JPH0742641A - Fuel injection device - Google Patents

Abstract

PURPOSE:To aim at securing fuel injection even when battery voltage has dropped, with regard to a fuel injection valve that the higher the fuel pressure gets the higher the required battery voltage gets to open the valve, by making the fuel pressure drop when the battery voltage has dropped lower than the preset value. CONSTITUTION:A fuel injection valve 9 is connected to a low pressure pump 14 inside a fuel tank 13 through a fuel feeding pipe 12 after it is connected to a high pressure pump 11 through a fuel distribution pipe 10 to inject fuel into a combustion chamber 4 of an internal combustion engine 1. On the other hand, the fuel injection valve 9 is connected to a battery 57. The fuel injection valve 9 and the high pressure pump 11 are respectively controlled by an electronic control unit 50 based on respective detection signals from a voltage sensor 58 of the battery 57, a fuel pressure sensor 60 of the fuel distribution 10 and the like. Now, the higher the fuel pressure gets the higher the voltage of the battery 57 gets to open the valve of the fuel injection valve 9. In this case, the fuel pressure is lowered when the voltage of the battery 57 drops below the set voltage.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel injection device.

[0002]

2. Description of the Related Art A fuel injection device equipped with an electromagnetic fuel injection valve, which requires a high battery voltage in order to open the valve as the fuel pressure increases, has already been proposed by the present applicant (Japanese Patent Application No. Hei 4). -122235).

[0003]

However, when the battery voltage drops in the above fuel injection valve, the electric energy required to open the fuel injection valve is not supplied, and as a result, the fuel supplied to the fuel injection valve is not supplied. When the pressure of 1 is maintained constant, there is a problem that the fuel injection cannot be performed because the fuel injection valve is not opened.

[0004]

In order to solve the above problems, according to the present invention, an electromagnetic fuel injection valve that requires a high battery voltage to be opened as the fuel pressure increases is provided. In the fuel injection device, the pressure of the fuel supplied to the fuel injection valve is reduced when the battery voltage becomes lower than a predetermined set voltage.

[0005]

When the battery voltage becomes lower than the set voltage, the fuel pressure is lowered so that the fuel injection valve can be opened.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is a cylinder block,
Reference numeral 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an intake valve, 6 is an exhaust valve, 7 is an intake port, 8 is an exhaust port, and 9 is an electromagnetic fuel injection valve. The fuel injection valve 9 is connected to a high pressure pump 11 via a fuel distribution pipe 10, and the high pressure pump 11 is connected to a low pressure pump 14 arranged in a fuel tank 13 via a fuel supply pipe 12. In the embodiment shown in FIG. 1, the fuel injection valve 9 is composed of a so-called in-cylinder direct injection type fuel injection valve for injecting fuel into the combustion chamber 4, and therefore the pressure of the fuel supplied to the fuel injection valve 9 is Since it is necessary to make it higher than in the case of injecting fuel into the intake passage, in addition to the low pressure pump 14, the high pressure pump 11
Is provided. Further, a check valve 15 that can flow from the high-pressure pump 11 toward the fuel injection valve 9 is arranged in the fuel distribution pipe 10, while a pressure regulator 16 and a fuel filter 17 are arranged in the fuel supply pipe 12. . The pressure regulator 16 maintains the pressure of the fuel supplied to the high pressure pump 11 substantially constant.

FIG. 2 is a side sectional view of the fuel injection valve 9.
18 is a housing, 19 is a nozzle opening 20
, 21 is a needle, 22 is a needle 21
A movable core made of a magnetic material and integrally connected to
3 is a solenoid coil, 24 is a stator made of a magnetic material, 25 is a compression spring, and 26 is a fuel passage connected to the fuel distribution pipe 10. The fuel injection valve 9 is supplied with electric energy from the battery 57 (FIG. 1), and the fuel injection valve 9 is controlled based on the output signal of the electronic control unit 50 (FIG. 1).

When fuel injection should be started, the solenoid 23 is energized. When the solenoid 23 is energized, an upward electromagnetic attraction force acts on the movable core 22, and this upward force acts on the movable core 22 in a downward direction, that is, the spring force of the compression spring 25 and the fuel in the fuel passage 26. When the force due to the pressure becomes larger than the force, the movable core 22 ascends together with the needle 21, and as a result, the needle 21 opens the nozzle port 20 and fuel injection is started. On the other hand, when the fuel injection should be stopped, the solenoid 23 is deenergized. When the solenoid 23 is deenergized, the movable core 22 descends due to the spring force of the compression spring 25 and the force due to the fuel pressure in the fuel passage 26. As a result, the needle 21 closes the nozzle opening 20 and fuel injection is stopped. It

On the other hand, in the embodiment shown in FIG. 1, the high pressure pump 11 is composed of a diaphragm type pump. Referring to FIG. 3, where a cross-sectional view of the high pressure pump 11 is shown, 27
Is a housing, 28 is a cam chamber formed in the housing 27, 29 is a cam arranged in the cam chamber 28, 30 is a cam rotation shaft connected to a crankshaft (not shown), and 31 is a plunger insertion hole 32. A plunger 33 slidably inserted into the oil chamber, 33 an oil chamber communicated with the cam chamber 28 through the plunger insertion hole 31, and 34 a fuel distribution pipe 1
0 is a pump chamber, 35 is a diaphragm separating the oil chamber 33 and the pump chamber 34, 36 is a pump chamber 34
And 37, a fuel port connecting the fuel supply pipe 12 and 37, an opening / closing control valve arranged in the fuel port 36, a solenoid coil 38, a compression spring 39, and a stator 40 made of a magnetic material. A pair of ports 41 are formed in the housing 27, one end of each port 41 is opened to the circumferential surface of the plunger insertion hole 32, and the other end of each port 41 is opened to the cam chamber 28. The cam chamber 28 and each port 4
The inside of 1, the plunger insertion hole 32, and the oil chamber 33 are filled with the hydraulic oil of substantially atmospheric pressure. On the other hand, the fuel port 36 and the pump chamber 34 are filled with fuel.

Next, the operation of the high pressure pump 11 will be described. When the plunger 31 is located at the top dead center, the solenoid 38 is already de-energized, but an upward force is applied to the opening / closing control valve 37 by the fuel pressure in the pump chamber 34, and as a result, the opening / closing control valve 37. 37 is closed. Further, the diaphragm 35 is located above, that is, the pump chamber 34.
Is displaced towards. When the plunger 31 starts to descend from the top dead center of the plunger, the pressure inside the oil chamber 33 starts to decrease, and as a result, the diaphragm 35 starts to be displaced downward. When the diaphragm 35 starts to be displaced downward, the volume of the pump chamber 34 increases, so that the fuel pressure in the pump chamber 34 decreases. The upward force acting on the opening / closing control valve 37, that is, the force due to the fuel pressure in the pump chamber 34 is the opening / closing control valve 3
7, the opening / closing control valve 37 is displaced downward to open when the force is smaller than the downward force, that is, the spring force of the compression spring 39 and the force due to the fuel pressure in the fuel port 36. Fuel begins to flow into the pump chamber 34. Next, when the plunger 31 descends near the bottom dead center of the plunger, the pressure in the oil chamber 33 and the pump chamber 34
The pressure inside is almost equal and therefore the diaphragm 3
The displacement amount of 5 becomes almost zero. On the other hand, each opening of the port 41, which was closed by the peripheral surface of the plunger 31 near the top dead center of the plunger 31, on the side of the plunger insertion hole 32 is opened as the plunger 31 descends, and as a result, the plunger insertion hole 32 is opened through the port 41. And the cam chamber 28 communicate with each other. Next, each port 41 is fully opened just before the bottom dead center of the plunger 31.

When the plunger 31 rises from the bottom dead center and then the port 41 is closed by the peripheral surface of the plunger 31, the pressure in the oil chamber 33 starts to rise. When the pressure in the oil chamber 33 starts to rise, the diaphragm 35 is displaced upward, so that the volume of the pump chamber 34 starts to decrease. At this time, since the open / close control valve 37 is opened, the pump chamber 3
The fuel in 4 flows back into the fuel supply pipe 12 via the fuel port 36. Next, when the solenoid 38 is energized, the opening / closing control valve 37 is displaced upward and closed, and as a result, the fuel in the pump chamber 34 starts to be pressurized as the plunger 31 moves up. Next, when the fuel pressure in the pump chamber 34 reaches the valve opening pressure of the check valve 15 (FIG. 1), the check valve 15 opens and the fuel in the pump chamber 34 is discharged toward the fuel injection valve 9. . Note that once the opening / closing control valve 37 is closed, the opening / closing control valve 37
Since the closed state is maintained by the fuel pressure in the pump chamber 34, the solenoid 38 may be energized only for a short time required to raise the open / close control valve 37 to the closed position.

In the embodiment shown in FIG. 1, by controlling the fuel discharge amount of the high pressure pump 11, the fuel pressure in the fuel distribution pipe 10, that is, the fuel passage 26 of the fuel injection valve 9 (FIG. 2).
The fuel pressure inside is made to match the target fuel pressure,
Further, the fuel discharge amount of the high-pressure pump 11 is controlled by controlling the closing time of the opening / closing control valve 37. When the closing time of the opening / closing control valve 37 is lengthened, the opening time of the opening / closing control valve 37 is shortened, and as a result, the pump chamber 34 moves to the fuel port 3
Since the amount of fuel flowing back into the fuel supply pipe 12 via 6 is reduced, the fuel discharge amount of the high pressure pump 11 is increased. On the other hand, if the closing time of the opening / closing control valve 37 is shortened, the opening time of the opening / closing control valve 37 becomes longer, and as a result, the amount of fuel flowing back from the pump chamber 34 into the fuel supply pipe 12 increases, so that the high pressure pump 11 The fuel discharge rate is reduced. The solenoid 38 is controlled based on the output signal of the electronic control unit 50 (FIG. 1).

Referring to FIG. 4 showing the opening timing and closing timing of the opening / closing control valve 37, the solenoid 38 is turned on at the timing when the opening angle of the opening / closing control valve 37 goes back by the rotation angle TC of the cam 29. The opening / closing control valve 37 is closed. However, the opening timing of the opening / closing control valve 37 is shown in FIG.
As can be seen from the above, since it can be regarded as constant at the time when the cam rotation angle α advances from the top dead center of the plunger 31, in the embodiment according to the present invention, the cam rotation angle TC, that is, the closing timing of the opening / closing control valve 37 is controlled. Controls the closing time of the opening / closing control valve 37 and controls the fuel discharge amount of the high-pressure pump 11. That is, when the rotation angle TC is increased, the closing timing of the opening / closing control valve 37 is advanced and the closing time of the opening / closing control valve 37 is extended, so that the fuel discharge amount of the high-pressure pump 11 is increased, while when the rotation angle TC is decreased, the opening / closing control valve 37 is closed. Since the valve closing timing is delayed and the opening / closing control valve 37 closing time is shortened, the fuel discharge amount of the high pressure pump 11 is reduced. The valve closing timing TC is obtained as the sum of the basic valve closing timing TCB and the feedback correction coefficient Tf, which are obtained depending on the required fuel amount in the fuel injection valve 9 (described later). Further, the solenoid 38 is turned on for a short time according to the engine operating state.

Referring again to FIG. 1, the electronic control unit 5
0 is a digital computer, bidirectional bus 5
ROM (Read Only Memory) 52, RAM (Random Access Memory) 53, C mutually connected via 1
It has a PU (microprocessor) 54, an input port 55 and an output port 56. A voltage sensor 58 that generates an output voltage proportional to the battery voltage is attached to the battery 57 connected to the fuel injection valve 9.
Is output to the input port 55 via the AD converter 59. A fuel pressure sensor 60 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 10 is attached to the fuel distribution pipe 10, and the output voltage of the fuel pressure sensor 60 is input to an input port 55 via an AD converter 61. To be done. The load sensor 62 generates, for example, an output voltage proportional to the depression amount of an accelerator pedal (not shown), and this output voltage is input to the input port 55 via the AD converter 63. The crank angle sensor 64 generates an output pulse each time the crankshaft rotates 30 degrees, for example, and the output pulse is input to the input port 55. The top dead center sensor 65 generates an output pulse when, for example, the first cylinder reaches the intake top dead center, and this output pulse is input to the input port 55. C
The PU 54 calculates the current crank angle from the output pulse of the crank angle sensor 64 and the output pulse of the top dead center sensor 65, and also calculates the current cam 29 rotation angle. Further, the engine speed is calculated from the output pulse of the crank angle sensor 64. On the other hand, the output port 56 is connected to the solenoid 23 of the fuel injection valve 9 and the solenoid 38 of the high-pressure pump 11 via the corresponding drive circuit 66.

When the solenoid 23 of the fuel injection valve 9 is turned on to start fuel injection, an upward electromagnetic attraction force acts on the movable core 22, and this upward force acts on the movable core 22 in the downward direction. That is, when it becomes larger than the spring force of the compression spring 25 and the force due to the fuel pressure in the fuel passage 26, the movable core 22 rises together with the needle 21, so that fuel injection is started. However, the solenoid 23
When the voltage of the battery 57 that supplies electric energy to the vehicle decreases, the electromagnetic attraction force acting on the movable core 22 decreases, and as a result, when the fuel pressure in the fuel passage 26 (FIG. 2) is kept constant, An upward force acting on the movable core 22, that is, an electromagnetic attraction force by the solenoid 23, a downward force acting on the movable core 22, that is, the compression spring 25.
The spring force and the force due to the fuel pressure in the fuel passage 26 cannot be overcome, so that the movable core 22 cannot rise and fuel injection cannot be performed. In order to solve this problem, it is conceivable to increase the number of turns of the solenoid 23, for example, to secure the electromagnetic attraction force, but in this case, the size of the fuel injection valve 9 becomes large. Alternatively, for example, it is conceivable to discharge the electric energy stored in the capacitor in advance when the fuel injection valve 9 is opened, but in this case, the structure becomes complicated and the cost increases. Therefore, in the embodiment according to the present invention, the battery 5
When the voltage of No. 7 becomes lower than a predetermined set voltage, the fuel pressure in the fuel passage 26 is reduced. As a result, the movable core 22 can move up even when the voltage of the battery 57 decreases and the upward force acting on the movable core 22 when fuel injection should be started, and therefore the fuel injection can be continued. You can Moreover, the fuel injection can be ensured without increasing the size of the fuel injection valve 9 and without increasing the cost.

FIG. 5 shows the target fuel pressure PF in the fuel distribution pipe 10 and the voltage V of the battery 57 in the embodiment according to the present invention.
The relationship with B is shown. The map shown in FIG. 5 is RO
It is stored in M52. Referring to FIG. 5, when the voltage VB of the battery 57 is higher than the set voltage VB0, the target fuel pressure PF in the fuel distribution pipe 10 is maintained at a constant value PF0. On the other hand, when the voltage VB of the battery 57 becomes lower than the set voltage VB0, the target fuel pressure PF in the fuel distribution pipe 10 is set lower than the constant value PF0. As described above, in the embodiment of the present invention, the fuel discharge amount of the high-pressure pump 11 is controlled so that the fuel pressure Pf in the fuel distribution pipe 10 matches the target fuel pressure PF.
By setting F to be lower than the constant value PF0, the fuel pressure Pf in the fuel distribution pipe 10 can be reduced.

Next, a routine for executing the above embodiment will be described with reference to FIG. Referring to FIG. 6, first, at step 70, the voltage VB of the battery 57 is obtained based on the output voltage of the voltage sensor 58. Next, at step 71, the battery 57 obtained at step 70
The target fuel pressure PF in the fuel distribution pipe 10 is calculated from the voltage VB based on the map shown in FIG. In step 72, the engine speed N and the engine load L that have already been calculated are obtained.
From the above, the required fuel amount QF to be injected from the fuel injection valve 9 is calculated based on the map shown in FIG. 7, and at step 73, the required fuel amount QF obtained at step 72 is opened and closed based on the map shown in FIG. The cam rotation angle TCB (FIG. 4) corresponding to the basic valve closing timing of the control valve 37 is obtained. As can be seen from FIG. 8, the cam rotation angle TCB is increased as the required fuel amount QF increases. Then step 7
4, the current fuel pressure Pf in the fuel distribution pipe 10 is calculated based on the output voltage of the fuel pressure sensor 60, and step 75
Then, based on the target fuel pressure PF and the current fuel pressure Pf in the fuel distribution pipe 10, etc., the fuel pressure Pf in the fuel distribution pipe 10 is determined.
A feedback correction coefficient Tf that makes the fuel pressure equal to the target fuel pressure PF is obtained. At step 76, the cam rotation angle TC corresponding to the closing timing of the opening / closing control valve 37 is obtained by adding the feedback correction coefficient Tf to the cam rotation angle TCB obtained at step 73. Then, the processing cycle is ended. The maps shown in FIGS. 7 and 8 are stored in the ROM 52 in advance.

In the embodiment according to the present invention, the basic fuel injection time T in the fuel injection valve 9 is calculated from the required fuel amount QF. This basic fuel injection time T and required fuel amount QF
The relationship with is stored in the ROM5 in advance in the form of a map as shown in FIG.
It is stored in 2. As can be seen from FIG. 9, the basic fuel injection time T is increased as the required fuel amount QF increases. The basic fuel injection time T shown in FIG.
This is the optimum fuel injection time for injecting the required fuel amount QF when the target fuel pressure PF therein is the constant value PF0 (FIG. 5). However, when the target fuel pressure PF in the fuel distribution pipe 10 is made lower than a constant value PF0 based on the map of FIG. 5, if fuel injection is performed from the fuel injection valve 9 for the basic fuel injection time T, injection from the fuel injection valve 9 is performed. The amount of fuel to be discharged becomes smaller than the required fuel amount QF. Therefore, in the embodiment according to the present invention, the fuel injection time TA is calculated by multiplying the basic fuel injection time T by the correction coefficient K defined by the following equation.
U is determined so that the fuel injection amount at the target fuel pressure PF matches the required fuel amount QF. K = (PF0 / PF) ^1/2

FIG. 10 shows a routine for calculating the fuel injection time. Referring to FIG. 10, first, at step 80, the basic fuel injection time T is calculated based on the map of FIG.
Is calculated. Next, at step 81, the correction coefficient K is calculated from the already-obtained target fuel pressure PF. Next, at step 82, the correction coefficient K is set to the basic fuel injection time T
The fuel injection time TAU is calculated by multiplying by.

In the above-mentioned embodiments, the high pressure pump 11 is composed of a diaphragm type pump.
However, the high-pressure pump 11 can also be constituted by, for example, a positive displacement pump whose fuel discharge amount can be controlled.

[0021]

EFFECTS OF THE INVENTION Fuel injection can be secured even when the battery voltage drops.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine to which an embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of a fuel injection valve.

FIG. 3 is an enlarged cross-sectional view of a high pressure pump.

FIG. 4 is a diagram showing a valve opening timing and a valve closing timing of an opening / closing control valve of a high-pressure pump.

FIG. 5 is a diagram showing a relationship between a target fuel pressure PF and a battery voltage VB.

FIG. 6 is a flowchart for calculating the closing timing of the opening / closing control valve of the high pressure pump.

FIG. 7 is a diagram showing a relationship among a required fuel amount, an engine speed and an engine load.

FIG. 8 is a diagram showing a relationship between a required fuel amount and a basic valve closing timing.

FIG. 9 is a diagram showing a relationship between a required fuel amount and a basic fuel injection time.

FIG. 10 is a flowchart for calculating a fuel injection time.

[Explanation of symbols]

 4 ... Combustion chamber 9 ... Fuel injection valve 10 ... Fuel distribution pipe 11 ... High-pressure pump 14 ... Low-pressure pump 57 ... Battery 58 ... Voltage sensor 60 ... Fuel pressure sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F02M 51/00 F 9248-3G

Claims (1)

[Claims] 1. In a fuel injection device equipped with an electromagnetic fuel injection valve, which requires a high battery voltage in order to open as the fuel pressure increases, the battery voltage is lower than a predetermined set voltage. The fuel injection device is configured to reduce the pressure of the fuel supplied to the fuel injection valve when it becomes low.