JP2016044598A - Fuel supply system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately suppress a check valve 58 provided between a passage-side injection valve 14 and a feed pump 50 from being closed by pulsation generated downstream of the check valve 58.SOLUTION: A bypass passage 84 is provided downstream of a check valve 58. The bypass passage 84 is intended to cause fuel in a low-pressure fuel passage 22 to reversely flow to an inlet vessel 51. An electronically-controlled selector valve 86 switching the state of the bypass passage 84 over between a communication state and a cutoff state is provided in the bypass passage 84. An ECU 90 controls the selector valve 86 to be opened when a fuel injection quantity of a passage-side injection valve 14 or the like is small.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine, a fuel tank that stores fuel supplied to the internal combustion engine, a feed pump that sucks and discharges fuel from the fuel tank, and fuel injection by pressurizing fuel discharged from the feed pump The present invention relates to a fuel supply device for an internal combustion engine that is applied to a fuel supply system for an internal combustion engine that includes a high pressure fuel pump that supplies the valve.

  For example, Japanese Patent Laid-Open No. 2004-133620 proposes a check valve provided between a feed pump and a fuel injection valve, and a branch passage that allows fuel to flow out to the jet pump downstream of the check valve. Here, a residual pressure holding valve for maintaining the pressure of the branch passage at a predetermined pressure is provided upstream of the jet pump in the branch passage. Specifically, the valve opening pressure of the residual pressure holding valve is set lower than the minimum fuel pressure when the feed pump is driven. As a result, the residual pressure holding valve is always open over the period during which the feed pump is driven, the jet pump functions, and a part of the fuel pumped up from the feed pump passes downstream of the feed pump via the jet pump. To flow backwards. On the other hand, when the feed pump is stopped, the pressure on the downstream side of the check valve is maintained at the valve opening pressure of the residual pressure holding valve by closing the residual pressure holding valve. In particular, this document describes that the pressure on the downstream side of the check valve is maintained at about “200 kPa” by closing the residual pressure holding valve.

JP 2010-216433 A

  By the way, when the injection pressure of the fuel injection valve is variable, the valve opening pressure of the residual pressure holding valve needs to be set to be equal to or lower than the minimum value of the injection pressure. When the valve opening pressure is set low, the fuel pressure downstream of the check valve decreases when the feed pump stops and the check valve closes, and as a result, vapor tends to occur during dead soak. Has been found by the inventors.

  In order to solve this problem, when a residual pressure holding valve is provided upstream of the check valve, a fuel supply system including a high-pressure fuel pump that pressurizes fuel discharged from the feed pump and supplies the fuel to the fuel injection valve is as follows. It has been found by the inventor that serious problems arise. That is, in a predetermined operating region of the internal combustion engine in which fuel injection control is performed, the check valve is closed when the feed pump is driven by the pulsation of the fuel pressure generated downstream of the check valve, and as a result, the fuel to the fuel injection valve is closed. This is a problem that inconvenience may occur in the supply.

  The present invention, in a fuel supply system including a high-pressure fuel pump, occurs downstream of the check valve without providing a member that always allows the backflow of fuel downstream of the check valve over a period during which the feed pump is driven. This suitably suppresses the check valve from closing due to pulsation.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
Technical idea 1: an internal combustion engine, a fuel tank that stores fuel supplied to the internal combustion engine, a feed pump that sucks and discharges fuel from the fuel tank, and a fuel that is pressurized by fuel discharged from the feed pump A high-pressure fuel pump for supplying to the injection valve, and is provided between the high-pressure fuel pump and the feed pump, and is provided between the high-pressure fuel pump and the downstream fuel pressure. A check valve that opens when the differential pressure of the fuel pressure on the upstream side, which is the feed pump side, exceeds a specified pressure, and the check valve is bypassed on condition that a predetermined condition is satisfied. A permissible portion that allows a backflow of fuel from the downstream side to the fuel filling location before flowing into the downstream side, and the predetermined condition is that the backflow is not allowed by the permissible portion The fuel supply apparatus for an internal combustion engine is a condition in which the to constant check valve is a possibility of closing.

  In the above apparatus, when it is assumed that the backflow is not permitted by the permissible portion, the backflow is permitted by the permissible portion when the check valve may be closed. Accordingly, it is preferable that the check valve is closed by at least one of the following actions without providing a member that always allows the back flow of the fuel downstream of the check valve over a period during which the feed pump is driven. Can be suppressed. The first effect is that the force caused by the pulsation applied to the check valve can be reduced because the pulsation of the fuel pressure is released to the fuel filling location before flowing into the downstream side by the permissible portion. The second function is a system in which the amount of fuel consumed on the downstream side of the check valve increases and the flow rate passing through the check valve increases, and the lift amount of the check valve has a positive correlation with the flow rate. In the case of having the check valve, the amount of fuel consumption on the downstream side of the check valve increases due to the backflow, whereby the lift amount of the check valve increases, and as a result, the resistance to the pulsation of the check valve increases.

  Technical idea 2: The permissible portion bypasses the check valve and communicates the downstream side with the fuel filling portion before flowing into the downstream side, and the bypass passage communicates with the bypass passage. A fuel supply device for an internal combustion engine according to Technical Idea 1, comprising a switching valve that switches to a shut-off state.

  Technical idea 3: The feed pump increases the discharge amount as the amount of fuel injected from the fuel injection valve increases, and the predetermined condition defines the amount of fuel injected by the fuel injection valve. The fuel supply device for an internal combustion engine according to the technical idea 2, wherein the fuel supply device is a condition that is less than the amount.

  When the discharge amount of the feed pump is set according to the amount of fuel injected from the fuel injection valve, the check valve lift amount decreases when the injected fuel amount becomes small. Is easy to close. In view of this point, in the above device, when the amount of fuel to be injected is equal to or less than a specified amount, the lift amount of the check valve is increased by bringing the switching valve into a communication state, and thus the resistance of the check valve to pulsation is increased. To increase.

  Technical idea 4: The check valve includes a valve box connected to each of the upstream-side passage and the downstream-side passage, and a valve body, a valve seat, and the valve body housed in the valve box. A valve body seating member for seating on the valve seat; and a valve seat seating member for seating the valve seat on the valve box, wherein the valve seat is seated on the valve box, and the valve body is By sitting on the valve seat, the space in the valve box is divided into a space connected to the downstream passage and a space connected to the upstream passage, and the permitting portion includes the valve seat, the valve A passage having a seating member for seating and the valve box, and allowing the reverse flow of fuel from the downstream side to the upstream side by bypassing the check valve by separating the valve seat from the valve box 2. A fuel supply device for an internal combustion engine according to the technical idea 1 in which is formed.

  Technical idea 5: The force that the seat member for valve seat exerts on the valve seat is the force exerted on the valve seat by the upstream fuel and the seat member for valve seat when the predetermined condition is satisfied. The force exerted on the valve seat by the downstream fuel is larger than the resultant force with the force exerted on the valve seat, and the valve seat is adjusted to be separated from the valve box, and the predetermined condition In the state where the valve seat is seated on the valve box and the valve body is separated from the valve seat, the force exerted by the downstream fuel on the valve body and the valve body are seated on the valve seat. A technique in which a value obtained by subtracting the resultant force of the valve body seating member on the valve body from the force exerted on the valve body by the upstream fuel is equal to or less than a predetermined value greater than zero A fuel supply device for an internal combustion engine according to the fourth aspect.

  If the subtracted value is less than or equal to zero, the check valve can be kept closed. Therefore, in the above device, when the subtracted value is equal to or less than a predetermined value larger than zero, the reverse flow is allowed so that the valve seat is separated from the valve box. Thus, before the check valve is closed due to the force exerted on the valve body by the fuel on the downstream side, the valve seat can be separated from the valve box to allow the reverse flow. And if the said backflow is accept | permitted, the force which the fuel of a downstream side exerts on a valve body will be reduced. Thereby, it can suppress suitably that a non-return valve closes.

Technical idea 6: The fuel supply device for an internal combustion engine according to technical idea 2 or 3, wherein the switching valve is of an electronic control type.
Technical idea 7: The internal combustion engine includes an intake throttle valve in an intake passage, and the switching valve opens and closes using the pressure in the intake passage, and the pressure is low. 4. A fuel supply device for an internal combustion engine according to technical idea 2 or 3, wherein the valve is opened.

The figure which shows the structure of the fuel supply system concerning 1st Embodiment. (A) And (b) is a figure which shows the relationship between opening / closing of the switching valve concerning the same embodiment, and the lift amount of a valve body. (A)-(c) is a time chart which shows control of a switching valve. The figure which shows the structure of the fuel supply system concerning 2nd Embodiment. The figure which shows the structure of the switching valve concerning the embodiment. (A)-(c) is sectional drawing which shows the structure of the non-return valve concerning 3rd Embodiment.

<First Embodiment>
A first embodiment of a fuel supply device for an internal combustion engine will be described below with reference to the drawings.

  An internal combustion engine 10 shown in FIG. 1 includes an intake throttle valve 13 in an intake passage 12, a passage-side injection valve 14 that injects fuel into the intake passage 12, and an in-cylinder injection valve 18 that directly injects fuel into a combustion chamber 16. Yes.

  On the other hand, the fuel tank 20 is filled with gasoline fuel. The fuel tank 20 is connected to a low-pressure fuel passage 22 that is a passage for supplying fuel filled in the fuel tank 20 to the internal combustion engine 10. A low pressure side delivery pipe 48 that supplies fuel to the passage side injection valve 14 is connected to the low pressure fuel passage 22.

  A branch passage 24 is connected to the low pressure fuel passage 22. The branch passage 24 is provided with a high-pressure fuel pump 30 that sucks, pressurizes, and discharges fuel flowing into the branch passage 24. The high-pressure fuel pump 30 is an engine-driven pump that is driven using the power of the crankshaft 42 of the internal combustion engine 10. Specifically, the high-pressure fuel pump 30 includes a plunger 38 that repeats reciprocation in the cylinder 36 in accordance with the rotation of the camshaft 40 that rotates with the rotation of the crankshaft 42. A pressurizing chamber 34 that is a space defined by the cylinder 36 and the plunger 38 is connected to the branch passage 24 via the electromagnetic valve 32. Then, when the volume of the pressurizing chamber 34 is increased in a state where the electromagnetic valve 32 is opened, the fuel in the branch passage 24 is sucked into the pressurizing chamber 34. When the volume in the pressurizing chamber 34 is reduced, the fuel in the pressurizing chamber 34 is pressurized and discharged into the high-pressure fuel passage 44 by closing the electromagnetic valve 32. Here, the fuel discharge amount is adjusted by the closing timing of the electromagnetic valve 32. Specifically, as the valve closing timing of the electromagnetic valve 32 is delayed, the amount of fuel returned from the pressurizing chamber 34 to the branch passage 24 increases, and the discharge amount decreases.

The high pressure fuel passage 44 is connected to a high pressure side delivery pipe 46 that supplies fuel to the in-cylinder injection valve 18.
The fuel tank 20 is provided with an electronically controlled feed pump 50 that pumps up and discharges fuel in the fuel tank 20. Specifically, the feed pump 50 pumps up the fuel in the suction container 51 in the fuel tank 20. A check valve 52 is provided at the fuel discharge port of the feed pump 50, and the downstream of the check valve 52 is connected to a discharge passage 56 via a filter 54. The discharge passage 56 is connected to the low pressure fuel passage 22 via a check valve 58. Here, the check valve 58 is opened when the differential pressure between the pressure of fuel on the upstream side (discharge passage 56 side) and the pressure of fuel on the downstream side (low pressure fuel passage 22 side) becomes equal to or higher than a specified pressure.

  A relief valve 82 is connected to the low pressure fuel passage 22. The relief valve 82 is opened when the pressure of the low-pressure fuel passage 22 becomes equal to or higher than the guard pressure, and allows the low-pressure fuel passage 22 to communicate with the fuel tank 20.

  The discharge passage 56 is provided with a branch passage 60, and the branch passage 60 is connected to a residual pressure holding valve 62. The residual pressure holding valve 62 is opened when the pressure exceeds a predetermined pressure lower than the guard pressure. In the present embodiment, in particular, the predetermined pressure is set so that the residual pressure holding valve 62 is opened during the period in which the feed pump 50 discharges the fuel to supply the fuel to the internal combustion engine 10. ing.

  A return passage 64 for returning the fuel pumped up by the feed pump 50 to the suction container 51 is connected downstream of the residual pressure holding valve 62. Jet pumps 66 and 68 are connected to the return passage 64. For this reason, during the period in which the feed pump 50 discharges fuel to supply fuel to the internal combustion engine 10, the residual pressure holding valve 62 is opened, and the fuel that has flowed into the branch passage 60 is sucked through the return passage 64. Returned to the container 51. As a result, when the remaining amount of fuel in the fuel tank 20 is small, a negative pressure is generated in the vicinity of the jet pump 66, so the fuel in the vicinity of the jet pump 66 is sucked and sucked into the suction container 51 side. On the other hand, a communication passage 70 is connected in the vicinity of the jet pump 68. Therefore, when the remaining amount of fuel in the fuel tank 20 is small, a negative pressure is generated in the vicinity of the jet pump 68 when the fuel is returned to the suction container 51 via the return passage 64. The communication passage 70 is connected to a filter 72 disposed at a position away from the feed pump 50 in the fuel tank 20. For this reason, when a negative pressure is generated in the vicinity of the jet pump 68, the fuel at a position separated from the feed pump 50 is sucked into the communication passage 70 through the filter 72 and eventually merges with the fuel flowing out from the return passage 64. It flows into the suction container 51.

As described above, the residual pressure holding valve 62, the return passage 64, and the jet pumps 66 and 68 have a function of collecting the fuel in the fuel tank 20 in the suction container 51.
The ECU 90 is an electronic control device that electronically operates the electromagnetic valve 32, the passage side injection valve 14, the in-cylinder injection valve 18, and the feed pump 50. In particular, the ECU 90 operates the electromagnetic valve 32 of the high-pressure fuel pump 30 by an operation amount for feedback-controlling the fuel pressure PH in the high-pressure side delivery pipe 46 detected by the high-pressure side fuel pressure sensor 92 to the target value. Further, the ECU 90 controls the fuel pressure in the low pressure side delivery pipe 48 to a target value, and performs control to variably set the target value. Here, the target value is set to a low value in the low load region and set to a high value in the high load region.

  The operation amount of the feed pump 50 for controlling the fuel pressure in the low pressure side delivery pipe 48 to a target value is an open loop operation amount and a closed loop operation amount for controlling the fuel pressure in the low pressure side delivery pipe 48 to a target value, This is the sum of the open loop manipulated variable for controlling the fuel pressure in the high pressure side delivery pipe 46 to the target value. The closed loop operation amount is an operation amount for performing feedback control of the fuel pressure PL in the low pressure delivery pipe 48 detected by the low pressure fuel pressure sensor 94 to a target value. The open loop operation amount is set according to the fuel injection amount by the passage side injection valve 14 and the fuel injection amount by the in-cylinder injection valve 18. As a result, the amount of fuel discharged from the feed pump 50 increases as the fuel injection amount increases. In addition, as an operation amount of the feed pump 50, a rotation speed is illustrated below.

  The fuel pressure in the low-pressure fuel passage 22 becomes a target value of the fuel pressure in the low-pressure delivery pipe 48 except for pulsation and pressure loss. For this reason, in order to maintain high controllability of the fuel pressure in the low pressure delivery pipe 48, the guard pressure at which the relief valve 82 opens is set higher than the target value of the fuel pressure in the low pressure delivery pipe 48. There is a need.

  In order to open the residual pressure holding valve 62 when fuel is being supplied by the feed pump 50, the predetermined pressure for opening the residual pressure holding valve 62 is set to the low pressure delivery pipe 48. The fuel pressure must be lower than the target value.

  Here, in this embodiment, the guard pressure is set to “500 kPa or more”, desirably “500 to 700 kPa”, more desirably “550 to 700 kPa”, and the predetermined pressure is “250 kPa or less”, desirably “250”. ˜150 kPa ”, more preferably“ 200 ˜150 kPa ”.

  The check valve 58 is provided in association with variably setting the target value of the fuel pressure in the low pressure side delivery pipe 48. That is, in the case of the above configuration, when the feed pump 50 is stopped, the residual pressure holding valve 62 is also closed. Here, when the check valve 58 is not provided, the fuel pressure in the low-pressure fuel passage 22 is reduced to about the predetermined pressure that opens the residual pressure holding valve 62. In this case, as described above, the predetermined pressure cannot be increased due to variably setting the target value of the fuel pressure in the low-pressure delivery pipe 48, so that the vapor pressure of the fuel decreases. For this reason, we are anxious about vapor generating during dead soak. On the other hand, by providing the check valve 58, the fuel pressure in the low pressure fuel passage 22 can be maintained at a value higher than the predetermined pressure, so that the generation of vapor can be suppressed.

  By the way, when the high-pressure fuel pump 30 is provided, the high-pressure fuel pump 30 sucks fuel from the branch passage 24 or discharges the sucked fuel to the branch passage 24, thereby causing fuel pressure pulsation in the low-pressure fuel passage 22. Arise. In particular, during a period when the amount of fuel injected by the in-cylinder injection valve 18 is small, most of the fuel once sucked into the pressurizing chamber 34 is discharged into the branch passage 24, so that the pulsation of the fuel pressure becomes significant.

  Here, when pulsation of fuel pressure occurs in the high-pressure fuel pump 30, the check valve 58 is closed due to the fact that the pressure on the downstream side of the check valve 58 becomes higher than the pressure on the upstream side. There is a risk that the controllability of the system will be reduced. That is, when the check valve 58 is closed, the relationship between the rotation speed of the feed pump 50 and the discharge amount is lost, so that depending on the rotation speed of the feed pump 50 set by the ECU 90 to control the discharge amount of the feed pump 50. The target discharge amount will not be achieved.

  The phenomenon that the check valve 58 closes is particularly caused by the fact that the guard pressure for opening the relief valve 82 needs to be higher than the target value of the fuel pressure in the low-pressure delivery pipe 48 that is variably set. It tends to occur. This is because it becomes difficult to release the energy of the pulsation of the fuel pressure to the fuel tank 20 side by opening the relief valve 82. Note that when the check valve 58 is closed, the check valve 58 becomes a fixed end of the pulsation of the fuel pressure, so that a resonance phenomenon occurs, which may cause problems of sound and vibration due to the pulsation. That is, resonance occurs when the phase of the fuel pressure pulsation caused by the intake and discharge of fuel from the high-pressure fuel pump 30 and the reflected wave at the check valve 58 of the fuel pressure pulsation coincide. When resonance occurs, the pulsation of the fuel pressure at that time may cause a problem of sound and vibration.

  In the present embodiment, the resonance phenomenon occurs when the check valve 58 is closed during the idling operation of the internal combustion engine 10. Incidentally, during idle operation, fuel is not injected from the in-cylinder injection valve 18, but fuel is injected only by the passage-side injection valve 14, and therefore overlaps with a period in which the pulsation of the fuel pressure by the high-pressure fuel pump 30 becomes particularly large.

  Therefore, in the present embodiment, a bypass passage 84 is provided on the downstream side of the check valve 58, and an electronically controlled switching valve 86 that switches the bypass passage 84 between a communication state and a cutoff state is provided. Here, one end of the bypass passage 84 is connected to the low-pressure fuel passage 22 which is a passage on the downstream side of the check valve 58, and the other end is sucked into the feed pump 50 the fuel flowing into the downstream side of the check valve 58. It is open to the previous filling location. More specifically, the bypass passage 84 is used to directly join the fuel in the low-pressure fuel passage 22 into the suction container 51 instead of returning it to the discharge passage 56 or the like.

  The switching valve 86 is opened and closed by the ECU 90. In particular, in the present embodiment, the switching valve 86 is opened when the fuel injection amount of the internal combustion engine 10 is small. This is in view of the fact that the check valve 58 is likely to close due to the pulsation of the fuel pressure resulting from the intake and discharge of fuel by the high-pressure fuel pump 30 when the fuel injection amount is small. Hereinafter, this will be described with reference to FIG.

  In FIG. 2, the check valve 58 is simply described as including a valve seat 58a, a valve body 58b, a spring 58c, and a fixed end 58d. Here, the fixed end 58d fixes one end of the spring 58c. Moreover, the spring 58c is for exerting the force which seats on the valve seat 58a on the valve body 58b. The spring 58c determines the upstream differential pressure (the specified pressure) with respect to the downstream side where the check valve 58 opens together with the dimensions of the valve body 58b and the shape of the valve seat 58a. The lift amount of the check valve 58 is determined by the amount of displacement of the valve body 58b from the state where the valve body 58b is seated on the valve seat 58a. The lift amount increases as the value obtained by subtracting the force exerted by the downstream fuel on the valve body 58b from the force exerted by the upstream fuel on the valve body 58b increases. This is because the lift amount increases until the subtracted value is balanced with the elastic force of the spring 58c.

  Here, the feed pump 50 is controlled so as to discharge the necessary fuel according to the fuel consumption of the internal combustion engine 10, so that when the fuel injection amount is small, the feed pump 50 flows through the discharge passage 56 and the low-pressure fuel passage 22. The amount of fuel to be used is small. For this reason, when the fuel injection amount is small, the lift amount of the check valve 58 becomes smaller than when the fuel injection amount is large. When the lift amount of the check valve 58 is reduced, the resistance due to the pulsation of the fuel pressure is reduced, and as a result, the check valve 58 is easily closed by the pulsation.

  FIG. 2A shows a case where the switching valve 86 is in a closed state. In this case, since the fuel is not returned to the suction container 51 via the bypass passage 84, the flow rate flowing through the discharge passage 56 and the flow rate flowing through the low-pressure fuel passage 22 are both the flow rate Q1. On the other hand, FIG. 2B shows a case where the switching valve 86 is in the open state. In this case, since the fuel is returned to the suction container 51 through the bypass passage 84, the flow rate Qt flowing through the discharge passage 56 is equal to the flow rate Q1 flowing through the low-pressure fuel passage 22 and the flow rate Q2 flowing through the bypass passage 84. The sum of Accordingly, when the flow rate Q1 flowing through the low pressure fuel passage 22 is the same, the flow rate Qt of the discharge passage 56 when the switching valve 86 is in the open state is higher than the flow rate of the discharge passage 56 when the switching valve 86 is in the closed state. More than Q1. Therefore, by opening the switching valve 86 when the fuel injection amount is small, the flow rate of the discharge passage 56 can be increased, and as a result, the lift amount of the valve body 58b of the check valve 58 is increased. Resistance to pulsation can be increased.

Next, the effect | action of this embodiment is demonstrated using FIG.
3A shows the transition of the command value Q * of the fuel injection amount, FIG. 3B shows the transition of the open / close state of the switching valve 86, and FIG. 3C shows the check valve 58. The transition of the open / close state is shown.

  As shown in the drawing, the ECU 90 opens the switching valve 86 when the command value Q * becomes equal to or less than the specified value Qth. Here, the prescribed value Qth is set to a value that is equal to or greater than the fuel injection amount during idle operation and smaller than the injection amount during high-load operation of the internal combustion engine 10. The ECU 90 calculates an operation amount of the feed pump 50 that is appropriate for controlling the fuel pressure in the low-pressure delivery pipe 48 to a target value, and outputs an operation signal MS to the feed pump 50, thereby Manipulate the discharge rate. In this case, the discharge amount of the feed pump 50 is increased compared to the case where it is assumed that the switching valve 86 is closed. Therefore, the lift amount of the check valve 58 is increased as compared with the case where it is assumed that the switching valve 86 is in the closed state, and the resistance of the check valve 58 to the pulsation of the fuel pressure is improved.

  Incidentally, it is confirmed by the following experiment conducted without providing the bypass passage 84 that the resistance of the check valve 58 is improved against the pulsation of the fuel pressure by increasing the flow rate of the fuel. That is, this is an experiment in which the discharge amount of the feed pump 50 is gradually increased by gradually changing the air-fuel ratio to a richer side than the target air-fuel ratio while keeping the rotation speed of the internal combustion engine 10 constant during idle operation. . In this experiment, the fuel was injected only from the passage side injection valve 14 without performing the fuel injection by the in-cylinder injection valve 18. As a result, it has been confirmed that the situation where the check valve 58 is closed or the pulsation is amplified by resonance is eliminated.

However, in this embodiment, since a part of the pulsation energy of the fuel pressure is released through the bypass passage 84, the effect of reducing the pulsation force applied to the check valve 58 is also produced.
According to the present embodiment described above, the following effects can be obtained.

  (1) The bypass passage 84 and the switching valve 86 are provided, and when the check valve 58 may be closed, the switching valve 86 is opened so that the fuel that has flowed into the downstream side of the check valve 58 flows downstream. It was made to flow backward to the fuel filling point before flowing into the side. Accordingly, the check valve 58 is closed by the pulsation of the fuel pressure caused by the intake and discharge of the fuel of the high-pressure fuel pump 30 without providing a member that always allows the back flow of the fuel downstream of the check valve 58. Can be suppressed.

  (2) The opening operation condition of the switching valve 86 is a condition that the command value Q * of the fuel injection amount is equal to or less than the specified amount Qth. As a result, even when the switching valve 86 is closed, the switching valve 86 is not opened when there is a low possibility that the check valve 58 is closed, so that the discharge amount of the feed pump 50 is controlled by the internal combustion engine 10. The amount exceeding the fuel consumption can be reduced as much as possible.

<Second Embodiment>
Hereinafter, a second embodiment of a fuel supply device for an internal combustion engine will be described with reference to the drawings, focusing on differences from the first embodiment.

FIG. 4 shows the configuration of the fuel supply system according to this embodiment. In FIG. 4, members corresponding to the members shown in FIG.
In the present embodiment, the bypass passage 84 is provided with a switching valve 87 that opens and closes using the pressure in the intake passage 12. Here, the switching valve 87 is opened when the pressure in the intake passage 12 is low. That is, the switching valve 87 is connected to a portion of the intake passage 12 on the downstream side of the intake throttle valve 13 via the communication passage 100, thereby mechanically opening and closing using the pressure in the intake passage 12. To do.

FIG. 5 shows the configuration of the switching valve 87.
As shown in the figure, the switching valve 87 is connected to the valve body 87a that blocks the bypass passage 84, the atmosphere opening chamber 87b that applies a force in the valve opening direction to the valve body 87a, and the communication passage 100 to be connected to the valve body 87a. Are provided with a negative pressure generating chamber 87c for applying a force in the valve closing direction to the valve body 87 and a spring 87d for applying a force in the valve closing direction to the valve body 87a. Here, since the atmosphere release chamber 87b is open to the atmosphere, the atmospheric pressure in the atmosphere release chamber 87b is equal to the external pressure. On the other hand, since the negative pressure generation chamber 87c is connected to the communication passage 100, the negative pressure generation chamber 87c can be reduced to the pressure in the intake passage 12 with respect to the external air pressure. For this reason, when the opening degree of the intake throttle valve 13 becomes small, the atmospheric pressure in the negative pressure generation chamber 87c greatly decreases with respect to the atmospheric pressure in the atmosphere release chamber 87b. Thereby, the force in which the gas in the air release chamber 87b pushes the valve body 87a in the valve opening direction is larger than the force in which the gas in the negative pressure generation chamber 87c and the spring 87d push the valve body 87a in the valve closing direction. As a result, the valve body 87a is opened.

  Even in such a configuration, the switching valve 87 can be closed when the fuel injection amount is small. That is, the ECU 90 adjusts the amount of air taken into the combustion chamber 16 of each cylinder by adjusting the flow passage area of the intake passage 12 by the intake throttle valve 13. Then, the ECU 90 operates the fuel injection amount in order to control the air-fuel ratio of the air-fuel mixture in the combustion chamber 16 to the target air-fuel ratio in accordance with the air amount. For this reason, the air amount and the fuel injection amount have a positive correlation, and if the air amount is small, the fuel injection amount is also small.

According to the present embodiment described above, the following effects can be obtained in addition to the effects according to the above (1) and (2) of the first embodiment.
(3) The displacement direction of the valve body 87a of the switching valve 87 is orthogonal to the axial direction of the bypass passage 84 in the portion of the bypass passage 84 in which the switching valve 87 is accommodated. As a result, the force exerted on the valve body 87a by the fuel upstream of the bypass passage 84 (upper side in the drawing) than the switching valve 87 is orthogonal to the displacement direction of the valve body 87a. For this reason, the influence which the fuel of the upstream of the bypass path 84 rather than the switching valve 87 has on opening / closing of the valve body 87a can be reduced.

<Third Embodiment>
Hereinafter, a third embodiment of a fuel supply device for an internal combustion engine will be described with reference to the drawings, centering on differences from the first embodiment.

In the present embodiment, the function of the check valve 58 and the functions of the bypass passage 84 and the switching valve 86 are integrated.
FIG. 6A shows a cross-sectional configuration of a valve connected between the discharge passage 56 and the low-pressure fuel passage 22. As illustrated, the valve box 110 defines an internal space by a downstream side wall surface 110a, a cylindrical side wall 110b, and an upstream side wall surface 110c. A check valve 58 including a valve seat 112, a valve body 114, a spring 116, and a fixing portion 118 is accommodated in the internal space. A force for seating on the downstream side wall surface 110a is applied to the valve seat 112 by a spring 120 having one end fixed to the upstream side wall surface 110c. A force for seating on the valve seat 112 is applied to the valve body 114 by a spring 116 whose one end is fixed to the fixing portion 118. Note that the fixing portion 118 may be a member connected to the valve seat 112.

  In the state where the valve seat 112 is seated on the downstream side wall surface 110a as shown in FIG. 6A, when the valve body 114 is seated on the valve seat 112, the low pressure fuel passage 22 is formed by the valve seat 112 and the valve body 114. The discharge passage 56 is blocked. This is a state equivalent to the closed state of the check valve 58 of FIG. This state is realized when the feed pump 50 is stopped.

  FIG. 6B shows a state where the check valve 58 is opened. Here, the force F1 that the upstream fuel exerts on the valve body 114 is balanced with the resultant force of the force F2 that the downstream fuel exerts on the valve body 114 and the force F3 that the spring 116 exerts on the valve body 114, and “F1 = When the relationship of “F2 + F3” is established, the lift amount of the valve body 114 is determined. The valve body 114 is separated from the valve seat 112 because the force F3 exerted on the valve body 114 by the spring 116 and the downstream fuel are applied to the valve body 114 when the valve body 114 is seated on the valve seat 112. This is when the force F1 exerted on the valve body 114 by the upstream fuel is larger than the resultant force exerted by the force F2. And "F1-F2" at this time determines the differential pressure (the above-mentioned specified pressure) for opening the check valve 58.

  FIG. 6C shows a state in which the valve seat 112 is separated from the downstream side wall surface 110 a of the valve box 110. This is a state caused by the pulsation of the fuel pressure from the low pressure fuel passage 22. Here, in the present embodiment, the upstream fuel is the combined force of the force F2 exerted by the downstream fuel on the valve body 114 and the force exerted on the valve body 114 by the spring 116 when the check valve 58 is closed. The valve seat 112 is set to be separated from the valve box 110 on condition that the value subtracted from the force F1 exerted on the pressure is equal to or less than a predetermined value α (> 0). The valve seat 112 moves away from the valve box 110 because the force F5 exerted on the valve seat 112 by the downstream fuel, the force F4 exerted on the valve seat 112 by the upstream fuel, and the valve seat 112 on the valve box 110. This is when the spring 120 becomes larger than the resultant force with the force F6 exerted on the valve seat 112 in the seated state.

  This setting can be realized by adjusting the elastic constant of the spring 120. However, as adjustment elements for realizing this setting, in addition to the elastic constant of the spring 120, the shape and dimensions of the valve seat 112, the shape and dimensions of the valve body 114, the elastic constant of the spring 116, the valve body 114 and the valve seat 112 There is an angle between the displacement direction and the vertical direction.

  The predetermined value α (> 0) is as small as possible so that the valve seat 112 does not frequently separate from the valve box 110 until there is no risk of the check valve 58 closing. It is desirable.

Here, the operation of the present embodiment will be described.
When the feed pump 50 is driven, the check valve 58 is opened as shown in FIG. Thereafter, when the pulsation of the fuel pressure in the low pressure fuel passage 22 increases, the force F5 exerted on the valve seat 112 by the downstream fuel increases in addition to the force F2 exerted on the valve body 114 by the downstream fuel. Then, before the check valve 58 is closed, the valve seat 112 is separated from the valve box 110. As a result, the low pressure fuel passage 22 and the discharge passage 56 are communicated not only by the passage due to the opening of the check valve 58 but also by a portion of the space in the valve box 110 that bypasses the check valve 58. The That is, communication is also established by a space excluding the check valve 58 among spaces defined by the valve box 110 (downstream side wall surface 110a, side wall 110b, and upstream side wall surface 110c). For this reason, the force F2 exerted on the valve body 114 by the pulsation of the fuel pressure is reduced, and the closing of the check valve 58 is suppressed.

<Correspondence between technical idea and embodiment>
Hereinafter, a representative correspondence relationship between the technical idea described in the above “Means for Solving the Problems” and the embodiment will be described.

[Technical Thought 1: Specified Pressure ... Pressure that Generates Force that 58c Overcomes Force for Sitting 58a; Pressure that Generates Force that 116 Overtakes Force to Sit 114 to 112, "Predetermined Condition" ... In FIG. Condition where Q * is equal to or less than Qth; condition where F1-F2-F3 is equal to or less than α in FIG. 6 (F3 is a value when the valve element 114 is seated on the valve seat 112), “before flowing into the downstream side” 1 in FIG. 1; 56 in FIG. 6; permissible portions 84, 86; 84, 87; 110-118] [Technical Thought 2: FIGS. 1 and 3] [Technical Thought 3: FIG. 3] [Technical idea 4: Seat member for valve body ... 116, Seat member for valve seat ... 120, "Divided into a space connected to the downstream passage and a space connected to the upstream passage" ... FIG. a) “Allowable passage is formed” (FIG. 6C) [Technical Thought 5] FIG 6 (c)] [technical idea 6: 1] [technical idea 7: 4]
<Other embodiments>
Each of the above embodiments may be modified as follows.

・ About the switching valve
The electronically controlled valve body is not limited to one operated by the ECU 90. For example, the operation signal MS output from the ECU 90 to the feed pump 50 and the operation signal MS output to the passage side injection valve 14 or the in-cylinder injection valve 18 are input, and the switching valve is turned on when the injection amount is less than a specified amount. You may provide the hardware for exclusive use with only the function to open. Instead of this, dedicated hardware having only the function of opening the switching valve when the detected value of the flow rate of the fuel in the low-pressure fuel passage 22 is input and the flow rate is equal to or less than the specified amount is provided. Also good.

For example, the ECU 90 may open the switching valve 86 when the opening degree of the intake throttle valve 13 is equal to or less than a predetermined threshold value.
The valve element 87 a that opens and closes using the pressure in the intake passage 12 is not limited to one whose displacement direction is orthogonal to the axial direction of the bypass passage 84. For example, the displacement direction may obliquely intersect the axial direction.

・ "Check valve"
In FIG. 2, the elastic member that exerts a force to seat the valve body 58b on the valve seat 58a is not limited to the spring 58c. For example, rubber may be used. The elastic member is not limited to one whose elastic force increases in proportion to the amount of displacement. For example, the force that displaces the valve body 58b toward the valve seat 58a may be constant regardless of the lift amount. In this case, when the check valve is open, the lift amount of the check valve can be constant regardless of the injection amount. However, even in this case, according to the first embodiment, since a part of the energy of the fuel pressure pulsation can be released by the bypass passage 84, the check valve 58 is prevented from closing. I think it can be done.

  Similarly, in FIG. 6, the elastic member that exerts a force to seat the valve body 114 on the valve seat 112 is not limited to the spring 116. In FIG. 6, the elastic member that exerts a force to seat the valve seat 112 on the valve box 110 is not limited to the spring 120.

・ "About detour passage"
The downstream side of the bypass passage 84 is not limited to being opened to the suction container 51. For example, the space inside the fuel tank 20 may be opened outside the suction container 51. Further, for example, it may be connected to the discharge passage 56. Further, for example, it may be connected to the return passage 64.

  Further, the upstream side of the bypass passage 84 is not limited to the one connected to the downstream side of the portion of the low pressure fuel passage 22 connected to the relief valve 82. For example, it may be connected to the upstream side.

·"others"
In the above embodiment, when it is assumed that the check valve 58 is closed, it is assumed that the period during which the resonance phenomenon occurs is during idling, but this is not a limitation. For example, the resonance phenomenon may occur when the rotation speed of the crankshaft 42 is a predetermined rotation speed higher than that during idle operation. In this case, when it is assumed that the check valve 58 is closed, during the period in which the resonance phenomenon occurs, the check valve 58 does not actually close because the check valve 58 is lifted so that the resonance phenomenon occurs. It may not occur. However, even in this case, in order to prevent the check valve 58 from closing due to the pulsation of the fuel pressure when the lift amount of the check valve 58 is small, it is effective to provide a bypass passage 84 or the like. .

  The passage side injection valve 14 may not be provided. Even in this case, when the discharge amount of the feed pump 50 is changed according to the amount of fuel injected by the in-cylinder injection valve 18, the check valve 58 becomes a low lift amount during idling, so that the bypass passage 84 It is effective to provide a method.

  It is not essential to provide the residual pressure holding valve 62. Even if this is not provided, if a check valve is provided on the downstream side of the feed pump 50 for some reason, if this is closed by the pulsation of the fuel pressure, the controllability of the fuel supply amount will be reduced, so that detouring will occur. A technique such as providing a passage 84 is effective.

  The fuel is not limited to gasoline. Even if it is a fuel other than gasoline, if a check valve is provided on the downstream side of the feed pump 50, if the valve is closed due to the pulsation of the fuel pressure, the controllability of the fuel supply amount will be reduced, so a bypass passage 84 is provided. Such a method is effective.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Intake passage, 13 ... Intake throttle valve, 14 ... Passage side injection valve, 16 ... Combustion chamber, 18 ... In-cylinder injection valve, 20 ... Fuel tank, 22 ... Low pressure fuel passage, 24 ... Branch passage 30 ... High pressure fuel pump, 32 ... Solenoid valve, 34 ... Pressure chamber, 36 ... Cylinder, 38 ... Plunger, 40 ... Camshaft, 42 ... Crankshaft, 44 ... High pressure fuel passage, 46 ... High pressure side delivery pipe, 48 ... low pressure side delivery pipe, 50 ... feed pump, 51 ... suction container, 52 ... check valve, 54 ... filter, 56 ... discharge passage, 58 ... check valve, 58a ... valve seat, 58b ... valve body, 58c ... Spring, 58d ... fixed end, 60 ... branch passage, 62 ... residual pressure holding valve, 64 ... return passage, 66, 68 ... jet pump, 70 ... communication passage, 72 ... filter, 82 ... relief valve, 84 ... detour Passage, 86, 87 ... switching valve, 87a ... valve body, 87b ... atmospheric release chamber, 87c ... negative pressure generating chamber, 87d ... spring, 90 ... ECU, 92 ... high pressure side fuel pressure sensor, 94 ... low pressure side fuel pressure sensor, 100 DESCRIPTION OF SYMBOLS Communication path, 110 ... Valve box, 110a ... Downstream side wall surface, 110b ... Side wall, 110c ... Upstream side wall surface, 112 ... Valve seat, 114 ... Valve body, 116 ... Spring, 118 ... Fixed part, 120 ... Spring.

Claims (5)

An internal combustion engine, a fuel tank that stores fuel supplied to the internal combustion engine, a feed pump that sucks and discharges fuel from the fuel tank, and pressurizes and discharges fuel discharged from the feed pump to a fuel injection valve A high-pressure fuel pump, and is applied to a fuel supply system for an internal combustion engine,
The differential pressure between the pressure of the upstream fuel on the feed pump side and the pressure of the downstream fuel on the high pressure fuel pump side, which is provided between the high pressure fuel pump and the feed pump, is equal to or higher than a specified pressure. A check valve that opens at
Provided that a predetermined condition is satisfied, and a permitting part that allows the back flow of fuel from the downstream side to the fuel filling point before flowing into the downstream side by bypassing the check valve,
The fuel supply device for an internal combustion engine, wherein the predetermined condition is a condition in which the check valve may be closed if the reverse flow is not allowed by the permission portion.   The permissible section bypasses the check valve and connects the downstream side and the fuel filling site before flowing into the downstream side, and switching for switching the bypass path between a communication state and a cutoff state The fuel supply device for an internal combustion engine according to claim 1, further comprising a valve. The feed pump increases the discharge amount as the amount of fuel injected from the fuel injection valve increases.
The fuel supply device for an internal combustion engine according to claim 2, wherein the predetermined condition is a condition that an amount of fuel injected by the fuel injection valve is a predetermined amount or less. The check valve includes a valve box connected to each of the upstream-side passage and the downstream-side passage, and a valve body, a valve seat, and the valve body housed in the valve box. A valve body seating member, and a valve seat seating member for seating the valve seat on the valve box,
When the valve seat is seated on the valve box and the valve body is seated on the valve seat, the space in the valve box is connected to the space connected to the downstream side passage and the upstream side passage. Divided into space and
The permissible portion includes the valve seat, the valve seat seating member, and the valve box, and the valve seat is separated from the valve box, thereby bypassing the check valve from the downstream side. 2. The fuel supply device for an internal combustion engine according to claim 1, wherein a passage is formed to allow the fuel to flow backward to the upstream side. The force that the seat member for valve seat exerts on the valve seat includes the force that the upstream fuel exerts on the valve seat and the force that the valve seat seat member exerts on the valve seat when the predetermined condition is satisfied. The force exerted on the valve seat by the fuel on the downstream side is larger than the resultant force with the valve seat, and the valve seat is adjusted so as to separate from the valve box,
The predetermined condition is that when the valve seat is seated on the valve box and the valve body is separated from the valve seat, the force exerted by the downstream fuel on the valve body and the valve body A value obtained by subtracting, from the force exerted by the upstream fuel on the valve body, the resultant force with the force exerted on the valve body by the valve body seating member at a position seated on the valve seat is less than a predetermined value greater than zero. The fuel supply device for an internal combustion engine according to claim 4, which is a condition.