GB2506506A

GB2506506A - Gear lever lock

Info

Publication number: GB2506506A
Application number: GB1314128.8A
Authority: GB
Inventors: Roul D Arjyashree; Abhinav Juyal; Rakesh Puri; Karthikeyan Tr
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2013-08-07
Filing date: 2013-08-07
Publication date: 2014-04-02
Also published as: GB201314128D0

Abstract

A shifting device (10, fig 1), for shifting gears of a manual gearbox of a vehicle, comprises a gear lever 14 movable between at least one neutral position and at least one engaging position. The shifting device (10) comprises a locking device 16 having at least one locking element 18 for blocking the movement of the gear lever 14 from the neutral position into the engaging position. Locking element 18 may have a receptacle 26, attached to the gear lever 14, which engages with a locking pin 22 that is moveable by an actuator 24, e.g. an electric, electromagnetic, pneumatic actuator. The shifting device (10) comprises a shift gate along which the gear lever is movable to engage respective gears and a selection gate extending perpendicular to the shift gate. If a driver leaves a hand on the drive lever 14 while in neutral, the locking device 16 prevents movement of the gear lever 14 and thereby accidental engagement of synchronization devices in the gearbox. Reference is also made to a method for operating a shifting device (10).

Description

Shifting Device for a Manual Gearbox as well as Method for Operating a Shifting Device for a Manual Gearbox The invention relates to a shifting device according to the preamble of patent claim 1 as well as a method for operating a shifting device.

Shifting devices for manual gearboxes of vehicles are well known from the series production of vehicles. Such a shifting device serves for shifting gears of the manual gearbox. For this purpose, the shifting device comprises a gear lever movable between at least one neutral position and at least one engaging position for engaging a gear of the gearbox. In other words, in order to engage a gear of the gearbox of the vehicle, the gear lever is moved from the neutral position into the engaging position. In the neutral position of the gear lever, no gear of the gearbox is engaged.

The gearbox usually has a synchronization device having at least two synchronization elements forming a so called synchro pair, the synchro pair serving for synchronizing the rotational speeds of two gear wheels, wherein one of said gear wheels belongs to one gear and the other gear wheel belongs to another gear of the gearbox. For example, the synchronization elements are configured as synchronizer rings in the form of cones or double cones. It has been shown that excessive wear and overheating of the synchronization elements can occur which can result in a premature failure of the synchronization device.

In DE 698 11 944 T2, a gear box for a vehicle can be found, the gear box comprising a control shaft for shifting gears of the gearbox. For shifting gears, the control shaft is movable. The control shaft is connected to a gear lever so that the control shaft can be moved via the gear lever. The gearbox also has a locking mechanism by means of which a movement of the control shaft and thus the gear lever form a neutral position in an engaging position for engaging a gear of the gear box can be blocked. However, this locking mechanism is very complex.

It is therefore an object of the present invention to provide a shifting device for a manual gearbox as well as a method for operating a shifting device for a manual gearbox by means of which a premature failure of the synchronization device of the gearbox can be prevented in a particularly cost-efficient way.

This object is solved by a shifting device having the features of patent claim 1 and a method having the features of patent claim 6. Advantageous embodiments with expedient and non-trivial developments of the invention are indicated in the other patent claims.

In order to provide a shifting device indicated in the preamble of patent claim 1, by means of which a premature failure of a synchronization device of the gearbox can be prevented in a particularly easy and cost-efficient way, according to the present invention the shifting device comprises a locking device having at least one locking element for blocking the movement of the gear lever from the neutral position into the engaging position, the locking element being attached to the gear lever.

The basic idea behind the invention is that a premature failure of a synchronization device of the gearbox can be caused by the driver of the vehicle. When the vehicle is moving at high speed and the driver disengages the gear by moving the gear lever from the engaging position into the neutral position and keeps his hand on the gear lever or a gear shift knob attached to the gear lever, the gear lever is moved a bit out of the neutral position towards the engaging position but not completely into the engaging position due to the self-weight of the hand and cabin vibrations of the vehicle. Thereby, a synchronization device of the gearbox is actuated in such a way that a first synchronization element belonging to a gear wheel of a gear of the gearbox interacts with a second synchronization element belonging to another gear wheel of another gear of the gearbox, the synchronization elements serving for synchronizing the rotational speeds of the gear wheels.

Since the interaction of the synchronization elements is effected but the gear lever is not moved into the engaging position completely, the synchronization elements rotate in relation to each other with a very high difference between their rotational speeds. This results in very high temperatures of the synchronization elements, thus a premature failure of the synchronization device can occur.

By means of the locking mechanism of the shifting device according to the present invention, the movement of the gear lever out of the neutral position towards the engaging position can be retained or prevented, thus preventing the interaction of the synchronization elements. Hence, excessive wear and overheating of the synchronization elements as well as premature failure of the synchronization device can be prevented in a very easy and cost-efficient way since the locking element is attached to the gear lever.

Thereby, the level of complexity of the shifting device can be kept particularly low.

The invention also relates to a method for operating a shifting device for shifting gears of a manual gear box of a vehicle, the shifting device comprising a gear lever movable between at least one neutral position and at least one engaging position for engaging a gear of the gearbox. In the method according to the present invention, the movement of the gear lever from the neutral position into the engaging position is blocked by means of at least one locking element being attached to the gear lever. Advantageous embodiments of the shifting device according to the present invention are to be regarded as advantageous embodiments of the method according to the present invention and vice versa.

By means of the method according to the present invention, a misuse of the gearbox can be avoided when the driver moves the gear lever form the engaging position into the neutral position and rests his hand on the gear lever without actuating the clutch paddle.

By avoiding the misuse, a particularly high life of the gearbox can be realised since premature failure of the synchronization device can be avoided. The locking mechanism can be utilized for downshift protection as well as upshift protection which allows for the protection of the corresponding gear wheels and synchronization elements of the corresponding gears.

Further advantages, features, and details of the invention derive from the following description of preferred embodiments as well as from the drawing. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respective indicated combination, but also in any other combination or taken alone, without leaving the scope of the invention.

The drawing shows in: Fig. 1 a schematic and perspective view of a shifting device for a manual gearbox, the shifting device comprising a gear lever for shifting gears as well as a locking mechanism for blocking the movement of the gear lever from at least one neutral position into at least one engaging position, the locking device having at least one locking element attached to the gear lever; Fig. 2 part of a schematic and perspective view of the shifting device; Fig. 3 part of a schematic and perspective sectional view of the shifting device; Fig. 4 a table for illustrating the working principle of the shifting device; Fig. 5 a schematic and perspective view of a wire serving for illustrating the working principle of an actuator according to a first embodiment, the actuator serving for moving a locking pin for blocking the movement of the gear lever; Fig. 6 a schematic and perspective view of a coil around a soft iron pin, the coil and the pin serving for illustrating the working principle of the actuator according to the first embodiment; Fig. 7 a schematic sectional view of a coil serving for illustrating the working principle of the actuator according to the first embodiment; and Fig. 8 a schematic sectional view of the actuator according to a second embodiment serving for moving the locking pin.

Fig. 1 shows a shifting device 10 for shifting gears of a manual gearbox of a vehicle. The shifting device 10 comprises an armature 12 which can be attached to the body of the vehicle. In other word, the armature 12 is vehicle-fixed. The shifting device 10 also comprises a gear lever 14 which is movably supported on the armature 12. Hence, the gear lever 14 can be pivoted in the longitudinal direction of the vehicle and in the transverse direction of the vehicle in relation to the armature 12. By pivoting the gear lever 14 in the transverse direction of the vehicle, one of several shift gates not shown in Fig. 1 can be selected when the gear lever 14 is in its neutral position. In the neutral position, no gear of the manual gearbox is engaged. In order to engage a gear of the manual gearbox, the gear lever 14 can be moved from the neutral position into respective engaging positions along the respective shift gates.

In order to realize a comfortable shifting of the gears, the gearbox comprises a synchronization device. The synchronization device comprises synchronization elements from which one synchronization elements belongs to a gear wheel of a gear and another synchronization element belongs to another gear wheel of another gear of the manual gearbox. The synchronization elements can interact in such a way that the rotational speeds of the gear wheels are synchronized by means of the synchronization elements.

Thereby, the driver of the vehicle can switch from one gear to the other very smoothly and without actuating the accelerator paddle. For example, the synchronization device can be configured as a double cone synchronization device, the synchronization elements being synchronization rings in the foim of synchronization cones.

The interaction between the synchronization elements is effected when the gear lever 14 is moved a bit out of the neutral position towards one of the engaging positions without moving the gear lever 14 completely into the engaging position. In other words, the synchronization elements interact before the gear is engaged.

Conventionally, this can lead to an accidental misuse of the gearbox caused by the driver.

When the vehicle moves at high speed and the driver disengages a gear, leaves the gear lever 14 in the neutral position and rests his hand on the gear lever 14, a force acting from the hand upon the gear lever 14 moves the gear lever 14 a bit out of the neutral position towards the engaging position without moving the gear lever 14 completely into the engaging position. For example, the gear lever 14 is moved towards the engaging position for engaging the fourth gear of the gearbox. This results in actuating the corresponding synchronization elements of the third gear and the fourth gear. The force moving the gear lever 14 towards the engaging position is also affected by cabin vibrations. Due to high differential rotational speeds of the gear wheels and the corresponding synchronization elements of the third gear and the fourth gear, excessive wear and overheating of the synchronization elements can occur. This can result in a premature failure of the synchronization device and the gearbox as a whole. The force applied to the gear lever 14 can be dependent on the length and the weight of the driver's arm as well as the position of the driver's seat.

In order to prevent such premature failure of the gearbox, the shifting device 10 comprises a locking device 16 for blocking the movement of the gear lever 14 from the neutral position into the engaging positions. In other words, the movement of the gear lever 14 from the neutral position into the engaging positions can be avoided or restrained in such a way that the interaction of the synchronization elements is prevented when the driver moves the gear lever 14 into the neutral position, leaves the gear lover 14 in the neutral position and rests his hand on the gear lever 14.

The locking device 16 comprises a locking element 18 attached to a moving part 20 of the gear lever 14 so that the locking element 18 can be moved along with the gear lever 14.

The locking device 16 also has a locking pin 22 which can be moved between a locking position shown in Fig. 2 and 3 and a release position shown in Fig. 8. The locking pin 22 is attached to the armature 12 via an actuator 24 of the locking device 16, the actuator 24 seiving for moving the locking pin 22 between the locking position and the ielease position.

As can be seen from Fig. 3 and 8, the locking element 18 attached to the gear lever 14 has a receptacle 26. In the locking position, the locking pin 22 engages the receptacle 26 thereby blocking the movement of the gear lever 14. In the release position, the locking pin 22 is moved out of the receptacle 26. In other words, the locking pin 22 does not engage the receptacle 26 in the release position, the locking pin 22 releasing the gear lever 14 in the release position so that the gear lever 14 can be moved from the neutral position into the engaging positions.

The actuator 24 for moving locking pin 22 is operated by an electronic control unit in the form of a microprocessor 28. In Fig. 2, a signal for operating the actuator 24 is illustrated by a directional arrow 30, the signal being transmitted from the microprocessor 28 to the actuator 24. By directional arrows 32 a-c, input signals transmitted to the microprocessor 28 are illustrated. The actuator 24 is operated by the microprocessor 28 in dependency at least the on input signals. For example, a first one of the input signals is a neutral signal transmitted from a neutral switch to the microprocessor 28, the neutral signal characterizing a state in which the gear lever 14 is in the neutral position.

The neutral signal provided by the neutral switch can be generated by means of a capturing device 34, the capturing device 34 comprising a proximity sensor 36 and a neutral pin 38 attached to the gear lever 14. By means of the proximity sensor 36, the position of the neutral pin 38 can be detected. Since the neutral pin 38 is movable along with the gear lever 14, the proximity sensor 36 can detect whether the gear lever 14 is in its neutral position or not. If the proximity sensor 36 detects that the gear lever 14 is in its neutral position, this information can be transmitted to the microprocessor 28 via the neutral signal so that the microprocessor 28 can effect the movement of the locking pin 22 from the release position into the locking position.

A second one of the input signals can characterize, for example, the vehicle speed. The third input signal can characterize the rotational speed of an engine of the vehicle, the engine serving for driving the vehicle.

The actuator 24 can be, for example, an electromagnetic or electromechanical actuator 24. The actuator 24 comprising at least one solenoid from moving the locking pin 22.

Fig. 4 shows a table with vehicle conditions, input parameters for the microprocessor 28 and output parameters of the microprocessor 28. One of the output parameters is a timer which characterizes the time the gear lever 14 is in its neutral position while the vehicle is moving.

In a further embodiment, the actuator 24 comprises at least one electromagnet attached to the moving part 20 of the gear lever 14. The locking pin 22 which is also referred to as plunger is attached to the vehicle-fixed armature 12. When the driver rests his hand on the gear lever 14 being in the neutral position, a current passing through the electromagnet attracts the plunger so that the plunger engages the receptacle 26, thus holding the gear lever 14 in its neutral position. Said current can be generated by the microprocessor 28 if at least one desired or predeterminable condition is satisfied.

The principle behind such an electromagnetic locking is shown in Figs. 5 and 6. In order to move the locking pin 22 from its release position into its locking position, electromagnetism is used when the electromagnet is energized. When the electromagnet is energized, a holding force acts upon the locking pin 22, the holding force holding the locking pin 22 in the locking position. The holding force should be collinear with the load and the receptacle 26 and the locking pin 22 should be face to face to achieve optimal operation.

The magnetic locking mechanism relies upon some of the basic concepts of electromagnetism. Essentially, it consists of an electromagnet attracting a conductor in the form of the locking pin 22 with a force large enough to prevent the gear lever 14 being moved into the engaging positions. The magnetic locking mechanism makes use of the fact that a current through one or more loops of a wire 40 shown in Fig. 5 produces a magnetic field, the loops of wire forming a solenoid or a coil 42. If the coil 42 is wound around a ferromagnetic core such as a pin 44 made of soft iron, the effect of the magnetic field is amplified. This is because the internal magnetic domains of the material align with each other to greatly enhance the magnetic flux density B. Using the Biot-Savart law, it can be shown that the magnetic flux density B induced by a solenoid of effective length I with a current I through N loops of wire is given by the equation a): = The force F between the electromagnet and the plunger with surface area S exposed to the electromagnet is given by the equation b): In both equations a) und b), Po represents the permeability of free space and Pr the relative permeability of the core.

Fig. 7 shows a magnetic field produced by a solenoid, the magnetic field being illustrated by directional arrows. Fig. 7 shows a cross section through the center of the coil 42.

Crosses shown in Fig. 7 illustrate the current flowing into the image plane of Fig. 7. Dots shown in Fig. 7 illustrate the current flowing out of the image plane in the wire 40.

This principle of an electromagnet for moving the plunger (locking pin 22) can also be used for the actuator 24 shown in Figs. 1 and 2, the electromagnet of the actuator 24 being attached to the armature 12 and serving for moving the locking pin 22 into an out of the receptacle 26.

Fig. 8 shows an embodiment of the actuator 24 being a pneumatic actuator. Hence, the locking mechanism will be operated by air available in a tank. For example, a solenoid can be actuated by the microprocessor 28 when at least one desired condition is satisfied.

After the actuation of the solenoid, the air can flow into a working chamber 45 bounded by a cylinder 46 and a piston 48 of the actuator 24, the air being illustrated by directional arrows and pushing the piston 48 towards the locking element 18. As can be seen in Fig. 8, the locking pin 22 is coupled to the piston 48 via a piston rod 50. Thereby, the locking pin 22 can be moved along with the piston 48. Moreover, a duct element 52 is provided. By moans of the duct clement, the air can be guided from the tank through the duct element 52 into the working chamber 45.

In order to move the locking pin 22 from its locking position into its release position, for example, an exhaust port of the working chamber 45 is opened by the microprocessor 28 so that the air can flow out of the working chamber 45. Then, springs 54 push the piston 48 and the locking pin 22 away from the locking element 18 so that the locking pin 22 is moved out of the receptacle 26. The springs 54 are supported on the cylinder 46 on the one side and the piston 48 on the other side. When the piston 48 is pushed towards the locking element 18 by means of the air, the springs 54 are loaded. This means that the springs 54 are preloaded in the locking position. By venting the working chamber 45, the springs 54 can expand at least partly thereby pushing the locking pin 22 form its locking position in its release position.

Claims

Claims A shifting device (10) for shifting gears of a manual gearbox of a vehicle, the shifting device (10) comprising a gear lever (14) movable between at least one neutral position and at least one engaging position for engaging a gear of the gearbox, characterized in that the shifting device (10) comprises a locking device (16) having at least one locking element (18) for blocking the movement of the gear lever (14) from the neutral position into the engaging position, the locking element (18) being attached to the gear lever (14).
2. The shifting device (10) according to claim 1, characterized in that the locking element (18) has a receptacle (26), wherein the locking device (16) comprises a locking pin (22) movable between a locking position and a release position, the locking pin (22) engaging the receptacle (26) in the locking position thereby blocking the movement of the gear lever (14), the locking pin (22) releasing the gear lever (14) in the release position.
3. The shifting device (10) according to claim 2, characterized in that the locking device (16) comprises an actuator (24) for moving the locking pin (22).
4. The shifting device (10) according to claim 3, characterized in that the actuator (24) is an electric actuator, electromagnetic actuator or pneumatic actuator.
5. The shifting device (10) according to any one of the preceding claims, characterized in that the shifting device (10) comprises at least to shift gates along which the gear lever (14) is movable into respective engaging positions for engaging respective gears of the gearbox, wherein the gear lever (14) is movable between the shift gates along a selection gate extending perpendicular to the shift gates while the movement of the gear lever (14) into the engaging positions is blocked by the locking element (28).
6. A method for operating a shifting device (10) for shifting gears of a manual gearbox of a vehicle, the shifting device (10) comprising a gear lever (14) movable between at least one neutral position and at least one engaging position for engaging a gear of the gearbox, wherein the movement of the gear lever (14) from the neutral position into the engaging position is blocked by means of at least one locking element (28) being attached to the gear lever (24).