[0001] The present invention relates to an engine cooling fan control apparatus, and more
particularly to apparatus for preventing thermal seizure of the drive shaft of a turbo-supercharger
installed in the engine.
[0002] In an internal combustion engine with a turbo-supercharger which discharges compressed
air to the engine to improve engine output, the drive shaft common to the exhaust
turbine and the compressor of the turbo-supercharger is subjected to hot exhaust gas
so that the shaft has a tendency to be seized by its bearings.
[0003] The present invention provides an apparatus which senses the temperature of exhaust
to drive a turbo-supercharger shaft cooling means when the sensed temperature exceeds
a predetermined value, thereby preventing seizure of the shaft by its bearings.
[0004] In the drawings:
Fig. 1 is a diagramatic illustration of a preferred embodiment of a turbo-supercharger
shaft cooling apparatus according to the present invention;
Fig. 2 is a view, similar to Fig. 1, of a second embodiment of the present invention;
and
Fig. 3 is a schematic diagram of the timer of Fig. 2.
[0005] The same reference numerals are used to designate similar elements of the embodiments
shown in the figures.
[0006] Referring to Fig. 1, there is shown a preferred embodiment of a turbo-supercharger
shaft cooling apparatus according to the present invention..In the particular embodiment,
a battery 1 is adapted to supply electrical power to a fan motor 4, installed to cool
the engine compartment, via a fusible link 2 and a fuse 3 when the circuit is closed,
thereby driving fan motor 4 to cool the engine compartment and therefore the exhaust
turbine shaft and its bearings which are subjected .to hot exhaust. Switch 5, acting
as a thermal sensor, is closed when the exhaust temperature exceeds a predetermined
value, and is open when the exhaust temperature falls below the predetermined value.
Fusible link 2 and fuse 3 are for protection of battery 1 and the whole circuit from
short- circuiting and/or malfunction of motor 4.
[0007] Referring to Fig. 2, there is shown a second embodiment of a turbine shaft cooling
apparatus according to the present invention. In addition to the previously described
cooling function while the engine is running, this embodiment ensures that the turbine
shaft and bearing will be cooled for a predetermined interval after the ignition key
is turned off when the exhaust temperature exceeds the predetermined value because
the temperature of the engine compartment tends to rise greatly after the engine is
turned off. In this embodiment, battery 1 has one electrode grounded and the other
electrode connected via fusible link 2 and fuse 3 to one terminal of fan motor 4,
the other terminal of which is connected to a control terminal C of a timer 6 which
serves to control the operating interval of motor 6. The power supply for timer 6
is provided by connection of a power supply terminal B thereof to the output of fuse
3. Timer 6 has an ignition detection terminal Ig to detect the off state of an ignition
switch 7. Terminal Ig is connected via a fuse 8 to a terminal of ignition switch 7,
the input of which is connected to the output of fusible link 2. Fuse 8 has the same
function as fuse 3. In Fig. 3, power supply terminal B is connected via a stabilizing
power source SB and an analog switch AS to a power supply line B' for an amplifier
10. When ignition switch 7 is closed analog switch AS is actuated via input terminal
Ig and a resistor r
1 to supply the stabilized supply voltage via
B' to amplifier 10. Returning to Fig. 2, an exhaust temperature sensor 9, provided
in the exhaust manifold, not shown, senses the temperature of exhaust and outputs
a signal to amplifier 10 when the sensed temperature is above a predetermined value,
for example 700°C. Sensor 9 may be a conventional semiconductor thermal sensor. Amplifier
10 amplifies the signal from sensor 9 and supplies the amplified signal S
T to timer 6. Amplifier 10 is supplied with electrical power from terminal B' only
while ignition switch is on. Timer 6 may have a structure such as shown in Fig. 3.
In this particular structure, an AND gate receives a drive input via resistor r
1 and an inverter INV from terminal Ig while ignition switch 7 is open. A level adjust
circuit including a Zener diode Z
D, a resistor r
2 and a capacitor C
1 adjusts the voltage at the control input terminal of analog switch AS and at inverter
INV to a desired value. Another drive input S
T is supplied from amplifier 10 to the AND gate. A hold circuit comprising a resistor
r
3 and a capacitor C
2 holds the value of S
T for a short time, for example 1 second. The time constant determined by r
3 and C
2 is selected to be greater than that determined by C
1 and r
2 of the level adjust circuit. When the AND gate outputs a high level signal, a monostable
multivibrator M/M produces a high level signal continuing for a short predetermined
time of from 1 to 3 minutes, thereby turning on a transistor Tr via an OR gate for
that interval to operate fan motor 4. For as long as the signal S
T persists, transistor Tr is also turned on via the OR gate, thereby operating fan
motor 4 for that interval during which the exhaust temperature exceeds the predetermined
value.
[0008] In operation, during engine operation, exhaust temperature sensor 9 continuously
checks the temperature of exhaust. When sensor 9 detects that the temperature of exhaust
exceeds the predetermined value (700°C in this particular embodiment), sensor 9 outputs
a signal and therefore amplifier 10 outputs a constant-level d.c. voltage signal as
signal S
T to timer 6 which drives motor 4 via the OR gate and transistor Tr for as long as signal
S
T persists. When ignition switch 7 is opened, the Ig control input to analog switch
AS disappears, and analog switch AS is turned off, thereby interrupting the supply
of electrical power to amplifier 10. At this time, the output signal S
T from amplifier 10 disappears, but the value of S
T immediately before S
T disappears is held by the hold circuit. Thus, both inputs to AND gate are high so
that monostable multivibrator M/M produces an output continuously for 1 to 3 minutes.
Thus the engine compartment, turbo-supercharger shaft and bearings are cooled whereby
seizure of the drive shaft is prevented.
[0009] The temperature of exhust corresponds accurately to the temperature of turbine shaft.
After engine stops, the temperature of the exhaust system can rise to a value higher
than any other system in the engine compartment. Thus, it is most recommendable to
sense the temperature of exhaust itself in order to prevent seizure of the turbo-supercharger
shaft by its bearings.
[0010] While the present invention has been described in terms of a preferred embodiment
thereof, it should be noted that the present invention is not limited thereto. Various
modifications and changes could be made by those skilled in the art without departing
from the scope of the present invention, as set forth in the attached claims.
1. Apparatus for preventing thermal seizure of the shaft and bearings of exhaust turbine
and compressor of a turbo-supercharger for use with an internal combustion engine,
comprising:
- means (5;9) for sensing the temperature of exhaust gas from the engine to output
a drive signal when the sensed temperature exceeds a predetermined value;
- means (4) for cooling the shaft and bearings, and
- control means (5;6) responsive to the drive signal for driving the cooling means
to cool the shaft and bearings.
2. Apparatus according to claim 1, characterized in that said control means includes
a timer (6) responsive to the opening of an ignition switch (7) and the presence of
a value indicative of the drive signal from said sensing means (9) immediately before
the opening of the ignition, switch to drive the cooling means (4) for a particular
time interval after the ignition switch has opened.
3. Apparatus according to claim 2, characterized in that said timer (6) includes means
(AS) responsive to the closing of said ignition switch (7) for supplying power therethrough
to said sensing means (9) and responsive to the opening of said ignition switch (7)
for interrupting the supply of said power to said sensing means (9), and means (C2,r3) for holding the value indicative of the drive signal for a short time.