FIELD OF THE INVENTION

The present invention relates to a high-pressure pump for vehicle, and more particularly to a high-pressure pump for a common rail of an internal combustion engine (such as a diesel engine), wherein a high-pressure assembly of the high-pressure pump has an improved cam follower device.

BACKGROUND

In a fuel injecting system for vehicle or other apparatus, in order to supply high-pressure fuel into an engine, a high-pressure pump is adopted. The high-pressure pump generally comprises one or more high-pressure assemblies to pressurize the fuel at high pressure and then to supply it into the engine.

Figure 1 schematically shows a conventional high-pressure pump. The conventional high-pressure pump mainly comprises a housing 5, which, in its interior, defines a common driving shaft camber as well as a cam follower device chamber and a plunger sleeve installing chamber, wherein the latter two chambers extend perpendicular to the common driving shaft camber, an annular shoulder 25 is provided to separate the cam follower device chamber from the plunger sleeve installing chamber and at the same time to keep them communicating with each other; a plunger sleeve type high-pressure assembly 2, a main body of which is mounted in the housing 5; and a driving shaft 3 which is mounted in the driving shaft chamber of the housing 5 and has a cam 50 for driving the high-pressure assembly 2.

The high-pressure assembly 2 mainly comprises: a plunger sleeve 20 which is secured in the plunger sleeve installing chamber of the housing 50, wherein the axial position of the plunger sleeve 20 is limited by the shoulder 25; a plunger 22 which is movable back and forth in the plunger sleeve; a check valve device 24 which is mounted in the plunger sleeve such that a pressurization chamber is defined in the plunger sleeve between the plunger 22 and the check valve device 24; a cam follower device 4 which is mounted in the cam follower device chamber of the housing 5 and is driven by the cam 50 to force the plunger moving back and forth; and a fuel discharging joint 23 which is mounted outside of the check valve device 24 to discharge high-pressure fuel out of the high-pressure assembly through the check valve device 24. On the one hand, the check valve device 24 enables fuel, which is supplied from an oil tank to the high-pressure assembly, to flow into the pressurization chamber, but enables the fuel contained in the pressurization chamber not to flow back into the oil tank. On the other hand, the check valve device enables the fuel contained in the oil tank to be discharged out along the direction of the arrow F in figure 1 and to be supplied into an engine or a common rail system, but enables the discharged fuel not to flow back into the pressurization chamber.

As shown in figures 2 to 4, the cam follower device 4 mainly comprises a tappet body 6 slidable back and forth in the cam follower device chamber and a roller 8 mounted in the tappet body. The roller 8 is mounted rotatably on a spindle 7. A slide bearing 15 is provided between the roller 8 and the spindle 7.

The plunger 22 is pushed against the cam follower device 4 by a holding plate 14 and a spring 12 which is arranged in a front portion of the cam follower device chamber. The spring 12 also presses the roller 8 of the cam follower device 4 onto a cam surface of the cam 50.

When the spindle 3 is rotated, a relevant cam lobe on the cam surface of the cam 50 raises the cam follower device 4 upwardly and drives the plunger 22 via the cam follower device 2 to advance in the plunger sleeve. After the cam lobe is rotated over the cam follower device 4, the spring 12 pushes the cam follower device 4 to fall towards a relevant depression area of the cam surface such that the plunger 22 fallbacks in the plunger sleeve. In order to keep the cam follower device 4 at a proper position in the cam follower device chamber, a guiding piece 10, which protrudes from a periphery of the tappet body 6, is mounted on the cam follower device 4. A corresponding guiding groove 16 is formed in the cam follower device chamber, which guiding groove extends parallel to the longitudinal direction of the plunger. The guiding piece 10 is insertable in the guiding groove 16 and is slidable in the guiding groove parallel to the longitudinal direction of the plunger, such that the movement of the cam follower device 4 is directed and the cam follower device is kept in position.

Because the annular shoulder 25 is provided in the housing 5 to separate the cam follower device chamber from the plunger sleeve installing chamber and the guiding piece 10 protrudes from the periphery of the tappet body 6, it is impossible to mount the cam follower device 4, the spring 12 and the holding plate 14 into the cam follower device chamber through the plunger sleeve installing chamber. For this reason, an installing aperture 17 is opened in a bottom portion of the housing 5. During being assembled, the plunger sleeve 20 is first mounted in the plunger sleeve installing chamber, and then the plunger 22 together with the spring 12 and the holding plate 14 are plugged into the cam follower device chamber through the installing aperture 17 such that the plunger 22 is inserted in the plunger sleeve 20. Subsequently, the cam follower device 4 is mounted in the cam follower device chamber via the installing aperture 17 in such a way that the guiding piece 10 is inserted in the guiding groove 16. Subsequently, the driving shaft 3 is mounted in the driving shaft chamber. Finally, a seal 18 is provided to seal the installing aperture 17.

In the above mentioned high-pressure fuel pump, it takes much time opening a sufficiently sized installing aperture 17 in the bottom portion of the housing 5. Furthermore, the above assembling operation is inconvenient and time-consuming. Furthermore, although the installing aperture 17 is sealed with the seal 18, lubricant oil contained in the cam follower device chamber is easily leaked through the installing aperture 17 because the aperture is provided in the bottom portion of the housing 5. Furthermore, when it requires detaching the plunger, the spring, the holding plate and the cam follower device, it is necessary to first detach the seal 18, release the lubricant oil in the cam follower device chamber off, and then detach the driving shaft 3. Therefore, it is very inconvenient to repair or replace the plunger, the spring, the holding plate and the cam follower device.

Therefore, in order to solve the above problems, it is necessary to improve the conventional high-pressure fuel pump.

SUMMARY OF THE INVENTION It is an objective of the present invention to provide a high-pressure fuel pump, and more particularly a high-pressure pump for a common rail system of an internal combustion engine or a diesel engine, wherein using this kind of pump, the above problems that are relevant to the installation of the tappet body of the cam follower device in the prior art may be well solved.

For achieving the above objective, according to one aspect of the invention, a high-pressure fuel pump comprises:

a housing which, in its interior, has a cylindrical high-pressure assembly chamber; a high-pressure assembly for pressurizing fuel (such as diesel oil); and

a driving shaft for driving the high-pressure assembly via a cam to operate the high-pressure assembly, the driving shaft being partially mounted in the housing;

wherein the high-pressure assembly comprises a plunger sleeve which is inserted and mounted in the high-pressure assembly chamber; a plunger movable back and forth in the plunger sleeve; and a cam follower device which is driven by the cam on the driving shaft to enable the plunger to move back and forth;

the cam follower device comprises a tappet body slidable in the high-pressure assembly chamber; and a roller mounted in the tappet body, wherein the roller contacts with a cam surface of the cam of the driving shaft;

wherein the tappet body, on its periphery, is provided with a guide recess extending in a direction parallel to an axis of the plunger, that the housing, at a location corresponding to the guide recess, is provided with a protruding guide protrusion, and that the guide protrusion is inserted in the guide recess and the guide recess is enabled to slide with respect to the guide protrusion in the direction parallel to the plunger axis.

According to the present invention, when it intends to install the high-pressure assembly in the housing, the whole high-pressure assembly is placed in the high-pressure assembly chamber from an external opening of the chamber. According to a preferred embodiment of the present invention, the guide protrusion is a guide part mounted in the housing, wherein an inner end of the guide part is inserted in the guide recess.

According to another preferred embodiment of the present invention, the guide part comprises a pin portion at least at its inner end, and the guide part is passed through a guide part inserting hole formed in the housing.

According to another preferred embodiment of the present invention, the guide part is secured in the guide part inserting hole in an interference fit or screwed manner.

According to another preferred embodiment of the present invention, the guide recess is a guide groove.

According to another preferred embodiment of the present invention, the housing has a closed bottom portion.

According to another preferred embodiment of the present invention, the high-pressure fuel pump further comprises an oil feeding pump which is used to suck up fuel from an oil tank and to supply the fuel into the high-pressure assembly, and the oil feeding pump is mounted on the housing.

According to another preferred embodiment of the present invention, the tappet body has a cylinderical outer circumferential surface which is slidably mated with an inner circumferential surface of the high-pressure assembly chamber.

According to another preferred embodiment of the present invention, the plunger sleeve has a mounting portion which is inserted and mounted in the high-pressure assembly chamber and a shoulder which is pushed against an outer surface portion of the housing around the high-pressure assembly chamber.

According to another preferred embodiment of the present invention, the internal diameter of the high-pressure assembly chamber is constant.

According to another preferred embodiment of the present invention, the high-pressure assembly further comprises a spring which pushes the roller of the cam follower device against a cam surface of the cam of the driving shaft.

According to another preferred embodiment of the present invention, the plunger has an end whose diameter is increased, wherein said end delimits a holding plate on the plunger, the spring is biased against the holding plate so as to push a rear end of the plunger against the tappet body.

According to another preferred embodiment of the present invention, the guide part is a guide pin which is secured in the guide part inserting hole in an interference fit manner.

According to another preferred embodiment of the present invention, the plunger sleeve is provided with a leaky oil discharging passage therein, such that fuel, which is leaked along a gap between the plunger and the plunger sleeve, is completely returned into the oil tank.

The inventive high-pressure fuel pump is preferably a high-pressure pump for diesel engine. If the diesel engine is provided with a common rail, the high-pressure assembly is connected to the common rail. According to the present invention, it is unnecessary to open an installing aperture in the bottom portion of the housing, such that lubricant oil cannot leak from the bottom portion of the housing via the installing aperture.

Furthermore, the time required for machining the small sized guide part inserting hole in the housing is greatly less than that required for opening the large sized installing aperture in the bottom portion of the conventional housing. Further, the guide part inserting hole, which is provided in a side of the housing above the cam follower device chamber, cannot lead to leakage of the lubricant oil from the cam follower device chamber.

Furthermore, the whole high-pressure assembly can be installed directly into the high-pressure assembly chamber or removed from it independently of the driving shaft. Therefore, the high-pressure assembly can be installed and removed conveniently and quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

The previously described and other aspects of the present invention will be completely understood and comprehended by the following detailed explanation in combination of drawings, wherein: Figure 1 shows a cross-sectional side view of a conventional high-pressure fuel pump;

Figure 2 schematically shows a partial cross-sectional view, which illustrates a mating relationship between a cam follower device of a high-pressure assembly and a housing of the high-pressure fuel pump shown in figure 1 ;

Figure 3 shows a front view of the cam follower device shown in figure 2; Figure 4 shows a side view of the cam follower device along the arrow B shown in figure 2;

Figure 5 shows a cross-sectional front view of a high-pressure fuel pump according to an embodiment of the present invention;

Figure 6 shows a cross-sectional view of the high-pressure fuel pump along the direction A- A shown in figure 5;

Figures 7 and 8 show views similar as figures 5 and 6, but a high-pressure assembly is removed to illustrate a high-pressure assembly chamber;

Figure 9 schematically shows a partial cross-sectional view, which illustrates a mating relationship between a cam follower device of a high-pressure assembly and a housing of the high-pressure fuel pump according to the embodiment of the present invention;

Figure 10 shows a side view of the cam follower device along the arrow C shown in figure 9.

DETAILED DESCRIPTION OF THE INVENTION

Figures 5 and 6 show a main configuration of a high-pressure fuel pump according to an embodiment of the present invention. The high-pressure fuel pump may be used to supply high-pressure fuel into internal combustion engines of vehicles or other apparatuses. At present, in the field of vehicle, common rail technique is increasingly adopted. In a common rail type fuel injecting system, the pressurization of fuel and the injection of it are independent from each other. Fuel is fed at high pressure by a high-pressure pump and stored in a common rail. The common rail is connected in a branching manner in proper sequence to ejectors controllable by an electrical controlling unit. Each ejector comprises a fine-machined nozzle and a plunger drivable by an electromagnetic solenoid. The electrical controlling unit controls the ejectors to inject fuel into corresponding cylinders of the engine. Therefore, the inventive high-pressure fuel pump may constitute as one component of a common rail system of an internal combustion engine (such as a diesel engine) such that high-pressure fuel is fed into the common rail and the common rail injects the fuel via the ejectors into the engine.

As shown in figures 5 and 6, the inventive high-pressure pump mainly comprises: a housing 5 which, in its interior, defines a common driving shaft chamber extending laterally and a cylinderical high-pressure assembly chamber extending longitudinally and perpendicular to the common driving shaft chamber; an oil feeding pump 1 carried by the housing 5; plunger type high-pressure assemblies 2 (2 ^' ) which are mounted partly in the housing 5; and a driving shaft 3 which is mounted in the driving shaft chamber of the housing 5 and has cams 50 for driving the high-pressure assemblies 2. The driving shaft 3 is also used to drive the oil feeding pump 1.

The housing 5 is preferably cast. It can be integrally produced as a single piece or can be formed by assembling a plurality of parts together. The oil feeding pump 1 is mounted on the housing 5 to suck up fuel (such as diesel oil) from an oil tank (not shown) and to supply it into a main oil supplying passage 35 (figure 6) formed in the housing. The fuel enters from the main oil supplying passage 35 into a branch oil supplying passage 31 (figure 6) which allocates to the high-pressure assembly. Then, the fuel is supplied into the corresponding high-pressure assembly 2, 2 ^' through oil supplying holes 30 for high-pressure assembly, which holes are connected to the branch oil supplying passage 31. The fuel from the oil feeding pump 1 may be supplied into the main oil supplying passage 35 through a pipeline (not shown) formed in the interior of the housing 5 or alternatively may be supplied through a piping piece (not shown) connected outside of the housing 5 into the main oil supplying passage 35 via a fuel inlet 40 (shown in figure 5) for high-pressure assembly. The oil feeding pump 1 is mounted on the housing 5 and is coupled with an end of the driving shaft 3, such that the oil feeding pump 1 is driven by the driving shaft 3. The oil feeding pump 1 may be configured in conventional manners. For example, it can be a conventional vane pump, a gear pump or the like.

The high-pressure assembly is used to pressurize the fuel from the oil feeding pump 1 and supply it into the engine or the common rail. At least one high-pressure assembly is provided. However, in order to reduce the pressure fluctuation of supplied fuel, it is preferable to provide two or more high-pressure assemblies. Two high-pressure assemblies 2 and 2 ^' are illustrated in the figures.

The driving shaft 3 is extended through the housing 5 and is supported at both ends in the housing 5 by corresponding bearings.

The driving shaft 3 drives both the oil feeding pump 1 and the high-pressure assemblies 2, 2 ^' . Therefore, the relevant end of the driving shaft 3 is used to drive the oil feeding pump 1 rotating. The cams 50 are provided at a middle portion of the driving shaft 3 to drive the plunger type high-pressure assemblies 2 and 2 ^' . The high-pressure assemblies are arranged along the direction of the driving shaft.

A front end 54 of the driving shaft 3 is a driving end which extends outside of the housing 5 and is rotated by an output driver of the engine. Preferably, it is driven by a transmission mechanism.

According to the illustrated embodiment, each high-pressure assembly 2, 2 ^' is embodied as a plunger type high-pressure assembly. Theses high-pressure assemblies are installed side by side in the housing 5. The two high-pressure assemblies have the same configuration. Therefore, only the configuration of the high-pressure assembly 2 is explained below. Certainly, the two high-pressure assemblies 2 and 2 ^' can have different configurations.

The high-pressure 2 mainly comprises: a plunger sleeve 20, wherein a lower portion of the plunger sleeve is secured in the high-pressure assembly chamber of the housing 5, and the plunger sleeve, in its interior, has a valve installing chamber and a plunger chamber communicating with each other; a plunger 22 which is movable back and forth in the plunger chamber; a check valve device 24 which is mounted in the valve installing chamber in such a way that a pressurization cavity is defined in the plunger chamber between a front end of the plunger 22 and the check valve device 24; a cam follower device 4 which is mounted in the high-pressure assembly chamber of the housing 5 and is driven by the cam 50 to move the plunger back and forth; a fuel discharging joint 23 which is mounted at an outer side of the check valve device 24 to discharge high-pressure fuel out of the high-pressure assembly through the check valve device 24.

More particularly, the high-pressure assembly 2 mainly comprises: the plunger sleeve 20 which is secured in a cylinderical high-pressure assembly chamber 55 (shown in figures 7 and 8) of the housing 5 and which, in its interior, has the valve installing chamber and the plunger chamber communicating with each other; the plunger 22 which is movable back and forth in the plunger chamber; the check valve device 24 which is mounted in the valve installing chamber in such a way that the pressurization cavity is defined in the plunger chamber between the front end of the plunger 22 and the check valve device 24; the cam follower device 4 which is driven by the cam 50 on the driving shaft 3 to move the plunger 22 back and forth.

The plunger sleeve 20 has a cylinderical mounting portion 27 substantially at a middle thereof. The external diameter of the mounting portion is substantially equal to the internal diameter of the high-pressure assembly chamber 55. After the lower and middle portions of the plunger sleeve 20 are inserted in the high-pressure assembly chamber 55, the mounting portion 27 is mated with the high-pressure assembly chamber 55 to limit the radial position of the plunger sleeve 20 relative to the housing 5. A sealing ring is mounted between an outer circumferential surface of the mounting portion 27 and an inner circumferential surface of the high-pressure assembly chamber 55. The plunger sleeve 20 further comprises a shoulder 29 protruding radially above the mounting portion 27. The shoulder is used to abut against an upper surface portion 57 (shown in figure 7) of the housing around an opening of the high-pressure assembly chamber 55 so as to delimit the axial position of the plunger sleeve relative to the housing. The oil supplying hole 30 is formed in the plunger sleeve 20. Both ends of the hole are communicated with the check valve device 24 and the branch oil supplying passage 31 in the housing respectively. The check valve device 24 is an assembly comprised of two check valves, among of which, one check valve enables the fuel in the air supplying hole 30 to flow into the pressurization cavity 26 and enables the fuel in the pressurization cavity 26 not to flow into the air supplying hole 30; the other check valve enables the fuel in the pressurization cavity 26 to discharge out and flow into the engine or the common rail and enables the discharged fuel not to flow back into the pressurization cavity 26. This kind of check valve is well known in the art and its various configurations can be designed easily, which are not explained here.

The cam follower device 4 is a roller type cam follower device which mainly comprises a tappet body 6 slidable back and forth in the high-pressure assembly along an axis of the plunger 22 and a roller 8 mounted in the tappet body. The roller 8 is mounted rotatably on a spindle 7 which is secured in the tappet body 6. In order to facilitate rotating the roller 8 and reducing abrasion, a slide bearing 15 is provided between the roller 8 and the spindle 7.

The tappet body 6 can have a cylindrical outer circumferential surface which is matable with the inner circumferential surface of the high-pressure assembly chamber 55.

The plunger 22 has a rear end whose diameter is enlarged. Thereby, a holding plate 14 is held at a rear end of the plunger. In a front portion of the high-pressure assembly chamber, a spring 12 is mounted around the lower portion of the plunger sleeve so as to push the holding plate 14 against the cam follower device 4. Therefore, the rear end of the plunger 22 is always pushed against the cam follower device 4, such that the plunger 22 is always tightly contacted with the cam follower device 4. The spring 12 is also used to bias the cam follower device 4 onto a cam surface of the cam 50, such that a rolling contact between the roller 8 of the cam follower device 4 and the cam surface of the cam 50 is always maintained.

When the driving shaft 3 is rotated, a cam lobe 52 on the cam surface of the cam 50 raises the cam follower device 4 up and drives the plunger 22 to advance in the plunger chamber via the cam follower device 4. When the cam lobe 52 is rotated over the cam follower device 4, the spring 12 pushes the cam follower device 4 to fall toward a depression area of the cam surface such that the plunger 22 fallbacks in the plunger chamber. In this way, the cam drives the plunger 22 to reciprocate back and forth in the plunger chamber.

The high-pressure assembly is a plunger pump driven by the cam 50 on the driving shaft 3. The number of high-pressure assemblies equal to that of cams 50. In the embodiment illustrated in figure 5, two high-pressure assemblies 2, 2' are provided, and are driven by two corresponding cams 50 on the driving shaft 3. The two cams 50 are formed on the driving shaft 3 at axial positions corresponding to the high-pressure assemblies 2, 2', and they are offset regularly at an angle in the circumferential direction about the axis of the driving shaft 3. Each cam 50 has at least one cam lobe 52 (in the embodiment illustrated by figure 6, three are arranged regularly) on its cam surface. In the illustrated case, after the driving shaft 3 completes one rotation, each cam 50, by its cam lobes 52, drives the relevant high-pressure assembly to operate three times. Meanwhile, when one high-pressure assembly operates to suck fuel up, the other high-pressure assembly operates to discharge the fuel out, which will be explained below. In the state illustrated by figure 5, the plunger 22 in the high-pressure assembly 2 is at a top dead center over its stroke, that is, the volume of the pressurization cavity is minimal; the plunger 22 in the high-pressure assembly 2' is at a bottom dead center over its stroke, that is, the volume of the pressurization cavity is maximal. Working periods of these high-pressure assemblies are staggered with each other to facilitate restraining the pressure fluctuation of fuel supplied in the engine or the common rail.

The cam 50 may be integrally formed as a part of the driving shaft 3 or alternatively may be produced separately and then be mounted on the driving shaft 3.

When the high-pressure pump is operated, low-pressure fuel from the oil feeding pump 1 is fed into main oil supplying passage 35, fed from there into the branch oil supplying passage 31 , and then fed from the branch oil supplying passage 31 into the oil supplying hole 30. When the plunger 22 fallbacks (moves far away from the check valve device 24, i. e. along a direction enabling the volume of the pressurization cavity 26 to be increased), fuel in the oil supplying hole 30 is sucked into the pressurization cavity 26. When the plunger 22 advances (moves toward the check valve device 24, i. e. along a direction enabling the volume of the pressurization cavity 26 to be decreased), the fuel in the pressurization cavity 26 is pressurized by the plunger 22 and discharged out of the high-pressure pump through the check valve device 24. When the plunger 22 advances and thus the fuel in the pressurization cavity 26 is pressurized, only a little of fuel is leaked backwardly in a gap between the outer surface of the plunger 22 and the inner wall of the plunger chamber. In the plunger sleeve 20, formed substantially in the middle portion of the plunger chamber are an annular oil collecting groove 32 and a leaky oil discharging passage 34 which opens from the oil collecting groove 32 toward the periphery of the plunger sleeve 20.

The leaky oil discharging passage 34 is communicated with a corresponding branch leaky oil returning passage 60 formed in the housing 5. The branch leaky oil returning passage 60 is communicated with a common main oil returning passage 65 (shown in figure 6). This main oil returning passage 65 opens to the oil tank. In this way, high temperature fuel leaked along the outer surface of the plunger 22 is collected in the oil collecting groove 32 and is completely returned into the oil tank through the leaky oil discharging passage, the branch oil returning passage 60 and the main oil returning passage 65 without influencing the temperature of fuel supplied in the pressurization cavity.

Furthermore, in order to prevent heat of the leaky high temperature fuel from be transferred to the supplied fuel, the oil supplying hole, the branch oil supplying passage and the main oil supplying passage are arranged at one side of the relevant high-pressure assembly, and the leaky oil discharging passage, the branch oil returning passage and the main oil returning passage are arranged at the other side of the relevant high-pressure assembly. In this way, the leaky high temperature fuel is completely returned into the oil tank through the separately provided branch and main oil returning passages without the temperature of fuel supplied in the pressurization cavity being increased and without the viscosity of fuel being reduced and the leakage rate of fuel being increased.

In order to guide the cam follower device 4 in the high-pressure assembly chamber 55 and to hold the cam follower device 4 at a proper position in the high-pressure assembly chamber, a guide recess is formed on the periphery of the tappet body 6 of the cam follower device 4 parallel to the plunger axis. Further, at a location corresponding to the guide recess, a guide protrusion is provided in the housing 5. The guide protrusion may be integrally formed in the housing 5 or may be mounted, as a separate piece, in the housing. The guide protrusion is insertable in the guide recess and enables the guide recess to slide with respect to the guide recess and parallel to the plunger axis.

Each high-pressure assembly may be equipped with at least a pair of matable guide recess and guide protrusion. In a preferred embodiment, the guide recess is in the form of a guide groove 82, and the guide protrusion is in the form of a guide part 80, as shown in figures 9 and 10. At a location corresponding to the guide groove 82, a guide part inserting hole 85 (shown in figure 8) is formed through the housing 5. The guide part 80 is inserted and secured in the guide part inserting hole 85. An inner end of the guide part 80 is inserted in the guide groove 80 in such a way that the guide groove 82 is slidable forwardly or backwardly with respect to the guide part 80. Therefore, the tappet body 6 is guided via the guide part 80 to slide in the high-pressure assembly chamber 55 parallel to the plunger axis, and at the same time the tappet body 6 is held at the proper position in the high-pressure assembly chamber 55. The position of the guide part inserting hole 85 is designed in such a way that the inner end of the guide part 80 is always located in the guide groove 82 during the tappet body 60 slides back and forth in the high-pressure chamber 55.

The guide groove 82 may have various possible cross-sections in a plane perpendicular to the plunger axis. The inner end of the guide part 80 has a cross-sectional shape matable with the guide groove 82.

The guide part 80 may be a simple guide pin which is secured in the guide part inserting hole 85 in an interference fit manner. Alternatively, a portion (the inner portion) of the guide part 80 may be a pin portion.

Alternatively, the guide part 80 may screwed in the guide part inserting hole 85.

A seal may be provide between the guide part 80 and the guide part inserting hole 85. According to the present invention, a single high-pressure assembly chamber 55 is formed in the housing 5 of the high-pressure fuel pump, which chamber is allocated to each high-pressure assembly 2. The recessed guide groove 82 is provided on the tappet body 6 of the cam follower device 4. Therefore, the cam follower device 4 can be inserted directly into the high-pressure assembly chamber through the outer opening of the high-pressure assembly chamber 55.

The internal diameter of the high-pressure assembly chamber 55 is preferably constant, which facilitates machining the chamber.

During the high-pressure pump is assembled, the driving shaft 3 is first installed into the driving shaft chamber of the housing 5. Subsequently, the cam follower device 4 is inserted from the outer opening of the high-pressure assembly chamber 55 into the high-pressure assembly chamber such that the guide groove 82 of the tappet body 6 is aligned with the guide part inserting hole 85. Subsequently, the guide part 80 is inserted and secured in the guide part inserting hole 85 with the inner end of the guide part 80 being inserted in the guide groove 82. Subsequently, using the outer opening of the high-pressure assembly chamber 55, the plunger 22 (together with the spring 12 and the holding plate 14) and the plunger sleeve 20 (together with the check valve device 24) are inserted in the high-pressure assembly chamber. The position of the plunger sleeve 20 relative to the housing 5 is determined by the mounting portion 27 and the shoulder 29 of the plunger sleeve. Then, a screw is used to secure the plunger sleeve 20 in the housing 5. In this way, the high-pressure assembly is installed on the housing. It can be seen that, the whole high-pressure assembly is installed in the housing from one side thereof. In comparison with the conventional technique that the high-pressure assembly is installed in the housing from both sides, the inventive technique is simpler and quicker.

Furthermore, when it is required to remove the high-pressure assembly to repair or inspect its components, it is possible to remove the components directly from the high-pressure assembly chamber 22 without first removing the driving shaft as in the prior art. Therefore, the high-pressure assembly can be assembled or detached conveniently and quickly. According to the present invention, a bottom portion of the housing 5 may be closed without an installing aperture being opened in the bottom portion of the housing 5. In fact, the guide part inserting hole is opened in a side of the housing above the cam follower device chamber. Therefore, the bottom portion of the housing 5 is wholly closed such that lubricant oil in the cam follower device chamber is prevented from leaking.

Furthermore, the diameter of the guide part inserting hole 85 is greatly less than the diameter of the installing aperture in the bottom portion of the conventional housing. Therefore, the time required for machining the guide part hole in the housing is greatly less than the time required for opening the installing aperture in the bottom portion of the conventional housing.

In conclusion, the general performance of the inventive high-pressure pump is clearly excellent to the prior art mentioned above.

Although the present invention is shown and explained by specific embodiments, the present invention is not limited by these explained particulars. Contrarily, various modifications of the present invention are possible within the scope of attached claims and their equivalents.