GB2536950A

GB2536950A - Coupling assembly for coupling a camshaft-driven unit pump to a camshaft

Info

Publication number: GB2536950A
Application number: GB1505710.2A
Authority: GB
Inventors: Palma Andrea; Sperlinga Antonino
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2015-04-01
Filing date: 2015-04-01
Publication date: 2016-10-05
Also published as: GB201505710D0

Abstract

A coupling assembly for coupling a camshaft-driven unit pump to a camshaft comprising a first gear 8 rotationally fixedly connected to a camshaft 3 and a second gear 9 configured to mesh with the first gear and comprising an integrated conversion mechanism 10 operatively coupled to a piston 5 of a unit pump 2 to convert rotation of the second gear into a stroke movement of the piston. The integrated conversion mechanism preferably comprises a disk 16 with lobes 17 circumferentially protruding therefrom. The disk and the second gear may be spaced apart from each other. Preferably the disk is operatively coupled to a follower 13 of the piston. The unit pump is preferably a fuel injection pump. Also claimed is a vehicle comprising the assembly. The invention allows the pump to be mounted in a number of different locations with respect to an engine, as opposed to conventional camshaft lobe driven pumps which are restricted to being directly coupled to the camshaft.

Description

Coupling assembly for coupling a camshaft-driven unit pump to a camshaft The present invention relates to a coupling assembly for coupling a camshaft-driven unit pump to a camshaft and to a vehicle, which comprises such a coupling assembly.

In combustion engines, there are camshaft-driven unit pumps driven by rotation of the engine's camshaft.

DE 195 15 191 Al discloses a coupling assembly for coupling a camshaft-driven unit pump to a camshaft, which comprises a pump lobe rotationally fixedly connected to the camshaft, wherein an end of a plunger piston of the unit pump is in contact with the pump lobe to convert rotation of the camshaft into a stroke movement of the plunger piston.

It is an object of an embodiment of the present invention to provide a coupling assembly for coupling a camshaft-driven unit pump to a camshaft with which it is possible to install the unit pump within a vehicle's engine compartment with more flexibility compatible with functionality constraints of the unit pump.

According to an embodiment of the invention, a coupling assembly for coupling a camshaft-driven unit pump to a camshaft is provided, which comprises a first gear rotationally fixedly connected to the camshaft and a second gear configured to mesh with the first gear. The second gear comprises an integrated conversion mechanism operatively coupled to a plunger piston of the unit pump to convert rotation of the second gear into a stroke move-ment of the plunger piston.

In known engines, the possible installation positions for a unit pump are limited, since the pump lobe, which is rotationally fixedly connected to the camshaft, directly acts on the cam 3 5 follower of the unit pump. By using two gears, wherein a first gear is rotationally fixedly con-nected to the camshaft, also called a fixed gear, and a second gear, which can for example be mounted to a cylinder head of the engine, is configured to mesh with the first gear, and wherein the second gear comprises an integrated conversion mechanism operatively coupled to a plunger piston of the unit pump to convert rotation of the second gear into a stroke movement of the plunger piston, the motion axis of the plunger piston does no longer have to be directly coupled to the rotation axis of the camshaft since movement can be transmitted to the motion axis of the plunger piston via the first and second gear and, therefore, the unit pump can be installed more flexibly within the engine compartment. Thus, a coupling assembly for coupling a camshaft-driven unit pump to a camshaft is provided with which it is possible to install the unit pump within a vehicle's engine compartment with more flexibility and compatible with functionality constraints of the unit pump. Further, it is possible to assemble the unit pump, the camshaft and the coupling assembly together to form a single unit, prior to installing the single unit in the engine compartment. Thereby, the installation of the unit pump within the engine compartment can be further simplified.

The integrated conversion mechanism can comprise a disk with lobes circumferentially protruding from said disk. Disk and lobes can be one piece. This integrated conversion mechanism can be operatively coupled to a follower attached to an end of the plunger piston to convert rotation of the second gear into a stroke movement of the plunger piston. The disk with lobes which can driven by an appropriate drive shaft.

Since pump lobes, in particular pump lobes used for driving a unit pump for a 3-cylinder engine, usually have a tri-lobe profile in order to convert rotation of a camshaft into a stroke movement of a plunger piston, the plunger piston of the unit pump does not have to be adapted to the coupling assembly and, therefore, no major and costly modifications of the plunger piston are required in order to synchronize the rotation of the camshaft and the oper-ation of the unit pump_ Since the number of lobes on the conversion mechanism should correspond to the number of cylinders in the engine in order to ensure an even flow of liquid to an engine, such a con- 3 0 version mechanism with a tri-lobe form is preferably used with unit pumps for 3-cylinder en-gines. Therefore, if the unit pump is used for an engine with more than three cylinders, the conversion mechanism should be adapted to have for example a lobe contour wherein the number of lobes corresponds to the number of cylinders of the engine to ensure an even flow of liquid to the engine. So if there are four or six cylinders, the number of lobes should be 4 3 5 or 6 respectively.

In an embodiment, the coupling assembly has a disk, which is securely fastened to the second gear. Fastening can be done by screws or bolts or the like. When being used, the disk securely fastened to the second gear acts as a driven wheel and at the same time directly converts rotation into a stroke movement of the plunger. In the alternative, the disk is one piece with the second gear. In both cases the position of the associated drive shaft for sec-ond gear and disk provides flexibility in positioning the unit pump.

In other embodiments the coupling assembly has a disk and the second gear with a joint rotation axis and are spaced apart from each other. In other words, they are mounted at a dis-tance on the same driveshaft. This gives even more flexibility as to the position of the unit pump.

Further, the first gear can have a first diameter and the second gear can have a second diameter, wherein the second diameter is firmly specified and the first diameter is selected ac-cording to a desired frequency of operation of the unit pump. For example, if a value larger than a value of the second diameter is selected for the first diameter, the frequency of operation of the unit pump can be increased, compared to embodiments wherein the first diameter and the second diameter have equal values. On the other hand, if a value less than a value of the second diameter is selected for the first diameter, the frequency of operation of the unit pump can be decreased, compared to embodiments wherein the first diameter and the second diameter have equal values. Further, it is also possible that the first gear has a firmly specified diameter and that the diameter of the second gear is selected according to the desired frequency of operation of the unit pump.

Also the first gear can have a first number of teeth and the second gear can have a second number of teeth, wherein the first number of teeth is firmly specified and the second number of teeth is selected according to a desired frequency of operation of the unit pump. For example, if the second number of teeth is selected to be larger than the first number of teeth, a rotational velocity of the second gear and, therefore, the frequency of operation of the unit pump can be increased, compared to embodiments wherein the first number of teeth is equal to the second number of teeth. On the other hand, if the second number of teeth is selected to be less than the first number of teeth, a rotational velocity of the second gear and, therefore, the frequency of operation of the unit pump can be decreased, compared to embodiments wherein the first number of teeth is equal to the second number of teeth.

Thus, the coupling assembly can be adapted in a simple way to match a desired frequency of operation of the unit pump without having to adapt the camshaft and/or the unit pump in a costly and exacting way. Further, a surface of the integrated conversion mechanism which is operatively coupled to the plunger piston to convert rotation of the second gear into a stroke movement of the plunger piston can be slightly modified, in order to increase or decrease the frequency of operation of the unit pump, too.

According to another embodiment of the invention, a vehicle is provided, which comprises an engine, a camshaft-driven unit pump for supplying a fluid to the engine, at least one cam-shaft for driving the camshaft-driven unit pump and a coupling assembly for connecting the camshaft-driven unit pump to the at least one camshaft as described above.

In the usual vehicle engines, the possible installation positions for a unit pump are limited, since an end of the plunger piston has to be in contact with a pump lobe rotationally fixedly connected to the camshaft, wherein a motion axis of the plunger piston is directly coupled to a rotation axis of the camshaft, and due to the presence of fixing points of other engine components, for example a gearbox, in this area. By using a coupling assembly with two gears, wherein a first gear is rotationally fixedly connected to the camshaft and a second, second gear, which can for example be mounted to a cylinder head of the engine, is configured to engage with the first gear, and wherein the second gear comprises an integrated conversion mechanism operatively coupled to a plunger piston of the unit pump to convert rotation of the second gear into a stroke movement of the plunger piston, the motion axis of the plunger piston does no longer have to be directly coupled to the rotation axis of the camshaft since movement can be transmitted to the motion axis of the plunger piston via the first and sec- and gear and, therefore, the unit pump can be installed more flexible within the vehicle's en-gine compartment Thus, with such a coupling assembly it is possible to install the unit pump in the vehicle's engine compartment in every position compatible with functionality constraints of the unit pump. Further, since hereby no modifications of the unit pump, the camshaft or other engine components are required, the coupling assembly is not restricted to specific types of camshaft-driven unit types or engines. Furthermore, it is possible to assem-ble the unit pump, the camshaft and the coupling assembly together to form a single unit, prior to coupling the single unit to the engine and to installing the single unit in the vehicle. Thereby, the installation of the unit pump in the vehicle can be further simplified.

Therein, the unit pump can be a fuel injection pump. In most of the usual engines, for example internal combustion engines, a fuel pump is used to supply fuel to the cylinders of the engine, which is mechanically driven by the rotational motion of a camshaft. That the unit pump is a fuel injector pump should merely be understood as an example, however, and the unit pump can be any other pump installed in the vehicle, coupled to an engine and driven by a camshaft, too.

Embodiments of the invention will now be described with reference to the drawing.

Figure 1 illustrates a coupling assembly for coupling a camshaft-driven unit pump to a camshaft according to embodiments of the invention.

Figure 1 illustrates a coupling assembly 1 for coupling a camshaft-driven unit pump 2 to a camshaft 3 according to embodiments of the invention.

The unit pump 2 shown in figure 1 is a fuel injection pump 4 mounted on an engine, which comprises a movable plunger piston 5 and with which fuel is pumped from a reservoir in an unillustrated combustion chamber of the engine, in particular an intemal combustion engine, for example a gasoline engine. That the unit pump is a fuel injector pump should merely be 2 0 understood as an example, however, and the unit pump can be any other pump coupled to an engine and driven by a camshaft, too.

The plunger piston 5 defines a working chamber 6, whose volume is changed periodically by the movement of the plunger piston 5. Therein, the fuel can be introduced from the reservoir into the working chamber 6 via a supply line. From the working chamber 6, the fuel flows at a high pressure into an injector, which controls the injection of fuel in the combustion chamber.

Figure 1 also illustrates a camshaft 3, wherein the plunger piston 5 is moved by rotational movement of the camshaft 3. In particular, the rotational movement of the camshaft 3 is transferred to the plunger piston 5, which is guided in an axial direction in a housing 7 of the unit pump 2, and is converted into a reciprocal linear motion of the plunger piston 5 and, thus, in a stroke movement of the plunger piston 5.

According to the embodiment shown in figure 1, the coupling assembly 1 for coupling the 3 5 camshaft-driven unit pump 2 to the camshaft 3 comprises a first gear 8 rotationally fixedly connected to the camshaft 3 and an second gear 9 mounted on a drive shaft 14 to a cylinder head 15 of the engine and configured to mesh with the first gear 8, wherein the second gear 9 comprises an integrated conversion mechanism 10 operatively coupled to the plunger piston 5 to convert rotation of the second gear 9 into a stroke movement of the plunger piston 5. Therein, the rotation of the second gear 9 is symbolized by the arrow indicated with refer-ence sign 11 and the stroke movement of the plunger piston 5 is symbolized by the arrow indicated with reference numeral 12.

In particular, since the first gear 8 is rotationally fixedly connected to the camshaft, by driving the camshaft 3 during operation of the engine, the first gear 8 is rotated too. Since the sec-and gear 9 is configured to mesh with the first gear 8, such rotation of the first gear 8 effects corresponding but reverse rotation of second gear 9 and, therefore, of the conversion mechanism 10 integrated into the second gear 9. More in detail, conversion mechanism 10 comprises a disk 16 having 3 lobes 17, 17' and 17" circumferentially protruding from a disk 16. Disk 16 and its lobes 17, 17' and 17" are one piece, so lobes 17, IT and 17" can be said to be integral to disk 16. Disk 16 and second gear 14 are both mounted on the same driveshaft 14 but at different axial positions. In Figure 1 disk 16 with its integral lobes 17, 17' and 17" is one piece with the second gear 9 and is facing the viewer, whereas second gear 9 being positioned axially behind disk 16.

As can be further seen in figure 1, a follower 13 is attached to an end of the plunger piston 5.

Follower 13 rides on the circumferential surface of disk 16 with its integral lobes 17, 17' and 17", thereby guiding the plunger piston 5 in an axial direction and converting the rotation of the second gear 9 into stroke movement of the plunger piston 5.

Depending on space requirements when mounting the parts, disk 16 with its integral lobes 17, 17' and 17" can be separated from each other, while still being mounted on the same driveshaft 14. This can be achieved by making sure that they are both fixedly mounted to the driveshaft 14, such that rotation of driven second gear 9 automatically amounts to a rotation of disk 16 with the same sense of rotation. In this way the position Thus, with the shown coupling assembly 1, the motion axis of the plunger piston 5 does no longer have to be directly coupled to the rotation axis of the camshaft 3 and, therefore, the unit pump 2 can be installed more flexible within the engine compartment and, therefore, a coupling assembly 1 for coupling the camshaft-driven unit pump 2 to the camshaft 3 is pro- 3 5 vided with which it is possible to install the unit pump 2 in a vehicle's engine compartment in every position compatible with functionality constraints of the unit pump 2.

According to the embodiment shown in figure 1, the integrated conversion mechanism 12 has a tri-lobe form, or in other words 3 lobes, in particular has a tri-lobe profile. Since pump lobes, in particular pump lobes used for driving a unit pump for a 3-cylinder engine, usually have a tri-lobe profile in order to convert rotation of a camshaft into a stroke movement of a plunger piston, the plunger piston 5 of the unit pump 2 does not have to be adapted to the coupling assembly and, therefore, no major and costly modifications of the plunger piston are required in order to synchronize the rotation of the camshaft 3 and the operation of the unit pump 2. However, since the number of lobes on the conversion mechanism should come-spond to the number of cylinders in the engine in order to ensure an even flow of liquid to an engine, such a conversion mechanism with a tri-lobe form is preferably used with unit pumps for 3-cylinder engines, and, if the unit pump is used for an engine with more or less than three cylinders, the conversion mechanism should be adapted to have for example a lobe contour wherein the number of lobes corresponds to the number of cylinders of the engines to ensure an even flow of liquid to the engine.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

List of reference signs 1 coupling assembly 2 camshaft-driven unit pump 3 camshaft 4 fluid injection pump plunger piston 6 working chamber 7 housing 8 first gear 9 second gear integrated conversion mechanism 15 11 rotation 12 stroke movement 13 follower 14 drive shaft cylinder head 1. 2. 3. 4. 2 0 5. 6. 7. 8.