Lubrication pressure controller

Details Lubrication pressure controller Lubrication pressure controller

1999-08-05

2001-06-12

Fenstermacher, David (Department: 3682)

Lubrication

Systems

With safety or indicating means

C184S006220, C184S006280, C184S026000

Reexamination Certificate

active

06244385

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a hydraulic controller which controls the pressure of hydraulic oil, and particularly to a hydraulic controller which has a cooling circuit that cools part of the hydraulic oil through an oil cooler.
BACKGROUND OF THE INVENTION
Vehicles such as automobiles are equipped with a hydraulic controller which controls actuators for the transmission, the clutch, etc. and also provides pressure necessary for the lubrication of these parts. Many of such hydraulic controllers include an air- or water-cooled oil cooler, which cools the hydraulic oil whose temperature increases while it is used for the control and lubrication of the transmission, the clutch, etc.
In such a hydraulic controller, the following method is used commonly. A pressure regulating valve is provided in the circuit of the hydraulic oil to adjust the pressure of the hydraulic oil, and the oil discharged from this pressure regulating valve is returned through an oil cooler to a tank (or a drain pan). In addition to this method, there is another method in which the discharge port of the above mentioned pressure regulating valve is constructed in two ports, one for a line which passes through the oil cooler and the other for a line used for recirculation. In this construction, when the amount of the oil discharged from the pressure regulating valve increases, the oil is directly returned through the recirculation line to the suction port of the pump.
FIG. 6
is a circuit diagram of a conventional lubrication pressure controller which includes a recirculation line. In this device, the hydraulic oil in a tank T is sucked by a pump P through a suction strainer and a suction oil passage
31
. After the pressure of the oil is adjusted by two regulator valves
33
and
34
to a predetermined hydraulic pressure (line pressure), the oil is then supplied through a line
35
to a speed change control valve. Excess oil in the pressure adjustment performed by the regulator valves
33
is dumped to a lubrication oil passage
36
(
36
a
and
36
b
), and the oil in this oil passage is supplied as lubrication oil to the components of the transmission which need lubrication (e.g., to the starting clutch, the planetary gears, the bearing parts of the shafts, etc.). The lubrication oil after being supplied to the speed change mechanism and the other components which require lubrication returns to the tank T through oil passages, for example, passages constituted by the inner walls of the transmission (not shown).
In the lubrication oil passage
36
(between
36
a
and
36
b
), which leads the hydraulic oil to the parts which require lubrication, a lubrication valve
71
is provided to adjust the pressure of the oil used for the lubrication. This valve comprises a spool
71
a
which is biased leftward by a spring
71
b
. The hydraulic oil moves this spool
71
a
rightward in correspondence with the magnitude of the pressure supplied into the oil chamber
71
c
and performs a pressure adjustment which achieves a predetermined lubrication pressure Pb needed for supplying the oil to the parts of the transmission which require lubrication.
For example, when the supply pressure (i.e., the discharge pressure of the regulator valves
33
and
34
) in the lubrication oil passage
36
a
is smaller than the predetermined lubrication pressure Pb, the spool
71
a
is shifted leftward by the spring
71
b
, so the hydraulic oil flowing in the lubrication oil passage
36
a
is partly supplied through a line
80
to the parts requiring lubrication but not through the other lines except the line
36
b
. On the other hand, if the supply pressure in the lubrication oil passage
36
a
becomes greater than the predetermined lubrication pressure Pb, the spool
71
a
is shifted rightward by the hydraulic pressure supplied into the oil chamber
71
c
, the pressure overpowering the resistance of the spring
71
b
. In this condition, the line
81
a
which passes through an oil cooler
85
to the tank T is open together with the line
80
, so part of the hydraulic oil is cooled and returned to the tank T. If the supply pressure increases further, then the spool
71
a
is shifted further rightward (this condition is shown in FIG.
6
). In this condition, another line
82
is open together with these lines
80
and
81
a
. This line
82
, which is called “recirculation line”, returns directly to the suction oil passage
31
of the pump P without passing through the oil cooler
85
and the tank T.
In vehicular transmissions, it is general that the pump P is directly connected to the output shaft of the engine, so the rotational speed of the pump P is proportional to that of the engine. Thus, there is a tendency that the greater the rotational speed of the engine, the higher the pressure of the hydraulic oil which is discharged from the regulator valves
33
and
34
and supplied into the lubrication oil passage
36
a
. This means that the operation of the valves described above is performed in correspondence with the rotational speed of the engine and that when the rotational speed of the engine is relatively high, the oil is flown through the recirculation line
82
directly to the suction oil passage
31
of the pump P in addition to the line
81
(
81
a
and
81
b
) passing through the oil cooler
85
.
In addition to this method, which controls the supply of the hydraulic oil to the oil cooler in correspondence with the pressure in the lubrication oil passage by means of the stroke of a valve spool as described above, there is another method in which the oil passage leading to the parts requiring lubrication and the oil passage leading to the oil cooler are switched by a (three-way) electromagnetic valve. This method is disclosed, for example, in Japanese Laid-Open Patent Publication No. H4(1992)-316766. Yet another method, which controls the flow of the hydraulic oil to the oil cooler, is disclosed in Japanese Laid-Open Utility-Model Publication No. H1(1989)-135254. In this method, an electromagnetic valve is provided in the oil passage leading to the oil cooler, and the flow of the hydraulic oil is changed by the on-off control of the valve.
However, in the previously mentioned prior-art lubrication pressure controller (e.g., one shown in FIG.
6
), if the lubrication valve
71
is disturbed by an external factor, for example, if the pressure in the lubrication oil passage
36
a
is disturbed by a drastic change in the amount discharged from the pump or in the control back pressure of the regulator valve
33
, and thereby the spool of the lubrication valve experiences an overstroke rightward, then the hydraulic oil flows excessively into the recirculation line
82
and causes a shortage in the amount of the hydraulic oil which is supplied to the lubrication oil passage
36
b
and to the oil cooler. Furthermore, if the spool is locked in such an overstroke condition, then there is a possibility that the recirculation line
82
will experience a negative pressure by the suction pressure of the pump P and will draw the hydraulic oil into the lubrication oil passage
36
a
. There is a concern that if this condition occurs, then the shortage of the hydraulic oil which should be supplied to the parts requiring lubrication would continue and result in a lubrication failure.
In the method which switches the oil passage leading to the parts requiring lubrication and the oil passage leading to the oil cooler by a (three-way) electromagnetic valve as disclosed, for example, in Japanese Laid-Open Patent Publication No. H4(1992)-316766, by construction, this switching involves all the hydraulic oil. Thus, the system requires a large electromagnetic valve capable of handling a relatively large flow, and this requirement makes it difficult that this method is to be applied to the condition which requires both the lubrication and the cooling of the transmission.
In the method which is disclosed in Japanese Laid-Open Utility-Model Publication No. H1(1989)-135254, the electromagnetic valve that is provided in the oil

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