JP2003278586A - Accumulator type fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accumulator type fuel injection device, coping with enforcement of regulation of exhaust gas and improvement in engine output without decrease in injection quantity, lowering of drivability and increase in cost by restraining excessive rise of an injector temperature caused by increase in common rail pressure. <P>SOLUTION: According to a difference between an injector temperature and a designated value, a common rail pressure detected by a sensor and a characteristic chart, a coefficient of current correction (current value correction amount: Ik) is calculated. When the common rail pressure is higher (A) as compared with the lower value in the low pressure time (B), the coefficient of current correction (Ik) is set to be lowered more largely than that (Ik=1.0) in the normal time. As described above, when the injector temperature exceeds a designated value, a driving current value to a solenoid coil of the injector is lowered to restrain the heating value of the solenoid coil. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation fuel injection device provided with an electromagnetic fuel injection valve for injecting high-pressure fuel into each cylinder of an internal combustion engine, and more particularly to an electromagnetic valve for the pressure-accumulation fuel injection device. The present invention relates to a method for controlling an injector drive current capable of suppressing an excessive rise in temperature of a fuel injection valve.

[0002]

2. Description of the Related Art Conventionally, a supply pump is used to pressurize high-pressure fuel into a pressure-accumulation container to accumulate the pressure, and the high-pressure fuel accumulated in the pressure-accumulation container is electromagnetically mounted on each cylinder of an internal combustion engine. 2. Description of the Related Art A pressure accumulation type fuel injection system is known in which fuel is distributed and supplied to a fuel injection valve (injector), and high-pressure fuel is injected from an injector of each cylinder to each cylinder of an internal combustion engine at a predetermined timing. Here, the injector drives the fuel injection nozzle that injects fuel to each cylinder of the internal combustion engine by lifting the nozzle needle from the valve seat of the nozzle body, and drives the nozzle needle in the valve opening direction (the side on which fuel injection is performed). And an urging means such as a spring for urging the nozzle needle in the valve closing direction. As the actuator, an electromagnetic actuator for controlling the pressure in the back pressure control chamber of the nozzle needle, for example, a solenoid valve having a valve element that operates to reduce the pressure in the back pressure control chamber when a drive current flows through the solenoid coil is used. Is generally adopted (for example, see Patent Document 1).

It should be noted that, for example, fuel leaked from the injector is discharged from the sliding parts in the injector and the back pressure control chamber to the outside through the solenoid coil in order to cool the heat generating parts such as the solenoid coil. It is discharged and returned to the fuel tank via the fuel return path. Further, the injector is configured to prevent fuel from leaking out of the system by a sealing means such as a rubber seal or a metal seal.

[0004]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-228998 (page 1-18, FIGS. 1 to 20)

[0005]

However, as a future trend of the pressure-accumulation fuel injection system, as shown in the graph of FIG. 10, measures for strengthening exhaust gas regulations and further improving engine output (output increase) are taken. As a result, there is a further increase in common rail pressure. However, with such a high pressure, as shown in the graph of FIG. 11, the injector temperature (or the injector leak temperature) becomes high due to the rise of the fuel temperature (the inlet temperature of the supply pump), and the rubber seal or It is difficult to secure the heat resistance reliability of the insulation film of the solenoid coil. In particular,
The injector temperature (or the injector leak temperature) may exceed the rubber allowable temperature during continuous operation at an engine output point and a high common rail pressure.

At this time, the injection amount of the fuel injected and supplied to each cylinder of the internal combustion engine is reduced or the common rail pressure is reduced to lower the fuel temperature and lower the injector temperature (or injector leak temperature). A possible method is to ensure the heat resistance reliability of the rubber seals and insulation coatings of solenoid coils, but in this case, the output of the internal combustion engine is actually reduced, and the drivability of a vehicle equipped with an accumulator fuel injection system There is a problem that (driving performance) is deteriorated.

A fuel cooler may be mounted for the purpose of lowering the fuel temperature as the common rail pressure further increases, but in this case, the cost increases due to an increase in the number of parts. Also, in order to improve the heat resistance reliability inside the injector, it is conceivable to make all the seal parts heat resistant, that is, metal seals, but in this case, metal seals are much more accurate than rubber seals. Since it is necessary to manufacture the product and the cost of the product itself is much higher than that of the rubber seal, it is hard to say that making all the heat resistant seals a heat resistant seal is the optimum means.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to suppress an excessive increase in injector temperature or injector leak temperature that rises as the pressure in the accumulator increases, thereby reducing the injection amount or the output of the internal combustion engine. Another object of the present invention is to provide a pressure-accumulation fuel injection device that can realize a higher pressure in the pressure accumulator without increasing the cost.

[0009]

According to the invention described in claim 1, when the injector temperature or the injector leak temperature detected or estimated by the temperature detecting means exceeds a predetermined value, the injector is compared with the injector at the normal time. By correcting the energization state to the injector on the side that suppresses the heat generation amount, it is possible to suppress an excessive rise in the injector temperature or injector leak temperature that rises as the pressure inside the pressure accumulator increases. As a result, the injector temperature or the injector leak temperature can be suppressed to be equal to or lower than the upper limit value capable of ensuring the heat resistance reliability of the injector.
Therefore, the pressure in the pressure accumulator can be further increased without reducing the injection amount, the output of the internal combustion engine, or the cost.

According to the second aspect of the present invention, when the injector temperature or the injector leak temperature detected or estimated by the temperature detecting means exceeds a predetermined value, the drive signal applied to the injector is higher than that in the normal time. By lowering the current value, it is possible to suppress the amount of heat generated by the injector, and thus it is possible to suppress an excessive increase in injector temperature or injector leak temperature that rises as the pressure inside the pressure accumulator increases. Further, according to the invention described in claim 3, when the current value of the drive signal is lowered as compared with the normal time, the pressure in the pressure accumulator detected by the pressure detection means is lower than that when the pressure is low. When the pressure in the pressure accumulator is higher, the injector temperature or injector leak temperature can be prevented from rising excessively by greatly reducing the pressure at high pressure.

According to the invention described in claim 4, the injector is a nozzle needle for opening and closing the injection hole, a pressure control chamber for controlling the operation of the nozzle needle, and a nozzle needle for reducing the pressure in the pressure control chamber. Is provided with an actuator for driving the valve in the valve opening direction and a biasing means for biasing the nozzle needle in the valve closing direction. According to the invention described in claim 5, when the actuator is applied with a drive signal for driving the valve body and the injector for switching between the communication state and the cutoff state of the pressure control chamber and the fuel return path. It has a solenoid coil that sucks the valve element to communicate with the pressure control chamber and the fuel return path. The actuator is configured so that leaked fuel leaking from the injector is discharged from each sliding portion in the injector and the pressure control chamber to the outside through the periphery of the solenoid coil, and is returned to the fuel tank via the fuel return path. It is characterized by

According to the sixth aspect of the invention, when the correction for lowering the current value of the drive signal is performed and the pressure in the accumulator is a low pressure below a predetermined value, the fuel set by the injection timing calculating means is set. By providing the injection timing correction means for correcting the injection timing in the advance direction, the actual injection amount injected and supplied from the injector of each cylinder to each cylinder of the internal combustion engine can be brought close to the target injection amount. The output reduction of the engine can be suppressed. Further, according to the invention of claim 7, when the correction for reducing the current value of the drive signal is carried out, the injection timing correction means for correcting the fuel injection timing set by the injection timing calculation means in the advance direction. Since the actual injection amount injected and supplied from the injector of each cylinder to each cylinder of the internal combustion engine can be brought close to the target injection amount, the decrease in the output of the internal combustion engine can be suppressed.

According to the eighth aspect of the present invention, when a pulsed drive current is applied to the injector, the solenoid coil is energized at the maximum charge current value when the injector is opened. Then, the solenoid coil is energized at a first drive current value lower than the charge current value until a predetermined time elapses, and then the first drive current is passed after the predetermined time elapses until the injector is closed. By energizing the solenoid coil at a second driving current value lower than the above value, the nozzle needle of the injector is surely opened by the charging current value and the first driving current value, and the nozzle nozzle of the injector is operated by the second driving current value. The valve open state of the needle can be maintained. Further, according to the invention described in claim 9, when the current value of the pulsed drive current is reduced as compared with the normal time, the first drive current value is set to be the normal time rather than the second drive current value. By significantly lowering it, it is possible to prevent the holding force for holding the valve open state of the injector from decreasing.

According to the tenth aspect of the present invention, when the pressure in the accumulator detected by the pressure detecting means exceeds a predetermined value, the predetermined drive signal stored by the current value storing means is stored. By correcting the current value of the drive signal applied to the injector so as to be lower than the basic current value, it is possible to suppress the heat generation amount of the injector and prevent the injector from becoming hot. Therefore, the pressure in the pressure accumulator can be further increased without reducing the injection amount, the output of the internal combustion engine, or the cost.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on examples with reference to the drawings. [Structure of First Embodiment] FIGS. 1 to 7 show a first embodiment of the present invention. FIG. 1 is a view showing the entire structure of a common rail fuel injection system, and FIG. 2 is a two-way valve type. It is the figure which showed the injector with a solenoid valve.

The common rail type fuel injection system of this embodiment includes a supply pump 3 which is rotatably driven by an internal combustion engine (hereinafter referred to as an engine) 1 such as a four-cylinder diesel engine, and a high-pressure fuel discharged from the supply pump 3. Common rail 4, which is a type of surge tank that stores pressure,
The high pressure fuel accumulated in the common rail 4 is used for the engine 1
Of a plurality of injections (4 in this example) into the combustion chamber of each cylinder
Injectors with two-way valve solenoid valve (hereinafter abbreviated as injectors) 5, and an electronic control unit (hereinafter E) for electronically controlling the supply pump 3 and a plurality of injectors 5.
Called CU) 10.

The supply pump 3 is a well-known feed pump (low-pressure supply pump) that pumps the fuel in the fuel tank 6 by rotating the pump drive shaft 32 with the rotation of the crankshaft 31 of the engine 1. A pump chamber into which the fuel sucked by the feed pump flows, a plunger (not shown) driven by the pump drive shaft 32, and a pressurizing chamber that pressurizes the fuel flowing from the pump chamber by the reciprocating motion of the plunger. (Plunger room). The supply pump 3 is a high-pressure supply pump (fuel supply pump) that pressurizes the fuel and discharges the high-pressure fuel from the discharge port to the common rail 4. In the fuel passage from the pump chamber of the supply pump 3 to the pressurizing chamber, an intake metering valve 7 as an electromagnetic actuator for opening and closing the fuel passage is attached.

The intake metering valve 7 is electronically controlled by a pump drive signal from the ECU 10 via a pump drive circuit (not shown) to adjust the intake amount of fuel sucked into the pressurizing chamber of the supply pump 3. The intake pressure adjusting solenoid valve changes the injection pressure supplied from each injector 5 to the engine 1, that is, the common rail pressure. The suction metering valve 7 is a normally open type pump flow control valve in which the valve state is fully opened when the energization is stopped.

The common rail 4 is required to continuously accumulate a high pressure (common rail pressure) corresponding to the fuel injection pressure. For this reason, the discharge port of the supply pump 3 for discharging the high pressure fuel through the fuel pipe 33. Connected with. The fuel pipe 33 that forms the high-pressure fuel flow path inside
Alternatively, a pressure limiter 34 that opens when the common rail pressure exceeds the limit set pressure is provided between the common rail 4 and the relief pipe 35 that forms the fuel return path therein, and the common rail pressure is higher than the limit set pressure. To prevent it from becoming. Further, the leaked fuel from the supply pump 3 is returned to the fuel tank 6 through a leak pipe 36 that forms a fuel return passage (leakage fuel passage) inside.

The injector 5 mounted on each cylinder of the engine 1 is connected to the downstream ends of a plurality of branch pipes (high pressure fuel flow paths) 39 branched from the common rail 4,
Fuel injection nozzle 11 for injecting high-pressure fuel into the combustion chamber of each cylinder, and a two-way valve solenoid valve as an electromagnetic actuator for driving a nozzle needle 13 housed in the fuel injection nozzle 11 in a valve opening direction. (Hereinafter abbreviated as solenoid valve)
12 and an urging means (not shown) such as a return spring for urging the nozzle needle 13 in the valve closing direction. The fuel injection nozzle 11 has a plurality of injection holes 16
Nozzle needle 13 for opening and closing, this nozzle needle 1
3 and a command piston 14 that operates in conjunction with the nozzle piston 15, and a nozzle body 15 that accommodates them.
Here, 17 is a fuel pool to which high-pressure fuel is constantly supplied,
18 is a fuel reservoir 17 and a back pressure control chamber (pressure control chamber)
A fuel passage (high-pressure passage) for supplying high-pressure fuel to 19, and 20 and 21 are inlet-side and outlet-side orifices (fixed throttle) for adjusting the flow rate of the passing fuel.

The solenoid valve 12 includes a vehicle-mounted power source 22 and a normally open type switch 23 incorporated in an injector drive circuit (EDU).
Solenoid coil 24 electrically connected through the solenoid coil 24, a valve body 25 with an armature that is attracted upward in the drawing by the magnetomotive force of the solenoid coil 24, and the valve body 25.
Is constituted by a return spring 26 for urging the valve in the valve closing direction. The injector 5 to the fuel tank 6
The leaked fuel leaks to the outside from the fuel outlets 28 through the sliding portions in the injector 5 and the back pressure control chamber 19 through the fuel passages 27 that surround the circumference of the solenoid coil 24, and the fuel return passages inside. It is configured to flow back to the fuel tank 6 through a leak pipe 37 that forms a (leak fuel flow path) (see FIGS. 1 and 2).

The injection of fuel from the injector 5 of each cylinder to the engine 1 is electronically controlled by a solenoid valve control signal to an injector drive circuit (EDU) that drives the solenoid valve 12. Then, the injector drive circuit (ED
U) is applied to the solenoid coil 24 of the solenoid valve 12 of the injector 5 of each cylinder by an injector drive signal (hereinafter referred to as an injector injection pulse) and the solenoid valve 12 is opened, the nozzle needle 13 is seated. By further lifting (separating), the injection hole 16 and the fuel pool 17
Communicates with. As a result, the high-pressure fuel accumulated in the common rail 4 is injected and supplied into the combustion chamber of each cylinder of the engine 1.

The ECU 10 has a CPU for performing control processing and arithmetic processing, and an RO for storing various programs and data.
A microcomputer having a well-known structure including functions of a storage device (memory) such as M and RAM, an input circuit, an output circuit, a power supply circuit, an injector drive circuit (EDU), and a pump drive circuit is provided. . The sensor signals from the various sensors are A / D converted by the A / D converter and then input to the microcomputer.

The ECU 10 calculates the optimum fuel injection pressure according to the operating conditions of the engine 1, that is, the common rail pressure, and drives the intake metering valve 7 of the supply pump 3 via a pump drive circuit (not shown). It is also a quantity control means. That is, the ECU 10 controls the rotation speed sensor 41.
Engine operating information such as the engine speed (NE) detected by the engine and the accelerator opening (ACCP) detected by the accelerator opening sensor 42, and the engine cooling water temperature (TH detected by the cooling water temperature sensor 43).
W) and the fuel temperature (THL) detected by the fuel temperature sensor 44 are added to calculate the target common rail pressure (Pt), and the target common rail pressure (Pt) is calculated according to the pressure difference between the common rail pressure (PC) and the target common rail pressure (Pt). A pump drive signal is output to the suction metering valve 7 of the supply pump 3 based on the target pump pressure feed rate.

Furthermore, more preferably, for the purpose of improving the injection amount accuracy, the common rail pressure (P) corresponding to the fuel injection pressure injected and supplied from each injector 5 to the engine 1.
The common rail pressure sensor 45 as a pressure detecting means for detecting C) is attached to the common rail 4, and the common rail pressure (PC) detected by the common rail pressure sensor 45 is a target common rail pressure (Pt) determined by the operating conditions of the engine 1. It is desirable to perform feedback control of the pump drive signal (drive current) to the intake metering valve 7 so as to substantially match with (1). The drive current to the intake metering valve 7 is preferably controlled by duty. That is, by using duty control for adjusting the on / off ratio (energization time ratio / duty ratio) of the pump drive signal per unit time to change the valve opening degree or the valve opening time ratio of the intake metering valve 7. , High precision digital control becomes possible.

Then, the ECU 10 calculates the optimum injection amount (Q) according to the operating condition of the engine 1, and an optimum injection amount calculating means according to the operating condition of the engine 1 and the target injection amount (Q). Injection timing calculation means for calculating the fuel injection timing (T) and injection pulse calculation means for calculating the injection pulse time (injection period, injection pulse width: Tq) according to the operating conditions of the engine 1 and the target injection amount (Q). The injection pulse width (T) is applied to the solenoid valve 12 of the injector 5 via the (injection period calculation means) and the injector drive circuit (EDU).
q) injector (INJ) injection pulse (driving current)
And an injector drive means for applying the voltage.

That is, the ECU 10 controls the engine speed (hereinafter referred to as engine speed: NE) detected by the speed sensor 41 and the accelerator opening sensor 42.
Target injection amount (basic injection amount: Q) based on engine operation information such as accelerator opening (ACCP) detected by
Is calculated and the fuel injection timing (energization start timing, injection start timing: T) is calculated based on the engine speed (NE) and the target injection amount (Q), and the common rail pressure (PC) and the target injection amount (Q) are calculated. The injection pulse width (Tq) is calculated in accordance with the above, and the injector (INJ) injection pulse is applied to the solenoid valve 12 of the injector 5 of each cylinder. As a result, the engine 1 is operated.

The ECU 10 of this embodiment includes a temperature detecting means (injector temperature estimating means) for estimating the injector temperature (or injector leak temperature) and the estimated injector temperature (or injector leak temperature).
However, do not exceed the resin allowable temperature (upper limit value: TLimit) such as the allowable film temperature and the allowable rubber temperature that can ensure the heat resistance reliability of the insulating film and the rubber seal of the solenoid coil 24 of the injector 5. In addition, the energization state correction means (current value correction) for lowering the current value of the injector (INJ) injection pulse applied to the solenoid valve 12 of the injector 5 when the predetermined value (Tmax) or more is preset Means) and. Note that Tmax
<TLimit.

In addition, the injector (IN
J) When lowering the current value of the injection pulse, as shown in the timing chart of FIG. 3, the common rail pressure (PC) detected by the common rail pressure sensor 45 is higher at high pressure than at low pressure. I am trying to lower it. Further, when the common rail pressure (PC) detected by the common rail pressure sensor 45 is a low value equal to or lower than a predetermined value, the ECU 10 sets the fuel injection timing (energization start timing: T) as shown in the timing chart of FIG. Is provided in the advance direction by an injection timing correction amount (α).

Here, in this embodiment, the target injection amount (Q) and the fuel injection timing (T) are determined by using the rotation speed sensor 41 and the accelerator opening sensor 42 as the operating condition detecting means for detecting the operating condition of the engine 1. Is calculated from other sensors (for example, cooling water temperature sensor 43, fuel temperature sensor 44, intake temperature sensor, intake pressure sensor, cylinder discrimination sensor, injection timing sensor, etc.) as operating condition detecting means. The target injection amount (Q) and the fuel injection timing (T) may be corrected in consideration of the detection signal (engine operation information).

[Control Method of First Embodiment] Next, a method of controlling the injector drive current of the present embodiment will be briefly described with reference to FIGS. 1 to 7. Here, FIG. 5 is a flowchart showing an outline of the method for controlling the injection amount of the injector.

First, engine parameters such as engine speed (NE), accelerator opening (ACCP), engine cooling water temperature (THW) and fuel temperature (THL) are fetched (step S1). Next, the injection amount command value (target injection amount: Q) is calculated based on the above engine parameters. Specifically, the target injection amount (Q) is calculated based on the engine speed (NE) and the accelerator opening (ACCP) captured in step S1 and stored in a storage device (memory) or the like (step S2). ). The target injection amount (Q) is
The engine cooling water temperature (THW) detected by the cooling water temperature sensor 43 or the fuel temperature (THL) detected by the fuel temperature sensor 44 may be corrected. Next, the fuel injection timing (T) is calculated based on the above engine parameters. Specifically, the fuel injection timing (energization start timing) is determined based on the engine speed (NE) captured in step S1 and the target injection amount (Q) or accelerator opening (ACCP) set in step S2. : T) is calculated and stored in a storage device (memory) or the like (step S3).

Next, the injector temperature (or injector leak temperature) is recognized. Specifically, an injector temperature sensor is attached to the injector 5 to detect the actual injector temperature (or injector leak temperature) by the injector temperature sensor, or a fuel temperature detected by the fuel temperature sensor 44 (of the supply pump 3). Inlet temperature: THL), engine speed (NE) detected by the rotation speed sensor 41, common rail pressure (P) detected by the common rail pressure sensor 45.
C) or the target common rail pressure (Pt), the target injection amount (Q), and the injector temperature (or injector leak temperature) are estimated from the duration (elapsed time) during high load operation. Here, the detected or estimated injector temperature (or injector leak temperature) is set as T1 and stored in a storage device (memory) or the like (step S4).

Next, it is determined whether or not the current value correction processing is executed.
That is, whether or not the detected or estimated injector temperature (or injector leak temperature) T1 exceeds a predetermined value (Tmax) capable of ensuring the heat resistance reliability of the insulating film or the rubber seal of the solenoid coil 24 of the injector 5. It is determined (step S5). If the determination result is NO, the common rail pressure (PC) is recognized. That is, the common rail pressure (PC) detected by the common rail pressure sensor 45 is taken in (step S
6).

Next, based on the engine parameters and the target injection amount (Q), the injector (IN
J) The ejection pulse width (ejection pulse time, energization period: Tq) of the ejection pulse is calculated. Specifically, the injector (INJ) is based on the common rail pressure (PC) captured in step S6 or step S22 described below and the target injection amount (Q) set in step S2.
The ejection pulse width (Tq) of the ejection pulse is calculated and stored in a storage device (memory) or the like (step S7). Next, the injector (INJ) injection pulse is set at the output stage of the ECU 10 (step S8). Then, it returns to the first step S1 and repeats each above-mentioned arithmetic processing and control processing.

Although not described in the flow chart of FIG. 5, the supply pump 3 is arranged so that the common rail pressure (PC) detected by the common rail pressure sensor 45 is substantially equal to the target common rail pressure (Pt). The amount of fuel discharged to the common rail 4 is feedback-controlled. Specifically, the valve opening degree of the intake metering valve 7 of the supply pump 3 is set to a pressure deviation value (ΔP = (P) between the common rail pressure (PC) and the target common rail pressure (Pt).
t-PC)), the opening command value (Di) of the intake metering valve 7 is calculated, and the opening command value (Di) of the intake metering valve 7 is set in the output stage of the ECU 10. To do.

When the result of the determination in step S5 is YES, that is, the detected or estimated injector temperature (or injector leak temperature) T1 is the predetermined value (Tma).
x) is exceeded, the current value correction amount calculation process shown in the routine of FIG. 6 is performed (step S9), and subsequently, the injection timing correction amount calculation process shown in the routine of FIG. 7 is performed. (Step S10). After that, step S7
In step S8, the injection pulse width (Tq) of the injector (INJ) injection pulse is calculated, and in step S8, the injector (INJ) in which the current correction coefficient (current value correction amount: Ik) set in step S23 described later is taken into consideration. ) The injection pulse is set at the output stage of the ECU 10. Then, it returns to the first step S1 and repeats each above-mentioned arithmetic processing and control processing.

Here, FIG. 6 is a flow chart showing a method for calculating a current value correction amount. When the routine of FIG. 6 is entered, the temperature difference (ΔT) between the injector temperature (or injector leak temperature) T1 and the predetermined value (Tmax) is calculated (step S21). Next, the common rail pressure (P
Recognize C). That is, the common rail pressure (PC) detected by the common rail pressure sensor 45 is taken in (step S22).

Next, the current correction coefficient (current value correction amount: Ik) is calculated based on the characteristic diagram of FIG. Specifically, a current correction coefficient (current value correction amount: Ik) is calculated from the temperature difference (ΔT) set in step S21 and the common rail pressure (PC) loaded in step S22, and the storage device (memory) is calculated. Etc. (step S23). After that, the routine exits the routine of FIG. 6 and proceeds to the routine of FIG.

In the process of calculating the current correction coefficient (Ik), the larger the temperature difference (ΔT), the more the current correction coefficient (Ik = 1.0) is stored in the storage device (memory) or the like. Ik) is set to be greatly lowered.
Further, as shown in the timing chart of FIG. 3 and the characteristic diagram of FIG. 6, when the common rail pressure (PC) captured in step S22 is high pressure (when PC is small) compared to when it is low pressure (when PC is small) The current correction coefficient (Ik) is
(k = 1.0).

Here, FIG. 7 is a flow chart showing a method for calculating the injection timing correction amount. When entering the routine of FIG. 7, first, the current correction coefficient (Ik) and the common rail pressure (PC) set in the above step S23 are recognized. That is, the common rail pressure (PC) detected by the common rail pressure sensor 45 is taken in (step S3).
1). Next, the injection timing correction amount (α) is calculated based on the characteristic diagram of FIG. 7. Specifically, the injection timing correction amount (α) is calculated from the current correction coefficient (Ik) and the common rail pressure (PC), and the injection timing correction amount is set to the fuel injection timing (T) set in step S3. The final fuel injection timing (T) in consideration of (α) is calculated and stored in a storage device (memory) or the like (step S32). After that,
Exit the routine.

In the process for calculating the injection timing correction amount (α), the smaller the current correction coefficient (Ik) is, the more the fuel injection timing (T) is set to be advanced compared to the normal time. Further, as shown in the timing chart of FIG. 4 and the characteristic chart of FIG. 7, the injection timing correction is performed when the common rail pressure (PC) captured in step S31 is low pressure (PC large) compared to high pressure (PC large). The quantity (α) is set so as to be greatly advanced.

[Operation of First Embodiment] Next, the operation of the common rail fuel injection system of this embodiment will be described with reference to FIGS.
A brief description will be given based on. Here, FIG. 2A is a diagram showing a non-injection state of the injector 5 of a specific cylinder (for example, # 1 injection cylinder) of the engine 1.

The fuel injection from the injector 5 of each cylinder of the engine 1 to the engine 1 is specified when the fuel injection timing (T) to a specific cylinder of the engine 1 comes, as shown in FIG. 2B. The normally open switch 23 in the injector drive circuit (EDU) corresponding to the injector 5 of the cylinder is closed, and the solenoid coil 24 of the solenoid valve 12 of the injector 5 of the specific cylinder is supplied with the current waveform shown by the solid line in FIG. 3, for example. Pulsed drive current, that is, the injector (IN
J) When the injection pulse is applied, the valve body 25 of the solenoid valve 12
Opens.

At this time, the injector drive circuit (ED
When the electromagnetic valve control signal of the specific cylinder is applied from the ECU 10, U) applies an injector injection pulse (pulse-shaped injector drive signal) to the solenoid coil 24 of the electromagnetic valve 12 of the injector 5 of the specific cylinder. For example, in FIG.
As shown by the solid line (normal time) in the timing chart of No. 1, first, the nozzle needle 1 of the injector 5 of the specific cylinder is
Charge current value (Io: 15 to 20 for example) which is the highest current value (peak current value) required to open
The solenoid coil 24 is energized by A).

After that, the solenoid coil 24 is energized by the first drive current value (Ia: 10 A, for example) required to open the nozzle needle 13 until a predetermined time elapses. Then, after the elapse of a predetermined time until the nozzle needle 13 is closed, the nozzle needle 1
The second drive current value (I
b: The solenoid coil 24 is energized by, for example, 5A. However, Io>Ia> Ib.

Valve body 2 with armature of this solenoid valve 12
While the valve 5 is open, the fuel in the back pressure control chamber 19 passes through the outlet side orifice 21 and the fuel flow path 27 and the fuel outlet 28.
After being discharged to the outside of the solenoid valve 12 after passing through, the gas is returned (leaked) to the fuel tank 6 through the leak pipe 37.
The nozzle needle 13 lifts (separates) from the valve seat of the nozzle body forming the nozzle body 15 by overcoming the urging force of the return spring (not shown). As a result, the injection hole 16 and the fuel sump 17 communicate with each other, so that the high-pressure fuel accumulated in the common rail 4 is injected and supplied into the combustion chamber of each cylinder of the engine 1.

Thereafter, the injection pulse time (injection pulse width: Tq) elapses from the fuel injection timing (injector injection pulse start timing: T) at which the output of the injector (INJ) injection pulse is started, and then the injector (INJ) injection pulse When the injector (INJ) injection pulse end timing at which the output of the
When the normally open switch 23 of U) is opened, the valve body 25 of the solenoid valve 12 is closed as shown in FIG.

While the valve body 25 of the solenoid valve 12 is closed, the high pressure fuel is filled from the fuel passage (high pressure passage) 18 through the inlet side orifice 20 into the back pressure control chamber 19, so that a return is made. The nozzle needle 13 is seated on the valve seat of the nozzle body forming the nozzle body 15 by the urging force of the spring. As a result, the injection hole 16 and the fuel pool 17
Since the communication state with is cut off, the fuel injection into the combustion chamber of the specific cylinder of the engine 1 ends.

[Characteristics of First Embodiment] As described above, in the common rail fuel injection system of the present embodiment, the detected or estimated injector temperature (or injector leak temperature) T1 exceeds the predetermined value (Tmax). If it is, the temperature difference (ΔT) between the injector temperature (or injector leak temperature) T1 and the predetermined value (Tmax)
And the current correction coefficient (current value correction amount: Ik) is calculated based on the calculated temperature difference (ΔT), common rail pressure (PC) and the characteristic diagram of FIG.

At this time, as shown in the characteristic diagram of FIG.
The current correction coefficient (Ik) is set to be much lower than the normal time (Ik = 1.0) when the common rail pressure (PC) is low (when PC is small) compared to when it is low (when PC is large). . Therefore, when the common rail pressure (PC) is low (P
When C is small: B), an injector (INJ) injection pulse is applied to the solenoid coil 24 of the solenoid valve 12 of the injector 5, as indicated by the dashed line in the timing chart of FIG. Specifically, first, the charge current value (I
o: For example, 15 to 20 A) by solenoid coil 2
4 is energized, and until a predetermined time elapses thereafter,
The second drive current value (Ib × Ik: 4A, for example) is supplied to the solenoid coil 24 by the first drive current value (Ia × Ik: 8A), for example, until the nozzle needle 13 is closed after a predetermined time has elapsed. Thus, the solenoid coil 24 is energized. However, Io>Ia> Ib.

Further, when the common rail pressure (PC) is high (when PC is large: A), the injector (injector) is connected to the solenoid coil 24 of the solenoid valve 12 of the injector 5 as shown by the broken line in the timing chart of FIG. INJ) Apply an injection pulse. Specifically, first, the charge current value (I
o: For example, 15 to 20 A) by solenoid coil 2
4 is energized, and until a predetermined time elapses thereafter,
The second drive current value (Ib × Ik: 3 A) is supplied from the solenoid coil 24 by the first drive current value (Ia × Ik: 7 A) until the nozzle needle 13 is closed after a lapse of a predetermined time. Thus, the solenoid coil 24 is energized. However, Io>Ia> Ib.

Therefore, as a future trend of the common rail type fuel injection system, as shown in the graph of FIG. 10, the common rail pressure (PC) is taken as a measure for strengthening the exhaust gas regulation and further improving the engine output (output increase). When the pressure is further increased, as shown in the graph of FIG. 11, the injector temperature (or injector leak temperature) becomes high, and the injector temperature (or injector leak temperature) changes to the rubber seal or solenoid coil inside the injector 5. In some cases, the allowable temperature (TLimit) of rubbers such as the insulating film 24 is exceeded.

However, in this embodiment, when the preset value (Tmax) is exceeded, the drive current value to the solenoid coil 24 of the solenoid valve 12 of the injector 5 is reduced according to the common rail pressure (PC). As a result, the heat generation amount of the solenoid coil 24 of the injector 5 can be suppressed. Therefore, it is possible to suppress an excessive rise in the injector temperature (or injector leak temperature) that rises as the common rail pressure (PC) increases. Thereby, the injector temperature (or the injector leak temperature) is suppressed below the resin allowable temperature (upper limit value: TLimit) capable of ensuring the heat resistance reliability of the rubber seal in the injector 5 and the insulating film of the solenoid coil 24. You can

Therefore, the common rail pressure (P) can be obtained without reducing the fuel injection amount into each cylinder of the engine 1.
C) can be further increased in pressure, and exhaust gas regulations can be strengthened and engine output can be further improved (output increase). In the case of the present embodiment, since the engine output is not reduced, it is possible to prevent the drivability (driving performance) of the vehicle equipped with the common rail fuel injection system from being reduced. Further, in this embodiment, it is not necessary to mount a fuel cooler for the purpose of lowering the fuel temperature (THL) as the common rail pressure (PC) further increases, and the heat resistance reliability in the injector 5 is improved. For the purpose, it is not necessary to heat-resistant seal (metal seal) all of the sealing portions, and therefore, the cost does not increase.

Here, in the injector 5 of the back pressure control system, the fuel in the back pressure control chamber is configured to flow via the flow path that goes around the solenoid coil 24. In addition, the leak fuel tends to increase in temperature as the common rail pressure increases. Therefore, this high temperature leaked fuel is
There is a risk that the temperature may rise above the heat resistant limit temperature of the peripheral members including the solenoid coil 24. On the other hand, it can be said that the above-described correction for reducing the drive current value is a very suitable means for suppressing the heat generation amount of the solenoid coil 24 of the injector 5 of the back pressure control system. Further, in the injector 5 of the back pressure control system, the high pressure fuel is recirculated (leaked) from the back pressure control chamber 19 to the fuel tank 6 through the outlet side orifice 21, the fuel flow passage 27, the fuel outlet 28 and the leak pipe 37. Then, a force acts in a direction of lifting the nozzle needle 13 upward in the drawing.

That is, since the back pressure control chamber 19 withdraws the high-pressure fuel that exerts an oil pressure in the valve closing direction of the nozzle needle 13, a force acts in the valve opening direction of the nozzle needle 13, so that the common rail pressure (PC) is reduced. When the pressure is higher than the predetermined value, the nozzle needle 13 opens with a desired responsiveness even if the drive current value applied to the solenoid coil 24 of the solenoid valve 12 that drives the injector 5 is lowered as compared with the normal time. As shown in the timing chart of FIG. 4, even when the drive current value applied to the solenoid coil 24 of the solenoid valve 12 is lowered as compared with the normal time, the fuel injection timing (T) substantially equal to the normal time is obtained. Can be obtained.

However, when the common rail pressure (PC) is a low pressure of a predetermined value or less, the pressure in the back pressure control chamber 19 naturally decreases, so that the nozzle needle 13 acts in the direction of lifting upward in the figure. The power also becomes smaller. Then, if the application timing of the drive current value applied to the solenoid coil 24 of the solenoid valve 12 is set to the same timing (fuel injection timing) as in normal time, the broken line (current correction / no injection timing correction) is shown in the timing chart of FIG. ),
The actual injection amount may be significantly smaller than the target injection amount (Q), which may lead to a reduction in engine output.

Therefore, in the common rail fuel injection system of this embodiment, when the current correction coefficient (current value correction amount: Ik <1.0) is calculated as described above,
As indicated by the solid line (normal time) and the alternate long and short dash line (current correction / injection timing correction) in the timing chart of FIG. 4, the operating conditions of the engine 1 (engine speed: NE) and the target injection amount (Q) The fuel injection timing (T) set accordingly is advanced in the advance direction by the injection timing correction amount (α) from the normal time, so that the injector 5 of each cylinder is advanced.
Since the actual injection amount that is injected and supplied from the engine to each cylinder of the engine 1 can be made extremely close to the target injection amount (Q), it is possible to suppress the decrease in the engine output.

[Second Embodiment] FIGS. 8 and 9 show a second embodiment of the present invention, and FIG. 8 is a flow chart outlining an injector injection amount control method.

Here, steps S1, S2, S3, S9, S10, S7 and S8 of the flowchart of FIG.
Steps S1, S2, S3, S9 of the flowchart of
Corresponding to S10, S7, and S8, the same process is performed except the process of step S9. Therefore, description of each process in the flowchart of FIG. 8 is omitted.

Here, FIG. 9 is a flow chart showing a method for calculating the current value correction amount. When the routine of FIG. 9 is entered, the common rail pressure (PC) is recognized. That is, the common rail pressure (PC) detected by the common rail pressure sensor 45 is taken in (step S41). Next, FIG.
The current correction coefficient (current value correction amount: I
k) is calculated. Specifically, the current correction coefficient (current value correction amount: Ik) is calculated from the common rail pressure (PC) fetched in step S41 described above, and the storage device (memory) is calculated.
Etc. (step S42). After that, the routine exits the routine of FIG. 9 and proceeds to the routine of FIG. 7 of the first embodiment.

In the calculation process of the current correction coefficient (Ik), the common rail pressure (PC) is a predetermined value (for example, 100M).
Pa: PA) or more, a basic current value stored in advance in a storage device (memory), that is, a current value (I ×
Ik: However, current correction coefficient (Ik) rather than Ik = 1.0)
Is set to lower. Further, as shown in the characteristic diagram of FIG. 9, when the common rail pressure (PC) captured in step S41 is equal to or higher than a predetermined value, the common rail pressure (PC)
Becomes larger, the current correction coefficient (Ik) becomes
= 1.0). In addition,
In addition to common rail pressure (PC), fuel temperature, ambient temperature,
The current correction coefficient (current value correction amount: Ik) may be corrected in consideration of the engine speed and the like.

In the common rail fuel injection system of this embodiment, when the common rail pressure (PC) is higher than a predetermined value (for example, 100 MPa: PA), the valve opening assisting force of the nozzle needle 13 of the injector 5 becomes large. This is utilized to correct the driving current value applied to the solenoid coil 24 of the solenoid valve 12 of the injector 5 so as to be lowered. That is, even in the normal time described in the first embodiment (when the injector temperature or the injector leak temperature is a temperature equal to or lower than the predetermined value (Tmax)), the solenoid coil 24 of the solenoid valve 12 of the injector 5 is in accordance with the common rail pressure (PC). The drive current value applied to is corrected.

[Modification] In this embodiment, as an example of the injector for injecting and supplying the fuel to each cylinder of the engine 1,
Although the example in which the injector 5 with the two-way valve solenoid valve 12 is used has been described, an injector with a three-way valve solenoid valve and other types of injectors may be used. Also,
In this embodiment, the rotation speed sensor 41, the accelerator opening sensor 42, the cooling water temperature sensor 43, and the fuel temperature sensor 44.
Although the target common rail pressure (Pt) is calculated using, other sensors (for example, intake air temperature sensor,
The target common rail pressure (Pt) may be corrected by adding detection signals (engine operation information) from the intake pressure sensor, the cylinder discrimination sensor, the injection timing sensor, and the like.

In this embodiment, the common rail pressure sensor 45
Is attached directly to the common rail 4 to detect the fuel pressure (common rail pressure) accumulated in the common rail 4, but the pressure detecting means is provided from the plunger chamber (pressurizing chamber) of the supply pump 3 to the inside of the injector 5. Attach it to the fuel piping etc. up to the fuel passage and supply pump 3
The pressure of the fuel discharged from the pressurizing chamber may be detected.

In the present embodiment, the example in which the suction metering valve 7 for changing (adjusting) the suction amount of the fuel sucked into the plunger chamber (pressurizing chamber) of the supply pump 3 is provided is explained. A discharge metering valve for changing (adjusting) the amount of fuel discharged from the third plunger chamber (pressurizing chamber) to the common rail 4 may be provided. It should be noted that a normally open type solenoid valve may be used in which the valve opening degree of the intake adjustment valve 7 or the discharge adjustment valve is fully opened when the energization of the solenoid valve is stopped.
It is also possible to use a solenoid valve of the type in which the valve opening degree of the intake adjustment valve 7 or the discharge adjustment valve is fully opened when the solenoid valve is energized.

In this embodiment, when the current correction coefficient (current value correction amount: Ik <1.0) is calculated, the injection timing correction amount (α) is calculated, and the current value correction and the injection timing correction are performed simultaneously. However, when the current value of the drive signal is corrected to be lower and the common rail pressure (PC) is lower than a predetermined value, the operating conditions of the engine 1 and the target injection amount (Q)
The fuel injection timing (T) set in accordance with the above may be advanced in the advance direction by the injection timing correction amount (α) corresponding to the common rail pressure (PC). In addition, the injector (INJ) injection pulse (driving current) compared to the normal time
When the correction for reducing the current value is performed, the first drive current value may be set to be significantly lower than the second drive current value compared to the normal time. Further, the second drive current value may be set to the same current value as in the normal time, and only the first drive current value may be lowered as compared with the normal time. In this case, it is possible to prevent the holding force for holding the valve open state of the injector 5 from decreasing.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a common rail fuel injection system (first embodiment).

2 (a) to 2 (c) are explanatory views showing an operating state of an injector (first embodiment).

FIG. 3 is a timing chart showing a current waveform (example) of an injector injection pulse (first embodiment).

FIG. 4 is a timing chart showing a current waveform and an injection rate waveform of an injector injection pulse (first embodiment).

FIG. 5 is a flowchart showing a method for controlling the injection amount of the injector (first embodiment).

FIG. 6 is a flowchart showing a current value correction amount calculation method (first embodiment).

FIG. 7 is a flowchart showing an injection timing correction amount calculation method (first embodiment).

FIG. 8 is a flowchart showing a method for controlling the injection amount of the injector (second embodiment).

FIG. 9 is a flowchart showing a current value correction amount calculation method (second embodiment).

FIG. 10 is a graph showing the relationship between engine speed and common rail pressure.

FIG. 11 is a graph showing the relationship between the fuel temperature and the injector temperature.

[Explanation of symbols]

1 engine (internal combustion engine) 3 supply pumps (high-pressure supply pumps) 4 common rail 5 injectors 6 Fuel tank 10 ECU (temperature detection means, energization state correction means) 12 Solenoid valve (actuator) 13 nozzle needle 16 injection holes 19 Back pressure control room (pressure control room) 24 solenoid coil 25 valve body 26 Return spring 27 Fuel flow path 37 Leak piping (fuel return path) 44 Fuel temperature sensor (temperature detection means) 45 Common rail pressure sensor (pressure detection means)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayoshi Ito             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F term (reference) 3G066 AA07 AB02 AC09 BA31 BA41                       CC01 CD10 CE22 CE29 DB09                       DC01 DC15 DC18                 3G301 HA02 JA32 KA09 LB11 LC01                       NA08 NE01 NE06 NE17 NE19                       PB01Z PB08Z PG02Z

Claims (10)

[Claims] 1. A high-pressure fuel pressure-fed by a high-pressure supply pump is accumulated in a pressure accumulator container, and the high-pressure fuel accumulated in the pressure accumulator container is distributed and supplied to an injector mounted in each cylinder of an internal combustion engine. In the pressure-accumulation fuel injection device that supplies high-pressure fuel from the injector to each cylinder of the internal combustion engine when the injector is energized, (a) temperature detecting means for detecting or estimating an injector temperature or an injector leak temperature. (B) When the injector temperature or the injector leak temperature detected or estimated by the temperature detecting means exceeds a predetermined value, the injector is provided to the side that suppresses the heat generation amount of the injector as compared with the normal time. And a current-carrying state correction unit that corrects the current-carrying state of the fuel cell. 2. The pressure-accumulation fuel injection device according to claim 1, wherein correcting the energization state of the injector to the side that suppresses the heat generation amount of the injector as compared with the normal time,
A pressure-accumulation type fuel injection device, which is a correction for reducing a current value of a drive signal applied to the injector as compared with the normal time. 3. The pressure-accumulation fuel injection device according to claim 2, wherein the energization state correction means has a pressure detection means for detecting a pressure in the pressure accumulation container, and the drive signal is different from that in the normal state. The pressure-accumulation fuel injection device is characterized in that when the current value is reduced, the pressure in the pressure accumulator detected by the pressure detection means is greatly reduced when the pressure is high compared to when the pressure is low. 4. The pressure-accumulation fuel injection device according to claim 2, wherein the injector is a nozzle needle that opens and closes an injection hole, a pressure control chamber that controls the operation of the nozzle needle, and the pressure control chamber. An accumulator type fuel injection device, comprising: an actuator that drives the nozzle needle in the valve opening direction by reducing the pressure of 1. and an urging means that urges the nozzle needle in the valve closing direction. 5. The pressure-accumulation type fuel injection device according to claim 4, wherein the actuator applies a valve body that switches between a communication state and a cutoff state between the pressure control chamber and the fuel return path, and the drive signal. Then, it has a solenoid coil that sucks the valve element to communicate with the pressure control chamber and the fuel return path, and leak fuel leaking from the injector is discharged from each sliding portion and the pressure control chamber in the injector. A pressure-accumulation type fuel injection device configured to be discharged to the outside through the periphery of the solenoid coil and to be returned to the fuel tank via the fuel return path. 6. The pressure-accumulation fuel injection device according to claim 4, wherein the injection amount calculation means calculates a target injection amount according to the operating condition of the internal combustion engine, and the operating condition of the internal combustion engine and An injection timing calculation unit that calculates a fuel injection timing according to the target injection amount set by the injection amount calculation unit, and a pressure detection unit that detects the pressure in the pressure accumulating container, the energization state correction unit, When the correction for lowering the current value of the drive signal is performed, and when the pressure in the pressure accumulator detected by the pressure detection means is a low value equal to or lower than a predetermined value, the fuel injection timing set by the injection timing calculation means is set. A pressure-accumulation type fuel injection device having an injection timing correction means for correcting in an advance direction. 7. The pressure-accumulation fuel injection device according to claim 4, wherein the injection amount calculation means calculates a target injection amount in accordance with the operating condition of the internal combustion engine, and the operating condition of the internal combustion engine. And an injection timing calculation means for calculating the fuel injection timing according to the target injection amount set by the injection amount calculation means, wherein the energization state correction means, when performing the correction to reduce the current value of the drive signal, A pressure-accumulation type fuel injection device having an injection timing correction means for correcting the fuel injection timing set by the injection timing calculation means in an advance direction. 8. The pressure-accumulation fuel injection device according to claim 5, wherein the drive signal is a pulsed drive current applied to the injector from a fuel injection start timing to an end of injection, When applying the pulsed drive current, the solenoid coil is energized at the charge current value which is the highest current value when the injector is opened, and then until a predetermined time elapses, A second drive current lower than the first drive current value after energizing the solenoid coil at a first drive current value lower than the charge current value and closing the injector after the predetermined time has elapsed. A pressure-accumulation type fuel injection device, wherein the solenoid coil is energized according to a value. 9. The pressure-accumulation fuel injection device according to claim 8, wherein when the current value of the pulsed drive current is reduced as compared with the normal time, the first drive current value is lower than the second drive current value. A pressure-accumulation type fuel injection device characterized in that the drive current value is greatly reduced compared to the normal time. 10. A high-pressure fuel pressure-fed by a high-pressure supply pump is accumulated in a pressure accumulator container, and the high-pressure fuel accumulated in the pressure accumulator container is distributed and supplied to an injector mounted in each cylinder of an internal combustion engine. In the pressure-accumulation fuel injection device that supplies high-pressure fuel from the injector to each cylinder of the internal combustion engine when the injector is energized, (a) a current value that stores a predetermined basic current value of a drive signal Storage means, (b) pressure detection means for detecting the pressure in the pressure accumulator, and (c) the current value when the pressure in the pressure accumulator detected by the pressure detection means exceeds a predetermined value. And a current value correction means for correcting the current value of the drive signal applied to the injector so as to be lower than the predetermined basic current value of the drive signal stored by the storage means. Accumulator type fuel injection system.