JP2001003801A - Common rail-type fuel injector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common rail-type fuel injector capable of preventing the dispersion of the fuel injection amount from injectors to inject the fuel with a target fuel injection amount by controlling the fuel feeding amount fed from a fuel supply pump to a common rail. SOLUTION: A basic pumping amount for feeding from a fuel supply pump to a common rail is determined on the basis of the common rail basic target pressure Prtb, and the common rail pressure Prad (i) lowered by the present fuel injection. The basic pumping amount is corrected for the next fuel injection on the basis of the deviation of the fuel injection amount between the actual fuel injection amount and the target fuel injection amount. The necessary fuel injection amount can be ensured without changing a fuel injection period, that is, without changing a fuel injection rate even when the individual dispersion and the dispersion by deterioration with age are found on the fuel injection amount of each injector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common rail type fuel injection device which stores fuel supplied from a fuel supply pump under pressure in a common rail and injects fuel supplied from the common rail from an injector into a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, for example, regarding a fuel injection control of an engine, a method of increasing an injection pressure and optimally controlling injection conditions such as a fuel injection timing and an injection amount in accordance with an operation state of the engine is known. A common rail fuel injection system is known. The common rail type fuel injection system stores a working fluid for fuel injection control pressurized to a predetermined pressure by a pump in a common rail in a pressure accumulated state, and operates injectors respectively arranged in each cylinder using the working fluid pressure. This is a system in which fuel is injected from an injector into a corresponding combustion chamber. A controller controls an on-off valve as a control valve provided in each injector so that fuel is injected from each injector under optimal injection conditions for the operating state of the engine.

[0003] In the case of a fuel pressure operated common rail type fuel injection system using a working fluid as fuel, a fuel flow path from the common rail to an injection hole formed at the tip of each injector through a fuel supply pipe is always injected. Each injector is provided with an on-off valve for performing control to pass or shut off fuel supplied through a fuel supply pipe, and an electromagnetic actuator for opening and closing the on-off valve. ing. The controller controls the pressure of the common rail and the operation of the electromagnetic actuator of each injector so that the pressurized fuel is injected in each injector under optimal injection conditions for the operating state of the engine. In addition, common rail fuel injection of a type in which engine oil is stored in a common rail as a working fluid and fuel supplied to a pressure increasing chamber in the injector is increased to a predetermined pressure by oil pressure supplied from the common rail to a pressure chamber of the injector. A system has also been proposed.

A conventional fuel pressure operated type common rail fuel injection system will be described with reference to FIG. Fuel tank 7
From the feed pump 6
It is sent to the fuel supply pump 1. The fuel supply pump 1 is a plunger-type variable displacement high-pressure pump driven by an engine, and pumps fuel to a common rail 2. The fuel stored in the common rail 2 in the state of accumulated pressure is
The fuel is supplied to injectors 3 provided for each cylinder according to the model of the engine through a fuel supply pipe 23 constituting a part of the fuel flow path, and is injected from each injector 3 into a corresponding combustion chamber. The fuel supply pump 1 can be a rotary type or a line type pump having a plurality of plungers depending on the model of the engine, other than the illustration.

The fuel supply pump 1 includes a pump driving cam 10 driven by the output of the engine, and a plunger 11 which reciprocates in contact with the pump driving cam 10. The top surface of the plunger 11 is a pump chamber. Twelve wall surfaces are formed. Pump chamber 12 and fuel suction passage 1
3 controls the amount of fuel flowing from the feed pump 6 into the pump chamber 12 through the fuel suction passage 13. A check valve 17 that opens at a predetermined discharge pressure of the fuel supply pump 1 is provided in a fuel discharge path 14 that connects the pump chamber 12 and the common rail 2.

In order to prevent the common rail 2 from abnormally rising due to a system abnormality or the like,
When the pressure becomes higher than a predetermined set pressure, the valve is opened and the fuel in the common rail 2 is discharged to the fuel tank 7 through the discharge path 21 to reduce the common rail pressure.
0 is provided. The common rail pressure Pr detected by the pressure sensor 22 provided on the common rail 2 is:
It is input to a controller 8 which is an electronic control module (ECM) of the engine.

[0007] The injector 3 is hermetically attached to a hole provided in a base such as a cylinder head (not shown) by a seal member. The injector 3 has a needle valve 31 which can reciprocate in the injector body, and an injection hole 32 formed at the tip of the nozzle and opened when the needle valve 31 is lifted to inject fuel into a combustion chamber (not shown). Have. The top surface 33 of the needle valve 31 forms a part of the wall surface of the balance chamber 30 to which the high-pressure fuel from the fuel supply pipe 23 is supplied. Fuel passage 3 connected to fuel supply pipe 23
4 communicates with a fuel reservoir 35 formed around the needle valve 31. The fuel pressure acts on the first tapered surface 36 of the needle valve 31 facing the fuel reservoir 35 to give a lift force to the needle valve 31. On the other hand, the needle valve 31 has a balance chamber 30.
The pressing force based on the fuel pressure in the inside and the returning force of the return spring 47 act. The lift of the needle valve 31 is controlled by the balance between the lift force, the pushing force, and the return force. When the needle valve 31 is opened, the second tapered surface 37 formed at the tip of the needle valve 31 is seated on the tapered valve seat of the injector body, and a passage formed around the needle valve 31 from the fuel reservoir 35 is formed. The communication with the injection hole 32 is closed.

The high-pressure fuel in the common rail 2 is supplied to the balance chamber 30 through a supply path 38 branched from the fuel supply pipe 23, and the fuel in the balance chamber 30 is discharged through a discharge path 40. Supply path 38 and discharge path 40
Are provided with orifices 39 and 41, respectively. The effective passage cross-sectional area of the orifice 41 is
Is set so as to be larger than the effective passage cross-sectional area. Further, the discharge path 40 is connected to the fuel return pipe 4 by the discharge path 40.
An on-off valve 44 for opening the valve 6 is provided.

When the electromagnetic solenoid 45 is operated by the control current from the controller 8 to open the on-off valve 44 provided in the discharge passage 40, the orifice 39 restricts the flow of fuel more strongly than the orifice 41. Therefore, the fuel pressure in the balance chamber 30 decreases. The lift force for lifting the needle valve 31 is applied to the balance chamber 30.
Exceeding the combined force of the pressing force based on the fuel pressure inside and the spring force of the return spring 47, the needle valve 31 is lifted,
Fuel is injected from the opened injection hole 32 into a combustion chamber (not shown). Fuel that has not been consumed for injection and has flowed out of the balance chamber 30 through the discharge path 40 is collected in the fuel tank 7 through the fuel return pipe 46.

The controller 8 includes an engine speed Ne.
Detection signals are input from various sensors 9 as detecting means such as an engine speed sensor for detecting the acceleration, an accelerator depression amount sensor for detecting the accelerator depression amount Ac, and the like. In addition, signals from various sensors for detecting the operating state of the engine, such as a cooling water temperature sensor, an engine cylinder discrimination sensor, a top dead center detection sensor, an atmospheric temperature sensor, an atmospheric pressure sensor, and an intake pipe pressure sensor, are input to the controller 8. Is done.

The controller 8 opens and closes the on-off valve 44 and controls the lift of the needle valve 31 in accordance with a target injection characteristic set based on the detection signal from each of the sensors 9 and a previously determined injection characteristic map. I do. The target injection characteristics are
The timing and the injection amount of the fuel injection from the injector 3 are determined so that the engine output becomes the optimum output according to the operation state of the engine. The timing and amount of fuel injection are determined by the injection pressure and the lift of the needle valve 31 (lift amount, lift period). The drive current determined based on the command pulse output from the controller 8 is sent to the electromagnetic solenoid 45, the on-off valve 44 is controlled to open and close, and the lift of the needle valve 31 is controlled.

More specifically, the relationship between the fuel injection amount of the injector 3 and the pulse width of the command pulse output by the controller 8 is determined by a map using the common rail pressure Pr (the fuel pressure in the common rail 2) as a parameter. I have. Since the fuel injection is started or stopped with a certain time delay from the timing when the command pulse is turned on or off, the injection timing can be controlled by controlling the timing when the command pulse is turned on or off. It is. A constant relationship between the basic injection amount and the engine speed Ne is given in advance as a basic injection amount characteristic map using the accelerator pedal depression amount Ac as a parameter, and the fuel injection amount depends on the operating state of the engine. It is obtained by calculation from the basic injection amount characteristic map. In the illustrated example, only one injector 3 is shown, but the engine is a multi-cylinder engine such as a four-cylinder or six-cylinder engine, and a controller 8 is provided for each injector 3 arranged corresponding to each cylinder. Perform fuel injection control.

Since the injection pressure of the fuel injected from the injector 3 is substantially equal to the pressure of the fuel stored in the common rail 2, the injection pressure is controlled by controlling the common rail pressure Pr. Even if the operating state of the engine is constant, the fuel in the common rail 2 is consumed every time fuel is injected by the injector 3 so that the common rail pressure Pr tends to decrease. If the operating state of the engine changes, the operating state of the engine changes. The common rail pressure Pr required to be optimum is also changed. The controller 8
By controlling the pumping amount of the fuel supply pump 1,
The pressure of the common rail 2 is controlled to a constant pressure or a required pressure according to the operation state of the engine.

In controlling the common rail pressure Pr, a target common rail pressure is determined in accordance with a target fuel injection amount and an engine speed Ne determined in accordance with an operation state of the engine. This is performed by performing feedback control on the pumping amount of the fuel supply pump 1 (the pumping amount accompanying the lift of the plunger) so as to eliminate the deviation from the actual common rail pressure that has been performed.

In the common rail type fuel injection system shown in FIG. 6, prestroke control is known as one of the methods for controlling the amount of pressure supplied by the fuel supply pump 1. The pre-stroke control is performed even when the plunger 11 is in the lift state, during the period when the inlet valve 15 provided in the fuel intake passage 13 is opened.
This method controls the amount of fuel pumped by utilizing the fact that the fuel sucked inside returns through the fuel suction passage 13 and is pumped to the discharge side after the inlet valve 15 is closed. The controller 8 controls the excitation timing of the electromagnetic solenoid 16 to control the fuel pumping period from the closing timing of the inlet valve 15, thereby controlling the pumping amount of the fuel supply pump 1. As a result, the common rail pressure Pr is controlled. Is done. Since the upper limit of the fuel pressure (feed pressure) in the fuel suction passage 13 is limited by the relief valve 18, excess fuel sent by the feed pump 6 is returned to the fuel tank 7 through the relief valve 18 and the return pipe 19.

Incidentally, the target fuel injection amount to be injected from the injector is determined by the common rail pressure as the injection condition and the opening period of the on-off valve provided in the injector. The actual fuel injection amount varies depending on the injector due to mechanical individual variation such as a difference in the injection hole diameter of the injector or variation due to diameter variation. In this case, the operating period of the electromagnetic actuator of the on-off valve of the injector, that is, the pulse width of the command pulse corresponding to the opening time of the on-off valve is adjusted, so that the fuel injection amount for each injection from each injector is adjusted to the target fuel injection amount. Correction control to match the amount is possible. However, since the fuel injection period, that is, the fuel injection rate is different for each injector, combustion variation occurs for each cylinder. In the case of the common rail type fuel injection system, even if the pumping characteristics of the fuel supply pumps are made uniform, the fuel injection amounts cannot be made uniform without eliminating the variation in the injection characteristics of the injectors. In particular, in an operation state in which the engine rotates at a low speed such as idling, the variation in injection among the cylinders appears as variation in combustion, which causes uncomfortable vibration and noise.

[0017]

Therefore, paying attention to the fact that the fuel injection amount is determined not only by the fuel injection period but also by the common rail pressure, the amount of fuel injected from each injector is varied due to individual variations of the injectors and aging. By controlling the common rail pressure for each cylinder even if there is variation in the injected fuel injection amount, the fuel injection for each injection from each injector includes the target fuel injection period and the target fuel injection amount. There is a problem to be solved in that it can be performed under target fuel injection conditions.

[0018]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection system in which a fuel injection amount is varied due to mechanical variation or aging of each injector. The common rail pressure at is increased to a level at which the fuel injection amount injected from each injector is the target fuel injection amount,
By making the fuel injection rate injected from each injector uniform, the variation in fuel injection amount is eliminated to avoid the variation in combustion between cylinders.In particular, even when the engine is running at a low speed such as idling, unpleasant vibration and An object of the present invention is to provide a common rail fuel injection device capable of preventing generation of noise.

According to the present invention, an injector is provided corresponding to each cylinder of an engine and injects fuel, a common rail for storing fuel in a pressure-accumulated state for supplying fuel to each injector, and a pressure of the common rail is increased. A fuel supply pump for sequentially pumping fuel to the common rail in order to perform fuel injection from each of the injectors in a state where the fuel injection is performed, detection means for detecting an operation state of the engine, and target fuel injection based on a detection signal from the detection means. A target fuel injection condition including a period and a target fuel injection amount, and a target fuel pumping condition including a target fuel pumping amount according to the target fuel injection condition are determined, and the target fuel pumping condition and the target fuel injection condition are determined. Control the fuel pumping by the fuel supply pump and the fuel injection from the injector, respectively. A controller for increasing the pressure of the common rail to a pressure at which fuel can be injected under the target fuel injection condition, so that an injection amount deviation between the actual fuel injection amount from the injector and the target fuel injection amount. A common rail type comprising correcting the target fuel pumping amount from the fuel supply pump based on a signal corresponding to the above, and performing feedback control for executing fuel pumping by the fuel supply pump with the corrected target fuel pumping amount. The present invention relates to a fuel injection device.

According to the common rail fuel injection device of the present invention, the controller is configured to control the fuel pumping of the fuel supplied by the fuel supply pump to increase the common rail pressure for each injector immediately before fuel injection from the corresponding injector is performed. The amount is corrected based on a signal corresponding to the injection amount deviation between the actual fuel injection amount and the target fuel injection amount, and the fuel supply pump Karano fuel pumping is feedback-controlled with the corrected fuel pumping amount. Is executed so as to satisfy the target fuel injection condition. Therefore, even if the fuel injection characteristics such as the fuel injection rate vary among the individual injectors, the fuel injection is performed such that the fuel injection condition including the fuel injection period and the fuel injection amount matches the target fuel injection condition. Even if the injection command period to the injectors is set to the same period for each injector, the fuel injection rate in each cylinder is adjusted by adjusting the common rail pressure that is increased for each injector before injection from each injector. The control is performed uniformly so that the fuel injection amount matches the target fuel injection amount.

[0021] The controller corrects the signal corresponding to the injection amount deviation in which the actual fuel injection amount exceeds or falls below the target fuel injection amount to decrease or increase the target fuel pumping amount, respectively. When the actual fuel injection amount is smaller than the target fuel injection amount, the fuel pumping amount is increased and corrected, and in the next fuel injection of the injector, the immediately preceding common rail pressure is controlled to be higher, and during the same fuel injection period. Even so, the fuel injection rate is increased, and the actual fuel injection amount is feedback-controlled so as to increase to the target fuel injection amount. Conversely, when the actual fuel injection amount is larger than the target fuel injection amount, the fuel pumping amount is corrected to be reduced, and at the time of the next fuel injection of the injector, the immediately preceding common rail pressure is controlled to be lower, Even in the same fuel injection period, the fuel injection rate is reduced, and the actual fuel injection amount is feedback-controlled so as to decrease to the target fuel injection amount.

A pressure sensor for detecting a pressure of the common rail, wherein the controller detects, as the signal corresponding to the actual fuel injection amount, a pressure drop of the common rail accompanying fuel injection based on a detection signal from the pressure sensor; Calculate the amount. The relationship between the common rail pressure drop amount and the actual fuel injection amount is obtained in advance as map data, and the actual fuel injection amount is calculated by detecting the common rail pressure drop amount using a pressure sensor.

The controller determines a common rail basic target pressure based on a detection signal from the detection means, and determines a next fuel level based on the common rail basic target pressure and an actual common rail pressure dropped by fuel injection from the injector. The fuel pumping amount is corrected by calculating a basic pumping amount for obtaining the common rail pressure in the injection, and correcting the basic pumping amount based on the signal corresponding to the injection amount deviation.

The controller corrects the basic pumping amount by multiplying the basic pumping amount by a correction coefficient calculated based on the signal corresponding to the injection amount deviation. For example, as a signal corresponding to the actual fuel injection amount, an output shaft rotation fluctuation amount of the engine or an in-cylinder pressure indicating a heat generation amount can be used, and as a correction coefficient calculated based on a signal corresponding to the injection amount deviation, It may be a ratio of a signal corresponding to the target fuel injection amount to a signal corresponding to the actual fuel injection amount.

The controller calculates a final target pressure of the common rail as one of the target fuel injection conditions based on a detection signal from the detection means, and calculates a final target pressure of the common rail and a fuel from the fuel supply pump. A pressure deviation from the pressure of the common rail before the fuel injection from the injector and before the fuel injection is obtained, and the basic pump pumping amount corrected based on the signal corresponding to the injection amount deviation is calculated based on the pressure deviation. Make further corrections. Fuel supply by the plunger of the fuel supply pump may correspond to each injector, that is, each cylinder. In such a case, the common rail pressure after the fuel supply from the fuel supply pump and before the fuel injection from the injector may deviate from the target common rail pressure due to the fuel supply pump side. The fuel pumping amount from the fuel supply pump corrected according to the cylinder-specific fuel injection amount deviation is further corrected according to the cylinder-specific pressure deviation of the common rail pressure accompanying the fuel supply of the fuel supply pump. Therefore, it is possible to perform more accurate common rail pressure control.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a common rail fuel injection device according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an outline of control of a common rail pressure and a fuel feed amount in a common rail fuel injection device according to the present invention. FIG. 2 is an example of a change in common rail pressure for the same injector in the common rail fuel injection device according to the present invention. FIG. The system shown in FIG. 6 can be adopted as the common rail type fuel injection system itself using the fuel supply pump. Therefore, a repeated description of the common rail fuel injection system to which the fuel supply pump according to the present invention is applied will be omitted. The same applies to the injector applied to the common rail type fuel injection system.

The control of the common rail pressure and the fuel feed amount in the common rail type fuel injection device will be described with reference to a flowchart shown in FIG. 1 and a graph showing a change in the common rail pressure shown in FIG. First, referring to the main flow shown in the upper left column of the flowchart shown in FIG. 1, detection signals from various sensors are read from the engine operating state such as the engine speed Ne and the accelerator depression amount Ac (step 1). The target fuel injection amount Qit to be injected from the injector 3, the fuel injection timing, and the common rail basic target pressure Prtb are calculated and determined according to the detected operating state of the engine (step 2).
3, 4). The common rail basic target pressure Prtb is determined based on the target fuel injection amount Qit determined in step 1 and the engine rotation speed Ne. In order to achieve the target fuel injection amount, it is determined based on map data prepared in advance from the operating state of the engine. The higher the target fuel injection amount Qit is, the higher the basic target common rail pressure Prtb is set. In the main flow, steps 1 to 4 are repeated to update the injection conditions at each time in order to respond to the ever-changing operation state of the engine.

Referring to the pump control flow described in the upper right column of the control flow chart shown in FIG. 1, the common rail basic target pressure Prtb (i) calculated in step 4 of the main flow is read (step 11). Each injector (i) 3 is set based on a detection signal sequentially detected from a pressure sensor 22 provided on the common rail 2.
, The actual common rail pressure Pr dropped by the immediately preceding fuel injection, that is, the actual common rail pressure Pr before pumping.
ad (i) is read (step 12). here,
The symbol (i) is assigned a different value for each cylinder, such as a cylinder number, and therefore for each injector. The basic pump pumping amount Qptb (i) is calculated based on the actual common rail pressure Prad (i) before the pumping and the common rail basic target pressure Prtb (i) read in step 11 (step 13). An injection amount feedback correction coefficient KQ (i), which is a learning value calculated and stored in a correction value calculation flow based on a cylinder-by-cylinder injection amount deviation described later, and a pump pressure feed calculated in a cylinder-by-cylinder rail pressure correction coefficient calculation flow described later. The variation correction coefficient k (i) is read (steps 14 and 15). The injection amount feedback correction coefficient KQ read in steps 14 and 15, respectively, is added to the basic pump pumping amount Qptb (i) calculated in step 13.
The final target pumping amount Qptf (i) is calculated by correcting the basic pumping amount Qptb (i) by multiplying (i) by the pumping variation correction coefficient k (i) (step 16). From the final target pumping amount Qptf (i) obtained in step 16, the command pulse timing for prestroke control supplied to the electromagnetic solenoid 16 to close the inlet valve 15 arranged in the fuel supply pump is determined ( Step 17).

Referring to the correction value calculation flow based on the cylinder-by-cylinder injection amount deviation described in the lower left column of the control flowchart shown in FIG. 1, the target fuel injection amount Qit (i) is calculated as in step 2 ( Step 21). Next, the actual fuel injection amount Qia (i) is calculated (step 22).
The actual fuel injection amount Qia (i) is, for example, for the fuel injection from each injector 3, the common rail 2 associated with the fuel injection.
Is obtained from the actual pressure drop amount as a deviation between the pressure before the pressure drop and the pressure after the pressure drop by using map data or a function previously obtained. An injection amount deviation dQi (i) between the target fuel injection amount Qit (i) calculated in step 21 and the actual fuel injection amount Qia (i) calculated in step 22 is calculated (step 23). As a function f of the target fuel injection amount Qit (i) calculated in step 21 and the injection amount deviation dQi (i) calculated in step 23, a correction coefficient KQ (i) based on the injection amount deviation is calculated (step 24). . The correction coefficient KQ (i) calculated in step 24 is stored as a learning value (step 25). For example, when the injection amount deviation dQi (i) is a positive value, the function f has a correction coefficient KQ (i) larger than 1 because the actual fuel injection amount is smaller than the target fuel injection amount. Obtain as a value. By setting the correction coefficient KQ (i) to a value larger than 1, the final target pumping amount is set to a large value, and the common rail pressure before the fuel injection is increased so that the fuel injection amount for the next fuel injection from the same injector is increased. Is increasing. Also,
When the injection amount deviation dQi (i) is a negative value, the correction coefficient KQ (i) is obtained as a value smaller than 1 contrary to the above case. Correction coefficient KQ stored as learning value
(I) is read in step 14 as an injection amount feedback correction coefficient in the pump control flow.

Referring to the flow of calculating the correction coefficient of the cylinder-specific rail pressure described in the lower right column of the control flowchart shown in FIG. 1, the common rail final target pressure Prtf
(I) is read (step 31), and the actual common rail pressure Pr recovered after the fuel supply by the fuel supply pump is recovered.
au (i) is calculated (step 32). From common rail final target pressure Prtf (i) to actual common rail pressure P
The pressure deviation ΔPr (i) obtained by subtracting rau (i) is calculated (step 33). Deviation of common rail pressure ΔPr
A correction coefficient k (i) is calculated based on (i) (step 34). Correction coefficient k (i) calculated in step 34
Is stored as a learning value (step 35). When the pressure deviation is a positive value, the actual common rail pressure Prau (i) was lower than the common rail final target pressure Ptrf (i) due to the variation in the amount of pumping of the plunger. i) is determined as a value larger than 1. By setting the correction coefficient k (i) to a value larger than 1, the final target pumping amount is set to a large value, and the common rail pressure before fuel injection at the next fuel pumping from the same plunger is increased to a required height. Can be. When the pressure deviation ΔPr (i) is a negative value, the correction coefficient k (i) is obtained as a value smaller than 1 contrary to the above case. Correction coefficient k (i) stored as learning value
Is read in step 15 as a pump pressure feeding variation correction coefficient in the pump control flow. It should be noted that the injector 3 and the plunger 11 do not always correspond one-to-one depending on the type of engine, and in that case, the symbol i indicates the injector 3 and the plunger 11 (or a single In the case of the plunger described above, the cam peak of the operation cam is associated with the plunger.

As described above, according to the common rail fuel injection device, both the degree of decrease of the common rail pressure Pr due to the fuel injection from the injector 3 and the degree of recovery of the common rail pressure Pr due to the fuel supply from the fuel supply pump 1 And the fuel injection period is adjusted to the target fuel injection period. Therefore, the fuel injection time ratio in the fuel injection period, that is, the variation in the fuel injection amount injected from each injector while the fuel injection rate is aligned for each cylinder. The common rail pressure by the fuel supply by the fuel supply pump is controlled so as to eliminate the pressure. Since the fuel injection amount injected from any of the injectors is secured to a predetermined target fuel injection amount determined based on the operation state of the engine, the fuel state in each combustion chamber varies, and the engine is uncomfortable. No undesired vibration or noise is generated, and unpleasant vibration or noise of the engine due to combustion variation can be prevented. In the embodiment described above, the basic pumping amount Q
Although correction was made as a correction coefficient to be multiplied by ptb (i), a correction term was added to the basic pumping amount Qptb (i).
Obviously, a correction may be made which adds as a function of the injection quantity deviation dQi (i) and the rail pressure deviation.

In the fuel supply pump, the change of the fuel pumping period by the pre-stroke control will be described with reference to an example of the fuel supply pump shown in FIGS. FIG. 3 is a sectional view showing an example of a fuel supply pump used in the common rail fuel injection device according to the present invention;
FIG. 4 is an enlarged sectional view showing a main part including an inlet valve of the fuel supply pump shown in FIG. 3, and FIG. 5 is an operation timing chart of the fuel supply pump shown in FIGS. Except for the specific configuration of the fuel supply pump, the common rail fuel injection system itself using the fuel supply pump can adopt the system shown in FIG. Therefore, a repeated description of the common rail fuel injection system to which the fuel supply pump according to the present invention is applied will be omitted. The same applies to the injector applied to the common rail type fuel injection system. Elements that are the same as the elements other than the fuel supply pump used in the common rail type fuel injection system shown in FIG. 6 are denoted by the same reference numerals, and description thereof will not be repeated.

FIG. 3 is a longitudinal sectional view schematically showing the entire fuel supply pump 50 used in the common rail fuel injection device according to the present invention. In a housing 52 of the high-pressure fuel pump 50, a camshaft 53 driven by a crankshaft of the engine via a suitable transmission means such as a belt is rotatably supported. The cam drive shaft is provided with a pump drive cam. On the outer periphery of the cam 54 formed integrally with the camshaft 53,
A rotating wheel 56 is rotatably mounted via a bearing 55, and the cam 54, the bearing 55, and the rotating wheel 56 are housed in a cam chamber 57 of the housing 52. Cam room 57
A plunger 60 that is pressed against the rotating wheel 56 by a plunger spring 59 is disposed in a bore 58 of the housing 52 communicating with the housing 52 so as to be able to move up and down. A tappet 61 is formed at the tip of the plunger 60.
Is engaged with one end of the plunger spring 59 on one side and receives the spring force of the plunger spring 59, and the rotating wheel 5 on the other side.
6 abuts.

A cylinder 62 is mounted on the upper end surface of the housing 52, and the housing 52 and the cylinder 62 constitute a pump body. A plunger 60 is slidably fitted in a cylinder bore 63 formed in the cylinder 62. A discharge hole 64 is formed in the upper part of the cylinder 62 from the lateral direction, and a discharge valve 65 formed of a check valve is disposed in the discharge hole 64. The plunger 60 is
The pump chamber 66 reciprocates slidably in a cylinder bore 63 formed in the cylinder 62, and a pump chamber 66 is defined above the cylinder bore 63 by the top of the plunger 60.

The low-pressure fuel discharged from the feed pump 6 to the fuel suction passage 13 is supplied to a fuel supply passage 71 formed in the housing 52, an annular passage 72 formed between the housing 52 and the cylinder 62, and an annular passage 72. The fuel is supplied to a fuel reservoir 74 formed on the upper surface of the housing 52 through a fuel suction passage 73 extending from the upper portion of the housing 52 to the fuel reservoir 74. A relief valve 18 is provided in a passage branched from the fuel intake passage 13, and fuel pressure equal to or higher than a set pressure is returned to the tank 7 through the relief valve 18. Fuel pool 7
4 is connected to the pump chamber 66 through an inlet valve 80 as described later.

On the other hand, the female screw portion 7 formed in the discharge hole 64
5, one end of a fuel discharge path 14 reaching the common rail 2 is screwed and connected. The fuel pressurized in the pump chamber 66 opens the discharge valve 65 with the increased fuel pressure, and reaches the common rail 2 through the fuel discharge path 14. The fuel leaking around the plunger 60 is collected through the drain port 79 separately from the lubricating oil.

The cylinder 62 has an inlet valve 80 for shutting off / communicating the fuel reservoir 74 and the pump chamber 66.
And a control valve 51 for operating the inlet valve 80 are provided. Inlet valve 80 based on FIG.
And the control valve 51 will be described. Inlet valve 8
0 is a valve head 8 disposed inside the pump chamber 66.
1 and a valve stem 82 extending outside the cylinder 62 and inside the control valve 51. Inlet valve 80
Closes when the valve face 83 of the valve head 81 contacts the valve seat 84 formed in the cylinder 62,
The space between the fuel pool 74 and the pump chamber 66 is shut off. The valve stem 82 is inserted through an insertion hole 85 formed in the cylinder 62 via a gap 86, and is guided above the insertion hole 85 into a guide hole 88 of a bush 87 having a tubular shape. The bush 87 functions as a lower seat of the inlet valve 80.

A snap ring 89 is fitted on the outer periphery of the upper part of the valve stem 82, and a spring guide 90, which also serves as a spring receiver, fitted on the valve stem 82 is provided with a snap ring 89.
, The position with respect to the valve stem 82 is regulated. A suction valve spring 91 is mounted between the bush 87 and the spring guide 90 in a compressed state. The suction valve spring 91 seats the valve head 81 on the valve seat 84 and constantly urges the inlet valve 80 in the valve closing direction. A cap 92 is hermetically attached to the upper part of the cylinder 62 by a seal ring so as to cover the fuel reservoir 74, and the upper part of the valve stem 82 is housed in a central hole 93 inside the cap 92. The valve stem 82 fits into the guide hole 88 of the bush 87 and the top 9 of the valve stem 82
8 fits into the bore 94, so that the plunger 60
, The accuracy (coaxiality, concentricity) of the valve stem 82 is ensured even when a fluid force acts on the inlet valve 80.

In the center of the cap 92, a bore 94 into which the top 98 of the valve stem 82 of the inlet valve 80 fits is formed. The control chamber 95 is formed by the wall surface of the bore 94 and the top wall of the top 98 of the valve stem 82. Are formed. The cap 92 has a communication passage 96 connected to the fuel reservoir 74.
The communication path 96 can be communicated through a communication path 97 formed at the bottom of the bore 94. At the time of communication, the fuel pressure of the low-pressure fuel sent from the feed pump 6 acts on the pressure control chamber 95. are doing. A control valve 51 is hermetically mounted on the upper surface of the cap 92 to connect the communication path 96 and the communication path 97 and open and close the opening of the communication path 97.

The control valve 51 has a housing 101 mounted on the upper surface of the cap 92 in a sealed state by a seal ring. The control valve 51 is configured as an electromagnetic valve, and energizes a solenoid 102 that is excited by a signal from a controller, an armature 103 that is activated by excitation and demagnetization of the solenoid 102, and an armature 103 inside the housing 101. A return spring 104 is provided. The front end of the armature 103 is an opening / closing valve portion 105, and the control valve 51 opens or closes the open end of the communication path 97 formed in the cap 92 to connect the control chamber 95 to the low pressure side, Alternatively, it is configured as a two-way valve that can be closed.
When the solenoid 102 is excited, the armature 103
Is lowered against the spring force of the return spring 104, the on-off valve portion 105 at the tip closes the open end of the communication path 97, and the control chamber 95 is closed. Further, when the solenoid 102 of the control valve 51 is demagnetized, the armature 103 is raised by the return spring 104, and the opening / closing valve portion 105 opens the open end of the communication path 97 so that the control chamber 95 can communicate with the low pressure side.

Next, the operation of the fuel supply pump shown in FIGS. 3 and 4 will be described based on the timing chart shown in FIG. FIG. 5 is a diagram showing an example of an operation timing chart of the fuel supply pump 50 with the horizontal axis as a time axis. FIG. 5A is a graph showing the on / off state of the control valve operation signal, and FIG.
FIG. 5C is a graph showing how the displacement of the control valve changes when the control valve is controlled in the manner of the operation signal shown in FIG. 5A; FIG. 5C shows the state when the control valve is controlled in the manner shown in FIG. FIG. 5 is a graph showing a state of lift of the inlet valve of FIG.
FIG. 5D is a graph showing the displacement of the plunger of the fuel supply pump, and FIG. 5E is a graph showing the flow rate of the fuel discharged from the fuel supply pump.

The low-pressure fuel delivered by the feed pump 6 is supplied to a fuel reservoir 74 through a fuel supply passage 71, an annular passage 72, and a fuel suction passage 73. FIG.
(A) to (E), when the control valve 51 is off, the armature 83 opens the communication path 97 by the action of the return spring 104, so that the pressure control chamber 95 is opened. Communicates with the low pressure side, and the pressure control chamber 95
Low-pressure fuel can flow into and out of the interior. As the plunger 60 descends, the pressure in the pump chamber 66 becomes negative, so that the inlet valve 80 is opened against the set force of the suction valve spring 91 by the balance of the fluid pressure acting on the inlet valve 80. Valve and fuel pool 7
The fuel in 4 is filled with a gap 86 formed between the groove 87 a at the lower end of the bush 87 and the insertion hole 85 and the valve stem 82.
Through the space between the valve face 83 of the valve head 81 and the valve seat 84 and into the pump chamber 66. That is, the inlet valve 80 is lifted in a direction in which the space between the valve face 83 and the valve seat 84 opens in response to the inflow of fuel.

At time t _{1 when the} plunger 60 starts displacing in the minus direction from the reference point, the operation signal of the control valve 51 is turned on. Control valve 51 starts the displacement in a closing direction from the time t _1, the on-off valve unit 105 at time t ₂
Is displaced until the opening of the communication path 97 is completely closed, and the pressure control chamber 95 is completely closed. Therefore, at time t _2,
The displacement of the lift in the opening direction of the inlet valve 80 stops, and the lift of the inlet valve 80 enters a full lift state. Until the time t ₃ when the plunger 60 reaches the bottom dead center, the fuel is sucked into the pump chamber 66 through the lifted inlet valve 80.

After time t _{3 when} the plunger 60 reaches the bottom dead center (BDC), the fuel in the pump chamber 66 is pushed out by the plunger 60 going to rise. At this time, since the fuel in the pressure control chamber 95 does not flow out, the inlet valve 80 cannot be closed, and the open state is maintained. Even if the fuel in the pressure control chamber 95 becomes high pressure, the cross-sectional area of the communication path 97 is small,
The small solenoid 102 can sufficiently oppose the internal fuel pressure, and does not push up the armature 103 against the operating force of the solenoid 102. Therefore, the fuel does not flow backward from the inlet valve 80 in the open state to the low pressure side such as the fuel reservoir 74 and the fuel suction passage 73, and is not discharged to the fuel discharge passage 14 by opening the discharge valve 65. The amount corresponding to the amount of fuel that has flowed back to the low pressure side such as the fuel suction passage 13 is returned to the tank 7 via the relief valve 18.

At time t _{4 when the} plunger 60 is rising through the bottom dead center (BDC), the operation signal of the control valve 51 is switched off. Time t ₄ is a command pulse timing for pre-stroke control. Armature 103 of the control valve 51 is raised by the spring force of the return spring 104, closing valve 105 starts to open the communication passage 97, the control valve 51 at time t ₅ is completely open the pressure control chamber 95. Since the pressure control chamber 95 communicates with the low pressure side and the pressure is reduced, the inlet valve 80 is raised by the pressure action of the fuel pressurized in the pump chamber 66 and the inlet valve 80 starts closing. Inlet valve 80 is fully closed at time t _6. Therefore, after the inlet valve 80 starts closing, the backflow of the fuel in the pump chamber 66 to the low pressure side starts to be stopped, and the pressurized fuel in the pump chamber 66 is discharged to the fuel discharge passage 14 through the discharge valve 65. beginning to be, the top dead center the plunger 60 at time t ₇ (TD
Until C), the fuel in the pump chamber 66 is discharged to the fuel discharge path 14.

In FIGS. 5A to 5C and 5E,
The graph shown by the broken line shows the state of each change when the operation timing of the control valve 51 from ON to OFF is delayed. That is, if the OFF operation timing of the control valve 51 is delayed (time t ₈ ), the displacement of the armature 103 of the control valve 51 is also delayed, and the opening timing t ₉ of the control valve 51 and the timing of closing the inlet valve 80 (time t _10). ) Is also late. Therefore, since late also timing the fuel from the pump chamber 66 begins to discharge by opening the discharge valve 65 to the fuel discharge passage 14, the discharge from the pump chamber 66 by the time t ₇ the plunger 60 reaches the top dead center (TDC) The amount of fuel discharged is reduced.
Conversely, if the operation timing of the control valve 51 from ON to OFF is advanced, the timing at which the inlet valve 80 closes is also earlier, and the amount of fuel discharged from the pump chamber 66 can be increased. Thus, by controlling the operation timing of the control valve 51 from ON to OFF, the pump chamber 6 is controlled.
6 can be controlled.

In this embodiment, the actual fuel injection amount is calculated from the common rail pressure drop amount, and the injection amount deviation is obtained from the deviation from the target fuel injection amount. As proposed in Japanese Unexamined Patent Publication No. Hei 11-96960, the amount of heat generated in the combustion chamber is obtained from the rotation fluctuation of the engine output shaft, and a deviation from the target heat generation amount is used as a signal representing the injection amount deviation. A correction coefficient for correcting the fuel pumping amount from the supply pump may be calculated. In addition, the in-cylinder pressure sensor disposed in the cylinder, using the heat generation rate in the cylinder detected by a sensor such as an ion sensor, to determine the amount of heat generated in the combustion chamber, according to the same procedure as above It is also possible to calculate a correction coefficient for correcting the fuel pumping amount from the fuel supply pump.

[0048]

According to the common rail fuel injection system of the present invention, the controller performs fuel injection from each injector based on the injection amount deviation between the actual fuel injection amount and the target fuel injection amount for each injector. Feedback control for correcting the fuel delivery amount for increasing the common rail pressure immediately before the injection to recover the common rail pressure immediately before the injection of each injector to a level at which the fuel injection amount injected from each injector becomes the target fuel injection amount. Control. Therefore, even if the fuel injection amount injected from each injector varies due to individual variations or changes in the diameter of the injector, the fuel injection period and the fuel injection rate and the fuel injection amount from the injector remain unchanged without changing the fuel injection period. Therefore, even in an operation state in which the engine rotates at a low speed such as idling, it is possible to eliminate fuel variation among the cylinders and to prevent generation of unpleasant vibration and noise. Further, with respect to the common rail pressure after fuel supply from the fuel supply pump, the variation caused by the fuel supply pump side can be eliminated by correcting the fuel supply amount based on the deviation of the recovery pressure of the common rail.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of control of a common rail pressure and a fuel pumping amount in a common rail fuel injection device according to the present invention.

FIG. 2 is a graph showing an example of a change in common rail pressure for the same injector in a common rail fuel injection device according to the present invention.

FIG. 3 is a sectional view showing an example of a fuel supply pump used in the common rail fuel injection device according to the present invention.

FIG. 4 is an enlarged sectional view showing a part including an inlet valve of the fuel supply pump shown in FIG. 3;

FIG. 5 is an operation timing chart of the fuel supply pump shown in FIGS. 3 and 4;

FIG. 6 is a schematic diagram illustrating a conventional common rail fuel injection system.

[Explanation of symbols]

 1,50 fuel supply pump 2 common rail 3 injector 8 controller 9 sensor 10 pump drive cam 11,60 plunger 12,66 pump chamber 13,73 fuel suction path 15,80 inlet valve 22 pressure sensor 51 control valve 52 housing 62 cylinder 82 valve Stem 94 Bore 95 Pressure control chamber Qit Target fuel injection quantity Qia Actual fuel injection quantity dQi Injection quantity deviation Pr Common rail pressure Prad Actual common rail pressure (before fuel pumping) Prau Actual common rail pressure (after fuel pumping) Qptb Basic pump pumping quantity Qptf Final target Pump pumping amount KQ Correction coefficient (for injection amount deviation correction) k Correction coefficient (for common rail pressure deviation correction)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02M 47/00 F02M 47/00 E 59/20 59/20 DF Term (Reference) 3G066 AA07 AC09 AD02 BA22 BA53 CB12 CC05U CD26 CE22 CE29 DA01 DA04 DA06 DC04 DC09 DC14 DC18 DC19 DC22 3G301 HA02 JA17 JA37 LB13 LC01 MA11 MA18 NA08 NC02 ND01 ND21 PA09Z PA10Z PB03Z PB08A PC01Z PE01Z PE05Z PE08Z PF03Z

Claims (6)

[Claims] An injector is provided corresponding to each cylinder of an engine and injects fuel, a common rail for storing fuel in a pressurized state for supplying fuel to each injector, and a state in which the pressure of the common rail is increased. In order to perform fuel injection from each of the injectors, a fuel supply pump for sequentially pumping fuel to the common rail, detection means for detecting an operating state of the engine, and a target fuel injection period based on a detection signal from the detection means. A target fuel injection condition including a target fuel injection amount and a target fuel pumping condition including a target fuel pumping amount corresponding to the target fuel injection condition are obtained, and the target fuel pumping condition and the target fuel injection condition are respectively determined according to the target fuel pumping condition A controller for controlling fuel pumping by the fuel supply pump and fuel injection from the injector; And the controller comprises:
In order to increase the pressure of the common rail to a pressure at which fuel can be injected under the target fuel injection condition, the fuel is set based on a signal corresponding to an injection amount deviation between the actual fuel injection amount from the injector and the target fuel injection amount. A common rail type fuel injection device comprising correcting the target fuel pumping amount from a supply pump, and performing feedback control for executing fuel pumping by the fuel supply pump with the corrected target fuel pumping amount. 2. The controller according to claim 1, wherein the controller corrects the signal corresponding to the injection amount deviation in which the actual fuel injection amount exceeds or falls below the target fuel injection amount to decrease or increase the target fuel pumping amount, respectively. 2. The common rail fuel injection device according to claim 1, comprising: 3. A pressure sensor for detecting a pressure of the common rail, wherein the controller detects the pressure of the common rail according to a fuel injection based on a detection signal from the pressure sensor as the signal corresponding to the actual fuel injection amount. 3. The common rail fuel injection device according to claim 1, wherein the amount of pressure drop is calculated. 4. The controller determines a common rail basic target pressure based on a detection signal from the detection means, and determines a next common rail basic target pressure based on the common rail basic target pressure and an actual common rail pressure dropped by fuel injection from the injector. Calculating the basic pumping amount for obtaining the common rail pressure in the fuel injection, and correcting the fuel pumping amount by correcting the basic pumping amount based on the signal corresponding to the injection amount deviation. 4. The common rail fuel injection device according to claim 3, comprising: 5. The controller according to claim 1, wherein the controller corrects the basic pumping amount by multiplying the basic pumping amount by a correction coefficient calculated based on the signal corresponding to the injection amount deviation. 5. The common rail fuel injection device according to 4. 6. The controller calculates a final target pressure of the common rail as one of the target fuel injection conditions based on a detection signal from the detection means, and calculates a final target pressure of the common rail and the fuel supply pump. A pressure deviation from the pressure of the common rail after the fuel pumping and before the fuel injection from the injector is obtained, and the basic pump pumping amount corrected based on the signal corresponding to the injection amount deviation is converted to the pressure deviation. The common rail fuel injection device according to any one of claims 1 to 5, further comprising a correction based on the correction value.