Apparatus for facilitating gear changing in mechanical gearboxes

#The present invention relates to an apparatus for facilitating gear changing in mechanical gearboxes comprising a gear selector housing in which a gear selector shaft is rotatably and axially displaceably mounted, said gear selector shaft being displaced axially during a selecting step to a preselected engagement position and during an engaging or disengaging step is caused to turn for engaging or disengaging the appropriate gear by means of at least one gear selector or the like attached to the gear selector shaft, at least one control valve arranged in the gear changing mechanism being activated during the initial phase of the engaging or disengaging movement and triggering the actuation of a pressurized-medium operated servo cylinder which, with anchorage in a fixed bracket and with connection to a lever or the like on the shaft, is disposed for carrying out gear changing operation to a major extent.

#In manually operable gearboxes it is customary to transfer movements from a manual gear change lever to the actual gear change means with the help of a ball joint-mounted gear change rod. In this connection it is also known to equip the gear changing apparatus so that the gear change rod can describe a limited relative free movement during a gear changing step, a control valve in the gear change rod system being activated to trigger the actuation of an operating cylinder which acts to provide an auxiliary force during the continued gear changing operation. Such a gear change rod system implemented by an auxiliary force is based on an axial play in the gear change rod or in its end points. The system is particularly referable to gearboxes in which the gear selection positions are provided by turning a gear selector shaft and engaging the gears by a push or pull action of the same shaft with support by auxiliary force from the operating cylinder.

#A prerequisite of known systems is thus the use of a gear change rod between a gear change lever and a gear selector mechanism, which reduces the field of use of the system.

#The invention is further distinguished by the control valve for connecting auxiliary force being integrated in or in conjunction with a lever attached to the gear selector shaft with a play which is limited in both turning directions. This results in that the inventive apparatus comprises comparatively simple components which can be easily installed in a vehicle without any great amount of space. Other distinguishing features of the invention are apparent from the accompanying patent claims and the following description, which is made with reference to the accompanying drawings, on which

#FIG. 1 is a perspective view schematically showing an inventive gear changing apparatus,

#FIG. 2 is a longitudinal section of a gear selector shaft with selector means which are a part of the gear changing apparatus,

#The gear changing apparatus for a vehicle shown in FIGS. 1 and 2 is manually operable by means of a gear change lever 1. The latter is formed with a spherical portion 1a, by means of which the gear change lever 1 is pivotally mounted between two spherical bearing halves 2, one upper and one lower, mounted in a fixed bearing housing 13a. The bearing housing 13a constitutes a portion of a fixed bracket 13 attached by four screwed connections 19 to a gear selector housing 16, which in turn is fixed to the vehicle gearbox (not shown). The lower bearing half 2 abuts against a bottom of the bearing housing 13a, and a stop washer 14 is clamped into the bearing housing 13a above the upper bearing half 2. The bottom of the bearing housing 13a as well as the stop washer 14 are provided with holes for the passage of the gear change lever 1. The bearing halves 2 are formed with spherical seatings surrounding the ball portion 1a, allowing the gear change lever 1 multidirectional turning movements. For the limitation thereof, a radial groove 1c is made in the spherical portion 1a of the gear change lever 1, a guide pin 15 mounted in the bearing housing 13a from the inside engaging in said radial groove. Such guidance prevents the gear change lever 1 from being turned about its longitudinal axis, and also substantially limits the pivoting movements of the gear change lever 1 to two mutually perpendicular planes.

#The lower end of the gear change lever 1 is also formed with a ball portion 1b, adapted for engagement in a bearing orifice in the lower end 3a of a transfer arm or lever 3 attached to a gear selector shaft 4. Said shaft is rotatably and axially displaceably mounted in the gear selector housing 16 with the aid of two bushings 18. For sealing, a seal 17 engaging against the gear selector shaft 4 is mounted in either end of the gear selector housing 16. A gear selector 5, a so-called selector finger, is attached to the gear selector shaft 4 on the inside of the gear selector housing 16, and outside the gear selector housing 16 a servo-actuated lever 6 is also attached to the gear selector shaft 4. The servo-actuated lever 6 is arranged for coaction with a force-amplifying means 7, known per se, for executing mechanical movements. In the exemplified embodiment, the so-called servo means 7 consists of an operating cylinder comprising at least one pressure-transmitting element (not shown) which, under the action of a pressurized medium, acts on the strokes of an out-going shaft 7b. The servo means 7 can be operated either by a hydraulic or a pneumatic pressurized medium. In FIG. 1 there is illustrated a pneumatically operated servo means 7 comprising a double-acting compressed-air cylinder pivotally attached to the cover of the gearbox via a fixed lug 7a at its one end. A fork 8 is attached to the outer end of the shaft 7b projecting out of the cylinder, the outgoing shaft 7b being pivotally attached to the lower end of said servo-actuated lever 6 by means of said fork 8.

#The cylinder of the servo means 7 is supplied with pressurized medium by one of two pipes 10,11 under the action of a control valve function arranged in the lever 3. In response thereto the servo means 7 can act on the turning movements of the gear selector shaft 4 in either direction with pulling or pushing stroke movements.