the like.

  Further, the ECU 18 has a circuit including resistors R1 and R2, a switching element 303, and the like in relation to the correction circuit unit 204.

  The resistor R1 has one end connected to the power supply line 301 and the other end connected to the output line 302.

  The switching element 303 is an npn transistor, and its collector is connected to the output line 302. A resistor R2 is connected in series to the emitter of the switching element 303. The other end of the resistor R2 is grounded.

  The switching element 303 has a base connected to a command signal output unit (not shown) of the ECU 18 and operates based on an input of a reset command signal from the command signal output unit. The switching operation of the switching element 303 energizes / cuts off the resistor R2. For example, the command signal output unit of the ECU 18 outputs a reset command signal at a timing corresponding to a predetermined crank angle based on the detection signal from the crank angle sensor 15.

  In the present embodiment, the resistors R1, R2 (R1> R2) are set so that the reference voltage of the detection signal output from the output terminal 212a of the correction circuit unit 204 is maintained constant (for example, +2 [V]). Has been.

  With the above configuration, during normal operation (switch-off state) when the power supply to the resistor R2 is interrupted, a current flows from the output terminal 212a to the correction circuit unit 204 (output circuit unit 212) via the resistor R1. Flows in.

  On the other hand, when the switching element 303 is activated based on the reset command signal from the command signal output unit of the ECU 18 (switch-on state), from the output terminal 212a via the resistor R2 to maintain a constant voltage, Current flows out to the ECU 18 side. That is, the direction of the current at the output terminal 212 a of the output circuit unit 212 is reversed by the switching operation of the switching element 303.

  When the external reset timing detection unit 215 detects the reversal of the current direction and determines that there is a reset command signal from the ECU 18, the reset signal is detected at the timing by the reset control unit 213 and the internal reset timing detection. Is output to the unit 214.

  The reset signal reaches the reset control unit 213 or the like with a delay of a preset time through the delay circuit unit 216. In this embodiment, it is set to be delayed by a time (for example, 100 μsec) equivalent to the delay time required for various signal processing such as A / D conversion performed in the detection unit 203, the signal correction unit 211, and the like. As a result, the timing at which the command output when the ECU 18 detects the desired crank angle (for example, crank angle 0 °) from the crank angle sensor 15 reaches the reset control unit 213 and the desired crank angle (for example, crank angle 0). It is possible to match the timing at which the detection value of the detection unit 203 reaches the reset processing step.

  The internal reset timing detection unit 214 that has received the reset signal discards the data of the reset timing calculated by itself, which is stored in the memory or the like. This is a function provided in consideration of giving priority to the external reset function in both reset modes. Without this function, in both reset modes, despite the reset process being performed at a more appropriate timing corresponding to a predetermined crank angle, an extra reset process is performed at the next internal reset timing, There is a possibility that a correction error occurs.

  In addition, the reset control unit 213 that has received the reset signal performs a reset process as in the case of the internal reset mode. By the reset process, the output value of the signal correction unit 211 becomes the reference value, and drift is eliminated.

  As described above, in the external reset mode, the reset process is appropriately executed based on the command from the ECU 18. However, the ECU 18 outputs a reset command signal only when it is determined that the output waveform of the in-cylinder pressure is abnormal based on its own determination criteria.

  When both reset modes are set, the processes performed in the internal reset mode and the external reset mode are executed in parallel.

  Under the above configuration, for example, the internal reset mode is used to reduce the burden on the ECU 18, and the external reset mode is used to leave it to the ECU 18. Normally, the external reset is based only on the internal reset and only when an abnormality occurs. When it is desired to perform the above, mode switching such as using both reset modes can be performed.

  As described above in detail, in the present embodiment, by resetting the output value of the signal correction unit 211 to the reference value, offset drift of the output value can be eliminated without relying on temperature information.

  In particular, the reset process can be executed at a desired timing according to the combustion cycle of the engine 1 without being affected by a change in the rotational speed of the engine 1 by the external reset function. Further, due to the internal reset function, even when there is no reset command signal from the ECU 18, the reset process can be performed periodically at relatively short intervals. As a result, by providing the both reset functions, the in-cylinder pressure of the engine 1 can always be detected with better accuracy without increasing the burden on the ECU 18.

  In the present embodiment, since the presence / absence of a reset command signal from the ECU 18 can be detected by determining the direction of the current at the output terminal 212a of the correction circuit unit 204, a terminal for inputting a signal from the ECU 18 and the like are additionally provided. There is no need to suppress the increase in the size of the in-cylinder pressure detecting device 12 (correction circuit unit 204), an increase in manufacturing cost, and the like.

  Furthermore, in this embodiment, the mode can be switched between an internal reset mode in which only the internal reset function is enabled, an external reset mode in which only the external reset function is enabled, and a dual reset mode in which both reset functions are enabled. It has become. For this reason, various types of ECUs 18 can be handled, convenience is increased, and versatility of the in-cylinder pressure detection device 12 (correction circuit unit 204) is also increased.

  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-described embodiment, the in-cylinder pressure detection device 12 in which the in-cylinder pressure sensor including the piezoresistive element 138 and the like and the output correction device including the correction circuit unit 204 and the like are integrated is illustrated. Not limited to this, the output correction device may be provided separately from the in-cylinder pressure sensor. For example, the output correction device for the in-cylinder pressure sensor 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.

  (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 internal reset timing detection unit 214 calculates the reset timing based on the waveform period of the output waveform of the output circuit unit 212. The reset timing calculation method by the internal reset timing detection unit 214 is not limited to this, and any other method may be used as long as the reset timing is calculated based on the output signal of the detection unit 203.

  (D) The configuration related to the detection of the reset command signal of the ECU 18 is not limited to the above embodiment.

  For example, when there is no reset command signal of the ECU 18, current flows out to the ECU 18 side at the output terminal 212a of the output circuit unit 212, and when the reset command signal is issued, current flows into the output circuit unit 212 side. A circuit configuration in which the direction of current is reversed may be employed. Moreover, it is good also as a structure which incorporated the circuit which consists of said resistance R1, R2, the switching element 303, etc. in the circuit structure of an engine control system outside ECU18. Other circuit configurations may be used as long as the direction of the current in the output terminal 212a of the output circuit unit 212 is reversed depending on at least the presence or absence of a reset command signal from the ECU 18.

  Of course, a configuration may be adopted in which an input terminal is separately provided for the reset command signal from the ECU 18 and the reset command signal is directly detected.

  (E) The above embodiment has a mode switching function for properly using the internal reset function and the external reset function. However, the present invention is not limited to this. Good.

  (F) In the above embodiment, the delay circuit unit 216 that delays the time from the detection of the reset command signal to the execution of the reset process is provided for the external reset function. For example, the delay circuit unit 216 can be omitted when the delay time required for various signal processing in the detection unit 203 and the signal correction unit 211 is relatively small.

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 an equivalent circuit diagram which shows the electrical connection structure of a correction circuit part and ECU.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 10 ... Glow plug, 12 ... In-cylinder pressure detection apparatus, 15 ... Crank angle sensor, 18 ... Electronic control unit (ECU), 138 ... Piezoresistive element, 203 ... Detection part, 204 ... Correction circuit part, 211 ... Signal correction unit, 212... Output circuit unit, 212a... Output terminal, 213... Reset control unit, 214... Internal reset timing detection unit, 215... External reset timing detection unit, 216.

Claims (4)

An output correction device for an in-cylinder pressure sensor that outputs an electrical signal in accordance with the in-cylinder pressure of the internal combustion engine or the rate of change of the in-cylinder pressure of the internal combustion engine,
An internal reset means for calculating a reset timing based on an output signal of the in-cylinder pressure sensor and resetting an output value of the in-cylinder pressure sensor to a reference value at the reset timing;
An external reset means for detecting an external reset command signal and resetting the output value of the in-cylinder pressure sensor to a reference value based on the reset command signal ;
An output terminal electrically connected to a predetermined external device;
Current determination means for determining the direction of current at the output terminal;
An output correction apparatus comprising: command signal detection means for detecting the reset command signal based on a determination result by the current determination means . 2. The output correction apparatus according to claim 1, further comprising delay means for delaying a time from detection of the reset command signal to execution of the reset by a predetermined time. A mode switching means capable of switching between an internal reset mode for performing only reset by the internal reset means, an external reset mode for performing only reset by the external reset means, and a dual reset mode for performing reset by the both reset means. output correction apparatus according to claim 1 or 2, characterized in that. 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;
Cylinder pressure detecting apparatus characterized by comprising an output correction device according to any one of claims 1 to 3.

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