Motor vehicles – Motor as source of power for other machine – Hydraulic drive to other machine
Reexamination Certificate
2002-06-26
2003-06-03
Dickson, Paul N. (Department: 3616)
Motor vehicles
Motor as source of power for other machine
Hydraulic drive to other machine
C180S337000, C180S406000, C060S486000, C060S487000
Reexamination Certificate
active
06571894
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to transmission mechanisms for vehicles having an HST (hydrostatic transmission), and more particularly to a transmission mechanism for work vehicles equipped with a work device externally of the vehicle body, and also to a pressure oil supply system for the mechanism.
2. Description of the Related Technology
It is commonly demanded that various vehicles be shortened in forward or rearward length to diminish the turning radius, improve the ease of driving and achieve cost reductions. Especially, this is strongly demanded of work vehicles which are equipped with a work device externally of the vehicle body in front or in the rear thereof.
Work vehicles provided with a work device externally of the vehicle body have a PTO shaft at a portion of the transmission for transmitting power to the work device. With such work vehicles, it is desired that the transmission shaft interconnecting the PTO shaft and the input shaft of the work device be disposed horizontally to the greatest possible extent in order to prevent the joints of the transmission shaft from giving off noise and assure the joints of improved durability. For example, JP-U1 No. 56555/1993 and JP-A No. 204135/1990 disclose transmissions for work vehicles intended to meet this demand. The disclosed arrangements include pulleys or like cooperative means for positioning a PTO shaft
1103
at a lower level than a front axle
1105
to cause the shaft to project from the front end face of the front axle case (as indicated at X in FIG.
19
). Generally, the transmission shaft
1104
for a work device
1106
needs to be lengthened (as indicated at Y in
FIG. 19
) if it is attempted to position the transmission shaft
1104
closer to a horizontal while causing the PTO shaft
1103
, as positioned approximately at the same level as the engine drive shaft
1101
a
, to project from the front end of the front axle case, consequently increasing the overall vehicle length. Alternatively, the transmission shaft
1104
must be inclined (as indicated at Z in
FIG. 19
) if an attempt is made to shorten the overall vehicle length while causing the PTO shaft
1103
to project from the front end of the front axle case at substantially the same level as the engine drive shaft
1101
a
, consequently increasing the load on the transmission shaft and impairing the durability of the transmission shaft. In view of these structural drawbacks, the transmissions disclosed in the foregoing publications are so constructed as stated above.
In the case of the conventional construction described, however, a differential gear unit is to be interposed between the engine output shaft (or HST motor shaft) and the PTO shaft, so that the cooperative mechanism between the two shafts must be adapted to avoid the interference with the differential gear unit. This results in an increase in the vehicle cost and an impaired maintenance work efficiency.
With vehicles, especially with work vehicles, it is known to dividedly derive a rear wheel driving force from the output of an HST for driving the front wheels. JP-A No. 66749/1997, for example, discloses such a transmission mechanism. With reference to
FIG. 20
showing such a conventional transmission mechanism as is disclosed in this publication, a vehicle comprising a differential gear unit
1140
, HST
1120
and drive source
1110
which are arranged from the front of the vehicle rearward has a transmission
1130
, in which a driving force from the drive source is divided into a front wheel driving force and a rear wheel driving force. This construction has the following drawbacks. Incidentally, indicated at
1131
in the drawing is a front wheel drive shaft which is coupled to the differential gear unit
1140
for driving front axles
1151
, and at
1132
is a rear wheel drive shaft which is connected to a rear axle
1152
by an unillustrated transmission shaft.
The transmission mechanism shown in
FIG. 20
essentially requires the transmission
1130
, which increases the number of parts and the cost. The provision of the transmission
1130
further entails the problem of impairing the reliability of the vehicle. Since the transmission
1130
serves as a power transmission path for both the front wheel driving force and the rear wheel driving force, the components of the transmission are burdened with a great load. Accordingly, the gears and other components are susceptible to damage, which lowers the reliability of the vehicle. Furthermore, the transmission
1130
is provided in a limited space between the differential gear unit
1140
and the HST
1130
, necessitating difficult installation work, which leads to the problem that the vehicle is inefficient to assemble in its entirety.
With work vehicles equipped with a work device externally of the vehicle body, there is a need to provide a considerable distance between the engine and the HST because it is necessary to interconnect the drive source and the HST by means of universal joints. Stated more specifically, the drive source is installed on the vehicle body with rubber vibration isolators interposed therebetween, while the HST is connected to the differential gear casing which is fixed to the front axle cases. A vibration difference therefore occurs between the drive source and the HST. Accordingly, to interconnect the two components by a shaft with the vibration difference absorbed, universal joints are used for the shaft to be connected between the drive source and the HST. For this reason, there is a need to provide a distance permitting the arrangement of two universal joints in series between the HST and the drive source.
With vehicles wherein a PTO unit is provided which has a PTO shaft for a mower or like work device, and a hydraulic clutch for effecting or interrupting the transmission of the output of the PTO shaft, it is desired to position the PTO shaft inwardly of the vehicle body to the greatest possible extent while shortening the distance between the hydraulic clutch and a charge pump for supplying a hydraulic fluid to the clutch.
A shorter distance between the pump and the clutch is desirable because of the difficulty to be encountered in hydraulically controlling the clutch if the distance is great. Inward positioning of the PTO shaft is desirable in order to reduce the overall length of the vehicle including the mower or the like while horizontally positioning the connecting rod between the shaft and the mower or the like.
This will be described with reference to a front mount mower tractor which is equipped with a mower in front of the vehicle body. If it is attempted to shorten the overall length of the vehicle including the mower in an arrangement wherein the PTO shaft is caused to project forward from the front axle case, the transmission shaft interconnecting the PTO shaft and the mower must be given a great inclination. The transmission shaft is pivotally moved vertically when the mower is raised or lowered. If the inclination of the transmission shaft is greater, the angle through which the shaft is pivotally moved also increases, permitting the transmission shaft joints to produce a louder noise and impairing the durability of the joints. It is therefore desired that the PTO shaft be disposed inward longitudinally of the vehicle body (toward the rear of the vehicle body in the case of the front mount mower tractor) in order to shorten the overall length of the vehicle while obviating these drawbacks.
Thus, it is desired that the vehicle wherein the power of the drive source is transmitted to the travel device and to the PTO unit via the HST fulfill the foregoing requirements, whereas transmission mechanisms still remain to be developed which meet all of these requirements.
Conventionally, the following construction has been adopted for the pressure oil supply system for supplying a hydraulic fluid to power steering hydraulic devices or to hydraulic devices for lifting work devices such as mowers. The conventional pressure oil supply system has an ar
Ishimaru Yoshitaka
Nemoto Shusuke
Sakikawa Shigenori
Takada Kenichi
Dickson Paul N.
Kanzaki Kokyukoki Mfg. Co. Ltd.
Knobbe Martens Olson & Bear LLP
Rosenberg Laura B.
LandOfFree
Transmission mechanism for vehicles having HST and pressure... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmission mechanism for vehicles having HST and pressure..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmission mechanism for vehicles having HST and pressure... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3135895