JP6307307B2 - Fuel pump - Google Patents

Description

  The present invention relates to a high-pressure fuel pump, and more particularly to a high-pressure fuel pump having a function of avoiding cavitation that occurs at the front end of a seat surface on the inner peripheral side of a seat portion.

  Patent Document 1 discloses a relief passage that relieves high-pressure liquid from a high-pressure side to a low-pressure side, and includes a valve body and a seat portion that engages with the valve body to seat fuel, and the seat portion is formed with a thin structure. In the relief valve, an electromagnetic solenoid which is a forced opening means is provided in the relief valve, and the injection pressure can be lowered by releasing the fuel pressure of the common rail according to the operating state of the engine.

  Patent Document 2 discloses a relief passage that relieves high-pressure liquid from a high-pressure side to a low-pressure side, and includes a valve body and a seat portion that engages with the valve body to seat fuel, and the seat portion is separate from the main body. In the structure in which the seat portion is press-fitted into a hole dug into the main body, a slider is installed between the valve body and an elastic member that urges the valve body. By sliding in the valve opening direction along the sliding inner wall, the sliding path is restricted, stress applied to the axis of the elastic member is not applied, the relief valve lift is stabilized, and the spring durability Can be improved.

JP-A-10-281036 JP2012-158987

  The conventional techniques so far have the following problems.

  The relief valve of the high-pressure fuel pump has a function of suppressing the occurrence of abnormal pressure where the discharge pressure becomes higher than the allowable value. Therefore, when the discharge pressure becomes higher than the set pressure, the valve body of the relief valve opens and the high pressure is released.

  When the condition that the discharge pressure is less than the allowable value is satisfied, the valve body needs to be seated on the seat portion to completely seal the fuel.

  Here, when the valve element opens, the discharge pressure decreases, the valve element moves in the valve closing direction, and the valve element is seated on the seat part, the valve element closes with a strong force. A large impact is generated in the vicinity, and high-frequency vibration is generated.

  When high-frequency vibration is generated in the seat portion and the vicinity thereof, cavitation bubbles are generated at locations where the amplitude is large.

  When the cavitation bubbles are generated / collapsed in the vicinity of the seat portion, erosion is caused in the seat portion, and the sealing performance is hindered.

  In particular, when a portion formed with a sharp edge shape vibrates at a high speed, separation occurs due to minute vibrations at the edge portion, whereby the pressure is locally reduced, and cavitation bubbles are generated therefrom.

  When the sharp edge shape is in the vicinity of the seat part, particularly on the upstream side of the seat part, the cavitation bubbles are convected when the valve body is opened, and the cavitation occurs in the vicinity of the seating point of the valve body and the seat part. Bubbles collapse, and the impact force strikes the valve body and the surface of the seat, causing cavitation erosion.

When the cavitation erosion proceeds, a gap is generated between the valve body and the seat portion when the valve body is closed, causing a problem that fuel cannot be completely sealed.

In order to solve the above problem, in the relief valve of the fuel pump, in order to reduce the impact force when the valve body is seated on the seat portion, the seat portion is in a structure that allows elastic deformation, At the time of sitting, in order to suppress generation of cavitation bubbles at the front end of the seat surface on the inner peripheral side of the seat, the front end of the seat surface is formed in a curved shape.

  When the valve is seated, the seat portion vibrates at a high speed.However, since the tip end portion of the seat surface is formed in a curved shape, a high-frequency pressure pulsation occurs at the tip portion as compared with a sharp edge shape at the tip portion. It is suppressed.

  The curved shape at the front end of the sheet surface suppresses high-frequency pressure pulsation generated at the front end of the sheet surface, so that cavitation bubbles are not generated.

  A high-pressure fuel pump that pressurizes and sends liquid from a low-pressure side to a high-pressure side, and opens and closes in a relief passage that relieves high-pressure liquid from the high-pressure side to the low-pressure side due to a difference in pressure between the high-pressure side and the low-pressure side Body, an elastic member that urges the valve body, and a seat portion that engages with the valve body and seals fuel, and the seat portion is a seat portion that is elastically deformed when the valve body collides, and the seat portion Since the front end portion of the seat surface on the inner peripheral side has a curved shape, the occurrence of cavitation bubbles can be suppressed at the front end portion of the seat surface when the valve body collides with the seat portion.

  In the conventional structure, when the valve body is opened, the cavitation bubble convects near the seating portion of the valve body and the seat portion, where the cavitation bubble collapses and generates a large impact force, hitting the valve body and the seat portion surface. However, according to the present invention, the occurrence of the cavitation erosion can be suppressed.

Since the occurrence of the cavitation erosion can be suppressed, the fuel can be completely sealed when the valve body is seated on the seat portion.

Overall configuration of system 1 Overall system configuration 2 Cross section of relief mechanism 1 Enlarged view of the seat part 1 Enlarged view of the seat part 2 Enlarged view of the seat part 3 Cross section of relief mechanism 2 Enlarged view of the seat part 4 Formula showing fluid parameters Diagram showing the unitized relief mechanism FIG. 1 showing another relief mechanism Enlarged view of the seat part of another relief mechanism 1 FIG. 2 showing another relief mechanism Enlarged view of the seat part of another relief mechanism 2

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of a system for implementing the present invention. A portion surrounded by a broken line in FIG. 1 shows a pump housing 1 of a high-pressure fuel supply pump, and a mechanism and parts shown in the broken line are integrally incorporated therein.

  The fuel in the fuel tank 20 is pumped up by the feed pump 21 and sent to the fuel inlet 10a of the pump housing 1 through the suction pipe 28. The fuel that has passed through the fuel suction port 10a reaches the suction port 30a of the electromagnetic suction valve mechanism 30 constituting the variable capacity mechanism via the pressure pulsation reducing mechanism 9 and the suction passage 10c.

  The electromagnetic intake valve mechanism 30 includes an electromagnetic coil 30b, and in a state where the electromagnetic coil 30b is energized, the electromagnetic plunger 30c compresses the spring 33 and moves to the right in FIG. Maintained. At this time, the suction valve body 31 attached to the tip of the electromagnetic plunger 30c opens the suction port 32 leading to the pressurizing chamber 11 of the high-pressure fuel supply pump. When the electromagnetic coil 30b is not energized and there is no fluid differential pressure between the suction passage 10c (suction port 30a) and the pressurizing chamber 11, the suction valve element 31 is The suction port 32 is urged in the valve closing direction (leftward in FIG. 1) to be closed, and this state is maintained.

  When the plunger 2 is displaced downward in FIG. 1 due to the rotation of the cam of the internal combustion engine, which will be described later, and the intake chamber is in the intake process state, the volume of the pressurizing chamber 11 increases and the fuel pressure therein decreases. In this step, when the fuel pressure in the pressurizing chamber 11 becomes lower than the pressure in the suction passage 10c (suction port 30a), the suction valve body 31 has a valve opening force (suction valve body 31 shown by the fluid differential pressure). 1) is generated. By this valve opening force, the suction valve body 31 overcomes the biasing force of the spring 33 and opens, thereby opening the suction port 32. In this state, when a control signal from the ECU 27 is applied to the electromagnetic intake valve mechanism 30, an electric current flows through the electromagnetic coil 30b of the electromagnetic intake valve 30, and the electromagnetic plunger 30c further compresses the spring 33 by the magnetic biasing force. It moves to the right in FIG. 1 and keeps the inlet 32 open.

  When the plunger 2 moves from the suction process to the compression process (the rising process from the lower start point to the upper start point) while maintaining the input voltage applied to the electromagnetic intake valve mechanism 30, the energized state of the electromagnetic coil 30b is changed. Since it is maintained, the magnetic urging force is maintained, and the suction valve body 31 still maintains the opened state. The volume of the pressurizing chamber 11 decreases with the compression movement of the plunger 2, but in this state, the fuel once sucked into the pressurizing chamber 11 is once again in the opened valve body 31 and the suction port 32. The pressure in the pressurizing chamber 11 does not increase because the air is returned to the suction passage 10c (suction port 30a). This process is called a return process.

  In the returning process, when the energization of the electromagnetic coil 30b is cut off, the magnetic biasing force acting on the electromagnetic plunger 30c is erased after a certain time (after magnetic and mechanical delay time). Then, the suction valve body 31 is moved to the left in FIG. 1 by the urging force of the spring 33 constantly acting on the suction valve body 31 to close the suction port 32. When the suction port 32 is closed, the fuel pressure in the pressurizing chamber 11 rises with the rise of the plunger 2 from this time. Then, when the fuel pressure in the pressurizing chamber 11 exceeds a pressure larger than the fuel pressure of the discharge port 13 by a predetermined value, the fuel remaining in the pressurizing chamber 11 passes through the discharge valve mechanism 8, High pressure discharge is performed and supplied to the common rail 23. This process is called a discharge process. As described above, the compression process of the plunger 2 includes a return process and a discharge process.

  During the returning process, the pressure pulsation is generated in the suction passage due to the fuel returned to the suction passage 10c, but this pressure pulsation only slightly flows backward from the suction port 10a to the suction pipe 28. Most of the energy is absorbed by the pressure pulsation reducing mechanism 9.

  By controlling the timing of releasing the energization of the electromagnetic coil 30c of the electromagnetic intake valve mechanism 30, the amount of high-pressure fuel that is discharged can be controlled. If the timing of releasing the energization to the electromagnetic coil 30b is advanced, the ratio of the return process in the compression process is reduced and the ratio of the discharge process is increased. That is, the amount of fuel returned to the suction passage 10c (suction port 30a) is reduced and the amount of fuel discharged at high pressure is increased. On the other hand, if the timing of releasing the energization is delayed, the ratio of the return process in the compression process is increased and the ratio of the discharge process is decreased. That is, more fuel is returned to the suction passage 10c and less fuel is discharged at high pressure. The timing of releasing the energization is controlled by a command from the ECU.

  As described above, the ECU controls the timing of releasing the energization of the electromagnetic coil, whereby the amount of fuel discharged at high pressure can be set to the amount required by the internal combustion engine.

  In the pump housing 1, a discharge valve mechanism 8 is provided on the outlet side of the pressurizing chamber 11 between the discharge port (discharge side pipe connection portion) 13. The discharge valve mechanism 8 includes a seat member 8a, a discharge valve 8b, a discharge valve spring 8c, and a holding member (discharge valve stopper) 8d. In a state where there is no fuel differential pressure between the pressurizing chamber 11 and the discharge port 13, the discharge valve 8b is pressed against the seat member 8a by the urging force of the discharge valve spring 8c and is in a closed state. When the fuel pressure in the pressurizing chamber 11 exceeds a pressure larger than the fuel pressure in the discharge port 13 by a predetermined value, the discharge valve 8b opens against the discharge valve spring 8c, and the pressure chamber 11 The fuel is discharged to the common rail 23 through the discharge port 13.

  After the discharge valve 8b is opened, its operation is restricted when it comes into contact with the holding member 8d. Therefore, the stroke of the discharge valve 8b is appropriately determined by the holding member 8d. If the stroke is too large, the fuel discharged to the fuel discharge port 13 will flow back into the pressurizing chamber 11 again due to the delay in closing the discharge valve 8b, so the efficiency of the high-pressure pump will decrease. . Further, when the discharge valve 8b repeats opening and closing movements, the holding member 8d guides the discharge valve so that it moves only in the stroke direction. By configuring as described above, the discharge valve mechanism 8 becomes a check valve that restricts the flow direction of fuel.

  In this way, the fuel introduced to the fuel suction port 10a is pressurized to a high pressure by the reciprocating movement of the plunger 2 in the pressurizing chamber 11 of the pump body 1, and the fuel discharge port 13 passes through the discharge valve mechanism 8. Is fed by pressure to a common rail 23 which is a high-pressure pipe.

  An injector 24 and a pressure sensor 26 are attached to the common rail 23. The injectors 24 are mounted in accordance with the number of cylinders of the internal combustion engine, and the fuel is injected into the cylinders by operating the on-off valve according to a control signal from the ECU 27.

  Next, the fuel relief operation in the first embodiment when an abnormal high pressure occurs in the high pressure portion such as the common rail 23 due to a failure of the injector 24 or the like will be described.

  The pump housing 1 is provided with a relief passage 300 that connects the discharge passage 12 and the suction passage 10c. The relief passage 300 restricts the flow of fuel in only one direction from the discharge passage 12 to the suction passage 10c. A mechanism 200 is provided.

  Further, as shown in FIG. 2, the fuel flow in the relief passage 300 may flow from the discharge passage 12 into the pressurizing chamber 11 in some cases.

  FIG. 3 shows a cross section of the relief mechanism according to the first embodiment of the present invention. The relief valve mechanism 200 includes a valve body 201, a valve body presser 202 that presses the valve body, an elastic member 203 that urges the valve body, a seat portion 204 that engages with the valve body and seals fuel, a housing 205, an upstream of the valve body A high pressure chamber 206 on the side, and a low pressure chamber 207 on the downstream side of the valve body. The valve body 201 is urged against the seat portion 204 by the elastic member 203 against the high pressure guided from the discharge flow path 12.

  When the discharge flow path becomes abnormally high pressure and the pressure in the high pressure chamber 206 rises, the fluid force acting on the valve body exceeds the urging force of the elastic member 203, and the valve body 201 rises away from the seat portion 204, and the relief The passage is in communication. Further, when the pressure in the high pressure chamber 206 decreases again, the urging force of the elastic member 203 exceeds the fluid force acting on the valve body, and the valve body 201 descends and adheres to the seat portion 204.

  Here, the seat portion 204 has an elastic material or a thickness that can be elastically deformed in order to reduce an impact force when the valve body 201 collides with the seat portion 204. For example, by using a thin structure as shown in FIG. 3, the sheet portion 204 is elastically deformed at the time of collision, and the impact force at the time of collision can be reduced.

  In the conventional structure, the front end portion 208 of the sheet surface on the inner peripheral side of the sheet portion 204 is formed with a sharp edge shape. FIG. 4 shows an enlarged view of the sharp edge shape formed at the sheet surface front end portion 208 on the inner peripheral side of the sheet portion. The seat portion 204 has a structure that is elastically deformed, and when the valve body 201 collides, a high-speed vibration 209 in the vertical direction is generated in order to reduce an impact force when the valve body 201 collides.

  FIG. 5 shows a state where cavitation occurs at the front end 208 of the sheet surface. High-speed vibration 209 causes high-frequency pressure pulsation at the sheet surface front end 208, whereby the pressure locally decreases rapidly and cavitation bubbles 210 are generated.

  When the valve body 201 rises again due to the increase in fluid force, the cavitation bubble 210 convects near the contact position between the valve body 201 and the seat portion 204, where the cavitation bubble 210 collapses and a high impact force is generated. This impact force strikes the wall surface of the seat portion 204, where cavitation erosion occurs.

  FIG. 6 shows a detailed embodiment of this patent. By forming the sheet surface front end portion 208 with the smooth curved shape 211, the high-speed vibration 209 that has conventionally occurred at the edge portion is eliminated, and the generation of cavitation bubbles can be suppressed.

  FIG. 7 shows an embodiment of the present invention. In the relief mechanism described in the first embodiment, the seat portion 204 has an elastic material or a wall thickness that can be elastically deformed in order to reduce an impact force when the valve body 201 collides. Therefore, high stress concentration occurs at the branch portion between the seat portion 204 and the housing 205. In order to alleviate this stress concentration and reduce the stress generated at the branch portion, a chamfer 212 is provided at the branch portion.

  FIG. 8 shows an embodiment of the present invention. Cavitation occurs when the surrounding flow transitions to turbulent flow due to the high-speed vibration of the front end 208 of the sheet surface. A Reynolds number is a fluid parameter indicating the degree of turbulence of the flow, and is defined by Expression (1) shown in FIG. 9 using a representative length scale D, a representative speed U, and a kinematic viscosity coefficient ν. The minimum Reynolds number for transition to turbulent flow in this relief mechanism is 20,000. When the representative velocity is 200 [m / s], when the representative length scale is 50 μm, the Reynolds number shown in Equation (1) is 20,000. Become. Here, the representative speed may be slightly different depending on the shape of the relief valve, but the concept of the representative length scale is not changed, and it is considered that generation of cavitation bubbles can be suppressed if the radius of curvature is larger than this.

  Therefore, in the relief mechanism described in the first and second embodiments, the smooth curved shape 211 of the sheet portion front end 208 is formed by an arc 213, and the radius value of the arc is 50 μm or more.

  FIG. 10 shows an embodiment of the present invention. A housing 205 surrounding the low-pressure chamber 207 existing downstream from the valve body 201 and the seat portion 204 are integrated into a unit. A hole 214 is dug in the main body 213. The housing 204 and the seat portion 203 having an integral structure are formed as separate parts from the main body body 213, and the housing 205 and the seat portion 204 having the integral structure are formed in a hole 215 dug into the main body body 214. Is installed. The relief mechanism of this configuration has the characteristics described in the first, second, and third embodiments, and the sheet surface front end portion 208 is formed in a smooth curved shape.

  11 and 12 show an embodiment of the present invention. The seat part 216 is formed as a separate part with respect to the main body body 214, and the seat part 216 has a structure surrounding the high-pressure chamber 206 on the upstream side and is installed in a hole 215 dug into the main body body 214. It is the composition which becomes. When the valve body 201 collides with the seat portion 216, the seat portion 216 has an elastic material that can be elastically deformed or a structure having a thickness in order to reduce the impact force.

  At this time, similarly to the seat portion 204, if the seat surface leading end portion 208 has an edge shape, cavitation occurs due to an impact when the valve body 201 collides with the seat portion 216. FIG. 12 shows an enlarged view of the sheet surface front end portion 208 of the sheet portion 216. By forming the front end 208 of the seat surface into a smooth curved shape 217, the occurrence of cavitation when the valve body 201 collides can be suppressed.

  13 and 14 show an embodiment of the present invention. The main body 218 is directly dug to form a seat portion 219. When the valve body 201 collides with the seat portion 219, the seat portion 219 has an elastic material that can be elastically deformed or a structure having a thickness in order to reduce the impact force.

At this time, similarly to the seat portion 204, if the seat surface front end portion 208 has an edge shape, cavitation occurs in the vicinity of the seat surface front end portion 208 due to an impact when the valve body 201 collides with the seat portion 219. FIG. 14 shows an enlarged view of the sheet surface front end portion 208 of the sheet portion 219. By making the front end of the seat surface have a smooth curved shape 220, the occurrence of cavitation when the valve body 201 collides can be suppressed.

DESCRIPTION OF SYMBOLS 1 ... Pump housing, 2 ... Plunger, 8 ... Discharge valve mechanism, 9 ... Pressure pulsation reduction mechanism, 10c ... Suction passage, 11 ... Pressurization chamber, 12 ... Discharge passage, 20 ... Fuel tank, 23 ... Common rail, 24 ... Injector , 26 ... Pressure sensor, 30 ... Electromagnetic suction valve mechanism, 200 ... Relief valve mechanism, 201 ... Valve body, 202 ... Valve body presser, 203 ... Elastic member, 204 ... Seat part, 205 ... Housing, 206 ... High pressure chamber, 207 ... Low pressure chamber, 208 ... Seat surface tip, 209 ... High speed vibration, 210 ... Cavitation bubbles, 211 ... Smooth curved shape, 212 ... Chamfer, 213 ... Arc, 214 ... Body body, 215 ... Hole, 216 ... Sheet part, 217 ... Smooth curve shape, 218 ... Body body, 219 ... Sheet part, 220 ... Smooth curve shape, 300 ... Relief passage

Claims (5)

A pressurization chamber whose volume is changed by a reciprocating operation of the plunger, a suction passage for sucking fuel into the pressurization chamber, a discharge passage for discharging the fuel from the pressurization chamber, and a suction passage. A high-pressure fuel supply pump having a suction valve provided, a discharge valve provided in the discharge flow path, and a relief valve provided in the discharge flow path,
The relief valve has a relief channel having an inlet as the discharge channel and an outlet as the suction channel or the pressurizing chamber, and opens and closes in the relief channel according to a difference in pressure between the inlet and the outlet. a body and an elastic member for urging the valve body, and a seat portion for sealing the fuel the valve body and engages, a housing connected with the seat portion,
The seat portion has a thin-walled structure that can be elastically deformed so that the seat portion can be displaced when the valve body collides,
The seat surface tip on the inner peripheral side of the seat portion has a smooth curved shape, and the seat surface tip is formed upstream of the seat surface in the fuel flow direction when the relief valve is opened,
A high-pressure fuel supply pump, wherein a chamfered portion is provided at a connection portion between the seat portion and the housing. 2. The high-pressure fuel supply pump according to claim 1, wherein a curved shape of the front end portion of the seat surface on the inner peripheral side of the seat portion is formed by an arc, and a dimension value of the arc is 50 μm or more. High pressure fuel supply pump. 2. The high-pressure fuel supply pump according to claim 1, wherein the housing surrounding the low-pressure space existing downstream with respect to the valve body and the seat portion have an integral structure, and the integral structure is separate from the main body. In the configuration in which the integrated structure is installed in a hole formed in a part and dug into the body body, the front end portion of the seat surface on the inner peripheral side of the seat portion has a smooth curved shape High pressure fuel supply pump. 2. The high-pressure fuel supply pump according to claim 1, wherein the seat portion surrounds a high-pressure region upstream of the valve body, and the seat portion is formed as a separate part from the main body. The high-pressure fuel supply pump is characterized in that, in the configuration in which the seat portion is installed in the hole dug into the main body, the front end portion of the seat surface on the inner peripheral side of the seat portion has a smooth curved shape. . 2. The high-pressure fuel supply pump according to claim 1, wherein the body body is scraped to form a seat portion, and the front end portion of the seat surface on the inner peripheral side of the seat portion has a smooth curved shape. High pressure fuel supply pump.