United States Patent t 11) 4,326,558

Gage 45 Apr. 27, 1982

(54) STEERING SYSTEM INCLUDING 4,160,490 7/1979 Bexten .............................. 60/405 X
ACCUMULATOR FOR SUPPLYING 4,242,867 1/1981 Belart ................................ 60/404 X
EMERGENCY RESERVE OF FLUID Primary Examiner-Robert G. Nilson
75 Inventor: Douglas M. Gage, Dubuque, Iowa 57 ABSTRACT
73 Assignee: Deere & Company, Moline, Ill. A hydraulic fluid power system includes an accumula
(21) Appl. No.: 209,763 tor which stores a reserve of pressure fluid at pump
standby pressure. The charging and discharging of the
22 Filed: Nov. 24, 1980 accumulator is controlled by an emergency steering
(51 Int. Cli ............................................... B62D 5/08 valve which is operable in response to a predetermined
(52) U.S. C. ...................................... 137/554; 60/328; minimum fluid pressure outputted by the steering pump
60/404; 91/28; 137/113; 180/133; 251/54; to discharge the stored fluid for emergency steering.
251/63.4; 251/297 The emergency steering valve also has components
58) Field of Search ......................... 60/328, 404, 405; which serve as a pressure switch which is actuated to
91/28; 180/133; 137/110, 113, 114,554; complete a circuit through an indicator light whenever
251/36, 47, 54, 63.4, 297 the emergency steering valve moves to effect the dis
References Cited
charge of the accumulator. The steering valve compo
56) nents are arranged so that premature actuation of the
U.S. PATENT DOCUMENTS indicator light during pressure drops of short duration
3,174,500 3/1965 Johnson .......................... 251/297 X . are avoided.
3,227,172 1/1966 Sims ........... ... 251/54 X
3,448,756 6/1969 Nordegren........................ 251/47 X 5 Claims, 1 Drawing Figure

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U.S. Patent Apr. 27, 1982 4,326,558

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 4,326,558
1. 2
routes a reserve of emergency steering fluid to the main
STEERING SYSTEM INCLUDING steering valve... - .
ACCUMULATOR FOR SUPPLYING EMERGENCY Yet another specific object of the invention is to pro
RESERVE OF FLUID vide, an emergency steering valve spool as set forth
above wherein it is detented in its closed position and is
BACKGROUND OF THE INVENTION regulated to move toward its open position at a prede
The present invention relates to hydraulic fluid termined rate. . ..
power steering systems having an accumulator for sup These and other objects will become apparent from a
plying fluid in the event that the vehicle engine or pri 10 reading of the ensuing description, together with the
mary fluid pressure source fails and more particularly appended drawing.
relates to improvements in the system disclosed in co BRIEF DESCRIPTION OF THE DRAWING
pending application, Ser. No. 196,199, filed on Oct. 14, The sole FIGURE shows a portion of a power steer
1980 by Gage et al and assigned to the same assignee as ing system, including a longitudinal sectional view of
is the instant application. the emergency steering valve and a schematic represen
A power steering system disclosed in the above-iden 15
tified patent application includes an emergency steering tation of the electrical steering mode indicator circuit.
valve coupled to an accumulator, to a steering fluid DESCRIPTION OF THE PREFERRED
pressure supply pump and to a main steering control EMBODIMENT
valve and comprises a pressure-responsive valve spool Referring now to the drawing, therein is shown a
which occupies a normal or closed position wherein it 20 pertinent portion of a power steering system indicated
prevents the discharge of fluid from the accumulator in its entirety by the reference numeral 10. The steering
when the system pressure is above a predetermined system 10 includes a pump 12 driven by a vehicle engine
minimum value and automatically shifts to an emer and connected to an accumulator 14 through the me
gency or open position wherein it permits fluid to dis 25 dium of an emergency steering valve 16. The pump 12
charge from the accumulator to the main steering valve and valve 16 are connected to a main steering valve
when the system pressure decreases to the predeter indicated by the functional box. 18.
mined minimum value. When the valve spool shifts to As will be described in more detail below, the emer
its emergency position, it completes an electrical circuit
to an indicator which apprises the operator that the 30 gency steering valve 16 embodies structure which
steering system is operating in an emergency steering condition aindicator
serves as pressure switch forming part of a steering
circuit 20.
mode. One drawback of this electrical circuit is that it The emergency steering valve 16 includes a valve
requires a resistor which acts as a source of constant body 22 defining a valve bore
power drainage. Another drawback is that the valve end closed by a threaded plug 26.24A having its left-hand
spool may oscillate in response to pressure surges and 35 aligned with the bore 24 and is intersected 28
passage
by
is axially
an inlet
effect a premature activation of the emergency steering port 30, which is connected to the outlet of the pump 12
mode indicator. by a conduit 32. Intersecting the bore 24 at respective
SUMMARY OF THE INVENTION locations spaced leftwardly in serial order from the
right-hand end of the bore are a charge-discharge port
According to the present invention, there is provided 40 34, a steering pressure fluid outlet port 36 and a sump
an improved emergency steering valve arrangement for port
completing an electrical circuit to an indicator which by a38. The port 34 is connected to the accumulator 14
conduit 40 while a branch of the conduit 18 is
apprises an operator that the vehicle steering system is connected to the
operating in an emergency steering mode. Specifically, port 38 to sump. port 36 and a conduit 42 connects the
the emergency steering valve includes a pressure 45 Fluid is routed from the inlet port 30 to the accumula
responsive valve spool which occupies a normal or tor 14 by way of the charge-discharge port 34 through
closed position wherein it blocks communication be an accumulator charge passage 44 having, as viewed in
tween an emergency fluid supply contained within an the drawing, a vertical section intersecting the passage
accumulator and a main steering valve when a steering 28 and a horizontal section intersecting the port 34.
fluid supply pump is supplying a normal amount of 50 Mounted in the vertical section of the passage 44 is a
fluid, the valve spool shifting to an emergency or open one-way valve 46 arranged for permitting fluid to flow
position wherein it permits fluid to discharge from the from the inlet port 30 to the accumulator 14 but not in
accumulator to the main steering valve when the output the opposite or reverse direction.
from the steering fluid pump drops below a normal Axially, shiftably mounted in the bore 24 for control
value. The valve spool serves as one contact of a switch 55 ling the flow of fluid between the ports 34 and 36 is a
having another contact which the valve spool engages valve spool-48. Specifically, the spool 48 has a land 50
to complete a circuit to the emergency steering mode at its right-hand end and intermediate land 52 spaced
indicator when the valve spool reaches its open posi leftwardly from the land 50 and a land 54 spwaced
tion. leftwardly from the land 52. A relatively shallow recess
It is an object of the invention to provide an electri 60 56 exists between the lands 50 and 52 while a much
cally controlled emergency steering mode indicator deeper recess 58 exists between the lands 52 and 54. A
which is efficiently and reliably energized only when an coil compression spring 62 is compressed between the
emergency steering mode condition exists. plug 26 and the left-hand end of the land 54 and acts in
It is a more specific object of the invention to provide opposition to any force as might be exerted on the right
an indicator embodied in an electrical circuit having an 65 hand end of the spool by a pin 64 reciprocably mounted
emergency steering valve spool as one contact of a in the passage 28 and having its right-hand end exposed
switch of the circuit which is closed only upon the to system pressure at the inlet port 30. To insure free
steering valve reaching an open position wherein it movement of the spool 48, a passage 66 extends axially
 3
4,326,558 4.
through the spool and is in constant fluid communica from the balls 70 and when the pin 64 becomes engaged
tion with the sump port 38. For a purpose to be ex with the screw head 74, this delay being chosen to pre
plained in more detail below, the right-hand end of the vent premature energization of the indicator light 80, as
passage 66 forms an orifice 68 which regulates the speed might occur during pressure surges in the hydraulic
at which the valve spool 48 will shift within the bore 24. 5 system.
When the valve spool 48 is in its normal operating The operation of the steering system is thought to be
position, as illustrated, the land 52 is located between understood from the foregoing and for the sake of brev
the charge-discharge port 34 and the outlet port 36 and ity, no further description is given.
thus prevents discharge of the accumulator 14. The I claim:
valve spool 48 is maintained in this position so as not to 10 1. In an emergency steering valve including a valve
be affected by pressure surges by means of a plurality of bore intersected by first and second ports respectively
spring-loaded detent balls 70 which are engaged in an adapted for connection to an accumulator and to a main
annular detent groove 72 formed in the land 54. How power steering valve, a pressure-responsive valve spool
ever, upon the pressure at the inlet port 30 falling to a reciprocably mounted in the bore for movement be
predetermined minimum value, which is less than the 15 tween a closed position wherein it blocks fluid commu
lowest pressure expected during normal system pres nication between the first and second ports and an open
sure fluctuations, the spring 62 will overcome the force position wherein it establishes fluid communication
exerted by the pin 64 and the detent balls 70 and will between the first and second ports, pilot pressure means
shift the spool 48 rightwardly to its emergency or open adapted for connection to a primary source of fluid
position wherein the intermediate land 52 is disposed 20 pressure and arranged for shifting the valve spool to its
rightwardly of the charge-discharge port 34 to thus closed position when the fluid pressure emanating from
connect the accumulator 14 for discharging its reserve the primary source is adequate for normal steering oper
of fluid pressure through the outlet port 36 for use in ation, a biasing means arranged for shifting the valve
emergency steering operation. spool to its open position when the primary source of
When the valve spool 48 is in its open or emergency 25 fluid pressure fails and an electrical steering condition
position, the right-hand end of the spool is in engage indicator circuit including an energizable indicator ele
ment with the pin 64 and holds the latter in engagement ment and a pressure switch means operable for complet
with a head 74 of an insulated screw 76 received in a
plug 78 closing the right-hand end of the passage 28. ing a circuit through the indicator element only when
The pin 64 and the head 74 of the screw 74 form oppo 30 the valve spool is shifted away from its closed position,
site contacts of a normally open switch of the steering the improvement comprising: said pressure switch
condition indicator circuit 20. An operator of the vehi means including means operated by the valve spool for
cle embodying the steering system is made aware or completing the circuit through the indicator element
apprised of the fact that the pressure in the system has only when the valve spool reaches its open position and
fallen below that for normal operation and that the 35 delay means for regulating the speed of travel of the
system is operating in an emergency steering mode with valve spool from its closed to its open position for pre
the accumulator 14 supplying the steering fluid by acua venting premature actuation of the indicator element in
tion of an indicator, here shown in the form of a light 80, response to primary fluid pressure decreases of short
connected in the circuit 20. Specifically, the light 80 is duration.
connected in series with the normally open pressure 40 2. The emergency steering valve defined in claim 1
switch formed by the screw 76 and the pin 64. A source wherein the delay means comprises a restricted passage
of electrical current, here shown in the form of a battery interconnecting fluid chambers at the opposite ends of
84, is connected to a power lead 86 in which is located the valve spool.
an on-off switch 88 that is preferably embodied in the 3. The emergency steering valve defined in claim 2
vehicle ignition switch such as to be closed any time the 45 wherein the restricted passage extends axially through
vehicle engine is running. Thus, it will be appreciated the valve spool.
that under normal operating conditions, with the pin 64 4. The emergency steering valve defined in claim 1
shifted leftwardly out of engagement with the head 74 wherein the pilot pressure means comprises a passage
of the screw 76, an open circuit will exist and no current extending axially into the valve bore, a pin reciprocably
will be flowing through the indicator light 80. How 50 mounted in the passage and an inlet port communicat
ever, upon there being a loss of pressure sufficient that ing with an end of the pin and adapted for connection to
the spring 62 disengages the spool 48 from the detent the primary source and said pressure switch means
balls 70, the valve spool 48 will move rightwardly and including said pin and a contact arranged for engage
engage the pin 64 with the head 74 to complete the ment by the pin when the valve spool is in its open
circuit and activate the indicator light 80. The size of 55 position.
the orifice 68 governs the speed at which the spool 48 5. The emergency steering valve defined in claim 1
will travel rightwardly after it is released from the de and further including detent means for releasably hold
tent balls and thus, a predetermined delay exists be ing the spool in its closed
2k k
position.
s sk sk
tween the time when the spool 48 becomes released
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