WO2009070267A1

WO2009070267A1 - Gearbox having synchronized clutch mechanisms

Info

Publication number: WO2009070267A1
Application number: PCT/US2008/013078
Authority: WO
Inventors: Kevin J. Knox
Original assignee: Caterpillar Inc.
Priority date: 2007-11-27
Filing date: 2008-11-24
Publication date: 2009-06-04

Abstract

A gearbox (1) having at least two gears is disclosed. The gearbox may include a first gearshaft (3), a second gearshaft (4) selectively engagable with the first gearshaft via the at least two gears, and at least one clutch mechanism (8, 9) located on the second gearshaft and configured to selectively engage the first gearshaft with the second gearshaft. The clutch mechanism may include a synchronizer (10), at least one clutch plate (12) attached to a gear (5b, 6b) on the second gearshaft, and a pressure plate (13) associated with the synchronizer. The clutch plate and the pressure plate may be configured to selectively engage one another, and the synchronizer may be configured to drivingly engage the second gearshaft so that the second gearshaft is driven by the first gearshaft.

Description

GEARBOX HAVING SYNCHRONIZED CLUTCH MECHANISMS

Technical Field The present disclosure is directed to a gearbox and, more particularly, a gearbox having synchronized clutch mechanisms.

Background

Construction and earthmoving equipment, as well as many other types of machines, are commonly used in a wide variety of applications. Generally, a machine is powered by an engine or motor and equipped with a gearbox having gear elements. One or more clutches associated with the gearbox connect input and output mechanisms within the power train of the machine. These clutches may be selectively engaged to transmit torque from the engine or motor to drive train elements of the machine. During operation of the gearbox, torque may be transmitted by either a first clutch or a second clutch. Each clutch includes clutch plates coupled to an input path configured to rotate and deliver torque from the engine by selectively engaging pressure plates coupled to an output path. Flow of a pressurized fluid, such as high pressure engine or transmission oil, controls the engagement of the clutch plates and pressure plates. As the first clutch is selected to be engaged and torque transmitted from the input path to the output path, pressure plates of the second clutch rotate with the output path, and the clutch plates of the second clutch rotate with the input path. Although unengaged and not transmitting torque, the pressure plates and clutch plates of the second clutch still rotate and experience frictional contact, generating heat and inefficiency of the gearbox. One method of improving the efficiency of a gearbox under such conditions is described in U.S. Patent No. 6,883,394 (the '394 patent) to Koenig et al., issued on 26 April 2005. The '394 patent describes a method for controlling the positioning of a plurality of synchronizers for a dual clutch transmission. The dual clutch transmission includes a dual coaxial clutch assembly having a first clutch mechanism and a second clutch mechanism, a first input shaft having a gear set, a second input shaft coaxial to the first and also having a gear set, a counter shaft having mating gears for the gears of the two input shafts, an output shaft, and a reverse counter shaft. The plurality of synchronizers is configured to selectively engage and disengage the various gear sets, and a plurality of shift actuators is adapted to move the synchronizers. The method controls the movement of the synchronizers and constantly monitors their positions, so as to prevent a drift condition where an errant synchronizer drifts into non-commanded contact with a gear set causing interference, damage, and inefficiency of the transmission.

Although the dual clutch transmission of the '394 patent may prevent undesirable frictional contact and inefficiency of a gearbox, it may have limitations. For example, an unengaged clutch mechanism of the dual coaxial clutch assembly may rotate and experience undesired frictional contact. The gearbox of the present disclosure is directed towards improvements in the existing technology.

Summary of the Disclosure

One aspect of the present disclosure is directed to a gearbox having at least two gears. The gearbox may include a first gearshaft, a second gearshaft selectively engagable with the first gearshaft via the at least two gears, and at least one clutch mechanism located on the second gearshaft and configured to selectively engage the first gearshaft with the second gearshaft. The clutch mechanism may include a synchronizer, at least one clutch plate attached to a gear on the second gearshaft, and a pressure plate associated with the synchronizer. The clutch plate and the pressure plate may be configured to selectively engage one another, and the synchronizer may be configured to drivingly engage the second gearshaft so that the second gearshaft is driven by the first gearshaft. Another aspect of the present disclosure is directed to a method for directing a clutch mechanism to engage a first gearshaft with second gearshaft of a gearbox. The clutch mechanism may include a synchronizer, a clutch plate, and a pressure plate located on the second gearshaft. The method includes engaging the clutch plate, attached to a gear drivingly coupled to an input gear fixed to the first gearshaft, with the pressure plate associated with the synchronizer and engaging the synchronizer with the second gearshaft so that the second gearshaft engages the first gearshaft.

Brief Description of the Drawings

Fig. 1 is a schematic cross-section of a gearbox according to an exemplary disclosed embodiment; and

Fig. 2 is a schematic, cross-sectional view of an exemplary clutch mechanism for the exemplary disclosed gearbox shown in Fig. 1.

Detailed Description

Fig. 1 diagrammatically illustrates an exemplary gearbox 1. Gearbox 1 may include a housing 2 and a plurality of co-operating shafts rotably supported therein. A first gearshaft 3, such as a power input shaft, may be connected to an external motive power source, such as a crankshaft of an internal combustion engine (not shown), and may be configured to engage a second gearshaft 4. A first input gear 5a and a second input gear 6a may be coupled to first gearshaft 3 and configured to rotate with first gearshaft 3. A first gear 5b may be located on second gearshaft 4 and configured to rotate with first input gear 5a, and a second gear 6b may be located on gearshaft 4 and configured to rotate with second input gear 6a. An output gear 7 may be rotably coupled to second gearshaft 4 and configured to drive second gearshaft 4. Although not shown, it will be understood that output gear 7 may also be engaged with a gear on a third gearshaft, such as a power output shaft, and transmit torque to the third gearshaft. A first clutch mechanism 8 may be associated with first gear 5b and located on second gearshaft 4, and a second clutch mechanism 9 may be associated with second gear 6b and also located on second gearshaft 4. Torque may be selectively transmitted through a first pathway or a second pathway. First clutch mechanism 8 may be associated with the first pathway and configured to selectively engage output gear 7, transferring torque from first gearshaft 3 to second gearshaft 4. When first clutch mechanism 8 is disengaged, first gearshaft 3 may not rotate second gearshaft 4, as there is no connection between first clutch mechanism 8 and output gear 7. As first clutch mechanism 8 may be engaged, second clutch mechanism 9 may be disengaged, so that torque may only be transmitted through first pathway by first clutch mechanism 8.

Similarly, second clutch mechanism 9 may be associated with the second pathway and configured to selectively engage output gear 7, transferring torque from first gearshaft 3 to second gearshaft 4. When second clutch mechanism 9 is disengaged, first gearshaft 3 may not rotate second gearshaft 4, as there is no connection between second clutch mechanism 9 and output gear 7. As second clutch mechanism 9 may be engaged, first clutch mechanism 8 may be disengaged, so that torque may only be transmitted through second pathway by second clutch mechanism 9.

First clutch mechanism 8 and second clutch mechanism 9 may be selectively detached from output gear 7. A synchronizer 10 of first clutch mechanism 8 and second clutch mechanism 9 may be configured to move axially along second gearshaft 4 and selectively engage and disengage with output gear 7. It should be appreciated that a variety of known types of synchronizers may be capable of engaging first clutch mechanism 8 or second clutch mechanism 9 to output gear 7 and that the particular type of synchronizer that may be employed is beyond the scope of this disclosure. Any type of synchronizer that may be axially movable by a yoke 1 1 or a like device may be employed. As shown in Fig. 1, synchronizer 10 may engage first clutch mechanism 8 to output gear 7 when moved from a neutral position to an engaged position (to the right in Fig. 1). Similarly, synchronizer 10 may engage second clutch mechanism 9 to output gear 7 when moved from a neutral position to an engaged position (to the left in Fig. 1).

In the exemplary disclosed embodiment shown in Fig. 2, second clutch mechanism 9 may include at least one clutch plate 12, at least one pressure plate 13, and synchronizer 10. Clutch plate 12 may be attached to a hub 18 coupled to second gear 6b and may rotate with second input gear 6a and first gearshaft 3 (shown in Fig. 1). Pressure plate 13 may be attached to a cylindrical member 14 coupled to synchronizer 10. Hydraulic fluid, such as, for example, high pressure engine or transmission oil, entering through a fluid passage 15 may engage clutch plate 12 and pressure plate 13, transferring torque from clutch plate 12 to pressure plate 13. Cylindrical member 14 and synchronizer 10 coupled to pressure plate 13 may subsequently rotate. Yoke 1 1 may be configured to axially move synchronizer 10 to the left to engage synchronizer 10 and second clutch mechanism 9 with output gear 7 and transmit torque from first gearshaft 3 to second gearshaft 4. As schematically and diagrammatically shown in the exemplary embodiment of Fig. 2, a collar 16 may engage in frictional contact with output gear 7, as to synchronize the rotational speeds of first gearshaft 3 and second gearshaft 4 before gear teeth 17 of synchronizer 10 and output gear 7 engage each other. Yoke 1 1 may also be configured to axially move synchronizer 10 to the right to disengage synchronizer 10 and second clutch mechanism 9 from output gear 7. Although not shown in Fig. 2, it will be understood that a similar clutch arrangement may be associated with first clutch mechanism 8. Industrial Applicability

The disclosed gearbox 1 may have applicability with machines powered by engines or motors and having drive train elements. For example, and as shown in Fig. 1 , gearbox 1 may serve to transmit torque from first gearshaft 3, such as a power input shaft, to a second gearshaft 4 and to drive train elements (not shown). Torque may be selectively transmitted through a first pathway by engaging a first clutch mechanism 8 or a second pathway by engaging a second clutch mechanism 9.

First gearshaft 3 may be rotably driven by an external motive power source, such as a crankshaft of an internal combustion engine (not shown). Torque generated by the rotation of first gearshaft 3 may be selectively transmitted to second gearshaft 4 through the engagement of first clutch mechanism 8 or second clutch mechanism 9 disposed on second gearshaft 4. Clutch plates 12 associated with first clutch mechanism 8 may be attached to first gear 5b and configured to rotate with first input gear 5a of first gearshaft 3, and clutch plates 12 associated with second clutch mechanism 9 may be attached to second gear 6b and configured to rotate with second input gear 6a of first gearshaft 3. As first clutch mechanism 8 or second clutch mechanism 9 may be selectively engaged, hydraulic fluid may enter a fluid passage 15 and engage clutch plates 12 with pressure plates 13. Torque may be transferred from the rotation of clutch plates 12 to pressure plates 13 which may rotate cylindrical member 14 of synchronizer 10 coupled to pressure plates 13. Synchronizer 10 may be axially moved by yoke 1 1 to engage output gear 7 fixed to second gearshaft 4. Once engaged with output gear 7, the rotation of synchronizer 10 and cylindrical member 14 may transfer torque to second gearshaft 4.

First clutch mechanism 8 and second clutch mechanism 9 may be selectively employed to engage second gearshaft 4 with first gearshaft 3. In particular, first clutch mechanism 8 and second clutch mechanism 9 may selectively engage output gear 7. Synchronizer 10 and yoke 1 1 may be configured engage one of first clutch mechanism 8 and second clutch mechanism 9 and disengage the other. For example and referring to Fig. 1, yoke 1 1 of first clutch mechanism 8 may be configured to axially move synchronizer 10 to the right to engage output gear 7, and yoke 1 1 of second clutch mechanism 9 may be configured to axially move synchronizer 10 to the left to engage output gear 7. To disengage first clutch mechanism 8, yoke 1 1 may be configured to axially move synchronizer 10 to a neutral position to the left. Similarly, to disengage second clutch mechanism 9, yoke 1 1 may be configured to axially move synchronizer 10 to a neutral position to the right. Assembling synchronizer 10 and yoke 1 1 to first clutch mechanism 8 and second clutch mechanism 9 may prevent undesired frictional contact between clutch plate 12 and pressure plate 13 and inefficiency of gearbox 1. Synchronizer 10 and yoke 1 1 may be configured to completely detach an unengaged first clutch mechanism 8 or second clutch mechanism 9 from output gear 7. Therefore, cylindrical member 14 and pressure plates 13 of the unengaged clutch mechanism remain stationary. Clutch plates 12 and pressure plates 13 of only the engaged clutch mechanism will come into contact and rotate.

It will be apparent to those skilled in the art that various modifications and variations can be made to the gearbox of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.

Claims

1. A gearbox ( 1 ) having at least two gears and comprising: a first gearshaft (3); a second gearshaft (4) selectively engagable with the first gearshaft via the at least two gears; and at least one clutch mechanism (8 ,9) located on the second gearshaft and configured to selectively engage the first gearshaft with the second gearshaft, the clutch mechanism including: a synchronizer (10); at least one clutch plate (12) attached to a gear (5b, 6b) on the second gearshaft; and at least one pressure plate (13) associated with the synchronizer; wherein the clutch plate and the pressure plate are configured to selectively engage one another, and the synchronizer is configured to drivingly engage the second gearshaft so that the second gearshaft is driven by the first gearshaft.

2. The gearbox of claim 1, wherein the gear is drivingly coupled to an input gear (5a, 6a) fixed to the first gearshaft and the pressure plate is attached to a cylindrical member (14) coupled to the synchronizer.

3. The gearbox of claim 1 , further including an output gear (7) fixed to the second gearshaft, the output gear configured to drive the second gearshaft.

4. The gearbox of claim 3, wherein the clutch mechanism is configured to engage the output gear.

5. The gearbox of claim 4, wherein the synchronizer of the clutch mechanism is configured to engage the output gear.

6. The gearbox of claim 5, further including a synchronizer adjustment mechanism (1 1) configured to move the synchronizer axially along the second gearshaft.

7. A method for directing a clutch mechanism (8, 9) to engage a first gearshaft (3) with a second gearshaft (4) of a gearbox (1), the clutch mechanism including a synchronizer (10), a clutch plate (12), and a pressure plate (13) located on the second gearshaft, the method comprising: engaging the clutch plate, attached to a gear (5b, 6b) drivingly coupled to an input gear (5a, 6a) fixed to the first gearshaft, with the pressure plate associated with the synchronizer; and engaging the synchronizer with the second gearshaft so that the second gearshaft is drivingly engaged with the first gearshaft.

8. The method of claim 7, wherein engaging the synchronizer with the second gearshaft includes engaging the synchronizer with an output gear (7) fixed to the second gearshaft.

9. The method of claim 7, wherein engaging the synchronizer with the second gearshaft includes directing a synchronizer adjustment mechanism (1 1) to move the synchronizer axially along the second gearshaft to engage the output gear fixed to the second gearshaft.

10. A machine including the gearbox of claims 1-6.