JP2000161172A - Accumulator type fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent engine trouble and the like by determining whether or not a fuel detection means for detecting the fuel pressure of an accumulator has failed. SOLUTION: High pressure fuel pressurized by a fuel pump 1 is stored in an accumulator 3 and supplied via a fuel passage 10a to a fuel injection nozzle 9 which injects the fuel into the fuel chamber of an engine. When the ratio of the average value of the absolute values of the time rate of change of the output of a fuel pressure detection means 3a for detecting the fuel pressure of the accumulator 3 to the average value of the outputs of a fuel detection means 3a is not greater than a predetermined value and the difference between the output value of the fuel pressure detection means 3a and the set pressure of the accumulator 3 is not smaller than a predetermined value, a determination means 8 determines that the fuel pressure detection means 3a has failed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator type fuel injection device.

[0002]

2. Description of the Related Art As a fuel injection device for a diesel engine, a high pressure fuel accumulated in an accumulator is stably supplied to each cylinder of the engine to improve the engine performance in a wide operating range from a low speed range to a high speed range. There is a type fuel injection device (common rail system). Even when such a fuel injection device is used, if the fuel injection rate immediately after the start of fuel injection is excessive, rapid explosion combustion is performed at the beginning of combustion, which not only increases engine noise but also increases exhaust gas emissions. Nitrogen oxides (NOx) increase.

In order to solve such a problem, a pressure-accumulation type fuel injection device which injects fuel at a low fuel injection rate in an initial stage of each fuel injection cycle has been proposed. The fuel injection device according to this proposal selectively communicates, for example, a low-pressure accumulator for storing low-pressure fuel, a high-pressure accumulator for storing high-pressure fuel, and a low-pressure accumulator or a high-pressure accumulator to an injector (fuel injection nozzle). A switching valve for switching the fuel injection rate by controlling the fuel injection rate, and an on-off valve for controlling the fuel injection timing by connecting / disconnecting the pressure control chamber of the injector and the fuel tank.

[0004] With respect to the fuel pressure generation in the accumulator, for example, a low-pressure fuel and a high-pressure fuel are obtained by using a low-pressure fuel pump and a high-pressure fuel pump driven by an engine, respectively. There is one that obtains low-pressure fuel by regulating high-pressure fuel introduced into an accumulator (for example, JP-A-6-93936). A pressure-accumulation fuel injection device of the type that obtains low-pressure fuel of a low-pressure accumulator from high-pressure fuel of a high-pressure accumulator (for example, WO98 / 0906)
In 8), for example, the on-off valve for controlling the fuel injection timing, which is provided corresponding to the injector of each cylinder, is closed, and the switching valve for switching the fuel injection rate is switched to the low pressure side. The chamber (fuel pool) is filled with low-pressure fuel, and the injector is kept closed. When the fuel injection start time comes, the on-off valve is opened, the injector is opened, and low-pressure fuel is injected from the nozzle to reduce the pressure. Initial injection (hereinafter referred to as "low-pressure injection") is performed, and when the low-pressure injection period has elapsed, the switching valve is switched to the high-pressure side, and high-pressure fuel from the high-pressure accumulator is injected from the nozzle to perform high-pressure main injection (hereinafter, "high-pressure injection"). When the injection end time comes, the switching valve is switched to the low pressure side and the on-off valve is closed. That is, the switching valve switches between the low-pressure accumulator and the high-pressure accumulator during fuel injection to control the fuel injection waveform.

[0005] In the low-pressure accumulator, after the switching valve is closed, the high-pressure fuel accumulated between the switching valve and the fuel chamber of the injector is regulated to obtain low-pressure fuel. That is, the pressure control valve of the low-pressure accumulator connected to the fuel passage between the low-pressure accumulator and the fuel tank is duty-controlled so that the fuel pressure in the low-pressure accumulator becomes a predetermined pressure. The fuel is discharged to the fuel tank (open to the atmosphere).

[0006]

SUMMARY OF THE INVENTION A pressure sensor for detecting the fuel pressure of a high-pressure accumulator in a pressure-accumulation type fuel injection device having the above-mentioned structure for controlling an injection waveform by switching between a low-pressure accumulator and a high-pressure accumulator during fuel injection. If the signal fails, the signal output fails when the signal output is low (low pressure) (for example, disconnection)
In order to increase the fuel pressure of the high-pressure accumulator, the fuel pressure of the high-pressure accumulator rises, but finally, the relief valve installed in the high-pressure accumulator operates, and the high-pressure accumulator and the fuel Damage to the passage can be prevented.

However, the fuel is always injected at an injection pressure higher than the maximum injection pressure in the normal mode,
Problems such as an increase in the injection amount, an increase in the maximum cylinder pressure, and an increase in noise and vibration are caused. Further, in order to increase the fuel pressure of the low-pressure accumulator, the high-pressure fuel pump repeats excessive fuel pumping, which may cause a failure. When the pressure sensor of the high-pressure accumulator fails in a state where the signal output is in a high output (high pressure) state, control is performed to reduce the fuel pressure of the high-pressure accumulator. The fuel pressure of the high-pressure accumulator required for the operation cannot be obtained. for that reason,
The engine will not run.

Further, when the pressure sensor for detecting the fuel pressure of the low-pressure accumulator fails, when the signal output fails in a low output (low pressure) state (for example, disconnection), the fuel pressure of the low-pressure accumulator is reduced. , The fuel pressure of the low pressure accumulator rises, and eventually becomes equal to the fuel pressure of the high pressure accumulator. As a result, high-pressure injection is performed from the initial stage of injection, and the injection amount increases, resulting in overload operation. Therefore, if the engine continues to be operated in an abnormal state, the engine and the vehicle may be damaged. Also, since the low-pressure accumulator has a lower allowable withstand pressure (allowable pressure) than the high-pressure accumulator, an excessive increase in the fuel pressure in the low-pressure accumulator may cause damage to the low-pressure accumulator and fuel leakage. And so on.

When the pressure sensor of the low-pressure accumulator fails in a state where the signal output is in a high output (high pressure) state, control is performed to reduce the fuel pressure of the low-pressure accumulator. Pressure and only high pressure injection. As a result, the ignition timing is delayed, the exhaust temperature rises, and the torque becomes insufficient, which adversely affects the engine. Therefore, an object of the present invention is to provide a pressure-accumulation type fuel injection device which determines a failure of a fuel pressure detecting means for detecting a fuel pressure of an accumulator to prevent an engine failure or the like.

[0010]

To achieve the above object, according to the first aspect of the present invention, pressurized high-pressure fuel is stored in an accumulator and injected into a combustion chamber of an engine through a fuel passage. It is supplied to the fuel injection nozzle. The determination means is
The ratio between the average value of the absolute value of the rate of change of the output of the fuel pressure detection means with respect to time and the average value of the output of the fuel pressure detection means is equal to or less than a predetermined value, and the output value of the fuel pressure detection means and the set pressure of the accumulator When the difference between the fuel pressure is equal to or more than the predetermined value, it is determined that the fuel pressure detecting means has failed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an accumulator type fuel injection device as an embodiment of the present invention,
FIG. 2 is a schematic diagram showing a connection between main elements of the fuel injection device shown in FIG. 1 and injectors of each cylinder of the engine.

1 and 2, the pressure-accumulation type fuel injection device is mounted on, for example, an in-line six-cylinder diesel engine (not shown), and the high-pressure fuel pump 1 is, for example, as shown in FIG. And two plunger pumps 20, each of which corresponds to the front three cylinders and the rear three cylinders of the in-line six-cylinder engine, respectively, and drives the front three cylinder plungers 21 and the rear three cylinder plungers 21. Each of the cams 22 has three peaks, and each plunger 21 performs three pumping strokes to feed the fuel while the high-pressure fuel pump shaft makes one rotation. Adjustment of the pressure feeding stroke
This is performed by adjusting the closing timing of the solenoid valve 23 provided on the discharge side of the plunger. While the solenoid valve 23 is open, the pressure feeding operation of the plunger pump 20 becomes invalid. I have. The solenoid valve 23 is controlled by an electronic control unit 8 described later.

Returning to FIG. 1, an electronic control unit (ECU) 8 as a control means of the accumulator type fuel injection device includes an engine speed Ne detected by an engine speed sensor 8a and an accelerator opening sensor (not shown). The pressure control stroke is variably adjusted by controlling the solenoid valve 23 of the high-pressure fuel pump 1 in accordance with the accelerator pedal depression amount (accelerator opening) Acc detected by the control unit. The pressure feeding stroke (discharge pressure) according to the fuel pressure P _HP detected by the provided pressure sensor (first fuel pressure detecting means) 3a.
Is feedback-controlled to obtain high-pressure fuel suitable for the operating state of the engine.

The fuel pressurized by the high-pressure fuel pump 1 is stored in the high-pressure accumulator 3. This high-pressure accumulator 3
It is common to each cylinder and communicates with the fuel passage 10a. In the middle of the fuel passage 10a, for example, a switching valve (first control valve) 5 for switching the fuel injection rate, which comprises a two-way solenoid valve, is used.
Is provided for each cylinder (FIG. 2), and a check valve 32 is provided immediately downstream of the switching valve 5 to allow fuel flow only from the upstream side to the downstream side.

The fuel passage 10a has a fuel passage 10b branched from the fuel passage 10a downstream of the check valve 32.
A common low-pressure accumulator (second accumulator) 4 is connected to each cylinder via the. A check valve 6 is provided in the middle of the fuel passage 10b.
And a bypass passage for bypassing the check valve 6, and an orifice 6a is provided in the bypass passage. The check valve 6 is connected between the low-pressure accumulator 4 and the fuel passage 10.
The fuel flow is allowed only in the direction a. When the fuel pressure in the fuel passage 10a is higher than the fuel pressure in the fuel passage 10b,
The fuel in the fuel passage 10a flows into the fuel passage 10b through the orifice 6a, and further flows into the low-pressure accumulator 4. A pressure control valve (second control valve) 34 that operates under the control of the electronic control unit 8 and controls the fuel pressure of the low-pressure accumulator 4 is provided between the low-pressure accumulator 4 and the fuel tank 17 in the fuel passage 10b. Have been. As shown in FIG. 2, the low-pressure accumulator 4 has a pressure sensor 4 for detecting the fuel pressure P _LP in the low-pressure accumulator 4.
a (second fuel pressure detecting means) is provided.

The electronic control unit 8 determines that the fuel pressure in the low-pressure accumulator 4 depends on the engine speed Ne and the accelerator pedal depression amount Acc.
The pressure control valve 34 is controlled based on the actual pressure P _LP detected by the pressure sensor 4a so that the pressure becomes suitable for the engine operating state represented by An injector 9 as a fuel injection nozzle provided in each cylinder of the engine has a pressure control chamber 11 and a fuel chamber (fuel pool) 12 connected to a fuel passage 10a via an orifice 15, and the pressure control chamber 11 Is connected to a fuel tank 17 via an orifice 16 and a fuel return passage 10c. An on-off valve 7 for controlling the fuel injection timing, which is composed of, for example, a two-way solenoid valve, is connected in the middle of the fuel return passage 10c. Note that the on-off valve 7 may be installed in the injector.

The injector 9 has a needle valve 13 for opening and closing a nozzle (injection hole) 9a and a hydraulic piston 14 slidably housed in the pressure control chamber 11. The needle valve 13 is a spring (FIG. (Not shown) to the nozzle 9a side to close the valve. When the fuel is supplied from the fuel passage 10a to the pressure control chamber 11 and the fuel chamber 12 and the on-off valve 7 for controlling the injection timing is closed, the resultant force of the spring force of the spring and the fuel pressure becomes the needle valve 13 In addition, the needle valve 13 closes the nozzle 9a against the fuel pressure in the fuel chamber 12. When the on-off valve 7 opens and the fuel in the pressure control chamber 11 is discharged to the fuel tank 17 side (open to the atmosphere), the needle valve 13 resists the spring force of the spring due to the fuel pressure in the fuel chamber 12. And hydraulic piston 1
The nozzle 9a is opened by moving to the side 4 and fuel in the fuel chamber 12 is injected from the nozzle 9a into the combustion chamber of the engine.

The operation of the fuel injection device having the above configuration in the normal mode will be described below. Under the control of the electronic control unit 8, the fuel pressure in the high-pressure accumulator 3 and the fuel pressure in the low-pressure accumulator 4 are controlled so as to conform to the engine operating state, and the engine operating state (engine speed, accelerator pedal depression amount) is controlled. Etc.), a fuel injection period (fuel injection start / end timing) and a low pressure injection period are set.

As shown in FIG. 4, the switching valve 5 and the on-off valve 7 are both closed until the fuel injection start timing arrives, and the low-pressure fuel passage 10a downstream of the switching valve 5 is supplied to the fuel passage 10a. Low-pressure fuel is supplied from the pressure accumulator 4, and the low-pressure fuel is supplied to the pressure control chamber 11 and the fuel chamber 12 of the injector 9. When the on-off valve 7 is closed, the fuel pressure supplied to the pressure control chamber 11 is applied to the needle valve 13 through the hydraulic piston 14, and the needle valve 13
a is closed and the valve is closed.

At the fuel injection start timing, only the on-off valve 7 is opened, and the low-pressure fuel in the pressure control chamber 11 of the injector 9 is discharged to the fuel tank 17 through the orifice 16 and the fuel return passage 10c. As a result, when the resultant force of the fuel pressure applied to the needle valve 13 via the hydraulic piston 14 and the spring force of the spring becomes smaller than the fuel pressure in the fuel chamber 12 acting to push up the needle valve 13, the needle valve 13 Rises to open the nozzle 9a, and low-pressure fuel is injected from the nozzle 9a. That is, low-pressure injection is performed at a relatively low fuel injection rate (fuel injection amount per unit time) at the beginning of injection. By this low-pressure injection, the combustion in the initial stage of the fuel injection period is performed relatively slowly, and the amount of NOx in the exhaust gas is reduced.

When a predetermined time has elapsed since the start of the low-pressure injection, the switching valve 5 for switching the injection rate is opened while the on-off valve 7 for controlling the injection timing is opened, and the fuel chamber 12 is opened. High-pressure fuel is supplied, and high-pressure fuel is injected from the injector 9. That is, high-pressure injection is performed at an injection rate larger than the fuel injection rate at low-pressure injection. When the fuel injection ends, the on-off valve 7 for controlling the injection timing is closed, and the high-pressure fuel supplied from the fuel passage 10a to the pressure control chamber 11 through the orifice 15 is supplied to the needle valve 13 via the hydraulic piston 14. Acting, the needle valve 13 closes the nozzle 9a, and the fuel injection from the nozzle 9a ends. At the end of fuel injection, the fuel injection rate falls rapidly, and the amount of black smoke (smoke) and particulates (particulate matter PM) emitted from the engine is reduced. The switching valve 5 for switching the injection rate is closed at the same time as the closing of the on-off valve 7 at the fuel injection end timing, or is closed when a predetermined time has elapsed from the fuel injection timing end timing.

As shown in FIG. 5, between the fuel chamber 12 of the injector 9 and the switching valve 5 for switching the injection rate, high-pressure fuel in the fuel passage 10a passes through the orifice 6a of the fuel passage 10b to the low-pressure accumulator 4. As a result, the fuel pressure in the fuel passage 10a gradually decreases from the end of the fuel injection in each fuel injection cycle, and the pressure control is continued until the fuel injection in the next fuel injection cycle is started. Valve 3
The fuel pressure is reduced to the fuel pressure suitable for the low-pressure injection set by 4, and the injection rate in the next low-pressure injection becomes required.

As described above, when the pressure sensor 3a for detecting the fuel pressure of the high-pressure accumulator 3 fails when the signal output is in a low output (low pressure) state, as shown by a solid line in FIG. The fuel is injected at an injection pressure equal to or higher than the maximum injection pressure in the normal mode indicated by, increasing the injection amount,
Problems such as an increase in the maximum pressure in the cylinder and an increase in noise and vibration are caused. When the pressure sensor 4a for detecting the fuel pressure of the low-pressure accumulator 4 fails when the signal output is in a low output (low pressure) state, as shown by a one-dot chain line in FIG. The maximum injection pressure (indicated by a dotted line) in the mode is reached, the injection amount increases, and an overload operation is performed. Thus, the pressure sensor 3 for detecting the fuel pressure of the high-pressure accumulator 3
If a or the pressure sensor 4a that detects the fuel pressure of the low-pressure accumulator 4 fails, the combination of low-pressure injection and high-pressure injection cannot be performed, and the injection amount becomes abnormal. FIG. 6 shows a fuel injection waveform when the pressure sensor 3a for detecting the fuel pressure of the high-pressure accumulator 3 and the pressure sensor 4a for detecting the fuel pressure of the low-pressure accumulator 4 fail when the signal output is low, respectively. 9 is a timing chart showing the driving of the switching valve 9 and the switching valve 5.

Therefore, in the accumulator type fuel injection device of the present invention, the electronic control unit 8 executes a failure judgment routine of the accumulator pressure sensor shown in FIG. 8 at a predetermined cycle. In the determination routine shown in FIG. 8, it is determined whether the pressure sensor 3a for detecting the fuel pressure of the high-pressure accumulator 3 is normal (Step S).
1) When the pressure is normal, it is determined whether the pressure sensor 4a for detecting the fuel pressure of the low-pressure accumulator 4 is normal (step S).
2) When the pressure sensor 4a is normal, the mode shifts to the normal control mode (step S4), and when it is determined in step S1 that the pressure sensor 3a is faulty, the mode shifts to the fault control mode (limp home mode) ( Step S
3).

In step S1, the failure of the pressure sensor 3a is determined by the electronic control unit 8 when the difference between the actual pressure of the high-pressure accumulator 3 from the pressure sensor 3a and the indicated pressure (set pressure) exceeds a certain fixed value. And a ratio between the average value of the absolute value of the time change rate of the pressure sensor 3a and the average value of the pressure sensor 3a during a certain period. That is,
(1) When the difference between the actual pressure of the high-pressure accumulator 3 and the indicated pressure continues for a certain fixed time or more, (2) the average value of the rate of change of the output of the pressure sensor 3a with respect to time and the average of the output during a certain fixed period When the ratio of the values is equal to or less than a certain value, it is determined that the pressure sensor 3a has failed when the two failure conditions are simultaneously satisfied.

FIG. 9 shows the relationship between the command pressure of the high-pressure accumulator 3 and the output (actual pressure) of the pressure sensor 3a. In FIG. 9, the solid line indicates a normal state (actual pressure = instruction pressure) of the pressure sensor 3 a, and an allowable value (hysteresis) is set on both sides of the pressure sensor 3 a to be the reference region I. The lower region II of the reference region I is a region where the actual pressure is smaller than the indicated pressure, and the upper region III is a region where the actual pressure is larger than the indicated pressure. Is satisfied. The electronic control unit 8 determines that the pressure sensor 3a falls under the failure condition (1st failure condition) of the above (1) when any one of the regions II and II continues for a certain fixed time or more. judge. Then, when it is determined that a failure has occurred in the region II or II for a certain fixed time or more, a failure of the pressure sensor 3a is reliably determined.

Further, as shown in FIG. 10, the electronic control unit 8 calculates the average of the absolute value of the rate of change of the output of the pressure sensor 3a with respect to time, Adp, and the average of the output of the pressure sensor 3a during a certain time Ts. The value is Ap and the ratio R (=
When (Ap / Adp) is equal to or smaller than a certain fixed value α (R <α), it is determined that the pressure sensor 3a corresponds to the failure condition (second failure condition) of (2). When the pressure sensor 3a is normal, the output value changes with time. The average value Adp of the absolute value of the rate of change of the output with respect to time and the average value Ap of the output are obtained.
Change as indicated by the dotted lines, but when abnormal, the output value becomes constant and does not change, and becomes as indicated by the solid line.
The dimension is made non-dimensional by dividing the average value Ap of the output by the average value Adp of the absolute value of the rate of change of the output with respect to time.
FIG. 10 shows the pressure sensor 4a at a certain time Ts.
4 shows an example of the average value Adp of the absolute value of the change rate of the output with respect to time and the average value Ap of the output of the pressure sensor 4a.

The pressure sensor 4a performed in step S2
Is exactly the same as the failure determination of the pressure sensor 3a of the high-pressure accumulator 3, and the description is omitted. 9 and 10, reference numeral 4a in parentheses is referred to. The electronic control unit 8 controls the pressure sensor 3a in step S3 in FIG.
In the failure control mode (limp home mode)
Fuel injection amount, injection pressure, pressure control valve 34 of low-pressure accumulator 4
Is controlled by switching each control map for the failure mode. That is, as shown by the solid line in FIG. 11, the fuel injection amount control limits the maximum injection amount and the maximum engine speed (maximum value) as shown by the solid line with respect to the normal mode (maximum value) shown by the dotted line. FIG. 11 is a characteristic diagram showing a relationship between the engine speed and the fuel injection amount.

Further, the electronic control unit 8 controls the maximum pressure (fuel pressure) of the high-pressure accumulator 3 to a predetermined pressure (hereinafter referred to as "set pressure") as shown by a solid line in FIG. This set pressure is
The pressure control valve 34 is held and controlled in the fully closed state, and the maximum pressure is determined by using the detection value of the pressure sensor 4a of the low-pressure accumulator 4 in the effective section of the pressure-feeding stroke of the plunger 21 (FIG. The maximum pressure of the adjusted discharge pressure is lower than the pressure (maximum pressure) of the high-pressure accumulator 3 during normal control and higher than the pressure (maximum pressure) of the low-pressure accumulator 4 during normal control, as indicated by the dotted line. The pressure is controlled to be equal to or less than the allowable withstand voltage of the accumulator 4. Thereby, the pressure of the high-pressure accumulator 3 =
It becomes the pressure of the low-pressure accumulator 4. By setting the maximum pressure (fuel pressure) of the high-pressure accumulator 3 to be equal to or less than the allowable withstand pressure of the low-pressure accumulator 4, damage to the low-pressure accumulator 4, fuel leakage, and the like are prevented. FIG. 12 is a characteristic diagram showing a relationship between the engine speed and each pressure (fuel pressure) of the high-pressure accumulator 3 and the low-pressure accumulator 4.

Further, the control of the injector 9 and the switching valve 5 is simplified by using the same map as in the normal control. Since the pressure of the high-pressure accumulator 3 is equal to the pressure of the low-pressure accumulator 4, the fuel is injected when the injector 9 is opened, and there is no delay in the injection timing with respect to the normal mode. Further, an increase in the in-cylinder pressure is prevented. FIG. 7 is a timing chart showing the fuel injection waveform and the driving of the injector 9 and the switching valve 5 in the failure mode of the pressure sensor 3a.

The pressure sensor 4a shown in step S2 of FIG.
In the failure control mode (limp home mode) of step S3 when the failure determination is made in the failure determination of (3), the maximum pressure (fuel pressure) of the high-pressure accumulator 3 is maintained and controlled with the pressure control valve 34 fully closed. At the same time, the pressure is controlled to be equal to or lower than the allowable withstand voltage of the low-pressure accumulator 4. Thus, the pressure of the high-pressure accumulator 3 = the pressure of the low-pressure accumulator 4. The other controls are exactly the same as those described above when the pressure sensor 3a fails.

As described above, the electronic control unit 8 determines whether the pressure sensor 3a for detecting the fuel pressure of the high-pressure accumulator 3 or the pressure sensor 4a for detecting the fuel pressure of the low-pressure accumulator 4 has failed. By performing appropriate control in the mode, engine overload operation, increase in cylinder pressure, increase in vibration noise, increase in exhaust temperature, and the like can be suppressed, and the vehicle can travel to a repair shop by itself.

[0033]

According to the present invention, the average value of the absolute value of the rate of change with time of the output of the fuel pressure detecting means for detecting the fuel pressure in the accumulator for storing pressurized high-pressure fuel and the fuel detection When the ratio of the output of the means to the average value is equal to or less than a predetermined value, and when the difference between the output value of the fuel pressure detecting means and the set pressure of the accumulator is equal to or more than a predetermined value, it is determined that the fuel pressure detecting means has failed. Thus, it is possible to appropriately control the engine in the limp home mode in which the engine operation area is limited, and it is possible to avoid failure of the engine and the vehicle.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a pressure accumulating fuel injection device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing connection between main elements of the fuel injection device shown in FIG. 1 and injectors of each cylinder of the engine.

FIG. 3 is a schematic view of the high-pressure fuel pump shown in FIG.

FIG. 4 is a diagram showing a change in the injection rate over time and a change in each open / close state of a switching valve for switching the injection rate and an on-off valve for controlling the injection timing in one fuel injection cycle performed in the normal mode. is there.

FIG. 5 is a diagram showing a change in fuel pressure in a fuel passage between an injector and a switching valve over time in one fuel injection cycle performed in a normal mode.

FIG. 6 is a timing chart showing a fuel injection waveform and driving of an injector and a switching valve when a pressure sensor of a high-pressure accumulator or a pressure sensor of a low-pressure accumulator fails.

FIG. 7 is a timing chart showing the fuel injection waveform and the driving of the injector and the switching valve in the failure mode of the pressure sensor of the high-pressure accumulator and the pressure sensor of the low-pressure accumulator.

FIG. 8 is a flowchart of a pressure sensor failure determination routine of the high-pressure accumulator and the low-pressure accumulator of the accumulator-type fuel injection device shown in FIG.

FIG. 9 is a characteristic diagram showing one of the failure determination conditions of the pressure sensor of the high-pressure accumulator, and showing the relationship between the indicated pressure of the high-pressure accumulator and the output (actual pressure) of the pressure sensor.

FIG. 10 is a graph showing one of the failure determination conditions of the pressure sensor of the accumulator, and showing a change in the output of the pressure sensor.

FIG. 11 is a characteristic diagram showing a relationship between an engine speed and a fuel injection amount.

FIG. 12 is a characteristic diagram showing a relationship between an engine speed and pressures (fuel pressures) of high-pressure and low-pressure accumulators.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 high-pressure fuel pump 3 high-pressure accumulator (first accumulator) 4 low-pressure accumulator (second accumulator) 3a pressure sensor (first fuel pressure detecting means) 4a pressure sensor (second fuel pressure detecting means) 5 high-pressure / low-pressure accumulator (Fuel injection rate) Switching valve (first control valve) 7 Injection timing control opening / closing valve 8 Electronic control device (control means) 9 Injector (fuel injection nozzle) 10a, 10b Fuel passage 20 Plunger pump 21 Plunger 22 Cam 34 Low pressure accumulator pressure control valve (second control valve)

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) F02M 63/00 F02M 63/00 CF term (reference) 3G066 AA07 AB02 AC09 AD12 BA24 BA25 BA28 CA01S CA04U CA09 CA20U CB07U CB09 CB11 CB12 CB16 CC06T CC08T CC14 CC26 CC64T CC66 CC67 CC68U CC70 CD25 CD26 CE02 DA12 DA14 DA16 DC04 DC09 DC18 3G301 HA02 HA04 HA06 JA24 JA25 JB01 JB08 LB11 LB16 LB17 LC01 LC08 MA11 MA27 MA28 NA01 NA05 NA06 NA08 ND02 NE26 PB08

Claims (1)

[Claims] An accumulator storing pressurized fuel, a fuel passage extending from the accumulator toward a cylinder of an engine, and a fuel passage connected to an end of the fuel passage and supplying fuel to a combustion chamber of the cylinder. A fuel injection nozzle for injecting the fuel pressure, a fuel pressure detecting means for detecting a fuel pressure in the accumulator, an average value of an absolute value of a change rate of the output of the fuel pressure detecting means with respect to time, and an average value of an output of the fuel detecting means. And a determining means for determining that the fuel pressure detecting means has failed when a difference between the output pressure of the fuel pressure detecting means and a set pressure of the accumulator is equal to or more than a predetermined value. An accumulator type fuel injection device characterized by the above-mentioned.