JP6689153B2 - Fuel supply pump - Google Patents

Description

  The present invention relates to a fuel supply pump that supplies fuel to an internal combustion engine at high pressure, and relates to a fuel supply pump including a relief valve mechanism.

  Recently, miniaturization, high efficiency, and low exhaust of internal combustion engines have been vigorously promoted. In response to this, there is a strong demand for the fuel supply pump to have a smaller body that improves mountability in an internal combustion engine, and to have a high discharge pressure and a high volumetric efficiency that correspond to high efficiency and low exhaust emissions. .

  One of the most important issues facing the higher pressure of the fuel supply pump, which is the above-mentioned requirement, is the development of a relief valve inside the fuel supply pump. Since the relief valve determines the maximum allowable pressure of the entire fuel supply system, there is a demand for a relief valve that can be stably opened when necessary.

  In this regard, various proposals have been made for relief valve mechanisms. Among them, for example, Patent Document 1 discloses a structure in which a fluid throttle is provided on a side surface of a relief valve to form an intermediate chamber, and a relief valve lift is increased by pressure accumulated therein.

Japanese Patent No. 5103138

  As an example of improving the opening characteristic of the relief valve, in the example of Patent Document 1, pressure loss is generated in the fluid throttle provided on the side surface of the relief valve, whereby pressure is accumulated in an intermediate chamber formed between the seat portion and the fluid throttle, This is configured to act on the bottom surface of the relief valve. Thereby, the fluid force in the valve opening direction acts on the relief valve, the lift increases, and high opening performance can be obtained.

  However, with this structure, it is necessary to control the width of the gap between the relief valve holder and the relief valve body, so strict tolerance control is required for both the relief valve holder and the relief valve body, which may increase costs. There is.

  In view of the above problems, it is an object of the present invention to provide a low-cost relief valve mechanism capable of stably exhibiting high fuel release characteristics, and a fuel supply pump including the relief valve mechanism.

The present invention in order to solve the above problems, comprising: a pressurizing chamber for pressurizing fuel, the pressure chamber of the fuel discharge passage downstream of the ejection off valve or a relief valve mechanism back to the low pressure passage, the In the fuel supply pump, the relief valve mechanism includes a seat portion that closes a relief flow passage when a relief valve is seated, a relief valve holder that holds the relief valve, and the relief valve via the relief valve holder. And a relief spring for urging the sheet toward the seat portion, and the relief valve holder is pierced in the relief valve axial direction at a facing portion facing the seat portion, and when the relief valve is opened, A hole is formed to reduce the flow velocity of the fuel flowing between the facing portion and the seat, and the hole is formed substantially parallel to the relief valve axial direction .

  According to the configuration of the present invention, it is possible to realize a relief valve mechanism that stably exhibits high fuel release characteristics, and a fuel supply pump equipped with the relief valve mechanism, with an inexpensive structure.

The figure which shows the cross section of the relief valve 30 which concerns on Example 1 of this invention. The figure which shows the whole structure of the fuel supply pump system to which the Example of this invention is applied. 3 shows a flow velocity distribution inside the relief valve 30 according to the first embodiment of the present invention. 5 shows a pressure distribution in the relief valve 30 according to the first embodiment of the present invention. The figure which shows the cross section of the relief valve 30 which concerns on Example 1 of this invention. The figure which shows the cross section of the relief valve 30 which concerns on Example 1 of this invention. The figure which shows the cross section of the relief valve 30 which concerns on Example 2 of this invention. The figure which shows the cross section of the relief valve 30 which concerns on Example 3 of this invention.

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

  Examples will be described with reference to FIGS. FIG. 2 shows the overall configuration of a fuel supply pump system to which the fuel supply pump 300 of the present invention is applied. First, the overall configuration will be described with reference to FIG. 2, and then each embodiment of the relief valve mechanism will be described.

  The fuel supply pump system of FIG. 2 is roughly divided into a fuel tank 101 on the left side of the drawing, a fuel supply pump 300 on the center of the drawing, a fuel injection system 200 (common rail 53, injector 54, etc.) on the right side of the drawing, and an engine control unit (ECU) 40. The internal combustion engine 400 is provided with the fuel supply pump 1 and the injector 54 at the lower center of the drawing.

  The fuel supply pump 300 integrally incorporates a plurality of parts and mechanisms in the body 1 and is attached to the cylinder head 20 of the internal combustion engine 400. A suction passage 9, a pressurizing chamber 11, a discharge passage 12, and a relief passage 15 are formed in the body 1. The suction passage 9 is provided with an electromagnetic suction valve 5, the discharge passage 12 is provided with a discharge valve 8, and the relief passage 15 is provided with a relief valve 30. Further, the pressurizing chamber 11 in the body 1 has its volume changed by the plunger 2 which moves up and down by the rotation of the cam 7 of the internal combustion engine, so that the pump operation can be performed.

  The function of each valve formed in the fuel supply pump 300 will be briefly described. The electromagnetic suction valve 5 is a regulating valve that determines the amount of fuel to be pressurized. The discharge valve 8 is a check valve that limits the flow direction of fuel. The relief valve 30 functions as a safety valve that releases the abnormally high pressure fuel when the common rail 53 has an abnormally high pressure equal to or higher than the set pressure.

  According to the fuel supply pump system, the fuel from the fuel tank 101 is guided into the fuel supply pump 300, and passes through the electromagnetic suction valve 5 in the suction passage 9, the pressurizing chamber 11, and the discharge valve 8 in the discharge passage 12. The pressure is increased and is given to the fuel injection system 200. The fuel supply pump 300 is connected to the common rail 53 of the fuel injection system 200, the pressurized fuel is pressure-fed, and the high-pressure fuel is injected from the injector 54 into the combustion chamber of the internal combustion engine. The pressure in the common rail 53 is measured by the pressure sensor 56, and its signal is sent to the engine control unit (ECU) 40. The injectors 54 are mounted according to the number of cylinders of the engine, and injects fuel according to a signal from the engine control unit (ECU) 40. An engine control unit (ECU) 40 controls the electromagnetic suction valve 5 in the fuel supply pump.

  The fuel supply pump system of FIG. 2 is configured as described above. First, the function of each part of the fuel supply pump will be described in more detail.

  First, the connection relationship with the internal combustion engine for causing the pressurizing chamber 11 to perform a pump operation will be described. The plunger 2 is inserted into the recessed hole formed in the body 1 from the side opposite to the pressurizing chamber 11 (lower side in FIG. 2). The plunger 2 is slidably inserted into the cylinder 120, and a retainer 3 is attached to the lower end of the plunger 2. The urging force of the plunger return spring 4 acts on the retainer 3 in the direction toward the cam attached to the cam shaft of FIG. 2 (downward direction of FIG. 2). The tappet 6 reciprocates in the vertical direction in FIG. 2 by the rotation of the cam 7 of the internal combustion engine. Since the plunger 2 is displaced following the tappet 6, the volume of the pressurizing chamber 11 is changed by this and the pressurizing operation becomes possible.

  Next, the configuration of the electromagnetic intake valve 5 in the fuel supply pump controlled by the signal of the engine control unit (ECU) 40 will be described. The electromagnetic suction valve 5 is held by the body 1, and includes an electromagnetic coil 500, a mover 503, an anchor spring 502, and a suction valve valve spring 504. Hereinafter, the description will be made on the assumption that the movable portion 503 is formed of one member, but the movable portion 503 may be formed of two members, an anchor that forms the magnetic attraction surface and a rod that forms the sliding portion. Good.

  In the following, the description will be made on the premise of a system using a normally open type electromagnetic suction valve. An electromagnetic suction valve that is opened when the electromagnetic coil 500 is OFF and closed when the electromagnetic coil 500 is ON is called a normally open system. The urging force of the anchor spring 502 acts on the relief valve 501 in the valve opening direction via the movable portion 503, and similarly, the urging force of the intake valve spring 504 acts in the valve closing direction. Here, since the biasing force of the anchor spring 502 is larger than the biasing force of the suction valve spring 504, the suction valve 501 is in the open state when the electromagnetic coil 500 is OFF (non-energized). The operation is reversed, that is, the same applies to a fuel supply pump of an electromagnetic intake valve called a normally closed system in which the intake valve 501 is closed when the electromagnetic coil 500 is OFF (non-energized). The present invention can be applied.

  The relief valve 30 is formed by a relief valve 152 and a seat member 151. In addition, in the following description, the relief valve 30 of the pressurized chamber returning system will be described. A method of opening the abnormal high pressure generated on the common rail 53 side to the pressurizing chamber 11 will be referred to as a pressurizing chamber returning method.

  The relief valve 30 of FIG. 2 is formed in the relief passage 15. The relief passage 15 is connected to the downstream side of the discharge valve 8 (fuel injection system 200 side) and the pressurizing chamber 11, and The relief valve 152 is arranged in a direction in which the valve opens from the downstream side to the pressurizing chamber 11 side. The relief valve 152 is biased to the seat member 151 by a relief spring 154, and a seat portion 150 that seals fuel is formed on the seat member 151 at a contact portion between the two. The behavior of the relief valve 152 is determined by the differential pressure generated before and after the relief valve 152. That is, the pressure on the upstream side of the relief valve 152 (the pressure on the downstream side of the discharge valve 8) becomes larger than the pressure on the downstream side of the relief valve 152 (the pressure in the pressurizing chamber 11), and the urging force due to these differential pressures causes the relief. When the urging force of the spring 154 is overcome, the valve opening operation is started. The present invention can be similarly applied to a system using a low pressure return system in which the relief passage 15 is connected to the downstream side of the discharge valve 8 and the damper chamber 51.

  Next, the operation of the fuel supply pump 300 and the flow rate control method will be described. A state in which the plunger 2 is displaced downward in FIG. 2 due to the rotation of the cam 7 of the internal combustion engine is referred to as a suction process, and a state in which the plunger 2 is displaced upward is referred to as an ascending process. The rising process is composed of a return stroke and a compression stroke which will be described later. In the suction process, the volume of the pressurizing chamber 11 increases, and the fuel pressure therein decreases. In this suction step, when the fuel pressure in the pressurization chamber 11 becomes lower than the fuel pressure in the suction passage 9, the suction valve 501 of the electromagnetic suction valve 5 opens, and the fuel is sucked into the pressurization chamber 11.

  In the suction process, since the electromagnetic coil 500 is in the OFF state, the biasing force of the anchor spring 502 moves the rod portion at the tip through the movable portion 503 in the direction of opening the rod portion (rightward in FIG. 2). There is. Next, when the plunger 2 shifts from the suction stroke to the rising stroke, the electromagnetic coil 500 of the electromagnetic suction valve 5 is kept in the OFF state, so that the movable portion 503 and the rod portion at the tip end move to the valve opening position. Retained. In this state, the intake valve 501 moves in the valve closing direction (leftward in FIG. 2) to close the valve due to the rise of the plunger 2, but collides with the rod portion at the tip of the movable portion 503 in the valve opening position. Therefore, the valve cannot be closed and the open state is maintained.

  As a result, in the rising step, the pressure of the pressurizing chamber 11 is maintained at a low pressure almost equal to that of the suction passage 9, so the discharge valve 8 cannot be opened, and the fuel corresponding to the volume decrease of the pressurizing chamber 11 is It is returned to the damper chamber 51 side through the electromagnetic suction valve 5. This process is called a returning process. As a result, only the required flow rate is pressurized and discharged, and the flow rate can be controlled.

  Next, when the electromagnetic coil 500 of the electromagnetic suction valve 5 is energized in the returning step, the magnetic attraction force acts on the mover 503, overcoming the urging force of the anchor spring 502, and the movable portion 503 and the rod portion of the electromagnetic suction valve 5 move. It moves in the valve closing direction (leftward in FIG. 2) and is held in the valve closing position. In this state, or with the movement of the movable portion 503 in the valve closing direction, the suction valve 501 is closed by the biasing force of the suction valve spring 504 and the fluid differential pressure of the return fuel. Immediately after the suction valve 501 is closed, the fuel pressure in the pressurizing chamber 11 rises as the plunger 2 rises to form a compression stroke. As a result, the discharge valve 8 automatically opens, and the fuel is pressure-fed to the common rail 53.

  If the electromagnetic suction valve 5 that operates as described above is used, the flow rate discharged by the pump can be controlled by adjusting the timing of turning on the electromagnetic coil 500.

  FIG. 1 is a sectional view of a relief valve mechanism 30 according to the first embodiment. As shown in FIG. 1, the relief valve mechanism 30 of this embodiment includes a relief housing 155, and the relief housing 155 is press-fitted into a hole formed in the body 1 of the fuel supply pump 300. Although the relief housing 155 is configured integrally with the seat member 151 in FIG. 1, it may be configured separately.

  The ball valve 152a of the relief valve mechanism 30 is biased by the relief spring 154 toward the seat member 151 via the relief valve holder 152b, and the seat portion 150 for sealing fuel is formed at the contact portion between the two. There is. The behavior of the relief valve 152 is governed by the differential pressure generated before and after the relief valve 152. The relief valve holder 152b is biased by the relief spring 154 to bias the ball valve 152a against the seat portion 150. The ball valve 152a and the relief valve holder 152b together constitute a relief valve 152. Although it is possible to form both of them with one member, the processing cost can be reduced by using the ball valve 152a as a commercially available material.

  A pressure difference is generated between the pressure on the upstream side (right side in FIG. 1) of the relief valve 152 (pressure on the downstream side of the discharge valve 8) and the pressure on the downstream side (left side in FIG. 1) (pressure in the pressurizing chamber 11). When the urging force exceeds the urging force of the relief spring 154, the relief valve 152 starts the valve opening operation in the downstream direction. The relief spring 154 is supported by the outer peripheral portion of the spring support member 158, and the spring support member 158 is fixed to the relief housing 155 by press fitting. By adjusting the press-fitting depth of the spring support member 158, it is possible to adjust the biasing force of the relief spring 154 and change the differential pressure (set pressure) at which the valve opening operation starts.

  As described above, the fuel supply pump 300 of this embodiment pressurizes the fuel and pressurizes the fuel in the discharge passage downstream of the discharge valve 8 from the pressurizing chamber 11 or the low pressure passage (the suction passage 9, the damper chamber 51). ) And the relief valve mechanism 30 which returns to (). Then, the relief valve mechanism 30 includes a seat portion 150 that closes the relief flow passage (relief passage 15) by the relief valve 152a being seated, a relief valve holder 152b that holds the relief valve 152a, and a relief valve holder 152b. And a relief spring 154 for urging the relief valve 152a toward the seat 150 via the relief valve 152a.

  The relief valve holder 152b has a facing portion 156 (upstream side surface portion) facing the seat portion 150, which penetrates in the relief valve axial direction (the left-right direction in FIG. 1) and faces the relief valve 152a when the relief valve 152a opens. A hole 153 is formed to reduce the flow rate of the fuel flowing between 156 (upstream side surface) and the seat 150.

  FIG. 3 shows a flow velocity distribution diagram around the relief valve with and without the hole 153. It can be seen from FIG. 3 that the hole portion 153 reduces the flow velocity of the fuel flowing between the facing portion and the seat portion 151 when the relief valve 152 is opened. FIG. 4 shows a pressure distribution diagram around the relief valve with and without the hole 153. It can be seen from FIG. 4 that the pressure of the fuel between the facing part 156 and the seat part 150 is increased. Since the pressure increases, the fluid force acting in the opening direction of the relief valve 152 increases, and the opening performance of the relief valve 152 can be improved. The present inventors were able to confirm by analysis that the provision of this hole 153 increases the fluid force applied to the relief valve 152.

  Here, it is desirable that the hole portion 153 be formed on the inner peripheral side of the outermost peripheral portion 159 of the facing portion 156 of the relief valve holder 152b. If the hole portion 153 is formed on the outer peripheral side with respect to the outermost peripheral portion 159 of the facing portion of the relief valve holder 152b, the area of the upstream pressure receiving portion of the relief valve 152 may not be secured. On the other hand, according to the above configuration, this risk can be suppressed and the area of the upstream pressure receiving portion 156 of the relief valve 152 can be secured.

  Further, as shown in the cross-sectional view of the relief valve mechanism 30 in FIG. 5, it is desirable that the tangent line 157 drawn on the seat surface of the seat portion 150 overlaps the seat portion side end surface 153b of the hole portion.

  If the tangent line 157 drawn to the seat surface of the seat portion 150 is configured to be separated from the seat portion side end surface 153b of the hole portion 153, the fuel flowing from the upstream side may not easily flow into the hole portion 153. On the other hand, according to the above configuration, this fear is suppressed, and the fuel flowing in from the upstream side easily flows into the hole 153. Although the number of holes is arbitrary, it is preferable that the number of holes is four or more from the viewpoint of maintaining balance when the relief valve is lifted. Further, it is desirable that the hole 153 be substantially parallel to the axial direction of the relief valve 152.

  When the hole 153 is displaced from the direction parallel to the axial direction of the relief valve 152, it becomes difficult for the fuel to flow into the hole 153, and the fuel easily flows between the facing portion and the seat 150. Then, the flow velocity of the fuel between the facing portion 156 and the seat portion 150 increases, and the pressure of the fuel between the facing portion 156 and the seat portion 150 decreases. For this reason, the fluid force applied in the lift direction of the relief valve 152 is reduced, and the opening performance of the relief valve 152 may be reduced. On the other hand, with the above configuration, this risk can be suppressed and the opening performance of the relief valve 152 can be improved.

  Further, as shown in the cross-sectional views of the relief valve valve mechanism 30 of FIGS. 1 and 5, the relief valve valve holder is disposed on the outermost peripheral portion 159 and the relief valve valve holder 152b on the outer peripheral side and faces the outermost peripheral portion 159. It is desirable that the clearance 160 between the opposite surface of the relief housing 155 and the opposite surface is 0.2 mm or more. Although the outermost peripheral portion 159 is shown on the same plane as the facing portion 156 in FIG. 4, the position of the outermost peripheral portion 159 is not limited to this.

  If the clearance between the outermost peripheral portion 159 of the relief valve valve holder 152b and the opposing surface of the relief housing 155 that is arranged on the outer peripheral side of the relief valve valve holder 152b and that faces the outermost peripheral portion 159 is 0.2 mm or less, the tolerance is The control becomes strict and the cost at the time of manufacturing the fuel supply pump increases. With the above configuration, this can be suppressed and the cost at the time of manufacturing the fuel pump can be reduced.

  Further, as shown in the cross-sectional view of the relief valve mechanism 30 of FIG. 6, in the state where the relief valve 152 is opened at the maximum opening degree, the facing portion 156 of the relief valve holder 152b and the seat member 151 that faces the facing portion 156 substantially in parallel therewith. It is desirable that the clearance between the opposite surface of the hole 153 and the opposite surface be less than or equal to the diameter of the hole 153. Further, when the gap is 0.2 mm or less as described above, the differential pressure between the upstream surface and the downstream surface of the relief valve increases, so that the fluid force applied to the relief valve can be increased. In the state where the relief valve 152 is opened at the opening, when the clearance between the facing portion 156 of the relief valve holder 152b and the facing surface of the seat member 151 that faces the relief valve holder 152b is equal to or larger than the hole diameter of the hole portion 153, The fluid force acting on the relief valve holder 152b may reduce the opening performance of the relief valve 30. With the above configuration, this can be suppressed and the relief valve opening performance can be improved. In this embodiment, when the relief valve 152a is opened, the entire flow path from the seat portion 150 to the downstream side of the relief valve holder 150b is configured to be 0.1 mm or more.

  FIG. 7 is a sectional view of a relief valve mechanism according to the second embodiment of the present invention. In FIG. 8, 1 is a pump body, 150 is a seat portion, 153 is a hole portion, 154 is a relief spring, 155 is a housing, 151 is a seat member, 156 is an intermediate chamber, 156 is an opposing portion (upstream pressure receiving surface), 158. Represent spring support members, respectively.

  In the second embodiment, the hole 153, which is one place in the first embodiment, is arranged in three or more places. Since the flow field can be made symmetrical with respect to the central axis of the relief valve 152 by increasing the number of holes, the inclination of the relief valve 152 can be suppressed.

  FIG. 8 is a sectional view of the relief valve mechanism 30 according to the third embodiment of the present invention. In FIG. 7, 1 is a pump body, 150 is a seat portion, 153 is a hole portion, 154 is a relief spring, 155 is a housing, 151 is a seat member, 156 is an intermediate chamber, 156 is a facing portion (upstream pressure receiving surface), 158. Represent spring support members, respectively.

  In the third embodiment, the hole 153 is formed so as to communicate with the recess of the relief valve holder 152b. With the above configuration, fuel easily flows into the hole 153. Then, it becomes difficult for fuel to flow between the facing portion 156 and the sheet member 151. The flow velocity of the fuel between the facing portion 156 and the seat member 151 decreases, and the fuel pressure between the facing portion 156 and the seat member 151 increases according to Bernoulli's theorem. Physical strength becomes high. Therefore, the opening performance of the relief valve 152 can be improved. It has been confirmed by analysis that a higher fluid force is applied to the relief valve when the hole 153 is formed in communication with the recess of the relief holder 152b than when the hole 153 is formed apart from the recess. .

  Further, it is desirable that the cross-sectional area of the hole portion 153 when viewed in the axial direction of the relief valve 152 is formed to be 1/300 or more of the cross-sectional area of the relief valve holder.

  If the cross-sectional area of the hole portion 153 when viewed in the axial direction of the relief valve 152 is less than 1/300 of the cross-sectional area of the relief valve holder 152b, fuel cannot pass through the hole portion 153 and the seat member Fuel flows between 151 and the facing portion 156 of the relief valve holder 152b, and the flow velocity becomes faster. According to Bernoulli's theorem, the pressure generated between the seat member 151 and the facing portion 156 of the relief valve holder 152b becomes low, and the fluid force acting on the relief valve 152 becomes small. Therefore, the opening performance of the relief valve 152 may be deteriorated. With the above configuration, this can be suppressed and the opening performance of the relief valve 152 can be enhanced.

  INDUSTRIAL APPLICABILITY The present invention is widely applicable to various high pressure pumps as well as fuel supply pumps for internal combustion engines.

1: Body 2: Plunger 3: Retainer 4: Return spring 5: Electromagnetic suction valve 6: Tappet 7: Cam 8: Discharge valve 9: Suction passage 11: Pressurization chamber 12: Discharge passage 15: Relief passage 150: Seat 151 : Valve seat 152: Relief valve 152a: Ball valve 152b: Relief valve holder 153: Hole 154: Relief spring 155: Housing 156: Upstream pressure receiving surface 157: Tangent line 158 drawn to the seat surface: Spring support member 53: Common rail 54 : Injector 56: Pressure sensor

Claims (8)

A pressurizing chamber for pressurizing fuel,
In a fuel supply pump comprising a relief valve mechanism for returning the fuel in the discharge passage downstream of the discharge valve to the pressure chamber or the low pressure passage,
The relief valve mechanism is
A seat portion that closes the relief flow passage by seating the relief valve,
A relief valve holder for holding the relief valve,
A relief spring that urges the relief valve toward the seat portion via the relief valve holder,
When the relief valve is opened, the flow velocity of the fuel flowing between the facing portion and the seat portion is reduced when the relief valve holder penetrates in the relief valve axial direction at the facing portion facing the seat portion. hole which is formed,
The hole is a fuel supply pump formed substantially parallel to the axial direction of the relief valve . The fuel supply pump according to claim 1,
The hole is a fuel supply pump formed on an inner peripheral side of an outermost peripheral portion of the facing portion of the relief valve holder. The fuel supply pump according to claim 1,
The fuel supply pump, wherein the hole portion is configured such that a tangent line drawn to the seat surface of the seat portion overlaps the seat portion side end surface of the hole portion. The fuel supply pump according to claim 1,
A fuel supply pump configured such that, in a state where the relief valve is opened, all the flow passages from the seat portion to the downstream side of the relief valve holder have a hole diameter of the hole portion or less. The fuel supply pump according to claim 1,
The relief valve holder receives a projecting portion that projects to the side opposite to the surface that holds the relief valve, and the relief spring on the radially outer side of the projecting portion, and the length in the relief valve axial direction is greater than that of the projecting portion. Also has a short spring receiving portion,
The hole is a fuel supply pump formed by penetrating the spring receiving portion . The fuel supply pump according to claim 1,
A fuel supply pump formed such that the cross-sectional area of the hole when viewed in the axial direction of the relief valve is 1/300 or more of the cross-sectional area of the relief valve holder. The fuel supply pump according to claim 1,
The fuel supply pump in which the holes are formed at least at three or more locations in the facing portion of the relief valve holder. The fuel supply pump according to claim 1,
The fuel supply pump, wherein the relief valve holder is formed with a recess for holding the relief valve, and the hole is formed in communication with the recess of the relief valve holder.

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