JP5592148B2 - Fuel injection pump - Google Patents

Description

  The present invention relates to a fuel injection pump, and more particularly to a technique for improving the durability of a plunger.

  2. Description of the Related Art Conventionally, a plunger that moves up and down by power transmitted from a crankshaft of an engine and a plunger barrel that accommodates the plunger so as to be movable up and down are defined by an upper surface of the plunger and an inner peripheral surface of the plunger barrel. There is known a fuel injection pump in which the above space constitutes a pressurizing chamber for pressurizing fuel. For example, as described in Patent Document 1.

  The plunger provided in the fuel injection pump described in Patent Document 1 is coated with a coating material mainly composed of carbon over the entire outer periphery. With this configuration, in the fuel injection pump described in Patent Document 1, the conformability and the lubrication function between the outer peripheral surface of the plunger and the inner peripheral surface of the plunger barrel are improved. This prevents wear and seizure of the contact surface. However, when the technique for applying the coating process is applied to a conventional fuel injection pump, the dimension of the clearance (gap) between the plunger and the plunger barrel in the upper portion of the plunger is changed from the conventional state. . Therefore, the amount of fuel leaking from the pressurizing chamber becomes different from the conventional one, and the way in which the fuel is pressurized becomes different from the conventional one. As a result, the fuel injection characteristics are changed. Become. For this reason, when the coating process is performed on the plunger, it is necessary to review various setting items related to the fuel injection characteristics such as the shape and size of the plunger and the plunger barrel, and the engine speed.

JP 2007-2776 A

  The present invention has been made in view of the circumstances as described above, and improves the durability of the plunger without changing the fuel injection characteristics of the conventional fuel injection pump, and wear of the contact surface between the plunger and the plunger barrel. And a fuel injection pump capable of suppressing seizure.

The invention according to one aspect of the present invention includes a plunger that moves up and down by power transmitted from a crankshaft, and a plunger barrel that accommodates the plunger so that the plunger can be moved up and down. The upper surface of the plunger and the plunger barrel In the fuel injection pump in which the space partitioned by the inner peripheral surface of the fuel pump constitutes a pressurizing chamber for pressurizing the fuel, the pressurizing chamber is depressurized on the outer periphery of the upper and lower middle portions of the plunger. A groove is formed on the outer peripheral surface of the plunger, and the dimension of the outer diameter of the plunger and the film thickness of the coating film below the groove is larger than that of the groove. The dimension is set to be larger than the combined dimension of the outer diameter of the plunger on the upper side and the film thickness of the coating film .

  The present invention has an effect that the durability of the plunger can be improved and wear and seizure of the contact surface between the plunger and the plunger barrel can be suppressed without changing the fuel injection characteristics of the conventional fuel injection pump. Play.

It is a figure which shows the whole structure of the fuel injection pump which concerns on a 1st structure form. It is a schematic diagram which shows the plunger with which the fuel injection pump which concerns on a 1st structure form is equipped, (a) is a figure which shows the area | region in which the coating film was formed, (b) is a figure which shows the structure of the periphery of a groove part. . It is a schematic diagram which shows the plunger with which the fuel injection pump which concerns on 1st embodiment is equipped, (a) is a figure which shows the area | region in which the coating film was formed, (b) is a figure which shows the structure around a groove part. . It is a schematic diagram which shows the plunger with which the fuel injection pump which concerns on a 2nd structure form is equipped, (a) is a figure which shows the area | region in which the coating film was formed, (b) is a figure which shows the structure of the periphery of a groove part. .

Hereinafter, preferred embodiments and configuration forms of the present invention will be described with reference to the accompanying drawings.

<First configuration form>
The overall configuration of a fuel injection pump 1 according to the first configuration mode will be explained with reference to FIG. In the present specification, the axial direction of the cam shaft 11 is defined as the front-rear direction, the side on which the cam 12 is disposed is defined as the rear, the axial direction of the plunger 31 is defined as the up-down direction, and the pressurizing chamber 32a is provided. The description will be given with the side to be formed defined as the upper side.

  The fuel injection pump 1 is a device provided in a fuel injection device of an engine, and pumps fuel to a fuel injection nozzle. The fuel injection pump 1 is configured by vertically joining an upper housing 30 that is an upper structure and a lower housing 10 that is a lower structure.

  A tappet 14 and the like are assembled to the lower housing 10.

  The cam shaft 11 is rotatably spanned in the cam chamber of the lower housing 10 with its axial direction being parallel to the front-rear direction. The camshaft 11 is rotated by transmitting rotational power from the crankshaft of the engine. The cam 12 is provided at the rear portion of the cam shaft 11 and rotates integrally with the cam shaft 11.

  The tappet 14 is fitted into a tappet hole 10 a formed in the lower housing 10. The tappet 14 can move up and down in the tappet hole 10a. The lower surface of the tappet 14 is in contact with the outer peripheral surface of the cam 12 via a roller (not shown). The rotational force of the cam shaft 11 is converted into a lifting motion by the cam 12 and transmitted to the tappet 14.

  The upper housing 30 is assembled with a plunger 31, a plunger barrel 32, a lower spring receiver 33, an upper spring receiver 34, a plunger spring 35, a control sleeve 36, and the like.

  The plunger 31 is a substantially cylindrical member. The plunger 31 is disposed above the tappet 14 while being fitted to the plunger barrel 32. The plunger 31 has lead portions 31a and 31a, a land portion 31b, a groove portion 31c, and the like.

A land portion 31b is formed on the plunger 31, and lead portions 31a and 31a are formed on the outer periphery of the land portion 31b. The lead portions 31a and 31a are grooves formed in a short spiral shape along the circumferential direction of the outer peripheral surface of the land portion 31b, and are formed at two locations on the outer periphery (side wall) of the land portion 31b. Each lead portion 31 a is formed symmetrically with respect to the axis of the plunger 31. The groove portion 31 c is a ring-shaped (ring-shaped) groove, and is formed on the outer periphery of the middle portion of the plunger 31. The groove part 31c of this configuration form is formed below the land part 31b. The radial dimension of the portion of the plunger 31 where the groove 31c is formed is smaller (reduced) than the radial dimension of the other portion of the plunger 31.

  The plunger barrel 32 is a substantially cylindrical member having a columnar cavity formed in the center. The plunger barrel 32 is fixed to the upper housing 30 and the lower housing 10 with the axial direction thereof being parallel to the vertical direction. A plunger 31 is fitted into the cylindrical cavity of the plunger barrel 32. The plunger 31 can slide in the axial direction along the inner peripheral surface of the plunger barrel 32 and can rotate in the circumferential direction. In other words, the plunger 31 can move up and down in the cylindrical cavity of the plunger barrel 32 and can rotate.

  A space defined by the upper surface of the plunger 31 and the inner peripheral surface of the cylindrical cavity of the plunger barrel 32 constitutes a pressurizing chamber 32a for pressurizing the fuel. A space defined by the outer peripheral surface of the groove 31c of the plunger 31 and the inner peripheral surface of the plunger barrel 32 forms an annular space. The ring-shaped space (the space formed by the groove portion 31c) is for decompressing the inside of the pressurizing chamber 32a. The pressure in the pressurizing chamber 32a after fuel injection is released to the outside through the groove 31c.

As shown in FIG. 2, a coating film 37 is formed on the contact surface (slide surface) between the plunger 31 and the plunger barrel 32. In the first configuration , the coating film 37 is formed on a portion (region) located below the groove 31c on the outer peripheral surface of the plunger 31 (see FIG. 2A). More specifically, the coating film 37 of this configuration form is a film formed by DLC (abbreviation of diamond-like carbon; hereinafter referred to as “DLC”). The coating film 37 is produced, for example, by applying a coating process to the plunger 31 by a high-frequency plasma CVD (chemical vapor deposition) method using methane (CH 4) as a raw material or a sputtering method. On the other hand, the coating film 37 is not formed on the portion (region) located on the upper side of the groove 31c in the outer peripheral surface of the plunger 31 (the coating process is not performed). Such a configuration can be realized, for example, by masking the upper side (non-processed portion) of the plunger 31 during the coating process.

  The lower spring receiver 33 shown in FIG. 1 is accommodated in the bottom portion of the tappet 14 in a state of being engaged with the lower end portion of the plunger 31 so as to be relatively rotatable. The upper spring receiver 34 is fitted to the plunger 31 so as to be relatively rotatable, and is disposed at a position above the lower spring receiver 33.

  The plunger spring 35 surrounds the outer periphery of the plunger 31 and is attached so as to be interposed between the lower spring receiver 33 and the upper spring receiver 34. The plunger 31 is urged in the downward direction by the urging force received from the plunger spring 35. With such a configuration, the lower end portion of the plunger 31 is pressed against the bottom portion of the tappet 14 via the lower spring receiver 33. Therefore, the plunger 31 moves up and down in the cylindrical cavity of the plunger barrel 32 in conjunction with the up and down movement of the tappet 14.

  The control sleeve 36 is a substantially cylindrical member, and is interposed between the plunger barrel 32 and the upper spring receiver 34. The control sleeve 36 is fitted (externally fitted) to the plunger barrel 32 so as to be relatively rotatable, and a lower portion thereof is engaged with a lower portion of the plunger 31. More specifically, an engaging portion 31g is provided at the lower portion of the plunger 31 (a predetermined distance above the lower end), and the engaging portion 31g engages with an engaging groove formed at the lower portion of the control sleeve 36. Is done. Specifically, the engaging portion 31g is formed to project from the lower portion of the plunger 31 in the diametrical direction in a plan view oval shape. The engagement groove is formed by notching a part of the side wall of the control sleeve 36 upward from the lower end. The engaging portion 31g is engaged with the engaging groove from below. With such a configuration, the control sleeve 36 cannot rotate relative to the plunger 31 and can move up and down in the axial direction within a predetermined range.

  A pinion gear is formed on the outer periphery of the upper portion of the control sleeve 36, and the pinion gear meshes with a rack gear formed on the control rack 38 (a rack and pinion mechanism is configured). The control rack 38 is interlocked with the actuator. By actuating the actuator, the control sleeve 36 is appropriately rotated through the control rack 38, the positions of the lead portions 31a and 31a of the plunger 31 are changed, and the amount of fuel supplied to the pressurizing chamber 32a is adjusted accordingly. can do.

  An engine equipped with the fuel injection pump 1 is provided with a supply pump (not shown). The supply pump is a pump for supplying fuel to the pressurizing chamber 32a, and is driven in conjunction with the rotation of the crankshaft of the engine. The fuel stored in the fuel tank of the engine is supplied to suction ports 32b and 32b formed in the plunger barrel 32 by driving the supply pump. The plunger 31 is moved up and down to an appropriate position and rotated in the circumferential direction to an appropriate position, whereby the lead portions 31a and 31a communicate with the suction ports 32b and 32b. In this way, by adjusting the positions of the lead portions 31a and 31a of the plunger 31 via the control sleeve 36, the way in which the fuel is pressurized in the pressurizing chamber 32a is adjusted, and as a result, it is pumped to the fuel injection nozzle. It is possible to adjust the amount of fuel to be adjusted.

  That is, the suction ports 32 b and 32 b are opened and closed by the land portion 31 b of the plunger 31. Specifically, when the land portion 31b is in a position facing the suction ports 32b and 32b, the openings of the suction ports 32b and 32b are closed by the land portion 31b, so that no fuel is supplied to the pressurizing chamber 32a. Become. On the other hand, when the land portion 31b is located away from the suction ports 32b and 32b, the openings of the suction ports 32b and 32b communicate with the pressurization chamber 32a, so that fuel is supplied (intake) to the pressurization chamber 32a. It becomes a state.

  The fuel injection pump 1 configured as described above operates as follows. That is, when the cam shaft 11 rotates, the tappet 14 moves up and down in the tappet hole 10a. That is, the rotational force of the cam shaft 11 is transmitted to the tappet 14 as a rising force. Along with this, the plunger 31 moves up and down in the columnar cavity of the plunger barrel 32. When the plunger 31 moves in the downward direction, the volume of the pressurizing chamber 32a increases and the pressure in the pressurizing chamber 32a decreases. When the plunger 31 is lowered until the suction ports 32b and 32b and the pressurizing chamber 32a communicate with each other, fuel is supplied into the pressurizing chamber 32a. When the plunger 31 moves in the upward direction and the suction ports 32b and 32b are not in communication with the pressurizing chamber 32a, the volume of the pressurizing chamber 32a decreases and the pressure in the pressurizing chamber 32a increases. The fuel in the pressurizing chamber 32a thus pressurized is injected from the fuel injection nozzle.

  Hereinafter, the contact between the plunger 31 and the plunger barrel 32 in the case where the technique for forming the coating film 37 on the plunger 31 is applied to a conventional fuel injection pump (a fuel injection pump including a plunger that has not been subjected to a coating process). The state of the surface will be described in detail with reference to FIGS. 2 (a) and 2 (b).

  As shown in FIGS. 2A and 2B, the outer peripheral surface of the plunger 31 is coated with a coating film 37 in a region below the groove 31 c. Therefore, compared to the conventional fuel injection pump, the outer peripheral surface of the lower portion of the plunger 31 (below the groove portion 31c of the plunger 31; hereinafter referred to as “plunger lower portion”), the inner peripheral surface of the plunger barrel 32, The clearance dimension L can be reduced by the film thickness (thickness) X of the coating film 37. Therefore, it is possible to reduce the amount of fuel leaking from the groove portion 31c to the tappet 14 side (lower side) through the space between the outer peripheral surface of the plunger 31 and the inner peripheral surface of the plunger barrel 32. The amount of fuel mixed into the lubricating oil can also be reduced. The fuel leaking from the groove portion 31 c to the tappet 14 side is collected in the collection tank via the oil drain path formed in the plunger barrel 32. Or it is good also as a structure which is supplied to suction port 32b * 32b again after performing a centrifugal process etc. FIG.

  In general, a coating film by DLC has a very smooth film surface and a very low coefficient of friction. Therefore, when the coating film 37 made of DLC is formed on the plunger 31, the plunger barrel 32, which is a sliding counterpart, is not easily worn, and the plunger 31 itself is not easily worn. Therefore, even if the dimension L of the clearance between the outer peripheral surface of the lower portion of the plunger 31 and the inner peripheral surface of the plunger barrel 32 is set small, seizure of the contact surface between the plunger 31 and the plunger barrel 32 hardly occurs. . It should be noted that the film thicknesses X, Y, and Z of the coating films 37, 57, and 67 shown in the drawing are expressed to be considerably thicker than the actual thickness for easy understanding. Similarly, the size of the clearance shown in the drawing is also expressed larger than the actual size.

As shown in FIG. 2B, the outer peripheral surface of the plunger 31 is not coated in the region above the groove 31c. Therefore, the outer peripheral surface of the upper portion of the plunger 31 (above the groove portion 31c of the plunger 31. This configuration form corresponds to the land portion 31b. Hereinafter, referred to as “plunger upper portion”) and the inner peripheral surface of the plunger barrel 32. The clearance dimension S between and is the same as before. Therefore, the amount of fuel leaking from the pressurizing chamber 32a and the lead portion 31a to the groove portion 31c through the space between the outer peripheral surface of the plunger 31 and the inner peripheral surface of the plunger barrel 32 is the same as before. As a result, the fuel injection characteristic is maintained in the previous state.

As described above, the fuel injection pump 1 according to the first configuration includes the plunger 31 that moves up and down by the power transmitted from the crankshaft, and the plunger barrel 32 that accommodates the plunger 31 so as to be movable up and down. In the fuel injection pump in which the space defined by the upper surface of the plunger barrel 32 and the inner peripheral surface of the plunger barrel 32 constitutes a pressurizing chamber 32a for pressurizing the fuel, A groove 31c for reducing the pressure of the pressure chamber 32a is formed, and a coating film 37 is formed on a portion of the outer peripheral surface of the plunger 31 located below the groove 31c.

  With this configuration, the durability of the lower portion of the plunger 31 is improved, wear on the contact surface between the plunger 31 and the plunger barrel 32 is minimized, and eventually the contact surface between the plunger 31 and the plunger barrel 32 is seized. Can be prevented. In addition, the clearance dimension L between the outer peripheral surface of the plunger 31 and the inner peripheral surface of the plunger barrel 32 at the lower portion of the plunger 31 can be set small, thereby reducing the downward leakage of the fuel groove 31c. can do. On the other hand, since the clearance dimension S between the outer peripheral surface of the plunger 31 and the inner peripheral surface of the plunger barrel 32 at the upper portion of the plunger 31 is the same as before, the present invention can be used without changing the fuel injection characteristics. It is possible to apply the invention to a conventional fuel injection pump. Further, since the coating film 37 is not formed on the upper portion of the plunger 31, there is no possibility that the coating film 37 is peeled off by an impact (impact pressure) when the fuel supplied to the pressurizing chamber 32 a collides with the upper portion of the plunger 31. Therefore, there is no problem that the operator feels uneasy when the coating film 37 peeled off by cavitation stands out during maintenance.

< First embodiment>
Below, the structure of the fuel injection pump 2 which concerns on 1st embodiment of this invention is demonstrated with reference to FIG. The fuel injection pump 2 is different from the fuel injection pump 1 according to the first embodiment in that a plunger 51 is provided instead of the plunger 31. In addition, in the following description, the same code | symbol is attached | subjected about the member similar to the member comprised in the fuel injection pump 1 which concerns on a 1st structure form, and the point of a shape, a material, and a function, and the description is abbreviate | omitted. . The description of the second configuration form described later is similarly omitted as appropriate.

  The plunger 51 is a substantially cylindrical member. The plunger 51 is formed with a lead portion 31a, a land portion 31b, a groove portion 31c, and the like. The outer diameter of the plunger 51 below the groove 31c is larger than the outer diameter of the plunger 51 above the groove 31c.

In the first embodiment, the outer diameter of the upper part of the plunger 51 is such that the dimension E when added to the film thickness Y of the coating film 57 described later is the same as the dimension D of the outer diameter of the previous plunger upper part. Set to That is, as shown in FIGS. 2 and 3, the outer diameter dimension E of the upper part of the plunger 51 after the coating process is set to be the same dimension D as the outer diameter of the previous plunger upper part (E = D). . The plunger 51 is fitted into the plunger barrel 32. The plunger 51 can move up and down in the axial direction along the inner peripheral surface of the plunger barrel 32 and can rotate in the circumferential direction.

  As shown in FIG. 3, a coating film 57 is formed on the contact surface between the plunger 51 and the plunger barrel 32. In the present embodiment, the coating film 57 is formed on both the portion above the groove 31c and the portion below the groove 31c on the outer peripheral surface of the plunger 51. The coating film 57 of this embodiment is a film formed by DLC. In the present embodiment, the groove portion 31c is configured not to be coated, but the present invention is not limited to this, and the coating film 57 may be formed on the outer peripheral surface of the groove portion 31c.

  Below, the case where the technique which forms the coating film 57 in the plunger 51 is applied to the conventional fuel injection pump is demonstrated in detail with reference to Fig.3 (a) and FIG.3 (b).

  In the region below the groove 31 c, the outer peripheral surface of the plunger 51 is coated with the coating film 57. Therefore, the clearance dimension M between the outer peripheral surface of the lower portion of the plunger 51 and the inner peripheral surface of the plunger barrel 32 is made smaller by the film thickness Y of the coating film 57 than in the conventional fuel injection pump. Can do. Further, seizure of the contact surface between the plunger 51 and the plunger barrel 32 can be prevented. The outer peripheral surface of the plunger 51 is also coated with the coating film 57 in the region above the groove 31c. Therefore, seizure of the contact surface between the plunger 51 and the plunger barrel 32 can be prevented.

  Here, in the fuel injection pump 2 of the present embodiment, the dimension E that combines the outer diameter of the upper portion of the plunger 51 and the film thickness Y of the coating film 57 is the dimension D (see FIG. 2 (a)). Therefore, the amount of fuel leaking from the pressurizing chamber 32a and the lead portion 31a to the groove portion 31c through the space between the outer peripheral surface of the plunger 51 and the inner peripheral surface of the plunger barrel 32 is the same as before. The injection characteristics are maintained in the previous state.

  In the present embodiment, the dimension E when the outer diameter of the upper part of the plunger 51 and the film thickness Y of the coating film 57 are added is the same as the dimension D of the outer diameter of the previous plunger upper part. To be set to However, the present invention is not limited to this. For example, the clearance T between the outer peripheral surface of the upper portion of the plunger 51 and the inner peripheral surface of the plunger barrel 32 is set so that the amount of fuel leaking from the pressurizing chamber 32a (and the lead portion 31a) to the groove portion 31c is the conventional amount. It may be changed within a range in which the amount of leakage is not significantly changed.

As described above, the fuel injection pump 2 according to the first embodiment of the present invention includes the plunger 51 that moves up and down by the power transmitted from the crankshaft, and the plunger barrel 32 that accommodates the plunger 51 so as to be movable up and down. In the fuel injection pump in which the space defined by the upper surface of the plunger 51 and the inner peripheral surface of the plunger barrel 32 constitutes a pressurizing chamber 32a for pressurizing the fuel, Is formed with a groove 31c for depressurizing the pressurizing chamber 32a, a coating film 57 is formed on the outer peripheral surface of the plunger 51, and the outer diameter of the plunger 51 and the film of the coating film 57 below the groove 31c. The dimension combined with the thickness is the dimension combined with the outer diameter of the plunger 51 and the film thickness of the coating film 57 above the groove 31c. Remote, it is set large, those.

  With this configuration, the durability of the plunger 51 is improved, wear of the contact surface between the plunger 51 and the plunger barrel 32 is minimized, and eventually the contact surface between the plunger 51 and the plunger barrel 32 is seized. Can be prevented. Moreover, the dimension M of the clearance between the outer peripheral surface of the plunger 51 and the inner peripheral surface of the plunger barrel 32 at the lower portion of the plunger 51 can be set small, and the leakage downward from the groove portion 31c of the fuel is reduced. can do. On the other hand, since the dimension T of the clearance between the outer peripheral surface of the plunger 51 and the inner peripheral surface of the plunger barrel 32 at the upper portion of the plunger 51 can be set to the same size as the conventional one, the fuel injection characteristic is improved. The present invention can be applied to conventional fuel injection pumps without modification.

< Second configuration form>
Below, the structure of the fuel injection pump 3 which concerns on a 2nd structure form is demonstrated with reference to FIG. The fuel injection pump 3 is different from the fuel injection pump 1 according to the first configuration in that a plunger 61 is provided instead of the plunger 31.

The plunger 61 is a substantially cylindrical member. In the plunger 61, a lead portion 31a, a land portion 31b, a groove portion 31c, an engaging portion 31g, and the like are formed. The outer diameter of the plunger 61 below the groove portion 31c is smaller (reduced) than the outer diameter below the groove portion 31c of the plunger 31 according to the first configuration . The plunger 61 is fitted into the plunger barrel 32. The plunger 61 can move up and down in the axial direction along the inner peripheral surface of the plunger barrel 32 and can rotate in the circumferential direction.

As shown in FIG. 4, a coating film 67 is formed on the contact surface between the plunger 61 and the plunger barrel 32. In the present configuration , the coating film 67 is formed on a portion of the outer peripheral surface of the plunger 61 that is below the groove portion 31c and above the engaging portion 31g. The coating film 67 of this configuration form is a film formed by DLC. The film thickness Z (thickness) of the coating film 67 is larger than the film thickness X of the coating film 37 according to the first configuration .

  Of the outer peripheral surface of the plunger 61, the coating film 67 is not formed on the portion located above the groove portion 31c and the engaging portion 31g and the portion located below the engaging portion 31g. Therefore, of the outer peripheral surface of the plunger 61, the contact portion 61e that contacts the bottom portion of the tappet 14, the engagement portion 61f that engages with the lower spring receiver 33, and the engagement portion 31g are subjected to coating processing. It is a state that has not been done. Such a configuration can be realized, for example, by masking the upper side and the lower side (non-processing part) of the plunger 61 during the coating process.

In the present configuration , the clearance dimension N between the outer peripheral surface of the plunger 61 (the portion subjected to the coating process) after the coating process and the inner peripheral surface of the plunger barrel 32 is the clearance of the first embodiment . It is set to be the same as the dimension M (N = M). As described above, the outer diameter of the lower portion of the plunger 61 can be set smaller than the conventional dimension according to the film thickness Z of the coating film 67 to be formed.

  Below, the case where the technique which forms the coating film 67 on the plunger 61 is applied to the conventional fuel injection pump is demonstrated in detail with reference to Fig.4 (a) and FIG.4 (b).

The portion of the engaging portion 31g of the plunger 61 is not coated. Therefore, even if the engaging portion 31g slides in the engaging groove formed in the control sleeve 36, there is no possibility that the coating film is peeled off due to the sliding motion between these members. Similarly, the coating portion is not applied to the contact portion 61e and the engaging portion 61f of the plunger 61. Therefore, even if the plunger 61 rotates relative to the tappet 14 and the lower spring receiver 33, there is no possibility that the coating film peels off due to the sliding motion between these members. As described above, the plunger 61 of the present configuration is coated so as to avoid a portion where there is a possibility of peeling due to wear.

As described above, the fuel injection pump 3 according to the second configuration form includes the plunger 61 that moves up and down by the power transmitted from the crankshaft, the plunger barrel 32 that accommodates the plunger 61 so as to be able to move up and down, and the plunger 61 cannot be relatively rotated. A space defined by the upper surface of the plunger 61 and the inner peripheral surface of the plunger barrel 32 constitutes a pressurizing chamber 32a for pressurizing the fuel. In the fuel injection pump, the plunger 61 is provided with an engagement portion 31 g that engages with an engagement groove formed in the control sleeve 36. A groove portion 31c for reducing pressure is formed, located on the outer peripheral surface of the plunger 31 below the groove portion 31c, and the engaging portion 3 The portion located above the g, the coating film 67 is formed, is intended.

  With this configuration, the coating film 67 is not formed at the contact portion between the plunger 61 and the tappet 14, the lower spring receiver 33, and the engaging portion 31 g, thereby preventing the coating film 67 from peeling off. can do. Therefore, the frequency of replacement of the plunger 61 with a new one can be suppressed, and as a result, the maintainability of the fuel injection pump 3 is improved. Further, when the stripped coating film 67 is accumulated between the lower spring receiver 33 and the lower end portion of the plunger 61 (the contact portion 61e and the engagement portion 61f), the control sleeve 36 is rotated. There is no problem that the required operating force increases.

DESCRIPTION OF SYMBOLS 1 Fuel injection pump 31 Plunger 31c Groove part 31g Engagement part 32 Plunger barrel 32a Pressurization chamber 36 Control sleeve 37 Coating film

Claims (1)

A plunger that moves up and down by power transmitted from the crankshaft; and a plunger barrel that accommodates the plunger so as to be lifted and lowered.
In the fuel injection pump in which the space defined by the upper surface of the plunger and the inner peripheral surface of the plunger barrel constitutes a pressurizing chamber for pressurizing the fuel.
On the outer periphery of the upper and lower halfway portion of the plunger, a groove portion for reducing the pressure chamber is formed,
A coating film is formed on the outer peripheral surface of the plunger,
The dimension of the outer diameter of the plunger below the groove and the film thickness of the coating film is larger than the dimension of the outer diameter of the plunger and the film thickness of the coating film above the groove. Also, a fuel injection pump characterized by being set large .

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