JP5040692B2 - In-cylinder direct injection internal combustion engine fuel supply device - Google Patents

Description

  The present invention relates to a fuel supply device for a direct injection type internal combustion engine, and particularly to a technique for reducing pressure loss in a high-pressure fuel pump.

Conventionally, in a direct injection type internal combustion engine, a high-pressure fuel pump as shown in Patent Document 1 is used for supplying high-pressure fuel to a fuel injection valve (injector).
This high-pressure fuel pump changes the volume of the pump chamber by the reciprocating movement of the plunger driven by a cam, sucks fuel into the pump chamber through the suction side one-way valve in the plunger suction stroke, and in the plunger discharge stroke. A plunger pump that discharges fuel in the pump chamber through a discharge-side one-way valve, and the suction-side one-way valve that is provided for the suction-side one-way valve, regardless of the pressure in the pump chamber due to electromagnetic force generated by energization And a solenoid capable of holding the valve in an open state.

Then, the solenoid is energized until an arbitrary timing of the discharge stroke of the plunger, the suction side one-way valve is kept open, and the suction side one-way valve is closed after the solenoid is energized. Thus, the discharge operation of the plunger pump is controlled by controlling the valve closing timing (the valve closing period in the discharge stroke) of the suction side one-way valve by controlling the solenoid energization end timing. To control.
JP 2007-032323 A

  By the way, in a direct injection type internal combustion engine, since fuel injection cannot be performed until the fuel pressure reaches the injection permission fuel pressure, it is required to improve the boosting characteristic of the high-pressure fuel pump in order to improve startability.

  Therefore, in the present invention, in the conventional high-pressure fuel pump, the suction side one-way valve is opened by the suction force generated by the pressure drop in the pump chamber during the plunger suction stroke, and the fuel is sucked. Focusing on the fact that the pressure loss corresponding to the set load of the spring of the one-way valve occurs during the intake stroke, and aims to improve the boosting characteristic of the high-pressure fuel pump by reducing this pressure loss .

Therefore, in the present invention, in order to control the discharge amount of the plunger pump, the energization start timing of the solenoid provided in the one-way valve on the suction side is switched between the initial stage of the intake stroke and the late stage of the intake stroke according to the operating conditions. The operation condition in which the energization start timing of the solenoid is set to the initial stage of the suction stroke is set so that at least the fuel pressure on the discharge side is lower than a predetermined value .

  According to the present invention, energization of the solenoid is started from the beginning of the intake stroke, and the intake-side one-way valve is held open, so that the intake-side one-way valve is held open by the solenoid during the intake stroke. Since the electromagnetic force can counteract the set load of the spring of the one-way valve, the pressure loss can be reduced accordingly. As a result, it is possible to improve the boosting characteristics at the start, and to deal with the occurrence of vapor in the pump chamber.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a fuel supply device for a direct injection type internal combustion engine, showing an embodiment of the present invention.
This internal combustion engine is an in-cylinder direct injection spark ignition internal combustion engine, and there are a homogeneous operation mode and a stratified operation mode as operation modes (combustion modes). In the homogeneous operation mode, fuel is injected during the intake stroke, and a homogeneous air-fuel mixture is formed in the entire combustion chamber, thereby causing homogeneous combustion at a stoichiometric or lean air-fuel ratio (A / F = 20 to 30). . On the other hand, in the stratified operation mode, fuel injection is performed in the compression stroke, and a stratified air-fuel mixture is formed around the spark plug, so that the air / fuel ratio (A / F = 30 to In step 40), stratified combustion is performed.

A fuel supply device for the internal combustion engine will be described.
A low pressure fuel pump 2 is provided in the fuel tank 1. Specifically, the electric low-pressure fuel pump 2 that pumps the fuel in the fuel tank 1, the fuel filter 3 that filters the fuel on the discharge side thereof, and the discharge side pressure is kept constant by returning the surplus fuel to the fuel tank 1. A low-pressure pressure regulator 4 that is adjusted to (usually about 0.3 to 0.5 MPa) is provided.

The fuel pumped by the low pressure fuel pump 2 is supplied to the high pressure fuel pump 8 through the fuel filter 6 and the fuel damper 7 by the low pressure fuel passage 5.
The high-pressure fuel pump 8 is mainly composed of a plunger pump 9. The plunger pump 9 changes the volume of the pump chamber 12 by the reciprocating motion of the plunger 11 driven by the cam 10, and sucks fuel into the pump chamber 12 through the suction side one-way valve 13 in the intake stroke of the plunger 11. 11, the fuel in the pump chamber 12 is discharged through the discharge-side one-way valve 14 in the discharge stroke. The pump drive cam 10 is connected to the engine cam shaft.

  The high pressure fuel pump 8 further includes a solenoid 15. The solenoid 15 is provided for the suction-side one-way valve 13 and can hold the suction-side one-way valve 13 in an open state regardless of the pressure in the pump chamber 12 by electromagnetic force generated by energization.

FIG. 2 shows a specific structure of the high-pressure fuel pump 8.
The suction side discharge valve (the valve body) 13 is provided in the suction side passage of the plunger pump 9 and is urged in the valve closing direction by the spring 13s, and is opened against the spring 13s by the negative pressure in the pump chamber 12. On the other hand, the solenoid 15 is energized to open regardless of the pressure in the pump chamber 12. That is, it functions as a one-way valve in the suction direction when the solenoid 15 is not energized, and is kept fully open in any direction when the solenoid 15 is energized.

  The discharge-side one-way valve (the valve body) 14 is provided in the discharge-side passage of the plunger pump 9 and is urged in the valve closing direction by the spring 14s, and resists the spring 14s by the positive pressure in the pump chamber 12. It is configured to open. That is, it functions as a one-way valve in the discharge direction.

  Here, the solenoid 15 is energized until an arbitrary timing of the discharge stroke of the plunger 11, the suction side one-way valve 13 is held open, and the suction side one-way valve 13 is closed after the solenoid 15 is energized. Thus, the discharge operation is started, and the valve closing timing (the valve closing period in the discharge stroke) of the suction side one-way valve 13 is controlled by controlling the energization end timing of the solenoid 15. The amount is controlled (see FIG. 3A).

  The discharge side of the high-pressure fuel pump 8 (plunger pump 9) (the outlet side of the discharge-side one-way valve 14) is connected to a fuel pressure accumulation chamber (common rail) 17 by a high-pressure fuel passage 16 with an orifice.

The fuel pressure accumulating chamber 17 is connected to the fuel injection valves 19 corresponding to the number of cylinders via branch pipes 18 that branch from now on, and these fuel injection valves 19 face the combustion chambers of the cylinders of the engine.
In addition, a fuel pressure sensor 20 that detects the fuel pressure in the pressure accumulation chamber 17 is attached to the fuel pressure accumulation chamber 17, and a signal thereof is input to the ECU 100.

  Furthermore, one end side of the relief valve 22 is connected to the communication passage 21 with the fuel pressure accumulating chamber 17, and the other end side of the relief valve 22 is connected to the low pressure fuel passage 5 on the suction side of the high pressure fuel pump 8 by the return passage 23. is doing. The relief valve 22 is for opening the valve when the fuel pressure in the fuel pressure accumulation chamber 17 is excessively increased and releasing the pressure (the valve opening pressure is about 18 MPa).

  Here, in order to control the fuel pressure injected from the fuel injection valve 19, the fuel pressure in the fuel accumulator chamber 17 is controlled. This fuel pressure is determined by the signal from the ECU 100 at the end of energization of the solenoid 15 (suction in the discharge stroke). By controlling the discharge amount of the high-pressure fuel pump 8 (plunger pump 9) by controlling the closing timing of the side one-way valve 13), the balance of the flow rate balance between the pump discharge amount and the fuel injection amount is arbitrary. Feedback control is performed to the target fuel pressure (usually about 3 to 15 MPa). Note that the target fuel pressure is set to be larger at the high rotation / high load side and smaller at the low rotation / low load side according to the operating conditions (the number of rotations and the load).

Next, the energization start timing of the solenoid 15 will be described with reference to FIGS.
FIG. 3A shows the suction / discharge operation of the plunger pump (and the energization start timing of the solenoid) during normal control.

In the suction stroke in which the plunger 11 descends from the top dead center (TDC), the suction side one-way valve 13 is opened by the negative pressure in the pump chamber 12, and fuel is sucked into the pump chamber 12.
Thereafter, immediately before the plunger 11 reaches bottom dead center (BDC), the solenoid ON signal is raised and the solenoid 15 is energized. This is because the suction-side one-way valve 13 is held in the closed state by the bottom dead center (BDC) regardless of the pressure in the pump chamber 12. Therefore, the energization start timing of the solenoid 15 is late in the intake stroke, and at the latest, the intake side one-way valve 13 is opened to the bottom dead center (BDC) by electromagnetic force. This is an energization start time that has been generally used conventionally.

  After the plunger 11 reaches the bottom dead center (BDC), it rises and enters the discharge stroke. However, since the suction side one-way valve 13 is held open by the solenoid 15, the plunger 11 is lifted to raise the pump chamber. The fuel in 12 flows backward to the suction side, and as a result, the pressure in the pump chamber 12 does not increase, and the discharge-side one-way valve 14 is kept closed and the discharge operation is not performed.

  Thereafter, the solenoid ON signal is terminated at an arbitrary timing of the discharge stroke, and energization of the solenoid 15 is terminated. Then, the suction side one-way valve 13 is closed, and thereafter, the pressure in the pump chamber 12 rises due to the rise of the plunger 11, and the fuel in the pump chamber 12 is discharged through the discharge side one-way valve 14. Therefore, the amount of fuel corresponding to the closing timing of the suction-side one-way valve 13 due to the end of energization of the solenoid 15, specifically the closing period of the suction-side one-way valve 13 in the discharge stroke, is discharged.

FIG. 3B shows the suction / discharge operation of the plunger pump (and the start of energization of the solenoid) during the pressure loss reduction control.
The difference from the normal control is that the energization start timing of the solenoid 15 is the initial stage of the intake stroke, particularly the top dead center (TDC). That is, the solenoid ON signal is raised at the beginning of the intake stroke, particularly at top dead center (TDC), and energization of the solenoid 15 is started. As a result, the suction side one-way valve 13 is maintained in an open state by electromagnetic force from the beginning of the suction stroke.

  In this way, the suction-side one-way valve 13 is forcibly opened by the electromagnetic force of the solenoid 15 during the suction stroke of the plunger 11, so that there is no pressure loss for opening the valve by fluid force, and the pressure loss can be reduced. .

  Therefore, the energization start timing in FIG. 3B is the energization start timing for reducing the pressure loss. However, since the energization time becomes longer, the power consumption increases. Therefore, the pressure loss reduction control of FIG. 3B is switched only when the pressure loss reduction control is particularly necessary depending on the operating conditions. 3 (A) normal control.

FIG. 4 is a flowchart of switching control between normal control and pressure loss reduction control.
In S <b> 1, it is determined whether or not it is a start time, that is, whether it is a start time or other normal operation.
In the case of starting, the process proceeds to S2, and it is determined whether or not it is a homogeneous start at an extremely low temperature (about −30 to −40 ° C.), that is, whether it is a homogeneous start at an extremely low temperature or other stratified start.

  In the in-cylinder direct injection spark ignition type internal combustion engine of the present embodiment, the engine is started by stratified combustion (compression stroke injection), but it is difficult to start by stratified combustion at extremely low temperatures, so it is homogeneous only at extremely low temperatures. The engine is started by combustion (intake stroke injection).

  At the time of homogenous starting at a very low temperature, the process proceeds to S5, and the flag F = 1 is set for pressure loss reduction control. At the very low temperature homogeneous start (intake stroke injection), the required injection amount exceeds the maximum discharge amount of the high pressure fuel pump, and the suction side one-way valve 13 is closed over the entire discharge stroke, so that the low pressure fuel pump 2 This is because it is desirable to reduce the pressure loss in the intake stroke of the high-pressure fuel pump as much as possible.

  In the case of normal stratification start-up, the process proceeds to S3, where the cooling water temperature (water temperature) is detected, and it is determined whether or not the first predetermined value (for example, 110 ° C.) or higher. This is a hot restart, and determines whether the fuel temperature (fuel temperature) is higher than the vapor generation temperature using a water temperature correlated with this instead of the fuel temperature.

  When the water temperature is 110 ° C. or higher, it is considered that vapor is generated. Therefore, the process proceeds to S5, and the flag F = 1 is set for pressure loss reduction control. This is to cope with the generation of vapor and reduce the pressure drop.

When the water temperature is less than 110 ° C., the process proceeds to S4, where the fuel pressure (fuel pressure) is detected, and it is determined whether or not the fuel pressure is lower than the injection permitted fuel pressure (for example, 3 MPa) at the stratified start (compression stroke injection).
When the fuel pressure is lower than the injection permission fuel pressure, the process proceeds to S5 in order to improve the boosting characteristic, and the flag F = 1 is set for pressure loss reduction control. This is because the fuel pressure can be increased more quickly and injection (compression stroke injection) can be performed earlier.

  If the fuel pressure is higher than the permitted fuel pressure for injection (ie, at the time of stratification start, there is no risk of vapor generation from the water temperature, and the fuel pressure is higher than the permitted fuel pressure for injection), the process proceeds to S6 and flag F = 0 for normal control. And

On the other hand, if the determination at S1 is normal operation, the process proceeds to S7.
In S7, the cooling water temperature (water temperature) is detected, and it is determined whether or not it is equal to or higher than a second predetermined value (for example, 100 ° C.). This determines whether or not the fuel temperature (fuel temperature) is higher than the vapor generation temperature using a water temperature correlated with the fuel temperature instead of the fuel temperature. However, since the correlation between the water temperature and the fuel temperature is different between the start time and the normal operation, the determination water temperature (100 ° C.) during the normal operation is made lower than the determination water temperature (110 ° C.) at the start time.

  When the water temperature is 100 ° C. or higher, it is considered that vapor is generated. Therefore, the process proceeds to S8, and flag F = 1 is set for pressure loss reduction control. This is to cope with the generation of vapor and reduce the pressure drop.

When the water temperature is less than 100 ° C., the process proceeds to S9, and flag F = 0 is set for normal control.
FIG. 5 is a flowchart of control of energization start timing (energization start angle) and energization end timing (energization end angle) of the solenoid.

In S11, the value of the flag F is determined, and it is determined whether or not F = 1 (there is a pressure loss reduction control request).
When F = 0 and there is no pressure loss reduction control request, that is, in the case of normal control, the process proceeds to S12, and the energization start angle is set by referring to the map from the engine speed Ne and the required fuel injection amount Qf. The energization start angle set here is the timing at which the suction side one-way valve 13 is opened to the bottom dead center (BDC) by the electromagnetic force at the latest in the later stage of the suction stroke.

When F = 1 and there is a pressure loss reduction control request, that is, in the case of pressure loss reduction control, the process proceeds to S13, and the energization start angle is set to the initial stage of the intake stroke, particularly top dead center (TDC).
After the energization start angle is set in S12 or S13, the process proceeds to S14 (1) to (3).

In S14 (1), the basic energization end angle (basic value of the energization end angle) is set by referring to the map from the engine speed Ne and the required fuel injection amount Qf.
In S14 (2), the difference between the target fuel pressure and the actual fuel pressure is multiplied by a predetermined gain G to calculate a feedback amount (FB portion).

FB minute = (target fuel pressure-actual fuel pressure) x G
In S14 (3), the energization end angle is set from the basic energization end angle and the FB portion.
Energization end angle = basic energization end angle−FB portion When the energization start angle and the energization end angle are set, the energization of the solenoid 15 is controlled based on these.

  As is clear from the above description, according to the present embodiment, the energization start timing of the solenoid 15 provided in the suction side one-way valve 13 is set to the initial stage of the suction stroke, whereby the suction side one-way valve 13 is changed. By forcibly opening with electromagnetic force, the pressure loss for opening the suction side one-way valve 13 can be reduced, the boosting characteristic at the time of starting can be improved, and the occurrence of a barper can be dealt with in the pump chamber 12 as well. Become.

  In addition, according to the present embodiment, by setting the energization start timing of the solenoid 15 to the top dead center (TDC) of the plunger 11, the pressure loss can be reduced in the entire suction stroke without fear of disturbing the discharge operation. The effect of reducing pressure loss is obtained.

  In addition, according to the present embodiment, by switching the energization start timing of the solenoid 15 between the initial stage of the intake stroke (near TDC) and the latter stage of the intake stroke (near BDC) according to the operating conditions, pressure loss reduction and power consumption It is possible to achieve both reduction.

  Further, according to the present embodiment, the operating condition in which the energization start timing of the solenoid 15 is set to the initial stage of the intake stroke is at least when the fuel pressure on the discharge side is lower than a predetermined value (injection permission fuel pressure), so Thus, it is possible to increase the fuel pressure more quickly and to enable injection earlier.

  Further, according to the present embodiment, the operation condition in which the energization start timing of the solenoid 15 is the initial stage of the intake stroke is at least at the time of start by stratified combustion and when the fuel pressure on the discharge side is lower than a predetermined value (injection permission fuel pressure) By doing so, at the time of stratification start-up, the fuel pressure can be increased more quickly and can be started by injecting earlier.

  Further, according to the present embodiment, it is possible to cope with the generation of vapor by setting the operating condition in which the energization start timing of the solenoid 15 is the initial stage of the intake stroke at least when the fuel temperature is higher than a predetermined value (vapor generation temperature). In this way, the pressure drop can be reduced. Therefore, it is possible to suppress the decrease in the discharge amount when the vapor is generated, and to suppress the generation of the vapor itself.

  Further, according to the present embodiment, when the water temperature is used instead of the fuel temperature, the operating temperature is set to the first predetermined value (110 ° C.) at the time of starting the operation condition in which the energization start timing of the solenoid 15 is the initial stage of the suction stroke. When higher, during normal operation, the water temperature is higher than a second predetermined value (100 ° C.), and the second predetermined value (100 ° C.) is lower than the first predetermined value (110 ° C.). By setting, it is possible to accurately cope with the fact that the correlation between the water temperature and the fuel temperature differs between the start time and the normal operation time.

  Further, according to the present embodiment, the required injection amount is set to the maximum discharge of the high-pressure fuel pump by setting the operation condition in which the energization start timing of the solenoid 15 is the initial stage of the intake stroke at least at the time of low-temperature start starting by homogeneous combustion. When the low pressure fuel is discharged from the low pressure fuel pump as it is, the pressure loss at the time of suction by the high pressure fuel pump can be reduced and the startability can be improved.

The block diagram of the fuel supply apparatus of the internal combustion engine which shows one Embodiment of this invention Diagram showing the specific structure of the high-pressure fuel pump Time chart showing energization start timing of solenoid during normal control (A) and pressure loss reduction control (B) Flow chart of switching control between normal control and pressure loss reduction control Flow chart of control of energization start timing and energization end timing of solenoid

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Low pressure fuel tank 3 Fuel filter 4 Low pressure pressure regulator 5 Low pressure fuel passage 6 Fuel filter 7 Fuel damper 8 High pressure fuel pump 9 Plunger pump 10 Pump drive cam 11 Plunger 12 Pump chamber 13 Suction side one-way valve 13s Spring 14 Discharge Side one-way valve 14s Spring 15 Solenoid 16 High pressure fuel passage 17 Fuel accumulator 18 Branch pipe 19 Fuel injection valve 20 Fuel pressure sensor 21 Communication passage 22 Relief valve 23 Return passage 100 ECU

Claims (6)

The volume of the pump chamber is changed by the reciprocating movement of the plunger, the fuel is sucked into the pump chamber through the suction-side one-way valve in the plunger suction stroke, and the fuel in the pump chamber is discharged in one direction in the plunger discharge stroke. A plunger pump that discharges through a valve;
A solenoid provided for the suction side one-way valve, and capable of holding the suction side one-way valve in an open state regardless of the pressure in the pump chamber by electromagnetic force generated by energization;
With
Energizing the solenoid until an arbitrary timing of the discharge stroke of the plunger, holding the suction side one-way valve in an open state, closing the suction side one-way valve after energization to the solenoid, An in-cylinder direct injection type in which the discharge amount of the plunger pump is controlled by starting the discharge operation and controlling the closing timing of the suction side one-way valve by controlling the energization end timing of the solenoid In a fuel supply device for an internal combustion engine,
The energization start timing of the solenoid is switched between the initial suction stroke and the late suction stroke according to the operating conditions.
The fuel supply device for a direct injection type internal combustion engine, characterized in that the operating condition in which the energization start timing of the solenoid is at the beginning of the intake stroke is at least when the fuel pressure on the discharge side is lower than a predetermined value . The operating condition in which the energization start timing of the solenoid is set to the initial stage of the intake stroke is at least at the time of start-up by stratified combustion and when the fuel pressure on the discharge side is lower than a predetermined value . A fuel supply device for a direct injection type internal combustion engine. The in-cylinder direct injection internal combustion engine according to claim 1 or 2 , wherein the operating condition in which the energization start timing of the solenoid is set to the initial stage of the intake stroke is at least when the fuel temperature is higher than a predetermined value . Fuel supply device. When the cooling water temperature is used instead of the fuel temperature, the operation condition in which the energization start timing of the solenoid is at the beginning of the intake stroke is as follows: at the start, when the cooling water temperature is higher than the first predetermined value, 4. The direct injection internal combustion engine according to claim 3 , wherein the coolant temperature is higher than a second predetermined value, and the second predetermined value is lower than the first predetermined value . Fuel supply device. The in-cylinder according to any one of claims 1 to 4 , wherein the operation condition in which the energization start timing of the solenoid is at the initial stage of the intake stroke is at least a low-temperature start time that is started by homogeneous combustion . A fuel supply device for a direct injection internal combustion engine. The energization start timing of the solenoid when the suction stroke initial, according to energization start timing of the solenoid claim 1, characterized in that the top dead center of the plunger to any one of claims 5 A fuel supply device for a direct injection type internal combustion engine.

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