Claims:We Claim:

1. A spring retainer assembly (127B) for a speed governor (100) for an internal combustion engine, said spring retainer assembly (127B) comprising :
- a tension lever (114) a having a grove
- a pressure spindle (500) inserted in said grove on said tension lever (114)
- compression spring (128) surrounding said pressure spindle (500), to enable movement of said pressure spindle (500) in said grove
- a shim (502) at one end of pressure spindle (500) to adjust the pretension of said compression spring (128)
- a closing plug (506) to close said grove

2. A spring retainer assembly (127B) according to claim 1 wherein said tension lever (114) is coupled to a link connecting to control rack (106)

3. A spring retainer assembly (127B) according to claim 1 wherein thickness of said shim (502) determines the pretension of compression spring (128)

4. A spring retainer assembly (127B) according to claim 1 wherein shim (502) of different thickness is used to vary the pretension of compression spring (128)
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[001] This invention relates to the field of fuel pumps to supply fuel to an internal combustion engine.

Background of the invention

[002] Fuel pumps to supply fuel to an internal combustion engine are known in prior arts. A typical fuel injection system comprises a fuel tank, a high pressure fuel pump, a set of injectors, a timing device etc. The pumps may be of different types like inline pump, radial piston pump etc. The fuel injection system may be fully mechanical system or a combination of an electronic and mechanical components.

In the fully mechanical system, the speed of the engine is regulated by a mechanical governor. The mechanical governors control the fuel injection quantity based on the engine RPM and based on the settings. The mechanical governors are typically built into the pump and use centrifugal fly weights, springs and lever assembly to regulate the fuel supply to the engine.

[003] The prior art DE 4407703 A1 discloses a mechanical governor for an internal combustion engine. The governor has on an outer periphery of a governor shaft, a spring presser is provided between a push ring and a spring bearing free to move. This spring presser is arranged at a specified position so that the push ring 23 knocks against it when the number of rotation of an internal combustion engine reaches a specified number of rotation. The spring presser is blocked by a snap ring from moving from the specified position to the side of the push ring. An interval between a small diametrical part of the spring presser and a small diametrical part of the spring bearing positioned at the specified positions is made roughly equal to natural length of a spring in a governor spring.

Brief description of the accompanying drawing

[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[005] FIG. 1 illustrates a mechanical governor
FIG. 2 and FIG. 3 illustrates a spring retainer assembly as in prior arts
FIG. 4 and FIG. 5 illustrates a spring retainer assembly according to the invention

Detailed description of the embodiments

FIG. 1 illustrates a mechanical speed governor 100 to regulate the fuel quantity to be delivered to an engine which is not shown, based on the operating conditions of the vehicle and the settings. The mechanical speed governor 100 is referred as speed governor or just as governor, in this document.

The mechanical speed governor 100 comprises a Swiveling lever 102, Rigid link 104, Control rack 106, Fuel-injection pump camshaft 108, Governor housing 110, Starting spring 112, Tensioning lever 114, Governor cover 116, Control lever 118, Stop setting/low-idle stop 120, Governor spring 122, Auxiliary idle-speed spring 124, Guide lever 126, Spring retainer assembly 127, Torque-control spring 128, Multiplier gear 130, Guide bushing 132, sliding bolt 134, Full-load stop 136.

The governor shown in fig. 1 typically forms part of an inline pump and typically disposed in same housing. The inline pump typically has a set of individual plungers pressurizing the fuel in their pump chambers. The plungers are driven by the cam shaft of the pump which in turn is driven by the engine. The plungers pressurize the fuel and the pressurized fuel is delivered to injectors and the injectors inject the fuel into cylinders of an engine. The plungers have a helix groove and when the helix groove comes in fluid communication with the control port, the pressure drops in the pump chamber and delivery of fuel to injectors is reduced. By rotating the plunger, the timing at which the helix groove comes in fluid communication with the control port, is varied. Thus the quantity of fuel which is pressurized and delivered to the injectors, is varied by rotating the plunger. The plunger is coupled to a rack through a gear mechanism. The rack moves to and fro. The linear motion of rack is converted into rotary motion by the gear and the gear enables the plunger to rotate clockwise or anti-clockwise whenever the rack moves. The rack is coupled to the control lever through spring and the lever is coupled to the accelerator pedal. Whenever the accelerator pedal position changes, the lever changes its position thereby moving the rack. The movement of the rack rotates the plunger thereby varying the quantity of fuel delivered to the injectors.

The functioning of inline pump, helix groove, rotation of the plunger etc. are already known and hence not explained in detail.

Basic function of the governor is to control the delivery fuel quantity through control rack 106 movement based on the pump speed input from camshaft 108 and load input from control lever 118. With changing speed of the camshaft 108, flyweights either move outwards or inwards and effectively transmitting the linear movement to sliding bolt 134 and Guide lever 126. Accelerating pedal of the vehicle is connected to control lever 118 which is connected to swiveling lever 102. The movement of the accelerating pedal is transmitted to control lever 118 and in turn to swiveling lever 102. This movement extends governor spring 122 and pulls the tensioning lever 114 which pushes the sliding bolt 134 and hence moves guide lever 126 against sliding bolt direction.

At maximum load condition and maximum speed condition, the fuel delivery is high. But with this delivery pattern of the pump, engine produces higher power which is beyond the limits of engine capability. To avoid this, fuel delivery has to be reduced during these conditions and Torque-control spring 128 serves this purpose. Torque-control spring 128 is pre-tensioned such that the sliding bolt can overcome the spring-force (adoption spring + Governor Spring) only at condition of maximum speed and maximum load. Sliding bolt moves the Pressure-spindle in the adaption overcoming the pre-tension and hence moves guide lever 126 away and this movement is transferred to control rack 106 through rigid link 104 and thus reducing the fuel delivery as per requirement.

Fig 2 and fig. 3 show an exploded view of spring retainer assembly 127 used in the prior arts, which is shown as 127A. Same parts shown in different figures have same part numbers. In the prior art shown in fig. 2 and fig. 3, spring retainer assembly 127A is assembled onto the tension lever 114 and spring retainer assembly 127A is further a sub-assembly of 6 components. This arrangement is used to keep the compression spring 128 under desired pre-load. Spring & pre-load is varied by adjusting an oval nut 200 to achieve the required fuel delivery characteristics.

In the proposed invention number of components are reduced but still achieves the desired hydraulic trend by using shims for adjusting pre-load of the spring.

Fig. 4 and fig. 5 show an exploded view of spring retainer assembly 127 according to one embodiment of the invention. The spring retainer assembly proposed according to the invention is referred as 127B. The spring retainer assembly 127B shown in fig. 3, according to the invention, is replaced by assembly of Pressure spindle 500, compression spring 128, Shim 502 and closing plug 506 directly onto the tension lever 114. No design change is made to the tension lever 114. Closing plug 506 is designed to hold shims 502 of different thicknesses with which the desired preload on compression spring 128 can be set to achieve the required fuel delivery characteristics.

The invention has advantage of simple assembly by eliminating 4 components of the spring retainer assembly 127A used in prior arts. It has simple design to achieve the required functionality. The invention eliminates adaption capsule malfunctioning as the lever is already sub-assembled and sealed. The invention provides easier method of setting the pre-tension on compression spring 128 by using shims of different thickness.