OIL FLOW SYSTEM FOR A CLUTCH

FIELD OF THE INVENTION

[0001] The present invention relates generally to a transmission system of
an automotive vehicle and more particularly, but not exclusively, to a clutch of the transmission system.

BACKGROUND OF THE INVENTION

[0002] Conventionally, an automotive vehicle is provided with a transmission system which transmits the power generated by an internal combustion engine, in a controllable way, to a wheel of the vehicle. The transmission system has primarily two functions. Firstly, it disconnects the engine from the wheel to enable gearing to boost the engine's effective torque. Secondly, it also disconnects the engine from the wheel when the vehicle is stopped thus permitting the engine to run without driving the vehicle.

[0003] Generally the transmission system includes a clutch, a gearbox and a drive means. It is housed on an input shaft and an output shaft operatively connected with each other through the gearbox and deriving power from the crankshaft. The clutch is located at one end of the input shaft to momentarily disconnect the gearbox from the engine to ensure gradual shifting of gears. When the clutch is engaged, it transmits force from the engine and rotates the wheel. When the clutch is disengaged, the tranmission of rotational force is cut off and the wheel tends to stop. The gearbox comprises a set of interlocking gears with multiple gear ratios. A operator can switch between the gear ratios as the speed of the vehicle varies by operating a gear shift means manually. The drive means may be a chain, a belt or a propeller shaft.

[0004] One of the many types of clutches, differing from each other depending upon how the clutch is actuated, is included in the transmission system. For example, in a manual clutch, the clutch actuation is controlled by the vehicle operator. In a centrifugal clutch, the clutch actuation is controlled by the engine removing the need for manual control.

[0005] It is observed that in the transmission system having manual clutch, shifting between one gear ratio to another gear ratio is difficult and painful for the vehicle operator. In the particular context of a three wheeled automotive vehicle, the gear shifting is hard between first gear ratio to neutral gear ratio and also between the reverse to neutral gear ratio. The condition is further aggravated when the vehicle is stuck in heavy traffic prompting the vehicle operator to change gear ratios many times within a short span of time. Thus, the hard and painful changing of gears is bothersome for the vehicle operator.

SUMMARY OF THE INVENTION

[0006] The transmission system may either have a wet clutch or a dry clutch. In the dry clutch transmission system, the clutch plates are cooled by the incoming environmental air. In the wet clutch transmission system, the clutch plates are cooled by the lubricating oil of the engine. Further, manually operable clutch systems can be either wet or dry.

[0007] The oil is supplied to the wet clutch through either splash mode or spray mode or both. In the splash mode, the oil is scooped from an oil sump due to rotation of an input shaft and allowed to pass between the clutch plates. In the spray mode, the oil is forced through an input shaft nozzle by means of a lubrication channel and is directed to pass between the clutch plates due to centrifugal force. Conventionally, a four stroke internal combustion engine employs both splash mode and spray mode to supply oil to the clutch plates to ensure their longer life.

[0008] However, the dual mode oil supply system has many demerits in the event of disengagement of clutch before gear shifting. The transmission system having the manually operable wet clutch has hard gear shifting. Due to oil supply through the input shaft, the required effort for manual gear shifting increases. This is because even though the clutch plates do not contact with each other, the clutch drag torque increases as the supplied viscous oil acts as a fluid coupling member between the clutch plates. Consequently, the manual gear shifting becomes difficult leading to vehicle operator's discomfort. It is to be noted that the operator may have to do gear shifting many times in a day particularly during heavy traffic and extra effort leads to frequent operator fatigue and muscle pain. On the other hand, if the oil supply through the input shaft (spray mode) is permanently disabled, the clutch durability will be considerably reduced, leading to operator dissatisfaction due to frequent part replacement. The present invention tends to address the above mentioned problems.

[0009] It is therefore an object of the present invention to reduce the clutch drag torque during the clutch disengagement event to reduce the effort required by the vehicle operator during ensuing gear shifting.

[00010] It is another object of the present invention to provide a clutch release pin assembly which disables the lubrication oil flow during clutch disengagement event to easy, smooth and comfortable gear shifting.

[00011] The present invention thereofore discloses a clutch release pin assembly operatively connected with a wet clutch housed in a transmission system toward one end of an input shaft. It comprises of a clutch release pin, a preloaded compression spring and an oil sealing cap. The clutch release pin is movable relatively to the oil sealing cap. During a clutch disengagement event, the clutch release pin assembly moves axially to cover the one end of the input shaft from which the lubrication oil is sprayed to the clutch plates. Thus, the one end of the input shaft is sealed and the flow of lubrication oil to the clutch plates is prevented. By 'blocking' the oil flow to clutch plates, the clutch drag torque is reduced thereby enabling smooth and comfortable shifitng of the gears.

[00012] The foregoing objectives and summary is provided to introduce a selection of concepts in a simplified form, and is not limiting. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the subject matter and the claims should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[00013] The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:

[00014] FIG. 1(a) shows a sectional view of a clutch release pin assembly
in a transmission system of an internal combustion engine according to an embodiment of the present invention.

[00015] FIG. 1(b) shows an exploded sectional view of the clutch release pin assembly of FIG. 1(a).

[00016] FIG. 2 shows an exploded perspective view of the clutch release pin assembly.

[00017] FIG. 3 shows a sectional view of the clutch release pin assembly during a clutch engagement event.

[00018] FIG. 4 shows a sectional view of the clutch release pin assembly during a clutch disengagement event.

[00019] FIG. 5 shows a sectional view of a clutch release pin in the transmission system according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

[00020] The present invention discloses a clutch release pin assembly which reduces the clutch drag torque. During the clutch disengagement event, it regulates the oil flow to the clutch plates through the spray mode. More particularly, the oil flow is disabled during the clutch disengagement event. The oil flow is blocked only momentarily at the time of disengaging the clutch to undertake a gear shifting event and reduces the clutch drag torque during the clutch disengagement event. The oil flow is not disabled during normal driving in any gear when the clutch is engaged. An embodiment is now explained in detail. Various other features of the present subject matter here will be discernible from the following further description thereof, set out hereunder.

[00021] FIG. 1(a) shows a sectional view of a clutch release pin assembly 40 in a transmission system of an internal combustion engine according to an embodiment of the present invention. The clutch release pin assembly 40 comprises of a clutch release pin 12, an oil sealing cap 18 and a preloaded compression spring 16 accommodated between the clutch release pin 12 and the oil sealing cap 18. In an embodiment, the oil sealing cap 18 and the clutch release pin 12 are movably connected to each other.

[00022] FIG. 1(b) describes the clutch release pin assembly in greater detail. In an embodiment, the clutch release pin 12 has a T-shaped cross section and comprises of a base portion 14. A supporting projection 15 emanates from one side of the base portion 14 and a stem portion 20 emanates from other side of the base portion 14. Thus, the supporting projection 15 and the stem portion 20 protrude from the base portion in opposite directions.

[00023] In an embodiment, the supporting projection 15 protrudes toward a one end of an input shaft 11. A clutch 10 (FIG. 3) is supported on the one end of the input shaft 11 to disengage or engage a wheel of the vehicle with the engine. In an embodiment, the supporting projection 15 has a cylindrical cross section and comprises of a hollow space 22 formed between the walls of the supporting projection 15.

[00024] As shown in FIG. 2, the oil sealing cap 18 has a hemispherical cross section and receives a portion of the supporting projection 15. In an embodiment, the oil sealing cap has an approximately U-shaped cross section.

[00025] The oil sealing cap 18 is movably connected to the clutch release pin 12 through the supporting projection 15. The supporting projection 15 of the clutch release pin 12 moves relatively to the oil sealing cap 18 during a clutch disengagement event. For this purpose, the oil sealing cap 18 comprises of at least one pin groove 19 and the supporting projection 15 also comprises of at least one pin receiving groove 15a. Through the pin groove 19 and the pin receiving groove 15a, the oil sealing cap 18 is supported on, and connected with, the supporting projection 15.

[00026] The at least one pin groove 19 is located on a lateral surface of the oil sealing cap 18. In a preferred embodiment, the oil sealing cap 18 comprises of two pin grooves 19,19 opposite to each other on either side of the long axis of the oil sealing cap 18. The at least one pin receiving groove 15a is provided along the axial surface of the supporting projection 15. In a preferred embodiment, the supporting projection 15 also comprises of two pin receiving grooves 15a, 15a.

[00027] Each pin groove 19 and each pin receiving groove 15a is configured to receive a guiding pin 17. During assembly, the guiding pin 17 passes through the at least one pin groove 19 and the at least one pin receiving groove 15a coaxially to hold the supporting projection 15 against the oil sealing cap 18. Thus, the guiding pin 17 holds the oil sealing cap 18 and supporting projection 15 together.

[00028] Further, in an embodiment, the compression spring 16 is a helical spring. It is preloaded by the oil sealing cap 18 during assembly. When assembled, a portion of the compression spring 16 is ensconced in the hollow space 22 of the supporting projection 15. The compression spring 16 is invisible from outside.

[00029] The clutch release pin 12 is assembled along with the compression spring 16, the oil sealing cap 18 and guiding pins 17 to form and function as a single unit. During assembly, when a portion of the supporting projection 15 of the clutch release pin 12 is received in the oil sealing cap 18, each guiding pin 17 passes through the corresponding pin groove 19 and the pin receiving groove 15a to hold the projection 15 against the oil sealing cap 18. According to an aspect, each pin receiving groove 15a of the supporting projection 15 has a bigger diameter than the pin groove 19 of the oil sealing cap 18. This ensures that the supporting projection 15 is able to move relatively with respect to the oil sealing cap 18.

[00030] The working of the clutch release pin assembly is now explained. FIG. 3 shows a sectional view of the clutch release pin assembly 40 during an event of clutch engagement. With the help of base portion 14, the clutch release pin assembly 40 sits over the clutch 10. The clutch 10 has a plurality of clutch plates 8. The stem portion 20 is axially outside while the oil sealing cap 18 and supporting projection 15 are received within the axial gap of a clutch bearing 21. The clutch release pin assembly 40 covers one end of the input shaft 11 and the clutch plates 8 receive lubrication oil for cooling from a nozzle 13 through the spray mode. The input shaft 11 is operatively connected to a crankshaft of the engine. The input shaft may also be referred to as counter shaft. It is a substantially hollow shaft with an oil channel 9 running along the long axis of the input shaft 11. The oil sealing cap 18 maintains a clearance with the one end of the input shaft 11 as the base portion 14 of the clutch release pin 12 is firmly seated on the clutch bearing 21. Thus, when the clutch 10 is engaged as shown, the oil is continuously supplied to the clutch plates 8 through the nozzle 13 in the oil channel 9 and the oil escapes to the clutch plates 8 as shown by the arrows. However, oil supply through the splash mode continues.

[00031] FIG. 4 shows a sectional view of the clutch release pin assembly 40 during a clutch disengagement event. To undergo gear shifting, the operator of the vehicle applies manual force on a clutch lever which is mechanically transferred to the stem portion 20 of the clutch release pin 12 which releases the pressure on the clutch plates 8 resulting in clutch disengagement. In response, the oil sealing cap 18 moves axially towards the one end of the input shaft 11 making initial contact with the one end of the input shaft 11 and there is no space for further axial movement of the oil sealing cap 18. The oil sealing cap 18 seals the one end of the input shaft 11 and prevents the flow of oil to the clutch plates 8 via the spray mode during the clutch disengagement event. The pin receiving groove 15a allows further movement of the supporting projection 15 against the oil sealing cap 18 after it makes initial contact with the one end of input shaft 11. This is possible because the pin receiving groove 15a of the projection 15 is bigger than the pin groove 19 of the oil sealing cap 18. If the pin receiving groove 15a were not bigger than the pin groove 19, the clutch release pin 12 will not be able to transfer the total displacement required to completely disengage the clutch plates 8 as there is no space for further axial movement of the oil sealing cap 18. By restricting the oil supply to the clutch plates 8 through the nozzle 13 of the input shaft 11, "the clutch drag torque is reduced thereby enabling smooth and comfortable shifting of the gears unlike the prior art shown in FIG. 5 where there is no mechanism to stop the oil flow through the spray mode to the clutch plates.

[00032] The present invention has several advantages along with those described above. The clutch release pin assembly disables the oil flow during the clutch disengagement event at the time of gear shifting leading to reduction of clutch drag torque. Hence, the effort required to shift the gears reduces thereby leading to easy, smooth and comfortable gear shifting. The smooth gear shifting particularly from first to neutral gear, or reverse to neutral gear is useful during heavy traffic or long travel. The durability of clutch plates will not be compromised because the oil flow to the clutch plates through the spray mode is only momentarily restricted during the duration of the clutch disengagement and subsequent shifting of gears.

[00033] It is to be noted that present subject matter is usable in any automotive vehicle including a two wheeled or a three wheeled vehicle. Further, any transmission system may comprise of a clutch release pin assembly as
1 explained above. Further, the clutch release pin assembly may be made of any material including a plastic resin, metal or metal alloy.

[00034] The present subject matter is thus described. The description is not intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above description. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore the forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.

We claim:

1. A clutch release pin assembly (40) for regulating the oil flow to a wet
clutch (10) comprising: a clutch release pin (12);
an oil sealing cap (18); a preloaded compression spring (16) accommodated between the clutch release pin (12) and the oil sealing cap (18);
wherein during a clutch disengagement event, the clutch release pin assembly (40) moves axially to cover an end of the input shaft (11) facing the wet clutch (10) and prevents the flow of oil toward a plurality of clutch plates (8).

The clutch release pin assembly (40) as claimed in claim 1, wherein the clutch release pin (12) further comprises of a base portion (14) wherein a supporting projection (15) emanates from one side of the base portion (14) and a stem portion (20) emanates from other side of the base portion.

The clutch release pin assembly (40) as claimed in claim 2, wherein a portion of the compression spring (16) is ensconced in a hollow space (22) of the supporting projection (15).

The clutch release pin assembly (40) as claimed in claim 1, wherein the oil sealing cap (18) has a hemispherical cross section and receives a portion of the supporting projection (15).

The clutch release pin assembly (40) as claimed in claim 1, wherein the oil sealing cap (18) comprises of at least one pin groove (19) and the supporting projection (15) comprises of at least one pin receiving groove (15a).

The clutch release pin assembly (40) as claimed in claim 5, wherein during assembly a guiding pin (17) passes through the at least one pin groove (19) and the at least one pin receiving groove (15a) coaxially to hold the oil sealing cap (18) against the supporting projection (15).

The clutch release pin assembly (40) as claimed in claim 5, wherein the diameter of the at least one pin receiving groove (15a) is bigger than the diameter of the at least one pin groove (15).

The clutch release pin assembly (40) as claimed in claim 1 or claim 7, the supporting projection (15) of the clutch release pin (12) moves relatively to the oil sealing cap (18) during a clutch disengagement event.

A transmission system comprising a clutch release pin assembly (40) as claimed in any of the previous claims.

An automotive vehicle comprising the transmission system as claimed in claim 9.