Steering mechanism of driving transmission

Motor vehicles – Steering by driving – Auxiliary steering motor

Reexamination Certificate

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Reexamination Certificate

active

06260641

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an operation mechanism of a hydrostatic transmission (hereinafter abbreviated as “HST”) type transmission apparatus applied to a crawler type working vehicle, wherein the apparatus has a driving HST constituting a non-stage transmission mechanism for speed changing and a steering HST constituting a non-stage transmission mechanism for turning.
BACKGROUND ART
Conventionally, it is well-known that a crawler type working vehicle is driven by use of an HST type non-stage transmission mechanism (as described in Japanese Utility Model Laid Open Gazette No. Sho 60-89,454). However, there has been no HST type transmission apparatus having an HST type non-stage mechanism for driving and an HST type mechanism for steering.
SUMMARY OF THE INVENTION
A transmission apparatus M of the present invention is so constructed that a steering HST mechanism
28
constituting a non-stage transmission mechanism for turning is juxtaposed with a driving HST mechanism
25
constituting a non-stage transmission mechanism for driving, the driving HST mechanism
25
being operated by a speed changing lever
68
, and the steering HST mechanism
28
being operated by a round steering wheel
19
. The rate of operational slanting angle of the speed changing lever
68
coincides with the rate of rotary speed of the steering HST mechanism
28
when the operated steering wheel
19
reaches its stroke end, thereby improving the operation feeling of the steering wheel
19
during the extreme low speed driving.
A speed changing servo rod
111
, which is operated by the operation of the speed changing lever
68
, is connected with a speed changing operation arm
151
of the driving HST mechanism
25
. The connecting portion between the speed changing servo rod
111
and the speed changing operation arm
151
has a clearance so that the arm
151
does not start rotating or the vehicle does not advance until the speed changing lever
68
is operated to a certain degree, thereby increasing the rotational angle of the speed changing lever
68
for the extreme low speed driving, whereby a rotational angle of a steering operation arm
162
, when the operated steering wheel
19
reaches its stroke end, is increased.
The operation mechanism including the speed changing lever
68
and the steering wheel
19
for the HST type transmission apparatus having the juxtaposed driving and steering HST mechanisms
25
and
28
according to the present invention, wherein the driving HST mechanism
25
is operated by the speed changing lever
68
and the steering HST mechanism
28
is operated by the steering wheel
19
, has effects as follows:
Firstly, due to the construction that the ratio of speed between left and right driving devices is changed by change of rotational angle of the steering wheel
19
, as the rotational angle of the steering wheel
19
for turning is increased, the difference of speed between left and right driving crawlers
2
is gradually increased, so that the turning radius is reduced, thereby making the turning angle agree with the feeling of an operator.
Secondly, while the rotational angle of the steering wheel
19
is the same, the turning angle is changed according to the change of operation angle of the speed changing lever
68
, so that the vehicle turns on a small circle slowly and on a large circle fast. If the vehicle turned on a common circle either slowly or fast when the steering wheel
19
was operated at the same angle, the vehicle might roll sideways when turning at high speed. According to the present invention, this problem can be prevented.
Thirdly, even though the left and right driving devices are of a crawler type, the vehicle can spin or turn on an extreme small circle easily by use of the firstly and secondly mentioned operation mechanism for a transmission apparatus.
Fourthly, the firstly and secondly mentioned operation mechanism for a transmission apparatus is further constructed so that, when the steering wheel
19
is operated for turning while the speed level determined by the speed changing lever
68
is low, as the operation angle of the steering wheel
19
is increased, the driving device on the turning side is gradually decelerated and the driving device on the opposite side gradually accelerated, and while the speed level is high, the opposite side driving device is also decelerated gradually, however, the rate of speed reduction of the turning side driving means is larger than the other. Hence, the vehicle can naturally turn with the most comfortableness for the operator mainly by deceleration of the turning side without acceleration of the opposite side.
Fifthly, the fourthly mentioned steering mechanism of a transmission apparatus is further constructed so that, when the rotational angle of the steering wheel
19
is small, the speed reducing rate of the decelerated side is small and the speed increasing rate of the accelerated side is large, and when the angle is large, the relation of scale between the speed reducing rate of the decelerated side and the speed increasing rate of the accelerated side is inverse. Hence, even the case of a large circular turning or that the operation angle of the steering wheel
19
is small, a natural steering operation can be obtained.
Sixthly, the fourthly mentioned steering mechanism of a transmission apparatus is further constructed so that, when the speed level determined by the speed changing lever
68
is low, both the turning and opposite sides are gradually decelerated, however, the opposite side is accelerated once, and then is gradually decelerated. Hence, when fast driving, the vehicle can be prevented from rapid turning, so that it can turn naturally whether the case is a large circular turning or a small circular turning.


REFERENCES:
patent: 4174762 (1979-11-01), Hopkins et al.
patent: 4420991 (1983-12-01), Meyerle
patent: 4600068 (1986-07-01), Lenhard-Backhaus
patent: 4882947 (1989-11-01), Barnard
patent: 5477455 (1995-12-01), Ishino et al.
patent: 53-18135 (1978-02-01), None
patent: 5-301580 (1993-11-01), None
patent: 7-76285 (1995-03-01), None
patent: 7-329818 (1995-12-01), None
patent: 8-142906 (1996-06-01), None
patent: 8-156821 (1996-06-01), None
patent: 8-310434 (1996-11-01), None

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