The invention also relates to a gearchange method.

Background Transmission of substantially the kind indicated above are previously known. A transmission is thus known from DE 33 08 525 in which an auxiliary shaft is arranged to be braked by a friction brake arrangement for synchronisation purposes. The technique thus known involves disadvantages in the form of high manufacturing and maintenance costs because the brake comprises brake plates and counterplates in a mutually axially movable configuration. Nor is a design of that kind ideal, since automatic adjustment of the rotation speed of the auxiliary shaft is usually necessary.

One object of the present invention is thus to provide a synchronisation brake for an auxiliary transmission shaft, which brake can be manufactured and maintained at lower cost than the state of the art and allow a better-defined control characteristic than the state of the art.

Summary of the invention The object of the invention is achieved with a transmission with features according to the attached claims 1 and 6. Preferred embodiments are specified in the respective dependent claims.

Brief description of the drawings The invention is described below in more detail with reference to examples of embodiments and the attached drawings, in which - Fig. 1 depicts schematically a transmission with a first embodiment of the invention, - Fig. 2 depicts a general view of a computerised control system for, inter alia, gearchanging, which system is intended to be used for applying the invention, and - Fig. 3 depicts schematically but in more detail a transmission with lubricating oil pump of rotary type, but not depicting an auxiliary shaft.

In Fig. 1, ref. 1 denotes a transmission constituting part of a driveline of an undepicted motor vehicle, e. g. a truck. The transmission comprises inter alia a main shaft 2 arranged to be driven via a clutch 3 by the motor vehicle's engine 4, and at least one auxiliary shaft 5.

The auxiliary shaft 5 acts upon and drives an oil pump 6 arranged to pump lubricating oil within the transmission to bearings 7 etc. in a conventional manner.

According to the invention, the oil pump is also arranged to serve as synchronisation brake for braking of said auxiliary shaft, to which end the oil pump is provided on its outlet side 8 with an adjustable constriction 9 arranged for adjustable braking of said auxiliary shaft.

The synchronisation brake indicated is arranged to be used during shaft speed synchronisation for a gearchange, and according to preferred embodiments the transmission is managed by a computerised control system 10 (Figs. 1 and 2) for the vehicle's driveline, arranged inter alia for mechanical gearchange with engine control, e. g. a system which is marketed under the name Opticruise and is schematically depicted in Fig. 2. The circled reference notations in Fig. 2 do not refer to the present description. The transmission may of course be managed and controlled by another computerised control system of a substantially corresponding kind and with substantially corresponding functions.

The control system is thus arranged for, inter alia, automatically controlled gearchanges with the vehicle's clutch engaged.

According to one version of the invention, synchronisation braking of the auxiliary shaft is arranged to be controlled by the computerised control system 10, whereby adjustment of braking is intended to be effected in response to shaft speed measurements and in this case by adjustment of the constriction 9, the adjustment being effected by means of, for example, a suitable actuator of a known kind arranged to act upon a preferably stepless choke valve of a suitable known kind.

According to the version depicted in Fig. 3, the oil pump 6 of rotary type arranged to pump oil from an oil sump 11 in the transmission's bottom portion 12 to desired portions via an oil filter 13 for pressure lubrication, to which end the adjustable constriction 9 is arranged on the outlet side 8 of the pump for adjustable constriction of the oil flow being delivered and hence adjustable braking of the auxiliary shaft which is arranged to drive the oil pump.

Likewise according to the preferred version, braking of said auxiliary shaft is intended to be effected for gearchange optimisation with the object of reducing gearchange time, particularly in the case of automatically controlled gearchanges with the clutch engaged.

It is also preferable that the control system be so arranged that constriction of the lubricating oil flow from the oil pump and hence braking are effected at times when the transmission is not transmitting any torque, i. e. when the transmission is under no load. During periods of restricted lubrication, the transmission is thus unloaded.

According to one version, braking to this end is intended to be effected after a gear has been disengaged and before the next gear is engaged.

Like the functioning of the transmission according to the invention, the method has probably been substantially indicated above.

An auxiliary shaft which acts drivingly upon an oil pump for lubrication of the transmission is also used for braking the auxiliary shaft for synchronisation purposes, to which end an adjustable constriction is arranged on the outlet side of the oil pump.

In addition to the general advantages which may be afforded by a synchronisation brake, inter alia in the form of quicker gearchanges and automatically controlled gearchanges, the invention makes it inter alia possible, as compared with the state of the art, for an existing oil pump to be used, and for the technical solution concerned to provide a simple and inexpensive installation which requires little maintenance and which also provides extraordinarily well-defined stepless adjustability.

The invention is described above in connection with examples of embodiments. A multiplicity of embodiments, as also minor modifications and additions, are of course conceivable, without having to depart from the concept of the invention.

The invention has therefore not to be regarded as limited to the embodiments indicated above but may be varied within its scope indicated by the attached claims.