Technical Field

The present invention relates to a direction control system that allows selection between forward and backward motion in gearboxes especially used in tractors and heavy duty vehicles. With the present invention, the motion direction of a power transmission system such as a gearbox may be changed without severing its connection to the source of motion such as a vehicle engine.

Prior Art

Various clutch systems developed for making a selection between forward and backward motions in vehicles are known. These systems are usually controlled through hydraulic control systems.

US5662198A describes a two-way hydraulic clutch system. This system aims at providing proper motion transmission by preventing two sequential double clutches from overlapping. The system is formed by sequentially arranging 2 clutch systems in opposite directions so as to operate independently from each other with a stationary hub. The system works by transmitting liquid from an oil circuit to a piston under a pressure that squeezes friction elements and, for motion in the opposite direction, squeezing secondary friction elements as a result of pressure applied on another piston with another oil circuit in order to increase torque. Pistons squeezing the friction elements move independently from each other and provide transmission with ease by joining the clutches located on both ends. However, when the piston and first friction element located in the first clutch shift axially, the second clutch and second friction element also tend to drag axially. This leads to an increase in friction and an unbalanced motion within the gearbox.

In US4736653A, a power transmission system is disclosed. In the clutch and release assembly of this system, interlocking and separation between the central shaft and the peripheral shaft located around this central shaft is realised as the teeth outside the central shaft and the teeth in the tube located within the clutch start moving. The clutch cylinder comprises a piston actuated by fluid pressure and a clutch plate consisting of multiple disks. The central shaft provides forward motion of the system while the peripheral shaft provides motion in the opposite direction. This system was designed for four wheel drive vehicles. > Moreover, transmission's size on the horizontal axis and the oiling system are scaled down with this system to obtain a compact design.

In US2011030493A1, a mechanism comprising a double clutch unit is mentioned. In the aforesaid mechanism, clutching is performed hydraulically. However, the motion transmission, which takes place while disk and linings included in the non-coaxial structure are slowing down the motion prior to rotation to the opposite direction, leads to using a large number of bearings and gears.

In EP2075487A2, a gearbox system is disclosed wherein forward - backward selection is made by using a hydraulic fluid. In Figures 13 and 20, juxtaposed forward- backward clutch system with hydraulic drive is illustrated.

In JP2010096215A and GB2274493A, non-coaxial clutch mechanisms are mentioned wherein disks and linings included in these are located so as to facilitate stopping and reversing the motion.

In CN101576145A, two engaged coaxial clutch mechanisms are disclosed

Purpose of the Invention

The aim of the present invention is to develop a direction control system that transmits the rotational motion generated by a motion source to the same or opposite direction. For instance, the aim is to develop a direction control system in a vehicle, especially such as a tractor or a heavy duty vehicle, which transmits motion provided by an engine in such a manner that the vehicle moves in the backward or forward direction.

A further aim of the invention is to develop a direction control system that is activated by fluid pressure and may utilise existing systems such as a hydraulic power steering system in order to accomplish this.

Brief Description of the Invention

The input for the direction control system developed with this invention is provided by an input shaft that extends through an axis and rotated by a motion source. A clutch input element is provided whose centre is the said axis and which is attached to the said shaft and co-rotates with this input shaft. Entering the system, motion is transmitted to a first clutch output element that rotates by receiving motion from and is coaxial with the clutch input element through a first lining set squeezed by a first piston or to a second clutch output element that rotates by receiving motion from and is coaxial with the clutch input element through a second lining set squeezed by a second piston. Furthermore, an output shaft is included that extends along the said axis and to which the first clutch output element is attached directly and the second clutch output element is attached via an idle gear set in order to reverse rotational direction. Thus, the output shaft is turned by the first clutch output element in the same direction as the input shaft when the first piston is activated, while it is turned by the second clutch output element in the opposite direction of the input shaft when the second piston is activated.

The direction control system according to the invention is controlled by pressure of a fluid such as oil. A fluid circuit used for this end is activated by a lever, a double switch or a similar equipment accessible by a user in line with his/her choice of direction, to provide motion in the first or second direction. The activated fluid circuit provides motion transmission in the corresponding direction by activating the first piston when the first direction is selected and the second piston when the second direction is selected.

When the selected direction is changed, the activated piston is turned back to its inactive position with a spring set. The need for pressurised fluid is reduced by utilising a spring set to bring pistons to their inactive position. This, therefore, allowed supplying pressurised fluid from an existing system, for instance a power steering fluid in a vehicle.

Description of Figures

The figures required for a better explanation of the present invention and their corresponding descriptions are listed below:

Figure-1: A schematic view of the direction control system in a tractor.

Figure-2: A cross-sectional perspective view of the direction control system in a tractor gearbox.

Figure-3: A cross-sectional view of the shaft, clutch input element and first clutch output element.

Figure-4: A cross-sectional view of the second clutch output element. Description of Features/Sections/Parts Constituting the Invention

Parts and sections are numbered individually for a better explanation of the invention and description of each number is provided below.

1. Input shaft

2. Clutch input element

3. First piston

4. First lining set

5. First clutch output element

6. Second piston

7. Second lining set

8. Second clutch output element

9. Idle gear set

10. Output shaft

11. Pressure channel

12. Spring

13. Intermediate member

14. Oiling channel

A. Direction control system

B. Engine

C. Main clutch

D. Speed change gears

E. Differential

F. Wheel Detailed Description of the Invention

The direction control system (A) according to the invention that transmits rotational motion generated by a motion source in the same or opposite direction basically comprises

- an input shaft (1) extending along a rotational axis that is turned by a motion source,

- a clutch input element (2) connected to the said input shaft (1) coaxially that rotates along with the said input shaft (1),

- a first clutch output element (5) that is coaxial with the clutch input element (2) and rotates by receiving motion from the clutch input element (2) via a first lining set (4) squeezed by a first piston (3),

- a second clutch output element (8) that is coaxial with the clutch input element (2) and rotates by receiving motion from the clutch input element (2) via a second lining set (7) squeezed by a second piston (6),

- an output shaft (10) that extends along the said axis and to which the first clutch output element (5) is attached directly and the second clutch output element (8) is attached via an idle gear (9) set so as to reverse rotational direction, and

- a user activated pressurised fluid circuit that activates the first and second pistons (3, 6)

- pressure channels (11) transmitting pressurised fluid provided by the said pressurised fluid circuit to the first piston (3) or the second piston (6) and

- springs (12), each compressing when the pistons (3,6) are activated, that determines the threshold value for fluid pressure upon which pistons (3,6) activate and squeeze lining sets (4,7), and stops motion transmission to the first and second clutch sets (5, 8) when fluid pressure is interrupted by releasing said lining sets (4, 7).

The clutch input element (2) and the second clutch output element (8) are shaped like dishes facing each other. Said dish shape creates a space between the clutch input element (2) and the second clutch output element (8). In this space, an intermediate element (13) is provided, which is an extension of the first clutch output element (5) and the clutch input element (2) respectively, in a direction parallel to the rotational axis from the clutch input element (2) towards the second clutch output element (8) and radially inwards. Co-rotation of the first clutch output element (5) with the clutch input element (2) is ensured as the teeth located on the outer surface of the first lining set (4) that is squeezed with the activation of the first piston (3) interact with the teeth located on the inner surface of the clutch input element (2) and the teeth located on the inner surface of the first lining set (4) interact with the teeth located on the outer surface of the first clutch output element (2). Thus, it is ensured that the output shaft (10) rotates in the same direction as the input shaft (1).

Co-rotation of the second clutch output element (8) with the clutch input element (2) is ensured as the teeth located on the inner surface of the second lining set (7) that is squeezed with the activation of the second piston (6) interact with the teeth located on the outer surface of the intermediate element (13) and the teeth located on the outer surface of the second lining set (7) interact with the teeth located on the outer surface of the second clutch output element (8). Thus, it is ensured that the output shaft (10) rotates in the opposite direction of the input shaft (1).

With this arrangement wherein the clutch input element (2), the first and second clutch output elements (5, 8) and the intermediate element (13) engage each other a compact direction control system (A) is achieved with low friction related loss.

In a preferred embodiment of the invention, each of the said springs (12) consist of at least two washers whose centre is the said axis, wherein one plain washer and one conical washer are located consecutively and adjacently. Need for pressurised fluid is reduced by using, instead of fluid pressure, springs with conical washers (12) working against fluid pressure while bringing the pistons (3, 6) to their inactive positions. This, therefore, allowed supplying pressurised fluid from an existing system.

The direction control system (A) according to the invention is used preferably in a vehicle gearbox in order to make a selection between said vehicle's forward or backward motion. Within the scope of this use, rotational motion received from the vehicle engine (B) through a main clutch (C) is transmitted firstly to the speed change gears (D) and then to the wheels (F) via differentials (F) by the direction control system (A) in a direction corresponding to forward and backward motion of the vehicle. In this case, for instance, when the first piston is activated the vehicle moves forward, while as the second piston is activated the vehicle moves backwards.

When the direction control system (A) according to the invention is used in a vehicle gearbox, the pressurised fluid system for activating the pistons is preferably a hydraulic power steering system. In a related embodiment of the invention, power steering hydraulic oil is also used for oiling the direction control system (A). In order to achieve this, oiling channels (14) are provided on the direction control system (A) conveying hydraulic oil to suitable spaces located within the direction control system (A) and between the direction control system (A) and the gearbox body. Thus, both activating pistons, and consequently direction selection, and oiling is realised with a single hydraulic system.