JPH1054292A - Fuel feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct failure judgement which can identify a failed section in a fuel feeder equipped with a common rail. SOLUTION: This fuel feeder is provided with a common rail which stores high-pressure fuel, an injector which injects the high-pressure fuel stored in the common rail to respective cylinders of an internal combustion engine, and a fuel supply pump which force-feeds the fuel. A control unit detects a pressure waveform Pc in the common rail, differentiates the pressure waveform to obtain DPc, and shapes its waveform to obtain a signal SDPc including a positive/ negative square wave pulse. Based on the square wave pulse and a fuel supply pump driving signal Cp or an injector driving signal Ci, occurrence of some failure in this fuel feeder including a failed supply pump or injector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system, and more particularly, to a fuel supply system in which fuel is stored in a high pressure state on a common rail, and high pressure is applied to each cylinder of the internal combustion engine via an injector (fuel injection valve). The present invention relates to a fuel supply device for injecting fuel.

[0002]

2. Description of the Related Art Conventionally, as a fuel supply device for a diesel engine, a device comprising a fuel injection pump and a nozzle has been generally used. In recent years, however, in order to achieve more precise control, a fuel is supplied to a common rail. Is stored in a high-pressure state, and a high-pressure fuel is injected from a common rail to each cylinder of the internal combustion engine via an injector.

As one example of such a fuel supply device, Japanese Patent Application Laid-Open No. H10-109052 discloses that an abnormality such as fuel leakage occurs when a control command value for a fuel supply pump exceeds a predetermined judgment value. Disclosed is a fuel supply device provided with abnormality determination means for determination.

[0004]

According to the above prior art, an appropriate measure is taken by such an abnormality judgment. In this case, the abnormality judgment includes not only the fuel leakage but also the pressure control valve of the pump. There is a possibility that factors such as a decrease in the responsiveness of the pump and a decrease in the pumping ability of the pump may affect the performance. However, in the above-described conventional technology, it is not possible to determine which factor caused the abnormality, and therefore, there is a problem that even if the abnormality is detected, appropriate measures cannot be taken.

[0005] In view of such circumstances, an object of the present invention is to perform an abnormality determination in a fuel supply device having a common rail so that an abnormal portion can be identified.

[0006]

A fuel supply device according to the present invention, which has been devised to achieve the above object, comprises a common rail for storing high-pressure fuel, and a high-pressure fuel stored in the common rail for each cylinder of an internal combustion engine. An injector for injecting
A fuel supply pump for pumping fuel to the common rail,
A pressure detecting means for detecting a pressure waveform in the common rail; a waveform converting means for differentiating and shaping the pressure waveform detected by the pressure detecting means to generate a square wave pulse; and a waveform converting means. Abnormality determining means for determining, based on a square wave pulse and a drive signal for the injector or the fuel supply pump, whether or not a device abnormality including an abnormality of the injector or the fuel supply pump has occurred.

In the fuel supply device configured as described above, the difference between the generation timing of the positive square wave pulse and the generation timing of the pump drive signal among the square wave pulses obtained by differentiating and shaping the pressure waveform. Accordingly, it is possible to detect the deterioration of the response of the pressure control valve. Further, it is possible to detect the deterioration of the responsiveness of the control valve of the injector from the difference between the generation timing of the negative square wave pulse and the generation timing of the injector drive signal.

Further, the variation in the injection start timing between the cylinders can be detected from the variation in the generation timing of the negative square wave pulse. Further, from the difference between the width of the positive square wave pulse and the width of the pump drive signal (pumping period), it is possible to detect a decrease in pumping capacity and fuel leakage in the piping.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing a configuration of a fuel supply device for a diesel engine according to an embodiment of the present invention. As shown in FIG. 1, the fuel supply device includes a two-cylinder high-pressure pump 1. The high-pressure pump 1 is provided with a drive shaft 2. The drive shaft 2 is connected to a crankshaft 4 of a diesel engine 3.
When the crankshaft 4 makes two rotations, the drive shaft 2 makes one rotation. Further, triangular cams 5 and 6 are fixed to the drive shaft 2. Further, cylinders 7 and 8 are provided in the high-pressure pump 1, and pistons 9 and 10 that slide on the cam surfaces of the cams 5 and 6 are arranged in the cylinders 7 and 8. The pistons 9, 9 associated with the rotation of the cams 5, 6
The downward movement of 10 causes the pressurizing chambers 11 and 12 in the cylinders 7 and 8 to move.
The fuel in the tank 14 is supplied via the low-pressure pump 13 to the fuel cell.

Discharge amount control solenoid valves 15 and 16 are disposed above the cylinders 7 and 8, and open and close the fuel supply passage from the low pressure pump 13. When the pistons 9 and 10 move upward with the discharge amount control solenoid valves 15 and 16 closed, the fuel pressurizing operation is performed in the pressurizing chambers 11 and 12. By controlling the valve closing timing (TF in FIG. 2) of the solenoid valves 15 and 16 during the pressurizing operation, the fuel discharge amount (shaded portion in FIG. 2) can be adjusted. . The discharge amount control solenoid valves 15 and 16 are opened at the top dead center (θ _{0 in} FIG. 2) of the cam lift, and the fuel pressurization in the pressurizing chambers 11 and 12 is completed. .

The pressurizing chambers 11 and 12 of the high-pressure pump 1
Are connected to a common high-pressure accumulator pipe, a so-called common rail 19, by fuel supply pipes 17 and 18. A check valve 20 is provided at the pump-side end of the fuel supply pipe 17, and a check valve 21 is provided at the common rail-side end. Similarly, a check valve 22 is provided at the pump-side end of the fuel supply pipe 18, and a check valve 23 is provided at the common rail-side end. These check valves 2
Reference numerals 0, 21, 22, and 23 permit the supply of fuel from the high-pressure pump 1 to the common rail 19 and regulate the return of fuel from the common rail 19 to the high-pressure pump 1.

An injector (injection valve) 25 for each cylinder of the diesel engine 3 is connected to the common rail 19 through a branch pipe 24. A flow limiter 26 is provided at an end on the common rail side of the branch pipe 24. The flow limiter 26 allows fuel supply to the injector 25 in a certain amount or less, and supplies fuel to the injector 25 in a certain amount or more. It regulates fuel supply. That is, if the injector 25 is damaged for any reason, the flow limiter 26
Limit the fuel supply to the plant.

The injector 25 has a three-way control valve 3.
By controlling the three-way control valve 31, high-pressure fuel stored in the common rail 19 can be injected from the injector 25 into each cylinder.

Electronic control unit (hereinafter referred to as ECU)
An input 27 receives information on an engine speed and an accelerator opening from a crank angle sensor 28, a cylinder discriminating sensor 29, and an accelerator opening sensor 30 and determines an optimum value determined according to an engine state determined from these signals. The control signal is output to the three-way control valve 31 so that the injection timing and the injection amount are equal to. As shown in FIG. 2, the crank angle sensor 28 outputs a signal of one pulse for each predetermined crank angle, and the cylinder discriminating sensor 29 outputs a signal of one pulse for each rotation of the drive shaft 2.

Further, the common rail 19 is provided with a common rail pressure sensor 32 for detecting a common rail pressure.
The ECU 27 controls the discharge amount of the high-pressure pump 1 so that the common rail pressure by the sensor 32 becomes an optimum value set according to the accelerator opening and the number of revolutions. The common rail pressure is input to the ECU 27 via the differentiating circuit 33 and the waveform shaping circuit 34.

When the diesel engine 3 is started, the cams 5 and 6 of the high-pressure pump 1 rotate, and with this rotation, the pistons 9 and 10 reciprocate to supply fuel from the low-pressure pump 13 to the high-pressure pump 1. High-pressure fuel is supplied to the common rail 19 through the fuel supply pipes 17 and 18, and the fuel is accumulated in the common rail 19. Here, the ECU 27
Controls the discharge amount of the high-pressure pump 1 so that the common rail pressure detected by the common rail pressure sensor 32 becomes an optimum value set according to the accelerator opening and the number of revolutions.

That is, the ECU 27 determines the crank angle
When the pulse signal from the source 28 is input, the process starts,
First, the common rail pressure by the common rail pressure sensor 32
And the accelerator opening by the accelerator opening sensor 30,
Capture of engine speed by rank angle sensor 28
Do. Then, the ECU 27 determines that the common rail pressure is
To the optimum value set according to the opening degree and the number of rotations.
At a predetermined crank angle θ _aWith high pressure pump 1
Is calculated (see FIG. 2). Next
The ECU 27 calculates the fuel discharge timing shown in FIG.
At the time of reaching the TF, the discharge amount control solenoid valves 15 and 16 are turned on.
By closing the valve, a predetermined amount of high-pressure fuel is supplied to the high-pressure pump 1.
To the common rail 19.

The ECU 27 controls the opening and closing of the three-way control valve 31 of the injector 25 in order to inject a fuel amount corresponding to the operating state of the diesel engine 3 into the cylinder, and the fuel in the common rail 19 is supplied to each cylinder of the diesel engine 3. Spray.

FIG. 3 shows (A) common rail pressure sensor 32
, The output signal DP of the differentiating circuit 33
c, (C) the output signal SDPc of the waveform shaping circuit 34,
(D) a pulse Ne indicating a predetermined angle in the output signal of the crank angle sensor 28, and (E) a pump drive signal output by the electronic control unit 27, that is, a discharge amount control solenoid valve 15, 1.
6A and 6B are diagrams illustrating an energization signal Cp to the ECU 6 and (F) an injector drive signal output from the electronic control unit 27, that is, a valve opening command signal Ci of the three-way control valve 31, respectively. In this figure, the rise and fall of the pressure Pc appear four times, which correspond to the pumping and the injection corresponding to the four cylinders, respectively, and correspond to the combustion order from the left. 1st cylinder, 5th cylinder, 3rd cylinder, 6
It is related to the number cylinder.

As shown in FIG. 3A, the pressure Pc of the fuel in the common rail 19 increases when the fuel is pumped from the high-pressure pump 1 and the injector 25
It decreases when fuel is injected from. In order to quantitatively grasp such a pumping time and a pumping period and an injection timing and an injection period, in the present invention, a differentiating circuit 33 and a waveform shaping circuit 34 are provided, and the processing results are shown in FIG. )) As shown in SDPc. The positive square wave pulse of SDPc represents pumping, while the negative square wave pulse represents injection.

When the discharge amount control solenoid valves 15 and 16 in the high-pressure pump 1 deteriorate, the response delay to the drive signal increases. Therefore, the ECU 27 detects the time difference T ₁ from the generation timing of the pump drive signal Cp to the generation timing of the positive square wave pulse of SDPc, and, based on the result, detects the discharge amount control solenoid valve 1 in the high-pressure pump 1.
5 and 16 abnormalities are detected.

Similarly, when the control valve in the injector 25 deteriorates, the response delay to the drive signal increases. Therefore, the ECU 27 sets the injector drive signal Ci
And detecting a time difference T ₂ of the from the generation timing to the generation timing of the negative of the square-wave pulse of SDPC, from the result, it detects the abnormality of the control valve in the injector 25.

The ECU 27 determines the injection start timing, ie, SD, from the predetermined engine rotation angle position signal Ne.
By detecting the time difference T ₃ to the negative generation timing of the square wave pulses Pc, to detect variations in the injection start timing among the cylinders, as a result, be corrected if necessary.

If the pumping capacity of the pump is reduced or fuel leaks in the piping, the actual pumping period obtained from the sensor output signal becomes longer than the pumping period indicated by the pump drive signal. Therefore, the ECU 27 determines that the width T ₄ of the positive square wave pulse of SDPc and the pulse width T
The difference from ₅ is detected, and from the result, a decrease in pumping capacity and a fuel leak in the piping are detected.

While the embodiment in which a two-cylinder high-pressure pump is employed in a six-cylinder diesel engine has been described above, the present invention can of course be applied to other types of engines.

[0027]

As described above, according to the present invention,
An abnormal part can be identified in the abnormality determination of the common rail type fuel supply device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a fuel supply device for a diesel engine according to an embodiment of the present invention.

FIG. 2 is a time chart for explaining a control operation of the fuel supply device.

FIG. 3A shows an output signal P of the common rail pressure sensor 32;
c, (B) an output signal DPc of the differentiating circuit 33, (C) an output signal SDPc of the waveform shaping circuit 34, (D) a pulse Ne indicating a predetermined angle in the output signal of the crank angle sensor 28,
(E) is a diagram showing a pump drive signal Cp output from the electronic control unit 27, and (F) is a diagram showing an injector drive signal Ci also output from the electronic control unit 27.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... High pressure pump (fuel supply pump) 2 ... Drive shaft 3 ... Diesel engine 4 ... Crank shaft 5, 6 ... Triangular cam 7, 8 ... Cylinder of high pressure pump 1, 9, 10 ... Piston 11, 12 ... Pressurizing chamber 13 ... low-pressure pump 14 ... fuel tank 15, 16 ... discharge amount control solenoid valve 17, 18 ... fuel supply pipe 19 ... common rail (accumulation chamber) 20, 21, 22, 23 ... check valve 24 ... branch pipe 25 ... injector ( Fuel injection valve) 26 Flow limiter 27 Electronic control unit (ECU) 28 Crank angle sensor 29 Cylinder discrimination sensor 30 Accelerator opening sensor 31 Three-way control valve 32 Common rail pressure sensor 33 Differentiating circuit 34 Waveform shaping circuit

Claims (1)

[Claims] 1. A common rail for storing high-pressure fuel, an injector for injecting high-pressure fuel stored in the common rail into each cylinder of an internal combustion engine, a fuel supply pump for pumping fuel to the common rail, and a pressure waveform in the common rail. Pressure-detecting means, a waveform converting means for differentiating and shaping the pressure waveform detected by the pressure detecting means to generate a square-wave pulse, a square-wave pulse obtained by the waveform converting means, and the injector Or a failure determining means for determining whether or not a device failure including a failure of the injector or the fuel supply pump has occurred based on a drive signal to the fuel supply pump.