U.S. patent number 3,783,301 [Application Number 05/261,080] was granted by the patent office on 1974-01-01 for lockout circuit for engine starter system.
This patent grant is currently assigned to Caterpillar Tractor Co.. Invention is credited to Robert L. Nieukirk.
United States Patent |
3,783,301 |
Nieukirk |
January 1, 1974 |
LOCKOUT CIRCUIT FOR ENGINE STARTER SYSTEM
Abstract
The risk of damage to starter mechanism for cranking an engine
is reduced by a simple and reliable lockout circuit which prevents
re-energization of the starter system from inadvertent closing of
the starter switch after the engine is running. The lockout circuit
detects when the engine has started by sensing engine oil pressure
but does not deactivate the starter system until such time as the
operator releases the starter switch. Thereafter the starter system
cannot be re-energized until after the engine has been shutdown.
All electrical elements of the lockout circuit are de-energized
during running of the engine after the starter switch is
released.
Inventors: |
Nieukirk; Robert L.
(Washington, IL) |
Assignee: |
Caterpillar Tractor Co.
(Peoria, IL)
|
Family
ID: |
22991874 |
Appl.
No.: |
05/261,080 |
Filed: |
June 8, 1972 |
Current U.S.
Class: |
290/37R;
290/38R |
Current CPC
Class: |
F02N
11/105 (20130101) |
Current International
Class: |
F02N
11/08 (20060101); F02n 011/00 () |
Field of
Search: |
;290/37,38
;123/179B |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simmons; G. R.
Attorney, Agent or Firm: McRae; Donald J.
Claims
I claim:
1. In a starter system for an engine having electrically operated
engine cranking means and a source of electrical power therefor and
having a normally open starter switch connected between said power
source and said cranking means for selectively energizing said
cranking means to start said engine, a lockout circuit
comprising:
a switching device connected between said power source and said
engine cranking means in series relationship with said starter
switch to form part of the power path through which electrical
energization is supplied to said cranking means from said power
source, said switching device being of the form which is normally
non-conductive and which is triggered into conduction by
application of an electrical gating signal to a gate terminal
thereof and which then remains conductive until current flow
through said switching device is interrupted, and
a gating signal switch having normally closed contacts connected
between said gating terminal and said power source through said
starter switch, said gating signal switch having means for opening
said contacts when said enging is running.
2. The combination defined in claim 1 wherein said switching device
is a silicon controlled rectifier and wherein said gating signal
switch is a fluid pressure operated switch responsive to oil
pressure from said engine.
3. A starter system for an engine having a ring gear which is
turned to start said engine and having an oil pump, comprising,
battery means,
an electrical starter motor,
a set of normally open electrical contacts connected across said
battery means in series with said starter motor,
a pinion gear coupled to said motor for rotation thereby and being
movable into engagement with said ring gear of said engine,
solenoid means which may be electrically energized and having means
for shifting said pinion gear into engagement with said ring gear
and for closing said normally open contacts to energize said motor
in response to said energization,
a normally open manually operable starter switch,
a solid-state switching means connected to said battery means in
series relationship with said starter switch and said solenoid
means and having a gate terminal for receiving an electrical signal
which initiates conduction through said switching means to provide
current therethrough for energizing said solenoid means, said
switching means being of the form which remains conductive until
current flow therethrough is stopped, and
a normally closed fluid pressure actuated switch connected between
said battery means and said gate terminal of said switching means
through said starter switch and having a fluid pressure input
coupled to said oil pump of said engine to be opened by fluid
pressure from said oil pump.
Description
BACKGROUND OF THE INVENTION
Starter systems for cranking an internal combustion engine or the
like customarily have a pinion gear which may be shifted into
engagement with a ring gear of the engine and rotated by
energization of an electrical starter motor in response to
actuation of a starter switch by the operator. To avoid excess wear
means are provided for retracting the pinion gear out of engagement
with the ring gear after start-up. Once the engine is running,
excess wear or serious damage can occur to the ring gear, the
pinion gear or other elements of the mechanism if the starter
switch is inadvertently reactuated at that time.
To forestall these adverse effects, some prior starter systems have
been provided with a lockout circuit which functions to prevent
reactivation of the starter system while the engine remains
running. Lockout circuits of this kind have means for detecting
when the engine is running and switch means for preventing
operation of the starter under this condition.
In general, prior lockout circuits have been unnecessarily complex.
Such circuits typically require an electrical signal, derived from
the engine generator or other electromechanical transducer, to
detect when the engine is running. Automatic means are provided for
immediately deactivating the starter, independently of the
operator's actions, in response to such signal and for preventing
reactivation as long as the signal remains present. In addition to
circuit complexity this requires that some portion of the lockout
circuit remains electrically energized throughout the period when
the engine is running and the automatic action deprives the
operator of the ability to control the duration of the initial
starter operation.
SUMMARY OF THE INVENTION
The present invention provides an extremely simple, reliable and
economical lockout circuit for preventing actuation of an engine
starter system while the engine is running.
In a preferred form the circuit detects the running condition of
the engine by sensing a fluid pressure such as engine oil pressure
rather than by requiring a continuous electrical signal input for
this purpose. The lockout circuit is connected between the starter
mechanism and the power source therefor through the operator's
starter switch and includes a switching device of the type which
conducts following receipt of a gate signal and which remains
conductive until current flow is stopped. Closing of the operator's
starter switch provides the gating signal through a normally closed
fluid pressure controlled switch which is opened by engine oil
pressure or the like once the engine has started. Opening of the
fluid pressure controlled switch does not in itself de-energize the
starting system since the switching device continues to conduct
until the operator releases the starter switch. Thereafter the
switching device cannot be again gated on as the gating signal path
is blocked at the fluid pressure controlled switch as long as the
engine continues to run.
Accordingly it is an object of this invention to provide a
simplified, highly reliable and economical lockout circuit for
preventing re-energization of the starter system of an engine after
the engine is running and the operator has released the starter
switch.
The invention, together with further objects and advantages
thereof, will best be understood by reference to the following
description of a preferred embodiment taken in conjunction with the
accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
The accompanying drawing diagrammatically shows an engine and
electrical starting system therefor together with electrical and
hydraulic circuit elements for providing a lockout function in
accordance with the present invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing, an engine 11 to which the invention
is applicable typically has a ring gear 12 coupled to a crank shaft
13 which must be turned to initiate starting of the engine. In
order to crank the engine 11, a starting system 14 typically has a
pinion gear 16 which is normally out of engagement with ring gear
12 but which is shifted axially into engagement therewith, as
indicated by arrow 17, upon electrical energization of a pinion
solenoid 18 having a movable armature 19. Solenoid 18 may be
energized by manual closing of a normally open operator's starter
switch 21. Closing of starter switch 21 connects one side of a
battery 22 to one end of the solenoid through a lockout circuit 23
which will hereinafter be described in more detail, the other end
of the solenoid being coupled to the other side of the battery and
being grounded to engine 11 in this particular example. A
protective fuse 24 and a current indicating ammeter 26 are
connected in series between battery 22 and starter switch 21 and
the generator 27 of engine 11 may be connected between ground and
the junction between ammeter 26 and starter switch 21 to recharge
the battery while the engine is in operation.
Energization of the pinion solenoid 18 to shift pinion gear 16 into
engagement with ring gear 12 also closes a set of normally open
switch contacts 28 which are connected across battery 22 in series
with a starter motor 29 thereby causing the motor to be actuated
following closing of the operator's starter switch 21. Motor 29 is
coupled to the pinion gear 16 through an overrunning clutch 31.
Thus closing of the starter switch 21 engages the pinion gear with
ring gear 12 and rotates the pinion gear to crank the engine 11.
Suitable constructional details of a starter system 14 as described
to this point, with the exception of lockout circuit 23, are well
known to the art and accordingly are not shown in the drawing. For
example, one typical mechanical assembly for a starter motor 29,
pinion solenoid and contact assembly 32, pinion gear 16 and
overrunning clutch 31 is disclosed in U.S. Pat. No. 3,433,968.
Considering now the lockout circuit 23, current is transmitted
between starter switch 21 and pinion solenoid 18 through a
preferably solid state switching means 33 of the form which is
normally non-conductive and which may be gated into conduction by a
gating signal and which thereafter remains conductive, even after
termination of the gating signal, until current flow therethrough
is stopped, such switching means 33 being an SCR (silicon
controlled rectifier) in this embodiment. To provide a gating
signal to SCR 33 under conditions to be described, a normally
closed fluid pressure operated switch 34 is connected between
starter switch 21 and the gate terminal 36 of SCR 33 in series with
a current limiting resistor 37 and a diode 38 which protects the
SCR from negative voltages such as might be present if the battery
22 was inadvertently reversed. Fluid pressure operated switches 34
are known devices, apart from the context of the present invention,
and may typically have contacts 39 which are normally held closed
by a spring 41 acting against a piston 42 within a cylinder 43, the
piston being coupled to the contacts. Introduction of fluid
pressure into cylinder 43 moves the piston 42 against the force of
spring 41 and thereby opens the contacts 39. Engines 11 of the form
to which the invention is applied typically have an oil pump 44 or
other means which generates a fluid pressure when the engine is
running. A conduit 46 connects the output of oil pump 44 to
cylinder 43 of pressure switch 34 whereby contacts 39 are opened
when the engine is running.
In operation, the operator initiates starting of engine 11 by
closing starter switch 21. SCR 33 becomes conductive at this point,
to energize the pinion solenoid 18, since closing of the starter
switch 21 also applies a gating signal to the SCR through pressure
switch 34, resistor 37 and diode 38. As previously described,
energization of pinion solenoid 18 shifts pinion gear 16 into
engagement with engine ring gear 12 while closing contacts 28 to
energize the starter motor 29 and thereby initiates cranking of
engine 11.
When engine 11 has started and is in operation, fluid pressure from
oil pump 44 opens contacts 39 of pressure switch 34 removing the
gating signal from SCR 33. This does not in itself stop
energization of the starting system 14 since an SCR 33 remains
conductive once it is gated on until current flow through the
anode-cathode circuit is stopped. This occurs in the present
instance, when the operator releases starter switch 21. Such
opening of switch 21 stops conduction through SCR 33 and
de-energizes pinion solenoid 18 which then restores and shifts
pinion gear 16 out of engagement with ring gear 12 while opening
contacts 28 to de-energize starter motor 29. Thereafter, the pinion
solenoid 18 and starter motor 29 cannot be re-energized by closing
of starter switch 21 as long as engine 11 remains running. Under
this condition, fluid pressure switch 34 is held open by the output
of oil pump 44 thereby blocking transmission of the necessary
gating signal to SCR 33. SCR 33 can again be gated into conduction
by closing of the starter switch 21 only after engine 11 has
stopped and fluid pressure is absent from pressure switch 34.
While the invention has been described with respect to a preferred
embodiment it will be apparent that modifications are possible and
thus it is not intended to limit the invention except as defined in
the following claims.
* * * * *