JPH06213051A - Accumulating fuel injection system - Google Patents

Abstract

PURPOSE:To provide an accumulator type fuel injection system which is able to detect any fuel leakage accurately irrespective of the load variation and revolution of an engine. CONSTITUTION:In a period of time ranging from a span of timing Ti when an injector driving pulse is stopped to another timing Te when the fuel supply of a fuel feed pump is started, common rail pressure Pc is usually kept almost constant. On the other hand, when a fuel leakage out of a fuel feeding system ranging from the fuel feed pump to the injector is produced, the common rail pressure Pc goes down significantly in this period of time. In addition, this behavior is not related to the load variation and revolution of a diesel engine. Accordingly, at these two point of time, both common rail pressure values Pc1 and Pc2 are measured, and on the basis of the difference, the fuel leakage from the fuel feeding system is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention stores fuel fed under pressure from a fuel supply pump in a high pressure state in a pressure accumulating chamber (common rail), and uses the high pressure fuel in a fuel injection valve provided in each cylinder of an internal combustion engine. More specifically, the present invention relates to a pressure accumulation type fuel injection device capable of detecting a fuel leak from the fuel supply system.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 62-2581.
As disclosed in Japanese Patent Laid-Open No. 60, there is known a device in which fuel fed under pressure from a fuel supply pump is temporarily stored in a common rail and then injected and supplied to a diesel engine via a fuel injection valve. Further, in this type of pressure accumulating fuel injection device, the fuel injection pressure from the fuel injection valve is determined by the fuel pressure in the common rail (common rail pressure). Therefore, a pressure sensor for detecting the common rail pressure is provided and the fuel pressure is detected. The fuel feed amount from the fuel supply pump is controlled based on the common rail pressure.

As described above, in the device in which the high pressure fuel is temporarily stored in the common rail, the fuel injection pressure can be controlled by the common rail pressure, and the fuel injection amount and the fuel injection timing can be controlled by the opening time and opening timing of the fuel injection valve. Can be controlled respectively. Therefore, as compared with a general fuel injection device including a fuel injection pump and a nozzle, this type of device can perform fuel injection control more precisely.

[0004]

However, in this type of fuel injection device, when an abnormality such as a pipe crack occurs in the fuel supply system from the fuel supply pump to the fuel injection valve, the following problems occur. Was there. In such cases,
Common rail pressure drops due to fuel leaks. Therefore, in order to control the common rail pressure to a desired value, it is necessary to increase the amount of fuel pumped from the fuel supply pump. As a result, a vicious cycle may occur in which the amount of fuel leakage further increases.

Therefore, the applicant of the present application has proposed a fuel from a fuel supply pump as disclosed in Japanese Patent Application No. 3-97324 as a device capable of promptly detecting such a fuel leak in a fuel supply system without using a special sensor. We proposed a device that determines fuel leakage from the control amount that determines the pumping amount. However, when the load of the diesel engine changes, the target value of the common rail pressure (hereinafter referred to as the target common rail pressure) also changes. Then, the control amount of the fuel supply pump also greatly changes, and it may be impossible to determine the fuel leak. For this reason, fuel leakage could not always be detected during operation of the diesel engine.

Further, the threshold value of the above-mentioned control amount used for judging the fuel leakage changes depending on the rotational speed of the diesel engine. Because the fuel supply pump normally rotates in synchronization with the diesel engine, the correspondence between the control amount of the fuel supply pump and the fuel pumping amount changes depending on the rotation speed of the diesel engine. Therefore, even if the target common rail pressure and the fuel injection amount are the same, the threshold value of the control amount changes depending on the rotation speed of the diesel engine. However, it is difficult to set a map for calculating the above threshold value for all engine speeds of the diesel engine. Therefore, in the above device, it is usually not easy to accurately detect the fuel leakage at any rotation speed of the diesel engine.

Therefore, the present invention has been made for the purpose of providing a pressure accumulating fuel injection device capable of accurately detecting a fuel leak irrespective of load fluctuations and engine speed of the engine.

[0008]

DISCLOSURE OF THE INVENTION The present invention, which has been made to achieve the above object, is, as illustrated in FIG. 8, a pressure accumulating chamber for accumulating fuel in a high pressure state, and a fuel supply for feeding fuel to the accumulating chamber under pressure. In a pressure accumulating fuel injection device comprising a fuel injection valve for injecting high-pressure fuel stored in the pressure accumulating chamber into each cylinder of an internal combustion engine, and a fuel pressure detecting means for detecting a fuel pressure in the pressure accumulating chamber, The fuel pressure pumping by the fuel supply pump and the fuel injection by the fuel injection valve are both detected by the determination period detecting means for detecting a predetermined determination period, and the fuel pressure detecting means is detected during the determination period. Fuel pressure change calculating means for calculating a fuel pressure change in the pressure accumulating chamber, and fuel leakage from a fuel supply system from the fuel supply pump to the fuel injection valve is determined based on the calculated fuel pressure change. And fuel leakage determining means, the accumulator fuel injection apparatus characterized by the provided it is a gist that.

[0009]

In the present invention thus constructed, the fuel supply pump pressure-feeds the fuel to the pressure accumulating chamber, and the fuel injection valve injects the fuel stored in the pressure accumulating chamber to each cylinder. Therefore, the fuel pressure in the pressure accumulating chamber detected by the fuel pressure detecting means increases when the fuel is pumped by the fuel supply pump and decreases when the fuel is injected by the fuel injection valve. On the other hand, the fuel pressure in the pressure accumulating chamber is normally held substantially constant during a predetermined determination period in which neither fuel pressure feeding nor fuel injection is executed. Then, the fuel pressure in this determination period exhibits the above-mentioned behavior irrespective of the load variation and the engine speed of the engine.

However, when fuel leaks from the fuel supply system from the fuel supply pump to the fuel injection valve, the fuel pressure in the pressure accumulator drops significantly during the determination period. In the present invention, the fuel pressure change in the accumulator detected during the determination period is calculated, and the fuel leak from the fuel supply system is determined based on the fuel pressure change. Regardless, the fuel leak can be accurately detected.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic configuration diagram showing the overall configuration of a pressure-accumulation fuel injection device according to an embodiment. As shown in the figure, the pressure-accumulation fuel injection device 1 of the present embodiment is a 6-cylinder diesel engine 2
A fuel injection valve (injector) 3 for injecting fuel into each cylinder of the diesel engine 2; a pressure accumulating chamber (common rail) 4 for accumulating high-pressure fuel to be supplied to the injector 3; and high-pressure fuel pressure-feeding to the common rail 4. The fuel supply pump 5 and the electronic control circuit 6 which controls these are provided.

The electronic control circuit 6 includes a rotational speed NE of the diesel engine 2 detected by the rotational speed sensor 7 and an accelerator sensor 8 and an accelerator opening AF (the diesel engine 2).
Corresponding to the load of), diesel engine 2
Of the inside of the common rail 4 detected by the pressure sensor 9 as the fuel pressure detection means by calculating the target common rail pressure for realizing the fuel injection pressure in which the combustion state of the fuel cell is optimized according to the detected operating state. Feedback control for driving and controlling the fuel supply pump 5 is performed so that the fuel pressure (common rail pressure Pc) of the above-mentioned target common rail pressure matches.

The fuel supply pump 5 is composed of a pair of plunger pumps (hereinafter, referred to as a first pump 5a and a second pump 5b) which pressure-feeds fuel at a 240 ° CA cycle. Each pump 5a, 5b has a phase of each plunger of 120 ° C.
A is different. Further, each of the pumps 5a, 5b sucks the fuel stored in the fuel tank 10 through the low pressure pump 11 according to a control command from the electronic control circuit 6, pressurizes it to a high pressure inside itself, and pressurizes this. The high-pressure fuel is pressure-fed to the common rail 4 via the supply pipes 12a and 12b.
The control command to the fuel supply pump 5 is output at a predetermined timing based on the detection value from the rotation speed sensor 7 or a cylinder discrimination sensor (not shown). The internal structure of each pump 5a, 5b is well known and will not be described in detail here.

Each injector 3 is connected by a pipe 13 to
It is connected to a common rail 4 that stores high-pressure fuel.
Then, by opening and closing the control valve 14 provided in each injector 3, the high-pressure fuel accumulated in the common rail 4 to reach the target fuel pressure is injected into the combustion chamber of each cylinder of the diesel engine 2. It The opening / closing operation of the control valve 14 of the injector 3 is executed based on the injector drive pulse from the electronic control circuit 6.

Next, the change of the common rail pressure Pc in the pressure-accumulation type fuel injection device 1 thus constructed will be described with reference to the time chart of FIG. As shown in (b) and (d), the unillustrated plungers of the first pump 5a and the second pump 5b slide at a 240 ° CA cycle.
When the drive pulses shown in (a) and (c) are input from the electronic control circuit to the pump (first pump 5a or second pump 5b) whose plunger is moving upward, the pump will cause the common rail 4 to pass after a predetermined delay time TC. To start pumping fuel to. The pump continues to pump fuel until the plunger reaches the top dead center, and pumps to the common rail 4 an amount of fuel proportional to the plunger movement amount during that time. That is, when the electronic control circuit 6 outputs the first pump drive pulse or the second pump drive pulse at the predetermined timing TF,
Then, at the timing Te after TC, the common rail pressure Pc
Begins to rise.

Further, the electronic control circuit 6 controls the control valve 14 of the injector 3 belonging to the ignition cylinder (e) every time each cylinder of the diesel engine 2 reaches the ignition timing.
The injector drive pulse shown in is output. Then, the injector 3 is opened almost simultaneously with the pulse output, and the fuel stored in the common rail 4 is injected into the cylinder. Therefore, when the electronic control circuit 6 outputs the injector drive pulse at a predetermined timing, the common rail pressure Pc decreases almost at the same time. When the injector drive pulse is stopped at the predetermined timing Ti, the injector 3 closes and the fuel injection ends. The timings TF, Te, and Ti are defined by the time from the reference signal for cylinder discrimination to the timing.

Since the common rail pressure Pc exhibits such a behavior, the common rail pressure Pc is usually almost in the period from the timing Ti at which the injector drive pulse is stopped to the timing Te at which the fuel supply of the fuel supply pump 5 is started. Holds constant. However, when fuel leaks from the fuel supply system from the fuel supply pump 5 to the injector 3, the common rail pressure Pc significantly decreases during this period. Therefore, in this embodiment, the common rail pressure Pc is measured at two points during the above period (Pc1, Pc1,
The fuel leak from the fuel supply system is detected based on the pressure difference between the common rail pressures Pc1 and Pc2. Next, the fuel leak detection process executed by the electronic control circuit 6 will be described with reference to FIGS.

First, FIG. 3 is a flow chart showing the main routine of the fuel leakage detection processing of this embodiment. In addition,
This process is executed every predetermined period (for example, 3 msec.) During operation of the diesel engine 2. When the process is started, first, at step 301, the threshold value Pt of the pressure decrease rate DPc used for judging the fuel leakage is calculated based on the average value Pcc of the common rail pressure Pc and the fuel temperature by the map of FIG. The pressure decrease rate DPc is a pressure decrease rate per 1 msec. While the common rail pressure Pc changes from Pc1 to Pc2, and is calculated by the process described later. Further, the average value Pcc can be substituted by the common rail pressure Pc detected at a predetermined timing (for example, between the timing Ti and the timing Te). Further, the fuel temperature is detected by a well-known fuel temperature sensor 20 provided in the fuel tank 10.

The map of FIG. 4 has the following characteristics. In the period from the timing Ti to the timing Te when the fuel is not supplied / injected into the common rail 4, some fuel flows out from the gap of the valve of the injector 3 even if the fuel supply system is normal. Therefore,
During this period, the common rail pressure Pc slightly decreases as illustrated in FIG. The decreasing tendency of the common rail pressure Pc becomes more remarkable as the common rail pressure Pc becomes higher, and the viscosity of the fuel becomes lower, as illustrated by the alternate long and short dash line in FIG.
For example, the higher the fuel temperature, the more remarkable. Therefore, the map of FIG. 4 is also made so that the threshold value Pt increases as the average value Pcc of the common rail pressure Pc increases and the fuel temperature increases. In addition, in FIG. 5, the maximum values of the common rail pressure Pc are shown together for comparison. Also,
Although the fuel temperature is used as the viscosity parameter in FIGS. 4 and 5, the fuel viscosity also changes depending on parameters other than temperature, such as the type of fuel. Therefore, a higher-order map in which these parameters are added may be created.

Returning to FIG. 3, in the following step 303,
Based on the pressure difference between the common rail pressures Pc1 and Pc2, it is determined whether or not the pressure decrease rate DPc calculated in the process described later exceeds the threshold value Pt. When DPc> Pt, the process proceeds to the following step 305, and when DPc ≦ Pt, the process is temporarily terminated. When an affirmative decision is made in step 303 and the routine moves to step 305, the abnormality counter N that is reset when the diesel engine 2 is started is incremented and the routine moves to step 307. In step 307, it is determined whether or not the value of the abnormality counter N exceeds 10. If it exceeds 10, in step 309, the abnormality flag Er indicating fuel leakage is set, and the process is terminated once,
If N ≦ 10, the process is temporarily terminated. In addition,
When the abnormality flag Er is set, other routines (not shown) perform predetermined processing such as notification of abnormality to the driver.

Next, the processing for calculating the above-mentioned pressure decrease rate DPc will be described. FIG. 6 shows the common rail pressure Pc1.
5 is a flowchart showing a detection timing setting routine for detecting the common rail pressure Pc2 and setting the detection timing of the common rail pressure Pc2. It should be noted that this routine is executed as an interrupt process to the main routine when 2 msec. Has elapsed from the timing Ti.

When the processing is started, in step 601,
The common rail pressure Pc detected at that time is defined as the common rail pressure Pc1. In the following step 603, it is determined whether or not the period from the timing Ti to the timing Te is longer than 7 msec. If an affirmative determination is made here, the routine proceeds to subsequent step 605, where the determination period flag F is set to 2. Then, in step 607, the timer Tm is set to 4 msec.
And the process ends. The determination period flag F
Is a flag indicating the length of a period (hereinafter referred to as a determination period) from the detection timing of the common rail pressure Pc1 to the detection timing of the common rail pressure Pc2.

Further, Te-Ti≤7 (msec.),
When a negative determination is made in step 603, the process proceeds to step 611. In step 611, Te-Ti is 4 msec.
Determine if it is longer. If an affirmative determination is made here, the process moves to the following step 613, and the determination period flag F is set to 1. Then, in step 615, the timer Tm is set to 1 m.
Set to sec. and end the process.

On the other hand, Te-Tm ≦ 4 (msec.),
When a negative determination is made in step 611, the determination period flag F is set to 0 in step 617, and the post-processing is ended.
When the determination period flag F is set to 0, the electronic control circuit 6 does not execute the pressure decrease rate calculation routine described below. Next, FIG. 7 is a flow chart showing a pressure decrease rate calculation routine for detecting the common rail pressure Pc2 and calculating the pressure decrease rate DPc. It should be noted that this routine is executed as an interrupt process to the main routine when the set time has elapsed after the timer Tm was set in step 607 or 615 described above.

When the processing is started, in step 701,
The common rail pressure Pc detected at that time is referred to as common rail pressure Pc2. In the following step 703, the common rail pressure Pc2 detected in step 701 is subtracted from the common rail pressure Pc1 detected in step 601 and the value is taken as the pressure decrease rate DPc. In the following step 705, it is determined whether or not the determination period flag F is 1. When F = 1, the processing is terminated as it is, and F ≠ 1.
That is, when F = 2, the process proceeds to the following step 707. In step 707, the pressure decrease rate DPc calculated in step 703 is divided by 4, and this is newly set as the pressure decrease rate DPc, and the process ends.

That is, when the determination period flag F is 1, the determination period is 1 msec. Therefore, Pc1 -P
c2 is the rate of pressure drop per 1 msec. However, when the determination period flag F is 2, the determination period is 4 msec. Therefore, Pc1-Pc2 is 4msec.
It is the rate of pressure drop per hit. Therefore, in the case of F = 2, in step 707, (Pc1-Pc2) / 4 is set to the pressure decrease rate D.
It is Pc.

In the above process, step 603.
6 to 615 correspond to the determination period detecting means, step 703 corresponds to the fuel pressure change calculating means, and steps 301 to 309 correspond to the fuel leak determining means. Through the above processing, in this embodiment, as shown in FIG. 2F, 2 mse of the timing Ti at which the injector drive pulse stops.
c. The common rail pressure Pc1 is detected later, and the common rail pressure Pc2 is detected 1 msec. or 4 msec later. Furthermore, the detection timing of the common rail pressure Pc2,
There is an interval of at least 1 msec. With the timing Te at which the fuel supply pump 5 pumps fuel to the common rail 4. Therefore, during the determination period, the fuel injection by the injector 3 and the fuel supply by the fuel supply pump 5 have almost no influence on the change in the common rail pressure Pc. Therefore,
During the above-described determination period, the common rail pressure Pc is normally held substantially constant regardless of the load fluctuation and the rotation speed of the diesel engine 2. In the case of fuel leakage, the common rail pressure Pc significantly decreases during the above determination period.

In this embodiment, 1 m in the above determination period
The pressure decrease rate DPc per sec. is calculated, and when the number of times the threshold value Pt exceeds the threshold value Pt exceeds 10 times, the fuel leakage from the fuel supply system from the fuel supply pump 5 to the injector 3 is determined. . Therefore, the pressure-accumulation fuel injection device 1 of the present embodiment can accurately detect the fuel leakage regardless of the load fluctuation and the rotation speed of the diesel engine 2.

The present invention is not limited to diesel engines, but can be applied to various internal combustion engines, such as in-cylinder injection spark ignition gasoline engines.

[0030]

As described above in detail, in the pressure-accumulation fuel injection device of the present invention, the fuel supply is performed based on the change in the fuel pressure in the pressure accumulation chamber during the predetermined determination period in which neither the fuel pressure feeding nor the fuel injection is executed. A system fuel leak has been detected. During this determination period, the fuel pressure in the pressure accumulating chamber is usually kept substantially constant regardless of the load variation and the engine speed of the engine.
Further, in the case of fuel leakage, the fuel pressure is significantly reduced during the above determination period. Therefore, in the present invention, the fuel leakage can be accurately detected regardless of the load variation and the engine speed of the engine.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an entire pressure accumulation type fuel injection device of an embodiment.

FIG. 2 is a time chart showing changes in common rail pressure in the example.

FIG. 3 is a flowchart showing a main routine of a fuel leakage detection process of the embodiment.

FIG. 4 is a map showing the relationship between the threshold value of the pressure drop rate, the common rail pressure, and the fuel temperature.

FIG. 5 is a time chart showing the difference in common rail pressure change depending on the average common rail pressure and fuel temperature.

FIG. 6 is a flowchart showing a detection timing setting routine of the embodiment.

FIG. 7 is a flowchart showing a pressure decrease rate calculation routine of the embodiment.

FIG. 8 is a diagram illustrating the configuration of the present invention.

[Explanation of symbols]

1 ... Accumulation type fuel injection device 2 ... Diesel engine
3 ... Injector 4 ... Common rail 5 ... Fuel supply pump
6 ... Electronic control circuit 9 ... Pressure sensor

Claims (1)

[Claims] 1. A pressure accumulation chamber for storing fuel in a high pressure state, a fuel supply pump for pressure-feeding the fuel to the pressure accumulation chamber, and a fuel injection valve for injecting the high pressure fuel stored in the pressure accumulation chamber into each cylinder of an internal combustion engine. In the pressure-accumulation fuel injection device including a fuel pressure detection unit that detects the fuel pressure in the pressure accumulation chamber, a predetermined determination is made that neither the fuel pressure pumping by the fuel supply pump nor the fuel injection by the fuel injection valve is executed. Determination period detection means for detecting a period, fuel pressure change calculation means for calculating a fuel pressure change in the pressure accumulation chamber detected by the fuel pressure detection means during the determination period, and based on the calculated fuel pressure change A fuel-accumulation fuel injection device comprising: a fuel-leakage judging means for judging a fuel leak from a fuel supply system from the fuel supply pump to the fuel injection valve;