GEARBOX WITH LINKAGE ROD

DESCRIPTION

The present invention relates to a semiautomatic gearbox for vehicles, such as motorcycles, quads, go-karts and automobiles, in particular for gearboxes with a linkage rod.

In vehicles the sequential or synchronized gear shift lever can be connected to the gearbox via linkage rods.

Passage from one gear to another is known to involve the following operations: a) reducing the engine fuel feed ("throttle" in technical jargon), b) operating the clutch, c) engaging the gear, d) releasing the clutch, e) returning engine fuel feed to the required level.

This succession of operations, especially during fast running, has a negative influence both on the smoothness of vehicle running and on the running behaviour of the vehicle, which can lead to dangerous instability, together with a loss of performance. Utility model application MI2022U000396 filed in the name of the present applicant describes a motorcycle gear shift lever directly coupled to the gearbox itself, characterised by comprising at least one extensimeter positioned on the gear shift lever. By means of an electronic circuit the extensimeter is able to interrupt the current feed to the spark plug or plugs in response to the operation of the gear shift lever. In this manner the gear can be changed without the need to operate the clutch and reduce the "throttle". Sensors for linkage rods are commercially available, using microswitch sensors, magnetic sensors or extensiometric sensors which for their installation require the linkage rod to be modified (cut, threaded) or replaced.

These sensors, with the exception of extensimetric sensors, which however have a very high cost, they require mechanical calibration, they often present a sensation of operational slack and are subject to wear and to malfunction caused by dirt.

An object of the present invention is to provide a semiautomatic gearbox for vehicles with a linkage rod-fitted gearbox which is of simpler construction and overcomes the drawbacks and limits of the aforesaid sensors. This and further objects are attained according to the present invention by a semiautomatic vehicle gearbox comprising: a gear shift lever coupled to said gearbox via a linkage rod; and a washer- shaped sensor of piezoelectric type for sensing the operation of said shift lever; characterised in that said sensor is coupled to said linkage rod.

Further characteristics of the invention are described in the dependent claims.

According to the present invention, a semiautomatic gearbox can be provided without replacing any part of the gearbox, but by merely adding a sensor to the gearbox linkage rod. The linkage rod is neither replaced nor modified.

Moreover, by using a piezoelectric sensor the electronic circuits used for reading and processing the sensor signal are simplified, in particular compared with extensimetric sensors. Advantageously, this modification can be made for all types of vehicles provided with a mechanical gearbox with linkage rod.

The characteristics and the advantages of the present invention will be apparent from the ensuing detailed description of one embodiment thereof illustrated by way of non-limiting example in the accompanying drawings, in which:

Figure 1 is schematic view of a shift lever coupled to the gearbox via a linkage rod, in accordance with the present invention;

Figure 2 is a block diagram relative to the engine electrical feed control; With reference to the accompanying figures, an embodiment of a semiautomatic vehicle gearbox having a linkage rod, in accordance with the invention, in particular for motorcycles, comprises a shift lever 10 having a pedal crank 11 at one end.

The shift lever 10 comprises a projection 12 on which a linkage rod 13 is fixed. The linkage rod 13 is then connected to a gearbox 14.

A threaded ball joint 15 (uni-ball type) is fixed to one end of the linkage rod 13 and is locked by a nut 16 positioned between the ball joint 15 and the linkage rod 13.

The ball joint 15 is fixed to the projection 12 by a bolt 17 and nut 18. Another threaded ball joint 20 (uni-ball type) is connected to the other end of the linkage rod 13, and is normally locked by a nut 21 positioned between the ball joint 20 and the linkage rod 13.

According to the present invention, a sensor 22 in the form of a washer, i.e. a disc with a central hole of diameter slightly greater than the diameter of the thread of the ball joint 20, is positioned between the nut 21 and the linkage rod 13.

An electric cable 23 extends from the sensor 22 for connection to a central control unit 40.

The ball joint 20 is connected to one end of a lever 24 by a bolt 25 and nut 26.

The other end of the lever 24 is fixed to the shaft 27 of the gearbox casing 14 by a fixing bolt 28.

The central control unit 40 is connected electrically by a cable 41 to the vehicle electrical/electronic circuits 42 which feed the spark plug or plugs (not shown) via a cable 43.

The sensor used is a washer shaped piezoceramic sensor with its polarities on the two opposing flat faces.

The sensor 22 can be applied to one of the two ends of the linkage rod 13, preferably to that located close to the gearbox casing 14, because of the greater space available. However there is nothing to prevent it from being positioned at other points of the linkage rod, if possible.

When a vehicle gear change is required, the driver operates the gear shift lever connected to the gearbox shaft 27 by the linkage rod 13. This action by the driver subjects the linkage rod 13 to a compression or expansion force sensed by the sensor 22. The sensor 22 is sensitive to the point that, itself being fixed to the rod 13 by the nut 21 , it would be blocked, however if a force is applied to change gear, either the possible slack of the thread on the ball joint 20, or the extension or compression of the thread, is sufficient for the sensor 22 to produce a signal. When the sensor 22 is installed, the nut 21 is tightened against the rod 13. The sensor is hence compressed and produces an electric signal, however because of the characteristics of piezoelectric sensors, when tightening is discontinued the sensor is zeroed and a signal is produced only if it is again subjected to a new force. The energy deriving from the action on the gearbox is sensed by the sensor 22 and its value is acquired by the central control unit 40 which shuts off electrical feed to the spark plug or plugs by means of the electrical/electronic circuits 42.

The central control unit 40 amplifies the signal from the sensor 22 and acts on the engine operating system to enable the gear to be engaged without operating the clutch and/or even minimally releasing the accelerator. The said electronic circuit can act in various ways on the motorcycle operation to interrupt or reduce the engine torque in addition to interrupting electrical feed to the spark plugs. In particular, injector feed can be interrupted or a particular channel of the engine central control unit dedicated to this function can be acted upon, or the engine shut-off switch can be operated. The central control unit 40 can also be regulated to suitably choose the intervention threshold voltage beyond which gear change must take place.

The central control unit 40 is not further described as its construction is known to an expert of the art.

The fact that the sensor 22 is directly associated with the bolt linkage rod 13, in accordance with the present invention, makes the device virtually universal, i.e. suitable for any type of vehicle having a lever connected to the shaft axis, such as motorcycles, quads, go-karts and automobiles.

The sensor 22 is preferably in the form of a washer to facilitate its construction and mounting, however other forms can be used. For example, sensors of different shapes and smaller dimensions can be used (for example a small piezoelectric cylinder), positioned within a mechanical structure (for example a pair of washers) and coupled to the linkage rod.

The system conceived in this manner is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept; moreover all details can be replaced by technically equivalent elements.