GB2386643A

GB2386643A - Accumulator-type fuel injection system with pump control valve solenoid temperature protection

Info

Publication number: GB2386643A
Application number: GB0300576A
Authority: GB
Inventors: Takashi Kikutani; Toshimi Matsumura
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2002-01-15
Filing date: 2003-01-10
Publication date: 2003-09-24
Anticipated expiration: 2023-01-10
Also published as: DE10301066B4; GB0300576D0; JP2003206790A; GB2386643B; DE10301066A1; JP3960051B2

Abstract

A common rail type fuel injection system according to the present invention prevents the temperature of the solenoid coil of a suction control valve from rising above a predetermined temperature of the suction control valve (6) before the engine (1) is started, thereby increasing the life of interior components of the suction control valve (6). Even when the starter remains in the IG Ò ON state for a long period of time, the energization of the solenoid coil in the suction control valve (6) of the supply pump (4) is suspended, thereby making it possible to prevent the temperature of the solenoid coil of the suction control valve (6) from rising above a predetermined temperature. This makes it possible to improve the reliability and increase the life of the interior components of the suction control valve (6).

Description

ACCUMULATOR-TYPE FUEL INJECTION SYSTEM

The present invention relates to an accumulator-type fuel injection system equipped with a high-pressure supply pump that 5 pressurizes the fuel introduced into a pressure chamber via a pump control valve. Examples of pump control valves are valves for controlling the amount of fuel fed under pressure or valves for controlling a fuel injection pressure Fuel is then directed to an accumulator container. More particularly, the present invention 10 relates to an improvement in reliability of interior components of an electric pump control valve such as of an electromagnetic type or an electromotive type valve.

Generally, conventional common rail type fuel injection systems for use in fuel injection systems in diesel engines are 15 configured to accumulate high-pressure fuel under pressure in an accumulator container (a common rail). Shared by all engine cylinders, the accumulator container supplies high-pressure injected fuel to each cylinder at predetermined time intervals through a fuel injection valve that communicates with the common 20 rail. The common rail needs to continuously accumulate a common rail pressure that corresponds to a fuel injection pressure. For that purpose, a variable discharge high-pressure supply pump feeds high-pressure fuel. The pressure and the amount of the fuel fed under pressure are controlled, thereby providing feedback control 25 to the fuel pressure in the common rail (or the fuel injection pressure). Such a high-pressure supply pump has a pressure chamber for pressurizing fuel by a reciprocating plunger and a pump control

L valve (a suction control valve) that allows determination of the amount of fuel to be introduced into the pressure chamber in accordance with the degree of opening (the degree of valve opening) of a fuel passage to the pressure chamber.

5 The common rail fuel injection system equipped with the pump control valve as described above is set to a degree of valve opening in order to improve the ease of starting the engine. That is, the degree of valve opening allows the solenoid coil of the suction control valve to be energized at the same time an ignition key is 10 inserted into the key cylinder in the passenger compartment and turned from the OFF position to the IG position, i.e., at the same time an ignition switch (IG ON) is turned ON. Then, upon energizing the starter for starting the engine, the degree of valve opening allows for providing the amount of fuel and the fuel injection 15 pressure that are necessary for immediately starting the engine.

In the aforementioned method for controlling the degree of opening of the suction control valve upon starting the engine, suppose that the starter remains energized in the IG ON state for a long period of time prior to starting. In this case, the 20 temperature of the solenoid coil in the suction control valve may rise above a particular temperature (a suction control valve reliability limit) for assuring the reliability of interior components of the suction control valve. This causes a problem of significantly shortening the life of the interior components of the 25 suction control valve. For example, rubber components such as sealing materiels or plastic components such as insulating coatings of the solenoid coil may experience a shortened life.

It is therefore an object of preferred embodiments of the present invention to provide an accumulator-type fuel injection system which makes it possible to prevent the temperature of the pump control valve from rising above a particular temperature before the engine is started, thereby increasing the life of the interior components of the suction control valve. According to a first aspect of the invention, when the 10 rotational speed of the engine does not increase to or above a predetermined value, for example, a particular cranking speed, the fuel injection control unit prohibits the pump control valve from energizing until a predetermined condition is satisfied. This permits the temperature of the pump control valve to not rise above 15 a specific limit before the engine is started. It is thus possible to improve the reliability of interior components of the pump control valve and increase the life of the interior components of.

the pump control valve.

According to a second aspect of the invention, the 20 aforementioned pump control valve starts to energize when an ignition key is inserted into a key cylinder, when the ignition key is turned from an OFF position to an IG position or an ACC position in the key cylinder, or when a door lock provided in the vehicle is unlocked from outside the vehicle. This allows a driver or person 25 to turn the ignition key to the ST position to start energizing the starter immediately after entering the vehicle, thereby enabling the engine to be quickly started.

L According to a third aspect of the invention, the predetermined condition corresponds to a predetermined time period The predetermined time period is substantially equivalent to a period of time during which the pump controlvalve begins energizing 5 until the temperature of the pump control valve achieves a particular temperature before the engine is started, or a period of time during which a glow plug for facilitating starting of the engine starts to be energized and is then fully energized. This permits distinguishing the condition of energizing the pump control 10 valve from the condition of not energizing the pump control valve.

According to a fourth aspect of the invention, cases where the rotational speed of the engine does not increase to the predetermined value or more include a case where the starter is not energized, a case where the rotational speed of the engine does not 15 increase to a cranking speed or higher, or a case where the engine is not started. This allows for defining the condition for prohibiting the pump control valve from being energized in order to prevent the temperature of the pump control valve from rising above the predetermined temperature.

20 According to a fifth aspect of the invention, the aforementioned pump control valve is a suction control valve for adjusting the amount of fuel introduced into a pressure chamber of the high-pressure supply pump. The suction control valve is an electromagnetic valve of the normally open type which is fully 25 opened in terms of the degree of valve opening when de-energized.

To improve the ease of starting the engine, this allows for setting the valve to such a degree of opening that the suction control valve

is energized at the same time of the insertion of an ignition key, and the amount of fuel and the fuel injection pressure necessary for an immediate start of the engine are provided upon energizing the starter. Accordingly, it is possible for a driver or a person 5 to turn the ignition key to the ST position to start energizing the starter immediately after having entered the vehicle, thereby cranking the engine to quickly start it.

Further areas of applicability of the present invention will

become apparent from the detailed description provided hereinafter

10 It should be understood that the detailed description and specific

examples, while indicating preferred embodiments of the invention, are exemplary and intended for purposes of illustration only and are not intended to limit the scope of the invention.

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

Fig. 1 is a schematic view of the configuration of a fuel injection system of the common rail type according to an embodiment 20 of the present invention; Fig. 2 is a flowchart of a method for controlling the fuel injection system of the common rail type according to an embodiment of the present invention; Fig. 3 is a flowchart of a method for controlling the fuel 25 injection system of the common rail type according to an embodiment of the present invention; and Fig 4 is a timing chart of the operation of the fuel injection

system of the common rail type according to an embodiment of the present invention.

5 The following description of the preferred embodiments is

merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Now, the present invention will be described in accordance with an embodiment with reference to the accompanying drawings, in 10 which Fig. 1 illustrates the entire configuration of a fuel injection system of the common rail type.

A fuel injection system of the common rail type according to this embodiment includes a common rail 2, which serves as an accumulator container. The accumulator container accumulates 15 high-pressure fuel under a pressure corresponding to a fuel injection pressure at which the pressurized fuel is supplied by injection into each cylinder of an internal combustion engine (hereinafter referred to as the engine) 1 such as a diesel engine having a plurality of cylinders. The fuel injection system further 20 includes a plurality of injectors 3 (four injectors in this embodiment) with one injector 3 being arranged on each cylinder of the engine 1, a supply pump 4 for pressurizing the fuel introduced into a pressure chamber via a suction control valve 6 (discussed hereinafter) to feed the fuel under pressure to the common rail 2, 25 and an electronic control unit (corresponding to a fuel injection control device according to the present invention and hereinafter referred to as the ECU) 10 for electronically controlling the

plurality of injectors 3 and the supply pump 4.

It is necessary to continuously accumulate a common rail pressure corresponding to the fuel injection pressure in the common rail 2, which is thus connected to the outlet of the supply pump 5 4 for discharging high-pressure fuel therein via a fuel conduit (a high-pressure fuel passage) 11. The fuel that leaks past the injectors 3 and the supply pump 4 is allowed to return to a fuel tank 5 via leakage fuel conduit (fuel return passages) 12, 13, and 14. A relief conduit (a fuel return passage) 15 that connects the 10 common rail2 and the fuel tank 5 is provided with a pressure limiter 16. The pressure limiter 16 is a pressure relief valve that opens when the fuelpressure in the common rail 2 exceeds a set upper limit pressure in order to limit the fuel pressure to the set upper limit.

The injector 3 on each of the cylinders, which is connected 15 to a downstream end of each of a plurality of manifolds 17 that branch from the common rail 2, is an electromagnetic fuel injection valve which includes a fuel injection nozzle for injecting the high pressure fuel accumulated under pressure in the common rail 2 into each cylinder of the engine 1. The injectors 3 also serve as 20 electromagnetic actuators or valves for providing back pressure control to anozzle needle accommodated in the fuel injection nozzle, The electromagnetic valve is activated or deactivated (turned ON or OFF) to electronically control the injection of fuel from the injector 3 on each of the cylinders into the respective cylinders 25 of the engine 1. That is, while the electromagnetic valve of the injectors 3 is open, the high-pressure fuel accumulated under pressure in the common rail 2 is supplied by injection into the

cylinders of the engine 1.

The supply pump 4 has a known built-in feed pump (a low-pressure feed pump, not shown) that pumps up the fuel in the fuel tank 5 by a pump drive shaft 22 which is caused to rotate by 5 the rotation of a crankshaft 21 of the engine 1. In the configuration according to this embodiment, there is provided a power transmission device 25 such as a belt that is looped over a crank pulley 23 installed on an end portion of the crankshaft 21 and over a pump pulley 24 installed on an end portion of the pump 10 drive shaft 22. Accordingly, the pump drive shaft 22 of the supply pump 4 rotates in sync with the crankshaft 21 of the engine 1.

The supply pump 4 has a pump chamber into which the fuel is introduced that the feed pump pumps up via a fuel conduit 19, a plunger (not shown) that is actuated by the pump drive shaft 22, 15 and a pressure chamber (a plunger chamber) for allowing the reciprocating movement of the plunger to pressurize the fuel. The supply pump 4 acts as a high pressure fuel feed pump for pressurizing the fuel introduced from the pump chamber into the pressure chamber via the suction control valve 6. The high pressure fuel is fed under 20 pressure from the outlet to the common rail 2. The suction control valve (SCV) 6 for controlling the degree of opening of the fuel passage is provided in the fuel passage of the pump chamber of the supply pump 4.

The suction control valve 6, corresponding to the pump 25 control valve according to the present invention, is electronically controlled by a pump drive signal from the ECU 10 via a pump drive circuit (not shown). This allows a pump pressure control valve (an

l electromagnetic valve for adjusting the amount of suction), for adjusting the amount of suction of the fuel introduced from the pump chamber of the supply pump 4 into the pressure chamber, to change the common rail pressure corresponding to the fuel injection 5 pressure (fuel pressure) at which the fuel is supplied by injection from each injector 3 to the engine 1.

The suction control valve according to this embodiment has a valve (valve body) for changing the degree of opening of the fuel passage from the pump chamber of the supply pump 4 to the pressure 10 chamber and a solenoid coil (an electromagnetic coil) for adjusting the degree of valve opening in response to the pump drive signal (a suction control valve command value). The suction control valve 6 is also a normally open electromagnetic valve (a pump control valve) that fully opens in terms of the degree of valve opening when 15 the solenoid coil is de-energized. In this embodiment, to provide improved ease of starting the engine 1, the solenoid coil of the suction control valve 6 starts to be energized at the same time the ignition key is inserted into the key cylinder in the passenger compartment and turned from the OFF position to the IG position, 20 i.e., as the ignition switch is turned on (IG ON). This causes the valve to be set to the degree of opening that allows for providing the amount of fuel and the fuel injection pressure that are necessary for immediately starting the engine 1 upon energizing the starter to start the engine 1.

25 The ECU 10 is provided with a microcomputer that has a CPU for performing control and computation processing, memory units such as ROM and RAM, an input circuit, an output circuit, a power

supply circuit, an injector drive circuit (EDU), and a pump drive circuit. Sensor signals from various sensors are adapted to be converted from analog to digital with an A-D converter for input to the microcomputer.

5 The ECU 10 is provided with injection timing and injection volume determination means for determining the optimum injection timing (the start timing for a main injection, fit) and the target volume of injection (the time period of injection, Q) in accordance with the running conditions of the engine 1. The ECU 10 is further 10 provided with injection pulse width determination means for computing the duration of an injection pulse (an injection pulse width) in accordance with the running conditions of the engine 1 or the fuel injection pressure (i.e., the co on rail pressure) and the target volume of injection (Q), and injector drive means for 15 applying a pulsed injector drive current (an injection pulse) to the electromagnetic valve of the injector 3 on each cylinder via the injector drive circuit (EDU).

That is, the ECU 10 is configured to calculate the target volume of injection (Q) in accordance with the information on the 20 running conditions of the engine such as the rotational engine speed (hereinafter referred to as the number of engine revolutions or NE) sensed by a rotational speed sensor 31 and the degree of accelerator opening (ACCP) sensed by an accelerator opening degree sensor 32.

The ECU 10 then applies an injector drive current (an injection 25 pulse) to the electromagnetic valve of the injector 3 on each cylinder in accordance with the width of the injection pulse that has been calculated according to the running conditions of the

engine 1 or the fuel injection pressure (i.e., the common rail pressure) and the target volume of injection (Q.). This configuration allows the engine 1 to run.

The ECU 10 also serves as a suction control means (or SCV 5 control means) for computing the optimum fuel injection pressure (i.e., the target common rail pressure) corresponding to the running conditions of the engine 1 to drive the suction control valve 6 of the supply pump 4 via the pump drive circuit. That is, the ECU 10 is configured to compute the target common rail pressure 10 (Pet) in consideration of the engine running conditions such as the number of engine revolutions (NE) sensed by the rotational speed sensor 31 and the degree of accelerator opening (ACCP) sensed by the accelerator opening-degree sensor 32 as well as in consideration of the correction made to the temperature of cooling 15 water for the engine (THW) sensed by a cooling water temperature sensor 33 or the fuel temperature (THE) sensed by a fuel temperature sensor 34. To achieve the target common rail pressure, the ECU 10 delivers the pump drive signal (a suction control valve command value) to the solenoid coil of the suction control valve 6.

20 More preferably, a common rail pressure sensor (fuel injection pressure sensor means and fuel pressure sensor means) 35 for sensing the common rail pressure corresponding to the fuel injection pressure is attached to the common rail 2. It is thus desirable to provide feedback control using the pump drive signal 25 (the suction control valve command value) of the suction control valve 6 of the supply pump 4 such that the common rail pressure (Per) sensed by the common rail pressure sensor 35 substantially

corresponds with the target common rail pressure (Pet) determined in accordance with the running conditions of the engine 1 Additionally, it is preferable to provide duty control to the suction control valve command value (a drive current value) for the 5 suction control valve 6. It is possible to provide digital control with high accuracy by using duty control in which the rate of ON/OFF (the rate ofenergization duration or a duty ratio) of the pump drive signal per unit time is adjusted in accordance with the target common rail pressure (or target pump feed under pressure) to change 10 the degree of valve opening of the suction control valve 6.

In this embodiment, the rotational speed sensor 31, the accelerator opening-degree sensor 32, the cooling water temperature sensor 33 or the fuel temperature sensor 34 are used as the running condition sensor means for sensing the running 15 conditions ofthe engine 1 to compute the target volume of injection (Q), the injection timing (0t), and the target common rail pressure (Pct). However, the target volume of injection (Q.), the injection timing (0t), and the target common rail pressure (Pet) may be corrected in consideration of sensor signals (engine running 20 information) from other types of sensors (for example, an intake air temperature sensor, an intake air pressure sensor, a cylinder discrimination sensor, or an injection timing sensor) employed as the running condition sensor means.

25 Now, a method for controlling the fuel injection system of the common rail type according to this embodiment will be explained briefly with reference to Figs. 1 to 3. Among these figures, Figs.

2 and 3 are flowcharts illustrating the method for controlling the fuel injection system of the common rail type.

First, it is determined whether the ignition switch has been turned on (IG ON) (step S1). If it is determined YES, engine 5 parameters (the running conditions of the engine 1) such as the number of engine revolutions (NE), the degree of accelerator opening (ACCP), the temperature of cooling water for the engine (THW), the fuel temperature (THF), and the common rail pressure (Per) are taken.

10 Then, it is determined whether a running flag (fNE) for determining whether the engine has started has been set (step S3) If it is determined YES, the process proceeds directly to step S5.

On the other hand, if it is determined NO in step S3 or if the engine 1 has not yet been started, it is determined whether a starter 15 energization flag (fSTA) for determining if the starter is energized has been turned ON (step S4). If it is determined NO, the process proceeds directly to step S15.

On the other hand, if YES is determined in step S4, i.e., if the starter has been energized, it is then determined whether the 20 number of engine revolutions (NE) is lower than the cranking speed (A) (step S5). If YES is determined, the process proceeds directly to step S15. On the other hand, if NO is determined in step S5, i.e., if the number of engine revolutions (NE) has increased above the cranking speed (A), a counter, for counting the time after IG 25 ON, is cleared (step S6). The running flag (fNE) of the engine 1 is then set (step S7).

It is then determined whether the engine 1 has been started.

More specifically, it is determined whether the number of engine revolutions (NE) has increased above the engine idle speed (B) (step S8). If it is determined NO, i.e., if the engine 1 has not yet been started, it is then determined that the engine 1 is cranking, 5 and the SCV control value (DsCv: suction control valve command value) is then set to a second default (D2) during the energization of the starter (during cranking) (step S9).

Then, the target volume of injection (Q) and the injector injection pulse width (Tq), serving as INJ control values, are 10 computed based on the engine parameters. The injection timing (0t) is also computed in accordance with the engine parameters. More specifically, the target volume of injection (Q) is determined from the aforementioned number of engine revolutions (NE) and the aforementioned degree of accelerator opening (ACCP). Additionally, 15 the injector injection pulse width (Tq) is determined from the aforementioned target volume of injection (Q) and the aforementioned common rail pressure (Par). Furthermore, the injection timing (6t) is determined from the aforementioned number of engine revolutions (NE) and the aforementioned target volume of 20 injection (Q) (step S10).

The INJ control values, the injection timing, and the SCV control value are set to the output stage of the ECU 10. More specifically, the injector (INJ) injection pulse width (Tq) and the injection timing (0t) are set to the output stage of the ECU 10.

25 In addition, the SCV control value (suction control valve command value: IDSCV) is set to the output stage of the ECU 10 (step Sit).

Subsequently, the process proceeds to step S1, from which the

aforementioned control is repeated.

On the other hand, if YES is determined in step S8, i.e., if the engine 1 has already been started, the target common rail pressure (Pet) is computed in accordance with the engine parameters 5 More specifically, the target common rail pressure (Pet) is determined from the aforementioned number of engine revolutions (NE) and the aforementioned target volume of injection (Q) (step S12). Then, an SCV correction value (Di) is computed in accordance with the difference in pressure (Per - Pct) between the 10 aforementioned common rail pressure (Per) and the aforementioned target common rail pressure (Pet) (step S13). Then, the SCV-

correction value (Di) is added to the previous SCV control value (ADS=) to compute the current SCV control value (suction control valve command value: Ds=) (step S14). Thereafter, the process 15 proceeds to step Sl0.

On the other hand, if NO is determined in step S4, or if YES is determined at step S5, the running flag (fNE) of the engine 1 is cancelled (step Sl5). Then, the elapse time after the IG ON is calculated such that CIGon = CIGon + 1 (step S16). It is then 20 determined whether the predetermined time (T0) has elapsed after the ignition switch is turned ON (CIGon > T0)(step S17). Suppose that NO is determined, i.e., the predetermined time (T0) has not elapsed after the ignition switch is turned ON. In this case, before the engine 1 is started, the process determines that the 25 predetermined time (T0) has not elapsed after the suction control valve 6 of the supply pump 4 starts to be energized, and then sets the SCV control value (midst: Suction control valve command value)

to a first default (D1) before the starter starts to be energized (step S18). Thereafter, the injector injection pulse width (Tq) serving as an INJ control value is cleared (step S19). The process then proceeds to step S11.

5 On the other hand, suppose that YES is determined in step S17, i.e., the predetermined time (T0) has elapsed after the ignition switch is turned ON. In this case, before the engine 1 is started, the process determines that the predetermined time (T0) has elapsed after the suction control valve 6 of the supply pump 4 starts to 10 be energized, and then resets the SCV control value (DS=: Suction control valve command value) (step S20). Thereafter, the process proceeds to step S19.

On the other hand, if NO is determined in step S1, the running flag (fNE) of the engine 1 is cancelled (step S21). Then, the 15 counter (CIGon) for counting the time after the IG ON is cleared (step S22). Thereafter, the process proceeds to step S20.

[Feature of Embodiment] Now, the operation of the fuel injection system of the common rail type system according to this embodiment is briefly explained 20 with reference to Figs. lto 4. Fig.4 is a timing chart illustrating the operation of the common rail type fuel injection system.

Suppose that a driver on board a vehicle inserts the ignition key into the key cylinder in the passenger compartment to turn the ignition key from the OFF to the IG positions in the key cylinder.

25 This causes the ignition switch to be turned ON (IG ON) and the ECU 10 to start the routine shown in Figs. 2 to 3. Here, at the same time as the IG ON, the solenoid coil in the suction control valve

6 of the supply pump 4 is energized at the first default (D1), causing the valve to be set to the degree of opening that permits the amount of fuel and the fuel injection pressure necessary for immediately starting the engine 1 upon energizing the starter.

5 When the driver turns the ignition key from the IG position to the ST position in the key cylinder, the starter begins energizing (STA ON) which begins cranking the engine 1. At the same time as the STA ON, the solenoid coil in the suction control valve 6 of the supply pump 4 starts energizing at the second default (D2) 10 that is greater than the first default (D1), thereby providing a degree of opening larger by the difference between the valve defaults. Since the supply pump 4 is driven at the cranking speed, the fuel is fed under pressure into the common rail 2, causing the pressure in the common rail to become greater than the atmospheric 15 pressure. At this time, the fuel is injected from the injectors 3 on each cylinder into the respective cylinders of the engine 1, thereby causing the engine 1 to start and run at a number of engine revolutions greater than or equal to the idling engine speed.

However, suppose that the starter remains for a long period 20 of time in the energizing IG ON state and the value of the drive current applied to the solenoid coil in the suction control valve 6 of the supply pump 4 is maintained at the first default (D1) to hold the predetermined degree of opening of the valve as shown by the alternate long end short dashed line in the timing chart of Fig. 25 4. In this case, the temperature of the solenoid coil in the suction control valve 6 of the supply pump 4 may rise above a predetermined temperature (a suction control valve reliability limit) for assuring the reliability of interior components of the supply pump 4, as

shown by the alternate long and short dashed line in the timing chart of Fig. 4. This causes a disadvantage of significantly shortening the lives of interior components of the suction control 5 valve 6 (for example, rubber components such as sealing materials or plastic components such as insulating coatings of the solenoid coil) In this regard, even when the starter remains for a long period of time in the energizing IG ON state, this embodiment is 10 configured to prohibit (suspend) the energization of the solenoid coil in the suction control valve 6 of the supply pump 4 at a point in time after a predetermined time period has elapsed (in the IG ON state). Thereafter, at the same time the driver turns the ignition key from the IG position to the ST position in the key 15 cylinder or as the STA ON, the solenoid coil in the suction control valve 6 of the supply pump 4 starts to be energized at the second default (D2) that is greater than the first default (D1), thereby compensating degradation in the ease of starting the engine 1.

20 As described above, the fuel injection system of the common rail type according to this embodiment is configured to prohibit (suspend) energization of the solenoid coil in the suction control valve 6 of the supply pump 4 at a point in time after a predetermined time period has elapsed from the IG ON state, even when the starter 25 remains for a long period of time in the IG ON state. In other words, when the solenoid coil in the suction control valve 6 is energized for a predetermined time period or more before the engine 1 is

started, the energization of the solenoid coil in the suction control valve 6 is cut, thereby preventing an increase in the temperature of the solenoid coil of the suction control valve 6 from becoming higher than necessary.

5 This permits the temperature of the solenoid coil in the suction control valve 6 of the supply pump 4 to not rise above a predetermined temperature (a suction control valve reliability limit) as shown by the solid line in the timing chart of Fig. 4.

It is thus possible to improve the reliability of interior 10 components of the suction control valve 6 and increase the life of the interior components of the suction control valve 6 (forexample, rubber components such as sealing materials or plastic components such as insulating coatings of the solenoid coil).

Here, it is to be understood that the time period during which 15 the solenoid coil in the suction control valve 6 is energized before the engine 1 is started includes at least one or more of the outside air temperature, the engine cooling water temperature, the engine lubricant temperature, the temperature of the fuel to be introduced into the pressure chamber of the injectors 3, the temperature of 20 the fuel leaked past the supply pump 4, the battery voltage, the temperature of the solenoid coil in the suction control valve 6, the value of the current for driving the solenoid coilof the suction control valve 6, and the duration for energizing a glow plug. The lower the temperatures of the outside air, the engine cooling water, 25 the engine lubricant, and the fuel, or the lower the battery voltage, or the lower the temperature of the solenoid coil in the suction control valve 6, or the lower the value of the drive current applied

to the solenoid coil of the suction control valve 6, the longer the time period (a predetermined time period) of energizing the solenoid coil of the suction control valve 6 may be made before the engine 1 is started.

In this embodiment, an example has been described which provides a suction control valve (the suction control electromagnetic valve) 6 for changing the amount of fuel to be introduced into the pressure chamber of the supply pump 4. However, 10 a discharge control electromagnetic valve may be provided for altering the amount of fuel supplied from the pressure chamber of the supply pump 4 into the common rail 2. Alternatively, a motor-driven (electromotive) suction control valve may be provided instead of the electromagnetic valve.

15 This embodiment has employed the suction control valve (the suction control electromagnetic valve) 6 of the normally open type in which the electromagnetic valve is fully opened in terms of the degree of valve opening when the valve is de-energized. However, a discharge control electromagnetic valve of the normally open type 20 (which is normally open) may also be employed in which the electromagnetic valve is fully opened in terms of the degree of valve opening when de-energized. Alternatively, an electromagnetic valve of the normally closed type may be employed in which the discharge control electromagnetic valve or the suction 25 control electromagnetic valve is completely closed in terms of the degree of valve opening when the valve is de-energized.

The description of the invention is merely exemplary in

nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention.

Such variations are not to tee regarded as a departure from the spirit and scope of the invention.

Claims

1. An accumulator-type fuel injection system comprising: an accumulator container for accumulating high pressure fuel under a pressure corresponding to a fuel injection pressure, a fuel injection valve for injecting the high pressure fuel accumulated under pressure in said accumulator container to each cylinder of an engine, a high pressure supply pump for pressurizing intake fuel to be fed under pressure into said accumulator container, a pump control valve for adjusting an injection pressure of fuel discharged from said high-pressure supply pump or an amount of fuel fed under pressure, and a fuel injection control unit for controlling a degree of opening of said pump control valve so as to obtain a fuel injection pressure or an amount of fuel fed under pressure in accordance with running conditions of said engine, wherein a rotational speed of said engine does not increase to at least a predetermined value, said fuel injection control unit prohibits said pump control valve from being energized until a predetermined condition is satisfied after said pump control valve starts to be energized.

2. An accumulator-type fuel injection system according to claim 1, wherein said pump control valve starts to be energized when an ignition key is inserted into a key cylinder to start said engine, when said ignition key is turned from an OFF position to an IG

position or an ACC position in said key cylinder, or when a door lock provided in a vehicle is unlocked from outside said vehicle.

3. An accumulator-type fuel injection system according to claim 1 or 2, wherein said predetermined condition is a predetermined time period, and said predetermined time period is substantially equivalent to a period of time during which said pump control valve begins to be energized and then a temperature of said pump control valve achieves a predetermined temperature before said engineis started, or a period of time during which a glow plug for facilitating starting of said engine starts to be energized and is then fully energized.

4. An accumulator-type fuel injection system according to any one of claims 1 to 3, wherein cases where the rotational speed of said engine does not increase to the predetermined value or more include a case where a starter for starting said engine is not energized, a case where the rotational speed of said engine does not increase to a cranking speed or more, or a case where said engine is not started.

5. An accumulator-type fuel injection system according to any one of claims 1 to 4, wherein said pump control valve is a suction control valve for adjusting an amount of fuel introduced into a pressure chamber of

said high-pressure supply pump, and said suction control valve is a normally-open electromagnetic valve which is fully opened in terms of a degree of valve opening when de-energized.

6. A method comprising: accumulating high pressure fuel under a pressure corresponding to a fuel injection pressure in an accumulator container, injecting the high pressure fuel accumulated under pressure in said accumulator container to each cylinder of an engine with a fuel injection valve, pressurizing intake fuel to be fed under pressure into said accumulator container with a high pressure supply pump, adjusting an injection pressure of fuel discharged from said high-pressure supply pump or an amount of fuel fed under pressure with a pump control valve, and controlling a degree of opening of said pump control valve, with a fuel injection control unit, to obtain a fuel injection pressure or an amount of fuel fed under pressure in accordance with running conditions of said engine, wherein a rotational speed of said engine does not increase to at least a predetermined value, said fuel injection control unit prohibits said pump control valve from being energized until a predetermined condition is satisfied after said pump control valve starts to be energized.

7. A method according to claim 6, wherein said pump control valve starts to be energized when an ignition key is inserted into a key cylinder to start said engine, when said ignition key is turned from an OFF position to an IG position or an ACC position in said key cylinder, or when a door lock provided in a vehicle is unlocked from outside said vehicle.

8. A method according to claim 6 or 7, wherein said predetermined condition is a predetermined time period, and said predetermined time period is substantially equivalent to a period of time during which said pump control valve begins to be energized and then a temperature of said pump control valve achieves a predetermined temperature before said engine is started, or a period of time during which a glow plug for facilitating starting of said engine starts to be energized and is then fully energized.

9. A method according to any one of claims 6 to 8, wherein cases where the rotational speed of said engine does not increase to the predetermined value or more include a case where a starter for starting said engine is not energized, a case where the rotational speed of said engine does not increase to a cranking speed or more, or a case where said engine is not started.

10. A method according to any one of claims 6 to 9, wherein said pump control valve is a suction control valve for adjusting an amount of fuel introduced into a pressure chamber of said high-pressure supply pump, and said suction control valve is a normally-open electromagnetic valve which is fully opened in terms of a degree of valve opening when de-energized.

11. An accumulator-type fuel injection system substantially as described herein and with reference to figure 1 of the drawings hereof.

12. A method for controlling a fuel injection system substantially as described herein and with reference to any one or more of the drawings hereof.