ES2543318T3 - Fuel pump - Google Patents

Abstract

A fuel pump (1) for pressurizing fuel in a high pressure fuel injection system, the fuel pump (1) comprising: a pump head (7) having a pumping chamber (7a) extending disposed to receive the fuel to be pressurized; a pumping element (8) arranged to respond reciprocally to the movement of a drive element (10), the pumping element (8) defining, in part, the pumping chamber (7a) such that, in use , when the pumping element (8) reciprocates, a force, transferred from the driving element (10), is applied to the fuel inside the pumping chamber (7a) to pressurize the fuel; a frame (12) arranged to hold the drive member (10) and the head (7) of the pump; and a cover (3) defining an internal volume (5) for containing fluid; in which at least a part of the frame (12), at least a part of the driving element (10) and at least a part of the pumping element (8) are received in the cover (3).

Description

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DESCRIPTION

Fuel pump

Field of the Invention

The present invention is related to the field of fuel pumps. In particular, the invention relates to a high pressure fuel pump for supplying high pressure fuel to a fuel injector. More specifically, but not exclusively, the present invention relates to a housing for such a pump.

Background of the invention

Fuel injection systems for modern internal combustion engines, in particular engines using compression ignition, comprise a multitude of fuel injectors arranged to deliver an atomized fuel spray to a respective combustion chamber for combustion.

In order to improve the atomization of the fuel within the engines that use compression ignition, it is preferable to atomize the fuel as much as possible. Increased fuel atomization improves the efficiency of the combustion process, which in turn improves fuel efficiency and reduces harmful emissions such as carbon monoxide produced by the combustion process. The most common way to improve atomization is to increase the pressure at which the fuel is injected. Therefore, there has been a continuing desire to manufacture pumps capable of pressurizing fuel at higher pressures.

Known high-pressure pumps use a pumping element such as a steel piston that moves alternately within an adjusted bore guide, the piston being driven by a transmission shaft. Therefore, as the drive shaft rotates, its rotational force is transferred to the plunger so that the plunger moves alternately within the bore of the guide. The fuel enters a pumping chamber at one end of the bore of the guide and is then pressurized, when the reciprocating piston applies a pressurizing force to the pumping chamber. The fuel is then forced through a supply valve into a high pressure rail, ready for injection by the fuel injectors. The pump components are held by the housing. Document DE 10 2008 007028 describes a fuel pump that includes a plate arrangement that compensates forces between a pumping element and a driving element.

In order to increase the fuel pressure that a high-pressure fuel pump is capable of providing, greater energy must be put into the system through the rotating drive shaft so that the plunger applies a force greater than the fuel. Therefore, as the pressures that the pumps are capable of providing have increased, so must the relative resistance of the pump casing due to the increase in physical energy used within the pump.

It is common to manufacture high pressure fuel pump housings from cast steel to provide the force necessary to resist the stresses that high pressure fuel pumps undergo. As pumps capable of producing higher pressure fuel have been developed, the thickness of the steel casing has also increased to withstand stress-related increases.

Increasing the thickness of a cast steel pump housing results in the pump being heavier. As such, the fuel efficiency of the vehicle in which the pump is used is reduced because the heavier components have to be transported. In addition, as the thickness of the casing of the molten steel pump increases, so does the total size of the pump.

It would be desirable to provide a high pressure fuel pump that is of reduced weight and size. This is particularly relevant in vehicles with the concept of "eco-efficiency", in which the overall reduction of a vehicle's weight is a key component in improving efficiency to reduce the environmental impact of the vehicle. In addition, it is desirable to minimize the size of a pump, because such a pump occupies less space inside a vehicle.

The embodiments of the present invention, therefore, are intended to at least partially mitigate one or more of the problems mentioned above.

Compendium of the invention

According to a first aspect of the present invention, a fuel pump is provided for pressurizing fuel in a high pressure fuel injection system. The fuel pump comprises a pump head that has a pumping chamber that is arranged to receive the fuel to be pressurized. The fuel pump also includes a pumping element arranged to move alternately in response to the movement of a drive element. The pumping element defines, in part, the pumping chamber so that, in use, when the pumping element moves alternately, it is

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applies a force, transferred from the drive element, to the fuel inside the pumping chamber to pressurize the fuel. The fuel pump also comprises a frame arranged to hold the drive element and a cover that defines an internal volume for containing fluid. At least one piece of the frame, at least one piece of the drive element, and at least one piece of the pumping element are received in the cover. This arrangement, therefore, provides a smaller, lighter pump.

The frame and cover together provide a pump housing.

The frame can be arranged to keep the pump head and the drive element in fixed positions with respect to each other. Such an arrangement allows the proper functioning of the fuel pump. In particular, a large force is transferred from the drive element to the pump head in order to pressurize fuel inside the pump head at a very high pressure. Therefore, the frame has to resist such forces and keep the pump head and drive element in fixed positions relative to each other so that the pump continues to function properly.

The frame can be constructed from a material that has greater strength than a material from which the roof is constructed. The frame is provided to hold the pump head and drive element, at the same time as the cover for containing fluids is provided. Therefore, only the frame has to withstand the high forces transferred from the drive element to the pump head. Therefore, the cover can be made of a material of lower resistance than the frame, since it only has to contain fluid. Alternatively, the frame and cover can be made of the same material and the frame can be made thicker than the cover to provide the greatest strength. Preferably, the frame is made of aluminum because aluminum is relatively strong compared to other materials, while it has relatively low density compared to other materials.

The materials for the frame and cover can be selected in such a way that they are optimized for their specific function. The material for the frame can be selected such that it is of a sufficiently high strength to withstand the forces transferred from the drive element to the pump head. Cover material can be selected to contain fluid.

The frame can be formed in a single piece. Forming the frame from a single piece allows the frame to be stronger because it has no union, which can lead to structural weaknesses. In addition, the frame can be formed in a single piece by means of an extrusion process. Such an extrusion process provides an easy means to manufacture a single piece frame. In addition, such an extrusion process allows additional functions, such as screw holes, which are easily formed within the frame.

The cover can be formed of a material based on plastics. Such an arrangement results in a lightweight and easy to manufacture cover.

The frame can be arranged to mount the fuel pump on an engine component. The frame holds the high-stress components of the fuel pump. Therefore, it is desirable to mount the fuel pump using the high strength frame of the fuel pump.

The fuel pump can also comprise a mounting arrangement for connecting the fuel pump frame to the engine component. The mounting arrangement provides means to provide a strong connection between the frame and the engine component.

The housing and the mounting arrangement may each comprise a complementary interference feature arranged to prevent rotation of the mounting arrangement with respect to the housing. For example, the cover and the mounting arrangement may each comprise a complementary interference feature arranged to prevent rotation of the mounting arrangement with respect to the cover. When the fuel pump is running, great forces are transferred between the drive arrangement and the pump head. The forces applied by these components result in the fuel pump frame being attempted to move in response to these forces. Therefore, it is advantageous to include complementary interference features that will prevent rotation between the frame and the mounting arrangement, thereby helping to keep the fuel pump securely in position.

One of the complementary interference characteristics may comprise a projection and the other complementary interference characteristic may comprise a recess. Such interconnected interference characteristics provide a strong connection between the frame and the mounting arrangement.

The cover may comprise one or more integrated components. The one or more integrated components may include a leakage return device to facilitate fluid recirculation. The one or more integrated components may include a fuel inlet to supply fuel to the fuel pump. The one or more integrated components may include both the leakage return device and the fuel inlet. Providing these components integrated within the housing provides a smaller and easier to manufacture fuel pump.

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The drive element can be formed from a multitude of parts that include a shaft part and a cam part. Such an arrangement is advantageous when a frame formed of a single piece is used. The cam part can be constructed from a material of higher strength than the shaft part. This is because the cam part supports most of the load that is transferred to the pump head to pressurize the fuel. Such an arrangement provides a cheaper manufacturing of the drive element since only the expensive strong material is used for the part that requires a strong material.

The pump head can be received inside the cover. Including the pump head inside the cover improves the cooling of the pump head.

The embodiments of the invention provide a high pressure fuel pump that is lighter in weight than the current known pumps. A high strength frame is provided to support the pumping loads by supporting the high stress parts of the pump, such as the cam arrangement and the pump head, and a light weight cover is then provided to seal the pump to prevent fuel leakage from the pump.

Embodiments of the invention provide a high pressure fuel pump that is smaller than known fuel pumps. Such embodiments utilize a support frame and a light weight cover. The cover can be relatively thin, and as such, the overall thickness of the housing is reduced, because only a strong support of the frame is provided, instead of a strong housing that encloses the entire pump.

The embodiments of the invention reduce the cost and time to prototype new pumps. In particular, the frame can be extruded from metal and a molded plastic shell can be used to build the cover. Such techniques do not require the slow and expensive arrangements necessary to build a cast steel housing.

Brief description of the drawings

The embodiments of the present invention will now be described, by way of example only, with respect to the accompanying drawings, in which similar numerical references are used for similar parts, and in which:

Figure 1 illustrates a cross-sectional view of a pump according to a first embodiment of the present invention;

Figure 2 provides an exploded view of the pump of Figure 1;

Figure 3 illustrates a frame of a pump housing of the pump of Figure 1;

Figure 4 illustrates a pump cover of Figure 1;

Figure 5 provides an exploded view of a pump fixing arrangement in Figure 1;

Figure 6 provides an exploded view of the fixing arrangement of Figure 5 from an alternative angle;

Figure 7 provides an exploded view of the cam arrangement illustrated in Figures 1 and 2; Y

Figure 8 provides an exploded view of an alternative cam arrangement.

Detailed description of embodiments of the invention

First, reference will be made to Figures 1 and 2, which provide two alternative views of a pump 1 provided according to a first embodiment of the present invention. Initially the pump 1 will be described mainly with respect to its operation.

The low pressure fuel enters the pump 1 through a fuel inlet 2, which is integrated into a cover 3 of the pump 1. The fuel then passes through an inlet metering valve (IMV) 4a of a arrangement of the IMV 4 mounted on the cover 3, which controls the rate of fuel flow in the pump 1. The cover 3 forms part of a pump housing and defines an internal cavity 5 in which the pumping components are arranged and actuation of the pump 1, the internal cavity 5 being filled with fuel. The arrangement of the IMV 4 is partially arranged between the fuel inlet 2 and the internal cavity 5; therefore, the fuel passes from the fuel inlet 2 through the IMV 4a and into the internal cavity 5.

The fuel inside the internal cavity 5 acts as a lubricant of the moving parts of the fuel pump 1, and also acts to cool the components of the pump 1 by absorbing the heat generated in the pumping process, such that the Heat is transferred out of the pumping components of the pump 1. In order to facilitate the cooling process a leakage return device 6, such as a venturi device, is provided to allow the fuel to be removed from the internal cavity 5 and return to a cam box

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of the engine or low pressure drain, so that the fuel is recirculated. The leakage return device 6, therefore, aids in the recirculation of the fuel such that the heat generated by the pumping components is transferred outside the fuel pump 1.

The pumping components include a pump head 7, a pumping element in the form of a piston 8 and an actuation arrangement comprising a follower arrangement 9 and a drive shaft or cam arrangement 10. The pumping process has place inside pump head 7. The pump head, therefore, is made of a strong material, such as hardened steel, in order to resist the high pressure fuel that is pressurized within a pumping chamber 7a of the pump head 7, in addition to the large forces applied to the pump head 7 by the pumping element 8 in order to pressurize the fuel.

The pumping chamber 7a of the pump head 7 is disposed at one end of an bore 7b of the plunger provided in the pump head 7 and is a cavity comprising a low pressure fuel inlet (not shown) to receive fuel from the internal cavity 5 defined by the cover 3, and a high pressure fuel outlet (not shown) in the form of an outlet valve. The pumping chamber 7a is defined in part by a pumping head at a first end of the piston 8. The piston 8 is arranged to move alternately so that a pumping head of the piston increases and decreases the volume of the pumping chamber 7a . As the volume of the pumping chamber decreases, the fuel pressure inside the pumping chamber 7a increases. When the fuel inside the pumping chamber 7a reaches a predetermined pressure, the outlet valve opens allowing the high pressure fuel to pass through it to a high pressure rail (not shown) in which the fuel is Store ready for injection by one or more fuel injectors (not shown).

At a second end of the piston 8, away from the pumping chamber 7a, the follower arrangement 9 is arranged to collaborate with the cam arrangement 10 to transform a rotating movement of the cam arrangement 10 into the alternative movement of the piston 8 within the bore 7b of the plunger.

The cam arrangement 10 is provided with a shaft part 10a located at least partially outside the cover 3 of the pump 1 to engage with a drive source (not shown), such as a drive gear. The cam arrangement 10 rotates in response to the input force provided by the drive gear. The shaft part 10a of the cam arrangement 10 is also partly located inside the inner cavity 5 of the cover 3, and has a cam part 10b connected on the shaft 10a in a part inside the inner cavity 5.

The follower arrangement 9 comprises a roller 9a that abuts the cam 10b so that the roller 9a and the cam 10b are communicatively coupled. The roller 9a is held inside a roller shoe 9b connected to the second end of the piston 8. When the cam 10b rotates, the roller 9a rotates inside the roller shoe 9b. The arrangement of the roller 9a and the roller shoe 9b limits the transfer of lateral movement from the cam 10b to the plunger 8, while transmitting the alternative movement of the cam 10b to the plunger 8. A spring 11 is held in position between the head 7 of the pump and a spring seat 8a mounted on the piston 8, in order to urge the piston 8, and the roller shoe 9b connected thereto, to the contact with the cam 10b. Due to the spring 11, the follower arrangement 9 continuously follows the alternative movement of the cam 10b.

The follower arrangement 9 also includes a shoe guide 9c, which is provided around the peripheral surface of the roller shoe 9b, in order to guide the movement of the shoe 9b of the roller. Therefore, the guide 9c allows the roller shoe 9b to move along the axis of the plunger 8, which allows alternative movement, but restricts the lateral movement, of the shoe guide 9c. The rotation of the cam arrangement 10 exerts a lateral force on the follower arrangement 9 and hence the guide 9c of the shoe is constructed of a strong material in order to resist such lateral movement and resist the stress associated with such resistance.

Although the aforementioned follower arrangement 9 has been described as a roller-based arrangement, it will be appreciated that any suitable tracking arrangement could be used (for example a stem or other intermediate drive component).

The pump housing includes a frame 12, in addition to the cover 3. The frame 12 is provided to hold various drive and pump components, in particular, the pump components 7, 9, 10 that are subjected to high levels of effort due to the pumping process. Therefore, the frame 12 is arranged to hold the pump head 7, the roller shoe 9 and the shaft 10a of the cam arrangement 10. The frame 12, therefore, is made of a relatively strong material, such as aluminum, in order to withstand the high levels of stress within the pump 1, particularly due to the forces that are transferred from the cam arrangement 10 to the piston 8 and then the fuel inside the pump head 7.

In order to facilitate the rotation of the cam arrangement 10, and avoid excessive loading and wear on the frame 12, the bearings 13a, 13b are provided in the parts of the frame 12 that hold the cam arrangement 10.

As can be seen in Figure 2, a mounting arrangement 14 is provided with a mounting plate 14a external to the cover 3 that connects the pump 1 to the motor. The mounting arrangement 14 is connected to the frame 12 a

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through the cover 3 in order to provide a solid support for the frame 12 and therefore to the pump 1. Since the frame 12 and the mounting arrangement 14 are connected through the cover 3, the mounting arrangement 14 includes a multitude of seals 14b, 14c in order to prevent fuel leakage through the cover

3.

Each of the components of the pump 1 will now be described in more detail with respect to different figures.

The construction of the frame 12 will be further discussed with reference to Figure 3, which shows the pump frame 12 of the first embodiment of the present invention.

The frame 12 is provided with two sections 12a, 12b for holding the cam, each of which defines a hole 12c, 12d through which the arrangement 10 of the cam (shown in Figures 1 and 2) can be held ), in which the cam 10b is placed between the two clamping sections 12a, 12b of the cam. The holes 12c, 12d defined by the cam holding sections 12a, 12b respectively are shaped so as to complement the outer surface of the shaft 10a of the cam arrangement 10. Therefore, in this case the holes 12c, 12d are circular to complement the cylindrical shape of the shaft 10a of the cam arrangement 10. Therefore, a smooth rotation of the arrangement 10 of the cam is possible. The dimensions of the frame 12 are arranged so that within the holes 12c, 12d defined by each of the clamping sections 12a, 12b, one of the bearings 13a, 13b can be placed in order to facilitate rotation of the axis 10a of the arrangement 10 of the cam. The fuel in the internal cavity 5 defined by the inner walls of the cover 3 helps to lubricate the frame 12 and the bearings 13a, 13b in order to facilitate smooth rotation of the shaft 10a of the cam arrangement 10 and minimize wear . The cam clamping sections 12a, 12b support most of the weight and effort of the cam arrangement 10. However, the mounting arrangement 14 supports a part of the load applied to the cam holding section 12a that is adjacent to the mounting arrangement 14.

The frame 12 is also provided with a section 12e holding the pump head. This section 12e has a hole 12f to receive the pump head 7. In particular, a front face of the pump head 7 protrudes, at least partially, through this hole 12f. The front face of the pump head 7 includes a recess that defines, in part, the pumping chamber 7a into which the pumping head of the piston 8 is inserted to thereby define the pumping chamber 7a.

A multitude of screw holes 12g (only one shown in Figure 3) are provided in section 12e of the head pump holder of the frame 12, through which the screws (not shown) can connect the head 7 from the pump to the frame 12. A strong fixation of the pump head 7 to the frame 12 is required in order to prevent the head 7 from separating the pump from the frame 12 when the piston 8 is operated inside the head 7 of the pump, such that a force is provided that urges the pump head 7 out of the frame 12. Alternatively, the frame 12 could be arranged to provide at least one fastener (not shown) that stops with a rear face of the pump head so that it does not depend on the connection screws to secure the pump head 7 in the frame 12.

The frame 12 is also provided with sections 12h for securing the shoe guides (only one shown), which include a multitude of struts (not shown) that holds the shoe guide 9c.

The sections 12a, 12b of the cam holder, the section 12e of the pump head and the sections 12h of the shoe guide are joined together by the main frame structure 12. Structural rigidity is required between these sections 12a, 12b, 12e, 12h, and in particular in the sections 12a, 12b of holding the cam and in the section 12e of holding the pump head because the pressurization of the fuel is achieved by movement relative of the piston 8, actuated by the arrangement 10 of the cam, inside the head 7 of the pump. Therefore, the position of the pump head 7 with respect to the arrangement 10 of the cam needs to remain constant in order to allow the correct operation of the pump 1.

The holes or cutouts 12i are provided within the main body of the frame 12 in order to reduce the weight of the frame 12 without reducing the relative strength of the frame 12 so that the frame 12 is able to provide a strong hold on the components of The pump subjected to high levels of effort.

It will be appreciated that while the sections 12a, 12b of the cam holder, the section 12e of the pump head and the sections 12h of the shoe guide are held by the main body of the frame 12 in this embodiment of the invention, alternatively, strut fasteners could be provided between each of the sections of the frame 12 in order to link the sections together. The use of strut fasteners between the sections of the frame 12 could help to further reduce the weight of the frame 12, and in certain arrangements allow a reduction in the size of the frame 12.

In this example, the frame 12 is also provided with fixing holes 12j, 12k, 12l, 12m to connect the pump 1, through the frame 12, to the mounting arrangement 14. The holes 12j, 12k, 12l, 12m and their relationship with the mounting arrangement 14 will be discussed when the mounting arrangement 14 is described in detail with respect to Figures 5 and 6.

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The frame 12 is manufactured by extruding an aluminum bar. The extrusion process is fast and cheap to perform. By forming the frame 12 by an extrusion process, the frame 12 can be formed in one piece. That is, it is extruded from a single metal bar and, as such, there are no pieces that have to be joined. On the contrary, casting processes require two or more pieces that melt, which then join together. There is a risk of structural weaknesses forming at the junctions between these pieces. Therefore, the extrusion process overcomes these problems.

In addition, since the frame 12 is extruded, the amount of cutting and drilling of the frame is minimized. In particular, the extrusion process allows certain features of the frame 12, such as holes, to be formed in the frame 12 during the extrusion process. In contrast, casting techniques require that all features be added after casting, which leads, therefore, to new structural weaknesses.

It will be appreciated that although it is described that the frame 12 is made of aluminum, any suitably strong material could be used. In particular, any suitable metal or other materials such as a composite plastic or a composite encapsulation made of sintered metal could be used. It is noted that although an extrusion process is preferable for the construction of the frame 12, other construction processes such as smelting could be used.

The cover 3, which defines the internal cavity 5, is arranged to enclose the frame 12 and the pump and drive components that hold the frame 12. In other words, the pump and drive components are arranged, at least partially, within the internal cavity defined by the frame 12. The cover 3, therefore, provides a fluid tight housing around the pumping components such that the fuel does not escape from the internal cavity.

While in Figure 1 the cover 3 is shown to enclose all the pumping and actuating components of the pump 1, it will be appreciated that the cover 3 is arranged to define an internal cavity that contains fuel for cooling and lubrication purposes. The mobile pumping and actuating parts of the pump 1, such as the piston 8, the follower arrangement 9 and the arrangement 10 of the cam, therefore, require such lubrication and cooling. As such, it will be appreciated that it is not necessary to enclose within the cover 3 the assembly of the pump head 7. The cover could be provided so that it was attached to a peripheral surface of the pump head 7 or to the front face of the pump head 7. In such circumstances, the front face of the pump head 7 would be in fluid communication with the fuel within the internal cavity 5, and at least part of the side part and the rear part assembly of the head 7 of the pump would be external to the cover 3. It is observed that due to the constant flow of fuel through the pump head, the heat generated inside the pump is, at least in part, transferred away by the pressurized fuel, and by therefore the cooling of the pump head is not as important as the cooling of the mobile components of the pumping process.

The cover 3 is composed of two pieces 3a, 3b, as shown in Figure 2. The pieces 3a, 3b are arranged to fit around the components connected to and inside the frame 12. The two pieces 3a, 3b of the cover plastic can then be joined together, so that the two-piece cover 3 seals the fluid inside. The two pieces can be joined by any method capable of providing a fluid tight seal.

Figure 4 shows a half 3a of the cover 3. In Figure 4, it can be seen that the cover 3 has a multitude of internal support struts 3s. The support struts 3s harden the cover 3 to improve the strength of the cover 3. As such, it is possible to have a thinner cover 3, while still providing sufficient strength. The struts 3s could also be provided to abut the outer surface of the frame 12 so that the cover 3 is firmly formed around the frame 12.

In this embodiment of the invention, the frame 12 only joins the cover 3 through the mounting arrangement

14. However, it will be appreciated that the cover 3 could be connected to the frame 12 in several ways, such as by the use of one or more connecting screws having the proper seal to prevent leakage of the cover 3.

The two pieces 3a, 3b of the cover are formed from plastic using an injection molding technique. Therefore, high frequency welding would provide adequate bonding between the two pieces 3a, 3b. However, 3 other materials, such as a metal, could be used for the cover. For example, a frame 12 and an aluminum cover 3 could be provided. Since the cover 3 only needs to provide fluid tightness, it could be manufactured much thinner than the frame 12. In addition, due to the relative strength of the metal compared to the plastic, a metal cover 3 could be manufactured much thinner than a cover 3 plastic Due to its conductive properties, a metal cover 3 could also assist in heat transfer away from the fuel inside the internal cavity.

Although in the embodiment of the invention described with respect to Figures 1 and 2 the internal cavity 5 defined by the cover 3 is filled with fuel, it will be appreciated that other fluids could be provided within the internal cavity 5. For example, it could be contain a specific cooling / lubrication fluid within the

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internal cavity 5. In such circumstances the arrangement of the IMV 4 would be connected directly, or through a content channel, from the fuel inlet 2 to the pump head 7. In such an arrangement, a cooling fluid inlet (not shown) could be provided, and the leakage return device 6 would help to recirculate the cooling fluid.

In addition to defining the internal cavity 5, the cover 3 also defines various characteristics of the fuel pump 1, as discussed below.

The cover 3 includes a connection part 3b of the IMV, which is arranged to allow the housing of the arrangement 4 of the IMV to be connected to the pump 1. The connection part 3b of the IMV defines a hole 3c in which a part of the arrangement of the IMV 4 can be positioned, so that the IMV 4a can be connected to the fuel inlet 2. One or more connection holes 3d can be provided inside the cover 3 to allow the arrangement 4 of the IMV can be attached to the cover, so that the arrangement 4 of the IMV is held in place in the pump 1.

The cover 3 also provides an integrated leakage return device 6 and an integrated fuel inlet 2. Integrating these components into the cover 3 is advantageous when the cover 3 is constructed from plastic using an injection molding method, since the components are formed as part of the cover 3 in the molding process. Furthermore, integrating these components into the cover 3 simplifies the complete manufacturing process of the fuel pump 1 and reduces the size of the fuel pump 1.

The housing, which includes frame 12 and cover 3, is much smaller than known housings. This is because the minimum structural support required can be provided by the frame 12, and then a comparatively thin and light cover 3 can be provided that provides a fluid-tight seal for the pump 1. In general, this allows the total size of the housing and therefore of the pump 1. In addition, the materials used for the frame 12 and the cover 3 can be selected so as to better adapt to their respective functions, which allows the weight of the housing and, therefore, of the pump 1.

A further advantage of such a carcass construction is that it is possible to place the IMV arrangement 4 much closer to the pump head 7 than is possible in a fuel pump using a steel housing molten. This is because the frame 12 can be provided only in those parts that require clamping, and the cover 3 can be arranged to closely surround this frame 12, which allows the arrangement 4 of the IMV to be placed near the head 7 of the pump . Therefore, the head 7 of the pump as a whole can be further reduced.

Although it has been described that the frame 12 is disposed within the previous cover 3, it will be appreciated that the frame 12 could be provided so that it is only partially within the cover 3. For example, the main structure of the frame 12 could be provided outside the cover 3 with clamping arms that extend through the cover 3 to hold the high-stress components of the pump 1. In this case, the arrangement of Mounting 14 can be easily connected to the frame 12, or even formed integrally with the frame 12.

The mounting arrangement 14 shown in Figure 2 with respect to Figures 5 and 6 will now be described in more detail.

The mounting arrangement 14 comprises a mounting plate 14a, which is arranged to be connected to a motor component to secure and stabilize the pump 1. The mounting plate 14 is a substantially flat structure with a multitude of holes or cuts to reduce the plate weight 14a. The mounting plate 14a is provided with a multitude of screw holes 14d, 14e, 14f for screws (not shown) to connect the mounting plate to the motor. Additional holes 14g, 14h, 14i, 14j of screws are provided to allow the mounting plate 14 to be connected by screws, through the holes, in the cover 3 and connected to the frame 12. Thus, a face of the mounting plate 14a to sit flush against the cover 3, connected through the cover 3 to the frame 12, so that the cover 3 is held between the plate mounting plate 14a and the frame 12.

Because the screws for connecting the mounting plate 14a to the frame 12 pass through the cover 3, it is necessary to provide sealing means of the mounting arrangement. This is achieved by providing the first and second gaskets 14b, 14c, which seal the space between the mounting plate 14a and the cover 3, and the space on the outer surface of the mounting plate 14a, respectively.

The first seal 14b takes the form of a gasket that is placed between the mounting plate 14a and the cover 3. The gasket 14b is arranged such that it surrounds all the screw holes in the cover 3 and the 14g, 14h, 14i , 14j on the mounting plate 14, whereby an internal cavity is created between the mounting plate 14a and the cover 3 for the fluid. The gasket 14b is fixed between the mounting plate 14a and the cover 3, together holding the frame 12 and the mounting plate 14a due to the screws. Therefore, the gasket 14b provides a fluid tight seal between the cover 3 and the mounting plate 14a. Alternatively, the first seal could be provided by a multitude of joints, each provided around a single screw hole.

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The second seal 14c takes the form of an O-shaped rubber gasket and is disposed on an outer surface of the mounting plate 14a. The O-shaped seal 14c prevents fuel leakage from around the screw heads that pass through the mounting plate 14a.

To prevent rotation of the housing with respect to the mounting plate 14a, the cover 3 is provided with a multitude of projections 3m, which are arranged to engage with a multitude of complementary recesses 14k within the mounting plate 14a. In use, this arrangement of the cover 3 and of the mounting plate 14a helps to prevent the rotation of the mounting plate 14a with respect to the cover 3. Therefore, this feature of the mounting arrangement 14 provides interference that it is radial with respect to the axis 10a of the arrangement 10 of the cam, in order to help prevent the rotation of the mounting arrangement 14.

It will be appreciated that the radial interference characteristics provided between the cover 3 and the mounting plate 14a could include more protrusions in the frame 12 that protrude at the rear of the projections 3m in the cover 3. Thus, the frame 12 would hold the 3m protuberances and therefore would provide additional resistance to the relative rotation of the housing and mounting plate 14.

The mounting plate 14a can be extruded from an aluminum bar. Such manufacturing process is cheap and fast. However, any suitable material and manufacturing process could be used.

The construction of the arrangement 10 of the cam shown in Figures 1 and 2 will now be considered in more detail with respect to Figure 7.

In general, known drive shafts are constructed from a single piece of metal and secured by a two-piece cast steel housing, which is constructed around the drive shaft. However, when used with an extruded aluminum frame or any fixed frame structure, it is not possible to use a standard drive shaft.

In the embodiment of the invention shown in Figures 1 and 2 an arrangement 10 of the multi-piece cam is provided. The arrangement 10 of the cam includes three parts: the shaft 10a, the cam 10b and a rear support stump 10c. The shaft 10a extends along the length of the arrangement 10 of the cam and the cam 10b and the rear support stump 10c are mounted thereon, so that the arrangement 10 of the cam can be constructed within the frame fixed 12.

The axis 10a is an elongated structure with a cylindrical stepped shape, which has a multitude of cylindrical pieces, which are reduced in diameter towards one end of the axis 10. The axis has a first part 10aa of reduced diameter on which the cam 10b is it adjusts under pressure, and a second section 10ab of reduced diameter neighboring at one end of the shaft 10a on which the rear support stump 10c is adjusted under pressure. The second section 10ab of reduced diameter has a smaller diameter than the first section 10aa of reduced diameter.

In order to mount the cam arrangement 10 within the frame 12, it is first necessary to insert the cam 10b through the space between the two clamping sections 12a, 12b of the cam of Figure 3. Next, the shaft 10a it is inserted through the first section 12a of the cam holding of the frame 12 and through the cam 10b and in the rear support stump 10c which is arranged to hold the shaft 10a inside the second section 12b of the cam holding of the frame 12.

Figure 8 shows an arrangement 100 of the alternative cam, which uses a key interference joint. In this embodiment of the invention, the arrangement 100 of the cam includes a shaft 100a, a cam 100b, a rear support stump and two coupling elements (or keys) 100d, 100e. The shaft 100a and the cam 100b are provided with recessed parts 100aa, 100ba, 100bb (or keyways) with which the coupling elements 100d, 100e are coupled. The coupling elements 100d, 100e, therefore, act as intermediate connecting pieces that provide a joint or bridge between the shaft 100a and the cam 100b, in order to help prevent the parts of the arrangement 100 of the cam move out of position relative to each other. The arrangement 100 of Fig. 8, therefore, provides an arrangement 100 of the drive shaft that is stronger than the aforementioned arrangement 10 that depends on the pressure adjustment of the parts.

It will be appreciated that although the pressure adjustment and key interference adjustment arrangements have been described, the cam arrangement parts could be connected by any suitable means such as serial interference, thermal expansion interference, a striated or hydroconformed interference.

The construction of the arrangement 10, 100 of the cam from multiple pieces makes it possible to build a cheaper arrangement of the cam compared to a drive shaft made of one piece. In particular, the cam 10b, 100b can be made of high strength steel, since it takes most of the effort and then the axle and the rear support stump can be made of cheaper grade steel.

The arrangement 10 of the cam of the illustrated embodiment serves as a driving element of the pump to transfer a driving force to the pumping element to pressurize fuel inside the pump head. It will be appreciated that other drive elements could be contemplated.

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For example, although the use of a fixed frame 12 with an arrangement 10 of the cam made of multiple pieces has been described herein, it will be appreciated that in certain circumstances it may be preferable to use a drive element comprising a transmission shaft of a single piece and a frame made of multiple pieces.

The invention has been described with the use of a linear pumping arrangement, in which a cam 10b, 100b drives an elongated piston 8 leading to a pumping chamber 7a. However, it will be appreciated that alternative pumping arrangements could be used. For example, a drive element comprising a rocker arm type pump arm can be used. In such a case, the actuators of the rocker arrangement could be held by the frame in a manner similar to the arrangement of the cam illustrated in the

10 Figure 1.

The aforementioned embodiments of the present invention have been described with respect to a single pump 1 having a single pump head 7 and a single cam arrangement 10. However, it will be appreciated that the principles of the present invention apply equally to pumping systems that include multiple pumping heads, with one or more transmission shafts.

Other variations and modifications will be apparent to one skilled in the art without departing from the scope of the invention, as defined in the appended claims. For example, it will be appreciated that although the described embodiments relate to fuel pumps that are lubricated with fuel, the invention is equally applicable to oil lubricated pumps.

Claims (11)

1. A fuel pump (1) for pressurizing fuel in a high pressure fuel injection system, the fuel pump (1) comprising: a pump head (7) having a pumping chamber (7a) that is arranged to receive the fuel to be pressurized; a pumping element (8) arranged to respond in reciprocating motion to the movement of an actuating element (10), the pumping element (8) defining, in part, the pumping chamber (7a) such that, in use When the pumping element (8) moves alternately, a force, transferred from the actuating element (10), is applied to the fuel inside the pumping chamber. 10 pumping (7a) to pressurize the fuel; a frame (12) arranged to hold the drive element (10) and the pump head (7); Y a cover (3) defining an internal volume (5) to contain fluid; wherein at least a part of the frame (12), at least a part of the drive element (10) and at least a part of the pumping element (8) are received in the cover (3). The fuel pump (1) according to claim 1, wherein the frame (12) is arranged to keep the pump head (7) and the drive element (10) in fixed positions relative to each other to support the transfer of force from the drive element (10) to the pump head (7). 3. The fuel pump (1) according to claim 1 or claim 2, wherein the frame (12) is it builds from a material that has greater strength than a material from which the roof (3) is constructed.

Four.

The fuel pump (1) according to any preceding claim, wherein the frame (12) is formed in a single piece.

5.

The fuel pump (1) according to claim 4, wherein the frame (12) is formed in a single piece by means of an extrusion process.

The fuel pump (1) according to any preceding claim, wherein the cover (3) is formed of a plastic-based material.

7.

The fuel pump (1) according to any preceding claim, wherein the frame (12) is arranged to mount the fuel pump (1) to an engine component.

8.

The fuel pump (1) according to claim 7, further comprising:

30 a mounting arrangement (14) for connecting the frame (12) of the fuel pump (1) to an engine component. 9. The fuel pump (1) according to claim 8, wherein the cover (3, 12) and the mounting arrangement (14) each comprise a complementary interference feature (3m, 14k) arranged to prevent the rotation of the mounting arrangement (14) with respect to the cover (3, 12). The fuel pump (1) according to claim 9, wherein one of the complementary interference characteristics comprises a projection (3m) and the other complementary interference characteristic comprises a recess (14k). 11. The fuel pump (1) according to any preceding claim, wherein the cover (3) comprises one or more integrated components (2, 6) including one or more return devices of 40 leakage (6) to facilitate fluid recirculation, and a fuel inlet (2) to supply fuel to the fuel pump (1). 12. The fuel pump (1) according to any preceding claim, wherein the drive element (10) is formed from a multitude of parts including a shaft part (10a) and a cam part (10b) . 13. The fuel pump (1) according to claim 12, wherein the cam part (10b) is constructed from a material of greater strength than the shaft part (10a). 14. The fuel pump (1) according to any preceding claim, wherein the pump head (7) is received inside the cover (3). eleven 15. The fuel pump (1) according to any preceding claim, wherein the frame comprises at least one bearing (12c, 12d, 13a, 13b) arranged to hold the drive element (10) for rotational movement with respect to the bearing (12c, 12d, 13a, 13b). 12