JP5327198B2 - Fuel injection control device and fuel injection device - Google Patents

Abstract

The device has an output characteristic adjuster e.g. offset digital to analog converter, adjusting amplification factor used by a fuel pressure sensor (S1) for converting fuel pressure into a sensor signal and an offset potential for the sensor signal. A controller e.g. microcomputer (25), transmits command information to the sensor, where the information specifies desired values of the factor and offset potential. The controller sets the factor and the offset potential to the desired values by the adjuster during reception of the information through a communication device of the sensor.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  In the control field of diesel engines mounted on vehicles, the fuel pressure is set at a predetermined position in the fuel passage from the fuel outlet of the common rail, which is a pressure accumulating container for storing high-pressure fuel pumped by the fuel pump, to the injection port of the fuel injection valve. A sensor is provided, and a signal from the fuel pressure sensor is AD-converted every predetermined time to detect a transition of the fuel pressure accompanying fuel injection into the cylinder, and an actual injection state of the fuel injection valve from the detection result (Injection characteristics) is detected, and the detection result of the injection state is fed back to fuel injection control (specifically, control of the fuel injection valve) and used (for example, Patent Document 1, Patent Document 1). 2).

  For example, the actual injection state to be detected includes the fuel injection start timing and the fuel injection amount. In the control device that controls the fuel injection valve (that is, controls the fuel injection to the internal combustion engine), the detected actual injection state Based on the state, the drive start timing and drive time of the fuel injection valve are corrected. In order to detect an injection state related to a certain cylinder, an emergency signal that traces a waveform of a signal from the fuel pressure sensor (hereinafter also referred to as a fuel pressure signal) in a period including a fuel injection period of the cylinder. AD conversion is performed at a constant sampling interval (for example, every several tens of μs).

  The fuel pressure signal is also used for basic control processing (hereinafter referred to as basic control processing) other than the processing for detecting the injection state in the fuel injection control processing. The basic control process includes, for example, a process for calculating a basic value of the driving time of the fuel injection valve (that is, a value before correction according to the injection state) and a process for controlling the fuel pump. That is, since the fuel pressure signal in the non-injection period in which the fuel is not injected into the cylinder indicates the fuel pressure before injection (pressure in the common rail) supplied from the common rail to the fuel injection valve, the control device Based on the AD conversion result of the fuel pressure signal during the non-injection period, the basic value of the drive time of the fuel injection valve is calculated, or the fuel pump is controlled so that the pressure in the common rail becomes the target value.

JP 2008-144749 JP 2009-57928 A

  Here, for the basic control process other than the process of detecting the injection state among the processes of the fuel injection control, the fuel pressure is changed to the maximum change range (for example, 0) from the minimum value to which the fuel pressure is considered to change. However, even if the detection resolution is a relatively large value (that is, a low resolution) such as several MPa, it is considered that there is no significant problem in the control.

  In order to detect the injection state, the fuel pressure may be detected in a range that varies with fuel injection and narrower than the maximum change range. In order to improve, a relatively small value (that is, high resolution) such as several tens of KPa is required.

  In order to satisfy such a requirement, the conventional fuel injection control device must always detect the fuel pressure with the resolution of a small value (high resolution) necessary for detecting the injection state within the maximum change range. It was. Specifically, when the fuel pressure changes from the minimum value to the maximum value in the maximum change range, the fuel pressure sensor changes so that the fuel pressure signal changes from the minimum value to the maximum value in the voltage range that can be AD converted by the AD converter. And the voltage detection resolution (that is, the number of bits) of the AD converter is set to a value that provides the pressure detection resolution necessary for detecting the injection state.

  However, in such a configuration, the number of bits of the AD converter increases, and the processing load of the computer (for example, the process of transferring data as an AD conversion result from the AD converter to the memory or the process of calculating the data) Load) will increase. When the processing load increases, the AD conversion interval (that is, the sampling interval) cannot be shortened. As a result, it is difficult to realize the sampling interval (for example, several tens of μs) necessary for detecting the injection state. Become.

  Accordingly, an object of the present invention is to reduce the processing load for detecting the fuel pressure in the fuel injection control device.

  According to a first aspect of the present invention, there is provided a fuel injection control device that injects fuel supplied from a pressure accumulating container that stores fuel pumped by a fuel pump into a cylinder of an internal combustion engine from an injection port, and fuel injection from a fuel outlet of the pressure accumulating container. It is provided at a predetermined position in the fuel passage to the injection port of the valve, detects the fuel pressure in the fuel passage that fluctuates with fuel injection from the injection port to the cylinder, and generates a sensor signal having a voltage corresponding to the fuel pressure. Fuel pressure detection means for outputting; and control means for performing fuel injection control processing for injecting fuel to the fuel injection valve. The control means has an AD converter that AD converts the sensor signal from the fuel pressure detection means, detects the fuel pressure from the AD conversion result by the AD converter, and determines the detected value of the fuel pressure. The fuel injection control process is performed by using this.

  Further, the fuel pressure detection means includes a communication means for communicating with the control means, a gain when the fuel pressure detection means converts the fuel pressure into a sensor signal, and a sensor that outputs the fuel pressure detection means to the control means. Output characteristic adjusting means for adjusting the offset potential of the signal. Then, command information representing each value of the gain and the offset potential is transmitted from the control means to the fuel pressure detection means, and when the fuel pressure detection means receives the command information by the communication means, the output characteristic adjustment means The gain and the offset potential are set to values represented by the received command information.

  According to such a fuel injection control device, the control means detects the fuel pressure in a wide pressure range from a predetermined minimum value to a predetermined maximum value (in other words, the fuel pressure detection target range is a wide pressure range). The fuel pressure is detected in a specific pressure range narrower than the wide pressure range (in other words, the fuel pressure detection target range is set to a narrow specific pressure range). By changing the command information transmitted to the pressure detection means, in any case, when the fuel pressure changes from the minimum value of the detection target range to the maximum value, the minimum value of the predetermined voltage range in which the sensor signal can be AD converted by the AD converter The output characteristics (that is, gain and offset potential) of the fuel pressure detecting means can be set so as to change from 1 to the maximum value.

  For this reason, when the fuel pressure is detected in a narrow pressure range, the value of the fuel pressure represented by the LSB (least significant bit) of the AD converter (that is, detection of the fuel pressure) is detected, compared with the case where the fuel pressure is detected in a wide pressure range. (Resolution value) can be reduced. As a result, the detection resolution when the fuel pressure is detected in a narrow pressure range can be increased without increasing the number of bits of the AD converter.

  Therefore, when the fuel pressure is detected in a narrow specific pressure range, it is possible to satisfy the requirement to detect with high resolution without increasing the number of bits of the AD converter. Since it is not necessary to increase the number of bits of the AD converter, it is possible to detect fuel pressure such as a process of transferring data as an AD conversion result from the AD converter to a memory and a process of calculating the data. The processing load can be reduced.

By the way, the control means can be configured specifically as described in claim 2.
That is, the control means detects the fuel pressure in a basic detection range from a predetermined basic lower limit pressure to a predetermined basic upper limit pressure, and the fuel pressure is in a detection range narrower than the basic detection range and has a basic lower limit. In some cases, detection is performed within a limited detection range from a lower limit pressure higher than the pressure to an upper limit pressure lower than the basic upper limit pressure. When the fuel pressure is detected in the basic detection range, the control means detects the sensor signal when the fuel pressure changes within the basic detection range (specifically, when the fuel pressure changes from the basic lower limit pressure to the basic upper limit pressure). Is a voltage range in which the AD converter can perform AD conversion, and a basic detection range representing each value of the gain and the offset potential that changes in a voltage range from a predetermined basic lower limit voltage to a predetermined basic upper limit voltage. Command information is transmitted to the fuel pressure detecting means. Further, when the control means detects the fuel pressure within the limited detection range, as the command information, the fuel pressure changes within the limited detection range (specifically, when the fuel pressure changes from the lower limit pressure forming the limited detection range to the upper limit pressure). The command information for the limited detection range representing each value of the gain and the offset potential at which the sensor signal changes in the voltage range from the basic lower limit voltage to the basic upper limit voltage is transmitted to the fuel pressure detecting means.

  According to this configuration, when the fuel pressure is detected in the limited detection range that is narrower than the basic detection range, the value of the fuel pressure represented by the LSB of the AD converter (in comparison with the detection in the basic detection range ( The fuel pressure detection resolution value) can be reduced. As a result, the detection resolution when the fuel pressure is detected within the limited detection range can be increased without increasing the number of bits of the AD converter. Therefore, when detecting the fuel pressure in a limited detection range narrower than the basic detection range, it is possible to satisfy the demand for detection with high resolution without increasing the number of bits of the AD converter. It is possible to reduce the load of processing for detecting fuel pressure, such as processing for transferring data as an AD conversion result from the AD converter to the memory and processing for calculating the data.

  Next, in the fuel injection control device according to claim 3, in the fuel injection control device according to claim 2, the control means before the specific period including the fuel injection period of the cylinder corresponding to the fuel pressure detection means arrives. The change range of the fuel pressure in the specific period is predicted. Then, the control means transmits the command information for the limited detection range using the predicted change range (hereinafter also referred to as the predicted change range) to the fuel pressure detection means, during the specific period. The fuel pressure is detected within the predicted change range. The command information for the limited detection range with the predicted change range as the limited detection range means that the sensor signal is a voltage range from the basic lower limit voltage to the basic upper limit voltage when the fuel pressure changes in the predicted change range. This is command information representing each value of the gain and the offset potential that will change.

  According to this configuration, the fuel pressure in a specific period including the fuel injection period can be detected with higher resolution than other periods, and this effect can be achieved without increasing the number of bits of the AD converter. Can also be obtained. Accordingly, it is possible to accurately detect the actual injection state of the fuel injection valve from the fuel pressure in a specific period including the fuel injection period with a small processing load.

  Next, in the fuel injection control device according to claim 4, in the fuel injection control device according to claim 3, when the specific period ends, the control means transmits the command information for the basic detection range to the fuel pressure detection means. By doing so, the fuel pressure is detected in the basic detection range.

And according to this structure, the fuel pressure in periods other than the specific period can be detected in a wide basic detection range.
Next, in a fuel injection control device according to a fifth aspect, in the fuel injection control device according to the third and fourth aspects, the control means is configured to control the specific pressure based on the fuel pressure detected before the specific period arrives. Predict the range of change in fuel pressure over time.

According to this configuration, the change range of the fuel pressure can be predicted more correctly.
The fuel pressure value used for predicting the change range (the fuel pressure value before the specific period arrives) may be detected from the sensor signal output by the fuel pressure detecting means. If the fuel pressure detecting means is provided for each of them, the fuel pressure value detected from the sensor signal corresponding to the other cylinders that are not performing fuel injection may be used. Further, a fuel pressure value detected by a pressure sensor provided in the pressure accumulation chamber may be used. On the other hand, in any case, a value obtained by averaging a plurality of detection values (an average value or a so-called annealing value) may be used.

  On the other hand, a fuel injection device according to a sixth aspect of the present invention includes a fuel injection valve that injects fuel supplied from a pressure accumulating container that stores fuel pumped by a fuel pump from an injection port to a cylinder of an internal combustion engine, and fuel from a fuel outlet of the pressure accumulating container A sensor signal of a voltage corresponding to the fuel pressure is provided at a predetermined position in the fuel passage to the injection port of the injection valve, and detects the fuel pressure in the fuel passage that varies with fuel injection from the injection port to the cylinder. And a fuel pressure detecting means for outputting.

  The fuel pressure detection means includes a communication means for communicating with a control device for controlling the fuel injection valve, a gain when the fuel pressure detection means converts fuel pressure into a sensor signal, and the fuel pressure detection means. Output characteristic adjusting means for adjusting the offset potential of the sensor signal to be output. Further, the fuel pressure detecting means receives a command signal transmitted from the control device and representing each value of the gain and the offset potential by the communication means. The offset potential is set to a value represented by the received command information.

According to such a fuel injection device, it is possible to constitute the fuel injection control device according to each of the above-described claims, and to obtain the above-described effects.
Further, in the fuel injection device according to claim 6, the fuel pressure detecting means can be provided in the fuel injection valve. That is, the fuel injection valve and the fuel pressure detection means can be integrated into one module. And according to such a fuel-injection apparatus, handling becomes easy.

It is a block diagram showing the fuel-injection control system of embodiment. It is a block diagram showing the connection state of an injector and ECU. It is a block diagram showing the fuel pressure sensor and control IC which are provided in the injector. It is explanatory drawing explaining the relationship between a sensor output voltage (voltage value of a fuel pressure signal) and fuel pressure. It is a flowchart showing the pressure detection range switching process which the microcomputer of ECU performs. It is a flowchart showing the detection range command process performed in FIG. It is a flowchart showing the limited detection range calculation process performed in FIG. It is a flowchart showing the output adjustment process performed by the controller in the control IC of each injector, and the adjustment value calculation process performed during the output adjustment process. It is a flowchart showing the AD conversion process which the microcomputer of ECU performs.

  The fuel injection control system of the embodiment to which the present invention is applied will be described below. In addition, the fuel injection control system of this embodiment controls the fuel injection to the diesel engine of a motor vehicle.

  As shown in FIG. 1, the fuel injection control system of the present embodiment includes injectors IJ1 as fuel injection valves provided in each cylinder (four cylinders in the present embodiment) # 1 to # 4 of the in-vehicle diesel engine 13. IJ4 and an electronic control unit (hereinafter referred to as ECU) 11 that drives injectors IJ1 to IJ4 to control fuel injection to engine 13 are provided.

  In the present embodiment, the injectors IJ1 to IJ4 are of the solenoid valve type that opens by energizing the coil (opens the injection port), but the injectors IJ1 to IJ4 are of a type that opens and closes by a piezo actuator. May be good. Further, the fuel injection order of each cylinder # 1 to # 4 is “# 1 → # 3 → # 4 → # 2”.

  Each of the injectors IJ1 to IJ4 is connected to a fuel supply pipe 17 extending from a common rail 15 that is a fuel pressure storage container. The fuel stored in the fuel tank 19 of the vehicle is pumped to the common rail 15 by a fuel pump 21. The injectors IJ1 to IJ4 are opened when the high-pressure fuel stored in the common rail 15 is supplied through the fuel supply pipe 17 and is driven by the ECU 11 (the coil is energized). Then, the fuel is injected into cylinders # 1 to # 4 from its injection port (not shown). The fuel pump 21 is, for example, an engine-driven high-pressure pump that is driven by the rotation of the crankshaft of the engine 13 to perform a pump operation.

  Further, in the fuel supply piping 17 from the common rail 15 to each of the injectors IJ1 to IJ4, the end of the injectors IJ1 to IJ4 (that is, the fuel intake port of the injectors IJ1 to IJ4) has fuel pressure at that position (so-called inlet Fuel pressure sensors S1 to S4 for detecting the pressure) are provided. For this reason, the fuel pressure detected by the fuel pressure sensors S1 to S4 varies depending on the fuel injection operation of the injectors IJ1 to IJ4 corresponding to the fuel pressure sensors S1 to S4.

  In the present embodiment, the fuel pressure sensors S1 to S4 are provided in the injectors IJ1 to IJ4 and are constituent elements of the injectors IJ1 to IJ4. In the following description, the fuel pressure refers to the fuel pressure detected by the fuel pressure sensors S1 to S4 unless otherwise specified, and the fuel pressure at the fuel intake ports of the injectors IJ1 to IJ4. .

  Then, an analog sensor signal indicating a fuel pressure detected by the fuel pressure sensors S1 to S4 (a sensor signal having a voltage corresponding to the fuel pressure, hereinafter also referred to as a fuel pressure signal) is sent from each of the injectors IJ1 to IJ4. Input to the ECU 11 in parallel via individual sensor lines LS1 to LS4 (see FIG. 2). The injectors IJ1 to IJ4 are also in data communication with the ECU 11 via a common communication line LC (see FIG. 2).

  Further, the ECU 11 also receives signals from other sensors for detecting the operating state of the engine 13. Other sensors include, for example, the well-known crank angle sensor 23, an intake air sensor that detects the amount of intake air to the engine 13, a water temperature sensor that detects the cooling water temperature of the engine 13, an accelerator depression sensor, There are fuel ratio sensors and the like.

  On the other hand, the ECU 11 includes a microcomputer 25 that performs a fuel injection control process for injecting fuel to the injectors IJ1 to IJ4, and a communication driver 29 for communicating with the injectors IJ1 to IJ4. The microcomputer 25 includes an AD converter (ADC) 27 that performs AD conversion by switching fuel pressure signals from the injectors IJ1 to IJ4 one by one, and a well-known CPU, ROM, and RAM (not shown). Although not shown, the ECU 11 sends a drive signal (in this embodiment) for opening the injectors IJ1 to IJ4 according to the injection command signals for the injectors IJ1 to IJ4 output from the microcomputer 25. And a drive circuit for outputting a current flowing through the coils of the injectors IJ1 to IJ4.

Next, the connection state between the injectors IJ1 to IJ4 and the ECU 11 will be described with reference to FIG.
As shown in FIG. 2, between the injectors IJ1 to IJ4 and the ECU 11, in addition to the sensor lines LS1 to LS4 and the common communication lines LC for the injectors IJ1 to IJ4 described above, a common power line LP and A ground line LG is provided. The power supply line LP is a line for supplying a constant power supply voltage from the ECU 11 to the injectors IJ1 to IJ4. The ground line LG is a line connecting the ground line in the ECU 11 and the ground lines in the injectors IJ1 to IJ4. It is. That is, electric power is supplied from the ECU 11 to the injectors IJ1 to IJ4 via the power supply line LP and the ground line LG.

  Further, each of the injectors IJ1 to IJ4 is provided with a control IC 31 including a communication driver 33 for communicating with the ECU 11 via the communication line LC. The control IC 31 and the fuel pressure sensors S1 to S4 are operated by electric power supplied from the EC 11 via the power line LP and the ground line LG.

  In FIG. 2, the drive signal lines for supplying the drive signals for opening the injectors IJ1 to IJ4 from the ECU 11 to the injectors IJ1 to IJ4 are not shown.

  Next, the configuration of the fuel pressure sensors S1 to S4 and the control IC 31 provided in the injectors IJ1 to IJ4 will be described with reference to FIG. In the drawings and in the following description, “n” at the end of the reference sign such as #n, IJn, Sn, LSn is any one of 1 to 4 and corresponds to the cylinder #n. Show.

  As shown in FIG. 3, the fuel pressure sensor Sn provided in the injector IJn includes four resistors (so-called gauge resistors) R1 to R4 formed on the diaphragm (pressure receiving portion) so as to form a Wheatstone bridge circuit. When the excitation voltage Vi is applied between the terminals Ja and Jb, the resistance values of the resistors R1 to R4 change according to the fuel pressure, so that the output voltage Vo corresponding to the fuel pressure is generated between the terminals Jc and Jd. This is a well-known Wheatstone bridge type pressure sensor. In the fuel pressure sensor Sn, the gain (ratio of change in the output voltage Vo with respect to the fuel pressure) when the fuel pressure is converted into the output voltage Vo is increased according to the excitation voltage Vi.

  In addition to the communication driver 33, the control IC 31 includes a nonvolatile memory 35, a controller 37, a gain adjustment DA converter (gain adjustment DAC) 41, and an offset adjustment DA converter (offset adjustment DAC). ) 43, buffer circuits 45 and 47, a differential amplifier circuit 49, and an adder circuit 51.

The nonvolatile memory 35 stores in advance fixed information for controlling the fuel pressure sensor Sn.
The controller 37 includes a gain register GNREG and an offset register OFREG. Then, the controller 37 calculates a value to be stored in each of the gain register GNREG and the offset register OFREG based on the information acquired from the ECU 11 via the communication driver 33, and each calculated value is stored in the gain register GNREG. Stored in each of the offset registers OFREG. Further, the controller 37 outputs the digital data indicating the value stored in the gain register GNREG to the gain adjusting DA converter 41, and the digital data indicating the value stored in the offset register OFREG is used for offset adjustment. The data is output to the DA converter 43.

  The gain adjusting DA converter 41 outputs a voltage having a value indicated by the digital data supplied from the controller 37. The output voltage of the gain adjusting DA converter 41 is supplied to the terminal Ja of the fuel pressure sensor Sn via the buffer circuit 45. The terminal Jb of the fuel pressure sensor Sn is connected to the ground line. Therefore, the output voltage of the gain adjusting DA converter 41 is applied as the excitation voltage Vi between the terminals Ja and Jb of the fuel pressure sensor Sn.

  The offset adjustment DA converter 43 also outputs a voltage having a value indicated by the digital data supplied from the controller 37. The output voltage of the offset adjustment DA converter 43 is input to the adder circuit 51 via the buffer circuit 47.

The differential amplifier circuit 49 amplifies the output voltage (output voltage generated between the terminals Jc and Jd) Vo of the fuel pressure sensor Sn with a constant amplification factor and outputs the amplified voltage to the adder circuit 51.
The adder circuit 51 adds the output voltage of the offset adjustment DA converter 43 input from the buffer circuit 47 to the output voltage of the differential amplifier circuit 49, and outputs the voltage after the addition.

  The buffer circuit 53 outputs the output voltage of the adding circuit 51 to the sensor line LSn corresponding to the injector IJn as a fuel pressure signal (sensor signal) indicating the fuel pressure detected by the fuel pressure sensor Sn. The fuel pressure signal is input to the ECU 11 via the sensor line LSn.

  With such a configuration, the control IC 31 of the injector IJn adjusts the excitation voltage Vi supplied from the gain adjustment DA converter 41 to the fuel pressure sensor Sn based on the information acquired from the ECU 11 through communication. A gain (a rate of change of the fuel pressure signal with respect to the fuel pressure) when the fuel pressure detected by the fuel pressure sensor Sn is converted into a fuel pressure signal is adjusted. The control IC 31 adjusts the offset potential of the fuel pressure signal output to the ECU 11 by adjusting the output voltage of the offset adjustment DA converter 43 based on the information acquired from the ECU 11 through communication.

In the fuel injection control system with the hardware configuration as described above, the microcomputer 25 of the ECU 11 performs, for example, the following processes [1] to [6] for each cylinder #n.
[1] A process in which the fuel pressure signal from the injector IJn is AD-converted by the AD converter 27 at regular intervals, and the fuel pressure (inlet pressure of the injector IJn) is detected from the AD conversion result (AD conversion value).

  [2] A target injection state (for example, injection start timing) based on the fuel pressure detected before driving the injector IJn (when fuel is not injected) and control parameters such as the engine speed and the accelerator opening. And the basic value of the output start timing and output duration of the injection command signal for the injector IJn necessary to realize the target injection state.

  [3] The injection state such as the actual injection start timing and the injection amount is determined from the fuel pressure at regular intervals detected in a specific injection state monitoring period including the period during which the injector IJn is driven (fuel injection period of cylinder #n). The process which detects and calculates the correction value for correct | amending the output start timing and output continuation time of an injection command signal from the detection result.

  [4] The output start timing and the output continuation time of the injection command signal calculated in the process of [2] are corrected by the correction value calculated in the process of [3] to start the output of the injection command signal. Process to finally determine timing and output duration.

[5] A process of outputting an injection command signal for the injector IJn as a result determined in the process of [4].
[6] A process of controlling the fuel pump 21 so that the fuel pressure detected when the injector IJn is not driven becomes a target value.

The processes [2] to [6] correspond to the fuel injection control process, and the processes [2] and [6] correspond to the basic control process described in the section “Background Art”. Yes.
Here, in the present embodiment, the microcomputer 25 of the ECU 11 determines, for each cylinder #n, a predetermined period that does not include the fuel injection period of the cylinder #n (in this embodiment, from the transition timing from the expansion stroke to the exhaust stroke) In the period of 360 ° CA from the intake stroke to the compression stroke), the fuel pressure is changed from the predetermined basic lower limit pressure PMINB to the predetermined basic upper limit pressure PMAXB based on the fuel pressure signal from the injector IJn. The above processes [2] and [6] are performed using the fuel pressure detected in the basic detection range up to and detected during this period.

  “CA” means a crank angle. In the present embodiment, the basic detection range is the maximum change range from the minimum value to the maximum value at which the fuel pressure is considered to change normally. For example, the basic detection range is set to a range of 0 to 220 MPa. Therefore, as shown in FIG. 4A, the basic lower limit pressure PMINB is 0 MPa, and the basic upper limit pressure PMAXB is 220 MPa.

  When the microcomputer 25 detects the fuel pressure in the basic detection range (maximum change range), the microcomputer 25 instructs the injector IJn (specifically, the control IC 31) to specify the following gain and offset potential values. Information (equivalent to command information for the basic detection range) is transmitted. As shown in FIG. 4A, when the fuel pressure changes in the basic detection range (0 to 220 MPa), the fuel pressure signal from the injector IJn is The maximum voltage range in which the AD converter 27 can perform AD conversion correctly is a gain and an offset potential that change in a voltage range from a predetermined basic lower limit voltage VMINB to a predetermined basic upper limit voltage VMAXB.

  In FIG. 4, “sensor output voltage” means the voltage value of the fuel pressure signal. In the present embodiment, as shown in FIG. 4A, the basic lower limit voltage VMINB is 1.0V, and the basic upper limit voltage VMAXB is 4.0V.

  Further, the microcomputer 25 for each cylinder #n has a specific injection state monitoring period including the fuel injection period of the cylinder #n (in this embodiment, from the transition timing from the intake stroke to the compression stroke, from the expansion stroke to the exhaust stroke). In the period of 360 ° CA until the timing of transition to), based on the fuel pressure signal from the injector IJn, the fuel pressure is in a limited detection range narrower than the basic detection range, and its injection state monitoring period Detecting in the range where the fuel pressure is expected to change. Then, the process [3] is performed using the fuel pressure detected during the injection state monitoring period.

  Further, when the microcomputer 25 detects the fuel pressure within the limited detection range, the microcomputer 25 instructs the injector IJn (specifically, the control IC 31) to instruct the following values of gain and offset potential as follows (limited detection range). Equivalent to the command information). As illustrated in FIG. 4B, the gain and offset potential indicated by the command information change when the fuel pressure changes within a limited detection range (in the example of FIG. 4B, a range of 30 to 110 MPa). The fuel pressure signal from the injector IJn is a gain and an offset potential that change in the voltage range from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB.

Then, next, the outline | summary of the process performed in order to detect a fuel pressure by the microcomputer 25 of ECU11 and control IC31 of the injector IJn is demonstrated.
First, the principle will be described.

  In the microcomputer 25 of the ECU 11, as shown in FIG. 4B, when the fuel pressure changes from the detection lower limit pressure PMIN that is the lower limit value of the detection range to the detection upper limit pressure PMAX that is the upper limit value of the detection range, the fuel pressure Assuming that the signal voltage (sensor output voltage) V changes in the maximum voltage range from the basic lower limit voltage VMINB that can be AD converted by the AD converter 27 to the basic upper limit voltage VMAXB, The fuel pressure P is calculated from the voltage of the fuel pressure signal (specifically, the AD conversion value of the fuel pressure signal) Vs by Equation 2. Note that “b” in Equations 1 and 2 is a conversion coefficient for converting the fuel pressure signal into the fuel pressure.

P = (Vs−VMMIN) · b + PMIN Equation 1
b = (PMAX−PMIN) / (VMAXB−VMINB) Equation 2
In this embodiment, when the fuel pressure is detected in the basic detection range of 0 to 220 [PMa], as shown in FIG. 4A, when the fuel pressure is the basic lower limit pressure PMINB, When the pressure signal is the basic lower limit voltage VMINB and the fuel pressure is the basic upper limit pressure PMAXB, the fuel pressure signal is the basic upper limit voltage VMAXB.

  That is, the fuel pressure sensor Sn and the control IC 31 on the injector IJn side basically output the fuel pressure in the basic detection range (PMINB to PMAXB) as a voltage from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB.

  Hereinafter, the relationship between the fuel pressure signal voltage (sensor output voltage) and the fuel pressure shown in FIG. 4A is referred to as a basic characteristic. In this embodiment, the detection range of the fuel pressure is changed. However, in the case of the detection range having the maximum width (that is, the basic detection range), the basic characteristics shown in FIG. .

  On the other hand, the control IC 31 of the injector IJn is a detection lower limit pressure PMIN that is a lower limit value of the detection range and an upper limit value of the detection range as information indicating the detection range of the fuel pressure determined by the microcomputer 25 from the ECU 11. The voltage value of the fuel pressure signal with the above basic characteristic corresponding to each of the detection upper limit pressures PMAX is transmitted. Hereinafter, the voltage value of the fuel pressure signal in the basic characteristic corresponding to the detection lower limit pressure PMIN is referred to as the lower limit voltage VMIN, and the voltage value of the fuel pressure signal in the basic characteristic corresponding to the detection upper limit pressure PMAX is referred to as the upper limit voltage VMAX. Say.

  In the case of the basic characteristics shown in FIG. 4A, for example, if the detection lower limit pressure PMIN is 30 MPa and the detection upper limit pressure PMAX is 110 MPa, the lower limit voltage VMIN is 1.41 V and the upper limit voltage VMAX is 2.5 V. When the detection lower limit pressure PMIN is 0 MPa of the basic lower limit pressure PMINB and the detection upper limit pressure PMAX is 220 MPa of the basic upper limit pressure PMAXB, the lower limit voltage VMIN is 1.0 V of the basic lower limit voltage VMINB, and the upper limit voltage VMAX is the basic upper limit voltage. It becomes 4.0V of VMAXB.

  In the control IC 31 of the injector IJn, the controller 37 calculates the offset adjustment value DZ to be stored in the offset register OFREG from the lower limit voltage VMIN and the upper limit voltage VMAX transmitted from the ECU 11 according to the following expressions 3 and 4. A gain adjustment value DG to be stored in the gain register GNREG is calculated.

DZ = (VMINB−VMIN) / KZ1 + KZ2 Equation 3
DG = KG1 / (VMAX−VMIN) + KG2 Equation 4
In Equation 3, KZ1 and KZ2 are offset coefficients, which compensate for variations in the characteristics of the circuit on the injector IJn side including the fuel pressure sensor Sn and when “fuel pressure = detection lower limit pressure PMIN”. In addition, the value is set such that “the voltage of the fuel pressure signal = the basic lower limit voltage VMINB”. For example, if the circuit characteristics are ideal and the output voltage of the differential amplifier circuit 49 is 0 V when “fuel pressure = 0”, KZ1 is set to 1 and KZ2 is set to VMINB.

  In Equation 4, KG1 and KG2 are gain coefficients, which compensate for variations in the characteristics of the circuit on the injector IJn side including the fuel pressure sensor Sn, and the voltage range from the lower limit voltage VMIN to the upper limit voltage VMAX. The value is set to a value that expands to a voltage range (maximum voltage range in which AD conversion is possible) from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB. For example, if the circuit characteristics are ideal and KG2 is 0, KG1 is set to "VMAXB-VMINB".

  The voltage indicated by the offset adjustment value DZ is output from the offset adjustment DA converter 43 and input to the adding circuit 51, and the voltage indicated by the gain adjustment value DG is output from the gain adjustment DA converter 41 and fuel. When the fuel pressure changes from the detection lower limit pressure PMIN to the detection upper limit pressure PMAX by being supplied to the pressure sensor Sn as the excitation voltage Vi, the fuel pressure signal to the sensor line LSn is changed from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB. A changing sensor output characteristic is realized.

  Further, in the ECU 11, the microcomputer 25 predicts the change range of the fuel pressure in the current injection state monitoring period at the start of the injection state monitoring period for each cylinder #n, and uses the predicted change range as the above-described limited detection range. And Then, from the limited range lower limit pressure PMINLMT that is the lower limit value of the limited detection range and the limited range upper limit pressure PMAXLMT that is the upper limit value of the limited detection range, The limited range upper limit voltage VMAXLMT is calculated.

  The limited range lower limit pressure PMINLMT is also the detection lower limit pressure PMIN when the fuel pressure detection range is the limited detection range, and the limited range upper limit pressure PMAXXLMT is detected when the fuel pressure detection range is the limited detection range. It is also the upper limit pressure PMAX. The limited range lower limit voltage VMINLMT is the voltage value of the fuel pressure signal with the basic characteristics corresponding to the limited range lower limit pressure PMINLMT, and the limited range upper limit voltage VMAXLMT is the fuel with the basic characteristics corresponding to the limited range upper limit pressure PMAXLMT. This is the voltage value of the pressure signal. Further, “a” in Expressions 5 to 7 is the slope of the straight line of the basic characteristics.

VMINLMT = (PMINLMT−PMINB) · a + VMINB Equation 5
VMAXLMT = (PMAXXLMT−PMINB) · a + VMINB Equation 6
a = (VMAXB−VMMINB) / (PMAXB−PMINB) Equation 7
Further, for each cylinder #n, the microcomputer 25 provides the limited range as information indicating the detection range of fuel pressure (in this case, the limited detection range) to the injector IJn of the cylinder #n at the start of the injection state monitoring period. The lower limit voltage VMINLMT and the limited range upper limit voltage VMAXLMT are transmitted. Then, the limited range lower limit voltage VMINLMT and the limited range upper limit voltage VMAXLMT transmitted at this time are such that when the fuel pressure changes in the limited detection range, the fuel pressure signal from the injector IJn changes from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB. It is also command information for a limited detection range that commands a gain and an offset potential that change in the voltage range.

  Further, the microcomputer 25 uses the basic lower limit voltage as information indicating the detection range of fuel pressure (in this case, the basic detection range) to the injector IJn of each cylinder #n at the end of the injection state monitoring period. VMINB and basic upper limit voltage VMAXB are transmitted. The basic lower limit voltage VMINB and the basic upper limit voltage VMAXB transmitted at this time are a voltage range from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB when the fuel pressure changes in the basic detection range. It is also command information for the basic detection range that commands the gain and offset potential that will change at

  On the other hand, each value (fixed value) of the basic lower limit voltage VMINB, the basic upper limit voltage VMAXB, the offset coefficients KZ1, KZ2, and the gain coefficients KG1, KG2 is stored in advance in the non-volatile memory 35 on the injector IJn side. Also on the ECU 11 side, each value (basic lower limit voltage VMINB, basic upper limit voltage VMAXB, basic lower limit pressure PMINB, basic upper limit pressure PMAXB) is stored in a nonvolatile memory (not shown) provided inside or outside the microcomputer 25. (Fixed value) is stored in advance.

Next, the contents of processing performed to detect the fuel pressure by the microcomputer 25 of the ECU 11 and the control IC 31 of the injector IJn will be described using a flowchart.
First, FIG. 5 is a flowchart showing a pressure detection range switching process executed by the microcomputer 25 of the ECU 11. This pressure detection range switching process is executed each time the crank angle of the engine 13 detected based on the signal from the crank angle sensor 23 advances by a predetermined angle. This process may be executed at a timing of every 180 ° CA, which is a timing at which each cylinder shifts from the suction stroke to the compression stroke.

  As shown in FIG. 5, when the microcomputer 25 starts the pressure detection range switching process, first, in S110, the transition timing from the suction stroke of the first cylinder # 1 to the compression stroke (exhaust from the expansion stroke of the fourth cylinder # 4). If it is determined that the timing is affirmative, the first cylinder # 1 is determined as the limited cylinder in the next S120, and the fourth cylinder # 4 is determined as the full-range cylinder, and thereafter, the process proceeds to S190, and a detection range command process described later is performed.

  The limited cylinder is a cylinder that detects the fuel pressure within the above-described limited detection range (in other words, the fuel pressure detection range is set to the limited detection range), and the all-range cylinder is based on the fuel pressure. The cylinder is detected in the detection range (in other words, the detection range of the fuel pressure is set as the basic detection range).

  If a negative determination (NO) is made in S110, the process proceeds to S130, and the transition timing from the suction stroke of the third cylinder # 3 to the compression stroke (exhaust from the expansion stroke of the second cylinder # 2). If it is determined that it is also the timing of transition to the stroke), if the determination is affirmative that the timing is reached, the process proceeds to S140. In S140, the third cylinder # 3 is determined as a limited cylinder, and the second cylinder # 2 is determined as a full-range cylinder. Thereafter, the process proceeds to S190, and a detection range command process described later is performed.

  If the determination in S130 is negative (NO), the process proceeds to S150, and the transition timing from the intake stroke of the fourth cylinder # 4 to the compression stroke (exhaust from the expansion stroke of the first cylinder # 1). If it is determined that it is also the timing of transition to the stroke, and if it is determined that the timing is affirmative, the process proceeds to S160. In S160, the fourth cylinder # 4 is determined as the limited cylinder, and the first cylinder # 1 is determined as the full-range cylinder. Then, the process proceeds to S190, and a detection range command process described later is performed.

  If the determination in S150 is negative (NO), the process proceeds to S170, and the transition timing from the suction stroke of the second cylinder # 2 to the compression stroke (exhaust from the expansion stroke of the third cylinder # 3). If it is determined that it is also the timing of transition to the stroke), and if the determination is affirmative, the process proceeds to S180. In S180, the second cylinder # 2 is determined as a limited cylinder, and the third cylinder # 3 is determined as a full-range cylinder. Then, the process proceeds to S190, and a detection range command process described later is performed.

If a negative determination (NO) is made in S170, the pressure detection range switching process is terminated as it is.
With the above processing, each cylinder #n is switched from the full range cylinder to the limited cylinder at the transition timing from the intake stroke to the compression stroke, and from the limited cylinder to the full range cylinder at the transition timing from the expansion stroke to the exhaust stroke. It will be switched. For this reason, each cylinder #n is a limited cylinder in the injection state monitoring period of 360 ° CA from the transition timing from the intake stroke to the compression stroke to the transition timing from the expansion stroke to the exhaust stroke. In this period (that is, a period of 360 ° CA from the transition timing from the expansion stroke to the exhaust stroke to the transition timing from the intake stroke to the compression stroke), the cylinders are set to the entire range.

Next, FIG. 6 is a flowchart showing the detection range command process executed in S190 of FIG.
As shown in FIG. 6, when the microcomputer 25 starts the detection range command process, first, in S220, the fuel pressure detection range for the limited cylinder #x (x is any one of 1 to 4) determined in the current process. And a limited detection range calculation process (FIG. 7) for calculating command information (command information for the limited detection range) to be transmitted to the injector IJx of the limited cylinder #x. .

  As shown in FIG. 7, in the limited detection range calculation process, first, in S223, from the injector IJx during the current operating state of the engine 13 and the 360 ° CA period before the current injection state monitoring period arrives. Based on the fuel pressure detected based on the fuel pressure signal (that is, the fuel pressure detected when the fuel injection to the cylinder #x is not performed, hereinafter referred to as the fuel pressure when the injection is not performed), this 360 ° The change range of the fuel pressure in the injection state monitoring period for CA is predicted.

  Specifically, the output continuation time of the injection command signal of the injector IJx determined based on the operating state of the engine 13 such as the accelerator opening and the coolant temperature (equivalent to the time for opening the injector IJx), and when the injection is not performed Is applied to a pressure change range calculation map prepared in advance, for example, to calculate an upper limit value and a lower limit value of the fuel pressure change range in the current injection state monitoring period.

  Note that the pressure change range calculation map generally has a tendency that the longer the duration of output of the injection command signal (that is, the longer the injection time), the wider the range of the predicted fuel pressure change range, and the injection The upper limit value and the lower limit value of the predicted fuel pressure change range are set higher as the non-implemented fuel pressure increases.

  In S223, the lower limit value of the calculated fuel pressure change range (that is, the calculated lower limit value of the limited detection range) is set as the limited range lower limit pressure PMINLMT, and the calculated upper limit value of the fuel pressure change range (that is, the lower limit value). The calculated upper limit value of the limited detection range is set as the limited range upper limit pressure PMAXXLMT.

  Then, in the limited detection range calculation process, in the next S225, the limited range lower limit pressure PMINLMT and the limited range upper limit pressure PMAXXLMT set in S223 are substituted into the above-described Expressions 5 to 7, so that the limited detection range is calculated. The limited range lower limit voltage VMINLMT and the limited range upper limit voltage VMAXLMT are calculated as the command information, and then the limited detection range calculation process ends.

  Returning to FIG. 6, when the above-described limited detection range calculation processing is completed, in the next S230, AD conversion of the fuel pressure signal related to the limited cylinder #x determined in the current processing is disabled (prohibited), and the subsequent S240. Then, the limited range lower limit voltage VMINLMT and the limited range upper limit voltage VMAXLMT as the command information for the limited detection range calculated in S220 (S225) are transmitted to the injector IJx of the limited cylinder #x. By transmitting both the voltages VMINLMT and VMAXLMT, the fuel pressure detection range (limited detection range) is notified to the injector IJx.

  In the next S250, the process waits until a normal response is received from the injector IJx of the limited cylinder #x. If a normal response is received, the process proceeds to S260. Note that the normal response from the injector IJx received in S250 indicates that the information from the ECU 11 (in this case, VMINLMT, VMAXLMT) has been received, and is transmitted in S450 of FIG. 8 described later.

  In S260, the limited range lower limit pressure PMINLMT calculated in S220 (S223) is set as the detection lower limit pressure PMIN [x] for the limited cylinder #x, and the detection upper limit pressure PMAX [x] for the limited cylinder #x. The limited range upper limit pressure PMAXLMT calculated in S220 (S223) is set. The detection lower limit pressure PMIN [x] and the detection upper limit pressure PMAX [x] set here are determined from the AD conversion value of the fuel pressure signal of the cylinder #x in S640 in the AD conversion process of FIG. Used to calculate pressure.

In the next S270, AD conversion of the fuel pressure signal related to the limited cylinder #x is set to be permitted (permitted). That is, the impossibility set in S230 is canceled.
Next, in S280, AD conversion of the fuel pressure signal relating to the all-cylinder cylinder #y (y is any one of 1 to 4) determined in the current processing is set to disabled (prohibited), and in S290, basic detection is performed. The basic lower limit voltage VMINB and the basic upper limit voltage VMAXB as command information for the range are transmitted to the injector IJy of the all-cylinder #y. By transmitting both the voltages VMINB and VMAXB, the fuel pressure detection range (basic detection range) is notified to the injector IJy.

  Then, in the next S300, the process waits until a normal response is received from the injector IJy of the entire cylinder #y. If a normal response is received, the process proceeds to S310. The normal response from the injector IJy received in S300 also indicates that information (in this case, VMMINB, VMAXB) from the ECU 11 has been received, and is transmitted in S450 in FIG. 8 described later.

  In S310, the basic lower limit pressure PMINB is set as the detection lower limit pressure PMIN [y] for the entire range cylinder #y, and the basic upper limit pressure PMAXB is set as the detection upper limit pressure PMAX [y] for the entire range cylinder #y. The detection lower limit pressure PMIN [y] and the detection upper limit pressure PMAX [y] set here are determined from the AD conversion value of the fuel pressure signal of the cylinder #y in S640 in the AD conversion process of FIG. Used to calculate pressure.

In the next S320, the AD conversion of the fuel pressure signal for the entire cylinder #y is set to be permitted (permitted). That is, the impossibility set in S280 is canceled.
When the process of S320 ends, the detection range command process ends, and the pressure detection range switching process of FIG. 5 also ends accordingly.

Next, FIG. 8A is a flowchart showing an output adjustment process executed by the control IC 31 of each injector IJn.
In this output adjustment process, when the fuel pressure changes within the detection range (limited detection range or basic detection range) determined by the microcomputer 25 of the ECU 11, the fuel pressure signal changes from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB. This is a process for adjusting the gain and offset potential for outputting the fuel pressure signal so as to change in the voltage range. Further, this output adjustment processing is executed by the controller 37 in the control IC 31 when the power supply voltage is supplied from the ECU 11 to the injector IJn as the vehicle ignition is turned on and the control IC 31 is activated.

  As shown in FIG. 8A, when starting the output adjustment process, the controller 37 of the control IC 31 first initializes the variable lower limit voltage VMIN and the upper limit voltage VMAX in S410. Specifically, the lower limit voltage VMIN is set to a basic lower limit voltage VMINB (= 1.0 V) as an initial value, and the upper limit voltage VMAX is set to a basic upper limit voltage VMAXB (= 4.0 V) as an initial value.

Next, in S420, an adjustment value calculation process shown in FIG. 8B for calculating the offset adjustment value DZ and the gain adjustment value DG is executed.
In this adjustment value calculation process, first, in S510, the offset adjustment value DZ is calculated by substituting the lower limit voltage VMIN into Equation 3 described above. In subsequent S520, the gain adjustment value DG is calculated by substituting the lower limit voltage VMIN and the upper limit voltage VMAX into Equation 4 described above.

  Returning to FIG. 8A, when the adjustment value calculation process in S420 is completed, in the next S430, the offset adjustment value DZ calculated in S420 is set in the offset register OFREG, and the gain adjustment calculated in S420 is performed. The value DG is set in the gain register GNREG.

  Then, in the next S440, it is determined whether or not a lower limit voltage and an upper limit voltage as command information from the ECU 11 have been received. The lower limit voltage and upper limit voltage received here are those transmitted in S240 or S290 of FIG.

  If it is determined in S440 that the lower limit voltage and the upper limit voltage have not been received, the process proceeds to S490, and the gain adjustment DA converter 41 DA converts the gain adjustment value DG in the gain register GNREG. Thus, the voltage indicated by the gain adjustment value DG is supplied to the fuel pressure sensor Sn as the excitation voltage Vi. Further, in S500, the offset adjustment value DZ in the offset register OFREG is DA-converted by the offset adjustment DA converter 43, whereby the voltage indicated by the offset adjustment value DZ is supplied to the addition circuit 51. Then, the process returns to S440.

If it is determined in S440 that the lower limit voltage and the upper limit voltage have been received, the process proceeds to S450.
In S450, the above-mentioned normal response is transmitted to the ECU 11, and in the subsequent S460, the lower limit voltage VMIN is set to the lower limit voltage (VMINLMT or VMINB) received from the ECU 11 at this time, and the upper limit voltage VMAX is changed from the ECU 11 to the upper limit voltage (currently received). VMAXLMT or VMAXB).

  In subsequent S470, the adjustment value calculation process of FIG. 8B is executed again. In the adjustment value calculation process in this case, each of the lower limit voltage and the lower limit voltage received from the ECU 11 is used as the lower limit voltage VMIN and the upper limit voltage VMAX in Expressions 3 and 4, respectively. A gain adjustment value DG is calculated.

  Further, in next S480, the offset adjustment value DZ calculated in S470 is reset in the offset register OFREG, and similarly, the gain adjustment value DG calculated in S470 is reset in the gain register GNREG. Then, the process proceeds to S490.

  As a result of such output adjustment processing, in the control IC 31 of each injector IJn, when the limited range lower limit voltage VMINLMT and the limited range upper limit voltage VMAXLMT are transmitted from the ECU 11, the limited detection range (that is, both the voltages VMINLMT and VMAXLMT represent) When the fuel pressure changes in the range from the limited range lower limit pressure PMINLMT to the limited range upper limit pressure PMAXLMT), the fuel pressure is changed so that the fuel pressure signal changes in the range from the basic lower limit voltage VMINB to the basic upper limit voltage VMAXB. The gain to be converted into the signal and the offset potential of the fuel pressure signal are set. Further, when the basic lower limit voltage VMINB and the basic upper limit voltage VMAXB are transmitted from the ECU 11, if the fuel pressure changes in the detection range (that is, the basic detection range) represented by both the voltages VMINB and VMAXB, the fuel pressure signal is The gain and the offset potential are set so as to change in the range from the lower limit voltage VMINB to the basic upper limit voltage VMAXB.

  Next, FIG. 9 is a flowchart showing an AD conversion process executed by the microcomputer 25 of the ECU 11. This AD conversion process is executed at regular time intervals (for example, every several tens of μs) at which the fuel pressure signal from each injector IJn should be AD converted.

As shown in FIG. 9, when the microcomputer 25 starts executing the AD conversion process, a cylinder number counter CN indicating the number of the cylinder to be processed is first initialized to 1 in S610.
Then, in next S620, it is determined whether or not the AD conversion of the fuel pressure signal is set to be possible for the cylinder indicated by the value of the cylinder number counter CN (hereinafter referred to as cylinder (#CN)). Whether AD conversion is possible or not is set in each of S230, S270, S280, and S320 in FIG.

  If the AD conversion of the fuel pressure signal is enabled for the cylinder (#CN) (S620: YES), the process proceeds to S630, and the fuel pressure signal of the cylinder (#CN) (specifically, the cylinder (#CN) The fuel pressure signal from the injector IJ (CN) is AD converted by the AD converter 27 and the AD conversion value Vs [CN] is stored.

  Then, in the next S640, by substituting the AD conversion value Vs [CN] as “Vs” in Equations 1 and 2, the fuel pressure P [CN] indicated by the fuel pressure signal of the cylinder (#CN) is obtained. ] And the calculated fuel pressure P [CN] is stored.

  When calculating the fuel pressure P [CN] in S640, each of “PMIN” and “PMAX” in Equations 1 and 2 is the cylinder (#CN) in S260 or S310 of FIG. ) Is used for each of the detection lower limit pressure PMIN [CN] and the detection upper limit pressure PMAX [CN]. For this reason, when the equations used to calculate the fuel pressure P [CN] in S640 are described again, the following equations 8 and 9 are obtained.

P [CN] = (Vs [CN] −VMINB) · b + PMIN [CN] (Equation 8)
b = (PMAX [CN] −PMIN [CN]) / (VMAXB−VMINB) (Equation 9)
The detection lower limit pressure PMIN [CN] and the detection upper limit pressure PMAX [CN] are the command information (lower limit voltage and upper limit voltage) transmitted to the injector IJ (CN) of the cylinder (#CN) in S240 or S290 of FIG. In the end, the microcomputer 25 of the ECU 11 calculates the fuel pressure based on the content of the command information transmitted to the injector IJn and the AD conversion value of the fuel pressure signal. become.

Then, when the process of S640 is completed, the process proceeds to S650.
If it is determined in S620 that the AD conversion of the fuel pressure signal is disabled for the cylinder (#CN) (S620: NO), the process proceeds to S650 as it is.

  In S650, the cylinder number counter CN is incremented (+1). In S660, it is determined whether or not the value of the cylinder number counter CN exceeds 4. If the value of the cylinder number counter CN does not exceed 4 (S660: NO), the process returns to S620, but if the value of the cylinder number counter CN exceeds 4 (S660: YES), the process for all cylinders is performed. Therefore, the AD conversion process is terminated.

  If the cylinder (#CN) indicated by the value of the cylinder number counter CN is a limited cylinder, the fuel pressure P [CN] for each fixed time calculated in S640 is the process of [3] described above. This is used for (processing for detecting the injection state). Further, if the cylinder (#CN) is a full-range cylinder, at least one fuel pressure P [CN] calculated in S640 is processed in the above-described processes [2] and [6] (basic control process). Used for.

  On the other hand, in the above embodiment, the ECU 11 and the injector IJn constitute a fuel injection control device, the microcomputer 25 of the ECU 11 corresponds to the control means, the injector IJn corresponds to the fuel injection valve, and the fuel pressure sensor Sn. The control IC 31 corresponds to the fuel pressure detection means, the communication driver 33 corresponds to the communication means, and the gain adjustment DA converter 41 and the offset adjustment DA converter 43 correspond to the output characteristic adjustment means. . The injector IJn also corresponds to a fuel injection device, and the microcomputer 25 of the ECU 11 also corresponds to a control device.

  According to the above embodiment, the microcomputer 25 of the ECU 11 detects the fuel pressure of each cylinder #n in a wide basic detection range in a period other than the injection state monitoring period, but the injection state monitoring period (the fuel injection period is set). In a specific period including), a change range predicted to change in that period is detected in a limited detection range that is narrower than the basic detection range, and the fuel pressure is detected in the basic detection range. In either case, when the fuel pressure changes in the detection range (detection target range) by changing the command information transmitted to the injector IJn between the case and the detection in the limited detection range, the fuel pressure signal is converted into the AD converter 27. Output characteristics of the fuel pressure signal on the injector IJn side so as to change within the maximum voltage range (VMINB to VMAXB) that can be AD converted by In and the offset potential) is variably set.

  For this reason, when the fuel pressure is detected in the limited detection range, the fuel pressure value (the value of the fuel pressure detection resolution) represented by the LSB of the AD converter 27 is smaller than in the case where the fuel pressure is detected in the basic detection range. As a result, even if the number of bits of the AD converter 27 is not increased, the detection resolution when detecting the fuel pressure within the limited detection range can be increased.

  Therefore, the fuel pressure at the time of fuel injection that changes in a narrower range than the basic detection range (fuel pressure in the injection state monitoring period) can be detected with high resolution and high accuracy without increasing the number of bits of the AD converter 27. be able to. Since it is not necessary to increase the number of bits of the AD converter 27, fuel pressure detection such as a process of transferring data as an AD conversion result from the AD converter 27 to a memory and a process of calculating the data are performed. Therefore, the processing load can be reduced. As a result, it is possible to accurately detect the actual injection state from the fuel pressure in the injection state monitoring period with a small processing load. For this reason, the AD conversion interval can be set short.

Further, the fuel pressure can be detected within the maximum basic detection range during the period other than the injection state monitoring period.
Further, the microcomputer 25 of the ECU 11 determines the change range of the fuel pressure in the injection state monitoring period (which is also a range in which the fuel pressure is detected) from the fuel pressure during non-injection detected before the injection state monitoring period arrives. Since the prediction is performed, the prediction accuracy can be increased.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to such Embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect. .

  For example, the fuel pressure used for predicting the change range of the fuel pressure is not the fuel pressure detected from the fuel pressure signal of the same cylinder, but the fuel pressure detected from the fuel pressure signals of other cylinders not performing fuel injection. It may be used. In addition, the fuel pressure detected by the pressure sensor provided on the common rail 15 may be used for prediction. On the other hand, in any case, prediction may be made by using a value (average value or so-called annealing value) obtained by averaging the fuel pressure detected a plurality of times.

  In the above-described embodiment, the lower limit voltage and the upper limit voltage are transmitted from the ECU 11 to the injector IJn as command information for instructing the gain and the offset potential. However, the offset adjustment value DZ and the gain adjustment value DG are used as the command information. You may comprise so that it may transmit.

  More specifically, the microcomputer 25 of the ECU 11 substitutes the limited range lower limit voltage VMINLMT and the limited range upper limit voltage VMAXLMT as “VMIN” and “VMAX” in Equations 3 and 4 in S240 of FIG. The offset adjustment value DZ and the gain adjustment value DG are calculated, and the calculated values DZ and DG may be transmitted to the injector IJx of the limited cylinder #x. Similarly, in S290 of FIG. By substituting VMINB and the basic upper limit voltage VMAXB as “VMIN” and “VMAX” in Equations 3 and 4, the offset adjustment value DZ and the gain adjustment value DG are calculated, and the calculated values DZ and DG are calculated. And may be transmitted to the injectors IJy of the entire cylinder #y. In this case, if the control IC 31 of each injector IJn determines that the offset adjustment value DZ and the gain adjustment value DG from the ECU 11 are received in S440 of FIG. 8A, the received values DZ, DG. May be set in each of the offset register OFREG and the gain register GNREG in S480.

  On the other hand, the positions where the pressure sensors S1 to S4 are provided are not limited to the fuel intake ports of the injectors IJ1 to IJ4, but from the fuel outlet of the common rail 15 (the end on the common rail 15 side of the fuel supply pipe 17) of the injectors IJ1 to IJ4. It may be at any position in the fuel passage to the injection port.

  The target of fuel injection control may be a gasoline engine.

  DESCRIPTION OF SYMBOLS 11 ... ECU (electronic control apparatus), 13 ... Engine (vehicle-mounted diesel engine), 15 ... Common rail, 17 ... Fuel supply piping, 19 ... Fuel tank, 21 ... Fuel pump, 23 ... Crank angle sensor, 25 ... Microcomputer, 27 ... AD converter, 29, 33 ... Communication driver, IJ1-IJ4 ... Injector, S1-S4 ... Fuel pressure sensor, 31 ... Control IC, 35 ... Non-volatile memory, 37 ... Controller, 41 ... DA converter for gain adjustment, 43 ... DA converter for offset adjustment, 45, 47, 53 ... buffer circuit, 49 ... differential amplifier circuit, 51 ... adder circuit, GNREG ... gain register, OFREG ... offset register, LC ... communication line, LG ... ground line, LP ... Power supply line, LS1 to LS4 ... Sensor line

Claims (7)

A fuel injection valve that injects fuel supplied from an accumulator that stores fuel pumped by a fuel pump from an injection port into a cylinder of an internal combustion engine;
Provided at a predetermined position in a fuel passage from a fuel outlet of the pressure accumulating container to an injection port of the fuel injection valve, and detecting a fuel pressure in the fuel passage that varies with fuel injection from the injection port to the cylinder; Fuel pressure detecting means for outputting a sensor signal having a voltage corresponding to the fuel pressure;
Control means for performing fuel injection control processing for injecting fuel into the fuel injection valve,
The control means includes an AD converter that AD converts the sensor signal from the fuel pressure detection means, detects the fuel pressure from an AD conversion result by the AD converter, and a detected value of the fuel pressure A fuel injection control device for performing the fuel injection control process using
The fuel pressure detection means includes a communication means for communicating with the control means, a gain when the fuel pressure detection means converts the fuel pressure into the sensor signal, and the fuel pressure detection means to the control means. Output characteristic adjusting means for adjusting the offset potential of the sensor signal to be output,
Command information representing each value of the gain and the offset potential is transmitted from the control means to the fuel pressure detection means,
When the fuel pressure detection means receives the command information by the communication means, the output characteristic adjustment means sets the gain and the offset potential to values represented by the received command information;
A fuel injection control device. The fuel injection control device according to claim 1,
The control means includes
When the fuel pressure is detected in a basic detection range from a predetermined basic lower limit pressure to a predetermined basic upper limit pressure, and the fuel pressure is a detection range narrower than the basic detection range, May be detected in a limited detection range from a higher lower limit pressure to an upper limit pressure lower than the basic upper limit pressure,
When the fuel pressure is detected in the basic detection range, as the command information, when the fuel pressure changes in the basic detection range, the sensor signal is in a voltage range in which the AD converter can perform AD conversion. Thus, command information for the basic detection range representing each value of the gain and the offset potential that changes in a voltage range from a predetermined basic lower limit voltage to a predetermined basic upper limit voltage is sent to the fuel pressure detection means. Send
When the fuel pressure is detected in the limited detection range, as the command information, when the fuel pressure changes in the limited detection range, the sensor signal has a voltage range from the basic lower limit voltage to the basic upper limit voltage. Transmitting command information for a limited detection range representing each value of the gain and the offset potential to be changed to the fuel pressure detection means;
A fuel injection control device. The fuel injection control device according to claim 2,
The control means includes
Before a specific period including a fuel injection period of a cylinder corresponding to the fuel pressure detection means arrives, a change range of the fuel pressure in the specific period is predicted, and the predicted change range is defined as the limited detection range. Transmitting the command information for the limited detection range to the fuel pressure detection means to detect the fuel pressure in the predicted change range in the specific period;
A fuel injection control device. The fuel injection control device according to claim 3, wherein
The control means includes
Detecting the fuel pressure in the basic detection range by transmitting command information for the basic detection range to the fuel pressure detection means when the specific period ends;
A fuel injection control device. In the fuel injection control device according to claim 3 or 4,
The control means predicts a change range of the fuel pressure in the specific period based on the fuel pressure detected before the specific period arrives;
A fuel injection control device. A fuel injection valve that injects fuel supplied from an accumulator that stores fuel pumped by a fuel pump from an injection port into a cylinder of an internal combustion engine;
Provided at a predetermined position in a fuel passage from a fuel outlet of the pressure accumulating container to an injection port of the fuel injection valve, and detecting a fuel pressure in the fuel passage that varies with fuel injection from the injection port to the cylinder; Fuel pressure detecting means for outputting a sensor signal having a voltage corresponding to the fuel pressure;
A fuel injection device comprising:
The fuel pressure detecting means includes
A communication means for communicating with a control device for controlling the fuel injection valve; a gain when the fuel pressure is converted into the sensor signal in the fuel pressure detection means; and the sensor signal output from the fuel pressure detection means. Output characteristic adjusting means for adjusting the offset potential, and when the command signal transmitted from the control device and representing each value of the gain and the offset potential is received by the communication means, Setting the gain and the offset potential to values represented by the received command information by the output characteristic adjusting means;
A fuel injection device characterized by the above. The fuel injection device according to claim 6, wherein
The fuel pressure detecting means is provided in the fuel injection valve;
A fuel injection device characterized by the above.

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