Parallel shaft transmission

Details Parallel shaft transmission Parallel shaft transmission

2000-05-31

2001-12-25

Marmor, Charles A (Department: 3682)

Machine element or mechanism

Gearing

Interchangeably locked

Reexamination Certificate

active

06332371

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a parallel shaft transmission wherein a plurality of gear trains are disposed between shafts established parallel to each other, and each gear train has a plurality of clutching means for selecting the gear train to effect power transmission.
BACKGROUND OF THE INVENTION
Parallel shaft transmissions with such a constitution have had many uses such as in automobile transmissions. For example, parallel shaft automatic transmissions are disclosed in Japanese Patent Laid-open No. 57-103955(A) and Japanese Patent Laid-open No. 4-331852(A).
However, these parallel shaft transmissions have constitutions wherein a plurality of gear trains for engaging with each other are disposed parallel to the shafts and between the parallel shafts, and the gear train for effecting power transmission is selected by the connection and disconnection of a plurality of clutches disposed adjacent to the gears constituting each gear train. Therefore, the tendency is for the axial dimension of the transmission to increase; this tendency increases as the number of speeds increases. Particularly in automobile transmissions, the number of hydraulic clutches corresponds to the number of speeds, but hydraulic clutches structurally have relatively large axial and radial dimensions, and it is easy for the transmission to become large.
Also, in recent years, automobile transmissions have tended to have a greater number of speeds because of the demands for drivability and improvements in fuel consumption. Three speed transmissions changed to four speed transmissions; once five speed transmissions came into use, six speed transmissions were requested because of further demands for drivability and improvements in fuel consumption. This is consequently a situation where it is easy for transmissions to become larger and larger. Likewise, as the transmissions came to have larger numbers of speeds, the number of clutches increased and the increased size and weight of transmissions and consequent increases in manufacturing costs have become problematic.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a parallel shaft transmission having a constitution wherein the disposition of the gears and clutches is contrived so that the transmission can have an increased number of speeds and be as compact as possible.
The parallel shaft transmission relating to the present invention has the following constitution: an input shaft, first counter shaft, second counter shaft, and output shaft established on the same axis as the first counter shaft and able to rotate relatively thereto, with each established parallel to the others; set of two first change gear trains comprising first and second change drive gears (for example, first gear
21
a
and second gear
21
b
in
FIG. 1
of the embodiment) established on the input shaft, and first and second change driven gears (for example, third gear
22
a
and fourth gear
22
b
in
FIG. 1
of the embodiment), established on the first counter shaft, for engaging with first and second change drive gears; first and second clutch means (for example, first clutch
11
and second clutch
12
in
FIG. 1
of the embodiment), established on the input shaft, for connecting and disconnecting the input shaft and the set of two first change drive gears; set of two second change gear trains comprising third and fourth change drive gears (for example, third gear
22
a
and fifth gear
22
c
in
FIG. 1
of the embodiment) established on the first counter shaft, and third and fourth change driven gears (for example, sixth gear
23
a
and seventh gear
23
c
in
FIG. 1
of the embodiment), established on the second counter shaft, for engaging with the third and fourth change drive gears; third and fourth clutch means (for example, the third clutch
13
and fourth clutch
14
in
FIG. 1
of the embodiment), established on the second counter shaft, for connecting and disconnecting the second counter shaft and the set of two second change driven gears; third change gear train comprising a fifth change drive gear (for example, the eighth gear
23
d
in
FIG. 1
of the embodiment) established on the second counter shaft, and fifth change driven gear (for example, the ninth gear
24
d
in
FIG. 1
of the embodiment), established on the output shaft, for engaging with the fifth change drive gear; and fifth clutch means (for example, fifth clutch
15
in
FIG. 1
of the embodiment), established between the first counter shaft and output shaft, for connecting and disconnecting the first counter shaft and output shaft.
In a parallel shaft transmission with such a constitution, the driving force transmitted from the engine to the input shaft is transmitted to the output shaft at a reduction ratio corresponding to the selected gear train, by means of a gear train such as the first change gear train, second change gear train, and third change gear train, through the selective connection and disconnection of each clutch means established on the input shaft and second counter shaft. Furthermore, by the connection and disconnection of the fifth clutch means established between the first counter shaft and output shaft, the driving force of the input shaft can be transmitted to the output shaft at the reduction ratio of the first gear train, without passing through the second gear train and third gear train. For this reason, a transmission with the same number of speeds can be constituted with a number of clutches less than the number of speeds, such as a six forward speed transmission constituted with five hydraulic clutches. Consequently, a parallel shaft transmission, with improved drivability and fuel consumption and with an increased number of speeds, can be provided without cost increases or increased size and weight of the transmission due to an increased number of clutches.
Moreover, a parallel shaft transmission can be constituted as follows: a reverse coupling gear train (for example, reverse gear trains
21
r
,
26
,
22
r
in
FIG. 1
of the embodiment) is established between the input shaft and first counter shaft; and a forward and reverse switching mechanism (for example, reverse selector
16
in
FIG. 1
of the embodiment) is disposed on the input shaft. With this constitution, the clutch means (for example, second clutch
12
and third clutch
13
in
FIG. 1
of the embodiment) disposed on the first counter shaft or second counter shaft can be used both for forward and reverse. For this reason, a transmission, with which forward and reverse are possible, can be constituted without increasing the number of clutch means and the size of the transmission, and a compact parallel shaft transmission can be provided.
Also, a parallel shaft transmission can be constituted as follows: a reverse coupling gear train is established between the input shaft and first counter shaft; and a forward and reverse switching mechanism (for example, the reverse clutch
46
in
FIG. 9
of the embodiment and the reverse selector
86
in
FIG. 10
of the embodiment) is disposed on the first counter shaft. With this constitution, the clutch means disposed on the first counter shaft or second counter shaft as above can be used both for forward and reverse, and a transmission, with which forward and reverse are possible, can be constituted without increases to transmission size. Furthermore, because the forward and reverse switching mechanism is disposed on an axis with few clutch means, increases to the axial dimensions can be minimized and a compact parallel shaft transmission can be provided.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed descriptio

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