GEAR CONTROL DEVICE

Field of the invention

The present invention relates to a gear control device for a vehicle gear, which gear control device comprises a gear lever for setting gear positions, and activation means which cooperate with the gear lever and are adapted to initiating the engagement of gears corresponding to gear positions set.

Background to the invention

In conventional gear changing in a vehicle, the gear change movement is transmitted mechanically from the gear lever to the gearbox. This is usually effected by means of link rods which move shafts and/or gearwheels in the gearbox relative to one another as a consequence of whatever gear position is set via the gear lever. This entails the creation of a mechanical resistance from friction forces and counterforces which the driver clearly perceives when changing gear. Changing gear and engaging a different one imparts a definite sensation to the driver's hand. There are gearboxes where control is no longer based on this principle but involves a more indirect interaction between the position of the gear lever and whatever gear is being engaged, e.g. via electrical signals. Such cases do of course not entail the creation of any resistance to the gear change movement. The fact that the driver does not physically perceive gear positions being set may create a feeling of uncertainty. This is particularly so in cases where the gear positions are arranged sequentially along a line, which means that the gear lever may pass through a number of gear positions without the driver having any perception of this happening. To some extent, this problem can be reduced by the gear lever acting upon a profiled rod with recesses which define gear positions and a spring-loaded ball which is pressed against the profiling to indicate the fixed gear positions, but much of the feeling of uncertainty described above still remains.

The situation which occurs with the types of gear described above prompted to a greater or lesser extent the subject matter of the patent specifications referred to below. US 6 834 562 describes a gear system with a gear lever and an electrical

monitoring device for detecting the positions of the gear lever. The system is provided with a mechanical arrangement whereby gear change sensation is created by a number of coil springs.

US 6 732 847 describes transmission by wire and a gear lever with recesses corresponding to the transmission's gear positions.

US 5 540 114 describes a gear change device which comprises two photosensors for detecting the positions of the gear lever. A cam arrangement is connected to the gear control rod to impart a resistance which provides the driver with gear change sensation. US 4 912 997 describes a manual gear with electrical signal transmission in which a ball joint and a cam track cooperate to create stability in gear changing and a sensation of conventional gear changing.

US 2005 0160861 describes a gear lever provided with a rolling element fastened to a movable block whereby the gear lever can be pivoted into various regions. The arrangements described above succeed to varying extents in overcoming the problem of lack of gear change resistance. Such mechanical solutions entail wear, so their characteristics change during their service life. The mechanical devices are also complicated, which renders them expensive and liable to malfunction.

The object of the present invention is to eliminate or at least reduce the problem of inadequate gear change resistance described above in such a way as not to entail disadvantages such as are associated with the devices described in the aforesaid specifications.

Summary of the invention

The stated object is achieved according to the invention by the gear control device further comprising a fluid-operated damping device adapted to exerting a resistance to gear lever movement.

The damping device creating this resistance to gear change movement recreates the feeling of a conventional mechanical gear. As the damping device is fluid-operated, it is not subject to mechanical wear. It is very simple to implement and therefore inexpensive. The absence of wear means that the movement resistance is maintained at a distinct level. This makes it easy to create a movement resistance which is

relatively similar for the various gear positions.

According to a preferred embodiment, the activation means comprises electrical monitoring means adapted to detecting gear positions, and electrical signal means adapted to transmitting signals to the gearbox which represent positions detected. Electrical monitoring and signal transmission are particularly advantageous in this type of gear and the invented damping device is therefore particularly useful in such applications.

According to a further preferred embodiment, the device comprises an element which is movable by the gear lever and which has a profiled side with a plurality of recesses and also a body abutting springingly against the profiled side and adapted to being able to spring into any of the recesses.

These components provide an easy and reliable way of achieving distinct indication of gear positions in that each recess represents a gear position, and this version is certainly suitable for being combined with a damping device according to the invention.

According to a further preferred embodiment, the movable element is a shiftable rod and the springing abutting body is a ball.

The movable element being configured as a shiftable rod cooperating with a springing ball is particularly advantageous in providing a simple way of connecting a fluid-operated damping device.

According to a further preferred embodiment, the damping device is adjustable to regulate the resistance to the gear change movement.

The adjustability makes it possible to compensate for changes in operating conditions, e.g. temperature variations of the control fluid. It also affords the possibility of adapting the movement resistance to a level which the driver finds suitable and comfortable.

According to a further preferred embodiment, the fluid-operated damping device is a hydraulic damping device.

Although a pneumatic damping device is in principle within the scope of the invention, a hydraulic version is in most cases best suited for the purpose and provides a simple solution.

According to a further preferred embodiment, the hydraulic damping device comprises a hydraulic cylinder, which is a very simple and operationally reliable way of creating a counterforce to the gear lever.

According to a further preferred embodiment, the shiftable rod is arranged within the hydraulic cylinder, thereby achieving a simple and compact configuration in that the shiftable rod also performs a function in the damping device.

According to a further preferred embodiment, the shiftable rod is provided with a piston which is shiftable with the rod and which cooperates with the hydraulic cylinder.

The rod thereby acts as a piston rod and hence provides a direct connection between gear change movement and piston movement.

According to a further preferred embodiment, the piston abuts sealingly against the hydraulic cylinder and is provided with a connecting duct running through it.

Precise coordination of the movement resistance is thus easy to achieve by suitable dimensioning of the duct. According to a further preferred embodiment, the throughflow cross-sectional area of the connecting duct is adjustable.

The adjustability of the device can thus be achieved in an easily predictable way.

The advantageous embodiments indicated above of the gear control device invented are indicated in the dependent claims. Another aspect of the invention refers to a vehicle, in particular a truck provided with a gear control device according to the invention or any of its preferred embodiments.

The vehicle invented affords corresponding advantages achieved with the gear control device invented and its preferred embodiments as described above. The invention is explained in more detail by the detailed description of embodiment examples of it set out below with reference to the accompanying drawings.

Brief description of the drawings

Fig. 1 illustrates schematically a gear control device according to the invention. Fig. 2 illustrates a detail of a gear control device according to a second embodiment

example of the invention. Fig. 3 illustrates a detail of a gear control device according to a third embodiment example of the invention.

Fig. 4 illustrates a detail of a gear control device according to a fourth embodiment example of the invention.

Fig 5 illustrates a detail of a gear control device according to a fifth embodiment example of the invention.

Fig. 1 illustrates a gear lever 1 operated by the driver via a gear knob by means of which the gear lever is moved along a coulisse 3 to desired gear positions. The gears are arranged sequentially along the coulisse. The gear lever 1 is manoeuvred about a swivel joint 4 and has its lower portion 1 b connected to a rod 6 via a toggle joint 5 which allows changes of angle between the gear lever's lower portion 1 b and the rod 6. One side of the rod 6 is profiled with a plurality of recesses 7, each of which represents a gear position, in the example depicted a reverse position, a neutral position and four forward gears. A ball 8 is pressed against the profiled side of the rod 6 by a springing mechanism 9. When a gear change is effected by moving the gear knob 2 along the coulisse 3, the rod 6 is subjected to shifting whereby the ball 8 is pushed out of one recess 7 and into another recess 7 depending on the shift position of the rod. The position of the ball 8 in the recess 7 denotes a distinct gear position. The springing force of the mechanism 9 is sufficient to clearly indicate the respective gear position. The force is nevertheless relatively moderate to avoid wear and constitutes in itself a relatively small resistance to shifting the rod 6.

To create increased resistance to gear change movement, the rod is built into a hydraulic cylinder 10 with a first end wall 11 through which the rod 6 extends sealingly and a second end wall 12. A piston 13 is fastened to the end of the rod 6 which points away from the gear lever. The piston is provided with a connecting duct 14 connecting the two sides of the piston to one another. The hydraulic cylinder is filled with oil.

Movement of the piston 13 in either direction creates a resistance by the oil being compressed on one side, albeit being able to percolate through to the other side via the connecting duct 14. The diameter of the duct determines the amount of resistance created.

The gear positions are monitored by a detector 15 which monitors the angle between the gear lever's lower portion 1 b and the rod 6. The detector 15 sends electrical signals 16 to the gearbox for setting of the gear which corresponds to the angle detected. Fig. 2 illustrates an embodiment example in which the connecting duct 14 is provided with an adjustable throttle valve 27. The constriction of the throttle valve is controlled from a temperature sensor 17 which monitors the temperature of the oil.

The resistance force can thus be kept unchanged irrespective of temperature effects on its viscosity. As an alternative or in addition, the throttle valve 27 may be controlled manually by a control device 18 in the driver's cab.

Fig. 3 illustrates an embodiment example in which the piston 13 has no connecting duct. Instead, communication is established by a clearance 26 arranged between the piston 13 and the hydraulic cylinder 10. For centring guidance of the piston 13, the latter's circumference may be provided with three ribs 19. Alternatively, these ribs may be arranged on the inside of the cylinder.

Fig. 4 illustrates an example in which communication between the two sides of the piston 13 is via an external line 20 which may likewise be provided with an adjustable throttle valve 21.

Fig. 5 illustrates an example in which the hydraulic cylinder 25 takes the form of a unit separate from the gear position rod 6. The hydraulic cylinder 25 thus has a separate piston rod 22 connected to the swivel joint 5 on the opposite side of the gear position rod 6. The piston 23 has a connecting duct 24 which may be provided with an adjustable throttle valve.

It is likely to be understood that the hydraulic resistance may be constituted in many different ways within the scope of the invention and be situated in different ways. The examples depicted all involve displacement, but it is likely to be understood that the resistance may also be constituted dynamically, e.g. by vanes.