JP2009091955A - Supply pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly secure the discharge amount of the fuel during high rotation of an engine without increasing the size of the supply pump in a supply pump wherein a plunger is reciprocatively arranged in a plunger barrel, a pressure chamber is formed between the plunger barrel and the plunger, and a first suction port and a second suction port for sucking fuel into the pressure chamber and a fuel discharge passage for discharging the fuel from the pressure chamber are arranged. <P>SOLUTION: The plunger barrel 3 has the second suction port 42 to be opposed to the top of the plunger 4 when the plunger 4 is located at a lower dead center, and a stepped portion 4a provided on the outer periphery of the top of the plunger 4 so as to be stepwisely narrower toward the top end. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a configuration of a supply pump of an accumulator fuel injection device mounted on an engine.

Conventionally, a supply pump is provided in an accumulator fuel injection device mounted on an engine, a plunger is provided in a plunger barrel so as to be reciprocable, and a pressurizing chamber is formed between the plunger barrel and the plunger, The reciprocating motion of the plunger sucks fuel into the pressurizing chamber and discharges the fuel from the pressurizing chamber (see, for example, Patent Document 1). In such a supply pump, at the time of engine start (at low speed) when the fuel supply pressure is low, the fuel suction is performed in order to secure the amount of fuel sucked from the fuel tank into the pressurizing chamber through the fuel suction passage. In some cases, a starting suction port that directly connects the passage and the pressurizing chamber (not via a check valve) is provided in addition to the normal suction port.
JP 2006-83821 A

  However, in the supply pump having the configuration including the starting intake port, the effective stroke of the plunger is reduced, so that the amount of fuel discharged is reduced. Therefore, in order to appropriately secure the fuel discharge amount at the time of high engine rotation, it is necessary to increase the size of the supply pump by increasing the diameter or stroke of the plunger.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, in the first aspect of the present invention, the plunger is provided in the plunger barrel so as to be able to reciprocate, a pressure chamber is formed between the plunger barrel and the plunger, and fuel can be sucked into the pressure chamber. In a supply pump comprising a suction port and a second suction port, and a fuel discharge passage capable of discharging fuel from the pressurizing chamber, when the plunger is positioned at the bottom dead center in the plunger barrel, the top of the plunger The second suction port is provided so as to face the outer periphery of the plunger, and a stepped portion is formed on the outer periphery of the top portion of the plunger in a stepwise manner in the top end direction.

  According to a second aspect of the present invention, the radial width of the stepped portion is set to 1% or less of the diameter of the plunger.

  According to a third aspect of the present invention, the width of the step portion in the longitudinal direction of the plunger is set to ½ or more of the opening width of the second suction port.

  The first suction port according to claim 4, wherein a plunger is provided in the plunger barrel so as to be reciprocally movable, a pressure chamber is formed between the plunger barrel and the plunger, and fuel can be sucked into the pressure chamber. And a second discharge port and a fuel discharge passage that allows fuel to be discharged from the pressurizing chamber. When the plunger is located at the bottom dead center in the plunger barrel, Thus, the second suction port is provided, and a taper portion that gradually becomes thinner in the top end direction is provided on the outer periphery of the top portion of the plunger.

  According to a fifth aspect of the present invention, the angle of the tapered portion is 5 degrees or less with respect to the longitudinal direction of the plunger, and the width of the tapered portion in the longitudinal direction of the plunger is set to 1 / of the opening width of the second suction port. Two or more.

  According to a sixth aspect of the present invention, the plunger includes a first taper portion having a large diameter portion and a small diameter portion on the bottom side of the plunger, and gradually narrowing in a bottom end direction on an outer periphery between the large diameter portion and the small diameter portion. A second taper portion that gradually decreases in the bottom end direction on the outer periphery of the bottom portion of the plunger, and the angle of each of the first taper portion and the second taper portion is 10-30 with respect to the longitudinal direction of the plunger. Less than or equal to degrees.

  In Claim 7, it has a 1st taper part which has a large diameter part and a small diameter part in the bottom part side of the said plunger, and becomes thin gradually in the bottom end direction on the outer periphery between this large diameter part and a small diameter part. The angle of the first taper portion is 10 to 30 degrees or less with respect to the longitudinal direction of the plunger, and the diameter of the bottom portion of the plunger is 85% or less of the diameter of the large diameter portion of the plunger. It is.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, when the engine is started (at the time of low rotation), the speed at which the plunger reciprocates becomes slow. It becomes possible. In addition, since the speed at which the plunger reciprocates at a high engine speed increases, the fuel sucked into the pressurizing chamber from the first suction port passes from the second suction port through the plunger barrel and the stepped portion by a dynamic effect. The fuel is not returned to the fuel supply side, and the fuel discharge amount increases. Therefore, the amount of fuel discharged at the time of high engine rotation can be ensured appropriately without increasing the size of the supply pump.

  According to the second aspect of the present invention, the amount of fuel discharged at the time of high engine rotation is set to be equivalent to that by a supply pump having no second intake port, so that the fuel can be discharged appropriately.

  According to the third aspect of the present invention, it is possible to sufficiently secure the amount of fuel sucked into the pressurizing chamber through the space between the plunger barrel and the step portion from the second suction port when the engine is started (at the time of low rotation).

  According to the fourth aspect of the present invention, when the engine is started (at the time of low rotation), the speed at which the plunger reciprocates becomes slow. Therefore, fuel is sucked from the second suction port into the pressurizing chamber through the plunger barrel and the tapered portion. It becomes possible. In addition, since the speed at which the plunger reciprocates at a high engine speed increases, the fuel sucked into the pressurizing chamber from the first suction port passes from the second suction port through the plunger barrel and the tapered portion due to a dynamic effect. The fuel is not returned to the fuel supply side, and the fuel discharge amount increases. Therefore, the amount of fuel discharged at the time of high engine rotation can be ensured appropriately without increasing the size of the supply pump. Further, the change in the fuel discharge amount with respect to the pump rotational speed becomes smoother than in the case where the step portion is used instead of the taper portion, and the control accuracy of the fuel discharge amount can be improved.

  According to the fifth aspect of the present invention, the amount of fuel discharged at the time of high engine rotation can be made equal to that by a supply pump having no second intake port so that the fuel can be discharged appropriately. Furthermore, it is possible to sufficiently secure the amount of fuel sucked into the pressurizing chamber from the second suction port through the space between the plunger barrel and the tapered portion when the engine is started (at the time of low rotation).

  According to the sixth aspect, the plunger can be inserted into the seal member without damaging the seal member.

  According to the seventh aspect, the plunger can be inserted into the seal member without damaging the seal member.

  Next, embodiments of the invention will be described.

  FIG. 1 is a front sectional view showing an overall configuration of a supply pump according to an embodiment of the present invention, FIG. 2 is a side sectional view showing an entire configuration of a supply pump according to an embodiment of the present invention, and FIG. FIG. 4 is a side view showing the configuration of the top of the plunger at the bottom dead center according to one embodiment, FIG. 4 is a side view showing the configuration of the top of the plunger at the bottom dead center according to the second embodiment, and FIG. FIG. 6 is a side view showing the state of the seal member portion during the assembly operation of the plunger, and FIG. 6A is a side view in the case where the bottom portion is provided with the second tapered portion. b) is a diagram in the case where the bottom portion has a smaller diameter than the diameter of the plunger.

  A supply pump 1 according to an embodiment of the present invention is provided in an accumulator fuel injection device mounted on an engine.

  In the supply pump 1, as shown in FIGS. 1 and 2, a plurality of plunger barrels 3 are inserted into the upper portion of the supply pump main body 2. Plungers 4 are provided in the lower portions of the plunger barrels 3 so as to be able to reciprocate in the vertical direction, and the lower portions project downward from the lower ends of the plunger barrels 3. A spring receiver 5 is disposed below the plunger barrel 3 and the plunger 4.

  The spring receiver 5 is fitted to the lower end portion of the plunger 4 that protrudes downward from the plunger barrel 3, and can reciprocate in the vertical direction together with the plunger 4. A spring 6 is interposed between the spring receiver 5 and the lower end portion of the plunger barrel 3 so as to expand and contract in the axial direction of the plunger 4, that is, in the vertical direction. It is urged downward via the receiver 5.

  Further, a tappet 7 is disposed below the plunger barrel 3 on the same axis as the plunger 4 and is provided in the supply pump main body 2 so as to reciprocate in the vertical direction. The tappet 7 has a bottomed cylindrical tappet guide 7a and a tappet roller 7b, and the tappet roller 7b is rotatably supported in the bottom of the tappet guide 7a so that the lower portion protrudes downward. Has been.

  The spring receiver 5 is fitted into the upper portion of the tappet guide 7 a of the tappet 7, and the tappet 7 is urged downward by the urging force of the spring 6 together with the plunger 4 through the spring receiver 5. By the urging by the spring 6, the tappet roller 7b of the tappet 7 is pressed against the cam 12 on the cam shaft 11 provided below the tappet roller 7b.

  The cam shaft 11 is disposed in a direction perpendicular to the axial direction of the plunger 4 and is rotatably supported at the lower portion of the supply pump main body 2. Both end portions of the cam shaft 11 protrude from the supply pump main body 2 to the side, a feed pump 15 is provided at one end thereof, and a drive gear 13 is fixed at the other end. Power is transmitted from the crankshaft of the engine to the camshaft 11 through the drive gear 13, and the camshaft 11 is rotated.

  In the supply pump main body 2, cams 12 are provided in parallel with appropriate phase differences at positions facing the respective tappets 7 of the cam shaft 11, and rotate integrally with the rotation of the cam shaft 11. The rotation of the cam 12 is performed in a state where the tappet roller 7 b of the tappet 7 is in pressure contact with the cam 12 as described above.

  A suction side check valve 21, a discharge side check valve 22, and a joint 23 are arranged on the same axis as the plunger 4 in the upper part of each plunger barrel 3. It is provided. Of these members, the joint 23 located on the upper side protrudes upward from the plunger barrel 3 and can be connected to piping or the like.

  On the other hand, a pressurizing chamber 25 is formed between the plunger barrel 3 and the plunger 4 below the suction side check valve 21 located on the lower side. The pressurizing chamber 25 communicates with a fuel tank (not shown) through a fuel suction passage 31 formed in the supply pump main body 2, the plunger barrel 3, etc., and is formed by a joint 23, a pipe connected to the joint 23, and the like. The discharge passage 32 communicates with a pressure accumulation chamber (not shown).

  The fuel suction passage 31 is provided with a feed pump 15 and a suction-side check valve 21, and fuel pumped from the fuel tank by the feed pump 15 is added from the first suction port 41 through the suction-side check valve 21. The pressure chamber 25 can be inhaled. The fuel discharge passage 32 is provided with a discharge side check valve 22, and the fuel whose pressure is increased in the pressurizing chamber 25 is discharged from the pressurizing chamber 25 through the discharge side check valve 22 and can be pumped to the pressure accumulating chamber. It is said that.

  Thus, by rotating the cam shaft 11, the feed pump 15 is driven and the cam 12 on the cam shaft 11 is rotated, and the cam 12 is moved downward by the spring 6 through the tappet 7. The biased plunger 4 is reciprocated up and down in the plunger barrel 3, whereby the intake of fuel into the pressurizing chamber 25 and the discharge of fuel from the pressurizing chamber 25 are alternately performed.

  That is, the plunger 4 is urged downward by the urging force of the spring 6 and descends from the top dead center in the plunger barrel 3 to start the fuel intake stroke. The feed pump 15 causes the fuel intake passage from the fuel tank. The fuel pressure-fed through 31 is sucked into the pressurizing chamber 25 from the first suction port 41 through the suction-side check valve 21.

  On the other hand, the plunger 4 is pushed up by the cam 12 against the urging force of the spring 6 and ascends from the bottom dead center, whereby the fuel discharge stroke is started and the fuel sucked into the pressurizing chamber 25 is pressurized. Thus, the high-pressure fuel is discharged through the discharge-side check valve 22 and is pumped to the pressure accumulating chamber through the fuel discharge passage 32.

  In the supply pump 1 having such a configuration, the plunger barrel 3 is provided with a second suction port 42 that allows the fuel to be sucked into the pressurizing chamber 25 in addition to the first suction port 41. The second suction port 42 is disposed in a direction perpendicular to the axial direction of the plunger 4, that is, in a radial direction, and is formed in the middle of the plunger barrel 3 so as to penetrate the inner peripheral surface from the outer peripheral surface thereof. Yes.

  The second suction port 42 communicates with a fuel bypass passage 45 communicating with the fuel suction passage 31 on the outer peripheral side of the plunger barrel 3. On the other hand, the second suction port 42 is located above the upper end position of the outer periphery of the plunger 4 when the plunger 4 reciprocating in the vertical direction reaches the bottom dead center on the inner peripheral side of the plunger barrel 3. It communicates with the pressurizing chamber 25. The second suction port 42 is located below the upper end position of the outer periphery of the plunger 4 and is closed by the outer peripheral surface of the plunger 4 when the plunger 4 rises a prestroke from the bottom dead center. .

  The pre-stroke here is a stroke from the bottom dead center of the plunger 4 which sucks or discharges fuel by reciprocating in the plunger barrel 3 in the supply pump 1 to the start of fuel pressure increase.

  The fuel bypass passage 45 is formed by an annular groove-like space formed between the supply pump main body 2 and the plunger barrel 3 fitted thereto, and the fuel bypass passage 45 is located upstream of the suction side check valve 21. The suction passage 31 communicates with the suction passage 31.

  Thus, the fuel pumped from the fuel tank by the feed pump 15 through the fuel suction passage 31 can be sucked into the pressurizing chamber 25 from the first suction port 41 via the suction-side check valve 21 as described above. In addition, it is possible to directly suck into the pressurizing chamber 25 from the second suction port 42 through the fuel bypass passage 45.

  Here, for example, if the second suction port 42 is not provided, the fuel supply pressure from the feed pump 15 is low when the engine is started at a low engine speed, so the pressure in the fuel suction passage 31 is reduced to the suction side check. The urging force of the spring 24 provided in the valve 21 cannot be resisted, and the fuel from the feed pump 15 may not be sucked into the pressurizing chamber 25 through the first suction port 41. For this reason, the fuel is not properly pumped to the pressure accumulating chamber, and the engine startability is unstable.

  Therefore, even when the second suction port 42 is provided as a starting suction port and fuel from the feed pump 15 is not sucked into the pressurizing chamber 25 from the first suction port 41 via the suction-side check valve 21, the second suction port 42 is provided. A part of the fuel can be sucked into the pressurizing chamber 25 by the two suction ports 42. In this way, even when the engine is started, the fuel is appropriately pumped to the pressure accumulating chamber, so that stable startability is ensured.

  By the way, in the supply pump having the second suction port serving as the starting suction port as described above, the effective stroke of the flanger is reduced, so that the amount of fuel discharged from the pressurizing chamber is reduced. . Therefore, conventionally, the amount of fuel discharged has been secured by increasing the diameter of the plunger or the stroke of the plunger.

  However, in such a configuration, there is a problem that the supply pump becomes large. Therefore, in the present invention, the supply pump 1 is kept compact and the fuel discharge amount is appropriately secured at the time of high engine rotation. The plunger 4 is configured as follows.

  As shown in FIG. 3, the plunger 4 is formed in a substantially cylindrical shape, and is slidable in the vertical direction along the inner peripheral surface of the plunger barrel 3 so as to be reciprocally movable. And in this Embodiment, the outer peripheral side becomes low and the center side of a top surface is low so that the step part 4a may become thin in steps at the outer periphery of the top part which faces the pressurizing chamber 25 of this plunger 4. It is formed in two upper and lower stages.

  A radial width L1 of the plunger 4 of the step 4a (the lower radius of the step 4a, that is, the width obtained by subtracting the upper radius of the plunger 4 from the radius of the plunger 4) is 1 of the plunger diameter D1. The width is set to be less than%. Further, the longitudinal direction (axial direction) of the plunger of the stepped portion 4a, that is, the vertical width H1 is equal to or larger than ½ of the vertical opening width d1 of the second suction port 42. Is set.

  When the plunger 4 is located at the bottom dead center, the top of the plunger 4 is provided so as to face the second suction port 42, and the step portion 4 a partially or entirely defines the second suction port 42. It is configured to face. At this time, the stepped portion 4 a is positioned above the lower end position of the opening of the second suction port 42.

  Thus, the first space 26 formed between the step portion 4 a and the inner peripheral surface of the plunger barrel 3 can communicate with the second suction port 42 in addition to the pressurizing chamber 25. That is, the pressurizing chamber 25 and the second suction port 42 can communicate with each other through the first space 26.

  Therefore, when the engine speed is low, such as when the engine is started, it is difficult for fuel to be sucked into the pressurizing chamber 25 from the first suction port 41 via the suction-side check valve 21. However, since the speed at which the plunger 4 reciprocates up and down in the plunger barrel 3 is slow, the step 4a causes the plunger 4 to descend from the top dead center to the bottom dead center during the fuel intake stroke. The formed first space 26 is communicated with the second suction port 42, and fuel is sucked into the pressurizing chamber 25 from the second suction port 42 through the first space 26.

  Further, when the engine speed becomes high, the fuel passes through the suction check valve 21 until the plunger 4 descends from the top dead center to the bottom dead center in the fuel suction stroke. While being sucked into the pressurizing chamber 25 from the first suction port 41, it is also sucked into the first space 26 formed by the stepped portion 4a.

  Before and after the plunger 4 is located at the bottom dead center, the first space 26 formed by the stepped portion 4a communicates with the second suction port 42, but the plunger 4 reciprocates in the plunger barrel 3 in the vertical direction. Therefore, the fuel sucked into the pressurizing chamber 25 and the first space 26 by the dynamic effect is held without returning from the second suction port 42 to the fuel supply side.

  Thus, in the fuel discharge stroke, the fuel increased by the amount of fuel returned from the second suction port 42 to the fuel supply side is increased in pressure and discharged from the pressurizing chamber 25 through the fuel discharge passage 32.

  As described above, the plunger 4 is provided in the plunger barrel 3 so as to be reciprocally movable, and the pressurizing chamber 25 is formed between the plunger barrel 3 and the plunger 4 so that fuel can be sucked into the pressurizing chamber 25. In the supply pump 1 including a first suction port 41 and a second suction port 42 and a fuel discharge passage 32 that allows fuel to be discharged from the pressurizing chamber 25, the plunger 4 is placed at the bottom dead center in the plunger barrel 3. When the engine is started, the second suction port 42 is provided so as to face the top of the plunger 4 and the step 4a is formed on the outer periphery of the plunger in a stepwise manner in the top end direction. At the time of low rotation, the speed at which the plunger 4 reciprocates slows down, so that the fuel is supplied from the second suction port 42 to the pressurizing chamber 25 between the plunger barrel 3 and the stepped portion 4a. It is possible to enter. Further, since the speed at which the plunger 4 reciprocates during high engine speed increases, the fuel sucked into the pressurizing chamber 25 from the first suction port 41 passes between the plunger barrel 3 and the stepped portion 4a by a dynamic effect. The fuel is not returned from the second suction port 42 to the fuel supply side, and the amount of fuel discharged is increased by the increase in the effective stroke. Therefore, the amount of fuel discharged at the time of high engine rotation can be ensured appropriately without increasing the size of the supply pump 1.

  Further, in the supply pump 1, since the radial width L1 of the plunger 4 of the stepped portion 4a is 1% or less of the diameter D1 of the plunger 4, the amount of fuel discharged at the time of high engine rotation is reduced. The fuel can be appropriately discharged as equivalent to that of a supply pump having a configuration not including the second suction port 42.

  Further, in the supply pump 1, the longitudinal width H1 of the plunger 4 of the stepped portion 4a is set to be 1/2 or more of the opening width d1 of the second suction port 42. A sufficient amount of fuel is sucked into the pressurizing chamber 25 from the second suction port 42 through the space between the plunger barrel 3 and the stepped portion 4a.

  Moreover, the plunger 4 can also be comprised as follows.

  As shown in FIG. 4, the plunger 4 is formed in a substantially cylindrical shape, and is slidable in the vertical direction along the inner peripheral surface of the plunger barrel 3 so as to be reciprocally movable. And the taper part 4b is formed in the taper shape on the outer periphery of the top part which faces the pressurization chamber 25 of this plunger 4 so that it may become thin gradually in the top end direction.

  The angle θ1 of the tapered portion 4b is set to be 5 degrees or less with respect to the longitudinal direction (axial direction) of the plunger 4, that is, the vertical direction. Further, the vertical width H2 of the tapered portion 4b is set to be equal to or larger than ½ of the vertical opening width d1 of the second suction port 42.

  When the plunger 4 is located at the bottom dead center, the top portion of the plunger 4 is provided so as to face the second suction port 42, and the taper portion 4 b partially or entirely defines the second suction port 42. It is configured to face. At this time, the tapered portion 4 b is positioned above the lower end position of the opening of the second suction port 42.

  Thus, the second space 27 formed between the tapered portion 4 b and the inner peripheral surface of the plunger barrel 3 can communicate with the second suction port 42 in addition to the pressurizing chamber 25. That is, the pressurizing chamber 25 and the second suction port 42 can communicate with each other through the second space 27.

  Therefore, when the engine speed is low, such as when the engine is started, it is difficult for fuel to be sucked into the pressurizing chamber 25 from the first suction port 41 via the suction-side check valve 21. However, since the speed at which the plunger 4 reciprocates up and down in the plunger barrel 3 is slow, the taper portion 4b causes the plunger 4 to descend from the top dead center to the bottom dead center during the fuel intake stroke. The formed second space 27 communicates with the second suction port 42, and fuel is sucked into the pressurizing chamber 25 from the second suction port 42 through the second space 27.

  Further, when the engine speed becomes high, the fuel passes through the suction check valve 21 until the plunger 4 descends from the top dead center to the bottom dead center in the fuel suction stroke. While being sucked into the pressurizing chamber 25 from the first suction port 41, it is also sucked into the second space 27 formed by the tapered portion 4b.

  Before and after the plunger 4 is located at the bottom dead center, the second space 27 formed by the tapered portion 4b communicates with the second suction port 42, but the plunger 4 reciprocates in the plunger barrel 3 in the vertical direction. Therefore, the fuel sucked into the pressurizing chamber 25 and the second space 27 by the dynamic effect is held without being returned from the second suction port 42 to the fuel supply side.

  Thus, in the fuel discharge stroke, the fuel increased by the amount of fuel returned from the second suction port 42 to the fuel supply side is increased in pressure and discharged from the pressurizing chamber 25 through the fuel discharge passage 32.

  As described above, the plunger 4 is provided in the plunger barrel 3 so as to be reciprocally movable, and the pressurizing chamber 25 is formed between the plunger barrel 3 and the plunger 4 so that fuel can be sucked into the pressurizing chamber 25. In the supply pump 1 including a first suction port 41 and a second suction port 42 and a fuel discharge passage 32 that allows fuel to be discharged from the pressurizing chamber 25, the plunger 4 is placed at the bottom dead center in the plunger barrel 3. When the engine is started, the second intake port 42 is provided so as to face the top of the plunger 4 and the outer periphery of the top of the plunger 4 is provided with a tapered portion 4b that gradually decreases in the direction of the top end. During low rotation, the speed at which the plunger 4 reciprocates slows down, so that fuel is pressurized from the second intake port 42 through the plunger barrel 3 and the tapered portion 4b. It is possible to suction 25. Further, since the speed at which the plunger 4 reciprocates during high engine speed increases, the fuel sucked into the pressurizing chamber 25 from the first suction port 41 passes between the plunger barrel 3 and the tapered portion 4b by a dynamic effect. The fuel is not returned from the second suction port 42 to the fuel supply side, and the amount of fuel discharged is increased by the increase in the effective stroke. Therefore, the amount of fuel discharged at the time of high engine rotation can be ensured appropriately without increasing the size of the supply pump 1. Further, the change in the fuel discharge amount with respect to the pump rotational speed becomes smoother than in the case where the stepped portion 4a is used instead of the tapered portion 4b as described above, and the control accuracy of the fuel discharge amount can be improved. .

  In the supply pump 1, the angle θ1 of the taper portion 4b is set to 5 degrees or less with respect to the longitudinal direction of the plunger 4, and the width H2 of the taper portion 4b in the longitudinal direction of the plunger 4 is set to the second length. Since the suction port 42 is set to be 1/2 or more of the opening width d1 of the intake port 42, the amount of fuel discharged at the time of high engine rotation is equivalent to that of a supply pump having a configuration without the second intake port 42, and the fuel is appropriately supplied. It can be discharged. Further, it is possible to secure a sufficient amount of fuel sucked into the pressurizing chamber 25 from the second suction port 42 through the space between the plunger barrel 3 and the taper portion 4b when the engine is started (at low speed).

  The plunger 4 is configured as follows on the bottom side.

  As shown in FIG. 5A, on the bottom side of the plunger 4, a small diameter portion 4 c is provided below the large diameter portion 4 d forming the plunger body so that the small diameter portion 4 c can be fitted to the spring receiver 5. A first taper portion 4e is formed on the outer periphery between the small diameter portion 4c and the large diameter portion 4d above the small diameter portion 4c. Further, a second taper portion 4f that is gradually narrowed in the bottom end direction is formed on the outer periphery of the bottom portion located below the small diameter portion 4c of the plunger 4.

  The angle θ2 of the first taper portion 4e is set to be 10 to 30 degrees or less with reference to the longitudinal direction (axial direction) of the plunger 4, that is, the vertical direction. Further, the angle θ3 of the second taper portion 4f is set to be 10 to 30 degrees or less with reference to the longitudinal direction (axial direction) of the plunger 4, that is, the vertical direction.

  Note that the bottom portion of the plunger 4 has a diameter D2 of the bottom portion, as shown in FIG. 5B, instead of setting the angle θ3 of the second taper portion 4f to be 10 to 30 degrees or less as described above. Can be configured to be set to 85% or less of the diameter of the large diameter portion 4d, that is, the diameter D1 of the plunger 4.

  As shown in FIG. 6, a seal member 51 is provided at the lower part of the plunger barrel 3 provided with the plunger 4. The seal member 51 is formed in a double cylinder shape by connecting the outer cylinder part 51a and the inner cylinder part 51b. The outer cylinder part 51a is fitted to the lower part of the plunger barrel 3 from below, and the inner cylinder part 51b penetrates the plunger 4 protruding downward from the plunger barrel 3, and a seal lip part 51c provided in the inner cylinder part 51b. -51d is provided so that it may closely_contact | adhere with the large diameter part 4d of the plunger 4. FIG.

  In the configuration in which the fuel leaking from the pressurizing chamber 25 through the space between the plunger barrel 3 and the plunger 4 is sealed by the seal member 51 provided in this way, the lower portion of the plunger barrel 3 is sealed when the plunger 4 is assembled. The procedure is determined so that the plunger 4 is inserted into the plunger barrel 3 and the seal member 51 in a state where the member 51 is fitted.

  Conventionally, when assembling the plunger, since the procedure is generally set so that the plunger is inserted into the plunger barrel and the seal member from below, in order to prevent the seal member from being damaged by the plunger, A large taper portion was formed. However, since the stepped portion and the like are formed on the outer periphery of the top portion of the plunger according to the present invention as described above, the shape thereof is limited, and in order to prevent the seal member from being damaged by the plunger, the plunger 4 Had to be inserted from above.

  Therefore, as described above, the second taper portion 4f is provided on the outer periphery of the bottom portion of the plunger 4, and the first taper portion 4e is provided on the outer periphery between the small diameter portion 4c and the large diameter portion 4d. When inserting in the direction of the pull-out arrow, the plunger 4 can be easily inserted from the bottom into the opening of the inner cylinder portion 51b of the seal member 51 so that the seal member 51 can be prevented from being damaged when the plunger 4 is inserted. ing.

  Thus, in the supply pump 1, the plunger 4 has the large-diameter portion 4d and the small-diameter portion 4c, and the outer periphery between the large-diameter portion 4d and the small-diameter portion 4c is gradually narrowed toward the bottom end. A first taper portion 4e, and a second taper portion 4f that gradually decreases in the bottom end direction on the outer periphery of the bottom portion of the plunger 4, and each angle θ2 · of each of the first taper portion 4e and the second taper portion 4f. Since θ3 is set to 10 to 30 degrees or less with respect to the longitudinal direction of the plunger 4, the plunger 4 can be inserted into the seal member 51 without damaging the seal member 51.

  In the supply pump 1, the plunger 4 has a large-diameter portion 4d and a small-diameter portion 4c, and the outer diameter between the large-diameter portion 4d and the small-diameter portion 4c is gradually narrowed toward the bottom end. A taper portion 4e is provided, and the angle θ2 of the first taper portion 4e is set to 10 to 30 degrees or less with respect to the longitudinal direction of the plunger 4, and the diameter D2 of the bottom portion of the plunger 4 is set to By setting the diameter of the large diameter portion 4d to 85% or less of the diameter D1 of the plunger 4, the plunger 4 can be inserted into the seal member 51 without damaging the seal member 51.

1 is a front cross-sectional view showing an overall configuration of a supply pump according to an embodiment of the present invention. The side sectional view showing the whole supply pump composition concerning one example of the present invention. The side view which showed the structure of the top part of the plunger in the bottom dead center which concerns on a 1st Example. The side view which showed the structure of the top part of the plunger in the bottom dead center which concerns on a 2nd Example. The side view which showed the structure of the bottom part of a plunger. (A) The side view in the case of providing a 2nd taper part in a bottom part. (B) The figure at the time of making a bottom part a small diameter compared with the diameter of a plunger. The side view which showed the state of the seal member part at the time of the assembly | attachment operation | work of a plunger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supply pump 3 Plunger barrel 4 Plunger 4a Step part 4b Tapered part 4c Small diameter part 4d Large diameter part 4e 1st taper part 4f 2nd taper part 25 Pressurization chamber 41 1st suction port 42 2nd suction port

Claims (7)

A first suction port and a second suction port which are provided in a plunger barrel so as to be capable of reciprocating, a pressure chamber is formed between the plunger barrel and the plunger, and fuel can be sucked into the pressure chamber; In a supply pump comprising a fuel discharge passage capable of discharging fuel from the pressurizing chamber,
The plunger barrel is provided with the second suction port so as to be opposed to the top of the plunger when the plunger is located at the bottom dead center, and a stepped portion that gradually decreases in the top end direction on the outer periphery of the top of the plunger. A supply pump characterized by comprising:   The supply pump according to claim 1, wherein a width of the step portion in the radial direction of the plunger is 1% or less of a diameter of the plunger.   3. The supply pump according to claim 1, wherein a width of the step portion in the longitudinal direction of the plunger is equal to or greater than ½ of an opening width of the second suction port. A first suction port and a second suction port which are provided in a plunger barrel so as to be capable of reciprocating, a pressure chamber is formed between the plunger barrel and the plunger, and fuel can be sucked into the pressure chamber; In a supply pump comprising a fuel discharge passage capable of discharging fuel from the pressurizing chamber,
The plunger barrel is provided with the second suction port so as to face the top of the plunger when the plunger is located at the bottom dead center, and is provided with a tapered portion that gradually decreases in the top end direction on the outer periphery of the top of the plunger. Supply pump characterized by that.   The angle of the taper portion is 5 degrees or less with respect to the longitudinal direction of the plunger, and the width of the taper portion in the longitudinal direction of the plunger is ½ or more of the opening width of the second suction port. The supply pump according to claim 4, wherein   The plunger has a large-diameter portion and a small-diameter portion on the bottom side of the plunger, and includes a first taper portion that gradually decreases in the bottom end direction on the outer periphery between the large-diameter portion and the small-diameter portion. A second taper portion that gradually decreases in the bottom end direction on the outer periphery, and each angle of the first taper portion and the second taper portion is set to 10 to 30 degrees or less with respect to the longitudinal direction of the plunger. The supply pump according to any one of claims 1 to 5, wherein the supply pump is characterized.   A first tapered portion having a large diameter portion and a small diameter portion on a bottom side of the plunger, and having a first taper portion gradually narrowing in a bottom end direction on an outer periphery between the large diameter portion and the small diameter portion; The angle is set to 10 to 30 degrees or less with respect to the longitudinal direction of the plunger, and the diameter of the bottom portion of the plunger is set to 85% or less of the diameter of the large diameter portion of the plunger. The supply pump according to any one of claims 1 to 5.

Images