Fuel supply pump

Abstract

A fuel supply pump, which is simple in construction and easy to produce and is capable of efficiently pressurizing a high flow rate of fuel, is provided. The fuel supply pump (50) includes a housing (52), a plunger barrel (53), a plunger (54) for pressurizing fuel, which is installed in the plunger barrel (53) so as to be allowed to move up and down, a cam (60) installed in rotation way below the plunger (54), a tappet structure body (6) installed between the cam (60) and the plunger (54) to transmitting the turning force, serving as a lifting force, from the cam shaft (3) to the plunger (54), a tappet structure body (6) installed between the cam (60) and the plunger (54) and provided for transmitting a upward or downward movement of the cam (60) caused by the rotation of the camshaft (3) to the plunger (54); and a return spring (68) for setting lowering force to the plunger (54), which is installed between the tappet structure body (6) and the plunger barrel (53).

Description

TECHNICAL FIELD

The present invention relates to a fuel supply pump. Particularly, the present invention relates to a fuel supply pump suitable for an accumulator fuel injection device with a pressure-amplifying piston (APCRS: Amplified Piston Common Rail System) that requires a high flow rate of pressurized fuel.

BACKGROUNDS

A conventional fuel supply pump 250 has been constructed as shown in FIG. 16. The conventional fuel supply pump 250 comprises: a pump housing 252 having a cylindrical space opened from end to end in the vertical direction; a plunger barrel 253 installed in the upper opening portion of the pump housing 252; a plunger 254 for pressurizing fuel, which is installed in the plunger barrel 253 and the cylindrical space of the pump housing 252 so as to be allowed to move up and down; a cam 260 installed in a rotation way below the plunger 254 and integrated with a cam shaft 3 (not shown) inserted into the pump housing 252 in the longitudinal direction; a tappet structure body installed between the cam 260 and the plunger 254 and provided for transmitting the torque of the cam shaft 203 as a lifting force to the plunger 254; and a return spring 268 for setting lowering force to the plunger 254, which is installed between the tappet structure body 206 and the plunger barrel-253.

As disclosed in JP 2001-317430 A and JP 2001-221130 A, such a conventional fuel supply pump 250 is constructed so as to move the cam 260 up and down when the cam shaft 3 is revolved by driving an engine (not shown). In conjunction with such a movement, the plunger 254 is allowed to be lifted and lowered through the tappet structure body 206. Therefore, the fuel supply pump 250 is constructed such that fuel can be suctioned into a pump chamber through an inlet valve by lowering the plunger 254, while the fuel in the pump chamber can be pressurized by lifting the plunger 254 to discharge the fuel from the pump chamber to a pressure-accumulating chamber (not shown) through an outlet valve.

However, such a fuel supply pump is provided with a projection 252a for supporting the upper end of the return spring 268 in the inner peripheral surface of the pump housing 252. Thus, for assembling the fuel supply pump 250, the plunger barrel 253 and the plunger 254 have to be inserted into the accommodating portion of the pump housing 252 from the upper portion thereof while staying out of the projection 252a. On the other hand, the return spring 268 and the tappet structure body 206 have to be inserted from a floor plug 280 formed below the pump housing 252 while staying out of the projection 252a. Consequently, in the conventional fuel supply pump, there are problems in that the assembly work is complicated and the production cost is not easily reduced.

Furthermore, for a diesel engine, as disclosed in JP 56-93936 A and JP 2885076 B, an accumulator fuel injection device (CRS: Common Rail System) that employs an accumulator (common rail) has been proposed to make it possible to increase engine power, improve fuel consumption, reduce particulate matters, and so on by efficiently injecting high-pressure fuel. There has been also proposed an accumulator fuel injection device that pressurizes and utilizes fuel from an accumulator.

Such a fuel supply pump 250 is intended to supply a relatively high flow rate of fuel into the accumulator by providing a predetermined lubrication mechanism (not shown) in a tappet structure body and forming a seal ring 252b installed between a pump housing 252 and a plunger barrel 253 into a predetermined shape. However, the degree of pressurization and the flow rate of fuel are still insufficient to allow higher power of the diesel engine.

Therefore, as a result of concentrated study, the present inventors have found out that the above problem can be solved by forming a projection on the plunger barrel to retain the upper end of a return spring, instead of forming a projection for supporting the upper end of the return spring on the inner peripheral surface of a pump housing.

That is, an object of the present invention is to provide a fuel supply pump, which is not only simple in construction and easy to produce but also capable of efficiently pressurizing a high flow rate of fuel.

DISCLOSURE OF THE INVENTION

[1] According to the present invention, the above object can be solved by providing a fuel supply pump comprising: a pump housing having a cylindrical space opened from end to end in the vertical direction; a plunger barrel installed in the upper opening portion of the pump housing; a plunger for pressurizing fuel, which is installed in the plunger barrel and the cylindrical space of the pump housing so as to be allowed to move up and down; a cam installed in rotation way below the plunger and integrated with a cam shaft inserted into the pump housing; a tappet structure body installed between the cam and the plunger and provided for transmitting a upward or downward movement of the cam caused by the rotation of the cam shaft to the plunger; and a return spring for setting lowering force to the plunger, which is installed between the tappet structure body and the plunger barrel, wherein the plunger barrel has a projection for supporting the upper end of the return spring.

That is, as constructed above, the inner peripheral surface of the pump housing does not require a projection for supporting the upper end of the return spring. Thus, no obstacle is provided on the inner peripheral surface of the pump housing has, so that the respective structural components such as the tappet structure body, the plunger barrel, and the plunger can be temporarily preassembled and inserted into the cylindrical space of the housing from the upper portion of the pump housing. In addition, no floor plug for inserting the tappet structure body is required. Consequently, the fuel supply pump simple in construction and easy to produce can be provided.

Furthermore, there is no obstacle in the inner peripheral surface of the pump housing, so that the inner peripheral surface of the pump housing can be processed more precisely and more easily than a conventional one. Thus, the cam shaft can be set at a higher rotational frequency. Consequently, the fuel supply pump, which is capable of supplying a high flow rate of fuel sufficiently pressurized into an accumulator, can be provided.

[2] For the configuration of the fuel supply pump of the present invention, it is preferred that the plunger barrel has a large diameter portion for restricting the movement of the return spring in the radial direction.

As configured above, the fuel supply pump of the present invention does not require any of projections and other restricting components conventionally provided in the inner peripheral surface of the pump housing for restricting the movement of the return spring in the radial direction.

Thus, the number of components can be reduced. Consequently, the fuel supply pump, which is simple in construction and easy to produce, can be provided.

[3] Furthermore, for the configuration of the fuel supply pump of the present invention, it is preferred that the projection of the plunger barrel has an outer peripheral surface fitted to the peripheral surface of the cylindrical space of the pump housing.

As configured above, the movement of the plunger barrel in the radial direction within the pump housing can be restricted easily and precisely.

[4] Additionally, for the configuration of the fuel supply pump of the present invention, it is preferred that the plunger barrel has a seal ring receiver in the outer peripheral surface of the projection.

As configured above, the movement of the plunger barrel in the radial direction within the pump housing can be restricted more effectively.

[5] In addition, for the configuration of the fuel supply pump of the present invention, it is preferable to provide a spring sheet between the return spring and the tappet structure body. The spring has an opening portion into which the plunger is inserted. In this case, a spring holding portion for restricting the downward movement of the return spring is also provided in the outer peripheral portion of the spring sheet.

As configured above, the return spring is allowed to exert spring force as lowering force effectively work on the plunger through the spring sheet.

[6] Additionally, for the configuration of the fuel supply pump of the present invention, it is preferred that the tappet structure body further comprises a cylindrical shell having an outer peripheral surface fitted to the peripheral surface of the cylindrical space of the pump housing, wherein the inner surface of the shell is provided with a projection for restricting the movement of the return spring in the radial direction.

As configured above, a roller body itself is not required to have a function for restricting the movement of the spring sheet in the radial direction. Thus, the composition of the roller body can be simplified.

[7] Furthermore, for constructing the fuel supply pump of the present invention, it is preferable to use an accumulator fuel injection device for pressurizing fuel having a flow rate per unit time of 500 to 1,500 litters per hour up to 50 MPa or more.

Using such an accumulator fuel injection device, the pressurization of the fuel having a large flow rate can be easily carried out. Therefore, the accumulator fuel injection device attains a further increase in fuel efficient, so that a diesel engine will have a higher power and an increase in fuel consumption, while attaining a reduction in particulate matters, and so on.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side-view of the fuel supply pump of the present invention with a portion partly broken away.

FIG. 2 is a cross-sectional view of the fuel supply pump of the present invention.

FIG. 3 is a diagram with perspective and cross-sectional views of a housing.

FIG. 4 is a diagram for illustrating a plunger barrel, a fuel inlet valve, and a fuel outlet valve.

FIG. 5 is diagram with perspective and cross-sectional views of a plunger.

FIG. 6 is a diagram with perspective, plane, and cross-sectional views of a spring sheet.

FIG. 7 is a diagram for illustrating a tappet structure body.

FIG. 8 is a diagram for illustrating a roller body.

FIG. 9 is a perspective view of the tappet structure body.

FIG. 10 is a cross-sectional view of the fuel inlet valve.

FIG. 11 is a cross-sectional view of the fuel inlet valve.

FIG. 12 is a diagram for illustrating the system of an accumulator fuel injection device (APCRS) in the form of a pressure amplifying piston system.

FIG. 13 is a diagram for illustrating the configuration of the accumulator fuel injection device (APCRS) in the form of a pressure amplifying piston system.

FIG. 14 is schematic diagram for illustrating a method for raising the pressure of fuel in the accumulator fuel injection device (APCRS) in the form of a pressure amplifying piston system.

FIG. 15 is a diagram for illustrating a timing chart of high-pressure fuel injection.

FIG. 16 is a diagram for illustrating the configuration of a conventional fuel supply pump.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the fuel supply pump will be described concretely with proper references to the drawings.

1. Basic Configuration of Fuel Supply Pump

As shown in FIG. 1 and FIG. 2, the present embodiment is a fuel supply pump 50 comprising: a pump housing 52 having a cylindrical space opened from end to end in the vertical direction; a plunger barrel 53 installed in the upper opening portion of the pump housing 52; a plunger 54 for pressurizing fuel, which is installed in the plunger barrel 53 and the cylindrical space of the pump housing 52 so as to be allowed to move up and down; a cam 60 installed in rotation way below the plunger 54 and integrated with a cam shaft 3 inserted into the pump housing 52; a tappet structure body 6 installed between the cam 60 and the plunger 54 and provided for transmitting a upward or downward movement of the cam 60 caused by the rotation of the cam shaft to the plunger 54; and a return spring 68 for setting lowering force to the plunger 54, which is installed between the tappet structure body 6 and the plunger barrel 53.

In addition, for the fuel supply pump 50 of the present embodiment, the plunger barrel 53 has a projection 53a for supporting the upper end of the return spring 68.

Hereinafter, the fuel supply pump 50 will be described more concretely by way of individually describing its structural components.

(1) Pump Housing

As exemplified in FIG. 1 and FIG. 2, the pump housing 52 is provided as an enclosure for housing the plunger barrel (cylinder) 53, the plunger 54, the tappet structure body 6, and the cam 60, and also provided for compartmentalizing the fuel compression chamber 74. Therefore, preferably, as shown in FIG. 3(a) and 3(b), the pump housing 52 has a shaft-inserting hole 92a opened from side to side in the horizontal direction and a cylindrical spaces 92b, 92c opened from end to end in the vertical direction.

Furthermore, as shown in FIG. 3(b), the pump housing 52 is preferably provided with through-holes 97, 98 opened in the lateral directions of the cylindrical spaces 92b, 92c, respectively. Specifically, each of the through-holes 97, 98 is preferably provided as an assembly of three hole portions (large, middle, and small holes) 97a-97c, 98a-98c with different pore sizes, concentrically arranged in a stepwise pattern. Therefore, the tip portions of guide pins (not shown) are press-inserted into the hole portions 97a, 98a to ensure high-precision positioning of the guide pins. In addition, the hole portions 97b, 98b have their own functions of introducing the tip portions of the guide pins into the hole portions 97c, 98c to press-insert the tip portions of the guide pin into the hole portions 97c or 98c, respectively. In addition, the hole portions 97a, 98a are preferably formed of threaded portions such that the guide pins can be press-fitted into the hole portions 97a, 98a to press-insert the dip portions of the guide pins into the hole portions 97a, 98a, respectively. Therefore, the guide pin can be press-inserted by means of thread engagement.

Furthermore, because the projection for supporting the upper end of the return spring 68 is provided in the plunger barrel 53 described below, projections in the inner peripheral surface of the cylindrical spaces 92b and 92c in the pump housing 52 are not required.

Thus, the inner peripheral surface of the pump housing 52 can be processed easily and precisely. Thereby, even in the case of rotating the cam shaft 3 at high speed, the vibration by the rotation can be effectively controlled. Consequently, the cam shaft 3 can be set at a higher rotational frequency than a conventional one. Furthermore, high power of a diesel engine, improvement in fuel consumption, reduction in particulate matters, and so on can be attained because the cam shaft 3 can be rotated at high speed and a high flow rate of fuel sufficiently pressurized can be supplied into an accumulator. In addition, there is no need to arrange a floor plug for inserting the tappet structure body and so on, allowing simpler composition.

Moreover, the fuel supply pump 50 can be assembled by only temporarily preassembling each component such as the tappet structure body 6, the plunger barrel 52, and the plunger 54 and inserting them into the cylindrical spaces 92b and 92c of the housing from the upper portion of the pump housing 52. Thus, the production cost can be significantly reduced.

Still, it is preferable that the movement of the return spring 68 in the radial direction is restricted by the plunger barrel 53. This is because of no need of any spring receiver that is conventionally essential to restrict the movement of the return spring in the radial direction. Therefore, the inner peripheral surface of the pump housing can be processed more easily and precisely. As a result, the cam shaft can be set at a higher rotational frequency.

(2) Plunger Barrel

A plunger barrel 53 is, as exemplified in FIG. 1 and FIG. 2, an enclosure for supporting the plunger 54 and constitutes a part of a fuel compression chamber (pump chamber) 74 for pressurizing a large amount of fuel at high pressures by the plunger 54. Therefore, the plunger barrel 53 is attached to the upper opening portion of each of the cylindrical spaces 92b, 92c in the pump housing 52. In addition, as shown in FIG. 2, the fuel compression chamber 74 for compressing the fuel introduced from a fuel tank (not shown) is installed between the outer peripheral surface of the plunger barrel 53 and the inner peripheral surface of the pump housing 52 (the peripheral surface of the cylindrical spaces 92b and 92c).

Furthermore, the plunger barrel 53 is characterized by having the projection 53a for supporting the upper end of the return spring 68. It is because of no need of any projection to restrict the upward movement of the return spring 68 in the inner peripheral surface of the pump housing 52 as the upper end of the return spring 68 is supported by the projection 53a of the plunger barrel 53.

Moreover, as shown in FIG. 2, the plunger barrel 53 is preferably provided with a large diameter portion 53b for restricting the movement of the return spring 68 in the radial direction. It is because of no need of any projection to restrict the movement of the return spring 68 in the radial direction in the peripheral surface of the pump housing 52 as well as to provide any component between the pump housing 52 and the return spring 68 to restrict the movement of the return spring 68 in the radial direction.

In addition, preferably, for the plunger barrel 53, the projection 53a has an outer peripheral surface fitted to the peripheral surface of the cylindrical space of the pump housing 52. This is because the movement of the plunger barrel 53 in the radial direction within the pump housing 52 can be restricted.

Furthermore, for the plunger barrel 53, as shown in FIG. 4, the outer peripheral surface of the projection 53a is preferably provided with a seal ring receiver 53c. This is because the movement of the plunger barrel 53 in the radial direction within the pump housing 52 can be restricted more effectively.

Furthermore, regarding the conformation of the plunger barrel 53, when the fuel supply pumps to be mounted on the plunger barrel are of inline and radial types, the conformation of the plunger barrel can be suitably changed so as to correspond to the respective types.

(3) Plunger

As exemplified in FIG. 1 and FIG. 2, the plunger 54 is a principle structural component for pressurizing fuel at high pressures in the fuel compression chamber 74 formed in the plunger barrel 53. Therefore, the plunger 54 is arranged so as to be capable of lifting and lowering movements in the plunger barrel 53 attached in each of the cylindrical spaces 92b, 92c formed in the pump housing 52 lifting and lower movement. In addition, as shown in FIG. 1 and FIG. 2, the plunger 54 is provided with a pressure portion 54a for allowing the plunger 54 to be introduced into or pulled out of the inside of the fuel compression chamber 74.

The pressure portion 54a is designed such that the pressure portion 54a has a diameter smaller than the diameter of the plunger barrel 53. Thus, a gap is preferably formed between the pressure portion 54a and an outlet valve 79 when the pressure portion 54a moves to the top dead center. This is because that the plunger 54 is driven at high speed to smoothly feed fuel to a common rail under pressure without allowing the pressure portion 54a to occlude the inlet of the outlet valve 79 even after pressurizing a large amount of fuel.

Furthermore, the plunger 54 is preferably formed in the shape of a round bar as a whole and provided with a collar portion 55 on its opposite end with respect to the pressure portion 54a to allow the plunger 54 to be smoothly driven at high speed. That is, it is preferable that the collar part 55 for locking is integrally formed on the external peripheral surface of the tip portion (lower end portion) of the cylindrical plunger 54. This is because that such a configuration of the plunger 54 can be easily and positively fixed in the opening portion 15 formed in the plunger mounting portion 14.

Furthermore, as shown in FIG. 2, the plunger 54 is preferably constructed such that the plunger 54 is always forced to move toward the cam by a spring 68 for returning the plunger and moves upward in response to the rotary movement of the cam 60 to pressurize fuel in the fuel compression chamber 74.

Furthermore, in the fuel supply pump of the present embodiment, it is preferable to pressurize a large amount of fuel by driving the cam and the plunger at high speed in the plunger barrel 53. Specifically, the rotation frequency of the cam is preferably in the range of 1,500 to 4,000 rpm. In addition, considering a gear ratio, the rotation frequency of the cam is preferably in the range of 1 to 5 times higher than the rotation frequency of an engine.

(4) Fuel Compression Chamber

As shown in FIG. 2, the fuel compression chamber 74 is a small chamber in the plunger barrel 53, which is formed by a combination of the plunger barrel 53 and the plunger 54. Thus, in the fuel compression chamber 74, the fuel quantitatively introduced into the fuel compression chamber 74 through a fuel inlet valve 73 can be pressurized efficiently and massively by driving the plunger 54 at high speed. Furthermore, even though the plunger 54 is driven at high speed as described above, for preventing a fuel for lubrication from inhibiting a high speed movement of the plunger 54, it is preferable that a spring sheet and a roller body described latter are provided with their respective fuel pass-through holes and the corresponding fuel pass-through holes are communicated with each other.

On the other hand, after completion of pressurization with the plunger 54, the pressurized fuel is supplied to a common rail (not shown) through the fuel outlet valve 79.

(5) Spring Sheet

FIG. 6(a) is a perspective view of the spring sheet 10. Similarly, FIG. 6(b) is a plane view of the spring sheet 10 and FIG. 6(c) is a cross-sectional view of the spring sheet 10 shown in FIG. 16(a).

The spring sheet 10 comprises a spring holding portion 12 for supporting a spring to be used at the time of pulling down the plunger 54 of the fuel supply pump 50 and a plunger mounting portion 14 for catching the plunger. Preferably, pass-through holes 16 for allowing passage of a lubricant or a fuel for lubrication are formed around the plunger mounting portion 14. In addition, for the spring sheet 10, an opening portion 15 for penetrating the plunger 54 there into is preferably provided in the center of the plunger mounting portion 14. This is because, as constructed above, a lubricant or a fuel for lubrication can move forward and backward freely through the spring sheet 10. Consequently, factors for inhibiting the plunger 54 driven at high speed are allowed to be lessened.

(6) Tappet Structure Body

Next, the tappet structure body will be described with reference to the drawings. Here, FIG. 7 is a diagram for illustrating the tappet structure body. Similarly, FIG. 8 is a diagram for illustrating a roller body and FIG. 9 is a perspective view of the tappet structure body.

As shown in (a) to (c) of FIG. 7, the tappet structure body 6 is constructed of a roller 29 in which a pin portion and a roller portion are integrated together, the roller body 28 receiving the roller 29, and a cylindrical shell 27 arranged so as to surround the roller 29 and the roller body 28. Preferably, it is constructed so as to be lifted and lowered by the rotary movement of the cam shaft 3 and the cam 60 connected thereto shown in FIG. 1.

This is because, as constructed above, the number of components can be saved and the conventional lubrication between the pin and the roller is not required. Thus, the roller is allowed to be driven at high speed. Consequently, because the cam shaft 3 can be set at a higher rotational frequency, a high flow rate of fuel that is sufficiently pressurized can be supplied into an accumulator.

In addition, as shown in FIGS. 7(a) to 7(c), the roller body 28 preferably has a main body 30 and is then held within the shell 27. Furthermore, on the main body 30, the roller support 30a having the inner peripheral surface is fitted to the outer peripheral surface of the roller 29. As shown in FIGS. 8(a) to 8(c), on the central portion of the upper surface of the main body 30, a contact portion 30c is provided integrally with the plunger 54 and protrudes toward the plunger 54. Preferably, on the peripheral portion of the main body 30, a sheet receiver 30d for receiving the spring sheet 10 is provided integrally therewith to protrude.

On the other hand, preferably, the surface of the roller receiver 30a is formed with a carbon coating consisting of an amorphous hard carbon film. This is because the friction against the surface of the roller receiver 30a is reduced and the abrasion on the surface of the roller receiver 30a is prevented. Thus, the roller 29 is allowed to be driven at high speed.

Still, the carbon coating preferably contains nitrogen and silicon. Also, preferably, its formation method utilizes, but not particularly limited to, a CVD method with plasma and ion beam.

In addition, as illustrated in FIG. 7 to FIG. 9, for the roller body 28, for example two fuel pass-through holes 30b through which a lubricant used for lubricating the inner portion of the fuel supply pump or fuel is passed are preferably arranged around the roller body at the symmetric position with respect to a central projection 30c.

Preferably, the shell 27 opens from end to end in the vertical direction and forms a cylindrical body having an outer peripheral surface fitted to the peripheral surface of cylindrical spaces 92b and 92c of a pump housing 52 shown in FIG. 3. Furthermore, on the top of the peripheral wall of the shell 27, a long hole 27a into which the guide pin is inserted is provided and formed as a pass-through hole extending in the axis direction of the shell 27. This is because the guide pin and the long hole 27a cooperate to be capable of moving up and down along the axis of the cylindrical spaces 92b and 92c for maintaining the movement of the tappet structure body 6 in the required direction, when the tappet structure body 6 moves up and down. Moreover, centering the tappet structure body 6 on the pump housing 52 can be performed only by inserting the outer peripheral surface of the shell 27 into the pump housing 52.

Additionally, the inner peripheral surface of the shell 27 is preferably provided with a first projection 27b as a projection for restricting the upward movement of the roller body 28. Similarly, the inner peripheral surface of the shell 27 is provided with a second projection 27c integrally therewith as a projection for restricting the movement of the spring sheet 10 in the radial direction. This is because the roller body 28 is not required to have a function for restricting the movement of the spring sheet 10 in the radial direction. Thus, the roller body 28 is allowed to be simplified in construction.

(7) Cam

As shown in FIG. 1 and FIG. 2, a cam 60 is a main element for converting the rotary movement of a motor into the vertical motion of the plunger 54 through the tappet structure body 6. Therefore, preferably, the cam 60 is inserted in rotation and held in a shaft-inserting hole 92a via a bearing body. Then, it is constructed so as to be revolved by driving an engine (cam shaft 3).

The cam 60 is preferably integrally provided with two cam portions 60 in parallel with each other with a predetermined distance in the axial direction with respect to the cam shaft 3 and located below the cylindrical space 92 of the pump housing 52.

(8) Fuel Inlet Valve and Fuel Outlet Valve

Preferably, a fuel inlet valve and a fuel outlet valve are arranged as exemplified in FIG. 4 and constituted as exemplified in FIGS. 10 to 11.

In other words, as shown in FIG. 10, the fuel inlet valve 73 is preferably constructed of a valve main body 19 and a valve body 20 having a collar portion 20b on its tip portion. Besides, as shown in FIG. 10, the valve main body 19 is preferably provided with a cylindrical fuel inlet chamber 19a opened downward and a fuel inlet hole 19b for feeding fuel into the fuel inlet chamber 19a.

Furthermore, preferably, the fuel outlet valve 79 comprises a valve body and is housed in part of the pump housing.

Then, preferably, the valve body is always energized by a spring in the valve-closing direction to supply a pressurized fuel to a common rail by opening and closing the valve.

Furthermore, as shown in FIG. 11, each of the fuel inlet valve 73 and the fuel outlet valve 79 comprises the valve main body 19, the valve body 20 movably attached in the inside of the valve main body 19, the fuel inlet chamber 19a provided in the inside of the valve main body 19, the fuel inlet hole 19b, the sheet portion 23 mutually contacted with the valve body 20 and part of the valve main body 19. Preferably, two or more fuel inlet holes 19b are formed and arranged in a non-radial pattern with respect to the fuel inlet chamber 19a.

This is because that such a fuel inlet valve supplies the fuel supply pump with fuel, for example, even at a flow rate of approximately 500 to 1,500 litters per hours quickly and quantitatively.

Likewise, the fuel outlet valve as constructed above also supplies the common rail with fuel, for example, even at a flow rate of approximately 500 to 1,500 litters per hours quickly and quantitatively.

(9) Lubrication System

Furthermore, a lubrication system of the fuel supply pump preferably employs, but not specifically limited to, a fuel lubrication system that utilizes part of a fuel oil as a lubrication component (fuel for lubrication).

This is because, when fuel is pressurized and fed under pressure into the common rail, particular problems are not generated because of using fuel for lubricating the cam chamber and so on, even though part of the fuel for lubricating the cam chamber and so on would be mixed with the fuel fed under pressure into the common rail. That is, because they have the same composition, there is no chance that additives and so on contained in a lubricant is mixed with the fuel fed under pressure into the common rail, unlike the lubricant used for lubricating the cam chamber and so on. Therefore, employing the fuel lubrication system prevents additive and so on contained in a lubricant from being mixed with fuel and injected into an engine. As a result, the exhaust gas purification is not allowed to be lowered.

2. Amplified Piston Common Rail System

Furthermore, the fuel supply pump of the present embodiment is preferably a part of a piston amplifying mechanical common rail system (APCRS) 100.

That is, as shown in FIG. 12, the fuel supply pump 103 is preferably constructed of a fuel tank 102, a feed pump (low pressure pump) 104 for supplying the fuel from the fuel tank 102, a fuel supply pump (high pressure pump) 103, a common rail 106 provided as a pressure accumulator for pressure-accumulation of the fuel fed under pressure from the fuel supply pump 103, a piston amplifier 108 (pressure amplifying piston), and a fuel injection system 166.

(1) Feed Pump and Fuel Supply Pump

The feed pump 104 is, as shown in FIG. 12, provided for feeding fuel (diesel oil) in the fuel tank 102 to the fuel supply pump 103 under pressure. It is preferable that a filter 105 is placed between the feed pump 104 and the fuel supply pump 103.

Preferably, the feed pump 104 has a gear pump structure mounted on the end of the cam shaft such that the feed pump 104 can be driven by directly connecting with the axis of the cam shaft or through an appropriate gear ratio.

Furthermore, the fuel fed under pressure from the feed pump 104 through the filter 105 is preferably supplied to the fuel supply pump 103 through a proportional control valve (FMU) 120 known in the art.

This proportional control valve can regulate the fuel fed to an inlet valve (not shown) of the fuel supply pump 103 under the control of the later-described electrical controlling unit (ECU).

In addition to feed the fuel supplied from the feed pump 104 to the proportional control valve 120 and the fuel supply pump 103 under pressure, it is preferable to construct that the fuel is returned to the fuel tank 102 through a overflow valve (OFV) 134 installed in parallel with the proportional control valve 120. Moreover, it is preferable that part of the fuel is fed under pressure to a bearing (not shown) of the fuel supply pump 103 and then used as a fuel lubricating oil of the bearing.

By the way, the fuel supply pump 103 is a device for pressurizing the fuel supplied from the feed pump 104 at high pressure as described above. The fuel supply pump 103 is preferably constructed such that, after pressurizing the fuel, the fuel is fed to the common rail 106 under pressure through the high pressure channel 107.

(2) High Pressure Path

Furthermore, as shown in FIG. 12, it is preferable to install a one way valve (not shown) on the outlet of the fuel supply pump 103, or both of the common rail 106 described below and the fuel supply pump 103.

This is because, by the one way valve, the fuel can be only fed from the fuel supply pump 103 to the common rail 106. Therefore, the adverse current can be effectively prevented even when the pressure of the fuel compression chamber 74 is lower than the pressure in the common rail 106. Consequently, a one way valve can be effectively preventing a decrease in pressure of the common rail 106.

(3) Common Rail

Furthermore, as shown in FIG. 12, the common rail 106 is connected to a plurality of injectors (injection valves) 110. Preferably, the accumulated pressure fuel at high pressure by the common rail 106 is injected into an internal combustion engine (not shown) from each of the injectors 110.

Furthermore, but not shown in the figure, the amount of discharge from each of these injectors 110 is preferably controlled through an injector driving unit (IDU). The IDU is connected to an electrical controlling unit (ECU) provided as a controller described letter. The IDU is driven by drive signals from the ECU.

Moreover, a pressure detector 117 is connected to the side end of the common rail 106 and a pressure-detection signal obtained by the pressure detector 117 is preferably sent to the ECU. That is, it is preferable to control an electromagnetic control valve (not shown) and also control the drive of IDU in response to the pressure detected when the ECU receives the pressure-detection signal from the pressure detector 117.

(4) Piston Amplifier

Furthermore, as exemplified in FIG. 13, a piston amplifier (pressure amplifying piston) is constructed of a cylinder 155, a mechanical piston 154, a compression chamber 158, an electromagnetic valve 170, and a circulation pathway 157. It is preferable that the mechanical piston 154 is equipped with a pressure-receiving portion 152 having a comparatively large area and a pressure portion 156 having a comparatively small area.

That is, the mechanical piston 154 housed in the cylinder 155 is pushed and moved by the fuel having a common rail pressure at the pressure-receiving portion 152. The common rail pressure of the compression chamber 158 is preferably adjusted to one that allows fuel having a pressure of approximately 30 MPa to be pressurized by the pressure portion 156 having a comparatively small area to make the pressure of the fuel in the range of 150 to 300 MPa.

Furthermore, for pressurizing the mechanical piston 154, a large amount of fuel having the common rail pressure is used. After pressurization, it is preferable to flow the fuel back to the fuel tank or the like through an electromagnetic driven overflow valve 170. That is, a major part of the fuel having the common rail pressure is pressurized by the mechanical piston 154 and then flows back to the fuel tank or the like together with spilled fuel from an electromagnetic valve 180 of the fuel injection system.

On the other hand, the fuel pressurized by the pressure portion 156 is fed to a fuel injection system (fuel injection nozzle) 163, effectively injected, and combusted.

Therefore, providing the piston amplifier as described above, the mechanical piston can be effectively pushed by the fuel having a common rail pressure without excessively increasing the size of the common rail.

That is, as illustrated in the schematic diagram of FIG. 14, according to the APCRS system, a mechanical piston is equipped with a pressure-receiving portion having a comparatively large area and a pressure portion having a comparatively small area. While considering the stroke of the mechanical piston, it is possible to effectively pressurize e fuel having the common rail pressure to a desired level with a small pressure. More concretely, the fuel from the common rail (pressure: p1, volume: V1, work load: W1) can be received by a pressure-receiving portion having a comparatively large area and then changed to higher-pressure fuel (pressure: p2, volume: V2, work load: W2) by a mechanical piston equipped with a pressure portion having a comparatively small area.

(5) Fuel Injection System

Furthermore, the configuration of the fuel injection system (fuel injection nozzle 110) 166 is, but not specifically limited to, preferably constructed as follows: As shown in FIG. 13, for example, the fuel injection system 166 comprises a nozzle body 163 including a seat surface 164 on which a needle valve body 162 can be placed, and an injection hole 165 formed on the downstream side from the valve body abutting portion of the seat surface 164. Preferably, it is constructed that the fuel supplied from the upstream side of the seat surface 164 at the time of lifting a needle valve body 162 is introduced into the injection hole 165.

Furthermore, such a fuel injection nozzle system 166 is preferably of an automatic opening and closing type, capable of lifting the needle valve body 162 by means of hydraulic pressure of the fuel sent from the upstream side. In this period, the needle valve body 162 is always energized toward the seat surface 164 by the spring 161 and opens and shuts the needle valve body 162 by switching energization/no energization of solenoid 180.

Furthermore, as to a time chart of high-pressure fuel injection, it is preferable to indicate a fuel injection chart having two-staged injection conditions as indicated by the solid line as exemplified in FIG. 15.

This is because such a two-stage injection timing chart can be attained by a combination of the common rail pressure and amplification with a piston amplifier (pressure amplifying piston), and thus the combustion efficiency of fuel can be raised, while cleaning an exhaust gas.

Furthermore, according to the present invention, it is also preferable to indicate a fuel injection chart as indicated by the dashed line B in FIG. 15, a combination of the common rail pressure and amplification with a piston amplifier.

By the way, when the piston amplifier is not used, the conventional injection timing chart becomes a single-stage injection timing chart with a low injection amount as indicated by the dashed line C in FIG. 15.

(6) Movement

Next, the fuel supply pump 103, the actions of the piston amplifier 108, and the fuel injection system 166 in the present embodiment will be described with reference to FIGS. 12 and 13. That is, as shown in FIG. 12, at the time of operating the fuel injection system (fuel injection nozzle 110) 166, the fuel in the fuel tank 102 is supplied from the feed pump 104 to the fuel supply pump 103. Furthermore, the high-pressure fuel is preferably supplied from the fuel supply pump 103 to the high pressure channel 107 under pressure.

Subsequently, as shown in FIG. 13, the fuel is subjected to pressure accumulation at approximately 50 MPa in the common rail 106 and then the fuel is preferably pressurized under ultra-high pressure conditions of 150 MPa or more as the piston amplifier 108 is provided between the common rail 106 and the fuel injection valve 110.

In the present embodiment, an extremely high flow rate of fuel is used for operating the piston amplifier 108. Therefore, as an example shown in FIG. 13, the plunger barrel and the pump housing provided in the fuel supply pump effectively function.

That is, the projection for supporting the upper end of the return spring is provided in the plunger barrel instead of being provided in the pump housing, allowing the inner peripheral surface of the pump housing to be processed precisely and easily. As a result, because the cam shaft can be set at a higher rotational frequency, a high flow rate of fuel that is sufficiently pressurized is allowed to be supplied into an accumulator. Consequently, for example, the high-pressurization of an APCRS (Amplified Piston Common Rail) becomes possible. In addition, high power of a diesel engine, improvement in fuel consumption, reduction in particulate matters, and so on can be attained.

Industrial Applicability

According to the fuel supply pump of the present invention, the projection is constructed so as to support the upper end of the return spring. Thus, a projection for supporting the upper end of the return spring in the inner peripheral surface of the pump housing is not required.

Furthermore, the inner peripheral surface of the pump housing can be processed easily and precisely. Therefore, the cam shaft can be set at a higher rotational frequency. Thus, a high flow rate of fuel that is more sufficiently pressurized than a conventional one can be supplied into an accumulator. Consequently the high power of a diesel engine, improvement in fuel consumption, reduction in particulate matters, and so on can be attained.

Claims

1. A fuel supply pump comprising:

a pump housing having a cylindrical space opened from end to end in the vertical direction;

a plunger barrel installed in the upper opening portion of the pump housing;

a plunger for pressurizing fuel, installed in the plunger barrel and the cylindrical space of the pump housing so as to be allowed to move up and down;

a cam installed in rotation way below the plunger and integrated with a cam shaft inserted into the pump housing;

a tappet structure body installed between the cam and the plunger and provided for transmitting a upward or downward movement of the cam caused by the rotation of the cam shaft to the plunger; and

a return spring for setting lowering force to the plunger, installed between the tappet structure body and the plunger barrel,

wherein the plunger barrel has a projection for supporting the upper end of the return spring.

2. The fuel supply pump as described in claim 1, wherein

the plunger barrel has a large diameter portion for restricting the movement of the return spring in the radial direction.

3. The fuel supply pump as described in claim 1, wherein

the projection of the plunger barrel has an outer peripheral surface fitted to the peripheral surface of the cylindrical space of the pump housing.

4. The fuel supply pump as described in claim 3, wherein

the plunger barrel has a seal ring receiver in the outer peripheral surface of the projection.

5. The fuel supply pump as described in claim 1, further comprising:

a spring sheet having an opening portion for penetrating the plunger there into is provided between the return spring and the tappet structure body: and

a spring holding portion for restricting the downward movement of the return spring is provided in the outer peripheral surface of the spring sheet.

6. The fuel supply pump as described in claim 1, wherein

the tappet structure body further includes a cylindrical shell having an outer peripheral surface fitted to the peripheral surface of the cylindrical space of the pump housing and the inner peripheral surface of the shell is provided with an projection for restricting the movement of the return spring in the radial direction.

7. The fuel supply pump as described in claim 1, wherein

the fuel supply pump is used in an accumulator fuel injection device for pressurizing fuel at a flow rate of 500 to 1,500 litters per hour to a value of 50 MPa or more.