Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
1998-12-14
2001-08-21
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S436000, C060S441000, C060S447000, C060S448000, C091S506000, C475S073000, C475S075000, C475S076000, C475S080000
Reexamination Certificate
active
06276134
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for controlling a plurality of hydraulic oil motors and a clutch, which apparatus is structured so as to provide the output torque of the plurality of hydraulic motors in accordance with a connection of the clutch in a hydraulic drive apparatus for a working machine, such as a wheel loader, a hydraulic excavator, or the like.
BACKGROUND OF THE INVENTION
In a hydraulic oil traveling drive apparatus for a vehicle which is driven by connecting the output torque of a plurality of hydraulic oil motors by means of a clutch; the output torque, the vehicle speed, and the like are conventionally controlled by connecting or disconnecting the clutch when the vehicle speed becomes a predetermined value.
FIG. 7
is a control circuit of a conventional control apparatus for a plurality of hydraulic oil motors and a clutch. The control circuit is constituted by the hydraulic oil pump
50
, the first hydraulic oil motor
51
, the second hydraulic oil motor
52
, the clutch
53
, a hydraulic oil pump
54
, and the like. The first hydraulic oil motor
51
and the second hydraulic oil motor
52
are connected to the hydraulic oil pump
50
in parallel, and are driven by pressurized oil discharged by the hydraulic oil pump
50
. The first motor gear
51
b
is fixed to the first output shaft
51
a
of the first hydraulic oil motor
51
, and the first motor gear
51
b
is engaged with the gear
55
a
, which is fixed to the drive shaft
55
for driving the vehicle. The output torque of the first hydraulic motor
51
is always transmitted to the drive shaft
55
via the first motor gear
51
b
and the drive shaft gear
55
a.
The clutch
53
is provided in the output shaft
52
a
of the second hydraulic motor
52
. The second motor gear
53
b
, for the second hydraulic motor
52
, is fixed to the second output shaft
53
a
of the clutch
53
, and the second motor gear
53
b
is engaged with the gear
55
a
for the drive shaft
55
. When the clutch
53
is engaged, the output torque of the second hydraulic motor
52
is transmitted to the drive shaft
55
for driving the vehicle via the clutch
53
, the second motor gear
53
b
, and the drive shaft gear
55
a
. A servo valve is attached to each of the first and second hydraulic motors
51
and
52
, and the discharge volume (cc/rev) of each of the first and second hydraulic motors
51
and
52
is controlled in accordance with a pressure signal from a high and low valve (hereinafter, referred to as an HL valve, not shown) for selecting between a high speed and a low speed.
The hydraulic oil pump
54
is connected to the drive shaft gear
55
a
via the pump gear
54
a
and the second motor gear
53
b
. The shuttle valve
54
c
, positioned in the conduit
54
e
, and the throttle
54
b
are connected in parallel between the Fp port and the Rp port of the hydraulic oil pump
54
. When a rotating speed of the drive shaft
55
(corresponding to the vehicle speed) becomes equal to or greater than a predetermined speed value, the discharge pressure of the hydraulic oil pump
54
reaches a predetermined pressure value which disengages the clutch
53
via the conduit
54
d
. When the rotating speed of the drive shaft
55
is less than the predetermined speed value, the discharge pressure of the hydraulic oil pump
54
does not reach the predetermined pressure value, so that the clutch
53
is still engaged. Further, the hydraulic pump
50
and the first hydraulic motor
51
are always connected to each other; however, the communicating and shutting valve
56
is interposed in the conduit
54
f
between the hydraulic pump
50
and the second hydraulic motor
52
, so that in a first position of the valve
56
the second hydraulic motor
52
is isolated from the hydraulic pump
50
, and in a second position of the valve
56
the second hydraulic motor
52
is connected to the hydraulic pump
50
.
A function of the communicating and shutting valve
56
will be described. When a tilt rotation amount is present in the second hydraulic motor
52
, a speed changing shock is generated by a disengaging of the clutch
53
; therefore, the tilt rotation amount of the second hydraulic oil motor
52
is set to be zero (hereinafter, referred to as a zero tilt rotation) before disengaging the clutch
53
. However, since there is no means provided for holding the zero tilt rotation position for the second hydraulic motor
52
, when even just a little tilt rotation amount is provided at the second hydraulic motor
52
, due to a sudden speed change or the like after setting the second hydraulic motor
52
to be at the zero tilt rotation (refer to the broken line S
5
in FIG.
9
), the second hydraulic motor
52
races and a load slip of the first hydraulic motor
51
is generated. In order to prevent the load slip, after the second hydraulic oil motor
52
is set to be at the zero tilt rotation, the conduit
54
f
, which connects the hydraulic pump
50
to the second hydraulic motor
52
, is shut by the communicating and shutting valve
56
at the same time as the clutch
53
is disengaged.
An operation of the conventional control circuit will be described below.
FIG. 8
shows the relation between the hydraulic motor discharge volume (cc/rev) and the vehicle speed (km/h) in the low speed range Lo. The curve S
1
shows the relation for the first hydraulic motor
51
, and the curve S
2
shows the relation for the second hydraulic motor
52
. For example, since the wheel loader is structured such that the discharge pressure of the hydraulic pump
54
does not reach a predetermined pressure value until the vehicle speed is 12 km/h, the clutch
53
is in the engaged state. Accordingly, the wheel loader is driven by a large drive force, corresponding to the sum (S
1
+S
2
) of the discharge volumes of the first hydraulic motor
51
and the second hydraulic motor
52
. In this case, when it is set to the low range Lo by the HL valve (not shown), the discharge volumes of the first hydraulic motor
51
and the second hydraulic motor
52
are limited, and the maximum vehicle speed is increased only to 12 km/h.
FIG. 9
shows the relation between the hydraulic motor discharge volume (cc/rev) and the vehicle speed (km/h) in the high speed range Hi. The curve S
3
shows the relation for the first hydraulic motor
51
, and the curve S
4
shows the relation for the second hydraulic motor
52
. In this case, since the discharge pressure of the hydraulic pump
54
does not reach the predetermined pressure value until the vehicle speed is 15 km/h, the clutch
53
is in the engaged state. When the vehicle speed is near 15 km/h, the discharge volume S
4
of the second hydraulic motor
52
approaches zero. Thus, when it is set to the high speed range Hi by the HL valve (not shown), the limit of the discharge volume of the first hydraulic motor
51
is canceled, and the vehicle speed is increased to 30 km/h or more by only the discharge volume S
3
of the first hydraulic motor
51
. Further, when the vehicle speed is 15 km/h or more, the discharge pressure of the hydraulic pump
54
reaches the predetermined pressure value, and the clutch
53
is disengaged.
In the conventional hydraulic oil traveling drive apparatus described above, since the communicating and shutting valve
56
must be a large size so that the total discharge amount of the second hydraulic motor
52
can pass therethrough, there is a problem in that the cost for the piping and for the communicating and shutting valve
56
is great, and a large space is necessary. Further, since it is necessary to shut the communicating and shutting valve
56
at the same time as disengaging the clutch
53
, a speed changing shock and the like are generated when this delicate timing is not satisfied. Further, in the case of fixing each of the first and second hydraulic motors
51
and
52
with a large tilt rotation amount and increasing the brake torque so as to reduce the vehicle speed, there is a case wherein the vehicle overruns when the fixed tilt rotation amount is still l
Fukuda Masao
Ikari Masanori
Inoue Hiroaki
Matsuyama Nobuo
Komatsu Ltd.
Lopez F. Daniel
Sidley Austin Brown & Wood
LandOfFree
Apparatus for controlling a plurality of hydraulic motors... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for controlling a plurality of hydraulic motors..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for controlling a plurality of hydraulic motors... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2446570