JP2000136763A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smooth fuel pressure control on the side of an injection valve for more reliability by providing a solenoid relief valve. SOLUTION: Fuel in a fuel tank 1 is increased in pressure by a low pressure pump 2 and a high pressure pump 8 and injected from an injection valve 37 to an engine. In the discharge stroke of the high pressure pump 8, a fuel pressure control valve 19 is made temporarily open for escaping fuel in a cylinder 10 from a relief oil passage 17 for the pump to control fuel pressure in response to the operated condition of the engine. During starting or reducing the speed of engine, solenoid relief valve 25 is made temporarily open. In this way, fuel in a common rail 35 is relieved from a relief oil passage 18 for the injection valve, if required, for improving the starting and operability of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device suitable for use in injecting fuel contained in a fuel tank of an automobile or the like from an injection valve to each cylinder of an engine, and more particularly to a fuel injection control device for an injection valve. The present invention relates to a fuel injection control device configured to variably control a fuel pressure.

[0002]

2. Description of the Related Art In general, a fuel injection control device for an automobile engine or the like is provided with a common rail provided with a plurality of injection valves for injecting fuel into a cylinder of an internal combustion engine, and connected to the common rail. It consists of a fuel pump that sucks fuel into the cylinder and discharges the fuel in the cylinder toward the common rail during the discharge stroke, and a fuel pressure control valve that controls the amount of fuel discharged from the fuel pump toward the common rail. Some are known (for example, JP-A-62-258160, JP-A-2-146256, etc.).

In this type of conventional fuel injection control device, the fuel pressure control valve is constituted by a normally open solenoid valve or the like.
The fuel pressure control valve is driven to a valve closing side by being energized from an engine control control unit or the like, and is kept open when the energization from the control unit is stopped.

[0004] The control unit adjusts the amount of fuel supplied to the common rail by changing the timing of opening and closing the fuel pressure control valve, and adjusts the amount of fuel injected from the injector to each cylinder of the engine. The pressure is variably controlled according to the operating state of the engine.

[0005]

In the above-mentioned prior art, the fuel pressure in the common rail is changed by using a fuel pressure control valve, so that the pressure of the fuel injected from the injector into each cylinder of the engine is reduced. It is configured to be variably controlled according to the operating state and the like.

However, since the fuel pressure control valve merely controls the amount of fuel discharged from the fuel pump toward the common rail, for example, when the engine is started, when the engine is decelerated, etc. There is a problem that it is difficult to improve startability and drivability.

That is, when the engine is started in a high temperature state, for example, the heat of the previous operation of the engine is transmitted to the common rail in the engine room, and the fuel pressure in the common rail rises excessively due to the heat, or the fuel pressure in the common rail increases. Fuel vapor or the like may occur, but in this case, it is difficult to properly control the fuel pressure in the fuel pressure control valve that only controls the fuel discharge amount, particularly in the depressurizing direction. At times, the fuel injection amount may be unstable.

Further, for example, when the driver of the vehicle releases the accelerator operation and the engine is decelerated from the high rotation speed side, the fuel injection from the injector may be temporarily stopped. Also in this case, it is difficult to quickly reduce the fuel pressure in the common rail by using the fuel pressure control valve, so that the operability of the engine may be adversely affected.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to stably control the pressure of fuel supplied from a fuel pump to an injection valve. Accordingly, it is an object of the present invention to provide a fuel injection control device capable of surely reducing the pressure in accordance therewith and improving the startability and operability of the internal combustion engine.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is an injection valve for injecting fuel into a cylinder of an internal combustion engine, and a fuel pump for discharging sucked fuel to the injection valve side. A relief oil passage provided between the discharge side of the fuel pump and the injection valve and communicating with the suction side of the fuel pump; and a relief oil passage provided in the relief oil passage so as to be openable and closable. And a normally-closed electromagnetic relief valve that opens when the pressure of the fuel pump is reduced and releases the fuel on the injection valve side to the suction side of the fuel pump.

With this configuration, the fuel supplied from the fuel pump to the injector is relieved to the suction side of the fuel pump using an electromagnetic relief valve, and the pressure of the fuel supplied to the injector is reduced. be able to. As a result, the pressure of the injected fuel can be variably controlled by, for example, an electromagnetic relief valve.

On the other hand, the invention of claim 2 has an injection valve for injecting fuel into a cylinder of an internal combustion engine, and a piston reciprocating in the cylinder. The piston moves from the suction valve to the cylinder while the piston reciprocates in the cylinder. A fuel pump for discharging the fuel sucked into the fuel injector to the injection valve side via a discharge valve; and a fuel pump connected between an inflow side and an outflow side of the suction valve with the suction valve interposed therebetween. A relief oil passage for the pump, a relief oil passage for the injection valve, which is provided between the discharge valve and the injection valve of the fuel pump and communicates with an inflow side of the suction valve, and which opens to the relief oil passage for the pump. A normally-closed fuel pressure control valve that is provided so as to be able to be closed and that is opened during a period from the middle to the end of the discharge stroke of the fuel pump, and is provided so as to be able to be opened and closed in the relief oil passage for the injection valve; Open when reducing the pressure on the outlet side of the discharge valve. Adopts a configuration comprising a normally closed solenoid type relief valve for relief was fuel on the outflow side of the discharge valve to the inlet side of the suction valve.

[0013] Thus, during the period from the opening of the fuel pressure control valve during the discharge stroke to the end of the discharge stroke, the fuel in the fuel pump is supplied to the inlet side of the suction valve via the relief oil passage for the pump. The pressure of the fuel discharged from the fuel pump can be variably controlled by changing the opening timing of the fuel pressure control valve. Further, the fuel on the outflow side of the discharge valve can be relieved to the inflow side of the suction valve using an electromagnetic relief valve, and the pressure of the fuel supplied to the injection valve can be reduced.

According to a third aspect of the present invention, the internal combustion engine is provided with temperature detecting means for detecting a temperature corresponding to a temperature of fuel injected from the injection valve, and is supplied to the injection valve. Fuel pressure detection means for detecting the pressure of the fuel is provided, and when the internal combustion engine is started in a state where the temperature detected by the temperature detection means is equal to or higher than a predetermined temperature, the electromagnetic relief valve is operated by the fuel pressure detection means. The apparatus is provided with valve control means for opening the valve only for a predetermined time in accordance with the detected fuel pressure.

Thus, when the internal combustion engine is started, the temperature of the fuel (fuel temperature) can be detected using the detection result by the temperature detecting means, and the pressure of the fuel can be detected by the fuel pressure detecting means. As a result, the electromagnetic relief valve can be opened and closed by the valve control means in accordance with the detected values of the fuel temperature and the fuel pressure. Even when the internal combustion engine is started in a high temperature state, the fuel pressure is controlled in accordance with the fuel temperature. Can be properly controlled.

Further, in the invention according to claim 4, the internal combustion engine is provided with injection control means for temporarily stopping fuel injection from the injection valve when the internal combustion engine is in a deceleration state,
When fuel injection from the injection valve is stopped by the injection control means, a valve control means is provided for opening the electromagnetic relief valve for a fixed time according to the fuel pressure on the injection valve side.

Thus, even when the fuel injection is temporarily stopped using the injection control means, the pressure of the fuel supplied to the injection valve is reduced by opening the electromagnetic relief valve using the valve control means. When the fuel injection is restarted, the fuel pressure corresponding to the operating state of the internal combustion engine can be maintained.

Further, in the invention of claim 5, the electromagnetic relief valve is configured to be opened at least for a certain time when the internal combustion engine is started.

Thus, when the internal combustion engine is started, for example, even when the fuel pump is not sufficiently driven, by opening the electromagnetic relief valve, the fuel is directly supplied to the injection valve bypassing the fuel pump. be able to.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fuel injection control device according to an embodiment of the present invention will be described in detail with reference to FIGS. .

Reference numeral 1 denotes a fuel tank containing fuel to be injected from a later-described injection valve 37 into each cylinder (not shown) of the engine, and 2 denotes a fuel in the fuel tank 1 at, for example, 0.3 to 0.
A low-pressure pump for discharging into the low-pressure pipe 3 at a low pressure of about 4 MPa is provided. Filters 4 and 5 for purifying fuel are provided in the fuel tank 1 before and after the low-pressure pump 2.
A return pipe 6 between the low-pressure pipe 3 and the fuel tank 1;
A pressure regulator 7 is provided.

The pressure regulator 7 returns the excess fuel in the low-pressure pipe 3 from the return pipe 6 to the fuel tank 1 and reduces the fuel pressure in the low-pressure pipe 3 to, for example, about 0.3 to 0.4 MPa. It is configured to keep it at a constant value.

A high-pressure pump 8 is a reciprocating fuel pump driven by an engine.
As shown in FIGS. 1 and 2, a cylinder 10 provided in a casing 9, a piston 11 provided reciprocally in the cylinder 10, and, for example, four cam peaks 12 </ b> A,
, And cams 12 for reciprocating the piston 11 in the cylinder 10 by the cam ridges 12.
And a suction oil passage 13, a suction valve 14, a discharge oil passage 15,
It is composed of a discharge valve 16 and the like.

Here, when the cam 12 is driven to rotate by a crankshaft or a camshaft (neither is shown) of the engine, the piston 11 follows the cam peak 12A, for example, at a cam angle of 90 °. Reciprocate in the cylinder 10. When the fuel in the fuel tank 1 is discharged from the low-pressure pump 2 into the low-pressure pipe 3, the high-pressure pump 8 sends the low-pressure fuel into the cylinder 10 through the suction oil passage 13 and the suction valve 14 in the suction stroke. In the suction and discharge strokes, the pressure in the cylinder 10 is increased while the discharge oil passage 15 and the discharge valve 16 are increased.
Through the injection valve 37, for example, 5 to 16 MPa
The high pressure fuel is supplied to the injection valve 37 side.

In this case, as shown in FIG. 6, the rotation angle during which the cam 12 rotates from the position corresponding to the top dead center of the piston 11 by about 90 ° and reaches the position corresponding to the top dead center again. If (cam angle) is defined as full stroke S0,
The suction stroke is performed during the first 45 ° of the entire stroke S0, and the discharge stroke is performed during the second 45 °.

Reference numeral 13 denotes a suction oil passage provided in the casing 9, and the suction oil passage 13 is, as shown in FIGS.
The low pressure pipe 3 and the cylinder 10 are connected. In the middle of the suction oil passage 13, there is provided a suction valve 14 that opens during the suction stroke of the high-pressure pump 8 and closes during the discharge stroke.

Reference numeral 15 denotes a discharge oil passage provided in the casing 9. The discharge oil passage 15 connects between the cylinder 10 and a high-pressure pipe 36 described later. In the middle of the discharge oil passage 15, a discharge valve 16 is provided which closes during the suction stroke of the high-pressure pump 8 and opens during the discharge stroke.

Reference numeral 17 denotes a pump relief oil passage provided in the casing 9. The pump relief oil passage 17 connects between the inflow side and the outflow side of the suction valve 14. The pump relief oil passage 17 relieves the pressure in the high-pressure pump 8 to the inflow side of the suction valve 14.

Reference numeral 18 denotes a relief oil passage for an injection valve serving as a relief oil passage provided in the casing 9. The relief oil passage 18 for the injection valve includes a cylinder 10, a suction valve 14, a discharge valve 16 and the like of the high-pressure pump 8. Is connected between the suction oil passage 13 and the discharge oil passage 15, and is arranged in parallel with the high-pressure pump 8. The injection valve relief oil passage 18 is connected to the injection valve 3.
The pressure supplied to the suction valve 7 is relieved on the inflow side of the suction valve 14.

Numeral 19 denotes a fuel pressure control valve which can be opened and closed in the middle of the relief oil passage 17 for the pump.
2, a casing 9 constituting a valve casing, a valve body 21 formed of a magnetic material such as an iron material and housed in a valve chamber 20 provided in the casing 9, and a valve body 21 as shown in FIG. And the casing 9 and the valve body 21
The valve spring 22 biases the valve body 22 in a valve closing direction with a predetermined biasing force, a solenoid 23 that drives the valve body 22 in the valve opening direction, and the like, and is configured as a normally closed solenoid valve. .

Here, the solenoid 23 is connected to a control unit 38 described later using the signal line 24. Then, when the power supply to the solenoid 23 is stopped and the pressure in the cylinder 10 is smaller than the maximum pressure described later, the valve body 21 is kept closed by the valve spring 22. When the drive signal K1 is output from the control unit 38 to the solenoid 23, the valve element 21 is magnetically attracted to the solenoid 23 and opens against the valve spring 22.

Then, the fuel pressure control valve 19 outputs the drive signal K1.
The valve is opened only during the middle of the discharge stroke of the high-pressure pump 8 until the end thereof, and at this time, the fuel in the cylinder 10 is relieved to the inflow side of the suction valve 14 through the relief oil passage 17 for the pump. Pressure in the common rail 35 (pressure of fuel injected from the injection valve 37)
Is variably controlled.

Reference numeral 25 denotes an electromagnetic relief valve which is provided in the middle of the injection valve relief oil passage 18 so as to be opened and closed. The electromagnetic relief valve 25 is a valve of the casing 9 substantially similar to the fuel pressure control valve 19. A normally closed solenoid valve is constituted by the chamber 26, the valve body 27, the valve spring 28, the solenoid 29, and the like.
Is connected to

When the power supply to the solenoid 29 is stopped and the fuel pressure in the common rail 35 is lower than a predetermined relief pressure, the valve body 27 is closed by the valve spring 28. Hold the valve state. In this case, the relief pressure of the electromagnetic relief valve 25 is
For example, it is set substantially equal to the maximum pressure described later.

When the fuel pressure in the common rail 35 exceeds the relief pressure, the valve body 27 is pushed against the valve spring 28 by this pressure, and the valve body 27 opens. As a result, the fuel in the common rail 35 is relieved toward the low-pressure pipe 3 through the relief oil passage 18 for the injection valve.

Further, when the control unit 38 outputs a drive signal K 2 to the solenoid 29, the valve body 27 is opened by the solenoid 29 against the valve spring 28. When the engine is started, or when the engine is in a fuel cut state, when the control unit 38 performs a start-up fuel pressure control and a fuel cut-off fuel pressure control described later, the electromagnetic relief valve 25 is opened as required. The fuel in the common rail 35 is relieved to the inflow side of the suction valve 14 through the relief oil passage 18 for the injection valve.

Reference numeral 31 denotes a bypass passage provided between the suction oil passage 13 and the discharge oil passage 15, and the bypass passage 31 is provided with a check valve 32 as shown in FIG.
Then, for example, when starting the engine, the common rail 35
When the internal fuel pressure is low, the fuel on the low pressure pipe 3 side is supplied into the common rail 35 from the bypass passage 31 together with the high pressure pump 8 and the injection valve relief oil passage 18.

Reference numeral 33 denotes a relief passage connected in parallel with the bypass passage 31. A relief valve 34 is provided in the relief passage 33, and the relief valve 34 has a pressure value larger than the relief pressure of the electromagnetic relief valve 25. Has a predetermined relief pressure. When the fuel pressure in the common rail 35 greatly exceeds the maximum pressure described later, the relief valve 34 is opened, and the fuel in the common rail 35 is sucked not only from the relief oil passage 18 for the injection valve but also from the relief passage 33. It is configured to be relieved on the inflow side of the valve 14.

A common rail 35 has one end connected to the discharge oil passage 15 of the high-pressure pump 8 through a high-pressure pipe 36.
The common rail 35 is formed by a metal tube or the like whose other end is closed, and four injection valves 37, 37,... Corresponding to each cylinder of the engine are provided in the middle thereof.

Reference numeral 38 denotes a control unit as an injection control means attached to the engine. On the input side of the control unit 38, as shown in FIG. 1, a crank angle sensor 39 for detecting the amount of rotation of the crankshaft of the engine is provided. ,
A cam position sensor 40 for detecting the rotational position of the cam shaft, a fuel pressure sensor 41 for detecting the fuel pressure in the common rail 35, and a fuel temperature sensor 42 for detecting the fuel temperature in the common rail 35 Etc. are connected. The fuel pressure control valve 19 and the electromagnetic relief valve 25 are connected to the output side of the control unit 38 together with the low-pressure pump 2 and each injection valve 37.

Further, the control unit 38 has a RO
M, a storage unit 38A including a RAM, and the like.
8A stores a fuel injection control program shown in FIGS. 3 to 5 and fuel pressure setting data for variably setting the target fuel pressure P0 in the common rail 35.

In this case, the target fuel pressure P0 is, for example, 4 to 6
Normal pressure of about MPa, intermediate pressure of about 6 to 8 MPa,
The maximum pressure is set to any one of the maximum pressures of about 10 to 15 MPa according to the load of the engine, the number of revolutions, and the like.

The control unit 38 outputs a drive signal K 1 to the fuel pressure control valve 19 to change a later-described reference stroke S 1 in accordance with the operating state of the engine and the like.
To variably control the fuel pressure inside. The control unit 38 controls the fuel pressure in the common rail 35 by using the electromagnetic relief valve 25 when the engine is started or when the fuel is cut by outputting a drive signal K2 to the electromagnetic relief valve 25.

The fuel injection control device according to the present embodiment has the above-described configuration. Next, a fuel injection control process of the control unit 38 will be described with reference to FIGS.

First, when power is supplied to the control unit 38, it is determined in step 1 whether or not the engine is being started. For example, since the engine is in a stopped state, "YES" is determined in step 1. In some cases, after starting fuel pressure control described later is performed in step 2,
Return to start with 0.

When it is determined "NO" in step 1, the engine is in operation, so in step 3, the fuel injection amount of the injection valve 37 is calculated in accordance with the operating state of the engine and the like. Correspondingly, the fuel injection pulse width T
Calculate i.

Next, in step 4, it is determined whether or not the engine is in a state where fuel cut control should be performed.
If it is determined to be "O", the injection pulse width Ti is output to the injection valve 37 in step 5 in order to perform the normal fuel injection, and the fuel is supplied from the injection valve 37 to the engine for the time (the injection amount) corresponding to the injection pulse width Ti. To each cylinder.

Here, the fuel cut control means that when the engine is decelerated from the high rotation side, for example, when the driver of the vehicle releases the operation of the accelerator pedal.
The fuel injection from the injection valve 37 to each cylinder of the engine is temporarily stopped to improve fuel efficiency, purify exhaust gas, and the like.

If "YES" is determined in step 4, the engine is in an operating state in which fuel cut control is to be performed due to deceleration of the vehicle or the like. After performing the fuel cut control in step 7, fuel pressure control during fuel cut described later is performed in step 7.

Next, in step 8, the target fuel pressure P0 in the common rail 35 is variably set according to the engine load, the number of revolutions, and the like by using the fuel pressure setting data and the like in the storage section 38A. A reference stroke S1 corresponding to the fuel pressure is calculated. Here, this reference stroke S1
Is defined as the rotation angle from the start of the discharge stroke to the opening of the fuel pressure control valve 19, as shown in FIG. 6, for example.

Next, at step 9, the cam angle of the engine is detected using the detection signals output from the crank angle sensor 39, the cam position sensor 40, and the like, so that the cam angle excluding the reference stroke S1 is obtained. The driving signal K1 is output to the fuel pressure control valve 19 within the range, and the fuel pressure control valve 19 is opened from the middle to the end of the discharge stroke. In this case, during the operation of the engine, the high-pressure pump 8 repeats the full stroke S0 in FIG. 4 four times while the cam 12 makes one rotation, so that the drive signal K1 is applied to these full strokes S0. Each is output.

As a result, while the fuel pressure control valve 19 is open,
The fuel in the cylinder 10 is relieved toward the low-pressure pipe 3 through the relief oil passage 17 for the pump, and the substantial discharge stroke of the high-pressure pump 8 is only in the range of the hatched portion A shown in FIG. Is set large, the discharge amount of the high-pressure pump 8 increases with the area of the hatched portion A, and the fuel pressure in the common rail 35 increases.

When the reference stroke S1 is set small, the discharge amount of the high-pressure pump 8 decreases and the fuel pressure in the common rail 35 decreases. Therefore, the control unit 38 changes the size of the reference stroke S1 by changing the size of the reference stroke S1. The fuel pressure in the common rail 35 can be variably controlled.

On the other hand, if "YES" is determined in step 1, since the engine is being started, the starting fuel pressure control shown in FIG. 4 is performed.

That is, in step 11 in FIG. 4, the detection signal output from the fuel temperature sensor 42 is read, and
2, the common rail 3 calculated using the detection signal
5 is, for example, 45 to 60 ° C., preferably 50 to 60 ° C.
It is determined whether or not the temperature is equal to or higher than a predetermined determination value as a high temperature of about ° C.

If it is determined "NO" in step 12, it is not the case where the engine is started in a high temperature state. Therefore, in step 13, the target fuel pressure P0 in the common rail 35 is set to, for example, 0.2 to 0.4 MPa, preferably 0.
A predetermined pressure is set as a low pressure value of about 3 MPa.

Subsequently, at step 14, a drive signal K2 is output to the electromagnetic relief valve 25, and the electromagnetic relief valve 2
After opening the valve 5 for a certain time, for example, step 1
At 5, the process returns to step 9 in FIG. In this case, after detecting the start of the engine, the drive signal K2 is stopped and the electromagnetic relief valve 25 is closed.

As a result, when the engine is started, the relief oil passage 18 for the injection valve acts almost in the same way as the bypass passage 31, and even when the high-pressure pump 8 is not sufficiently driven for starting the engine, The fuel discharged from the low-pressure pump 2 can be smoothly supplied into the common rail 35 through the relief oil passage 18 for the injection valve and the bypass passage 31, and the fuel pressure in the common rail 35 can be increased at an early stage.

If "YES" is determined in step 12, the engine is to be started in a high temperature state. Therefore, in order to suppress the fuel vapor generated in the common rail 35, the common rail 35 is determined in step 16. The target fuel pressure P0 is, for example, 0.6 to 0.8 MPa,
Preferably, the pressure is set to a predetermined value as a pressure value of about 0.7 MPa.

Next, at step 17, the fuel pressure sensor 41
Is output from the fuel pressure P in the common rail 35
In step 18, it is determined whether the fuel pressure P is equal to or higher than the set value (0.3 MPa).

When the determination in step 18 is "YES", the fuel pressure P in the common rail 35 becomes 0.3M
Since it is larger than Pa, the flow returns to step 17 after the electromagnetic relief valve 25 is opened in step 19. As a result, during a certain time during which the fuel pressure P in the common rail 35 is 0.3 MPa or more, the processing of steps 17 to 19 is repeatedly performed, and the fuel pressure P decreases.

If the determination in step 18 is "NO", the fuel pressure P in the common rail 35 becomes 0.3 MPa.
Since the driving signal K2 is stopped in step 20, the electromagnetic relief valve 25 is closed, and the process returns to step 9 in step 21.

Thus, when the engine is started in a high temperature state, the fuel pressure P in the common rail 35 can be adjusted to an appropriate set value (0.3 MPa) by using the electromagnetic relief valve 25, and the vapor and the like in the common rail 35. Can be suppressed, and the injection valve 3 can be used even when the engine is started at a high temperature.
7 can stably inject fuel.

On the other hand, if "YES" is determined in step 4, the fuel cut control is performed in step 6, so that the fuel pressure in the common rail 35 does not decrease due to the fuel injection from the injection valve 37, and the common rail 3
It becomes difficult to lower the fuel pressure in the fuel tank 5. Therefore, in step 7, fuel pressure control during fuel cut is performed.

That is, in the fuel pressure control at the time of fuel cut, as shown in FIG. 5, first, at step 21, the engine speed N is, for example, 1400-1800 rpm, preferably 1600 rpm.
It is determined whether or not the rotation speed is approximately equal to or greater than a predetermined determination value as a rotation speed of about rpm, and when it is determined to be “YES”,
The process moves to step 27 described later.

If "NO" is determined in the step 21, the injection pulse width T when the injection is restarted in the step 22.
It is determined whether or not i is equal to or greater than a predetermined determination value as a pulse width of, for example, 3 to 5 ms, and preferably about 4 ms. If “YES” is determined, the process proceeds to step 27, and if “NO” is determined. Move to step 23.
That is, since the engine is in a low-load operation state, the engine speed N is less than 1600 rpm and the injection pulse width T
If i is less than 4 ms, proceed to step 23,
In other cases, the engine is in the middle to high load operating state, and the process proceeds to step S27.

In step 23, it is determined whether or not the target fuel pressure P0 in the common rail 35 is equal to or less than a predetermined determination value, for example, a pressure value of 6 to 8 MPa, preferably about 7 MPa. In this case, when it is determined "NO" in step 23, the target fuel pressure P0 is set to be larger than the engine load state (low load), and the actual fuel pressure follows the target fuel pressure P0 and is maintained at a high pressure. It can be determined that there is.

Next, at step 24, the electromagnetic relief valve 25 is opened, the fuel pressure in the common rail 35 is released from the relief oil passage 18 for the injection valve to the low-pressure pipe 3 side to decrease, and the target fuel pressure P0 is reduced to 7 MPa. During a certain period of time until the time becomes the following, the process returns to step 23 and this process is repeated.

On the other hand, if "YES" is determined in the step 23, since the target fuel pressure P0 is equal to or less than the determination value P3, it is determined that the target fuel pressure P0 substantially corresponds to the load state of the engine. After closing the relief valve 25, the process returns to step 8 in FIG.

In step 27, the engine is set
Because of the high load operation state, the target fuel pressure P0 in the common rail 35 is, for example, 11 to 13 MPa, preferably 12 to 13 MPa.
It is determined whether the pressure value is equal to or less than a predetermined determination value as a high pressure value of about MPa.

If "NO" is determined in the step 27, the target fuel pressure P0 is set to an excessively large value. Therefore, in a step 28, the electromagnetic relief valve 25 is opened to lower the fuel pressure in the common rail 35. At the same time, step 2 is performed until the target fuel pressure P0 becomes 12 MPa or less.
7, the process is repeated.

If "YES" is determined in the step 27, the target fuel pressure P0 substantially corresponds to the load state of the engine, so that in the step 25, the electromagnetic relief valve 2
5 is closed, and the routine returns to step 26.

Thus, even when the fuel injection from the injection valve 37 is stopped, the relief oil passage 18 for the injection valve,
The fuel pressure in the common rail 35 can be smoothly reduced according to the operation state of the engine by the electromagnetic relief valve 25 and the like, and the fuel injected from the injection valve 37 is also used when fuel injection is restarted from the fuel cut state. Pressure can be controlled stably.

Thus, in the present embodiment, the casing 9 of the high-pressure pump 8 is provided with the pump relief oil passage 17, the injection valve relief oil passage 18, the fuel pressure control valve 19, the electromagnetic relief valve 25, and the like. The fuel pressure control valve 19 can be opened from the middle to the end of the discharge stroke, and at this time, the fuel in the cylinder 10 is released from the pump relief oil passage 17.
And the pressure of the fuel injected from the injection valve 37 can be appropriately controlled by the fuel pressure control valve 19, the electromagnetic relief valve 25, and the like according to the operating state of the engine.

Further, since the relief oil passage 18 for the injection valve, the electromagnetic relief valve 25 and the like are provided, the fuel pressure in the common rail 35 is reduced by the electromagnetic relief valve 25 and the like even when the engine is started or when the fuel is cut off. The pressure can be reduced as needed, and the pressure of the injected fuel can be constantly maintained in a stable state.

That is, when the engine is started in a high temperature state, the fuel pressure in the common rail 35 can be appropriately adjusted by the electromagnetic relief valve 25 using the detection signals output from the fuel pressure sensor 41 and the fuel temperature sensor 42, and the common rail 3
It is possible to suppress the generation of vapor and the like in the inside 5, and to start the engine smoothly even in a high temperature state.

Further, even during the engine fuel cut, the fuel pressure in the common rail 35 is reliably reduced by opening the electromagnetic relief valve 25 without using the fuel injection from the injection valve 37. Can be. As a result, it is not necessary to lower the fuel pressure by, for example, delaying the start of the fuel cut control by a certain period of time, so that it is possible to promote the improvement of the fuel efficiency and the like, and the fuel pressure in the common rail 35 following the change in the operating state of the engine. Can be quickly increased or decreased, and the drivability of the vehicle can be improved.

Further, when the engine is started, the electromagnetic relief valve 25 is opened only for a fixed time when the fuel temperature is low. Therefore, even if the high pressure pump 8 is not sufficiently driven, the low pressure pump 2 Can be quickly supplied into the common rail 35 through the relief oil passage 18 for the injection valve and the bypass passage 31, and the pressure of the injected fuel can be quickly increased to improve the startability of the engine.

Further, since the fuel pressure control valve 19 is opened only during the middle to the end of the discharge stroke, the fuel in the cylinder 10 is supplied to the low pressure pipe in the latter half of the discharge stroke when the pressure in the cylinder 10 becomes high. It can be relieved to the third side. As a result, the driving load of the high-pressure pump 8 can be reliably reduced, the energy of the engine can be saved, and the durability of the high-pressure pump 8 and the like can be improved.

In the above embodiment, steps 17, 18, 19 in FIG. 4 and steps 23, 24,
27 and 28 show specific examples of the valve control means.

In the above embodiment, step 1
0.3MPa, 0.7M as setting values used in 3, 16
Pa, steps 12, 21, 22, 23, 27
50 ° C, 1600 rpm, 4 m
Although s, 7 MPa, and 12 MPa were exemplified, the present invention is not limited to these specific numerical values.

Further, in the above embodiment, the relief oil passage 17 for the pump, the relief oil passage 18 for the injection valve, the fuel pressure control valve 19, the electromagnetic relief valve 25 and the like are arranged in the casing 9 of the high-pressure pump 8. However, the present invention is not limited to this, and these may be provided separately from the high-pressure pump 8.

In the above embodiment, the fuel temperature sensor 42 for detecting the fuel temperature in the common rail 35 is used as the temperature detecting means. However, the present invention is not limited to this. The temperature detecting means may be constituted by a water temperature sensor or the like.

Further, in the above-described embodiment, the case where the fuel injection control device is applied to a four-cylinder engine has been described as an example. However, the present invention is not limited to this.
The present invention may be applied to an engine having an arbitrary number of cylinders of up to 7 cylinders, 9 cylinders or more.

[0085]

As described above in detail, according to the first aspect of the present invention, the fuel injection control device is constituted by the injection valve, the fuel pump, the relief oil passage, and the electromagnetic relief valve. The fuel supplied to the fuel relief valve can be released to the suction side of the fuel pump by an electromagnetic relief valve as needed. And the fuel pressure can be constantly maintained in a stable state. As a result, the startability and drivability of the internal combustion engine can be reliably improved, and the reliability of the fuel injection control device can be improved.

On the other hand, according to the invention of claim 2, the fuel injection control device is constituted by an injection valve, a fuel pump, a relief oil passage for a pump, a relief oil passage for an injection valve, a fuel pressure control valve, and an electromagnetic relief valve. Therefore, the pressure of the injected fuel can be appropriately controlled in accordance with the operating state of the internal combustion engine by a fuel pressure control valve or the like. The pressure can be reduced as required by a type relief valve or the like, and the fuel pressure can be constantly maintained in a stable state. As a result, the startability and drivability of the internal combustion engine can be reliably improved, and the reliability of the fuel injection control device can be improved.

According to the third aspect of the invention, when the internal combustion engine is started in a state where the temperature detected by the temperature detecting means is equal to or higher than a predetermined temperature, the electromagnetic relief valve is set to the fuel pressure detected by the fuel pressure detecting means. When the internal combustion engine is started in a high temperature state, the temperature of the injected fuel is controlled by the valve control means and the electromagnetic relief valve by using the detection results obtained by the temperature detection means and the fuel pressure detection means. The pressure can be appropriately adjusted, the generation of vapor and the like in the fuel can be suppressed, and the internal combustion engine can be started smoothly even in a high temperature state.

Further, according to the present invention, when the fuel injection from the injection valve is stopped by the injection control means, the valve control means for opening the electromagnetic relief valve in accordance with the fuel pressure on the injection valve side is provided. With this configuration, even when the fuel injection from the injection valve is stopped, the fuel pressure is reliably reduced by opening the electromagnetic relief valve using the valve control means without using the fuel injection. be able to. As a result, the fuel pressure can be quickly increased or decreased following the change in the operating state of the internal combustion engine, and the drivability of the vehicle can be improved.

According to the fifth aspect of the present invention, since the electromagnetic relief valve is opened for at least a predetermined time when the internal combustion engine is started, even when the fuel pump is not sufficiently driven, the electromagnetic relief valve can be opened. The fuel flowing to the suction side can be quickly supplied to the injection valve side through the injection valve relief oil passage, so that the pressure of the injected fuel can be increased quickly and the startability of the internal combustion engine can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a fuel injection control device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the high-pressure pump in FIG. 1 together with a fuel pressure control valve, an electromagnetic relief valve, and the like.

FIG. 3 is a flowchart showing a fuel injection control process by a control unit.

FIG. 4 is a flowchart showing a fuel pressure control at start-up in FIG. 3;

FIG. 5 is a flowchart showing fuel pressure control during fuel cut in FIG. 3;

FIG. 6 is a characteristic diagram showing a relationship between a lift amount of a piston and an operation state of a fuel pressure control valve.

[Explanation of symbols]

 Reference Signs List 8 high-pressure pump (fuel pump) 9 casing (valve casing) 10 cylinder 11 piston 14 suction valve 16 discharge valve 17 relief oil passage for pump 18 relief oil passage for injection valve (relief oil passage) 19 fuel pressure control valve 25 electromagnetic relief valve 37 injection valve 38 control unit (injection control means) 41 fuel pressure sensor (fuel pressure detection means) 42 fuel temperature sensor (temperature detection means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 37/00 F02M 37/00 C 59/06 59/06 // F02M 51/04 51/04 Z F term (Reference) 3G060 AA03 AB00 AC08 BA20 BB00 BC03 CA01 CB01 CB05 CB06 CB07 CC02 DA01 DA06 FA07 GA01 GA03 GA06 GA14 3G066 AA02 AB02 AD12 BA00 BA12 BA17 BA19 BA23 BA37 CA01S CA04T CA05Z CA09 CA19 CA20U CA22T CB07 CD12 CD29 DA02 DB02 DB06 DB08 DB09 DB17 DC03 DC05 DC09 DC15 DC18 3G301 HA04 HA06 JA02 JA03 JA21 JA30 KA04 KA06 KA08 KA09 KA16 LB04 LB06 LB16 LC01 MA11 MA24 MA28 NA08 ND02 NE06 PB01Z PB08A PB08Z PE01Z PE03Z

Claims (5)

[Claims] 1. An injection valve for injecting fuel into a cylinder of an internal combustion engine, a fuel pump for discharging sucked fuel to the injection valve side, provided between the discharge side of the fuel pump and the injection valve,
A relief oil passage communicating with the suction side of the fuel pump; and a relief oil passage provided in the relief oil passage so as to be openable and closable. A fuel injection control device comprising: a normally closed electromagnetic relief valve for relieving a suction side of a pump. 2. An injection valve for injecting fuel into a cylinder of an internal combustion engine, and a piston reciprocating in a cylinder, and discharging the fuel sucked into the cylinder from the suction valve while the piston reciprocates in the cylinder. A fuel pump discharging to the injection valve side via a valve, a pump relief oil passage provided between the inflow side and the outflow side of the suction valve with the suction valve of the fuel pump interposed therebetween, A relief oil passage for an injection valve, which is provided between the discharge valve and the injection valve of the fuel pump and communicates with an inflow side of the suction valve, and which is openably and closably provided in the relief oil passage for the pump; A normally closed fuel pressure control valve that is opened during the middle of the discharge stroke of the fuel pump until the end thereof, and a fuel pressure control valve that is provided in the relief oil passage for the injection valve so as to be openable and closable. The valve opens when the pressure is reduced and the discharge valve flows out. The fuel injection control device in which consist of the electromagnetic relief valve normally closed to the relief of the fuel to the inlet side of the suction valve. 3. The internal combustion engine has a temperature detecting means for detecting a temperature corresponding to a temperature of fuel injected from the injector, and a fuel pressure for detecting a pressure of the fuel supplied to the injector. When the internal combustion engine is started in a state in which the temperature detected by the temperature detecting means is equal to or higher than a predetermined temperature, the electromagnetic relief valve is kept constant according to the fuel pressure detected by the fuel pressure detecting means. The fuel injection control device according to claim 1, further comprising a valve control unit that opens the valve only during the time. 4. The internal combustion engine is provided with injection control means for temporarily stopping fuel injection from the injection valve when the internal combustion engine is in a deceleration state, and the injection control means controls the injection from the injection valve by the injection control means. 4. The fuel injection according to claim 1, further comprising a valve control unit that opens the electromagnetic relief valve for a predetermined time according to the fuel pressure on the injection valve side when fuel injection is stopped. Control device. 5. The fuel injection control device according to claim 1, wherein the electromagnetic relief valve is configured to open at least for a predetermined time when the internal combustion engine is started.