ES2243809T3 - FUEL PRESSURE CONTROL DEVICE. - Google Patents

Abstract

Fuel pressure control apparatus for a high pressure fuel injection system that is equipped with an accumulator line (20) to supply accumulated fuel at a high pressure to a fuel injection valve (12), comprising: a fuel pump (30) for pressurizing fuel supplied at a high pressure and supplying the fuel to the accumulator line (20) under pressure; a safety valve (22) for controlling a fuel discharge in the accumulator line (20); detection means (68) for detecting a fuel pressure in the accumulator line (20); a calculation means (60) for determining an objective fuel pressure in the accumulator line (20); a means (60) for controlling the fuel pressure to open the safety valve (22) based on the fuel pressure detected and the calculated target pressure and reduce the fuel pressure in the accumulator line; and a means (60) for controlling the safety valve actuation to control an open valve period of the safety valve (22), in which the means (60) for controlling the safety valve actuation controls the valve (22) safety in such a way that prevents the open valve period of the safety valve (22) from overlapping a period during which the fuel injection valve (12) is open, characterized in that the means (60 ) the control of the safety valve actuation controls the safety valve (22) in such a way that it prevents the open valve period of the safety valve (22) from overlapping a period during which the means (68) Fuel pressure detection detects a fuel pressure.

Description

Pressure control device fuel.

Background of the invention 1. Field of the invention

The present invention relates to an apparatus of fuel pressure control according to claim 1.

2. Description of the related technique

From JP 9 209 870, a accumulator fuel injector in which the pressure of the fuel supplied from a fuel pump builds up on a common rail and ejected by an injector. To lessen the fluctuation of fuel pressure on the common rail and provide stable injection characteristics of fuel, a solenoid valve is provided in a conduit of return of fuel of the common rail in which the pressure of the fuel supplied by the fuel pump accumulates in a fuel tank The solenoid valve is controlled to open / close in correspondence with a control signal sent to the injector The solenoid valve is arranged on the water side above a hole in a fuel return line and It is controlled together with the injector by a control circuit. Is that is, the phase of the injector control pulse is shifted, outputs the control pulse of the solenoid valve towards the solenoid valve and therefore overlap a fluctuation of the pressure by the injector on a pressure side less than one target pressure on the common rail and a pressure fluctuation by the solenoid valve on a pressure side greater than the target pressure; therefore, the pressure fluctuation is reduced of fuel on the common rail.

From US 5,727,525, a fuel injection accumulator system for vehicles cars that includes a storage chamber that stores fuel inside it under a certain pressure, a plurality of fuel injectors that communicate with the accumulator chamber to inject the fuel stored inside the same in the engine cylinders of an engine, and a regulator of pressure to regulate the pressure of the fuel flowing through of a drain line from the accumulator chamber to a fuel tank. When a valve is completely closed throttle during a high-load engine operation, the fuel regulator opens the drain line to reduce quickly the fuel pressure inside the chamber accumulator up to a target pressure level. This allows a actual fuel injection pressure quickly follow a change in the target pressure level according to an operating condition of the engine when the throttle valve is reopened.

In general, in an internal combustion engine equipped with an accumulator line such as a common rail, a pump of fuel supplies a high pressure fuel under pressure to the accumulator line, and fuel injection valves connected to the accumulator line inject fuel into the combustion chambers of the engine.

A fuel pressure is controlled in the accumulator line, specifically, an injection pressure of fuel from the fuel injection valves so that it convert into a pressure corresponding to a state of engine operation In such pressure control of fuel, the amount of fuel supplied under pressure from the fuel pump increases, for example, when the fuel pressure in the accumulator line detected by a pressure sensor or similar is less than a fuel pressure target set according to a motor operating state. To conversely, when the fuel pressure detected is greater than the target fuel pressure, the amount of fuel supplied under pressure from the fuel pump or the fuel pressure supply is suspended. In this way, the fuel pressure in the accumulator line is controlled. Due to the performance of such fuel pressure control, the size of the atomized particles of injected fuel and others adjust to a combustion state of the engine.

However, in the case where the pressure of target fuel suddenly decreases, for example, due to a transition of the operating state of the engine from a operating state with high load up to a state of operation with reduced load in a short length of time, even if forced circulation of fuel is restricted or suspended from the fuel pump, it is necessary that an certain length of time until the fuel pressure in the accumulator line is reduced to fuel pressure objective. In such a case, the fuel injection is carried out, although temporarily, based on an injection pressure of excessive fuel, which results in an increase in noise from combustion as a result of excessive atomization of the fuel injected.

In view of such a problem, according to the technique related as described in the Japanese patent application open for public consultation No. HEI 10-54318, a pressure regulator (a safety valve) coupled to a common rail is composed of an electromagnetic valve that can actuate to open and close. When the fuel pressure on the common rail is greater than a target fuel pressure, fuel is discharged from the common rail by opening the safety valve and therefore the pressure of fuel. Due to the performance of a process of reduction of pressure of this type, the difference between fuel pressure and the target fuel pressure is reduced gently. By consequently, the noise increase of combustion as a result of a fuel injection based on excessive fuel injection pressure.

However, although a process of reducing pressure of this type that employs a safety valve be appropriate to properly reduce a fuel pressure, can negatively affect the fuel injection, the forced circulation of fuel from the fuel pump, the detection of a fuel pressure and others. For example, if carries out a fuel injection during the process of pressure reduction, fuel injection pressure changes drastically during fuel injection, and consequently the amount of fuel injection and the rate of injection They also change. As a result, the control accuracy of the Fuel injection inevitably deteriorates.

Summary of the invention

The present invention has been made by taking Consideration of such circumstances. It is an object of the present invention provide a pressure control apparatus of fuel and a method for a fuel injection system high pressure that is able to properly reduce a pressure of fuel in an accumulator line while preventing the high pressure fuel injection system be affected negatively.

According to the pressure control device of inventive fuel, the characteristics of claim 1 They solve the aforementioned object.

From dependent claims 2 to 9, obtain improved embodiments of the control apparatus of the fuel pressure according to the invention.

According to one aspect of the present invention, provides a fuel pressure control apparatus for a high pressure fuel system that is equipped with a accumulator line to supply accumulated fuel to a high pressure to a fuel injection valve, which comprises a fuel pump to pressurize fuel supplied at a high pressure and pressurized the fuel to the accumulator line, a safety valve for control the discharge of fuel in the accumulator line, a detection means to detect a fuel pressure in the accumulator line, a means of calculation to determine a pressure target of the fuel in the accumulator line, a means of fuel pressure control to open the valve safety based on the fuel pressure detected and the calculated target pressure and reduce a fuel pressure by the accumulator line, and a means of controlling the drive of the safety valve to control an open valve period of The safety valve. This pressure control device fuel is characterized because the control means of the safety valve actuation controls the valve safety in such a way that prevents the open valve period of the safety valve overlapping a period during the which the fuel pressure sensing means detects a fuel pressure

This construction makes it possible to avoid changing the fuel injection amount or injection rate due to a decrease in fuel pressure in the accumulator line in response to the opening of the safety valve and reduce suitably a fuel pressure in the accumulator line without adversely affect the state of the fuel injection.

Although this summary does not describe all characteristics of the invention, it should be understood that any combination of the features set forth in the claims Dependents is within the scope of the present invention.

Brief description of the drawings

Figure 1 schematically shows a structure of a high fuel injection system Pressure.

Figure 2 is a timing chart that shows a pattern of change in rail pressure, a state of operation of a fuel pump and others during the steady state operation.

Figure 3 is a flow chart showing a timing calculation procedure to drive some respective regulating valves of the fuel pump.

Figure 4 is a flow chart showing a procedure of setting a timing to trigger a security valve.

Figure 5 is a timing chart that shows an output pattern of a driving signal for the safety valve, an open-close state of the safety valve and others.

Figure 6 is a flow chart showing a control procedure for operating the valve security.

Figure 7 is a graph showing a characteristic of pressure reduction of rail pressure when the safety valve opens.

Description of the preferred embodiment

In this document, hereafter will describe an embodiment in which the present invention is applied to a control apparatus for controlling a fuel pressure in a common rail planned for a diesel engine.

Figure 1 schematically shows some structures of a four direct injection diesel engine four cylinders according to the present embodiment (to which, in the present document, hereafter simply referred to as "the engine") and of a high pressure fuel injection system of the same.

This high fuel injection system pressure is equipped with 12 injectors provided for correspond to respective cylinders # 1 to # 4 of the engine 10, a common rail 20 to which the injectors 12 are connected, a pump 30 fuel to supply fuel pressure in a fuel tank 14 to common rail 20, and a unit 60 of electronic control (to which, in this document, in successively it is called "the UCE").

The common rail 20 has the function of accumulating fuel supplied from the fuel pump 30 to a default pressure. A fuel injection pressure of the injectors 12 is determined based on a pressure of fuel (a rail pressure) on the common rail 20.

A safety valve 22 is coupled to the rail 20 common. The safety valve 22 is an electromagnetic valve normally closed that is actuated to open through a electrical conduction through the ECU 60. Safety valve 22 is connected to the fuel tank 14 through a conduit 21 of security. If the safety valve 22 is opened, the fuel on the common rail 20 it is discharged into the duct 21 of security and is returned to the fuel tank 14 through the safety duct 21. In this way, the rail pressure decreases based on a quantity of fuel discharged from common rail 20. The amount of rail pressure reduction is adjusts based on an open valve period length of the safety valve 22.

The injectors 12 are electromagnetic valves which are operated to open and close by the UCE 60. The injectors 12 inject the fuel supplied from rail 20 common in combustion chambers (not shown) of cylinders # 1 to # 4 respectively. Each of the injectors 12 is also connected to the fuel tank 14 through the valve 21 of security. The fuel that has leaked inside the injectors 12 are returned to the fuel tank 14 through the safety duct 21.

The ECU 60 performs a control associated with a amount of fuel supplied at pump pressure 30 of fuel and a fuel injection timing and a fuel injection quantity of the injectors 12. The ECU 60 it is composed of a memory 64 to store several programs of control, functional data and others, a CPU 62 to perform several arithmetic processes, a plurality of controllers 63 to give output to a conduction signal that is produced based on a supply capacity of a battery 59 to the injectors 12 and others to activate them, and the like.

In addition, several sensors to detect a state operating engine 10, a fuel pressure in the Common rail 20 and the like are connected to ECU 60. In ECU 60 detection signals from these are introduced sensors

For example, a speed sensor 65 of rotation is arranged in the vicinity of a crankshaft (no shown) of engine 10, and a cylinder discriminator sensor 66 is arranged in the vicinity of a camshaft (not shown). Based on the detection signals introduced from the sensors 65, 66, the ECU 60 calculates a rotation speed of the crankshaft (a NE speed of engine rotation) and an angle of crankshaft rotation (an AC crankshaft), respectively.

In addition, an acceleration sensor 67 is arranged in the vicinity of an accelerator pedal (not shown). The acceleration sensor 67 outputs a detection signal corresponding to an amount of depression (a degree of openness of the accelerator) of the accelerator pedal. The common rail 20 is equipped of a fuel pressure sensor 68, which outputs a detection signal corresponding to a rail pressure (a real fuel PCR pressure). A block of cylinders (no shown) of the motor 10 is provided with a temperature sensor 69 of refrigerant, which outputs a current sensing signal to a temperature of the engine coolant (a temperature of refrigerant). The ECU 60 detects an opening degree of accelerator, a real fuel PCR pressure and a temperature of refrigerant based on detection signals from the respective sensors 67 to 69.

The fuel pump 30 is composed of a motor shaft 40 rotatably driven by engine crankshaft 10, a feed pump 31 that operates based on rotation of the 40 motor shaft, a pair of supply pumps (a first pump 50a supply and a second supply pump 50b) actuated by an annular cam 42 formed in the motor shaft 40, and so on.

The feed pump 31 sucks fuel into the fuel tank 14 from an intake port 34 to through an intake duct 24 and supplies the fuel to the first supply pump 50a and the second pump 50b of supply at a predetermined supply pressure. Of the fuel that has been sucked from hole 34 of admission, an excess of fuel that is not supplied even to the first supply pump 50a or the second pump 50b of supply is returned to the fuel tank 14 through the safety duct 21.

Both the first supply pump 50a and the second supply pump 50b are called cam type pumps internal These pumps pressurize the fuel supplied from the feed pump 31 at an even higher pressure (for example, of 25 to 180 MPa) based on alternative movements of a piston (not shown) and supply the fuel under pressure pressurized to common rail 20 from a discharge hole 38 to through a discharge duct 23.

The fuel pump 30 is provided with a first regulating valve 70a and a second valve 70b of regulation, which are designed to regulate quantities supplied with fuel pressure from pumps 50a, 50b of supply, respectively. The two regulating valves 70a, 70b they are normally closed solenoid valves that are actuated to open through an electric conduction by the ECU 60.

Figure 2 is a timing chart that shows timings for sucking fuel into the respective pumps 50a, 50b supply and supply to fuel pressure from them, a pattern of change of rail pressure during steady state operation, and the rest.

The respective supply pumps 50a, 50b suck fuel alternately with phases of the AC angle of crankshaft (AC: crankshaft angle) that are offset from each other in an AC of 180º. Also, the respective pumps 50a, 50b of supply supply fuel pressure alternately with phases that are out of phase with each other in a 180º AC.

As indicated by (b) and (c) in the Figure 2, the first regulating valve 70a opens during a intake stroke of the first supply pump 50a for start sucking fuel and then it closes at a timing Default (AC angle of crankshaft) to stop sucking fuel. All the fuel that has been sucked in this way is pressurized in a forced circulation race that follows the race of suction and is supplied under pressure from the first pump 50a of supply to the common rail 20.

In this way, the amount of fuel supplied under pressure from the first supply pump 50a can be adjusted by changing an open valve period of the First regulating valve 70a.

As indicated by arrows in (b) and (c) in Figure 2, if the delay is delayed to close the first regulating valve 70a to increase a period of open valve thereof, the amount of fuel intake of the first supply pump 50a increases. When such occurs delay of the timing to close the first valve 70a of regulation, timing to start supplying under pressure fuel from the first supply pump 50a is advanced in an amount equal to the amount of delay. As a result, the period of forced circulation of fuel is extended and the amount of forced circulation of fuel from the first pump 50th supply increases.

On the contrary, if the timing is advanced to close the first regulating valve 70a in order to reduce a open valve period thereof, the admission amount of fuel from the first supply pump 50a decreases. To the occur such timing advance to close the first regulating valve 70a, timing (AC angle of crankshaft) to start supplying fuel pressure from the First supply pump 50a is delayed by an amount equal to The amount of advance. As a result, the circulation period forced fuel is shortened and the amount of circulation forced fuel of the first supply pump 50a decreases

As described above, the timing to start fueling since the first supply pump 50a is determined so only based on timing to close the first valve 70th regulation.

Also, by advancing or delaying the timing to close the second regulating valve 70b, the amount of forced circulation can be increased or reduced of fuel from the second supply pump 50b. Besides, the timing (the crankshaft angle AC) to start supplying at fuel pressure from the second supply pump 50b it can also be determined uniquely based on the timing to close the second regulating valve 70b.

Timings to open and close the respective regulating valves 70a, 70b are defined using a crankshaft angle as unit thereof. The timing of valve opening is set as a crankshaft angle relative to the valve closure timing. For example, when it stops supply fuel pressure from pumps 50a, 50b of respective supply, the valve opening timing is fixed at "AC 0ºC" and control valves 70a, 70b Respectives are kept closed during an admission race. On the other hand, when the amount of forced circulation of fuel is set at its maximum, the closing timing of valve is set to "AC 180º", which corresponds to a quantity of change of crankshaft angle during the intake stroke, and the respective regulating valves 70a, 70b are kept open constantly during the admission race.

In addition, every time the pumps 50a, 50b of respective supply suck fuel, timing of the respective regulating valves 70a, 70b are fixed based at a rail pressure, a target fuel pressure and Similar. Hereinafter, it will be described herein. document a procedure to set the closing timings valve with reference to a flow chart shown in the figure 3.

The ECU 60 carries out a routine of calculating actuation timing of regulating valves shown in figure 3 as an interruption manipulation a intervals of a predetermined crankshaft angle (AC 180º).

In step 110, the ECU 60 detects a pressure of actual fuel based on a detection signal from the 68 fuel pressure sensor. As indicated by (g) in Figure 2, the timing to detect the real fuel PCR pressure, specifically, timing (the angle) for the interruption of this routine is fixed in a timing after finishing supplying fuel pressure from the respective supply pumps 50a, 50b (the Timings in which the crankshaft angle AC reaches, by for example, respective angles AAC0, AAC1, ... AAC5).

Then, in step 120, the ECU 60 calculates a PCROBJ target fuel pressure based on a fuel injection amount and a NE rotation speed the motor.

The PCROBJ pressure of target fuel in relationship with the amount of fuel injection and speed Engine rotation NE is calculated preliminary by experiments, so that an atomized or similar particle size of Injected fuel adjusts to a combustion state of the engine, and is stored in memory 64 of the ECU 60 as functional data for the calculation of the PCROBJ target fuel pressure. In addition, in a routine other than this routine, the amount of Fuel injection is calculated based on a degree of throttle opening, a NE speed of engine rotation and other, and is stored in memory 64.

In step 130, the fuel PCR pressure actual is subtracted from the PCROBJ pressure of target fuel, and the resulting value is set as a difference? (= PCROBJ-PCR). Then, in step 140, you calculates an ANGBASE angle valve closure base based on the fuel injection amount, fuel PCR pressure Actual and NE speed of motor rotation.

The ANGBASE angle valve closure base is determined based on a forced circulation amount of fuel from the fuel pump 30 that is required during the steady state operation of it, specifically, when the rail pressure is substantially equal to the pressure PCROBJ fuel target, and PCROBJ fuel pressure objective remains substantially constant. The relationship between the ANGBASE angle valve closure base and injection quantity of fuel and others is stored in memory 64 as data functional for the calculation of the angle ANGBASE closing base of valve.

Then, in step 150, the UCE 60 calculates a final valve closure timing (one angle ANGFIN valve closing end) of valves 70a, 70b of respective regulation based on a formula (1) shown at continuation.

....... (1) ANGFIN = ANGBASE + K_ {p} \ \ times ΔPCR

In this formula, "K_ {p} \ times ΔPCR "represents a correction term by feedback and K_ {p} represents a proportional gain. Such as is evident from the formula (1), if the PCROBJ pressure of target fuel is greater than the actual fuel PCR pressure (ΔPCR> 0), the final ANGFIN angle of valve closure is fixed at a relatively large value. On the contrary, if the PCROBJ pressure of target fuel is less than the PCR pressure of actual fuel (ΔPCR <0), the final ANGFIN angle of Valve closure is set at a relatively small value.

After calculating the final ANGFIN angle of valve closure, in steps 160 to 190 the angle is compared ANGFIN valve closing end with a "AC 180º" value set of upper limit and with a fixed "AC 0ºC" limit value lower, and if necessary, the final ANGFIN angle of Valve closure is corrected. That is, if the final ANGFIN angle of valve closure is greater than "AC 180 ° C" (if the result in step 160 is YES), is set equal to "AC 180º" (step 170). Yes The final ANGFIN angle of valve closure is smaller than "AC 0 ° C "(if the result of step 180 is YES), it is set equal to "AC 0 ° C" (step 190). After this, the UCE 60 ends temporarily to the processes of this routine.

Then in a different routine from the present routine, the ECU 60 adjusts an amount of circulation forced fuel pump 30 fuel output alternatively to a driving signal based on the angle ANGFIN valve closing end towards valves 70a, 70b of respective regulation through controllers 63 and controls thus a rail pressure.

As described above, ECU 60 adjusts a quantity of forced circulation of fuel from the fuel pump 30 to control a rail pressure of so that the rail pressure matches the PCROBJ pressure of target fuel On the other hand, for example, in the case in that the PCROBJ target fuel pressure decrease suddenly and the rail pressure cannot follow the pressure decrease PCROBJ of target fuel, ECU 60 opens valve 22 of security for a predetermined length of time to thus carry out a process of reducing the rail pressure (in the present document, hereinafter referred to as the "process of pressure reduction ").

Hereinafter, it will be described herein. document a pressure reduction process with reference to Figures 4 to 7.

Figure 4 is a flow chart showing the content of a process of a "routine of fixing the safety valve actuation timings ". The Figure 5 is a timing chart showing a signal of conduit which has been output to valve 22 of security from controllers 63 of the UCE 60, a state of opening-closing safety valve 22 based in the driving signal, and so on. Figure 6 is a diagram of flow that shows the content of a process of a "routine of control of the safety valve drive ".

As indicated by (a) in the figure 5, the driving signal that has been output to the safety valve 22 is defined based on two parameters, specifically, a TCERRED time of no driving and a time Driving TABIER

Defining an AC angle of crankshaft after a predetermined angle α of a detection angle of the real fuel PCR pressure (for example, AAC1, AAC2 or AAC3 shown in figure 5) as a reference angle (BAC1, BAC2), TCERRADA non-driving time represents a time since achievement of the reference angle by the crankshaft angle AC until the beginning of the electricity supply to valve 22 of security. The TABIERTA driving time represents a time from the beginning of the electricity supply to the valve 22 of security until the interruption of the electricity supply.

The safety valve 22 opens and closes based on a driving signal. However, the timings when the safety valve 22 is opened and closed do not completely match the timings to start and stop supplying electricity to safety valve 22, respectively. That is, the safety valve 22 opens after elapsing a response delay time ΔT1 default from timing to start driving electric, and closes after a time ΔT2 of default response delay from timing to stop electric conduction (see (b) in figure 5).

Considering such a delay in response from the safety valve 22, the non-conduction time CLOSED is fixed so that the crankshaft angle AC at which the valve 22 of safety opens really match a crankshaft angle after a predetermined angle? from the reference angle (BAC1, BAC2) (shown in Figure 5 as CAC1, CAC2 and called hereinafter "actual opening angle of valve").

The actual valve opening angle (CAC1, CAC2) is set preliminary to be constantly delayed with regarding a timing to end the injection of fuel in the case where the timing for injection of fuel by the injectors 12 has changed depending on a Engine operating status. Therefore, whenever open safety valve 22, fuel injection already It will be over.

The TABIERTA driving time is intended for set an open valve period of the safety valve 22. The TABIERTA driving time is set based on a difference between the actual fuel PCR pressure and the PCROBJ pressure of target fuel and so on as follows. That is, if the safety valve 22 opens during the time TABIERTA de conduction, the actual fuel PCR pressure is reduced to PCROBJ pressure of target fuel.

Hereinafter, it will be described herein. document a detailed time setting procedure TCERRADA of non-driving and of the time TABIERTA of driving with reference to figures 4, 5 and 7.

After ending the "routine of calculating the actuation timing of regulating valves ", ECU 60 carries out the "routine of fixing the safety valve actuation timings " shown in figure 4 as a manipulation of the interruption a intervals of a predetermined crankshaft angle (AC of 180º).

First, in stage 210, the UCE 60 determines whether the actual fuel PCR pressure is higher or not than a value (PCROBJ + \ DeltaP1) obtained by adding a value \ DeltaP1 default to the PCROBJ target fuel pressure, specifically, if it is necessary or not to carry out the reduction process of pressure.

If the pressure reduction process is performed when the difference (PCR - PCROBJ) between the PCR pressure of real fuel and PCROBJ pressure of target fuel is not large enough, the rail pressure can drop very below the PCROBJ target fuel pressure in response to the opening of the safety valve 22. In other words, it arises the concern that the so-called phenomenon of overreaction

Therefore, if the difference between the PCR pressure of actual fuel and PCROBJ pressure of target fuel is small enough to ignore an increase in combustion noise, it is preferable to adopt the following countermeasure in terms of inhibition of the generation of the phenomenon of overreaction That is, while limiting an amount of forced fuel circulation of the fuel pump 30 based on a feedback control, the rail pressure is gradually reduced by a fuel injection or the called invalid injection in which the injectors are operated 12 in an invalid injection period to discharge fuel on the common rail 20 towards the safety duct 21 through the inside of the injectors 12.

From this point of view, the value ΔP1 default is set to a value large enough to to avoid an increase in combustion noise, specifically, in a adequate value to inhibit the generation of the phenomenon of overreaction

If in step 210 it is determined that the process of Pressure reduction is unnecessary (PCR? PCROBJ + ΔP1), the TABIERTA driving time is set to "0" in step 245. Next, the processes of the present routine.

On the other hand, if in step 210 it is determined that the pressure reduction process is necessary (PCR> PCROBJ + ΔP1), the ECU 60 calculates a CLOSED time in step 220 non-conduction based on the delay time ΔT1 of response of the safety valve 22 and the rotation NE of the engine.

For example, the higher the speed becomes Engine rotation NE, the shorter the required time becomes so that the crankshaft angle AC reaches the actual valve angle open (CAC1, CAC2) of the safety valve 22 from the angle reference (BAC1, BAC2). Therefore, the time CLOSED of no Driving is fixed in a relatively short length of time. He ΔT1 response delay time is calculated preliminary by experiments or the like as a characteristic response of the safety valve 22 and is stored in memory 64 as data to calculate the CLOSED time of no driving.

The respective supply pumps 50a, 50b begin to suck fuel immediately after the crankshaft angle AC has become the same as the angle of detection (AAC1 to AAC3) of the real fuel PCR pressure (see Figure 2). However, under the condition that it is determined affirmatively in Figure 210 (PCR> PCROBJ + ΔP1), always puts an end to the fuel intake before the crankshaft angle AC reaches the reference angle (BAC1, BAC2). In other words, the default ΔP1 value and the angle of Reference (BAC1, BAC2) are set to satisfy such a relationship.

Therefore, although in step 220 the Time CLOSED of non-conduction at its minimum and the timing to start the electricity supply to the safety valve 22 at its earliest timing, the valve 22 security never begins to stock up on electricity during The electrical conduction of the control valves 70a, 70b respective.

In the event that PCR ≤ PCROBJ + ΔP1, The final ANGFIN angle of valve closure is set to a value higher compared to the aforementioned case of PCR > PCROBJ + \ DeltaP1. Therefore, even after the crankshaft angle AC has reached the reference angle (BAC1, BAC2), the respective supply pumps 50a, 50b follow sucking fuel However, since in such a case it is not carried out the pressure reduction process, there is no possibility that the safety valve 22 can begin to stock up on electricity during electric conduction of valves 70a, Respective regulation 70b.

Then, in step 230, the ECU 60 calculates a K (> 0) rate of pressure reduction. If you open the safety valve 22, the fuel is discharged on rail 20 common and thus decreases the rail pressure. The rate at which the rail pressure is not constant but changes depending on a magnitude of rail pressure. That is, as shown in the Figure 7, the rate at which the rail pressure decreases (the gradient of a line of alternating short and long stripes shown in the Figure 7) tends to become smaller in proportion to a decrease in rail pressure The K rate of pressure reduction, which corresponds to the rate at which the rail pressure decreases, it is calculated based on the actual fuel PCR pressure. The relationship between K rate of pressure reduction and PCR fuel pressure real is preliminary by experiments or the like, and it is stored in memory 64 as data to calculate the K rhythm of pressure reduction

In step 240, the ECU 60 calculates a time DRIVING BOARD based on formula (2) shown at continuation.

....... (2) TABIERTA = K \ times (PCR - PCROBJ)

As is evident from the formula (2) previously mentioned and the reduction characteristic of the rail pressure shown in figure 7, if the rail pressure (the real fuel PCR pressure) at the opening of the safety valve 22 is constant, the TABIERTA time of driving is fixed longer in proportion to an increase in difference (PCR - PCROBJ) between the actual fuel PCR pressure and PCROBJ pressure of target fuel. Also, if the pressure differential (PCR - PCROBJ) is constant, the TABLE time of driving is fixed longer in proportion to a decrease in rail pressure (real fuel PCR pressure) at the instant of valve opening

The respective supply pumps 50a, 50b continue to supply fuel pressure immediately before that the crankshaft angle AC becomes the same as the angle of detection (AAC1, AAC2, AAC3) of real fuel PCR pressure (see figure 2). The timing to start supplying to fuel pressure is delayed in proportion to an increase in difference (PCR - PCROBJ) between the actual fuel PCR pressure and PCROBJ pressure of target fuel. Therefore when TABIERTA driving time is set relatively long, the period to supply fuel pressure from the 50th pumps, Respective supply 50b is set relatively short. By therefore, the period to supply fuel pressure from respective 50a, 50b supply pumps do not overlap the period open valve of safety valve 22. In other words, the respective supply pumps 50a, 50b supply under pressure fuel while not discharging fuel while maintaining open safety valve 22.

After having calculated the TABIERTA time of conduction, the ECU calculates a TABIERTAMAX value in step 250 maximum time TABIERTA based on time ΔT2 response delay (see Figure 5) and the NE speed of motor rotation.

The maximum TABIERTAMAX value is the maximum value of the TABIERTA driving time under the condition that the safety valve 22 opens before the angle AC of crankshaft reaches the detection angle (AAC1, AAC2, AAC3) of the Real fuel PCR pressure. The maximum TABIERTAMAX value changes depending on the NE speed of motor rotation. That is, the TABIERTAMAX maximum value is set smaller in proportion to a Increase in NE speed of motor rotation.

In step 260, the driving time TABIERTA it is compared with the maximum TABIERTAMAX value mentioned above. If it is determined that the TABIERTA driving time is greater than the TABIERTAMAX maximum value, the TABIERTA driving time is fixed in step 270 the same as the maximum TABIERTAMAX value.

After the process is carried out in step 270, or if it is determined that the TABIERTA driving time is equal or less than the maximum TABIERTAMAX value, the ECU 60 ends temporarily to the processes of this routine.

As described so far, it prevents the TABIERTA driving time exceeds the TABIERTAMAX value maximum after the end of the routine. Therefore, whenever detect the actual fuel PCR pressure, valve 22 of Security closes. That is, the timing to detect the Real fuel PCR pressure does not take place while it is open the safety valve 22.

The injectors 12 always start the injection of fuel after detecting the PCR fuel pressure real. Therefore, whenever the fuel injection is started, safety valve 22 closes. As described more Above, consideration of the fact that the actual valve angle Open (CAC1, CAC2) of the safety valve 22 is fixed constantly in a delayed timing with respect to the timing to end fuel injection allows reach a conclusion that the period for the injection of fuel, specifically, the open valve period of the nozzles 12 also does not overlap the open valve period of the safety valve 22.

In addition, the 50a, 50b supply pumps respective always start to suck fuel immediately after detecting the actual fuel PCR pressure, and the safety valve 22 is no longer supplied with electricity when real fuel PCR pressure is detected. Therefore, the respective regulating valves 70a, 70b begin to stock up of electricity after interrupting the supply of electricity to the safety valve 22. As described above, the consideration of the fact that the safety valve 22 does not start to supply electricity during the electrical conduction of respective regulating valves 70a, 70b allows to reach a conclusion that the period of electrical conduction of the valves 70a, 70b of regulation does not overlap the driving period electrical safety valve 22.

Next, the processes in the "control routine of valve actuation security "with reference to the flowchart shown in the figure 6.

The ECU 60 carries out this routine as a interruption manipulation at intervals of a crankshaft angle default (180º AC). The timing (the angle) for the interruption is set at the aforementioned angle of reference (BAC1, BAC2).

First, the ECU 60 determines at the stage 310 if the engine is running or not. Here it is determined that the engine is not running if the fuel injection is has stopped "OFF" a motor 10 ignition key or if the engine rotation speed NE has become equal or less than a predetermined rotation speed.

If it is determined here that the engine is in operation, the ECU 60 produces in the step 320 a signal of driving based on the TCERRADA non-driving time and the TABIERTA driving time, and outputs the driving signal towards the safety valve 22 through the controllers 63.

On the other hand, if in step 310 it is determined that the engine is not running, the safety valve 22 electricity is supplied at stage 325 to keep open for a predetermined length of time. The valve period open, which does not depend on the magnitude of the rail pressure in the Engine stop time, calculated by experiments or similar as a time that allows the rail pressure to drop constantly below the target fuel pressure in the time of engine start, and is stored in memory 64. The open valve period can be set as a constant or as a function of the coolant temperature in the instant Engine stop.

Having carried out the processes in stages 320, 325, ECU 60 temporarily terminates to the processes of this routine.

As described above, the process of Pressure reduction of the rail pressure is performed in the case where that the actual fuel PCR pressure is greater than the pressure PCROBJ of target fuel and the difference between the two is greater than the default ΔP1 value.

As a pressure reduction process, it is also knows a method in which the rail pressure is reduced by an invalid injection by the injectors 12. However, a method thus requires unloading fuel in a length of time extremely short, which is called an injection period not valid. Therefore, there is a limit to the amount of fuel which can be downloaded from common rail 20 in an instant, and can it is impossible to achieve a required amount of reduction of Pressure.

In this regard, according to the process of reducing pressure of the present invention, the common rail 20 is provided with the safety valve 22, and the rail pressure is reduced based at the opening of the safety valve 22. Therefore you can Discharge a large amount of fuel from common rail 20. By consequently, the rail pressure can be reduced without problems and safely up to a level close to the fuel pressure objective, and it is possible to adequately inhibit an increase in noise of combustion and others.

In particular, according to the present embodiment, when the safety valve 22 is actuated to open by such pressure reduction process, the open valve period of the safety valve 22 is fixed so that it does not overlap open valve period of the injectors 12. Therefore, it is possible to prevent the amount of fuel injection or the injection rate change due to a decrease in the pressure of the rail based on the opening of the safety valve 22. By Therefore, the rail pressure can be reduced without negatively affecting to fuel injection.

In addition, since the open valve period of the safety valve 22 is fixed so that it does not overlap detection period of the actual fuel PCR pressure, although the common rail 20 has undergone a pressure pulse in the instant of fuel discharge resulting from the opening of the safety valve 22, pressure pulsation does not affect negatively to the detection of the real fuel PCR pressure. Therefore, the actual fuel pressure can be detected With great precision. They can also be calculated with precision raised several control amounts based on the PCR pressure of actual fuel, such as the fuel injection period and else.

As described above, when set the open valve period of the safety valve 22 so that it does not overlap the open valve period of the injectors 12 or at the PCR pressure detection timing of real fuel, the open valve period of the valve 22 of Security can also be set at a constant length of time, short enough, preliminary considering some changes in the open valve period of the injectors 12 and the rest. It is true that such a construction allows fixed preliminary open valve period of valve 22 of safety so that it does not overlap the open valve period of the injectors 12 and so on. However, although the valve period open the safety valve 22 can be set longer to adjust to a difference between the rail pressure and the pressure of target fuel, safety valve 22 remains open only for the constant length of time.

Unlike such a construction, according to the pressure reduction process of the present invention, The maximum TABIERTAMAX value is calculated as a criterion value to determine if the open valve period of the valve 22 of safety overlaps or not the open valve period of the injectors 12 or at the PCR pressure detection timing of real fuel, and the maximum TABIERTAMAX value is compared with the TABIERTA driving time. Only when the TABIERTA time of driving exceeds the maximum TABIERTAMAX value time is limited TABIERTA driving at the maximum TABIERTAMAX value.

Therefore, the open valve period of the safety valve 22 can be extended to its maximum always and when it does not overlap the open valve period of the injectors 12 or at the PCR pressure detection timing of real fuel In addition, the rail pressure can be reduced by one adequate amount corresponding to a difference between the pressure Real fuel PCR and PCROBJ fuel pressure objective.

In addition, according to the pressure reduction process of the present embodiment, the open valve period of the safety valve 22 is fixed so that it does not overlap the period of forced circulation of fuel from pumps 50a, 50b respective supply. That is, it is supplied under pressure and is Discharge fuel at different timings.

For example, it is assumed in this document that the amount of decrease in rail pressure required in the pressure reduction process is "\ DeltaPa" and that the amount of pressure increase required to supply fuel pressure from the pumps 50a, 50b supply respective is "\ DeltaPb". In this case, unless supply pressure and discharge fuel simultaneously, the final amount of change in rail pressure must be equal to (ΔPb - ΔPa). However, if supplied under pressure and fuel is discharged simultaneously, these phenomena interfere each. As a result, there is no guarantee that the amount of change in rail pressure becomes equal to (ΔPb - ΔPa), which negatively affects both circulation forced fuel as to the discharge of fuel.

In this regard, according to the present embodiment, it is possible to avoid mutual interference between circulation forced fuel from pumps 50a, 50b supply respective and the discharge of fuel based on the opening of the safety valve 22. Therefore, the rail pressure can be reduced safely without negatively affecting circulation forced fuel from pumps 50a, 50b supply respective.

In addition, the actual open valve period of the safety valve 22 is calculated based on a signal from driving supplied to it and in a characteristic of response of it. Therefore, the open valve period of the safety valve 22 can be calculated more accurately. By Therefore, it is possible to avoid an inconvenience that may occur when the open valve period of the safety valve 22 overlaps the open valve period of the injectors 12, the PCR timing of real fuel PCR pressure or the period of forced circulation of fuel from pumps 50a, Respective supply 50b. In addition, the open valve period of the safety valve 22 can be extended within a allowable range

In addition, the conduction period of the valve 22 security is set so that it does not overlap the period of conduction of the respective control valves 70a, 70b. By Therefore, it is possible to avoid circumstances in which the overlapping these driving periods makes it impossible for the battery 59 supply a sufficient amount of electrical power to the respective valves 22, 70a and 70b and therefore hinder the Reliable drive thereof. Therefore it is possible prevent the forced circulation of fuel from the 50th pumps, Respective supply 50b, especially that the adjustment of a amount of forced circulation of fuel from them is seen negatively affected, and actuate safety valve 22 with reliability

In addition, according to the present embodiment, the process Pressure reduction is performed on the condition that the difference (PCR - PCROBJ) between the actual fuel PCR pressure and PCROBJ target fuel pressure is greater than the value Default ΔP1. The default ΔP1 value is fixed at a sufficiently large value as long as it does not cause an increase in combustion noise. Therefore, the process of pressure reduction is performed even in the case where the increased combustion noise is negligible, so it is done possible to avoid circumstances in which the rail pressure drops below the target fuel pressure. As a result, it is possible to inhibit the deterioration of the combustion state of the engine that results from an excessive decrease in rail pressure.

In addition, according to the present embodiment, the time DRIVING BOARD, specifically, the open valve period of the safety valve 22, is calculated based on the difference (PCR - PCROBJ) between the actual fuel PCR pressure and the pressure PCROBJ of target fuel and at the K rate of reduction of Pressure. Therefore, unless the TABIERTA driving time is limited by the maximum TABIERTAMAX value, the rail pressure can reduce precisely to PCROBJ fuel pressure objective.

In addition, according to the pressure reduction process mentioned above, if it is determined that the engine is not in operation, the safety valve 22 opens during a default length of time to safely reduce the rail pressure to a pressure lower than the pressure of target fuel Therefore, it is not only possible to inhibit adequately an increase in combustion noise during normal operation but also at the time of restart of the engine.

Especially, the open valve period mentioned above can be changed based on a coolant temperature at the time of engine stop, by which makes it possible to bring the rail pressure closer instantly engine restart at the target fuel pressure, and ensure improved engine starting capacity while adequately inhibits an increase in combustion noise.

The embodiment described so far may undergo the following construction modifications.

In the aforementioned embodiment, the pressure reduction process is performed on the condition that the difference (PCR - PCROBJ) between the fuel PCR pressure actual and the PCROBJ target fuel pressure exceeds the value Default ΔP1, according to which, the period of open valve of safety valve 22 overlaps the period of forced circulation of pump fuel 30 from fuel. By setting those periods so that they do not overlap with each other, the following can also be taken as an example building.

First, the timing (the angle AC of crankshaft) to start supplying fuel pressure from the fuel pump 30 is calculated based on the ANGFIN angle end of valve closure. Then in the process of step 250 shown in figure 4, the maximum TABIERTAMAX value of the TABIERTA driving time is calculated based on time ΔT2 response delay of safety valve 22 and in the NE speed of motor rotation. However, in this case, The maximum TABIERTAMAX value is calculated under the condition that the safety valve 22 is closed before the achievement of the timing for the beginning of the forced circulation of fuel by the crankshaft angle AC.

Then, in the processes after the stage 260, if the TABIERTA driving time exceeds the TABIERTAMAX value maximum, the TABIERTA driving time is set equal to the value TABIERTAMAX maximum. In this way, the TABIERTA driving time is limited to a value equal to or less than the maximum TABIERTAMAX value, so the fuel pump 30 always starts to supply at fuel pressure after closing the safety valve 22.

In this construction, the valve period open the safety valve 22 can be extended until its maximum as long as it does not overlap the circulation period forced fuel from the fuel pump 30, and the rail pressure can be reduced by an adequate amount corresponding to the phase difference between the PCR pressure of Real fuel and PCROBJ pressure of target fuel.

In the aforementioned embodiment, the TABIERTA driving time is set based on the difference (PCR - PCROBJ) between the actual fuel PCR pressure and the PCROBJ pressure of target fuel and at the K rate of reduction of pressure. However, for example, the TABIERTA time of driving can be constant and can be limited to a value that is equal to or less than the maximum TABIERTAMAX value.

In the aforementioned embodiment, the TABIERTA driving time is limited to a value that is equal or less than the maximum TABIERTAMAX value, according to which, it is avoided that The open valve period of the safety valve 22 is superimpose the PCR pressure detection timing of actual fuel or the open valve period of the injectors 12. However, the process to limit time may be omitted Driving TABIER For example, the TABIERTA time of driving can be set at a constant enough value small, whereby the open valve period of the valve 22 security can be set preliminary so that it does not overlap at fuel PCR pressure detection timing actual or at the open valve period of the injectors 12.

When performing the pressure reduction process in the aforementioned embodiment, it is possible to stop completely supplying fuel pressure from pump 30 made out of fuel. In this construction, controllers 63 can Commonly used for regulating valves 70a, 70b respective. As a result, the structure can be simplified general.

In addition to the pressure reduction process based at the opening of the safety valve 22 in the embodiment previously mentioned, the process of pressure reduction for injection-based rail pressure not valid by the injectors 12. In this case, these processes can Perform as follows. That is, if the difference (PCR - PCROBJ) between the actual fuel PCR pressure and the PCROBJ pressure of target fuel is greater than a predetermined pressure, it select the pressure reduction process based on the opening of the safety valve 22. On the other hand, if the difference (PCR - PCROBJ) is less than the default pressure, the Injection pressure reduction process not valid for the injectors 12.

In the aforementioned embodiment, the K rate of pressure reduction is set as a function of the Real fuel PCR pressure. However, it is also possible set the K rate of pressure reduction as a constant.

In the aforementioned embodiment, In addition to the safety valve 22, the common rail 22 can be provided of a mechanical pressure regulator that opens when the pressure the rail rises above a non-disruptive system pressure of forced fuel circulation.

In the aforementioned embodiment, the safety valve 22 is coupled to common rail 20. But nevertheless, the safety valve 22 may be coupled to a conduit of fuel that accumulates fuel at the same pressure as in the common rail 20, for example, to discharge duct 23.

In the aforementioned embodiment, the pressure reduction process is performed on the condition that the difference between the actual fuel PCR pressure and the pressure PCROBJ of target fuel exceeds the value ΔP1 predetermined. However, the pressure reduction process can be performed, for example, on the condition that the pressure Real fuel PCR exceeds PCROBJ fuel pressure objective.

In the aforementioned embodiment, the safety valve 22 can be designed as a valve whose degree Opening is adjustable. By varying the degree of opening depending on the difference (PCR - PCROBJ) between the pressure Real fuel PCR and PCROBJ target fuel pressure, The pressure reduction rate can be adjusted.

In the aforementioned embodiment, shows an example of a diesel engine as a combustion engine internal to which the pressure control apparatus of fuel of the present invention. However, this invention can also be applied, for example, to a motor of direct injection gasoline in which fuel is injected directly in the combustion chambers.

Claims (9)

1. Pressure control device fuel for a high fuel injection system pressure that is equipped with an accumulator line (20) for supply accumulated fuel at a high pressure at a fuel injection valve (12), comprising: a fuel pump (30) to pressurize fuel supplied at a high pressure and supply to press the fuel to the accumulator line (20); a safety valve (22) to control a fuel discharge in the accumulator line (20); detection means (68) for detecting a fuel pressure in the accumulator line (20); a means (60) of calculation to determine a target fuel pressure in the accumulator line (20); a pressure control means (60) of fuel to open the safety valve (22) based on the fuel pressure detected and at the calculated target pressure and reduce the fuel pressure in the accumulator line; Y a means (60) for controlling the actuation of the safety valve to control an open valve period of the safety valve (22), in which the control means (60) of the safety valve actuation controls the valve (22) of safety in such a way that prevents the open valve period of the safety valve (22) overlaps a period during which the fuel injection valve (12) is open, characterized because the drive control means (60) of the safety valve controls the safety valve (22) of such way that prevents the open valve period of the valve (22) security overlaps a period during which the fuel pressure detection means (68) detects a fuel pressure 2. The fuel pressure control apparatus according to claim 1, characterized in that the control means (60) of the safety valve actuation prevents the open valve period of the safety valve (22) from overlapping the timing of detection of the fuel pressure by means of detection (68) by setting the open valve period of the safety valve (22) short. 3. The fuel pressure control apparatus according to claim 1, characterized in that the control valve actuation means (60) sets the open valve period of the safety valve (22) based on a difference between the PCR fuel pressure detected and the PCRTRG pressure of the target fuel calculated. 4. The fuel pressure control apparatus according to claim 3, characterized in that the control valve actuation means (60) opens the safety valve (22) when the fuel PCR pressure detected is by a pressure Default API greater than the calculated target PCRTRG pressure. 5. The fuel pressure control apparatus according to claim 1, characterized in that the control means (60) of the safety valve actuation produces a valve opening signal of the safety valve (22) such that A valve opening timing of the safety valve (22) is constantly delayed with respect to the completion of the fuel injection of the fuel injection valve (12). 6. The fuel pressure control apparatus according to claim 1, characterized in that the electronic control unit (60) calculates a maximum TABIERTAMAX open valve period of the safety valve (22) based on a delay time ΔT2 of response and at an NE speed of motor rotation. 7. The fuel pressure control apparatus according to claim 6, characterized in that the maximum open valve TABIERTAMAX period is shorter the higher the engine rotation NE speed. 8. The fuel pressure control apparatus according to claim 3, characterized in that the control valve actuation means (60) sets the open valve period of the safety valve (22) based on a decreasing speed of the safety valve (22) and at a differential PCR-PCRTRG pressure between the detected fuel PCR pressure and the calculated target fuel PCRTRG pressure. 9. The fuel pressure control apparatus according to claim 1, characterized in that the control valve actuation means (60) produces a valve opening signal and a valve valve closing signal (22 ) safety based on a delay time ΔT2 of the safety valve (22).