JP2000240528A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a manufacturing cost of a fuel injection device by dispensing with an escape pipe and a safety valve for reducing fuel pressure in an accumulation chamber. SOLUTION: This fuel injection control device has an accumulation chamber, a fuel injection valve connected to the accumulation chamber, a fuel pump, a discharge pipe for introducing the fuel discharged from the fuel pump to the accumulation chamber, check valves 12e, 12g arranged on the discharge pipe and opened by a specified pressure difference, and a valve opening means 12h for forcibly opening the check valves 12e, 12g at the time of operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection control device for an internal combustion engine.

[0002]

2. Description of the Related Art In order to directly inject high-pressure fuel into a cylinder, a high-pressure fuel is stored in a pressure-accumulation chamber, and the fuel in the pressure-accumulation chamber is injected through a fuel injection valve arranged for each cylinder. A known fuel injection device is known.

[0003] The accumulator and the fuel tank are connected via a fuel pump. The fuel pump is configured to pump the amount of fuel injected during the predetermined period to the storage chamber at predetermined intervals to maintain the internal pressure of the storage chamber at the target fuel pressure. The fuel pump has a discharge stroke for pumping the fuel in the pump chamber to the pressure accumulating chamber and a suction stroke for sucking the fuel in the fuel tank into the pump chamber. In the suction stroke, the fuel pressure in the pump chamber is set in the accumulating chamber. Will be lower than the fuel pressure. Thereby, a check valve for preventing fuel in the accumulator from flowing back to the pump chamber of the fuel pump is disposed in the discharge pipe communicating the fuel pump with the accumulator.

In the fuel injection device having such a configuration, when the fuel pressure in the accumulator significantly exceeds the target fuel pressure due to, for example, an abnormality in the fuel injection valve, the fuel in the accumulator is returned to the fuel tank. A relief pipe with a safety valve that opens at a set pressure is required.

[0005]

Such a relief pipe and a safety valve are required to have high quality so as not to cause a fuel leak or the like because a high target fuel pressure always acts, and are relatively expensive. It is. Thereby, the cost of the whole fuel injection device is increased considerably.

Accordingly, an object of the present invention is to eliminate the need for a relief pipe and a safety valve for lowering the fuel pressure in a pressure accumulator in a fuel injection device having a pressure accumulator, thereby reducing the cost of the fuel injector. .

[0007]

According to a first aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine, comprising: a pressure accumulator, a fuel injection valve connected to the pressure accumulator, a fuel pump, and the fuel pump. A discharge pipe for guiding fuel discharged from the pressure accumulator to the pressure accumulating chamber, a check valve arranged in the discharge pipe and opened by a predetermined pressure difference, and an opening for forcibly opening the check valve when activated. And valve means.

According to a second aspect of the present invention, there is provided a fuel injection control apparatus for an internal combustion engine according to the first aspect, wherein the reverse valve is operated when the valve opening means is not operated. The stop valve allows only the fuel flow from the fuel pump to the accumulator when the predetermined pressure difference occurs.

According to a third aspect of the present invention, there is provided the fuel injection control apparatus for an internal combustion engine according to the first aspect, wherein the reverse valve is opened when the valve opening means is not operated. The stop valve allows only the fuel flow from the accumulator to the fuel pump when the predetermined pressure difference occurs.

[0010]

FIG. 1 is a schematic diagram showing an embodiment of a fuel injection control device for an internal combustion engine according to the present invention. Although the internal combustion engine in the present embodiment will be described below as having four cylinders, this does not limit the present invention. FIG.
In the drawings, reference numeral 1 denotes four fuel injection valves arranged for each cylinder, and reference numeral 2 denotes a pressure accumulation chamber for supplying high-pressure fuel to each fuel injection valve 1. The fuel injection valve 1 has a valve element for opening and closing the injection hole, and a solenoid for sucking the valve element in the valve opening direction. The spring force and the fuel pressure in the pressure accumulating chamber 2 act on the valve body in the valve closing direction. When the solenoid is demagnetized, reliable valve closing is compensated and fuel injection is stopped.
When the solenoid is excited, the solenoid sucks the valve body in the valve opening direction against the spring force and the fuel pressure, and fuel injection is performed.

Reference numeral 3 denotes a fuel tank, in which a low-pressure pump 4 is disposed. The low-pressure pump 4 is an electric pump driven by a battery.
It has a rated discharge pressure of 0.3 MPa. The low-pressure pump 4 is activated simultaneously with the ON signal of the starter switch. Reference numeral 6 denotes a filter for removing foreign matter from the fuel sucked by the low-pressure pump 4.

Reference numeral 7 designates a pressure accumulating chamber 2 having, for example,
This is a high-pressure pump for raising the pressure to near the target fuel pressure of MPa. The high-pressure pump 7 has a plunger 7a that can slide in the cylinder. The space 7d in the cylinder of the high-pressure pump 7 having the suction side opening 7b and the discharge side opening 7c serves as a pump chamber. The sliding operation of the plunger 7a for narrowing the pump chamber 7d, that is, the discharge stroke operation of the plunger 7a is provided by the cam 7e connected to the crankshaft of the engine body, and the sliding operation of the plunger 7a for expanding the pump chamber 7d. That is, the suction stroke operation of the plunger 7a is provided by the compression spring 7f. In the present embodiment, the cam 7e provides two discharge strokes in one rotation. However, the cam 7e is provided via a reduction gear or the like so that one rotation of the cam 7e corresponds to two rotations of the crankshaft. It is connected to a crankshaft, that is, a discharge stroke of the high-pressure pump 7 is provided for each fuel injection of the two cylinders.

The suction opening 7b of the pump chamber 7d communicates with the control chamber 7g. The control chamber 7 g is connected on the one hand to the discharge side of the low-pressure pump 4 by a suction pipe 8 and on the other hand to the fuel tank 3 by a return pipe 9.
A filter 10 for removing foreign matter from fuel discharged from the low-pressure pump 4 is disposed in the suction pipe 8.

The discharge side opening 7c of the pump chamber 7d is connected to the accumulator 2 by a discharge pipe 11. The discharge pipe 11 is provided with a check valve device 12, which will be described in detail later.

Reference numeral 16 denotes a solenoid valve for opening and closing the suction side opening 7b of the high-pressure pump 7. The electromagnetic valve 16 is closed by exciting the electromagnetic solenoid 16a, and is opened by a spring 16b by demagnetizing the electromagnetic solenoid 16a. The solenoid valve 16 is opened during the suction stroke of the high-pressure pump 7 and is closed for a required time during the discharge stroke. Thereby, during the suction stroke of the high-pressure pump 7,
Fuel discharged from the low-pressure pump 4 is sucked into the pump chamber 7d,
During closing of the solenoid valve 16 in the discharge stroke, the discharge pipe 11 is closed.
The fuel in the pump chamber 7d is pumped to the pressure accumulating chamber 2 via

Reference numeral 20 denotes a control device for controlling the opening and closing of the electromagnetic valve 16 via the electromagnetic solenoid 16a, and a pressure sensor 21 for detecting the fuel pressure in the accumulator 2 and an engine operating state. Sensors (not shown) for detecting the current engine operating state, such as an air flow meter, a rotation sensor, and a cooling water temperature sensor.

FIG. 2 shows the high-pressure pump 7 by the control device 20.
3 is a flowchart for opening / closing control of the electromagnetic valve 16 of FIG. This flowchart is executed simultaneously with the ON signal of the starter switch, and is repeated every discharge stroke of the high-pressure pump 7. First, in step 101,
The actual fuel pressure P in the accumulator 2 is measured by the pressure sensor 21. Next, at step 102, a pressure difference dP between the target fuel pressure Pt and the actual fuel pressure P is calculated, and the routine proceeds to step 103.

In step 103, the pressure difference d
It is determined whether P is equal to or greater than a predetermined value dP '. If this determination is denied, the actual fuel pressure P becomes the target fuel pressure P
It is a value relatively close to t. At this time, step 104
, The solenoid valve 16 in the discharge stroke of the high-pressure pump 7
Is controlled so that only the fuel amount obtained by adding the pressure compensation fuel amount for reducing the pressure difference dP to the fuel injection amount determined according to the engine operating state is discharged. Here, when the pressure difference dP is a negative value, that is, when the actual fuel pressure P exceeds the target fuel pressure Pt, the pressure compensation fuel amount becomes a negative value and is subtracted from the current fuel injection amount. .

The pressure-compensating fuel amount is relatively small. As a result, the high-pressure pump 7 may need to discharge several times before the actual fuel pressure P substantially matches the target fuel pressure Pt.
, The fuel injection amount control does not cause any problem by slightly correcting the valve opening time of the fuel injection valve. Thus, the relatively small amount of the pressure-compensating fuel can prevent the actual fuel pressure P from fluctuating largely around the target fuel pressure Pt. of course,
The pressure compensating fuel amount may be changed according to the magnitude of the pressure difference dP.

On the other hand, when the determination in step 103 is affirmative, that is, when the target fuel pressure Pt and the actual fuel pressure Pt
When the actual fuel pressure P is significantly lower than the target fuel pressure Pt when the pressure difference dP from the pressure difference dP is equal to or more than the predetermined value dP ′, the routine proceeds to step 105, where the electromagnetic pressure is applied over the entire discharge stroke of the high-pressure pump 7. The valve 16 is closed, and the high-pressure pump 7 is operated at the maximum discharge rate. That is, all the discharged fuel amounts other than those used for the fuel injection are regarded as the pressure-compensating fuel amounts.
At this time, since the current pressure difference dP between the target fuel pressure Pt and the actual fuel pressure P is relatively large, there is a possibility that the intended fuel amount cannot be injected even if the valve opening time of the fuel injection valve is corrected. The actual fuel pressure P is quickly changed to the target fuel pressure Pt.
It is necessary to almost match. Thereby, the pressure compensation fuel amount is set to be large.

FIG. 3 is an enlarged sectional view of the check valve device 12 described above. As shown in FIG.
Has a case 12 a having a larger diameter than the discharge pipe 11.
Discharge pipe connection 1 on high-pressure pump 7 side in case 12a
2b constitutes a valve seat portion, and the valve seat portion 12b
Is provided with a valve body 12c that can be brought into contact with the valve body 12c. Valve body 12c
Has a rod 12d that extends downstream in the case 12a.

At the center of the case 12a is a rod 12d.
Are fixed. This guide member 12e is provided with a plurality of through holes 12f, whereby a passage cross-sectional area equal to or larger than the passage cross-sectional area of the discharge pipe 11 is secured between the upstream side and the downstream side of the guide member 12e. . The guide member 12e also has a function of supporting a compression spring 12g that urges the valve body 12c in the valve closing direction.

A solenoid 12h is provided downstream of the guide member 12e, and a central through hole 1 of the solenoid 12h is provided.
It communicates with the pressure accumulation chamber 2 side of the discharge pipe 11 via 2i.
The rod 12d is connected to the central through hole 12i of the solenoid 12h.
Extends to the inside.

The compression spring 12g has a very small spring constant. If the fuel pressure on the high-pressure pump side slightly exceeds the fuel pressure on the accumulation chamber side, the valve body 12a is easily opened. Thus, the solenoid valve 1 of the high-pressure pump 7 described above
When the fuel is discharged from the high-pressure pump 7 by the opening / closing control of 6, the discharged fuel sequentially passes through the valve seat 12b, the through hole 12f of the guide member 12e, and the central through hole 12i of the solenoid 12h. The pressure is sent to the accumulator 2.

On the other hand, even if the fuel pressure in the pressure accumulating chamber side exceeds the fuel pressure in the high pressure pump side, the valve body 12a is not opened, and the valve body 12a is not opened during the suction stroke of the high pressure pump 7 or the high pressure pump 7 When the solenoid valve 16 is opened during the discharge stroke, the fuel pressure on the high-pressure pump side may be significantly lower than the fuel pressure on the accumulator chamber side, but no backflow of fuel occurs.

In the present embodiment, generally, the pressure accumulating chamber 2
There is no relief pipe and safety valve connected to. However, since the check valve device 12 has the above-described configuration, the solenoid 12h can be excited to forcibly open the valve body 12c as necessary. Thereby, by monitoring the fuel pressure in the pressure accumulating chamber 2 by the pressure sensor 21, for example, when the pressure in the pressure accumulating chamber 2 becomes abnormally high, or otherwise, the fuel pressure in the pressure accumulating chamber 2 is reduced. When it is desired to use the solenoid 12h, for example, duty control is performed on the valve opening period of the valve element 12c, so that the fuel pressure in the accumulator 2 can be set to a desired fuel pressure.

In particular, the valve element 1 using the solenoid 12h
If the time for forcibly opening the valve 2c is at the time of the suction stroke of the high-pressure pump 7 or the time at which the solenoid valve 16 is opened at the time of the discharge stroke, the fuel pressure in the accumulator 2 is reduced by the low-pressure pump 4c.
Can be freely reduced to the rated discharge pressure.

It is also possible to use the above-described check valve device 12 with the high-pressure pump side and the pressure accumulation chamber side reversed.
In this case, the compression spring 12g has a relatively large spring constant, and when the solenoid 12h is demagnetized, the valve body 12c only when the pressure in the accumulator 2 becomes equal to or higher than the target fuel pressure. Is opened. In this manner, if the pressure inside the pressure accumulating chamber 2 becomes higher than the set pressure due to some factor, the valve element 12c is automatically opened, thereby preventing the pressure inside the pressure accumulating chamber 2 from becoming higher than the set pressure.

On the other hand, the valve 12 is controlled by the solenoid 12h so as to coincide with the closing of the solenoid valve 16 of the high-pressure pump 7.
Although it is necessary to open the valve c, this makes it possible to pump the fuel discharged from the high-pressure pump 7 to the pressure accumulating chamber 2 and, when the pressure in the accumulating chamber 2 is lower than the set pressure,
It is possible to prevent the fuel from flowing backward from the accumulator 2 to the high-pressure pump 7.

In the above-described embodiment, the valve element 12c of the check valve device can be forcibly opened by the solenoid 12h, but this is not a limitation of the present invention.
Another actuator such as a step motor can be used instead of the solenoid.

[0031]

As described above, the fuel injection device for an internal combustion engine according to the present invention is provided with a check valve which is opened by a predetermined pressure difference in a discharge pipe for guiding fuel discharged from a fuel pump to a pressure accumulating chamber. And a valve opening means for forcibly opening the check valve during operation. Thereby, generally, two valves, a check valve for preventing backflow of fuel from the accumulator and a safety valve for lowering the fuel pressure of the accumulator, are required. According to the fuel injection device of the internal combustion engine, when the check valve is used as a check valve, the function as a safety valve can be provided by enabling forced opening by the valve opening means.
When the check valve is used as a safety valve, the function as a check valve can be provided by enabling the valve opening means to forcibly open the valve. In this way, it is possible to omit the relatively expensive safety valves and relief pipes that are generally required, thereby reducing the cost of the fuel injection device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a fuel injection control device for an internal combustion engine according to the present invention.

FIG. 2 is a flowchart for opening / closing control of a solenoid valve of a high-pressure pump.

FIG. 3 is an enlarged sectional view of a check valve device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 2 ... Pressure accumulation chamber 3 ... Fuel tank 4 ... Low pressure pump 7 ... High pressure pump 12 ... Check valve device 16 ... Solenoid valve 20 ... Control device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G066 AA07 AB02 AC09 AD12 BA12 BA61 CA01S CA04U CA09 CB01 CB07T CB07U CB09 CB12 CB16 CD26 CD29 CE13 CE22 DC18

Claims (3)

[Claims] 1. An accumulator, a fuel injection valve connected to the accumulator, a fuel pump, a discharge pipe for guiding fuel discharged from the fuel pump to the accumulator, and a discharge pipe. A fuel injection control device for an internal combustion engine, comprising: a check valve that is opened by a predetermined pressure difference and a valve opening unit that forcibly opens the check valve when activated. 2. The non-return valve according to claim 2, wherein the check valve permits only a fuel flow from the fuel pump to the pressure accumulating chamber when the predetermined pressure difference occurs. Item 2. A fuel injection control device for an internal combustion engine according to Item 1. 3. The non-return valve, when the valve opening means is not operated, permits only a fuel flow from the accumulator to the fuel pump when the predetermined pressure difference occurs. Item 2. A fuel injection control device for an internal combustion engine according to Item 1.