JP2002276441A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly perform a fail-safe processing even when fuel pressure detected by a plurality of fuel pressure sensors belongs to a normal possible range and a deviation of fuel pressure by two prescribed fuel pressure sensors is smaller than a prescribed decision value. SOLUTION: The device is provided with the plurality of fuel pressure sensors 44 and 45 for detecting each pressure of fuel within a common-rail 25 and an electronic control unit(ECU) 46. When each detected value of the two prescribed fuel pressure sensor 44 and 45 belongs to the normal possible range and the deviation of both detected values is smaller than the prescribed decision value, the ECU 46 sets the detected higher value as fuel pressure. The ECU 46 determines an injection period based on fuel injection quantity according to an operation state of an engine 11 and the fuel pressure, and controls a fuel injection valve 23 so as to inject fuel over the injection period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine for distributing pressurized fuel to a plurality of fuel injection valves by a fuel distribution pipe and injecting the fuel to the fuel injection pipe. The present invention relates to a fuel injection control device that controls at least one of a fuel injection amount and an injection pressure based on the detected values.

[0002]

2. Description of the Related Art A fuel pump compresses fuel to a high pressure, distributes the fuel from a common rail which is a fuel distribution pipe to fuel injection valves of each cylinder, and injects fuel by opening the fuel injection valves. Such a diesel engine is known. As one of the fuel injection control techniques for this engine, the pressure of the fuel in the common rail is detected by a single fuel pressure sensor, and the fuel injection amount and injection pressure from the fuel injection valve are controlled based on the detected value. There is something to do.

In the above fuel injection control, if the detected value of the fuel pressure sensor is out of the normal range, it can be understood that the fuel pressure sensor is abnormal. Accordingly, in this case, it is possible to perform an appropriate fail process in the fuel injection amount control and the injection pressure control. However, when a characteristic abnormality has occurred in the fuel pressure sensor, it is difficult to detect and deal with the abnormality. The characteristic abnormality is a phenomenon in which the detection value of the fuel pressure sensor belongs to a range that can be normally taken, but is different from the output characteristic in a normal state. For example, in the case of a fuel pressure sensor that outputs a voltage proportional to pressure, the slope of the characteristic is the same as the normal slope, but it is deviated or the slope of the characteristic is different from the normal slope. It is. In this case, it is difficult to distinguish between normal and abnormal characteristics.

Therefore, a technique has been proposed in which a plurality of fuel pressure sensors detect the pressure of the fuel in the common rail, and a characteristic abnormality of the fuel pressure sensor is detected using the detected values (for example, Japanese Patent Application Laid-Open No. HEI 9-26138). 8-61133). In this technique, if all the fuel pressure sensors are normal, their detection values (fuel pressures) are substantially the same. Therefore, the deviation of the detection values (fuel pressures) of two predetermined fuel pressure sensors Is larger than a predetermined determination value, it is determined that one of the fuel pressure sensors has abnormal characteristics.

[0005]

However, even if each fuel pressure sensor is normal, there is a considerable variation in its output characteristics. Therefore, the above-described determination is made using a determination value in which the variation is considered. If not, the deviation of the fuel pressure becomes larger than the determination value, and the normal fuel pressure sensor is erroneously detected as a characteristic abnormality. Therefore, in order to prevent erroneous detection due to this variation, a somewhat large determination value is set. In this case, when the deviation of the detected value is remarkably large, it is possible to detect that one of the fuel pressure sensors has an apparent characteristic abnormality and that abnormality is detected.

However, even if the deviation is small, not all the fuel pressure sensors are necessarily normal. Although it is not clear, the possibility remains that one of the fuel pressure sensors has abnormal characteristics. In this case, the deviation becomes smaller than the determination value, and the characteristic abnormality may not be detected. Thus, when the deviation is smaller than the determination value,
Since the presence or absence of the characteristic abnormality is not clear, there is a problem that it is difficult to perform an appropriate fail-safe process in the fuel injection amount control and the injection pressure control.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose that the fuel pressures detected by a plurality of fuel pressure sensors belong to a range which can be normally taken and two predetermined fuel pressures are provided. An object of the present invention is to provide a fuel injection control device capable of appropriately performing a fail-safe process even when a deviation of a fuel pressure by a sensor is smaller than a predetermined determination value.

[0008]

The means for achieving the above object and the effects thereof will be described below. In the invention according to claim 1, a plurality of fuel pressure sensors are provided in a fuel distribution pipe for distributing pressurized fuel to a plurality of fuel injection valves of an engine, and each detect a pressure of the fuel in the fuel distribution pipe, A fuel pressure setting unit for setting a fuel pressure used as a control parameter based on a detection value of each fuel pressure sensor; a fuel injection amount according to an operation state of the engine; and a fuel pressure by the fuel pressure setting unit. A fuel injection control device for determining an injection period and controlling the fuel injection valve so that fuel is injected over the injection period. If each of the detected values falls within a range that can be normally taken, and the deviation between the two detected values is smaller than a predetermined determination value, the higher detected value is determined by the fuel injection control unit. And it is set as the said fuel pressure for between calculation.

According to the above configuration, the pressure of the fuel in the fuel distribution pipe is detected by the plurality of fuel pressure sensors. If both of the predetermined two fuel pressure sensors are normal,
Their detection values should be approximately the same. The fuel pressure setting means sets the fuel pressure based on the detected value of each fuel pressure sensor. In the fuel injection control means, an injection period is obtained based on the fuel injection amount according to the operating state of the engine and the fuel pressure. When the fuel injection amount is the same, the injection period becomes shorter as the fuel pressure becomes higher. Further, the fuel injection control means controls the fuel injection valve so that fuel is injected over the injection period.

Here, of the two fuel pressure sensors, the higher detected value is supposed to be correct and the lower detected value is incorrect, and the latter detected value is set as fuel pressure by the fuel pressure setting means. In this case, the injection period determined from the fuel injection amount and the fuel pressure becomes longer than the original injection period. Therefore, when fuel is injected over a set period, a larger amount of fuel is injected than is originally required.

Conversely, if the higher detection value is incorrect, the lower detection value is correct, and the former detection value is set as the fuel pressure by the fuel pressure setting means, the fuel injection amount and the fuel The injection period determined from the pressure is shorter than the original injection period. Therefore, when fuel is injected over a set period, a smaller amount of fuel is injected than is originally required.

On the other hand, according to the first aspect of the present invention, when the respective detected values of the two predetermined fuel pressure sensors belong to a normal range, and the deviation between the two detected values is smaller than the predetermined determination value. Although it is not as clear as when the deviation is equal to or larger than the determination value, it is determined that there is a possibility that one of the fuel pressure sensors has abnormal characteristics, and the higher detection value is set as the fuel pressure. Therefore, by performing an appropriate fail-safe process of using the fuel pressure set in this manner for controlling the fuel injection valve, it is possible to suppress the injection of an excessive amount of fuel.

According to the second aspect of the present invention, the fuel distribution pipe is provided for distributing the pressurized fuel supplied from the fuel pump to the plurality of fuel injection valves of the engine, and detects the pressure of the fuel in the fuel distribution pipe. A plurality of fuel pressure sensors, and fuel pressure setting means for setting a fuel pressure used as a control parameter based on a detection value of each fuel pressure sensor,
A fuel injection control device that controls the fuel pump so that the fuel pressure by the fuel pressure setting device converges to a target pressure corresponding to the operating state of the engine. If the detected values of the two predetermined fuel pressure sensors belong to a range that can be normally taken, and the difference between the two detected values is smaller than a predetermined determination value, the higher detected value is determined by the fuel injection control means. It is assumed that the fuel pressure is set as the fuel pressure for controlling the fuel pump.

According to the above configuration, the pressure of the fuel supplied from the fuel pump to the fuel distribution pipe is detected by the plurality of fuel pressure sensors. If the two predetermined fuel pressure sensors are both normal, their detection values should be substantially the same. The fuel pressure setting means sets a fuel pressure based on a detection value of each of the fuel pressure sensors. The fuel injection control means controls the fuel pump such that the fuel pressure set by the fuel pressure setting means converges to a target pressure according to the operating state of the engine.

Here, if the higher detected value of the two fuel pressure sensors is correct and the lower detected value is incorrect, the latter detected value is determined by the fuel pressure setting means. When the pressure is set as the pressure, the deviation between the target pressure and the fuel pressure becomes larger than the original deviation, and the control amount required to converge the fuel pressure to the target pressure is the original control amount (the former detection value is Control amount required when the fuel pressure is set). For this reason, the pressure of the fuel supplied from the fuel pump, and eventually the pressure of the fuel in the fuel distribution pipe, becomes higher than it should be.

Contrary to the above, when the higher detection value is incorrect and the lower detection value is correct, and the former detection value is set as fuel pressure by the fuel pressure setting means, the target pressure And the difference between the fuel pressure and the original difference,
The control amount required to converge the fuel pressure to the target pressure is smaller than the original control amount (the control amount required when the latter detected value is set as the fuel pressure). Therefore, the pressure of the fuel in the fuel distribution pipe becomes lower than it should be.

On the other hand, according to the second aspect of the present invention, when the respective detected values of the two predetermined fuel pressure sensors belong to the range which can be normally taken, and the deviation between the two detected values is smaller than the predetermined judgment value. Although it is not as clear as when the deviation is equal to or larger than the determination value, it is determined that there is a possibility that one of the fuel pressure sensors has abnormal characteristics, and the higher detection value is set as the fuel pressure. Therefore, by performing an appropriate fail-safe process in which the fuel pressure set in this manner is used for controlling the fuel pump, it is possible to suppress an excessive increase in the pressure of the fuel in the fuel distribution pipe.

According to the third aspect of the present invention, the first or second aspect is provided.
In the invention described in the above, the fuel pressure setting means is provided with a predetermined 2
When only one of the detected values of the fuel pressure sensors is out of the range, the detected value of the other fuel pressure sensor is set as the fuel pressure.

Here, when the detected value of one of the fuel pressure sensors is out of the normal range, it is apparent that the detected value is abnormal. If the detected value of the other fuel pressure sensor belongs to the same range, the detected value is not a clear abnormality. In addition, it is very unlikely that both fuel pressure sensors will both fail at once. From this, the latter (the other) detection value can be considered normal.

In view of the above, in the fuel pressure setting means, when the detection value of one of the fuel pressure sensors is out of the normal range and the detection value of the other fuel pressure sensor belongs to the same range, the latter (the other The value detected by the fuel pressure sensor in (2) is set as the fuel pressure, and is used for control by the fuel injection control means.

Therefore, it is possible to prevent a problem caused by the detection value of the former (one) fuel pressure sensor, which is considered to be an obvious abnormality, being used for the control. By using the latter (other) detection value considered to be normal, control can be properly performed.

According to the invention described in claim 4, claim 1 or 2
Wherein the fuel pressure setting means sets a value corresponding to the operating state of the engine as the fuel pressure when both detected values of two predetermined fuel pressure sensors are out of the range. And

According to the above configuration, when the detected values of both fuel pressure sensors are out of the normal range, it is apparent that both detected values are abnormal. For this reason, in the fuel pressure setting means, a value determined based on the operating state of the engine at that time is set as the fuel pressure instead of the detection values of both fuel pressure sensors, and is used for control by the fuel injection control means. Can be

Therefore, it is possible to prevent a problem caused by the detection values of both the fuel pressure sensors, which are considered to be obvious abnormalities, being used for the control. By using a value corresponding to the operating state of the engine at that time, control can be properly continued.

According to the invention of claim 5, claim 1 or 2
In the invention described in the above, the fuel pressure setting means, when both detected values of the predetermined two fuel pressure sensors belong to the range, and a deviation between both detected values is equal to or more than the determination value, the operating state of the engine Is set as the fuel pressure.

According to the above arrangement, when each of the detected values of the two fuel pressure sensors belongs to a range which can be normally taken, and the deviation between the two detected values is equal to or larger than a predetermined determination value, Is clearly considered to be a characteristic abnormality. However, it is unclear which is the characteristic abnormality. For this reason, in the fuel pressure setting means, a value determined based on the operating state of the engine at that time is set as the fuel pressure instead of the detection values of both fuel pressure sensors, and is used for control by the fuel injection control means. Can be

Therefore, the detected value of the fuel pressure sensor suspected of being abnormal is used for the control, and an excessive amount of fuel is injected from the fuel injection valve, or the pressure of the fuel in the fuel distribution pipe rises excessively. Can be suppressed. By using a value corresponding to the operating state of the engine at that time, control can be properly continued.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a fuel injection control device according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the vehicle is equipped with an accumulator-type diesel engine (hereinafter simply referred to as an engine) 11. The engine 11 includes a cylinder head 12
And a cylinder block 14 having a plurality of cylinders (cylinders) 13. A piston 15 is accommodated in each cylinder 13 so as to be able to reciprocate. Each piston 15
Is connected via a connecting rod 16 to a crankshaft (not shown), which is the output shaft of the engine 11. The reciprocating motion of each piston 15 is converted into a rotary motion by a connecting rod 16 and then transmitted to a crankshaft.

The combustion chamber of each cylinder 13 has an intake passage 18
Is connected, and air outside the engine 11 is taken into the combustion chamber through the intake passage 18. An exhaust passage 19 is connected to the combustion chamber. The cylinder head 12 is provided with an intake valve 21 and an exhaust valve 22 for each cylinder 13. These intake / exhaust valves 21 and 22 reciprocate in conjunction with the rotation of the crankshaft, thereby providing intake / exhaust valves.
The connection between the exhaust passages 18, 19 and the combustion chamber is opened and closed.

The cylinder head 12 has a fuel injection valve (injector) for injecting fuel into a combustion chamber of each cylinder 13.
23 are attached. Fuel injection from each fuel injection valve 23 to the corresponding combustion chamber is controlled by a solenoid valve 24. The fuel injection valve 23 is connected to a common rail 25 which is a fuel distribution pipe. While the solenoid valve 24 is open, fuel in the common rail 25 is injected from the fuel injection valve 23 to a corresponding combustion chamber. A relatively high pressure corresponding to the fuel injection pressure is accumulated in the common rail 25. In order to realize this pressure, the common rail 25 is connected to a discharge port 28 of a supply pump 27 via a supply pipe 26.

The suction port 31 of the supply pump 27
It is connected to a fuel tank 33 via a filter 32. The supply pump 27 draws fuel from the fuel tank 33 via the filter 32. Also, with this,
The supply pump 27 reciprocates the plunger by a cam (not shown) synchronized with the rotation of the engine 11 to supply fuel to the common rail 25 at a predetermined pressure.

In the vicinity of the discharge port 28 of the supply pump 27, a pressure control valve 34 for controlling the pressure of fuel discharged from the discharge port 28 toward the common rail 25, and furthermore, the discharge amount is provided. When the pressure control valve 34 is opened, surplus fuel not discharged from the discharge port 28 is returned from the return port 35 of the supply pump 27 to the fuel tank 33 via the return pipe 36.

The common rail 25 is provided with a relief valve 37 that opens when a predetermined condition is satisfied. By opening the relief valve 37, the common rail 2
5 is returned to the fuel tank 33 through the return pipe 38, and the pressure in the common rail 25 is reduced.

Then, the cylinder 1 passes through the intake passage 18.
Fuel is injected from the fuel injection valve 23 into the high-temperature and high-pressure intake air introduced into the fuel cell 3 and compressed by the piston 15. This injected fuel self-ignites and burns.
The piston 15 is reciprocated by the combustion gas generated at this time, and the crankshaft is rotated, so that the driving force (output torque) of the engine 11 is obtained. The combustion gas is supplied to the exhaust passage 19.
Through the engine 11.

Various sensors such as a water temperature sensor 41, a rotational speed sensor 42, an accelerator sensor 43, and a plurality of fuel pressure sensors are used to detect the operating state of the engine 11. The water temperature sensor 41 is attached to the cylinder block 14 and detects the temperature of the cooling water flowing through the water jacket 14a. Rotation speed sensor 42
Is disposed near the crankshaft, and detects the engine speed, which is the number of revolutions of the crankshaft per hour. The accelerator sensor 43 detects the accelerator opening, which is the amount of depression of the accelerator pedal 39 by the driver.

A plurality of fuel pressure sensors are mounted on the common rail 25 and detect the fuel pressure in the common rail 25. In the present embodiment, a first fuel pressure sensor 44 and a second fuel pressure sensor 45 are used as the plurality of fuel pressure sensors. Both fuel pressure sensors 44 and 45 output voltages (analog values) proportional to the fuel pressure.

FIG. 2 shows the characteristics of the voltage VPC output from the two fuel pressure sensors 44 and 45. In the figure, the region lower than the lower limit value VMIN indicated by the broken line and the region higher than the upper limit value VMAX also indicated by the broken line correspond to the fuel pressure sensor 4.
Areas 4 and 45 cannot be taken if they are normal. Voltage V
When the PC belongs to the former area (VPC <VMI
N), there is a high possibility that the fuel pressure sensors 44 and 45 are disconnected. When the voltage VPC belongs to the latter region (VPC> VMAX), there is a high possibility that the fuel pressure sensors 44 and 45 are short-circuited. In other words, VMIN ≦
The range indicated by VPC ≦ VMAX is a range that the normal fuel pressure sensors 44 and 45 can normally take.

A characteristic line L1 indicated by a solid line indicates the characteristic of the voltage output from the normal first fuel pressure sensor 44.
A characteristic line L2 indicated by a solid line is a normal second fuel pressure sensor 45.
5 shows the characteristics of the voltage output from. Both characteristic lines L
At 1 and L2, the voltage increases in proportion to the increase in the pressure (fuel pressure) within the above-mentioned normal range. In addition,
The two characteristic lines L1 and L2 do not match, and the voltage differs by the predetermined amount ΔV with respect to the same pressure over the entire range of the pressure.

Further, in FIG. 2, a region sandwiched between two dashed lines is a range R in which the voltage output from the normal first fuel pressure sensor 44 varies around the characteristic line L1.
1 is shown. Similarly, a region sandwiched between the two dashed lines is a range R2 in which the voltage output from the normal second fuel pressure sensor 45 varies around the characteristic line L2.
Is shown.

When a characteristic abnormality occurs in the first fuel pressure sensor 44, the voltage output from the sensor 44 is in the range R
Deviate from 1. Further, when a characteristic abnormality occurs in the second fuel pressure sensor 45, the voltage output from the sensor 45 falls outside the range R2.

As shown in FIG. 1, the various sensors 41 to
In order to control each part of the engine 11 based on the detected value of the 45, an electronic control unit (Electronic Control Uni
t: ECU) 46 is provided. The ECU 46 is mainly composed of a microcomputer. A central processing unit (CPU) performs arithmetic processing according to a control program, initial data, a control map, and the like stored in a read-only memory (ROM). Various controls are executed based on the control. The calculation result by the CPU is temporarily stored in a random access memory (RAM). Further, the ECU 46 includes an A / D converter 47 for converting voltages (analog values) output from the fuel pressure sensors 44 and 45 into digital values. The various controls include fuel pressure setting, fuel injection amount control, and injection pressure control.

When setting the fuel pressure, the ECU 46 repeatedly executes a "fuel pressure setting routine" shown in FIGS. 3 and 4 at a predetermined timing, for example, at predetermined time intervals. EC
U46 first performs an A / D conversion of the output voltage of the first fuel pressure sensor 44 in step S100, so that A
/ D conversion value VPC1 is obtained. In step S105, the output voltage of the second fuel pressure sensor 45 is subjected to A / D conversion to obtain an A / D conversion value VPC2.

Next, in step S110, the first fuel pressure PCR1 is calculated according to the following (Equation 1), and the second fuel pressure PCR2 is calculated according to the following (Equation 2). (Equation 1) expresses the A / D conversion value VPC1 as the first fuel pressure PC.
R1 is a conversion formula, and (Formula 2) is A / D
It is a conversion formula for converting the conversion value VPC2 into the second fuel pressure PCR2 (= PCR1). A and B in (Equation 1) and C and D in (Equation 2) are both constant values. According to these (Equation 1) and (Equation 2), both fuel pressure sensors 4
When the pressures 4 and 45 are normal, the fuel pressures PCR1 and PCR2 have substantially the same value.

PCR1 = VPC1 · A + B (Equation 1) PCR2 = VPC2 · C + D (Equation 2) Subsequently, in step S115, the first fuel pressure PCR
It is determined whether only 1 is abnormal. For details,
The range in which the fuel pressure PCR1 can normally take (MIN1 to MA
X1) and the second fuel pressure PCR
Then, it is determined whether or not the condition that 2 belongs to the range (MIN2 to MAX2) that can be normally taken is satisfied. Here, the lower limit values MIN1 and MIN2 correspond to the lower limit value VMIN in FIG. 2, and the upper limit values MAX1 and MAX2 correspond to those in FIG.
Corresponds to the upper limit value VMAX.

When the determination condition in step S115 is satisfied, the first fuel pressure PCR1 is set in the range (MIN).
1 to MAX1), it is apparently abnormal. Further, since the second fuel pressure PCR2 belongs to the above range (MIN2 to MAX2), it cannot be said that it is a clear abnormality. In addition, it is very unlikely that both fuel pressure sensors 44, 45 will both fail at once. From this, it can be considered that the second fuel pressure PCR2 is normal. Therefore, in step S120, the second fuel pressure PCR2 is set as the final fuel pressure PCR, and thereafter, this routine ends.

If the determination condition in step S115 is not satisfied, it is determined in step S125 whether only the second fuel pressure PCR2 is abnormal. Specifically, the first fuel pressure PCR1 is set in the range (MIN1 to MAX).
It is determined whether both the condition that the first fuel pressure belongs to 1) and the condition that the second fuel pressure PCR2 is out of the range (MIN2 to MAX2) are satisfied.

When the determination condition in step S125 is satisfied, the second fuel pressure PCR2 is set in the range (MIN).
2-MAX2), it is apparently abnormal. Also, since the first fuel pressure PCR1 belongs to the above range (MIN1 to MAX1), it cannot be said that it is a clear abnormality. In addition, it is very unlikely that the two fuel pressure sensors 44, 45 will both fail at once. From this, it can be considered that the first fuel pressure PCR1 is normal. Therefore, in step S130, the first fuel pressure PCR1 is set as the final fuel pressure PCR, and then this routine ends.

If the determination condition in step S125 is not satisfied, the first step is executed in step S135 in FIG.
It is determined whether both the fuel pressure PCR1 and the second fuel pressure PCR2 are abnormal. Specifically, the first fuel pressure PCR
1 is outside the range (MIN1 to MAX1) and the second fuel pressure PCR2 is within the range (MIN2).
... MAX2) are determined.

When the determination condition of step S135 is satisfied, it is clear that both the fuel pressures PCR1 and PCR2 are abnormal. From this, step S14
At 0, the target pressure determined based on the operating state of the engine 11 at that time is set as the final fuel pressure PCR instead of both the fuel pressures PCR1 and PCR2, and then this routine is terminated. If the determination condition in step S135 is not satisfied, it is determined in step S145 whether the absolute value of the difference ΔPCR between the two fuel pressures PCR1 and PCR2 is equal to or greater than a predetermined determination value X. The determination value X is based on the above-described variation of the first fuel pressure PCR1 and the second fuel pressure P1.
It is determined in consideration of the variation of CR2, that is, in consideration of the ranges R1 and R2 in FIG.

Here, the processing in step S145 is for judging the degree of abnormality when one of the two fuel pressure sensors 44, 45 has abnormal characteristics.
That is, the first fuel pressure PCR1 and the second fuel pressure PCR2
Are greatly different from each other, it is considered that either one of the fuel pressure sensors 44 (or 45) clearly has abnormal characteristics. On the other hand, each fuel pressure PCR1, PC
When R2 is close, although not as obvious as described above, one of the fuel pressure sensors 44 (or 4
The possibility that 5) is abnormal in characteristics remains.

Therefore, the absolute value of the deviation ΔPCR is determined by the determination value X
It is determined whether or not it is more than the determination value. If the value is equal to or more than the determination value, it is determined that the characteristic is abnormal. If the value is smaller than the determination value X, it is not obvious but the possibility of the characteristic abnormality remains. I judge.

If the determination condition of step S145 is satisfied, the routine ends after the processing of step S140 described above. On the other hand, step S1
If the determination condition of No. 45 is not satisfied, step S15
At 0, the higher value of the two fuel pressures PCR1 and PCR2 is set as the final fuel pressure PCR, and then this routine ends.

The final fuel pressure PCR set on the basis of the detection values of the fuel pressure sensors 44 and 45 is used as a control parameter for calculating the fuel injection amount and injection pressure. Next, regarding the “injection amount control routine” and the “injection pressure control routine” executed by the ECU 46,
This will be described with reference to FIGS.

FIG. 5 shows a routine for setting the injection period in the injection amount control routine. In this injection period setting routine, the ECU 46 first determines in step S2
At 00, the injection amount Q is read. The injection amount Q is calculated based on the operating state of the engine 11 by an injection amount calculation routine prepared separately. In this injection amount calculation routine, for example, a predetermined control map is referred to, and a basic fuel injection amount (basic fuel injection time) corresponding to the engine speed and the accelerator opening is obtained. The basic fuel injection amount is corrected based on the cooling water temperature and the like, and the final injection amount Q is determined.

Next, in step S205, the final fuel pressure PCR is read. At this time, the final fuel pressure PCR set in the above-described fuel pressure setting routine is read. Step S
At 210, the fuel injection period TQ is calculated with reference to the control map shown in FIG. In this control map, an injection period TQ is defined based on the injection amount Q and the final fuel pressure PCR. In this control map, when the injection amount Q is constant, the injection period TQ becomes higher as the final fuel pressure PCR becomes higher.
Becomes shorter. When the final fuel pressure PCR is constant, the injection period TQ becomes longer as the injection amount Q increases.
Then, in the step S210 in FIG. 5, an injection period TQ corresponding to the injection amount Q and the final fuel pressure PCR is read from the control map.

In step S215, the injection period T
Q is stored in the RAM, and then this routine ends. The injection period TQ is used as an energizing time when energizing the solenoid valve 24 of the fuel injection valve 23 in another routine. As a result, the fuel injection valve 23 is opened over the injection period TQ, and a desired amount (injection amount Q) of fuel is injected.

In the injection pressure control routine of FIG.
6, first, in step S300, the leak amount and the estimated target pressure change amount are added to the injection amount Q, and the addition result is set as the estimated discharge amount QBASE of the supply pump 27. Here, the injection amount is the amount of fuel injected from the fuel injection valve 23, and the leak amount is the amount of fuel leaking from the fuel injection valve 23 or the like. The value obtained by adding the leak amount to the injection amount Q is the fuel amount required to maintain the fuel pressure.
In addition, when the target pressure PCRTRG, which is the target value of the fuel pressure according to the operation state of the engine 11, changes, the actual target fuel pressure is set to the target pressure PCRTRG.
Is the amount of fuel (probable amount) required to be equal to.

Next, in step S305, the final fuel pressure PCR is subtracted from the target pressure PCRTRG, and the result of the subtraction is set as a pressure deviation PCRDL. At this time, the final fuel pressure PC set in the above-described fuel pressure setting routine is used.
R is used as the final fuel pressure PCR in step S305. Based on the pressure deviation PCRDL, in steps S310 and S315, feedback (F /
B) Find the proportional term QFBP and the F / B integral term QFBI. Specifically, in step S310, the pressure deviation PCR
DL is multiplied by a predetermined value K, and the result of the multiplication is set as an F / B proportional term QFBP. In step S315, the product of the pressure deviation PCRDL and the predetermined value M is added to the F / B integral term QFBI in the previous control cycle, and the result of the addition is set as a new F / B integral term QFBI.

In step S320, the F / B proportional term QFBP and the F / B
/ B integral term QFBI is added, and the addition result is set as the final ejection amount QPF.

In step S325, a pump energizing current is obtained based on the final discharge amount QPF and the engine speed according to a predetermined control map or a predetermined arithmetic expression. In step S330, the pressure control valve 34 of the supply pump 27 is controlled to be energized by the pump energizing current,
This routine ends. Thus, in the injection pressure control routine, the supply pump 27 is controlled such that the final fuel pressure PCR converges on the target pressure PCRTRG according to the operating state of the engine 11.

According to the embodiment described above, the following effects can be obtained. (1) Under the situation where the higher one of the two fuel pressures PCR1 and PCR2 is correct and the lower one is incorrect,
When the latter value is set as the final fuel pressure PCR, the injection period TQ determined from the injection amount Q and the final fuel pressure PCR
Becomes longer than the original injection period. Therefore, when fuel is injected over a set period, a larger amount of fuel is injected than is originally required.

On the contrary, if the higher value is incorrect,
If the lower value is correct and the former value is set as the final fuel pressure PCR, the injection period TQ will be shorter than the original injection period. Therefore, when fuel is injected over a set period, a smaller amount of fuel is injected than is originally required.

In the present embodiment, each of the first fuel pressure PCR1 and the second fuel pressure PCR2 belongs to a range which can be normally taken,
If the deviation ΔPCR between the two fuel pressures PCR1 and PCR2 is smaller than the determination value X, the higher value is used as the final fuel pressure PCR.
(Steps S135, S145, S15
0), which is reflected in the fuel injection amount control (step S205). Therefore, by performing an appropriate fail-safe process of using the higher value as the final fuel pressure PCR for the injection amount control, it is possible to suppress the injection of an excessive amount of fuel, resulting in an increase in the injection amount. Excessive increase (overrun) of the engine rotation speed can be suppressed.

(2) If the higher value of the two fuel pressures PCR1 and PCR2 is correct and the lower value is incorrect, and the latter value is set as the final fuel pressure PCR, A control amount (F / B proportional term QFBP, required for converging the final fuel pressure PCR to the target pressure PCRTRG,
The F / B integral term QFBI) becomes larger than the original control amount (the F / B proportional term QFBP and the F / B integral term QFBI required when the former value is set as the final fuel pressure PCR). . For this reason, the pressure of the fuel supplied from the supply pump 27, and eventually the pressure of the fuel in the common rail 25, becomes higher than the original fuel pressure.

On the contrary, the higher value is incorrect,
Under the situation where the lower value is correct, the former value is the final fuel pressure P
When set as CR, the control amount required for causing the final fuel pressure PCR to converge to the target pressure PCRTRG is the original control amount (F required when the latter value is set as the final fuel pressure PCR). / B proportional term QFBP and F / B integral term QFBI). Therefore, the pressure of the fuel supplied from the supply pump 27 and the fuel pressure in the common rail 25 are lower than the original fuel pressure.

In this embodiment, the fuel pressures PCR1, PCR
2 belong to the range which can be usually taken, and the deviation ΔPCR
Is smaller than the determination value X, the higher value is set as the final fuel pressure PCR (steps S135, S145, S145).
150), which is reflected in the fuel injection pressure control (step S305). Therefore, by performing an appropriate fail-safe process of using the higher value as the final fuel pressure PCR for the injection pressure control, the common rail 2
Excessive increase in the fuel pressure in 5 can be suppressed.

(3) One fuel pressure PCR1 (or PCR
2) is out of the normal range, and the other fuel pressure PCR
If 2 (or PCR1) belongs to the same range, the latter value is set as the final fuel pressure PCR (step S11).
5, S120, S125, S130). That is, the fuel pressure PCR2 (or PCR1) on the side considered to be normal is set as the final fuel pressure PCR and used for controlling the fuel injection amount and the injection pressure (steps S205 and S205).
305).

Accordingly, it is possible to prevent a problem caused by using the fuel pressure PCR1 (or PCR2), which is considered to be an obvious abnormality, for the control. By using the fuel pressure PCR2 (or PCR1) considered to be normal as the final fuel pressure PCR, the above control can be performed properly.

(4) When both fuel pressures PCR1 and PCR2 are out of the normal range, it is clear that both fuel pressures PCR1 and PCR2 are abnormal. In this embodiment, in this case, both fuel pressures PCR1 and P
Instead of CR2, a value (target pressure) determined based on the operating state of the engine 11 at that time is set as the final fuel pressure PCR (steps S135 and S140), and is used for fuel injection amount control and injection pressure control. (Steps S205 and S305).

Accordingly, it is possible to prevent a problem caused by using both fuel pressures PCR1 and PCR2, which are considered to be obvious abnormalities, for the control. By using the target pressure as the final fuel pressure PCR for control, the control can be properly continued.

(5) If both the fuel pressures PCR1 and PCR2 belong to the normal range and the deviation ΔPCR is larger than the determination value X, one of the fuel pressure sensors 44 (or 4
It is considered that 5) is clearly characteristic abnormal. But,
It is unknown which fuel pressure sensor 44 (or 45) has the characteristic abnormality. On the other hand, in the present embodiment, the engine 1 at that time is replaced with the two fuel pressures PCR1 and PCR2.
The value (target pressure) suitable for the operating state of 1 is used as the final fuel pressure PCR.
(Steps S135, S145, S14)
0), and is used for controlling the fuel injection amount and the injection pressure (steps S205 and S305).

Accordingly, the fuel pressure PC which is suspected to have characteristic abnormalities
R1 (or PCR2) is used for the control, and it is possible to suppress the injection of an excessive amount of fuel or the excessive increase in fuel pressure. By using the target pressure as the final fuel pressure PCR for control, the control can be properly continued.

The present invention can be embodied in another embodiment described below. The present invention is also applicable to a system in which three or more fuel pressure sensors are used and control is performed using their detected values as control parameters. In this case, for example, when each of the fuel pressures of the two predetermined fuel pressure sensors belongs to a normal range and the deviation ΔPCR is smaller than the determination value X, the higher fuel pressure is set as the final fuel pressure PCR.

The present invention is not limited to a diesel engine, and is an engine in which the fuel injection amount and injection pressure are controlled based on the fuel pressure in the fuel distribution pipe, for example, a direct injection type in which fuel is directly injected into a combustion chamber. It is also applicable to gasoline engines.

The present invention relates to a fuel injection control device that uses the detection values of a plurality of fuel pressure sensors only for controlling the fuel injection amount, or a fuel injection control device that uses only the fuel injection pressure control. Is also applicable.

In the above-described embodiment, the fuel pressure sensors 44, which output different voltages by the predetermined amount ΔV with respect to the same pressure,
45 is used. Therefore, if both the fuel pressure sensors 44 and 45 are normal, a certain deviation should occur between the voltages of the two. Utilizing this, the A / D conversion value VPC
1, a deviation of VPC2 may be determined, and if the deviation is smaller than a predetermined value, the A / D converter 47 may be determined to be abnormal. By doing so, the A / D converter 47
Can be detected.

As the fuel pressure sensors 44 and 45, fuel pressure sensors of the type outputting the same voltage at the same pressure may be used.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an embodiment in which a fuel injection control device of the present invention is embodied in a diesel engine.

FIG. 2 is a graph showing output characteristics of a fuel pressure sensor.

FIG. 3 is a flowchart showing a procedure for setting a fuel pressure.

FIG. 4 is a flowchart showing a procedure for setting a fuel pressure.

FIG. 5 is a flowchart showing a procedure for setting an injection period in injection amount control.

FIG. 6 is a schematic diagram showing a map structure of a control map used for setting an injection period.

FIG. 7 is a flowchart showing a procedure for controlling the injection pressure.

[Explanation of symbols]

11 engine, 23 fuel injection valve, 25 common rail, 27 supply pump, 44 first fuel pressure sensor,
45: second fuel pressure sensor, 46: ECU (electronic control unit).

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 45/00364 F02D 45/00 364K 364Q F02M 37/00 F02M 37/00 A Q F term (reference) 3G084 AA01 BA13 BA14 DA30 EA03 EA11 EB08 EB22 EC03 FA00 FA10 FA20 FA33 3G301 HA02 JA21 JB01 LB06 MA11 NA08 NB01 NC02 PA11Z PB08Z PE01Z PE08Z PF03Z

Claims (5)

[Claims] 1. A plurality of fuel pressure sensors provided in a fuel distribution pipe for distributing pressurized fuel to a plurality of fuel injection valves of an engine, and each detecting a pressure of fuel in the fuel distribution pipe, and the fuel pressure sensor. A fuel pressure setting unit that sets a fuel pressure used as a control parameter based on each detected value; a fuel injection amount according to an operation state of the engine; and an injection period based on a fuel pressure by the fuel pressure setting unit. Asked,
Fuel injection control means for controlling the fuel injection valve so that fuel is injected over the injection period. The fuel pressure setting means, wherein each detection value of two predetermined fuel pressure sensors is If it belongs to the normal range and the difference between the two detection values is smaller than a predetermined determination value, the higher detection value is
The fuel injection control device is set as the fuel pressure for calculating the injection period by the fuel injection control means. 2. A plurality of fuel pressure sensors provided in a fuel distribution pipe for distributing pressurized fuel supplied from a fuel pump to a plurality of fuel injection valves of an engine, and each detecting a pressure of the fuel in the fuel distribution pipe. A fuel pressure setting means for setting a fuel pressure used as a control parameter based on a detection value of each of the fuel pressure sensors; And a fuel injection control unit that controls the fuel pump so as to converge to the fuel injection control device, wherein the fuel pressure setting unit belongs to a range where each detection value of two predetermined fuel pressure sensors can normally take, And, when the deviation between the two detection values is smaller than the predetermined determination value, the higher detection value,
The fuel injection control device is set as the fuel pressure for controlling the fuel pump by the fuel injection control means. 3. The fuel pressure setting means sets a detected value of the other fuel pressure sensor as the fuel pressure when only one detected value of the predetermined two fuel pressure sensors is out of the range. 3. The fuel injection control device according to claim 1, wherein 4. The fuel pressure setting means sets a value corresponding to an operating state of the engine as the fuel pressure when both detected values of two predetermined fuel pressure sensors are out of the range. 3. The fuel injection control device according to claim 1, wherein: 5. The fuel pressure setting means, when both detected values of two predetermined fuel pressure sensors belong to the range and a difference between the two detected values is equal to or greater than the determination value, sets the operating state of the engine. 3. The fuel injection control device according to claim 1, wherein a value corresponding to the fuel pressure is set as the fuel pressure.