System for shifting gears
The present invention relates to a system for shifting gears according to the introduction to the independent patent claims in the set of claims.
The invention will preferably be employed in vehicles of different types, but may also be applied within other technical fields where it is desirable to undertake a shift between different gear ratios. Other vehicles such as ships, small boats etc. may be briefly mentioned here.
In conventional gearshift systems currently on offer, gearboxes with several shift shafts are often employed. According to established technology each shift shaft is provided with a shift fork, each of which is connected to a shift sleeve in order to perform a gearshift. The shift fork together with its shift sleeve may be moved between different positions for shifting between different gear ratios and possibly the neutral position. When a gear is selected by means of the gear lever or by automatic gear selection, the shift shaft connected with the desired gear ratio is engaged. The shift shaft is then moved in its longitudinal direction for shifting to a new gear ratio.
Since several shift shafts are presumably included in the gearbox, the gearbox will be relatively large and require a great deal of space, its construction will be relatively complex and the gearbox will be expensive. This applies particularly in cases where gearbox solutions have many gears, for example where the gearbox has six different gear ratios in addition to reverse gear. In this case the gearbox may contain as many as four different shift shafts; a shift fork for each gear pair together with a shift fork for reverse gear. Such a gearbox requires a lot of space and in addition has an extensive construction with many different parts that have to fit together and be moved relative to one another.
A starting point for making the gearbox simpler and smaller is to reduce the number of components by using only one shift shaft in the gearbox. The principle of using a shift shaft is per se previously known. We refer here to DE 19901056, WO 9516869, EP 0131720, US 6389919, US 3929029 in addition to earlier Swedish patent applications filed by the same applicant.
By employing only one shift shaft, it must be ensured that the shift forks are mounted on the shift shaft in such a manner that only the shift fork that has to effect a shift to a new gear ratio follows the shift shaft when the shifting movement is to be performed. This can be solved in many different ways, one possibility being to employ a principle where a shift fork is selected and locked to the shift shaft by means of a rotation of the shift shaft. The remaining shift forks are kept unlocked, with the result that when the shift movement is to be performed, a gear shift is undertaken by means of the selected, locked shift fork.
It is an object of the present invention to provide a solution in which forces applied for selection of a shift fork do not influence the shift shaft in its direction of travel. In that respect it is an object of the invention to provide a solution principle where the forces acting on the shift shaft on selection of a shift fork act perpendicularly to the forces acting on the shift shaft when it has to be moved in order to change gear.
It is a further object of the present invention to provide a solution wherein the friction operating between the shift shaft and the shift forks is minimised. Furthermore, it is desirable to obtain a system that is easy and inexpensive to manufacture. The objects of the invention are achieved according to the invention as indicated in the characteristics of the independent patent claims, further embodiments of the invention being indicated in the dependent patent claims.
The invention according to patent claim 1 relates to a system for shifting gears, employing a gearbox provided with a shift shaft, which is equipped with at least two shift forks. One of the shift forks is selected for locking to the shift shaft, while the remaining shift forks are kept unlocked relative to the shift shaft. Subsequent movement of the shift shaft with the locked connecting structure results in a shift of gear ratio. The system is characterised in that it further comprises a selector shaft that is movable between different positions in the selector shaft's direction of travel. The selector shaft's position determines which shift fork is to be locked to the shaft.
The selector shaft is preferably movable between different positions in its longitudinal direction. Furthermore, the selector shaft's direction of travel is preferably positioned perpendicularly to the shift shaft's direction of travel. This arrangement of the selector shaft ensures that the forces acting on the shift forks are applied in a direction on the shift shaft which is preferably perpendicular to the direction of the forces acting on the shift shaft in order to effect a shift to a new gear ratio. The selector shaft's direction of travel relative to the shift shaft may.of course also be oriented in a manner other than perpendicularly to the shift shaft if so desired. The number of positions between which the selector shaft can be moved is dependent on the number of shift forks with which the shift shaft is equipped. In an embodiment of the system, two shift forks are included in the system. In this case the selector shaft is provided so as to be movable between a first position where one shift fork is locked to the shift shaft and a second position where the second shift fork is locked to the shift shaft. In addition, the selector shaft can be moved to a third position where one of the two shift forks is locked to the shift shaft, and where in addition the system is arranged so that it is possible to move the shift fork to reverse gear.
The system further comprises a guide shaft, which is connected to the selector shaft, where the guide shaft is equipped with locking devices which, depending on the selector shaft's position, effect locking of the shift fork concerned and unlocking of the remaining shift fork(s) relative to the shift shaft. The guide shaft will preferably be provided with a number of locking devices corresponding to the number of shift forks. The locking devices may be comprised of different devices and arrangements that are capable of transferring and/or converting the selector shaft's movement to locking of the individual shift fork. According to a preferred embodiment of the invention the individual locking device comprises an arm, one end of which is attached to the guide shaft, preferably in such a manner that the arm can be moved along the guide shaft. At the other end of the arm a locking pin is mounted, which is used for locking the shift fork to the shift shaft.
The shift shaft is provided with a locking area for each shift fork. The individual locking area is positioned inside a through-going bore that is provided in each of the shift forks. Moreover, each shift fork and the associated locking area are provided with openings that are arranged to receive a locking pin. The openings in the individual shift fork and the locking area are preferably positioned perpendicularly to the through-going bore. When the shift fork is in an unlocked state, the locking pin is located in the shift fork's opening. When the shift fork is in a locked state, the locking pin is moved to be housed both in the shift fork's opening and in the shift shaft's opening.
The locking device's arms are preferably designed so as to enable the locking pins to be inserted in the openings in the shift fork and the shift shaft in a direction that is perpendicular to the shift shaft's direction of travel, in accordance with the object of the invention. In a further embodiment of the system the guide shaft and the selector shaft are positioned at a distance from the shift shaft preferably above the shift shaft. The arms will then assume a curved shape, thus enabling the locking pins to be inserted perpendicularly to the shift shaft's direction of travel. In yet another embodiment the guide shaft, is attached perpendicularly to the selector shaft, advantageously at the centre of the guide shaft and preferably in such a manner that the guide shaft and the selector shaft form a cross. The guide shaft can then be positioned parallel to the shift shaft. It will also be possible to join the guide shaft and the selector shaft in another way. The guide shaft can be divided into two parts, each of which is attached to the selector shaft, for example the guide shaft's parts can be mounted at a level under the selector shaft. In a version of this latter embodiment, it will be necessary to equip the guide shaft with arms since the position of the guide shaft's parts ensures that the locking pins are moved directly
in towards the shift shaft in a direction that is perpendicular to the shift shaft's direction of travel.
In an embodiment of the system an additional locking part is also included for each shift fork. This ensures that the unlocked shift fork(s) are locked to the gearbox housing in order to prevent the unlocked shift fork(s) from moving when the shift shaft is moved. When the shift fork is in a locked state, the additional locking part permits the locked shift fork to be moved relative to the additional locking part. This can be achieved by a repositioning of the additional locking part relative to the locked shift fork, preferably by the additional locking part being moved by means of the shift fork's locking pin. The shift fork, moreover, is so designed that interaction between it and the additional locking part prevents the shift fork from moving out of position if a gear is selected, or out of neutral position.
The openings in the individual shift fork and the associated locking area of the shift shaft will be designed to be through-going. The additional locking part may be mounted in an additional opening, which is positioned so that when the shift fork is in an unlocked state, the additional locking part is located partly housed in its additional opening and in the shift fork's opening. When the shift fork has to be locked, the locking pin is moved to a position where it is housed both in the openings in the shift fork and the shift shaft's locking area. When the locked shift fork is moved in order to change gear, this causes the additional locking part to be housed in one of several grooves provided in the shift fork. The individual shift fork will preferably be provided with two grooves, one on each side of the shift fork's opening.
One of the shift forks may be provided with a reverse block, preferably by the level of one groove being displaced relative to the second groove.
In a further embodiment relating to interaction between the individual shift fork and the associated additional locking part, the first end of the locking pin is housed in the shift fork's opening on one side of the shift fork's bore and the additional locking part is partly housed in the shift fork's opening on the other side of the shift fork's bore, when the shift fork is in an unlocked state. When the shift fork is in a locked state, the locking pin is housed in the locking area's opening and in the shift fork's opening on both sides of the shift fork's bore. This position of the locking pin results in a displacement of the additional locking part in the shift fork's opening or out of the shift fork's opening. The additional locking part will preferably comprise a roller device that is attached to a first end of a piston. The other end of the piston is attached to a spring which in turn is attached to a wall portion in the additional opening. The additional opening is provided, for example, in the gearbox housing.
In yet another preferred embodiment of the invention it has been found to be necessary to provide additional locking means for ensuring that the shift fork(s) that are unlocked do not follow when the shift shaft is moved. This can be solved in various ways; an advantageous solution that may be mentioned here is where the gearbox housing or another suitable structure is provided with openings, each for receiving the second end of each locking pin. When the shift fork is in an unlocked state, the second end of the locking pin is moved to be housed in this opening, thereby ensuring that the shift fork remains at rest when the shift shaft is moved. When the shift fork is in an unlocked state, the second end of the locking pin is located outside this opening and the shift fork is therefore free to follow the movement of the shift shaft.
In one embodiment of the system for controlling the selector shaft's position, the determination of the selector shaft's position is associated with positioning of a gear lever employed for operating the gearbox. This embodiment may preferably be implemented by placing the gear lever in predetermined positions along a first direction of travel. These predetermined positions determine the selector shaft's position, and thereby which shift fork has to be locked to the shift shaft and which have to be released from the shift shaft.
By movement in a first direction here we mean that the gear lever is movable forwards and backwards between different positions in a gear path pattern comprising a first direction of travel where the desired gear gate is selected, the relevant shift fork thereby also being selected for locking to the shift shaft. The gear lever, moreover, is movable in a second direction of travel where shifting between the different gear ratios is undertaken. Movement of the gear lever in the second direction of travel therefore results in movement of the shift shaft with the shift fork and subsequent shifting to a new gear ratio.
When a gear lever is employed for operating the gearbox, the gear lever can be directly connected to the selector shaft by a transmission, for example in the form of a cable, rod or fluid actuator that arranges for the gear lever's movements and changes in position to be transmitted to the selector shaft by means of a lever and guide fork or lever with a toothed rack. The transmission may also be implemented by signal transmission.
As an alternative to a gear lever, a switch or push-button solution may also be employed as a gear operating device. Furthermore, a computer may be used for communication between the gear operating device and the selector shaft, and it is also possible for the gear operating device to be moved to positions where gear selection and gear shift are automatic.
As an alternative to manually operated gear operating devices, according to an embodiment of the invention a wholly automatic solution may be employed. In this
case the solution is provided by means of a data processing unit, which selects the appropriate gear ratio on the basis of incoming parameters and controls the selector shaft. The selected gear ratio can be communicated directly to the selector shaft and/or a control unit, which controls repositioning of the selector shaft. Where the gear operating device, i.e. the gear lever or push-button solution, is not directly attached to the selector shaft, it may be connected to a suitable actuator that receives a signal from the gear operating device or possibly the computer concerning the magnitude of the shift that has to be undertaken.
An embodiment of the system will now be described with reference to the attached drawings, in which
Figure 1 is a plan view from above of an arrangement for locking shift forks to a shift shaft.
Figure 2 is a plan view from above of an arrangement for effecting locking of the individual shift fork to the shift shaft. Figure 3 is a plan view from above of the assembly of the arrangements illustrated in figure 1 and figure 2. •
Figure 4 illustrates a practical embodiment of the system illustrated in figure 3.
The two shift forks 16 and 17 illustrated in figure 1 can be alternately locked to a shift shaft 15. In figure 1 the shift fork 16 is shown locked to the shift shaft 15, while the shift fork 17 is unlocked relative to the shift shaft 15. When shift fork 16 is locked to the shift shaft 15, a shift into reverse or first gear can be undertaken by the shift shaft being moved forwards or backwards in its longitudinal direction. The same applies for locking shift fork 17 to shift shaft 15, where shifting to second or third gear is undertaken by movement of the shift shaft forwards or backwards in its longitudinal direction.
In figure 1 the shift forks 16, 17 are shown provided with through-going bores 16a, 17 a, through which a shift shaft 15 is passed. The shift forks are provided with through- going openings 16b, 17b, which are shown oriented substantially perpendicularly to the through-going bores 16a, 17a. Furthermore, the shift shaft is provided with a locking area for each shift fork that is positioned inside the bores 16a, 17a. For each of the shift forks 16, 17 there is provided a respective through- going opening 15a, 15b in the shift shaft 15, with the result that the openings 16b, 17b are aligned with the openings 15a, 15b in the shift shaft. A locking pin 8 is shown positioned in the opening 17b on one side of the bore 17a. On the other side of the bore 17a is located an additional locking part, comprising amongst other things a roller device 27, which is partly housed in the opening 17b.
The roller device 27 is attached to the end of a piston 25, which is mounted by means of a spring 22 in an additional opening 21a provided in an element 21. The element 21 is affixed to the gearbox housing. With the roller device 27 partly housed in the opening 17b and in the additional opening 21a, the object is thereby achieved that the shift fork 17 is locked to the gearbox housing 30.
When the shift shaft 15 is moved for shifting the gear ratio, it is secured so that only the shift fork 16 accompanies the shift shaft 15, while the shift fork 17 remains at rest relative to the shift shaft. The shift fork 16 is locked to the shift shaft 15 by the locking pin 7 being moved on from its position in the opening 16b on one side of the bore 16a to be accommodated in the shift shaft's opening 15a, from where it continues until it is housed in the opening 16b on the other side of the bore 16a. The locking pin 7 then assumes the position illustrated in figure 1. This movement of the locking pin 7 causes the roller device 26 to be inserted in the opening 16b, slightly further away from the bore 16a. This causes the piston 24 to be moved in the additional opening and the spring 22 to be slightly compressed. The object is thereby achieved that the roller device 26 is moved from a position in which it locks the shift fork to the gearbox housing corresponding to that illustrated for shift fork 17, to a position in which the shift fork 16 can be moved together with the shift shaft 15 in order to effect a gear shift. Two grooves 14a, 14b are shown provided on the shift fork 16 for receiving the roller device 26 when a gear shift is to be undertaken. When a shift to first gear has to be performed, the shift shaft 15 with the shift fork 16 are moved to the left in figure 1, whereby the groove 14b is also moved to the left and the roller device 26 is moved to be housed in the groove 14b by the spring 22. Shifting to reverse gear requires the locking pin 7 to be moved further inwards in the opening 16b in the direction of the additional opening 20a, until the roller device 26 is housed in the additional opening 20a: When the roller device 26 has been moved into this position, the shift shaft 15 with shift fork 16 can be moved to the right in the figure, thus causing the roller device 26 to be housed in the groove 14a. Placing the additional locking parts in the shift forks' grooves provides security for the system, since an extra force has to be applied in order to move the shift fork out of the selected gear. Furthermore, the level difference produced by groove 14a being displaced relative to groove 14b is employed as a reverse block, since it prevents the driver from inadvertently putting the car in reverse, but in fact he has to perform an action such as moving the gear lever to another position in order to enable the locking pin 7 to be further inserted in the direction of the additional opening 20a.
When the shift fork 17 is locked to the shift shaft 15, the locking pin 8 will be employed for locking in the same way as described above in connection with locking of shift fork 16 to the shift shaft. The shift fork 17 is provided with grooves
13a and 13b for receiving the roller device 27 when shifting to second and third gear respectively. It can be seen in figure 1 that the grooves 13a, 13b are located on the same level. When the locking pin 8 has to lock the shift fork 17 to the shift shaft 15, the locking pin pushes the roller device 27 so that it is housed in the additional opening 21a. The shift fork 17 is then released from being locked to the gearbox housing and can be moved with the shift shaft 15 to the right for shifting to second gear and to the left for shifting to third gear.
Figure 2 illustrates an arrangement for effecting locking and unlocking of the shift forks by means of the locking pins 7, 8. A selector shaft 2 and a guide shaft 1 are mounted together at the centre of the guide shaft, thus forming a substantially right angle between the two shafts.
The selector shaft 2 is mounted in the housing with bearings 3. At one end of the selector shaft 2 it is coupled to a connector 4 for transmitting, for example, the gear lever's movement for selection of shift fork 16 or 17. The gear lever's movement can be transmitted by means of a cable, rod, fluid actuator, lever and guide fork, or lever with toothed rack or the like. Control of the selector shaft may also be implemented by other means than by movement of the gear lever, as has also been mentioned earlier. It may, for example, be controlled by switches in the driver's cabin or by a computer-controlled actuator. The guide shaft 1 and the selector shaft 2 are located at a distance from the shift shaft, preferably above the shift shaft as can be seen in figure 3. Figure 3 shows that the guide shaft 1 is positioned substantially parallel to the shift shaft 15. On the guide shaft 1 are mounted two arms 5, 6, each of which can be moved preferably slidingly along each end of the guide shaft 1 via a bore provided in the arms 5, 6. The locking pins 7, 8 are attached to the end of the anus 5, 6. Each of these arms 5, 6 is designed so as to permit the first end of each of the locking pins 7, 8 to be moved into locking position by means of a force that has a direction that is substantially perpendicular to the direction of the force acting on the shift shaft 15. In figures 2 and 3 the arms 5, 6 are shown in curved form, extending from the level on which the selector shaft 2 and the guide shaft 1 are located to the level on which the shift shaft 15 and the shift forks 7, 8 are located.
According to the embodiment illustrated in figures 1-3, the selector shaft 2 is provided in such a manner that when the selector shaft 2 is moved forwards and backwards in its longitudinal direction across the shift shaft, it can be moved between different positions. In figure 3 the selector shaft 2 is depicted moved to a first position where the shift fork 16 is locked to the shift shaft 15 by the first end 7a of the locking pin 7 being inserted through the opening 15a in the shift shaft 15. By means of this movement of the selector shaft 2, the object is simultaneously achieved that the shift fork 17 is unlocked from the shift shaft 15 by the first end 8a
of the second locking pin 8 being moved out of the opening 15b into a rest position in the shift fork's 17 opening 17b. In the same way shift fork 17 will be locked to shift shaft 15 and shift fork 16 will be released from shift shaft 15 when the selector shaft 2 is moved to a second position, for example by the selector shaft 2 being moved in the other direction.
When a gear is engaged by the shift shaft 15 being moved in the longitudinal direction, the arm 5 or 6 that is locked to the shift fork via the locking pin 7 or 8 will be able to accompany the shift fork 16 or 17 by the arm 5 or 6 sliding along the guide shaft 1. It can be seen in figure 3 that the gearbox housing, illustrated here by structure 30, is provided with openings 31. The second end 8b of the locking pin 8 is moved to be housed in this opening 31, thereby ensuring that the shift fork 17 remains at rest on movement of the shift shaft 15. The second end 7b of the locking pin 7 is located outside the opening 31 and the shift fork 16 is thereby free to follow the shift shaft's movement.
Figure 4 illustrates a practical embodiment of the system illustrated in figure 3. It can be seen from figure 4 that the guide shaft 1 is attached to the end of the selector shaft 2, and that the selector shaft is located at a level above the guide shaft 1. Otherwise the same figure references are employed in figure 4 as in figure 3.