GB2067250A

GB2067250A - Change speed gear

Info

Publication number: GB2067250A
Application number: GB8100684A
Authority: GB
Original assignee: Deere and Co
Current assignee: Deere and Co
Priority date: 1980-01-11
Filing date: 1981-01-09
Publication date: 1981-07-22
Also published as: CA1152357A; IT8147512A0; DE3048770C2; FI804066L; IT1142252B; FR2473664B1; JPS56101444A; SE441771B; SE8100105L; GB2067250B; FI69193C; JPH0155340B2; FI69193B; FR2473664A1; DE3048770A1

Abstract

An input shaft 19, 21 carries high speed range and low speed range input gears 27 and 25 and a reverse gear 43. A forward synchronized clutch 29 can selectively couple either of the gears 25 and 27 to the input shaft. A non-synchronized reverse clutch 45 can couple the reverse gear 43 to the input shaft. The gears on the input shaft are in constant mesh with gears on a counter-shaft 55, via gears on a reverse counter-shaft in the case of the reverse gear 43. Gears on the counter-shaft are also in constant mesh with gears on a gear shaft 65 provided with clutches 85 and 87 for selecting three speeds in either speed range. A gear 73 fixed on the gear shaft 65 is in constant mesh through a gear 75 with a gear 81 fixed on the output shaft 83. When the vehicle is stopped and reverse is to be engaged the reverse gear 43 is stopped because one of the clutches 85 and 87 will already be engaged while the input shaft still rotates because of drag through the main clutch. Gear clashing is nevertheless avoided because the selector mechanism for the clutches 29 and 45 is arranged, in going from neutral to reverse, momentarily to engage the clutch 29 with the gear 27 (which is also stopped) before engaging the clutch 45, whereby the input shaft is stopped before the reverse clutch is engaged. <IMAGE>

Description

SPECIFICATION Change speed gear This invention relates to a change speed gear for vehicle transmissions, particularly a transmission of the multi-range, multi-speed type commonly used in large off-road vehicles.

Current mutli-range transmissions used on large off-road vehicles utilize a high/low synchronizer for gear shifting. However, reverse gear is engaged using a conventional nonsynchronized gear clutch because of space and cost considerations. When the main clutch is disengaged, the main clutch being the means of transmissing torque to the transmission from the vehicle engine, drag causes the input shaft to experience a continued torque which in turn causes the reverse gear and reverse clutch to rotate out of synchronization, because customarily, prior to shifting the vehicle transmission to a reverse gear, the vehicle will be stopped resulting in the output shaft and the reverse gear being stopped.Therefore, upon engaging the non-synchronised reverse clutch for the reverse gear, clashing between the clutch and the reverse gear results, especially when the vehicle engine is running at a high R.P.M.

Although it has been proposed to provide the reverse gear with a synchronised clutch, the object of this invention is to provide a means of stopping the reverse gear from clashing when shifting the transmission from neutral to reverse, without going to such expense.

The invention is defined below in claim 1.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a fragmentary elevational view, partly in section, illustrating a transmission.

Fig. 2 is a fragmentary elevational view, partly in section, of the transmission reverse countershaft.

Fig. 3 is a fragmentary elevational view, partly in section of the transmission and shifting means.

Fig. 4 is an elevated view of a shifting cam.

Fig. 1 shows the parallel shaft portion of a multi-range transmission representative of the type used on off-road vehicles. A transmission housing 11 includes forward and rear walls 1 3 and 1 5 respectively. Rotatably mounted through the forward wall 13 and an inner wall 17 is an input shaft 19. The input shaft 19 is splined to an input feed shaft 21 at 23. Conventionally, the input feed shaft 21 is connected to a main clutch to receive torque from an engine. It is sometimes the practice to drive the input feed shaft 21 through a planetary gear section to increase the range capability of the transmission.

Carried on the input shaft 1 9 is a low range (or low speed) input pinion gear 25, and a high range (or high speed) input pinion gear 27. For the purpose of selectively establishing either a low or high range positive engagement between the input shaft 19 and the pinions 25 and 27, the transmission includes a dual speed or range selector clutch 29 located between the input pinions 25 and 27. The dual range clutch 29 includes a pair of synchronizer rings 31 located at opposite sides of the synchronizer member 33, the latter being splined to a hub 35 at 37. One of the synchronizer rings 31 is splined at 39 to the input pinion 25 while the other synchronizer ring 31 is splined at 41 to the input pinion 27.When the synchronizer rings 31 are shifted in the direction of an arrow L, synchronization occurs between the rear ring 31 and the synchronizer member 33, after which the splined connection at 39 is carried over the spline 37 on the hub 35. Thus, the hub 35, the low range pinion 25 and the rear synchronizing ring 31 are connected for the rotation in unison. This positively connects the low range pinion 25 to the input shaft 19. Shifting the synchronizer ring 31 in the opposite direction, in the direction of an arrow H, first synchronizes the first ring 31 and the synchronizer member 33 and causes positive engagement between the high-range pinion 37 and input shaft hub 35 by carrying over the splined connection at 41 to the hub splines 37.

Also, carried on the input shaft 19 is a reverse pinion gear 43. A reverse clutch 45 is located on the input shaft 1 9 between the low speed input pinion 25 and the reverse pinion 43. The reverse clutch 45 includes an internal ring 47 keyed to the shaft 1 9. An external ring 49 is axially shiftably splined at 51 to the interior ring 47 and is shiftable in the direction of the arrow R to engage teeth 53 located on the hub of the reverse pinion 43.

A main countershaft 55 is rotatably mounted in the walls 13 and 17. The countershaft 55 is shown displaced from its true position in order that the structure thereof may be more readily perceived. The main countershaft 55 carries a small countershaft gear 57, a large countershaft gear 59, a first intermediate countershaft gear 61, and a second intermediate countershaft gear 63, the gear 61 being smaller than the gear 63. The countershaft gear 59 is in constant mesh with the low range pinion 25, and the countershaft gear 63 is in constant mesh with the high-range pinion 27.

A gear shaft 65 is rotatably mounted in the walls 13 and 17. The gear shaft 65 has journalled thereon a large gear 67, a small gear 69, and an intermediate gear 71, these gears being respectively in constant mesh with the countershaft gears 57, 59, and 61. The gear shaft 65 also has an output gear 73 in constant mesh with a gear 75 fixed by any conventional means to a shaft 77 rotatably mounted between the wall 1 7 and another interior wall 79, the gear 75 being in constant mesh with a gear 81 fixed by any conventional means to a output shaft 83 rotatably mounted between the walls 1 7 and 79.For selectively establishing a positive engagement between the gears 67, 69, 71, and the gear shaft 65, the gear shaft 65 carries first and second clutches 85 and 87, which are of similar construction to the reverse clutch 45. Specifically, the clutches 85 and 87 include an interior ring 89 keyed to the gear shafts 65 at 91 and 92 respectively. An external ring 93 of clutch 85 is axially slidably splined to the interior ring 89. The external ring 93 is shiftable in the direction of the arrow A to bring the internal splines thereof into driving engagement with teeth 95 of the gear 67.

If the exterior ring 93 is shifted to the direction of the arrow D the external ring 93 will drivingly engage teeth 97 of gear 69. Similarly, an external ring 99 is axially shiftably splined to the internal ring 89 of clutch 87 and when shifted in the direction of arrow C will engage teeth 101 to drivably engage gear 71.

Referring to Fig. 2, a reverse countershaft 103 is rotatably mounted between the wall 17 and an internal wall 105, parallel to and behind the input shaft 1 9. The countershaft 103 carries first and second gears 107 and 109. The first gear 107 is in constant mesh with the reverse gear 43 on the input shaft 1 9 and the second gear 109 is in constant mesh with the gear 59 on the main countershaft 55.

Forward gear selection is attained in the conventional manner well known in the art. By way of illustration, first gear is obtained by sliding external ring 93 in the direction of arrow A to engage teeth 95 of gear 67 and shifting synchronizer 29 in the direction of arrow L, second gear being obtained by shifting synchronizer 29 in the direction of arrow H. It is observed that gear 67 represents first and second gears; gear 71 represents a third and fourth gear:and gear 69 represents a fifth and sixth gear.

When a vehicle carrying the transmission is stopped, the output shaft 83 will be stopped, thereby bringing the gear shaft 65 to a stop because of the coupling between gears 73, 75 and 81. The input shaft 19, even with the main clutch disconnected, will have a draft effect produced from the engine so that the input shaft 19 remains rotating when the engine is idling. It is customary to have either gear 67, 69 or 71 coupled to the shaft 65 prior to shifting to reverse; therefore the main countershaft 55 will be stopped. Therefore, motion between gears 59, 109, and 107, and reverse gear 43 is stopped.Because the input shaft 1 9 experiences a degree of rotation, drag forces will cause the reverse clutch 45 to rotate so that direct shifting of the reverse clutch 45 in the direction of arrow R to enage the teeth 53 will produce clashing between the reverse gear teeth 53 and the reverse clutch 45. To eliminate clashing, shifting the synchronizer 29 in either the direction of arrows H or L will cause the input shaft 19 to slow down by creating a positive communication between the input shaft 1 9 and the stopped shaft 55. Once the input shaft 1 9 has been stopped, the reverse clutch 45 can be shifted without clashing.

Referring to Fig. 3, the transmission further includes a shift cynchronizer clutch collar 108 having a linking arm 110. The collar is placed around the synchronizer clutch 29. A shift collar 111 having a linking arm 113 is placed around the clutch 45. A shift rod 11 5 is passed through holes in the linking arms 110 and 113 and fixed in the transmission by any conventional means parallel to the input shaft 19 such that collars 107 and 109 can slidably move thereon. Third and fourth shift collars 117 and 119, similar to the shift collar 111, are slidably mounted on a second shift rod 121 fixed in the transmission by any conventional means parallel to the gear shaft 65, the shift collar 11 7 being placed around the clutch 85 and the shift collar 11 9 being placed around the clutch 87.

Referring further to Fig. 3, and more particularly to Fig. 4, a first cam 123 is rotatably mounted in the transmission at 124. The cam 123 has a first groove or cam track 125 in which a track rider 137 of the linking arm 110 can slidably move and a second groove or cam track 127 in which the track rider 135 of the linking arm 113 can slidably move. The contour of the cam tracks 125 and 127 defines the clutching action of clutches 29 and 45 upon rotation of the cam 123. Similarly, a cam 131 controls the clutching action of the clutches 85 and 86.

Referring to Fig. 4, tracks 125 and 127 of cam 123 are contoured to define a track for the clutch riders 1 35 and 1 37 to achieve the desired reverse clutching without clashing. The intersection of track 125 and 127 with line 1-1 indicates the location of the riders 1 35 and 1 37 respectively, to place the transmission in reverse; the intersection of tracks 125 and 127 with line 5-5 indicates the location of the riders 135 and 137, respectively, to engage the low gear pinion 25 to shaft 19, the reverse clutch 45 being disengaged; and the intersection of tracks 125 and 127 with line 9-9 indicates the location of the followers 135 and 137 respectively, to engage the high gear pinion 27 to the shaft 19, the clutch 45 being disengaged. The intersection of tracks 125 and 127 with lines 3-3 and 7-7 indicate a neutral transmission mide. The course of cam track 125 experiences a lateral deformation at 1 33 of sufficient magnitude to cause the clutch collar 108 to shift the high/low synchronizer clutch 26 to momentarily engage and disengage the high gear 29 just prior to engaging the reverse clutch 111, thereby, deriving the aforedescribed clutching action to eliminate reverse gear clashing.

Claims

1. A change speed gear comprising an input shaft on which are journalled an input gear and a reverse gear, a synchronized forward clutch for coupling the input gear to the input shaft, a nonsynchronised reverse clutch for coupling the reverse gear to the input shaft, a gear shaft on which are journalled a plurality of speed-selection gears, clutch means for selectively coupling these gears to the gear shaft, a main countershaft with gears which provide constant mesh coupling between the input gear and the speed-selection gears and, via a reverse countershaft, between the reverse gear and the speed-selection gears, and a selector mechanism movable between neutral, forward and reverse positions to control the forward and reverse clutches and so constructed as, when moved from neutral to reverse, to engage and disengage the forward clutch prior to engaging the reverse clutch.

2. A change speed gear according to claim 1, wherein there are two input gears journalled on the input shaft and in mesh with countershaft gears for providing high and low speed ranges, the forward clutch being operable to couple either input gear to the input shaft and the selector mechanism so controlling the forward clutch as engage and disengage the forward clutch with a predetermined one of the input gears when moved from neutral to reverse, prior to engaging the reverse clutch.

3. A change speed gear according to claim 1 or 2, wherein the selector mechanism comprises a rotatable sector with cam tracks in which there engage follows connected to shift collars of the forward and reverse clutches, the sector having positions defining reverse gear and an adjacent neutral gear and the cam track pertaining to the forward clutch having a kink between these positions for effecting the engagement and disengagement of the forward clutch prior to engaging the reverse clutch.

4. A change speed gear substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.