192 clutches and power-stop control – Vortex-flow drive and clutch – With brake
Reexamination Certificate
2002-04-16
2004-04-27
Rodriguez, Saul (Department: 3681)
192 clutches and power-stop control
Vortex-flow drive and clutch
With brake
C192S003230
Reexamination Certificate
active
06725987
ABSTRACT:
REFERENCE TO PRIOR APPLICATIONS
This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in Japanese Patent Application No. 2001-121300 filed on Apr. 19, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power transmission device for transmitting power from the engine of heavy motor vehicles such as trucks and buses to the transmission, comprising a fluid coupling and a friction clutch, and more particularly to a gear parking brake enabling in-gear parking.
2. Description of the Related Art
Conventionally, a power transmission device that uses a fluid coupling in combination with a wet multiplate friction clutch has been proposed as a power transmission device for transmitting power from the engine of heavy motor vehicles such as trucks and buses to the transmission.
As shown in
FIG. 5
, this power transmission device has a fluid coupling
4
and a wet multiplate friction clutch
5
joined between the engine's crankshaft
1
and input shaft
3
of the transmission
2
, so as to be able to connect and disconnect. This enables smooth gear change and reliable power transmission to be achieved without it being necessary for the driver to operate the clutch.
The basic structure and application of a conventional power transmission device having this kind of structure will be described below.
First, in the same way as a well-known conventional fluid coupling, the fluid coupling
4
mainly consists of a pump shell
7
fixed to the engine's crankshaft
1
through a casing
6
, a turbine shell
8
positioned opposite the pump shell
7
, and a stator
9
fixed therebetween. The torque of the crankshaft
1
is delivered from the pump shell
7
through the fluid filled therein to the turbine shell
8
, and the torque of the turbine shell
8
is transmitted to an output shaft
11
that is connected to the wet multiplate friction clutch
5
, through a hub
10
. Further, a lock-up mechanism
13
(to be described later) activated by a fluid-activated mechanism
12
is formed between the casing
6
and the turbine shell
8
, and when the engine speed reaches a prescribed speed, the crankshaft
1
and output shaft
11
are directly linked through the above mechanisms and efficient power transmission is achieved.
Next, the wet multiplate friction clutch
5
comprises a clutch outer
14
spline fitted to the output shaft
11
, and a clutch center
15
mounted to the input shaft
3
of the transmission
2
. In the same way as in a conventional wet multiplate friction clutch, a plurality of friction plates
16
formed on the inside of the clutch outer
14
and a plurality of friction plates
17
formed on the outside of the clutch center
15
are made to come into contact with each other, thereby transmitting the power of the output shaft
11
to the input shaft
3
of the transmission
2
. Further, this wet multiplate friction clutch
5
contains a connection and disconnection mechanism
18
activated by a fluid-activated mechanism
12
, which will be described later, and when the engine is started or the gears are changed, the clutch outer
14
and the clutch center
15
disengage and the power between the output shaft
11
and the input shaft
3
is cut off.
Further, the fluid-activated mechanism
12
that operates this lock-up mechanism
13
of the fluid coupling
4
and the connection and disconnection mechanism
18
of the wet multiplate friction clutch
5
mainly consists of a hydraulic pump
21
formed inside an intermediate wall
20
of a joint housing
19
that contains the above-mentioned fluid coupling
4
and wet multiplate friction clutch
5
; a lock-up mechanism control valve
22
and a connection and disconnection mechanism control valve
23
activated by the operating oil discharged from the hydraulic pump
21
as shown in
FIG. 6
; and electromagnetic selector valves
24
and
25
to control the activation and shutoff of these control valves
22
and
23
. As shown in
FIG. 5
, this hydraulic pump
21
operates the whole time that the engine is running, accompanying the rotation of the pump shell
7
of the fluid coupling
4
, and it sucks in the operating oil that is pooled in the operating oil retention space
26
at the bottom of the joint housing
19
through a suction passage
27
. The operating oil is sent to the above-mentioned lock-up mechanism control valve
22
and the clutch connection and disconnection mechanism control valve
23
and either activates these valves or after passing through is returned back into the operating oil retention space
26
in a cycle. Further, the electromagnetic selector valves
24
and
25
that activate the lock-up mechanism valve
22
and the connection and disconnection mechanism control valve
23
are each controlled by control signals from a controller consisting for example of a micro-computer (not shown in the drawings).
In a power transmission device having this kind of construction, first, when the engine starts up, the lock-up mechanism
13
of the fluid coupling
4
and the connection and disconnection mechanism
18
of the wet multiplate friction clutch
5
are both turned to a disconnected (OFF) state. Therefore, in the fluid coupling
4
a state of so-called creep occurs, the power from the engine's crankshaft
1
is cut off by the wet multiplate friction clutch
5
, and is not transmitted to the input shaft
3
of the transmission
2
. Next, from this state when the driver shifts the transmission
2
into gear to move the vehicle, the controller, which receives this signal, activates the electromagnetic selector valve
25
and the clutch connection and disconnection mechanism control valve
23
. Accordingly the connection and disconnection mechanism
18
is activated by the operating oil discharged from the hydraulic pump
21
, and by connecting the wet multiplate friction clutch
5
, the power from the output shaft
11
is transmitted to the transmission
2
through the input shaft
3
and the vehicle begins to move. In such a way, the engine's power is transmitted to the transmission
2
and the vehicle starts moving, and when a prescribed speed is reached, the driver then operates a shift lever
28
to shift the transmission
2
up to second gear, third gear and so on in order to further increase the speed of the vehicle. However, each time the driver shifts up to a higher gear, it is automatically controlled so that the instant that the driver operates the shift lever
28
this is detected by the controller and the wet multiplate friction clutch
5
is momentarily cut off. Then, after the shift to the next gear has been completed the wet multiplate friction clutch
5
is automatically reconnected, and thus smooth upshift is achieved. Further, at the same time, when the vehicle has reached a prescribed speed, the lock-up mechanism
13
of the fluid coupling
4
is activated by an electromagnetic control valve
24
, which is also activated by the controller. By directly connecting the crankshaft
1
and the output shaft
11
, power from the engine's crankshaft
1
is transmitted to the transmission
2
without loss.
However, in a vehicle with a power transmission device having this kind of construction, so-called in-gear parking cannot be achieved. In other words, when the engine
1
is stopped in order to park, the hydraulic pump
21
for engaging the wet multiplate friction clutch
5
is inactivated and the wet multiplate friction clutch
5
is automatically disengaged. Therefore, whatever gear the transmission
2
is put into, the wet multiplate friction clutch
5
just runs idle and the engine brake does not work, meaning that the vehicle cannot be put into a definite stop.
Further, the side brake that is ordinarily used when parking a motor vehicle is not always able to be used and is prone to certain inconveniences, for example the brake wire may freeze in cold temperatures and not be able to be unfrozen, or the wire that activates it may snap.
For these reasons, methods such as forming a multip
Isuzu Motors Limited
McCormick Paulding & Huber LLP
Rodriguez Saul
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