JP5789976B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine including a high-pressure fuel pump that pressurizes and discharges fuel fed from a fuel tank.

  In a cylinder injection internal combustion engine, in order to ensure a high fuel pressure necessary for cylinder injection, fuel fed from a fuel tank is pressurized by a high pressure fuel pump and discharged to a high pressure fuel pipe. In such a fuel supply device, the fuel in the fuel passage is heated by the heat radiation of the internal combustion engine, and paper may be generated. As a result, so-called vapor lock occurs, and fuel injection from the injector may not be possible.

  Such vapor may occur due to a sudden change in engine operating conditions from full load operation to no load operation. Therefore, conventionally, in the fuel supply device for an internal combustion engine described in Patent Document 1, a purge valve provided between the high-pressure fuel pipe and the fuel tank is opened when the fuel is cut, and the fuel in the high-pressure fuel pipe is supplied to the fuel tank. It is trying to discharge. The purge valve is closed when the fuel flow rate in the fuel passage drops below a predetermined value.

JP 2000-329029 A

  By the way, in the fuel supply device in which the high-pressure fuel pump is arranged in or near the internal combustion engine, if the fuel flow of the high-pressure pump is stagnant during engine operation, the fuel stopped in the high-pressure fuel pump is heated by the heat radiation of the internal combustion engine. As a result, the temperature may rise and vapor may be generated in the high-pressure fuel pump. Regarding the generation of vapor in such a high-pressure fuel pump, the fuel discharge from the high-pressure fuel pipe by the purge valve as in the conventional fuel supply device takes time to discharge the fuel in the high-pressure fuel pump. It is difficult to sufficiently suppress the occurrence of vapor in

  The present invention has been made in view of such circumstances, and a problem to be solved is to provide a fuel supply device for an internal combustion engine that can suitably suppress generation of vapor in a high-pressure fuel pump. is there.

In order to solve the above-described problem, the high-pressure fuel pump includes a pump plan, which is a fuel supply device for an internal combustion engine including a high-pressure fuel pump that pressurizes and discharges fuel fed from a fuel tank. A spill valve is closed when the pressurizing chamber is contracted by raising the pump plunger, so that the fuel in the pressurizing chamber is pressurized and the outside of the high-pressure fuel pump to is what is discharged, and a relief valve for discharging to the outside in response to the opening of the fuel within the high pressure fuel pump, the relief valve when the fuel flow amount of the high-pressure fuel pump is greater than the judgment value of defined And a control unit for opening the valve, wherein the relief valve is connected to the fuel tank side with respect to the pressurizing chamber .

  When the amount of fuel flowing through the high-pressure fuel pump is small, the fuel continues to remain in the high-pressure fuel pump, and is heated by heat radiation from the internal combustion engine, resulting in high temperature and vapor. Therefore, in the above configuration, when the fuel flow rate of the high-pressure fuel pump is equal to or less than a predetermined determination value, the relief valve is opened to discharge the fuel in the high-pressure fuel pump to the outside. If the fuel in the high-pressure fuel pump is discharged to the outside, the fuel in the high-pressure fuel pump is replaced with new fuel sent from the fuel tank, so that the fuel temperature in the high-pressure fuel pump can be lowered. Therefore, according to the said structure, generation | occurrence | production of the vapor | steam in a high pressure fuel pump can be suppressed now suitably.

In order to solve the above-mentioned problem, the high-pressure fuel pump includes a pump plan, which is a fuel supply device for an internal combustion engine including a high-pressure fuel pump that pressurizes and discharges fuel fed from a fuel tank. A spill valve is closed when the pressurizing chamber is contracted by raising the pump plunger, so that the fuel in the pressurizing chamber is pressurized and the outside of the high-pressure fuel pump to is what is discharged, the relief when the relief valve for discharging to the outside in response to the opening of the fuel within the high pressure fuel pump, the fuel flow is less state of the high-pressure fuel pump continues for more than a certain period of time And a controller that opens the valve, and the relief valve is connected to the fuel tank side of the pressurizing chamber .

  If the state where the amount of fuel flowing through the high-pressure fuel pump is small continues for a certain period or longer, the fuel stopped in the high-pressure fuel pump is heated by the heat radiation of the internal combustion engine and becomes high temperature, and vapor is generated. Therefore, in the above configuration, when the state where the fuel flow of the high-pressure fuel pump is low continues for a certain period or longer, the relief valve is opened and the fuel in the high-pressure fuel pump is discharged to the outside. If the fuel in the high-pressure fuel pump is discharged to the outside, the fuel in the high-pressure fuel pump is replaced with new fuel sent from the fuel tank, so that the fuel temperature in the high-pressure fuel pump can be lowered. Therefore, according to the said structure, generation | occurrence | production of the vapor | steam in a high pressure fuel pump can be suppressed now suitably.

  It is desirable to open the relief valve until all the fuel in the high-pressure fuel pump is replaced. The replacement of the fuel can be grasped from the integrated value of the fuel circulation amount of the high-pressure fuel pump. Therefore, according to the third aspect of the present invention, if the control unit is configured to determine the period for continuing the relief valve opening based on the integrated value of the fuel flow rate of the high-pressure fuel pump, the relief valve opening period Can be set appropriately.

  In normal engine operation, as the vapor is generated, the temperature of the fuel in the high-pressure fuel pump rarely increases, and therefore the frequency of operation of the relief valve is extremely low. If the relief valve is left unused for a long period of time, sticking or the like may occur and the relief valve may not be able to be operated when necessary. Therefore, as described in claim 4, if the relief valve is forcibly opened at least once during the period from the start to the stop of the internal combustion engine, it is possible to prevent the sticking and ensure that the relief valve is operated when necessary. become able to.

  A high-pressure fuel system that supplies high-pressure fuel pressurized by a high-pressure fuel pump to the internal combustion engine, and a low-pressure fuel system that supplies low-pressure fuel that is not pressurized by the high-pressure fuel pump to the internal combustion engine. In the fuel supply device having the two fuel systems, when the fuel supply of the internal combustion engine continues for a long time by the low-pressure fuel system, the state where there is no fuel circulation of the high-pressure fuel pump is continued for a long time. Therefore, in the fuel supply device provided with such two fuel systems, the temperature of the fuel in the high-pressure fuel pump is likely to increase, and the present invention is particularly suitable for application to such a fuel supply device. .

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows typically the whole structure of the fuel supply apparatus of the internal combustion engine which concerns on one embodiment of this invention. The time chart which shows the setting aspect of the valve opening time of the relief valve in the embodiment. The time chart which shows the setting aspect of the valve closing time of the relief valve in the embodiment. The flowchart which shows the process sequence of the relief control routine employ | adopted as the embodiment.

  Hereinafter, an embodiment of a fuel supply apparatus for an internal combustion engine according to the present invention will be described in detail with reference to FIGS. In the present embodiment, the present invention is applied to a fuel supply apparatus including two fuel systems, a low pressure fuel system and a high pressure fuel system.

  First, the configuration of the fuel supply apparatus of the present embodiment will be described with reference to FIG. As shown in the figure, the discharge side of the feed pump 2 that pumps fuel from the fuel tank 1 is connected to a low-pressure side fuel passage 5 and a high-pressure side via a fuel filter 3 that purifies the fuel and a pressure regulator 4 that regulates the fuel. It is connected to the fuel passage 8. The low-pressure side fuel passage 5 is connected to a low-pressure fuel pipe 7 provided with a pulsation damper 6 that suppresses pulsation of fuel pressure. The fuel sent to the low pressure fuel pipe 7 is injected and supplied to the intake port of the internal combustion engine.

  On the other hand, the high-pressure side fuel passage 8 is connected to a high-pressure fuel pump 9 disposed in the cylinder head of the internal combustion engine. In the high-pressure fuel pump 9, the high-pressure side fuel passage 8 is connected to the pressurizing chamber 12 through an electromagnetic spill valve 11 after passing through a pulsation damper 10 that suppresses pulsation of fuel pressure. The pressurizing chamber 12 is provided with a pump plunger 15 that is moved up and down by a cam 14 provided on a camshaft 13 of the internal combustion engine.

  A high-pressure fuel passage 16 through which high-pressure fuel discharged from the pressurization chamber 12 passes is connected to the pressurization chamber 12. The high pressure fuel passage 16 is connected to a high pressure fuel pipe 19. Further, in the middle of the high-pressure fuel passage 16, a first check valve 17 that prevents backflow of fuel and a valve that opens when the fuel pressure in the high-pressure fuel pipe 19 becomes excessive to return the fuel to the high-pressure fuel pump 9. The second check valve 18 is provided. The fuel sent to the high-pressure fuel pipe 19 is directly injected into the cylinder of the internal combustion engine.

  In the fuel supply device of the present embodiment, a relief passage 20 for discharging the fuel in the high-pressure fuel pump 9 to the fuel tank 1 is connected to the pulsation damper 6 of the high-pressure fuel pump 9. In the middle of the relief passage 20, an electromagnetic relief valve 21 and a pressure regulator 22 are installed. When the relief valve 21 is opened, the fuel in the high-pressure fuel pump 9 passes through the relief passage 20 to the outside (fuel It is discharged into the tank 1).

  The on-off valve of the relief valve 21 is controlled by an electronic control unit 23 as a control unit. In addition to the control of the relief valve 21, the electronic control unit 23 also controls the fuel supply from the low pressure fuel pipe 7 and the high pressure fuel pipe 19 to the internal combustion engine.

Next, the operation of such a fuel supply device will be described.
The fuel pumped up from the fuel tank 1 by the feed pump 2 is purified by the fuel filter 3, regulated by the pressure regulator 4, and sent to the low pressure side fuel passage 5 and the high pressure side fuel passage 8. The fuel flowing into the low pressure side fuel passage 5 is sent to the low pressure fuel pipe 7 through the low pressure side fuel passage 5. On the other hand, the fuel flowing into the high pressure side fuel passage 8 is sent to the high pressure fuel pump 9 through the high pressure side fuel passage 8.

  In the high pressure fuel pump 9, the pump plunger 15 is moved up and down by the cam 14, and the electromagnetic spill valve 11 is opened when the pump plunger 15 is lowered. Then, the fuel that has flowed into the high-pressure fuel pump 9 through the opened electromagnetic spill valve 11 is introduced into the pressurizing chamber 12. When the electromagnetic spill valve 11 is closed while the pump plunger 15 is raised, the fuel in the pressurizing chamber 12 is pressurized and discharged into the high-pressure fuel passage 16 in accordance with the reduction in the volume of the pressurizing chamber 12. Then, the fuel is sent to the high pressure fuel pipe 19 through the high pressure fuel passage 16.

  In this embodiment, the electronic control unit 23 opens the relief valve 21 and discharges the fuel in the high pressure fuel pump 9 to the outside when it is determined that the high pressure fuel pump 9 becomes hot during engine operation. Like to do. Thus, the generation of vapor in the high-pressure fuel pump 9 is prevented by replacing the fuel in the high-pressure fuel pump 9.

  In the present embodiment, the electronic control unit 23 determines whether or not the high-pressure fuel pump 9 has reached a high temperature based on the fuel flow rate of the high-pressure fuel pump 9. Specifically, the electronic control unit 23 opens the relief valve 21 when the fuel flow of the high-pressure fuel pump 9 is low (here, substantially “0”) for a certain period or longer. Yes. That is, as shown in FIG. 2, when the fuel flow rate of the high-pressure fuel pump 9 becomes “0” (time T0), the electronic control unit 23 counters the time duration of the state where the fuel flow rate is “0”. Start counting up. When the counter value exceeds a prescribed high temperature judgment value (time T1), the relief valve 21 is opened.

  In the present embodiment, the electronic control unit 23 obtains the fuel flow rate of the high-pressure fuel pump 9 from the amount of fuel supplied from the high-pressure fuel pipe 19 to the internal combustion engine. For this reason, the relief valve 21 is opened when the state where the fuel supply from the high-pressure fuel pipe 19 to the internal combustion engine is stopped for a certain period or longer due to the fuel cut of the internal combustion engine or the fuel supply from the low-pressure fuel system. Become.

  In the present embodiment, the electronic control unit 23 sets the valve closing timing of the opened relief valve 21 to the integrated value (integrated circulation amount) of the fuel circulation amount of the high-pressure fuel pump 9 after the relief valve 21 is opened. Judgment is based. Specifically, the electronic control unit 23 obtains an added value of the amount of fuel supplied from the high-pressure fuel pipe 19 to the internal combustion engine and the amount of fuel discharged through the relief passage 20 in each control cycle for each specified control cycle. The accumulated distribution amount is obtained by integrating the obtained values for each control cycle. In the fuel supply device of the present embodiment, the fuel discharge amount per unit time through the relief passage 20 when the relief valve 21 is opened is substantially constant, and the fuel through the relief passage 20 in the control cycle is the same. The amount of emissions is constant.

  More specifically, as shown in FIG. 3, when the relief valve 21 is opened at time T2, the integration of the fuel flow rate of the high-pressure fuel pump 9 is started from time T2. At time T3, when the integrated flow rate exceeds a predetermined valve closing determination value, the fuel in the high-pressure fuel pump 9 is replaced, and the relief valve 21 is assumed to be sufficiently low in temperature in the high-pressure fuel pump 9. Closed.

  FIG. 4 shows a flowchart of a relief control routine applied to the present embodiment. The processing of this routine is started by the electronic control unit 23 at the start of engine operation.

  When this routine is started, it is first determined in step S100 whether the fuel flow rate of the high-pressure fuel pump 9 is "0". If the fuel flow rate is not “0” (S100: NO), the counter value is cleared in step S101, and the process returns to step S100. On the other hand, if the fuel flow rate is “0” (S100: YES), after the counter value is counted up in step S102, in step S103, it is determined whether or not the counter value exceeds the high temperature determination value. Is done. The above processing is repeated until it is determined in step S103 that the counter value exceeds the high temperature determination value.

  When the value of the counter exceeds the high temperature determination value (S103: YES), the relief valve 21 is opened in step S104, and the integrated flow amount Iq is cleared in step S105. Thereafter, the processing from step S106 to step S108 is repeated every prescribed control period until the integrated flow amount Iq exceeds the valve closing determination value. That is, in step S106, the fuel flow rate Q of the high-pressure fuel pump 9 per control cycle is calculated. In step S107, the calculated fuel flow rate Q is added to the previous value of the integrated flow rate Iq. The accumulated circulation amount Iq is updated. In step S108, it is determined whether or not the integrated flow amount Iq exceeds the valve closing determination value.

  If the integrated flow amount Iq exceeds the valve closing determination value by repeating the above processing (S108: YES), the processing returns to step S100 after the relief valve 21 is closed in step S109.

  In normal engine operation, the fuel in the high-pressure fuel pump 9 rarely increases in temperature as vapor is generated, and therefore the operation frequency of the relief valve 21 is extremely low. If the relief valve 21 is left in a non-operating state for a long period of time, sticking or the like may occur, and the relief valve 21 may not be able to be operated when necessary. Therefore, in the present embodiment, the electronic control unit 23 forcibly opens the relief valve 21 at an appropriate timing once during the period from the start to the stop of the internal combustion engine even if the high-pressure fuel pump 9 does not reach a high temperature. I am doing so. This forced valve opening is performed during fuel cut or during fuel supply by a low-pressure fuel system.

According to the fuel supply device for an internal combustion engine of the present embodiment as described above, the following effects can be obtained.
(1) In the present embodiment, the relief valve 21 that discharges the fuel in the high-pressure fuel pump 9 to the outside in response to the opening of the valve and the fuel flow in the high-pressure fuel pump 9 is “0” for a certain period or longer. An electronic control unit 23 is provided as a control unit that opens the relief valve 21 when the operation is continued. If the fuel in the high-pressure fuel pump 9 is discharged to the outside, the fuel in the high-pressure fuel pump 9 is replaced with new fuel sent from the fuel tank 1, so that the fuel temperature in the high-pressure fuel pump 9 can be lowered. . Therefore, according to the present embodiment, the generation of vapor in the high-pressure fuel pump 9 can be suitably suppressed.

  (2) In the present embodiment, the electronic control unit 23 determines the period during which the relief valve 21 continues to be opened based on the integrated value of the fuel flow rate of the high-pressure fuel pump 9 (integrated flow rate Iq). Yes. Therefore, it is possible to appropriately set the valve opening period of the relief valve 21.

  (3) In the present embodiment, the relief valve 21 is forcibly opened at least once during the period from the start to the stop of the internal combustion engine. Therefore, the relief valve 21 can be prevented from sticking, and the relief valve 21 can be reliably operated when necessary.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the relief valve 21 is forcibly opened at least once during the period from start to stop of the internal combustion engine. However, if there is no concern of the relief valve 21 being stuck, such forced opening may not be performed.

  In the above embodiment, the period during which the relief valve 21 is continuously opened is determined based on the integrated value of the fuel flow rate of the high pressure fuel pump 9 (integrated flow rate Iq). It is also possible to adopt a mode for determining the valve timing. For example, it is conceivable to always open the relief valve 21 for a certain period of time.

  In the above embodiment, the relief valve 21 is opened when the fuel flow rate of the high-pressure fuel pump 9 is substantially “0” for a certain period of time. In both cases, the relief valve 21 may be opened when the fuel flow rate of the high-pressure fuel pump 9 is sufficiently small. In addition, the relief valve 21 may be opened when the total amount of fuel flowing through the high-pressure fuel pump 9 during a certain period is equal to or less than a predetermined value. The fuel flow rate here is substantially “0”, which means the fuel flow rate excluding fuel leakage from the sliding portion of the high-pressure fuel pump 9 or the like.

  In the above embodiment, the case where the fuel supply device of the present invention is applied to an internal combustion engine provided with two fuel systems of a low pressure fuel system and a high pressure fuel system has been described. The present invention can be similarly applied to the fuel supply device provided.

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Feed pump, 3 ... Fuel filter, 4 ... Pressure regulator, 5 ... Low pressure side fuel passage, 6 ... Pulsation damper, 7 ... Low pressure fuel piping, 8 ... High pressure side fuel passage, 9 ... High pressure fuel Pump 10 pulsation damper 11 electromagnetic spill valve 12 pressure chamber 13 cam shaft 14 cam 15 pump plunger 16 high pressure fuel passage 17 first check valve 18 Second check valve, 19: high-pressure fuel pipe, 20: relief passage, 21: relief valve, 22: pressure regulator, 23: electronic control unit (control unit).

Claims (5)

In a fuel supply device for an internal combustion engine comprising a high-pressure fuel pump that pressurizes and discharges fuel fed from a fuel tank,
The high pressure fuel pump includes a pump plunger, and when the pressurization chamber is reduced by the pump plunger being raised, the electromagnetic spill valve is closed to pressurize the fuel in the pressurization chamber. Being discharged outside the high-pressure fuel pump,
A relief valve for discharging the fuel in the high-pressure fuel pump to the outside in response to opening of the valve;
A control unit that opens the relief valve when a fuel flow rate of the high-pressure fuel pump is equal to or less than a predetermined determination value;
Equipped with a,
The fuel supply device for an internal combustion engine, wherein the relief valve is connected to the fuel tank side with respect to the pressurizing chamber . In a fuel supply device for an internal combustion engine comprising a high-pressure fuel pump that pressurizes and discharges fuel fed from a fuel tank,
The high-pressure fuel pump includes a pump plunger, and when the pressurization chamber is contracted by raising the pump plunger, the electromagnetic spill valve is closed to pressurize the fuel in the pressurization chamber. Being discharged outside the high-pressure fuel pump,
A relief valve for discharging the fuel in the high-pressure fuel pump to the outside in response to opening of the valve;
A control unit that opens the relief valve when a state where the fuel flow of the high-pressure fuel pump is low continues for a certain period of time; and
Equipped with a,
The fuel supply device for an internal combustion engine, wherein the relief valve is connected to the fuel tank side with respect to the pressurizing chamber . The fuel supply device for an internal combustion engine according to claim 1 or 2, wherein the control unit determines a period during which the relief valve is continuously opened based on an integrated value of a fuel flow rate of the high-pressure fuel pump. The fuel supply device for an internal combustion engine according to any one of claims 1 to 3, wherein the relief valve is forcibly opened at least once in a period from start to stop of the internal combustion engine. The fuel supply apparatus includes a high pressure fuel system that supplies high pressure fuel pressurized by the high pressure fuel pump to the internal combustion engine, and a low pressure fuel system that supplies low pressure fuel not pressurized by the high pressure fuel pump to the internal combustion engine. The fuel supply device for an internal combustion engine according to any one of claims 1 to 4, comprising one fuel system.

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