JP4924413B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine that uses a fuel accumulator such as a common rail.

  As is well known, in a diesel internal combustion engine or an in-cylinder direct injection type gasoline internal combustion engine, a high-pressure fuel supply device including a fuel pressure accumulator (common rail, fuel rail) is used to perform high-pressure injection from an injector. Yes. Such a fuel supply apparatus generally includes a plunger that pressurizes a working chamber provided between a low-pressure passage connected to the feed pump and a high-pressure passage connected to the fuel accumulator, and includes a low-pressure passage and a working chamber. A control valve is provided between the operating chamber and the high-pressure passage, and the operating chamber is pressurized by opening the control valve according to the pressurizing operation (lifting operation) of the plunger. Fuel is supplied to the high-pressure passage through a check valve.

Here, in the normal return type, a pressure reducing valve is provided in the return passage from the fuel pressure accumulating portion to the fuel tank, and the pressure is reduced at the time of depressurization when it is not necessary to maintain the fuel pressure accumulating portion at a high pressure as in the engine deceleration operation. The valve is opened so that the fuel on the fuel accumulator side is returned to the fuel tongue through the fuel return passage. Further, in Patent Document 1, a check valve provided between the high pressure passage and the working chamber is a bidirectional valve, and at the time of the pressure reduction, the bidirectional valve is opened so that the fuel in the high pressure passage is low pressure through the working chamber. It is designed to return to the aisle side.
Japanese Patent Laid-Open No. 10-318060

  In the former normal return type, it is necessary to provide a return passage extending from the fuel accumulator to the fuel tank separately from the low pressure passage and the high pressure passage, and to switch and control the pressure reducing valve provided in the return passage separately from the control valve. There were problems such as an increase in the number of parts, a complicated structure including a control system, an increase in size and an increase in weight.

  In the configuration using the bidirectional valve as in Patent Document 1, the return type pressure reducing valve and the return passage are not necessary, but the bidirectional valve is an actuator that resists the differential pressure between the high pressure passage and the working chamber. There are also problems such as an increase in the number of parts, an increase in size, and an increase in weight because the actuator and its control processing are required. In addition, since the above-described differential pressure and pressure fluctuation acting on the bidirectional valve are large, it is very difficult to reliably operate only with the driving force of the actuator.

  The present invention has been made in view of such problems, and stably reduces the pressure on the high-pressure passage side while having a simple structure using a control valve provided between the low-pressure passage and the working chamber. It is an object of the present invention to provide a new fuel supply device for an internal combustion engine.

  Accordingly, the present invention provides a plunger for pressurizing a working chamber provided between the low pressure passage and the high pressure passage, and a back flow of fuel from the high pressure passage to the working chamber provided between the high pressure passage and the working chamber. In the fuel supply device for an internal combustion engine, comprising: a first check valve that performs control, a control valve that switches communication / blocking between the low pressure passage and the working chamber, and a control unit that controls operation of the control valve. And a second check valve that opens and closes the bypass passage according to the pressure in the working chamber.

  With the above configuration, when supplying high pressure fuel to the high pressure passage side, the high pressure fuel pressurized in the working chamber is supplied to the high pressure passage by closing the control valve when the working chamber is pressurized by the plunger. Can do. At the time of depressurization, the control valve is closed when the working chamber is depressurized by the plunger, thereby opening the second check valve using the negative pressure in the working chamber and returning the fuel from the high pressure passage to the low pressure passage through the bypass passage. it can.

  According to the present invention, in addition to the existing control valve, it is possible to stably perform pressure reduction on the high pressure passage side with a simple configuration using a high pressure passage or a low pressure passage as a return passage. The actuator can be simplified, the structure can be simplified, the size and weight can be significantly reduced, and the control system can be simplified.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a fuel supply device for an internal combustion engine according to a first embodiment of the present invention. In this fuel supply device 1, a low-pressure fuel adjusted to a predetermined feed pressure by a feed pump 2 is supplied from a fuel tank 3 through a low-pressure passage 4, and the fuel is pressurized to a high pressure and supplied to a high-pressure passage 5. Is. The high-pressure fuel is supplied to the fuel pressure accumulating section 6, also called a common rail / fuel rail, through the high-pressure passage 5, and the high-pressure fuel is injected from each injector 7 connected to the fuel pressure accumulating section 6 at an appropriate injection timing.

  The fuel supply apparatus 1 includes a low-pressure chamber 11 that forms part of the low-pressure passage 4, a high-pressure chamber 12 that forms part of the high-pressure passage 5, and a working chamber 13 that is provided between the both 11 and 12. A plunger 14 that is provided in the housing 10 and pressurizes the fuel in the working chamber 13, a first check valve 15 that prevents a backflow of fuel from the high pressure chamber 12 to the working chamber 13, the low pressure chamber 11 and the working chamber. And a control valve 17 for switching communication / blocking with the communication device 13. The plunger 14 is driven to reciprocate via a pump cam by rotational power of a crankshaft (not shown). When the load in the valve opening direction (the load from the working chamber 13) exceeds the load in the valve closing direction (the sum of the load from the high pressure chamber 12 and the load due to the spring force of the first spring 16) of the first check valve 15. As a result, the pressurized high pressure fuel in the working chamber 13 is supplied to the high pressure chamber 12. The control valve 17 is a solenoid valve that opens and closes according to the energization state of the solenoid 18, and its operation, that is, the energization state of the solenoid 18 is controlled by the control unit 20.

  In this embodiment, a bypass passage 21 for returning fuel from the high-pressure chamber 12 of the high-pressure passage 5 to the low-pressure chamber 11 of the low-pressure passage 4 is provided, and the second reverse passage that opens and closes the bypass passage 21 according to the pressure in the working chamber 13. A stop valve 22 is provided. The second check valve 22 includes a bottomed cylindrical large-diameter portion 23 slidably disposed on the cylindrical portion 1A of the housing 1, and a small-diameter needle valve extending coaxially from the large-diameter portion 23. 24, and is always urged in the valve closing direction by the spring force (biasing force) of the second spring 25 as the urging member. The second check valve 22 closes the bypass passage 21 by the tip of the needle valve 24 being seated on the opening edge of the bypass passage 21 from the low pressure chamber 11 side, and the second check valve 22 is connected to the bypass passage 21 from the low pressure chamber 11. The flow is prohibited. The low-pressure chamber 11 and the working chamber 13 are liquid-tightly defined by the large-diameter portion 23, but a seal ring is interposed between the large-diameter portion 23 and the cylindrical portion 1A in order to improve sealing performance. You may do it.

  FIG. 2 is a time chart showing the opening / closing timing of the control valve 17, etc., (A) is when the engine is in steady operation, that is, when fuel is supplied to supply high pressure fuel to the fuel accumulator 6, and (B) is when the engine is decelerating. That is, the operation at the time of depressurization of the fuel accumulator 6 is shown. FIG. 3 shows the load acting on the second check valve 22 when the fuel pressure on the high pressure chamber side is the highest and the fuel pressure on the high pressure chamber side is the lowest.

  At the time of fuel supply, as shown in FIG. 2A, the control valve 17 is closed during the ascending stroke in which the plunger 14 rises toward the working chamber 13, that is, when the working chamber 13 is pressurized. As a result, the inside of the working chamber 13 is pressurized in accordance with the rise of the plunger 14, and the load in the valve opening direction in the working chamber 13 is the load in the valve closing direction (the sum of the load on the high pressure chamber side and the load of the first spring 16). The first check valve 15 is opened, and the high-pressure fuel in the working chamber 13 is supplied to the high-pressure chamber 12 side of the high-pressure passage 5. Further, the fuel supply amount can be appropriately adjusted by adjusting the closing timing of the control unit 20 within the ascending stroke as indicated by reference numeral 31 in FIG.

  Here, as indicated by reference numerals 32 and 33 in FIG. 3, the spring load (set load) by the spring force of the second spring 25 urging the second check valve 22 in the valve closing direction is high and low. Regardless of the time, the load in the valve opening direction, that is, the load received from the high pressure chamber side (strictly, the sum of the load from the bypass passage 21 and the load from the low pressure chamber 11) and the working chamber 13 at the time of this fuel supply Is set to be sufficiently larger than the sum of the load at the maximum negative pressure acting on (see reference numerals 32 and 33). Therefore, the second check valve 22 is maintained in the closed state when fuel is supplied, and does not open carelessly.

  At the time of depressurization, as shown in FIG. 2B, the control valve 17 is closed during the downward stroke of the plunger 14, that is, at the time of depressurization of the working chamber. As a result, the pressure in the working chamber 13 decreases and the negative pressure increases as the plunger 14 descends, and as shown in FIG. 3, the load in the valve closing direction of the second check valve 22 (second spring 25). The load in the valve opening direction, taking into account the load due to the negative pressure in the working chamber 13 (the maximum negative pressure load at the time of decompression), greatly exceeds the spring load), and the second check valve 22 is reliably opened. Can be valved. Here, the first check valve 15 is reliably maintained in the closed state by strengthening the negative pressure in the working chamber 13. Thus, by opening the second check valve 22, the fuel is returned from the high pressure passage 5 to the low pressure passage 4, and the pressure of the fuel accumulator 6 is reduced. Further, by adjusting the closing timing of the control valve 17, it is possible to appropriately adjust the fuel return amount, that is, the degree of pressure reduction (see reference numeral 34).

  As described above, according to this embodiment, the existing control valve 17 that is closed in the ascending stroke of the plunger 14 is used when fuel is supplied, and the control valve 17 is closed in the descending stroke of the plunger 14 when the pressure is reduced. The second check valve 22 is opened by increasing the negative pressure of the fuel, and the fuel flows from the high pressure chamber 12 side to the low pressure chamber 11 side, that is, from the fuel accumulator 6 to the fuel pump 3 side through the bypass passage 21 without passing through the working chamber 13. Can be returned. Since an additional actuator or the like is not required as in the conventional example described above and the high pressure passage 5 or the low pressure passage 4 is used as a return passage in addition to the existing control valve 17, the structure is simplified, It is possible to greatly reduce the size and weight and simplify the control system.

  Further, the second check valve 22 is a needle valve 24 of the second check valve 22 whose pressure receiving area on the back side of the large diameter portion 23 facing the working chamber 13 faces the bypass passage 21 communicating with the high pressure passage 5. Is set to be much larger than the pressure receiving area. For this reason, the pressure (negative pressure) in the working chamber 13 can be applied to the second check valve 22 greatly, and the second check valve 22 can be stably opened regardless of the pressure on the high pressure passage 5 side during pressure reduction. Can be valved.

  FIG. 4 shows a fuel supply apparatus for an internal combustion engine according to the second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted as appropriate, and differences from the first embodiment will be mainly described. In the second embodiment, the second check valve 22A is disposed between the valve opening direction distal end portion 35 of the control valve 17A and the valve closing direction proximal end portion 36 of the large diameter portion 23 of the second check valve 22A. A second spring 25A that is biased in the valve closing direction (the right direction in FIG. 4) is provided coaxially in a compressed state. According to the second embodiment, as shown in FIG. 5, when the fuel is supplied, when the control valve 17 is lifted in the valve opening direction (right direction in FIG. 4), the second spring 25A and The second check valve 22A is pushed out in the valve closing direction (right direction in FIG. 4), and the set load of the second spring 25A increases, so that the second check valve 22A is more stably and reliably closed. Can be maintained in a state. On the other hand, at the time of depressurization, the control valve 17A is closed, that is, the second reverse spring 25A and the second check valve 22A are located in the most valve opening direction (left direction in FIG. 4). Since the stop valve 22A is opened, the set load due to the valve lift described above does not act, and the valve opening operation of the second check valve 22A is not adversely affected.

1 is a cross-sectional view showing a fuel supply device for an internal combustion engine according to a first embodiment of the present invention. The timing chart which shows the opening / closing operation | movement of the control valve of the said 1st Example at the time of fuel supply (A) and pressure reduction (B). Explanatory drawing which shows the load which acts on the 2nd check valve of the said 1st Example. Sectional drawing which shows the fuel supply apparatus of the internal combustion engine which concerns on 2nd Example of this invention. Explanatory drawing which shows the load which acts on the 2nd non-return valve of the said 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel supply apparatus 4 ... Low-pressure channel | path 5 ... High-pressure channel | path 6 ... Fuel pressure storage part 13 ... Actuation chamber 14 ... Plunger 15 ... 1st non-return valve 17, 17A ... Control valve 20 ... Control part 21 ... Bypass passage 22, 22A ... Second check valve 25, 25A ... second spring (biasing member)

Claims (5)

A plunger for pressurizing a working chamber provided between the low pressure passage and the high pressure passage;
A first check valve provided between the high pressure passage and the working chamber to prevent a back flow of fuel from the high pressure passage to the working chamber;
A control valve for switching communication / blocking between the low pressure passage and the working chamber;
In a fuel supply device for an internal combustion engine having a control unit that controls the operation of the control valve,
A bypass passage for returning fuel from the high pressure passage to the low pressure passage;
A second check valve that opens and closes the bypass passage according to the pressure in the working chamber;
A fuel supply device for an internal combustion engine, comprising:   The fuel supply device for an internal combustion engine according to claim 1, wherein the second check valve has a pressure receiving area facing the working chamber larger than a pressure receiving area facing the bypass passage.   The control unit closes the control valve when the pressure of the working chamber is increased so that the plunger pressurizes the working chamber when supplying the high-pressure fuel in the working chamber to the high-pressure passage, and supplies the fuel from the high-pressure passage to the low-pressure passage through the bypass passage. 3. The fuel supply device for an internal combustion engine according to claim 1, wherein the control valve is closed at the time of decompression of the working chamber in which the plunger depressurizes the working chamber when the pressure is returned.   An urging member for urging the second check valve in the valve closing direction, and the urging force of the urging member is set so as to maintain the second check valve in a closed state at least when the fuel is supplied; The fuel supply device for an internal combustion engine according to claim 3, wherein the fuel supply device is an internal combustion engine.   The internal combustion engine according to any one of claims 1 to 3, wherein a spring is interposed in a compressed state between a valve opening direction distal end of the control valve and a valve closing direction proximal end of the spring. Fuel supply system.

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