JP5625016B2 - High pressure fuel pump - Google Patents

Description

  The present invention relates to a high-pressure fuel supply pump that supplies high-pressure fuel to a fuel injection valve of a direct injection internal combustion engine.

  The high-pressure fuel pump targeted by the present invention includes a plunger that slides on a cylinder, and the tip of the plunger reciprocates in the pressurizing chamber to compress and pressurize the fuel introduced from the suction valve mechanism into the pressurizing chamber. Discharge from the discharge valve mechanism.

  This type of high-pressure fuel supply pump has a pressurization chamber formed in the pump body, and the tip of the cylinder protrudes into the pressurization chamber (for example, described in International Publication WO00 / 47888 pamphlet and International Publication WO02 / 055881 pamphlet). And a type in which a pressurizing chamber is formed in a cylinder (for example, those described in Japanese Patent Application Laid-Open Nos. 2003-49743 and 2001-295770).

International Publication WO02 / 055881 Pamphlet JP 2001-295770 A JP 2003-49743 A International Publication WO00 / 47888 Pamphlet

  In this type of high-pressure fuel supply pump, the high pressure and large capacity of the fuel have progressed, for example, constantly at a high speed of about 100 hertz (Hz) (currently only encountered in a high-speed rotation region where the engine rotates 6000 per minute). When reciprocating, heat generated by sliding of the sliding surfaces of the cylinder and plunger depletes pressurized fuel supplied as a lubricant to both sliding surfaces, resulting in the generation of slight stress acting in the radial direction. There may be a problem that the sliding surfaces of the two are seized or bite.

  Although there are various theories about the seizure mechanism, it is already known that reducing the temperature of the sliding surface is one of the means for preventing seizure. In particular, in the lower part of the cylinder (the end portion on the low-pressure fuel chamber side) where the heat generation is particularly large, there is a problem that it is difficult to cool the cylinder because the fluid stays in particular.

  An object of the present invention is to provide a high-pressure fuel supply pump of this kind that is robust and has a high lubricity between the sliding surfaces of the cylinder and the plunger.

  In the present invention, in order to achieve the above object, the cylinder and the pump body are formed as separate members, and the plunger has a diameter larger than the diameter of the portion that slides on the cylinder on the outer peripheral portion opposite to the pressurizing chamber. A small stepped portion is formed, and the stepped portion of the plunger that reciprocates in the low pressure fuel chamber increases or decreases the volume of the low pressure fuel chamber to generate fuel flow between the low pressure fuel chamber and the low pressure fuel passage. The fuel flow was configured to cool the cylinder directly or indirectly.

  According to the present invention configured as described above, the cylinder can be cooled by utilizing the positive fluid flow in the pump.

  Since the flow of fluid occurs in response to the movement of the plunger, in an operating state where the plunger moves slowly, i.e., in a small amount of heat generation, the cooling fluid flow is small and the plunger moves fast, i.e., in an operating state where the amount of heat generation is large. Then, the flow of the cooling fluid becomes large.

  As a result, the cylinder can be efficiently cooled, and a robust high-pressure fuel pump was obtained.

It is explanatory drawing which showed the implementation method of a high pressure fuel pump. It is explanatory drawing which showed the implementation method of a high pressure fuel pump. It is the graph which showed the operation | movement process of the high pressure fuel pump. It is the figure which showed the flow of the fuel in the high pressure fuel pump of each process. It is the figure which showed the flow of the fuel in the high pressure fuel pump of each process. It is the figure which showed the flow of the fuel in the high pressure fuel pump of each process. It is explanatory drawing which expanded the pressurization mechanism part. It is explanatory drawing which expanded the cooling part. It is explanatory drawing which expanded the cooling part. The equation of heat transfer for cooling is shown. It is the enlarged view of the groove | channel of a cylinder, and the projection figure showing the area of a groove channel. It is the enlarged view of the groove | channel of a cylinder, and the projection figure showing the area of a groove channel. It is the graph which showed the flow volume for cooling in a discharge process rate. It is the graph which showed high-pressure pump rotation speed, and friction and cooling energy. It is a figure which shows the fuel system which uses a high pressure fuel pump. It is a figure which shows the Example at the time of increasing the groove | channel of a cylinder. It is a figure which shows the Example at the time of increasing the groove | channel of a cylinder.

  An embodiment to which the present invention is applied has the following basic configuration.

  The cylinder 6 combined with the pump body 1, the plunger 2 slidingly reciprocatingly engaged with the cylinder 6, the pump body 1 and the cylinder 6 are defined, and the one end 2a of the plunger 2 enters and exits. The other end 2b of the plunger 2 enters and exits, and includes a low-pressure fuel chamber 10g communicating with the low-pressure fuel passage (10c, 10d). The plunger 2 is an outer peripheral portion of a portion entering and exiting the low-pressure fuel chamber 10g. In addition, a stepped portion (2a, 2b) having a smaller diameter than a portion that slides on the cylinder 6 is provided, and the volume of the low pressure fuel chamber 10g is increased or decreased by entering or leaving the stepped portion (2a, 2b) of the plunger 2. The fuel flows into the low-pressure fuel chamber 10g from the low-pressure fuel passage (10c, 10d), and the fuel flows out from the low-pressure fuel chamber 10g into the low-pressure fuel passage (10c, 10d). It is configured to low-pressure fuel chamber 10g side end of the cylinder 6 is exposed to the flow of fuel which is formed between the low pressure fuel chamber 10g and the low pressure fuel passage (10c, 10d).

  Preferably, the fuel flow between the low pressure fuel chamber 10g and the low pressure fuel passages (10c, 10d) passes through a hole or groove 10f provided in the cylinder 6.

  Preferably, the fuel flow between the low pressure fuel chamber 10g and the low pressure fuel passage (10c, 10d) is a hole or groove (10f) provided in any of the members surrounding the cylinder 6 (pump body 1 or cylinder holder 7). )

  Preferably, a plurality of holes or grooves 10f provided in the cylinder 6 are provided.

  Preferably, a plurality of holes or grooves (10f) provided in any of the members surrounding the cylinder 6 (pump body 1 or cylinder holder 7) are provided.

  Preferably, a plurality of holes or grooves 10f provided in the cylinder 6 are provided symmetrically with respect to the central axis of the plunger 2 or at equal intervals in the circumferential direction.

  Preferably, a plurality of holes or grooves (10f) provided in any of the members surrounding the cylinder 6 (pump body 1 or cylinder holder 7) are symmetric with respect to the central axis of the plunger or in the circumferential direction, etc. It is provided at intervals.

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

  A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a longitudinal sectional view of a high-pressure fuel pump in which the present invention is implemented. FIG. 15 shows a fuel supply system using the high-pressure fuel pump of FIG.

  The fuel sucked up from the fuel tank 20 by the low-pressure feed pump 21 is guided to the fuel inlet 10 a of the high-pressure fuel pump 100 through the suction pipe 28. The discharge amount of the low-pressure feed pump 21 is controlled by a signal 27D of an engine control unit 27 (hereinafter abbreviated as ECU) so that the pressure in the low-pressure pipe 28 becomes a desired pressure.

  The fuel led to the fuel suction port 10a is led to the low pressure chamber 10d through a damper chamber 14 (described later) in which the metal damper 9 is installed and a suction passage 10c.

  The pump body 1 is provided with a pressurizing chamber 11, and between the pressurizing chamber 11 and the low-pressure chamber 10d is provided a suction valve 31 and a seat 32 that controls the intake and shutoff of fuel in cooperation.

  The suction valve 31 urged in the direction of seating on the seat 32 by the spring 33 is pushed out in a direction away from the seat 32 against the spring by the electromagnetic drive mechanism 30A. The suction valve 31, the seat 32, the spring 33, and the electromagnetic drive mechanism 30A constitute an electromagnetically driven suction valve 30.

  As the plunger 2 descends due to the rotation of the cam 5, the pressure in the pressurizing chamber 11 decreases, so that the suction valve body 31 overcomes the urging force of the spring 33 due to the pressure difference between the front and rear, and the fuel is opened in the pressurizing chamber 11. Flow into. During the fuel inflow process, an electric current is applied to the electromagnetically driven intake valve 30 to strengthen the valve open state. Thereafter, when the electromagnetically driven suction valve 30 closes the suction valve 31 at a specific timing after the cam 5 rotates and the plunger 2 starts to rise, the sucked fuel rises in the pressurizing chamber 11. The fuel is pressurized to a high pressure by way of the fuel discharge port 12, passes through the high-pressure pipe 29, passes through the throttle 25, and is pumped to the common rail 23.

  A pressure sensor 26 is attached to the common rail 23, and the ECU 27 monitors the output of the pressure sensor 26 to detect a pressure change in the common rail. An injector 24 attached to each cylinder of the internal combustion engine is connected to the common rail 23, and the injector 24 directly injects an amount of fuel required by each cylinder into the cylinder by a drive signal from the ECU 27.

  27A is a power line that sends a drive current to the electromagnetic drive mechanism 30A, 27B is a signal line that sends a detection signal of the pressure sensor 26 to the ECU, and 27C is a power line that sends a drive current to the fuel injection valve 24.

The high-pressure fuel pump 100 according to this embodiment shown in FIG. 1 includes all the components surrounded by a broken line 100 in FIG.

  The pump body 1 is formed with a cylindrical recess that forms a pressurizing chamber 11. The pressurizing chamber 11 is provided together with a cylinder 6 that is fixed to the pump body 1 so that the tip projects into the cylindrical recess. Forming. A plunger 2 is slidably accommodated in the cylinder 6 and constitutes a pressure mechanism. As a result of the metal contact portion between the outer peripheral portion of the cylinder 6 and the pump body 1 functioning as a metal seal portion with respect to the internal fuel, the plunger 2 reciprocating in the pressurizing chamber 11 and the electromagnetically driven intake valve 30 described above, Further, the discharge valve mechanism 8 including the seat 8a, the discharge valve 8b, and the biasing spring 8c cooperates to pressurize the fuel in the pressurizing chamber to about 20 megapascals (MPa) or more if necessary. .

  The metal damper 9 is mounted in the fuel passage on the low pressure side and has a function of reducing fuel pulsation generated in the fuel passage on the low pressure side.

  The pulsation of the fuel generated in the fuel passage on the low-pressure side is caused by raising the plunger 2 with the intake valve 31 open to control the fuel discharge amount, so that the fuel once introduced into the pressurizing chamber is reduced in pressure. Occurs when backflowing (also called overflow) into the chamber 10d.

  The electromagnetically driven intake valve 30 also has a function of controlling the amount of discharged fuel. Specifically, when the cam 5 rotates and the plunger 2 is lowered by the force of the spring 4, that is, pulled into the cylinder 6, it is attracted to the seat 32 by the spring 33 and the intake valve 31 in the closed state is closed. The pressure difference between the pressure on the low pressure chamber 10d side (the feed pressure of the feed pump 21 is 1.5 to 2 atmospheres: 0.15 to 0.2 MPa) and the pressure on the pressurization chamber 11 side changes, and the suction valve 31 The force acting in the opening direction becomes larger, and the suction valve 31 separates from the seat 32 and opens against the force of the spring 33. That is, the suction valve 31 is set so that it can be opened by overcoming the urging force of the spring 33 by the valve opening force due to the fluid differential pressure. When the intake valve 32 is opened, low-pressure fuel is introduced into the pressurizing chamber 11. This state is called an inhalation stroke.

  When a current is supplied to the electromagnetic drive mechanism 30A before the cam 5 further rotates and the plunger 2 starts to rise, the electromagnetic plunger 30B receives an electromagnetic force in the direction in which the intake valve 31 is kept open to further compress the spring 33. To do.

  Thus, even if the cam 5 further rotates and the plunger 2 rises, the intake valve 31 remains open, and the fuel flows back to the low-pressure chamber, that is, returns (also called overflow). This process is referred to as the return process (or overflowing process).

  At this time, pressure pulsation is generated in the low pressure passage 10 by the fuel returned to the suction passage 10c. This pressure pulsation is absorbed and reduced as the metal damper 9 expands and contracts.

  When the current supplied to the electromagnetic drive mechanism 30A is cut off, the electromagnetic plunger 30B is quickly closed by the biasing force of the spring 33 and the fluid force acting on the intake valve 31 at that time. From this point of time, the fuel compression action by the plunger 2 starts, and when the fuel pressure becomes higher than the force of the spring 8c that biases the discharge valve 8b in the valve closing direction, the fuel opens the discharge valve 8b. Then, it is discharged to the discharge port 12 of the pump 100. This stroke is referred to as a discharge stroke. As a result, the compression stroke of the plunger consists of a return stroke and a discharge stroke.

  And the quantity of the high-pressure fuel discharged can be controlled by controlling the timing which cancels | releases the electricity supply to the electromagnetically driven intake valve 30. FIG. If the timing of releasing the energization is advanced, the ratio of the return stroke in the compression stroke (up stroke) is reduced, and the proportion of the discharge stroke is increased. That is, the amount of fuel returned to the low pressure chamber 10d is small, and the amount of fuel that is pressurized and discharged is large. On the other hand, if the timing of releasing the energization is delayed, the ratio of the return stroke in the compression stroke (up stroke) increases and the proportion of the discharge stroke decreases. That is, the amount of fuel returned to the low pressure chamber 10d is large, and the amount of fuel pressurized and discharged is reduced. The timing at which energization is released, that is, the fuel discharge amount, is determined and controlled by the ECU 27 in accordance with the operating state of the engine.

  In the pump body 1, a cylindrical passage 10b that is a part of the low-pressure passage 10 is formed outside a cylindrical recess that forms the pressurizing chamber 11, and this passage 10b has a circular opening. . The circular opening is sealed by an internal damper cover 14, and two metal dampers 9 are provided inside the circular opening.

  Thus, the fuel is introduced through the fuel introduction opening 10a formed in the pump body 1, the cylindrical passage 10b provided with the metal damper 9, and the suction passage 10c communicating with the low pressure chamber 10d.

  The electromagnetically driven suction valve 30 is fixed to the pump body 1 by welding, the suction valve 31 is installed at the entrance of the pressurizing chamber 11, and the suction passage 10c is located on the opposite side of the pressurizing chamber 11 with respect to the suction valve seat portion 32. Communicate.

  The pump body 1 is further formed with a horizontal cylindrical recess for attaching the discharge valve mechanism 8 communicating with the cylindrical recess forming the pressurizing chamber 11. This recess is designed to have a diameter smaller than the diameter of the horizontal cylindrical recess for mounting the discharge valve mechanism 8 so that the discharge valve mechanism 8 can be inserted from the side of the horizontal cylindrical recess for mounting the electromagnetically driven suction valve 30. Has been.

  After the discharge valve mechanism 8 is press-fitted and fixed in the horizontal cylindrical recess having a small diameter, a cylindrical metal ring is press-fitted and fixed to the inner upper end of the cylindrical recess forming the pressurizing chamber 11, and a part of the outer periphery thereof is fixed. A function of preventing the removal of the discharge valve mechanism 8 so as to face the end portion of the discharge valve mechanism 8 fixed earlier, and a function of increasing the compression efficiency by reducing the volume of the pressure chamber. Is given.

  Next, the cylinder 6 is inserted into the cylindrical recess of the pump body 1 so that the tip projects into the cylindrical recess forming the pressurizing chamber 11, and the annular sealing surface formed on the outer periphery of the cylinder 6 is the cylinder. It attaches so that it may contact | abut to the sealing surface formed around the opening part of a concave shape.

  Specifically, a seal ring 7A is attached to the outer periphery of the cylinder holder 7, and then an annular gasoline seal and an oil seal that are in sliding contact with the surface of the plunger 2 are mounted at a predetermined distance in the axial direction. Is installed in the cylinder holder 7, and the lower end side of the plunger 2 is inserted into the seal mechanism 13. Next, the cylinder holder 7 is mounted between the outer periphery of the lower end of the cylinder 6 and the inner periphery of the cylindrical sleeve 1S of the pump body 1 protruding to the periphery while the tip of the plunger 2 is inserted into the cylinder.

  At this time, the diameter is set so that the stepped portion of the inner periphery of the cylinder holder 7 contacts the lower end of the cylinder.

  Further, the inner peripheral stepped portion of the tightening holder 40 having a screw threadedly engaged with a screw engraved on the outer periphery of the cylindrical sleeve 1S is brought into contact with the outer peripheral stepped portion of the cylinder holder 7 for tightening. The cylinder holder 7 is pressed against the lower end of the cylinder 6 by screwing the holder 40 into the cylindrical sleeve 1S, and further, the pressurizing chamber is pressed by pressing the seal surface of the outer peripheral stepped portion of the cylinder 6 against the lower end seal surface of the pump body 1. Seal.

  A mounting bracket 41 for fixing the pump to the engine is fastened together between the tightening holder 40 and the pump body 1 to fix the pump.

  For mounting the high-pressure fuel pump 100 on the engine, the other end of the spring 4 whose one end abuts on the lower end of the cylinder holder 7 is held by a spring receiver 15 attached to the lower end of the plunger, and the lifter 3 is put on the spring receiver. Next, using the outer periphery of the lifter 3 as a guide, the lower end portion of the plunger 2 is inserted into the mounting hole of the engine head until the lifter 3 comes into contact with the cam 5, and the tightening holder 40 is sealed with a seal ring provided on the outer periphery of the tightening holder 40. Seal between the outer periphery and the inner peripheral surface of the mounting hole. Finally, the mounting bracket 41 is screwed to the engine with a screw 42, and the tightening holder 40 is pressed against the surface of the engine and fixed.

  The plunger 2 reciprocates inside the pressurizing chamber 11, sucks fuel into the pressurizing chamber 11, overflows from the pressurizing chamber 11 to the low pressure chamber 10d, pressurizes the fuel in the pressurizing chamber, and pressurizes the fuel. It performs a so-called pump function that discharges the discharged fuel.

  Fuel that leaks from the pressurizing chamber 11 through the gap between the plunger 2 and the cylinder 6 (referred to as blow-by fuel) reaches a seal chamber 10 g formed between the seal mechanism 13 and the lower end of the cylinder 6. The seal chamber 10f has a longitudinal groove 10f formed on the outer periphery of the cylinder 6, an inner periphery of the pump body 1, an outer periphery of the cylinder 6, an outer periphery of the cylinder holder 7 surrounded by the cylinder holder 7 and the seal ring 7A. The suction passage 10c communicates with a circular space 10e that makes a round and a return passage 10d that is formed through the pump body 1. Accordingly, it is possible to prevent the pressure of the fuel reservoir 10g from being abnormally increased by blow-by fuel and adversely affecting the seal mechanism.

  The sealing mechanism 13 provided on the outer periphery of the lower end of the plunger 2 prevents the fuel from leaking to the outside, and at the same time, the lubricating oil that lubricates the contact portion between the cam 5 and the lifter 3 and between the lifter 3 and the plunger 2 is pressurized chamber 11. And flow into the fuel passage such as the low pressure chamber 10d.

  A relief mechanism 200 that prevents the common rail 23 from becoming an abnormally high pressure is provided in the pump body 1. The relief mechanism 200 includes a relief valve seat 201, a relief valve 202, a relief press 203, and a relief spring 204. The relief mechanism 200 branches from the high-pressure passage between the downstream of the discharge valve mechanism 8 and the discharge port 12 and reaches the suction passage 10c. Arranged in the passages 210 and 211. When the pressure in the high-pressure fuel passage including the common rail 23 is about to become abnormally high, the pressure is transmitted to the relief valve 201, and the relief valve 201 is separated from the relief valve seat 201 against the force of the relief spring 204, and the abnormal high pressure is sucked into the suction passage. This prevents the high-pressure pipe 29 and the common rail 23 from being damaged. Since the abnormal high pressure is transmitted through the throttle 214, the relief valve 202 does not open in a very short time high pressure state that occurs during discharge. This prevents malfunction.

Here, it demonstrates that the plunger 2 has a large diameter part and a small diameter part. The plunger 2 includes a large diameter portion 2 a that slides with the cylinder 6 and a small diameter portion 2 b that slides with the plunger seal 13. The diameter of the small diameter portion 2b is set smaller than the diameter of the large diameter portion 2a, and is set coaxially with each other. In the present embodiment, the diameter of the large diameter portion 2a is 10 mm, and the diameter of the small diameter portion 2b is 6 mm.
Is set to Thus, by providing a large diameter part and a small diameter part in a plunger, there exist some advantages as follows. One is to reduce the pulsation of the low-pressure side pressure. Of the pulsations that occur as the plunger moves up and down, the pressure pulsations that occur upstream from the electromagnetically driven suction valve 30 can be reduced. The pressure pulsation generated on the upstream side of the electromagnetically driven suction valve 30 can cause noise, deteriorate the durability of the feed pump 21, deteriorate the durability of the low-pressure pipe 28 itself, etc. It is a cause of deterioration in various performances. The second advantage is that the plunger seal 13 can be made small. The advantage of downsizing is that the length of the fuel seal with the plunger is shortened, so that the amount of leakage from the seal can be further reduced, the frictional heat with the plunger can be reduced, the weight is reduced, and the cost is low.

  Hereinafter, the mechanism that reduces the pressure pulsation on the low pressure side by configuring the plunger 2 with the large diameter portion 2a and the small diameter portion 2b, which is the first advantage, will be described with reference to FIGS. I will explain.

  FIG. 3 is a diagram in which the horizontal axis represents time, briefly explaining the process when the pump reciprocates once and the movement of the solenoid that is an electromagnetic suction valve.

[Inhalation process]
At time TT, the plunger 2 is at the top dead center, that is, the pressure chamber has the smallest volume and the seal chamber has the largest volume. As the cam rotates, the plunger 2 starts to descend due to the compression reaction force of the spring 4. When the plunger 2 starts to descend, the pressure in the pressurizing chamber 11 decreases due to the increase in the volume of the pressurizing chamber 11, and the suction valve body 31 is moved by the difference from the pressure in the electromagnetically driven suction valve 30. It overcomes the biasing force and opens the valve. In this suction process, the fuel flowing into the pressurizing chamber 11 includes not only the fuel from the suction port 10a but also the fuel due to the volume reduction of the seal chamber 10g due to the movement of the plunger 2. When the diameter of the large diameter portion of the plunger 2 is φd ₁ , the diameter of the small diameter portion is φd ₂ , and the moving speed of the plunger is vp, the fuel flowing into the pressurizing chamber = φd ₁ ² × vp (φd ₁ ² − φd ₂ ² ) / φd ₁ ² × vp fuel flows in through the fuel passage 10d, and φd ₂ ² / φd ₁ ² × vp fuel flows in from the suction port 10a. In this embodiment, since the large diameter portion is 10 mm and the small diameter portion is 6 mm, the flow rate of (100−36) / 100 × vp = 64/100 × vp is sucked from the seal chamber 10 g and 36/100 × vp of fuel is sucked. It will flow from the mouth 10a.

  In preparation for the next return process and discharge process, at time T1, an electric current is sent from the ECU side to the electromagnetically driven intake valve 30, and the current energizes the solenoid 30b to open the intake valve 31, Strengthen the open state.

[Return process]
At time TB, the plunger 2 is at the bottom dead center, that is, the state where the volume of the pressurizing chamber 11 is the largest and the volume of the seal chamber 10g is the smallest. As the cam 5 rotates, the plunger 2 starts to rise. When the plunger 2 starts to rise, as the volume of the pressurizing chamber 11 decreases, the fuel in the pressurizing chamber 11 moves in the opposite direction to the suction process. That is, the fuel in the pressurizing chamber is not only returned to the suction port 10a but also returned to the seal chamber 10g through the fuel passage 10d due to the volume reduction of the seal chamber 10g due to the movement of the plunger.

Assuming that the diameter of the large-diameter portion of the plunger 2 is φd ₁ and the diameter of the small-diameter portion is φd ₂ , the fuel flowing out from the pressurizing chamber 11 = φd ₁ ² × vp (φd ₁ ²⁻ φd ₂ ² ) / φd ₁ ² × vp fuel passes through the fuel passage 10d and returns to the seal chamber 11g, and φd ₂ ² / φd ₁ ² × vp fuel returns to the inlet 10a. In this embodiment, since the large diameter portion is 10 mm and the small diameter portion is 6 mm, the flow rate of (100−36) / 100 × vp = 64/100 × vp is supplied to the seal chamber 10 g, and 36/100 × vp fuel is supplied. It will be returned to the inlet 10a.

[Discharge process]
In the ECU 27, a time T2 is calculated so as to obtain a desired discharge flow rate, and the current applied to the electromagnetically driven intake valve 30 at the time T2 is cut off. The suction valve body 31 that has been energized by electromagnetic force until time T <b> 2 starts to close by the compression reaction force of the spring 33 and the force of the fluid that passes through the suction valve body 31 and the seat 32. After completely closing the valve, the pressure in the pressurizing chamber rises due to the decrease in the volume of the pressurizing chamber due to the rise of the plunger, and the discharge valve 8a is pushed out and the discharge process is started. The discharge process continues until the plunger 2 reaches top dead center.

In this discharge process, the volume of the seal chamber 10g increases. As the volume of the seal chamber 10g increases, fuel flows from the discharge port 10a into the seal chamber 10g. The discharge flow rate is φd ₁ ² × vp, while the flow rate flowing into the seal chamber 10g is (φd ₁ ² −φd ₂ ² ) / φd ₁ ² × vp. In this embodiment, since the large diameter portion is 10 mm and the small diameter portion is 6 mm, a flow rate of (100−36) / 100 × vp = 64/100 × vp flows from the discharge port 10a into the seal chamber.

Here, it should be noted that in any step of the suction process, the return process, and the discharge process, that is, in all the states where the pump is operating, the passage 10d has (φd ₁ ² −φd ₂ ² ). That is, a flow rate of / φd ₁ ² × vp is flowing (see FIG. 13). In this embodiment, the large diameter portion is 10 mm and the small diameter portion is 6 mm, so that the flow rate of (100−36) / 100 × vp = 64/100 × vp has a flow in either direction in all steps. Yes.

A feature of the embodiment of the present invention is that frictional heat generated in a plunger and a cylinder, which are sliding parts of a pump, with a flow rate of (φd ₁ ² −φd ₂ ² ) / φd ₁ ² × vp flowing in the passage 10d. To take away.

  Prior to the description of the cooling function that takes away frictional heat, the necessary area of the low-pressure passage 10d as a passage will be described.

  A large amount of fuel always flows through the low-pressure passage 10d as described above. Therefore, if the passage area is small, there arises a problem that the fuel pressure pulsation in the seal chamber 10g increases. The increase in fuel pressure pulsation in the seal chamber 10g causes the following problems.

  One is the problem of fuel vaporization. Normally, the low-pressure passage system is controlled to a pressure of about 0.4 MPa (gauge pressure), but when there is a fuel pressure change of about ± 0.4 MPa as the fuel pressure pulsation, for example, the pressure on the small side is 0 MPa and the pressure at the atmospheric pressure level. End up. At this time, the fuel is vaporized at a temperature of about 50 ° C. The vaporization of the fuel hinders the oil film shape of the fuel necessary for sliding between the cylinder 6 and the plunger 2, and causes a problem of poor lubrication.

  Further, when the vaporized fuel reaches the electromagnetically driven suction valve 30 while being partially liquefied, there is a problem that the discharge flow rate control becomes unstable due to a sudden volume change.

  Further, when the vaporized fuel reaches the pressurizing chamber 11 while being vaporized, sufficient pressurization cannot be performed, and the pump performance cannot be obtained.

  Vaporization is detrimental because it can cause erosion by cavitation in the components that make up the fuel passage.

  The second problem is that the plunger seal 13 is worn. Further, the fluctuation of the force applied to the plunger seal 13 due to the fuel pressure pulsation increases, and the sliding surface pressure between the plunger seal 13 and the plunger 2 increases to promote wear.

  It is a necessary condition to ensure the area of the low-pressure passage 10d so that such a problem does not occur. In this embodiment, the area is ensured so that the fuel pressure pulsation in the seal chamber is 0.1 MPa or less.

  In order to secure a necessary area for the low-pressure passage 10d, it may be difficult to secure a space due to the component configuration with a single passage. In addition, there is a case where it is necessary to increase the size of the parts to secure. Here, the advantage of having a plurality of passages will be described. In this embodiment, the communication passage from the seal chamber 10g to the suction passage 10c is partially configured as a passage 10d and partially configured as a plurality of passages 10f. The use of a plurality of low-pressure passages 10f has the following advantages.

  One is that the space can be reduced. When the required passage area is determined, as in this embodiment, when the passage is formed around the plunger 2 at the center of the pump, a passage having a smaller diameter than the single case is formed. The configuration with two or three is advantageous in terms of space, and the outer diameter of the pump can be reduced. However, it is necessary to increase the total area in consideration of an increase in the area of the passage wall surface per passage area and an increase in pressure loss.

  The second advantage is the reduction of the side force acting on the plunger 2. Since the flow rate flowing into and out of the seal chamber is relatively large, when there is only one passage from the seal chamber, the pressure pulsation near the portion where the passage of the seal chamber communicates increases. That is, when considering the plunger 2b as a reference, the pressure of only one of the fuels of the plunger 2b among the fuels surrounded by the plunger 2b may increase, and the pressure of the fuel on the opposite side may decrease. In this case, the plunger 2b is pushed toward one side, that is, a side force is generated in the plunger 2a, which causes the sliding with the cylinder 6 to deteriorate.

  In order to reduce the side force, by constructing two low-pressure passages 10f symmetrically from the seal chamber 10g, even if some fuel pressure pulsation occurs, a section of the plunger 2b passing through the shaft is taken into consideration The pressure difference between one side surface and the opposite side surface at a position opposed to each other by 180 degrees around the plunger 2b is considered to be relatively small.

  The third advantage is that the cooling effect of the cylinder is improved. As will be described in detail later, the cooling effect is improved by increasing the surface with which the fluid contacts the cylinder.

By the way, the volume of the seal chamber 10f will be described. Needless to say, the larger volume is generally better because the pulsation is smaller. However, due to space limitations, in this embodiment, the flow rate is 5 times or more the operating distance of 1 plunger operation process (φd ₁ ² −φd ₂ ² ) / φd ₁ ² × 1 operation process. .

  Hereinafter, the operation of the pressurizing mechanism and its problems will be described in more detail. 8 and 9 are enlarged views of the pressurizing mechanism, and FIG. 7 is a diagram intentionally enlarged to facilitate the understanding of the gap between the plunger 2 and the cylinder 6, and also shows the action of force. is there.

  When the energization of the electromagnetic drive mechanism 30A is cut off in the ascending stroke of the plunger 2 and the intake valve 31 is closed, the inside of the pressurizing chamber 11 enters the fuel pressurizing stroke. In the pressurization stroke, the fuel in the pressurizing chamber 11 is rapidly compressed and pressurized. When the inside of the pressurizing chamber 11 is pressurized to a high pressure, a force Fp acts on the plunger 2 in the axial direction of the plunger 2 as a compression reaction force so as to be sandwiched between the pressurizing chamber 11 and the lifter 3. The plunger 2 with the outer diameter φd has a diameter gap (φD−φd) of about 10 μm, for example, with respect to the cylinder 6 with the inner diameter φD, so the plunger 2 must be inclined with respect to the cylinder 6 by the diameter gap. Absent. The inclination of the plunger 2 generates lateral force components Fps1 and Fps2 of the compression reaction force. Further, at the contact point between the plunger 2 and the lifter 3, the lateral force component Fps3 acts. The lateral force components Fps1 and Fps2 of the plunger 2 are loaded on the inner surface of the cylinder 6 and the outer surface of the plunger 2, and the sliding surface pressure between the plunger 2 and the cylinder 6 increases.

  When the fuel pressure is set to a higher pressure, the compression reaction force Fp becomes larger, that is, the lateral force components Fps1 and Fps2 also increase, and the sliding surface pressure increases. As a problem of the increase in the sliding surface pressure, there is a problem that an oil film in the sliding portion cannot be secured and the slidability is deteriorated. In addition, the frictional heat generated by the relative movement between the plunger 2 and the cylinder 6 increases due to the increase of the sliding surface pressure, and the fuel having a low boiling point and high volatility is easily vaporized in the sliding portion. Accelerates the deterioration of slidability because it can cause oil film loss.

The lateral force components Fps1, Fps2, and Fps3 acting on the plunger are as follows:
Fps2 = Fps1 + Fps3
It can be seen that Fps2 acting on the cylinder lower end is larger than force Fps1 acting on the cylinder upper end. That is, it can be said that the place where the frictional heat is generated most is the lower end of the cylinder.

  In order to solve the above-described problem of deterioration of slidability, in this embodiment, a fuel passage that reduces the generation of frictional heat by causing a fluid having a positive flow to act on the lower end portion of the cylinder that generates the most frictional heat. Configure. Specifically, a groove 10f is provided on the outer periphery of the lower end of the cylinder where frictional heat is generated, and the passage is configured such that the groove 10f is connected to the passage 10d.

  It is difficult to quantify the frictional heat caused by sliding between the plunger 2 and the cylinder 6. However, the fact that there is a fact that the plunger 2 and the cylinder 6 are adhered under a certain condition due to the sliding of the plunger 2 and the cylinder 6 is actually that the temperature reaches several hundred degrees near the adhesion part. On the other hand, in the normal operation state, the fuel temperature is always sent to the pump from the fuel tank 20 to the outside air temperature. Therefore, the fuel having a temperature clearly lower than the several hundred degrees of temperature is put into the pump. Will exist. In addition, the fuel in this embodiment is gasoline, and the boiling point at the fuel pressure of 0.4 MPa at the lower end of the cylinder 6 is about 110 ° C. Considering that it is not, fuel of 110 ° C. or less exists.

  Thus, the fuel temperature is clearly lower than the temperature between the plunger 2 and the cylinder 6 where the frictional heat is generated, so that the frictional heat due to the sliding between the plunger 2 and the cylinder 6 can be taken away.

  FIG. 12 is an enlarged view of the groove 6a formed in the cylinder 6 and a formula for the amount of heat Q deprived of the generated frictional heat.

  In general, the heat transfer amount Q increases in proportion to the temperature difference between the temperature Tb of the cylinder 6 and the fuel temperature Ta, in proportion to the fourth power of the flow velocity, and in proportion to the groove width.

Q = a × ΣB × V ^4/5 × | Tb−Ta |
a: constant, B: groove width (ΣB: total of each groove width), V: flow velocity, Tb: cylinder temperature, Ta: fluid temperature What is important here is that the frictional heat is large, that is, the pump operates fast Under the conditions, since the fluid velocity is large, energy proportional to the fluid velocity (in terms of mathematical expression, strictly proportional to the 4 / 5th power) can be taken (see FIG. 14). In the present invention, the positive fluid flow generated by the plunger having the large diameter portion and the small diameter portion is used for cooling. As can be seen from these general heat transfer equations, it is clear that the speed of the fluid takes away heat.

  Although the width B of the groove will be described later, it is desirable that the width is large in terms of heat transfer. However, when the width is increased, the passage area is increased and the flow velocity is reduced, so that the effect of heat transfer is hardly expected. In that case, the groove width may be increased without changing the passage area itself. That is, although B is increased, if the height H is decreased, the flow rate does not decrease and the amount of heat transfer can be increased.

  In the case where the conventional plunger has a structure having no large-diameter portion and small-diameter portion, the volume of the seal chamber does not change due to the operation of the plunger. There is little effect because there is no.

  In order to increase the cooling effect, there is a method of increasing the number of grooves 10f in the cylinder 6 (FIGS. 16 and 17). The amount of cooling heat is increased by increasing B in the formula (1). What is necessary is just to make m dimension small so that a flow rate may not fall. This not only improves the cooling performance but also makes the pressure distribution around the plunger uniform, reduces the side force generated in the plunger, and helps prevent seizure between the plunger 2 and the cylinder 6.

  Although not shown, the groove 10f may not be formed in the cylinder 6 itself. A groove 10f may be formed in the cylinder holder 7 that surrounds and supports the cylinder. Although the cooling surface may move away from the location where the frictional heat is generated, the cylinder member generally has high rigidity and is difficult to process. Therefore, the member surrounding the cylinder may be processed. There is a merit that processing becomes easy.

  In this embodiment, the groove 10f is formed in the cylinder, and the fluid is positively applied to the cylinder as the heating element to aim at cooling drop. However, even if such a groove 10f is not formed, the fluid flows on the lower surface of the cylinder. If so, it is also possible to cool the cylinder, which is a heating element, by forming the lower surface of the cylinder in a fin shape. However, the effect is smaller than passing through the vicinity of the friction surface.

  According to the first to fourth embodiments described above, it is possible to provide a high-pressure fuel pump in which the sliding portion does not seize or bite even when the plunger sliding to the cylinder is driven at high speed.

  A plunger pump that pumps fluid can be applied not only to a high-pressure fuel pump of a direct injection internal combustion engine, but also to a water pump, a hydraulic pump, a pump for a diesel vehicle, and the like.

DESCRIPTION OF SYMBOLS 1 Pump body 2 Plunger 3 Lifter 4 Spring 5 Cam 6 Cylinder 7 Cylinder holder 8 Discharge valve mechanism 9 Metal damper 10 Low-pressure passage 11 Pressurization chamber 30 Electromagnetic drive type intake valve

Claims (2)

A cylinder combined with the pump body;
A cylinder holder that sandwiches the cylinder with the pump body;
A plunger that slides back and forth in a cylinder,
A pressurizing chamber in which fuel is pressurized by one end of the plunger;
A low-pressure fuel passage through which fuel sucked into the pressurizing chamber passes,
A low pressure fuel chamber communicating with the low pressure fuel passage and formed by the cylinder holder and a cylinder;
The outer peripheral portion of the plunger has a stepped portion having a smaller diameter than the portion that slides on the cylinder,
The stepped portion pressurizes or depressurizes the fuel in the low pressure fuel chamber, thereby discharging the fuel into the low pressure fuel passage, or sucking the fuel into the low pressure fuel chamber,
The fuel flow between the low pressure fuel chamber and the low pressure passage is configured to pass through a plurality of holes or grooves provided between the cylinder and the cylinder holder, and the holes or grooves are the center of the plunger. Symmetrically or circumferentially with respect to the axis, the fuel in the low-pressure fuel chamber is discharged and sucked through a hole symmetrically or circumferentially spaced with respect to the central axis of the plunger. High pressure fuel supply pump. In claim 1,
The high-pressure fuel supply pump in which the hole or groove is formed so that a radial dimension (H or m) from the central axis is smaller than a width (B) in a direction along the circumference of the cylinder.

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