Machine element or mechanism – Control lever and linkage systems – Multiple controlled elements
Reexamination Certificate
1999-08-05
2001-02-20
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlled elements
C074S473370
Reexamination Certificate
active
06189402
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a manual transmission with a driver-operated gearshift-lever mechanism, which are used in automobiles, construction machine vehicles, earthmoving equipment vehicles and the like.
BACKGROUND ART
Most manual transmissions are composed of low-speed gears having a spline clutch connected to the gears against rotation, high-speed gears having a spline clutch connected to the gears against rotation, and a clutch hub interposed between the low-speed gears and the high-speed gears and connected an output shaft against rotation. A spline sleeve is fitted on the clutch hub for axially sliding movement. On actual speed changing, the spline sleeve fitted with the clutch hub rotatable with the output shaft is moved axially into spline engagement with either one of the low-speed gears and the high-speed gears, thereby selecting a transmission ratio in accordance with the gear ratios of the low and high gears so as to obtain the power transmission at the selected transmission ratio.
A selector mechanism of such manual transmissions as described above is of the multi-rod gear selector type in which there may be shift arms, one to each spline sleeve, and selector rods are each provided for each of the shift arms to support the shift arms and transmit the power. The shift arms are separately connected with the individual selector rods, one to each shift arm, by suitable fixing means such as bolts, spring pins, welding and the like. In the design, one shift arm and one selector rod are in combination employed for a transmission ratio between a pair of low and high gears and, therefore, the five-speed, one-reverse manual transmissions require three selector rods and also the six-speed, one-reverse manual transmissions require four selector rods. Japanese Utility Model Laid-Open No. 57819/1987 discloses an example of the multi-rod gear selector mechanism.
Another selector mechanism of the manual transmissions is of the single rod gear selector type, although being minor in use, in which all desired shift arms are arranged on a single selector rod in order to reduce the transmission in its weight, required space, the number of the parts and the like. In this design, all the shift arms except for a shift arm at a design location are arranged so as to slide on a single selector rod.
FIG. 3
is a top plan view illustrating an exemplary prior gearshift mechanism of the single rod gear selector type. The gearshift mechanism
60
in
FIG. 3
has low and high gear pairs for obtaining various speed ratios or transmission ratios. Further, there are provided selector rods extending over the overall length of a transmission case
74
, one to each gear pair. That is, for the six-speed, one reverse manual transmission illustrated, it is necessary to install four selector rods extending through the full length of the transmission case
74
, which are a first-speed, reverse selector rod
61
, a second-, third-speed selector rod
62
, a fourth-, fifth-speed selector rod
63
and a sixth-speed selector rod
64
. The first-speed, reverse selector rod
61
is connected to a first-speed, reverse shift arm
65
. Likewise, the second-, third-speed selector rod
62
, the fourth-, fifth-speed selector rod
63
and the sixth-speed selector rod
64
are connected to a second-, third-speed shift arm
66
, a fourth-, fifth-speed shift arm
67
and a sixth-speed shift arm
68
, respectively. Shift blocks
69
to
72
, each corresponding to each of the shift arms
65
to
68
, are assembled on the second-, third-speed selector rod
62
. There is provided engaging means operable in response to the manipulation of a shift lever, not shown, whether the engaging means is of a direct control type in which one end of the shift lever constitutes the engaging means or a remote control type in which the shift lever is operatively connected with the engaging means through wires or rods. Manipulating the shift lever thus causes the engaging means to make selective engagement with any one of the shift blocks
69
to
72
, resulting in shifting any one of the shift arms
65
to
68
, selected depending on the shift direction of the engaging means, so that any desired transmission range may be selected out of six-speeds and one reverse. On the gearshift mechanism of multi-rod gear selector type designed as described above, two or more selector rods occupy the space exceeding the area for the selector rods intrinsically indispensable for the transmission. This becomes a major problem exerting the great adverse influence upon the gearshift mechanism as to production cost, weight and the desired number of parts.
In contrast,
FIG. 4
is a side elevation showing an exemplary prior gearshift mechanism of single-rod gear selector type. The gearshift mechanism
80
in
FIG. 4
has a single selector rod
81
supported for sliding movement by the transmission case
74
and carrying thereon all shift arms
82
to
84
. Both the first-, second-speed shift arm
82
and third-, fourth-speed shift arm
83
are movable in a linearly sliding manner relatively of the selector rod
81
, whereas the fifth-speed shift arm
84
is fixed to the selector rod
82
. Shift block arrangement
85
is concentrated on a design location for selectively shifting the shift arms
82
to
84
. In the single rod gear selector type, the permissible spaces for each of the shift arms
82
to
84
become very small and, therefore, each shift arm is inevitably made slender although such an structure is less desirable because the shift arms become reduced in stiffness. In addition, the practical gearshift mechanism
80
makes no remarkable saving in the desired space for all the parts, including the shift arms
82
to
84
and the selector rod
81
, compared with the gearshift mechanism
60
of multi-rod gear selector type having four selector rods. Moreover, the need of a large number of forward speeds such as the six-speed, one reverse transmissions in recent years makes much more it difficult to assemble all shift arms on a single selector rod.
In the conventional gearshift mechanism of multi-rod gear selector type, the problem as described above arises that increased number of forward speeds increases the desired number of the selector rods. Moreover, the aggregation of the shift blocks on one location results in requiring such arrangement that the shift blocks for the shift arms corresponding to the outer opposing selector rods are to be formed on the extensions of the shift arms, which elongate beyond the inner selector rods. This causes the inevitable drawback in which the gearshift mechanism becomes greater in height so that it is hard to make it compact in size. In addition to the above, the shift blocks should be each assigned exclusively to each of the selector rods and, therefore, the parts necessary for gearshift in corresponding to the shift blocks have to be provided at every shift block. In contrast, on the prior gearshift mechanism of single rod gear selector type, the shift arms are limited in material to pressed iron alloys, cast iron alloys or the like, which is relatively higher in strength in order to avoid a deficiency in stiffness owing to the slender structure of the shift arms. Moreover, increased number of forward speed ranges causes such inconvenience that all shift arms may not be kept round a single selector rod. In recent years, accordingly, much attention has been given to a gearshift mechanism, which may contribute to make the transmissions compact in size, reduce the number of the desired parts and make available of inexpensive materials thereby being reduced in production cost.
The present invention has for its primary object to overcome the problems described above and in particular to provide a manual transmission having two selector rods, which design may reduce the desired number of selector rods by roughly half of the selector rods required in the multi-rod gear selector type while make it possible to improve the stiffness of the shift arms compared with the single rod gear selector type in whi
Browdy and Neimark
Fenstermacher David
Isuzu Motors Limited
LandOfFree
Gear transmission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gear transmission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gear transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2616181