JPH0727012A - Sensor power supply fluctuation preventive device - Google Patents

Abstract

PURPOSE:To prevent the power supply fluctuation which occurs in case of using the watch dog power supply of a controller, which processes the signal of a combustion pressure sensor, etc., and the power supply of the combustion pressure sensor, etc., in common. CONSTITUTION:This is a power supply 44, which supplies a sensor 1 with constant voltage, and the sensor power supply fluctuation preventive device, which supplies constant voltage in common to a watch dog detecting the abnormality of a watch dog clear signal from a central processor 43 processing the output signal of the sensor 1 so as to control an engine but prevents the voltage fluctuation, is equipped with a WDC inversion inhibiter 60, which inhibits the inversion of the watch dog clear signal supplied to the watch dog, so this inhibits the inversion during the period when it converts the signal of the sensor 1 from analog to digital.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power source such as a combustion pressure sensor, and more particularly to a case where a watchdog power source of a control unit for processing a signal of the combustion pressure sensor and a power source of the combustion pressure sensor are commonly used. To prevent power fluctuations that occur in the

[0002]

2. Description of the Related Art Conventionally, as a technique in this field, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 113630 and Japanese Patent Application Laid-Open No. 1-290970 disclose the same. In the descriptions in these publications, the ECU
The (Electronic Control Unit) processes the signal of the combustion pressure sensor in order to control the operation of the engine.

[0003]

However, the engine operation control using the above combustion pressure sensor or the like has the following problems. FIG. 7 is an overall system diagram for realizing engine control using a combustion pressure sensor. The system shown in this figure includes a combustion pressure sensor 1 (CPS) attached to the upper cylinder of each cylinder in the engine,
The crank angle sensor 2 (rotation sensor) for obtaining information on the process of each cylinder and the engine rotation time, and further, necessary engine information is input from various sensors such as the pressure sensor 3 provided in each part of the engine to input the air-fuel ratio of the engine. An ECU 4 for controlling (A / F) and the like is provided.

FIG. 8 is a diagram showing a schematic configuration of the ECU 4 which processes the signal of the combustion pressure sensor of FIG. EC shown in this figure
U4 is a low-pass filter 41 for removing noise by inputting the signal from the combustion sensor 1, and the low-pass filter 4
A / D converter 42 (Analog to Digital Converter) connected to 1 and converting an analog signal into a digital signal
And a central processing unit 43 for controlling the air-fuel ratio (A / F) by inputting a digital signal from the A / D converter 42, and further, the combustion sensor 1, etc., the A / D converter 42, the central processing unit 43. , And a power source 44 (IC) for supplying a low voltage (5 V) to the IC. Further, the power supply 44 has an operation monitoring function of the central processing unit 43 as another function, and monitors a watchdog clear signal (WDC) output from the central processing unit 43, and resets the central processing unit 43 when an abnormality is detected. .

The ECU 4 has a method using the combustion pressure sensor 1 as one of the lean combustion methods. From the combustion pressure obtained from the output of the combustion sensor 1, the output torque generated by the combustion is estimated, The difference from the previous torque (torque fluctuation) is calculated for each cylinder, and when the decrease in this value is a predetermined value abnormality, it is judged as a lean misfire, and the fuel injection amount is increased to enrich the air-fuel ratio (A / F). When the amount is smaller than a predetermined value, the amount of fuel injection is reduced to control the A / F to the lean side so that the A / F is always near the lean limit. An actual control method will be described below (for convenience, one cylinder will be focused on and described.

FIG. 9 is a diagram for explaining the timing of converting the analog output signal from the combustion pressure sensor 1 into a digital signal, and FIG. 10 is a flowchart for explaining the interruption and completion of the A / D converter 42. The estimated “PT
In order to obtain “RQ”, the voltages at several representative points of the output signal of the combustion sensor 1 are A / D converted. First, as shown in FIG. 9, the A / D converter 42 is activated by the central processing unit 43 by the rotation pulse signal NE (for example, 10 ° CA (Crank-pin Angle) cycle) of the crank angle sensor 2. Next, as shown in FIG. 10, as an example, in steps S1 and S2, the A / D converter 42 is activated by the output voltage VCP0 of the combustion pressure sensor 1 near the bottom dead center.

At steps S3 and S4, the top dead center (Top
A at output voltage VCP1 of combustion pressure sensor 1 of Dead Center)
The / D converter 42 is activated. In the same manner, the interrupt is started with the output voltage VCP2 of the combustion pressure sensor 1 at 10 ° CA after the top dead center and the output voltage VCP3 of the combustion pressure sensor 1 at 20 ° CA after the top dead center. It

In step S5, the A / D converter 42
In the completion interrupt of, the conversion completion or non-completion of all four A / D converters 42 is checked. When the conversion is completed in step S6, the end flag is "XCYL =
It is set to 1 ”. Fig. 11 shows the estimated torque "PTRQ"
It is a flow chart explaining the procedure of obtaining. The actual lean burn control is performed at the base timing so as to control the A / F and the like. As shown in the figure, in step S10, it is determined whether or not the end flag "XCYL = 1" is satisfied.

In step S11, the above judgment is "Y.
If "ES", that is, if the A / D conversion of all the four points is completed, the end flag is set to "XCYL = 0". In step S12, first, the combustion pressure CP1 at each point,
CP1 and CP3 are obtained as follows. CPn =
k1 * (VCPn-VCP0), where n = 1,2,3, k1: VCP
It is a conversion coefficient from n to CPn. Next CP1
The estimated torque "PTRQ" is obtained from CP1 and CP3 as follows.

PTRQ = k2 * CP1 + k3 * CP2 + k4
* CP3, where k2, k3, k4: CPn to PTR
It is a Q conversion coefficient. In step S13, the torque decrease amount DTRQ is obtained from the difference between PTQRs of this time and the previous time as follows. DTRQ = PTRQn-PTRQn-1 D obtained in this way in step S14
Lean TRQ Lean misfire torque level LVLTR
In order to compare with Q, it is determined whether DTRQ ≧ LVLTRQ is satisfied.

In step S15, the above "YES"
If it is determined that the fuel injection amount is increased, the fuel injection amount is increased. Step S
If the determination is "NO" at 16, the fuel injection amount is reduced. If “NO” is determined in step S10,
This base timing process is not performed.

FIG. 12 is a diagram showing the configuration of the power supply 44 of FIG. The power supply 44 shown in the figure is a series regulator type, operates as a variable impedance, forms a constant voltage (Vcc) from the battery voltage (+ B), and the sensor 1 and the like.
A transistor 51 that supplies this constant voltage to the A / D converter 42, the central processing unit 43, etc., a voltage dividing circuit 52 connected to the output of the transistor 51, and the output of the voltage dividing circuit 52 and the reference voltage are compared. The error amplifier 53 that feeds back the error signal to the base of the transistor 51, and the central processing unit 43 when power is supplied from the output of the transistor 51 and the watchdog clear signal from the central processing unit 43 is input and the clear signal is no longer transmitted. And a watchdog section 54 which outputs a reset (initial) signal to inform the central processing unit 43 that an abnormality has occurred.

FIG. 13 is a time chart for explaining the operation of the watch dock section 54 of FIG. As shown in the figure, the watchdog unit 54 monitors the watchdog clear signal of the central processing unit 43, and while the watchdog clear signal continues to invert, the central processing unit 43 receives "H (high)".
Signal is output, and the reset signal (iNi
Repeatedly apply "L (low)" to the T terminal. This fixed time tks is a period longer than the cycle of the watchdog signal.

FIG. 14 is a time chart for explaining the fluctuation which affects the power supply voltage Vcc by the watchdog clear signal. This figure shows the relationship between the power supply voltage Vcc (5v) supplied to the combustion sensor 1 and the watchdog clear signal described above. As shown in this figure, the power supply voltage is synchronized with "L" of the watchdog clear. Ripple occurs in Vcc.
This is because the voltage dividing resistors R1 and R2 for detecting Vcc inside the power supply 44 (IC) and the common impedance r of the aluminum wiring to the watchdog section 54 exist, and the current I1 flowing through the watchdog section 54 causes the impedance. The voltage drop I1 × r at the common impedance r appears as a ripple in the power supply voltage Vcc. The error due to this ripple is amplified by the combustion sensor 1 and reflected in the calculation in the central processing unit 43. Therefore, the lean limit may be erroneously determined in the air-fuel ratio (A / F) control, which may cause deterioration of drivability and emission.

Therefore, in view of the above problems, it is an object of the present invention to provide a sensor power supply fluctuation preventing device capable of preventing a lip fluctuation generated in a power supply by a watchdog clear signal.

[0016]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a power source for supplying a constant voltage to a sensor, which processes an output signal of the sensor to control an engine. A sensor power supply fluctuation prevention device that prevents voltage fluctuations of the watchdog that commonly supplies the constant voltage to the watchdog that detects an abnormality in the watchdog clear signal, but reverses the watchdog clear signal that is supplied to the watchdog. A WDC inversion prohibition unit is provided that prohibits only during the period in which the signal is converted from analog to digital.

[0017]

According to the sensor power supply fluctuation prevention device of the present invention, W
Since the inversion is prohibited by the DC inversion prohibiting unit only during the period in which the sensor signal is converted from analog to digital, the power supply voltage Vcc is synchronized with the watchdog clear signal.
It is possible to prevent the ripple that has been conventionally generated from occurring. The watchdog clear signal is inverted except during the conversion period, and since the inversion is interrupted only for an extremely short time during the conversion period, the function of the watchdog is not impaired. Further, the watchdog clear signal of each of the plurality of central processing units is logically ANDed with the in-conversion signal generated during the conversion of the sensor from analog to digital to form the inversion prohibition of the watchdog clear signal. Accordingly, it is possible to prevent ripple from occurring in the power supply voltage Vcc in synchronization with the watchdog clear signal.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a sensor power supply fluctuation prevention device according to an embodiment of the present invention. The central processing unit 4 of this figure differs from that of FIG. 11 in the WDC inversion prohibition unit 60 provided in the central processing unit 43. While the A / D converter 42 is A / D converting the output signal of the combustion sensor 1, the WDC inversion prohibiting unit 60 prohibits the inversion of the watchdog clear signal in the central processing unit 43. Next, the operation of the WDC inversion prohibition unit 60 will be described in detail.

FIG. 2 is a flow chart for explaining the operation of the WDC inversion prohibition unit 60 of FIG. Step S2 in this figure
At 0, it is judged whether it is the A / D conversion timing of VCP0 which is the output signal of the combustion sensor 1 in response to the NE interrupt of the crank angle sensor 2. If the determination is "YES" in step S21, the WDC inversion prohibition unit 60 sets the inversion prohibition flag to "XiWAC = 1".

In step S22, the A / D converter 4
2, VCP0 is A / D converted. After completion of this conversion, the process proceeds to step S28. In step S23, it is determined whether it is the A / D conversion timing of VCP1 which is the output signal of the combustion sensor 1. In step S24, the above "YE
If the determination is “S”, the WDC inversion prohibition unit 60 sets the inversion prohibition flag to “XiWDC = 1”.

In step S25, the A / D converter 4
2, VCP0 is A / D converted. After completion of this conversion, the process proceeds to step S28. Similarly, VCP2 and VCP3
Then, the WDC inversion prohibition unit 60 sets the inversion prohibition flag to "XiWDC = 1" during the A / D conversion. After those conversions are completed, the process proceeds to step S28. In step S26, it is determined that all A / D conversions have been completed. "NO"
If so, the process proceeds to step S28.

In step S27, the above "YES"
If YES, the flag XCYL is set to "XCYL = 1" so that the process for obtaining the estimated torque "PTRQ" in FIG. 11 is performed. In step 28, the flag XiWDC is set in the end interrupt of each A / D conversion.
Is cleared (as “XiWDC = 0”), the WDC inversion prohibition unit 60 cancels the WDC inversion prohibition, and the next A /
Wait for D conversion timing. The reversal prohibition time interval is adjusted to be smaller than the constant time tks described with reference to FIG. This is because if it exceeds this, it is determined that the CPU is abnormal.

FIG. 3 shows the WDC by the inversion prohibition flag of FIG.
It is a figure explaining inversion control. As shown in this figure, WD
In the C inversion prohibition unit 60, the inversion prohibition flag is set to "XiWDC" in step S30 by the 4 ms timer interrupt.
= 1 ”is determined. If this determination is "YES", the inversion of WDC in the following step 32 is skipped. In step S31, if the determination is "YES", it is determined whether the base circuit is normal for other processing. This judgment is "N
If it is "O", the inversion of WDC in the following step 32 is skipped.

In step S32, the above "YES"
If it is determined to be true, WDC is inverted. In this way, the inversion prohibition flag (XiWDC) is checked before the WDC inversion process, and if “XiWDC = 1”, the inversion process is prohibited by the WDC inversion skip. FIG. 4 is a diagram for explaining the relationship between the WDC and the CPS output signal when the inversion is prohibited. As shown in the figure, the WDC conversion is prohibited during the A / D conversion of the CPS output signal, so that the current flowing through the watchdog portion 54 is blocked. Therefore, power supply 4
The ripple of the power supply voltage Vcc of No. 4 can be removed, the accuracy of lean burn control can be improved relatively easily, and the above-mentioned problems can be solved. In the above embodiment, the output of WDC,
Although the case where the A / D conversion of the CPS output signal is processed by the same CPU has been described, the case where it is processed by another CPU will be described below.

FIG. 5 is a diagram for explaining another sensor power supply fluctuation preventing device according to the embodiment of the present invention, and FIG. 6 is a diagram showing the relationship between the WDC of the main CPU 45 and the iWDC of the sub CPU 46 of FIG. . 5, what is different from FIG. 1 is a main CPU 45, a sub CPU 46, and OR circuits 47 and 48. Although not shown, the power supply unit 44
Is provided with watchdog parts 54-1 and 54-2 for the main CPU 45 and the sub CPU 46. Those outputs are connected to the reset section of the main CPU 45 and the sub CPU 46. As shown in FIG. 6, the main CPU
45 performs other processing and forms WDC, and the A / D converter 42 outputs the "H (high)" signal as the in-conversion signal (iWDC) during the A / D conversion of the CPS output signal. The logical sum circuit 47 causes the WDC of the main CPU 45 and A
The inversion prohibition signal WDL that is in the "H" state is compulsorily taken during the conversion by taking the logical sum of the in-conversion signal from the / D converter 42.
0 is formed. The inversion prohibition signal WDL0 is supplied to the power source 44.
Is output to the watch dock 54-1. Similarly, the logical sum circuit 48 calculates the logical sum of the WDC of the sub CPU 46 and the in-conversion signal from the A / D converter 42, and forcibly outputs the inversion prohibition signal WDL1 in the "H" state during conversion. It is formed. The inversion prohibition signal WDL1 is output to the watchdog 54-2 of the power supply 44. In this way the CPU
The watchdog clear signal for detecting an abnormality from 45 and 46 prevents the power supply voltage of the sensor from changing during A / D conversion. Although the CPS sensor has been mainly described above, the present invention can be applied to other sensors (such as an air flow meter) that are similarly supplied with power from the ECU 4 to improve the accuracy.

[0026]

As described above, according to the present invention, inversion of the watchdog clear signal is prohibited only during the period in which the sensor signal is converted from analog to digital, so that the power supply voltage is synchronized with the watchdog clear. It is possible to prevent the generation of ripple that has occurred in Vcc. Further, the watchdog clear signal of each of the plurality of central processing units is logically ANDed with the in-conversion signal generated during the conversion of the sensor from analog to digital to form the inversion prohibition of the watchdog clear signal. Accordingly, it is possible to prevent ripple from occurring in the power supply voltage Vcc in synchronization with the watchdog clear signal.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a sensor power supply fluctuation prevention device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of a WDC inversion prohibition unit 60 of FIG.

FIG. 3 is a flowchart illustrating WDC inversion control by the inversion prohibition flag in FIG.

FIG. 4 is a diagram illustrating a relationship between a WDC and a CPS output signal when inversion is prohibited.

FIG. 5 is a diagram illustrating another sensor power supply fluctuation prevention device according to an embodiment of the present invention.

6 is a diagram illustrating a relationship between WDC of the main CPU 45 and iWDC of the A / D converter 42 in FIG.

7 is an overall system diagram for realizing engine control using the combustion pressure sensor 1. FIG.

FIG. 8 is an ECU that processes signals from the combustion pressure sensor 1 of FIG.
It is a figure which shows schematic structure of 4.

FIG. 9 is a diagram illustrating the timing of converting an analog output signal from the combustion pressure sensor 1 into a digital signal.

FIG. 10 is a flowchart illustrating interrupt activation and completion of the A / D converter 42.

FIG. 11 is a flowchart illustrating a procedure for obtaining an estimated torque “PTRQ”.

12 is a diagram showing a configuration of a power supply 44 of FIG.

13 is a time chart explaining the operation of the watch dock section 54 in FIG.

FIG. 14 is a voltage power supply V according to a watchdog clear signal.
It is a time chart explaining the fluctuation which affects cc.

[Explanation of symbols]

 1 ... Combustion sensor 2 ... Crank angle sensor 4 ... ECU 42 ... A / D converter 43, 45, 46 ... Central processing unit 44 ... Power supply 47, 48 ... OR circuit 51 ... Transistor 52 ... Voltage dividing circuit 53 ... Error amplifier 54 ... Watchdog section 60 ... WDC inversion prohibition section

Claims (2)

[Claims] 1. A watchdog clear signal from a central processing unit (43), which is a power supply (44) for supplying a constant voltage to the sensor (1) and processes an output signal of the sensor (1) to control an engine. Is a sensor power supply fluctuation preventing device that supplies a fixed voltage in common to a watchdog that detects an abnormality of the watchdog, and that prevents the watchdog clear signal supplied to the watchdog from being inverted. A part (60),
A sensor power supply fluctuation prevention device characterized in that the inversion is prohibited during a period in which a signal of the sensor (1) is converted from analog to digital. 2. The logical product of the watchdog clear signals of the plurality of central processing units (45, 46) and the in-conversion signal generated during the conversion of the sensor (1) from analog to digital. 2. The sensor power supply fluctuation prevention device according to claim 1, wherein an inversion prohibition of a take-watch dock clear signal is formed.