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WO1998015749A1 - Procedes et appareillage destines a reguler la pression et systemes de servodirection electro-hydraulique a flux sensiblement adapte - Google Patents

Procedes et appareillage destines a reguler la pression et systemes de servodirection electro-hydraulique a flux sensiblement adapte Download PDF

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Publication number
WO1998015749A1
WO1998015749A1 PCT/US1997/018358 US9718358W WO9815749A1 WO 1998015749 A1 WO1998015749 A1 WO 1998015749A1 US 9718358 W US9718358 W US 9718358W WO 9815749 A1 WO9815749 A1 WO 9815749A1
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WIPO (PCT)
Prior art keywords
flow
fluid
metering
power
instant
Prior art date
Application number
PCT/US1997/018358
Other languages
English (en)
Inventor
Edward H. Phillips
Original Assignee
Techco Corporation
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Publication date
Application filed by Techco Corporation filed Critical Techco Corporation
Publication of WO1998015749A1 publication Critical patent/WO1998015749A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B62D5/065—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B62D5/08—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by type of steering valve used
    • B62D5/083—Rotary valves

Definitions

  • the present invention relates generally to electro- hydraulically energized vehicular power steering systems and, more particularly, to methods and apparatus for controlling pressure and substantially flow matched electro-hydraulic power steering systems having extraordinarily high efficiency.
  • Electro-hydraulic power steering systems typically comprise an electrically driven pump which, in turn, provides a continuous flow of pressurized fluid to an open-center control valve.
  • an electrically driven pump which, in turn, provides a continuous flow of pressurized fluid to an open-center control valve.
  • selected ones of control orifices comprised within the open-center control valve progressively close thus impeding the flow of pressurized fluid therethrough and causing system pressure to rise.
  • Virtually all of the rising system pressure is then applied to a power cylinder in order to provide steering assist.
  • Such a system can be referred to as a pressure matched electro-hydraulic power steering system.
  • the efficiency of such systems is inherently low since the energy involved in generating the portion of the pressurized fluid passing through the control valve but not the power cylinder is lost.
  • the present invention is directed to methods and apparatus for controlling operation of pressure and substantially flow matched electro-hydraulic power steering systems wherein a substantially greater portion of the power utilized in generating electro-hydraulically energized fluid is directly applied to a power cylinder.
  • electro- hydraulic power steering systems utilizing the control methods and apparatus described below have substantially better efficiency than has been known before.
  • the methods utilized for controlling such pressure and substantially flow matched electro-hydraulic power steering systems comprise providing a selected value of flow of metering fluid through a high impedance metering circuit whose flow impedance value is continually under the physical control of a host vehicle's driver.
  • valve input shaft i.e., a valve input shaft
  • second valve element i.e., a valve sleeve
  • Suitable valve sets each comprising first and second valve elements (and in this case a valve input shaft and a valve sleeve), are comprised in control valves described my co-pending U.S. Patent Application entitled “Control Valve Apparatus for Pressure and Substantially Flow Matched Electro-Hydraulic Power Steering Systems".
  • the resulting instant system pressure is substantially determined by the product of the flow of metering fluid value and the instant flow impedance value.
  • valve sets utilized by the pressure and substantially flow matched electro-hydraulic power steering systems described herein are relatively low impedance flow direction switching power circuits. Orientation of the switching power circuit is controlled by the driver (concomitantly with the high impedance metering circuit) via the direction of the driver's application of torque to the steering wheel. This enables directionally controlled application of instant values of system pressure to a power cylinder (also coupled to the host vehicle's dirigible wheels) for achieving the required directionally applied steering force.
  • a first method and apparatus for controlling further comprises providing all flow of pressurized system fluid from a single electrically driven pump unit comprising a servo motor and causing selected small portions of the flow of pressurized fluid to pass through the high impedance metering circuit.
  • a signal representative of instant values of fluid flow through the high impedance metering circuit (hereinafter "the metering fluid flow signal") is provided by a flow measuring transducer section of a metering flow regulation module such as the one described in another co-pending U.S.
  • the signal is compared with a selected value therefor in order to provide an error signal.
  • the first method and apparatus for controlling further includes amplifying the error signal and utilizing the amplified error signal to drive the servo motor of the electrically driven pump unit continually toward volumetric output values which minimize the error signal regardless of instant values of power fluid flow.
  • a second method and apparatus for controlling further comprises providing a metering pump for separately causing selected flow values of metering fluid to flow through the high impedance metering circuit at a flow rate determined in an open-loop fashion.
  • This provides a biasing pressure value which is applied to a biasing port of a null value differential pressure transducer.
  • an electrically driven pump unit provides a flow of power fluid to a low impedance flow direction switching power circuit and power cylinder in the manner described above.
  • the second method and apparatus for controlling further includes amplifying the error signal and utilizing the amplified error signal to drive a servo motor of the electrically driven pump unit for providing required values of power fluid flow, in such a manner as to continually minimize the error signal regardless of instant values of power fluid flow.
  • the percentage of pressurized fluid utilized by the high impedance metering circuit is quite small. For instance, it would typically be only about 15 percent of the fluid delivered to the power cylinder when parking a host vehicle at a hand wheel rotation value of 400 degrees per second. Thus, hydraulic system efficiencies in excess of 80 percent can be achieved under high pressure parking conditions.
  • Fig. 1 is a schematic flow circuit illustrative of a method and apparatus for controlling operation of a pressure and substantially flow matched electro-hydraulic power steering system disclosed in a preferred embodiment of the invention
  • Fig. 2 is a schematic flow circuit additionally descriptive of a control valve utilized in the preferred embodiment of the invention
  • Fig. 3 is a graphical diagram depicting the relative power requirements of a motor used in a prior art EHPS and a servo motor utilized in the preferred embodiment of the invention
  • Fig. 4 is a flow chart showing the steps of a method for controlling disclosed in the preferred embodiment of the invention.
  • Fig. 5 is a schematic flow circuit illustrative of a method and apparatus for controlling operation of a pressure and substantially flow matched electro-hydraulic power steering system in an alternate preferred embodiment of the invention
  • Fig. 6 is a flow chart showing the steps of a method for controlling disclosed in the alternate preferred embodiment of the invention
  • Figs. 7A, 7B and 7C are sectional and plan views of control valve elements in accordance with both of the preferred and alternate preferred embodiments of the invention
  • Fig. 8 is a partially schematic sectional view of a control valve utilized in the preferred embodiment of the invention
  • Figs. 9A and 9B are sectional views of fixed and variable orifices utilized in conjunction with the preferred embodiment of the invention.
  • Fig. 10 is a partially schematic sectional view of a control valve utilized in the alternate preferred embodiment of the invention. Detailed Description of the Preferred Embodiments
  • Fig. 1 Depicted in Fig. 1 is a schematic flow circuit illustrative of a first method and apparatus for controlling a first pressure and substantially flow matched electro-hydraulic power steering system (hereinbelow described as “first EHPS System 80") in accordance with a preferred embodiment of the invention. More particularly, Fig. 1 discloses, in block diagram form, a test flow circuit 10 actually used in development of the first method and apparatus for controlling.
  • an electrically driven pump unit 12 comprising a pump 14 driven by a servo motor 16 provides a flow of pressurized fluid, at pressure values determined in a manner to be described below, to a delivery line 18.
  • Selected values of metering fluid flow derived from the flow of pressurized fluid pass through a needle valve 20 to, and through, a flow measuring transducer 22 and on to a return line 26. All returning fluid flow is delivered via return line 26 to a system reservoir 28 from which the pump
  • the flow measuring transducer 22 comprises either a fixed orifice 32 or a variable orifice 34 through which the flow of metering fluid passes.
  • the fixed orifice 32 would be utilized in a non-speed sensitive version of the first EHPS System while the variable orifice 34 would be utilized in a speed sensitive version of the first EHPS System.
  • the variable orifice 34 can be manipulated to enable a selected value of metering fluid flow according to a selected function of vehicle speed, engine speed, road conditions and/or any other desired parameter by a control signal issued by the host vehicle's electronic control module 40.
  • a temperature transducer 36 provides a temperature signal representative of the instant temperature of the metering fluid to a control module 38 along with vehicle speed, engine speed, road conditions and/or any other desired parameter signals derived from the host vehicle's electronic control module 40.
  • the flow measuring transducer 22 also comprises a differential pressure transducer 42 which provides a metering fluid flow signal which is actually representative of the differential pressure associated with passage of the flow of metering fluid from a sensing pressure node 44 to the return line 26 via either of the fixed or variable orifices 32 or 34.
  • a differential pressure transducer 42 which provides a metering fluid flow signal which is actually representative of the differential pressure associated with passage of the flow of metering fluid from a sensing pressure node 44 to the return line 26 via either of the fixed or variable orifices 32 or 34.
  • the metering fluid flow and temperature signals are respectively transmitted from the flow measuring transducer 22 to the control module 38 via signal transmission lines 46a and 46b.
  • Present versions of the differential pressure and temperature transducers 42 and 36 respectively issue the metering fluid flow and temperature signals as analog signals.
  • the control module 38 comprises A-to-D converters 48 and 50 which respectively convert those analog signals to multi-bit digital metering fluid flow and temperature signals.
  • a digital controller 52 subtractively compares the multi-bit digital metering fluid flow signal with a multi-bit number that is derived from a first look-up table in response to the multi-bit temperature signal to create a multi-bit error signal representative of the difference between instant and selected values therefor.
  • the multi-bit error signal is then processed in a proportional and differential (e.g., "PD") manner to generate a compensated multi-bit error signal.
  • PD proportional and differential
  • the compensated multi-bit error signal is applied to a second look-up table from which a linearized multi-bit error signal is delivered to a power amplifier 54 via linearized multi-bit error signal line 56.
  • the power amplifier 54 then issues a suitable amplified power signal to the servo motor 16 via power buss 58. And, the servo motor 16 drives the pump 14 continually toward volumetric output values which minimize the various error signals mentioned above.
  • the PD function additionally comprises complex filtering to provide a selected servo "roll- off' characteristic while compensating for such things as mechanical and electrical time constants of the servo motor 16 and volumetric compliance of the delivery line 18 as indicated in Fig. 1 by capacitor 60.
  • the PD function additionally comprises complex filtering to provide a selected servo "roll- off' characteristic while compensating for such things as mechanical and electrical time constants of the servo motor 16 and volumetric compliance of the delivery line 18 as indicated in Fig. 1 by capacitor 60.
  • further compensation would be required for various hydro-mechanical features thereof, perhaps even including one or more notch filters for eliminating frequencies associated with physical resonances.
  • Patent No. 5,544,715 dated August 13, 1996 and entitled “Method and Apparatus for Enhancing Stability in Servo systems Comprising Hydro- Mechanically Driven Actuators”.
  • power fluid flow is conveyed between delivery line 18 and return line 26 via power fluid supply line 62 and a load valve
  • the metering fluid flow regulation module 24 includes dynamic braking section 66 which selectively conveys dynamic braking fluid between delivery line 18 and return line 26 via dynamic braking line 68.
  • the dynamic braking section 66 comprises a spring biased, differentially activated, normally closed two-way valve 70. Its control port 72 is fluidly connected to sensing pressure node 44 while its biasing port 74 is fluidly connected to return line 26. Thus, opening of the spring biased, differentially activated, normally closed two-way valve 70 is also controlled by the sensing pressure. Whenever the force provided by spring 76 is overcome by excessive sensing pressure values, dynamic braking fluid flows through dynamic braking line 68. In normal static operation, selected values for the digital metering fluid flow signal are slightly less than the value that would cause the sensing pressure to overcome the force provided by spring 76.
  • a first exception demonstrates an additional operational feature wherein it is possible to speed up the electrically driven pump unit 12 in order to assist in warming up the fluid. This is accomplished at very cold temperatures by setting up the first look-up table such that the multi-bit number derived therefrom in response to very low values of the multi-bit temperature signal results in the sensing pressure partially overcoming the force provided by spring 76. Then the spring biased, differentially activated, normally closed two-way valve 70 is partially opened and additional fluid flow is delivered from the electrically driven pump unit 12.
  • the power amplifier 54 is normally configured as a single quadrant amplifier (e.g., one that only puts out unidirectional real power). This means that the electrically driven pump unit 12 is always slowed via back pressure on the pump 14 slowing the pump 14 and servo motor 16 against their combined moment of inertia. While this is happening, normal operation intermittently continues under hydro-mechanical control provided by the spring biased, differentially activated, normally closed two- way valve 70 instead of by the electronic means described above. As will become apparent hereinbelow with reference to the more detailed system described with reference to Fig.
  • FIG. 2 Shown in Fig. 2 is a schematic flow circuit which depicts the function of a first EHPS System 80 in accordance with the preferred embodiment of the invention.
  • First EHPS System 80 comprises most of the elements of the test flow circuit 10. They are similarly numbered and will not be further described herein.
  • the functions of needle valve 20 and load valve 64 are respectively implemented by high impedance metering valve 82 and a four-way low impedance flow switching valve 84 comprised in a control valve assembly 86.
  • the four-way low impedance flow switching valve 84 is used to enable directionally controlled application of instant values of system pressure to a power cylinder 88 for achieving required directionally applied steering force.
  • the four-way low impedance flow switching valve 84 is implemented by two input orifices 90a and 90b, and two return orifices 92a and 92b. Although they are all nominally closed-center orifices, it is desirable for either set of input orifices 90a and 90b or return orifices 92a and 92b to be configured in a slightly underlapped manner and the other of them to be configured in a slightly overlapped manner. Usually, the set of return orifices 92a and 92b is configured in a slightly underlapped manner. This results in an on-center fluidic fault, at the low pressure value of the return line 26, between ports 94a and 94b of the power cylinder 88. This, in turn, enables non-pointing behavior of the first EHPS System 80 when installed in a host vehicle. Providing low pressure for the power cylinder 88 while in its on-center mode is important because it reduces on- center friction via minimized seal drag.
  • the set of input orifices 90a and 90b is usually configured in a slightly overlapped manner in order to preclude any passage of power fluid from the power fluid supply line 62 until a preselected level of torque is applied to the host vehicle's steering wheel.
  • This in combination with the slightly underlapped set of return orifices 92a and 92b, enables an ideal on-center feel of pure mechanical steering without interdiction of a flow of power fluid from the power fluid supply line
  • the four-way low impedance flow switching valve 84 such that the incipient opening point of the slightly overlapped set of input orifices 90a and 90b occurs at a slightly higher value of applied torque than the incipient closing point of the slightly underlapped set of return orifices 92a and 92b. This ensures a smooth transition from purely mechanical on-center steering to power assisted steering after the closing of the slightly underlapped set of return orifices 92a and 92b.
  • the control valve assembly 86 In addition to enabling directionally controlled application of instant values of system pressure to the power cylinder 88, the control valve assembly 86 must be able to effectively extract regenerative hydraulic power from the power cylinder 88 whenever the host vehicle exits a turn. This is because the dirigible wheels would then drive the power cylinder 88 in a reverse direction. This would be problematic for a first EHPS System 80 described above because such dirigible wheel powered motion of the power cylinder 88 can be independent of the instant disposition of the four-way low impedance flow switching valve 84. And in general, resulting instant values of flow impedance of the input and return orifices 90a, 90b, 92a and 92b might yield excessive (and nonlinear) pressure value changes.
  • control valve assembly 86 comprises input check valves 96a and 96b respectively positioned in parallel with input orifices 90a and 90b, and return check valves 98a and 98b respectively positioned in parallel with return orifices 92a and 92b.
  • return check valves 98a and 98b respectively positioned in parallel with return orifices 92a and 92b.
  • Fig. 3 Shown in Fig. 3 is a graphical diagram depicting the relative speed/torque requirements of a drive motor comprised in a prior art EHPS system and the servo motor 16 of a similarly sized first EHPS System 80 during identical parking maneuvers.
  • both motors are of the field weakening type and could, for instance, be either switched reluctance or induction motors.
  • Identical maximum motor performance envelopes are depicted in Fig. 3 by line 100, which depicts maximum torque, hyperbolic curve 102, which depicts maximum power, and line 104, which depicts maximum speed.
  • the motor of the prior art EHPS system operates somewhere along the line 104 or hyperbolic curve 102 as determined by a nominally linear relationship between system pressure and motor torque.
  • instant torque/speed operating points of the servo motor 16 are respectively determined by system pressure and steering wheel speed as is described above.
  • a typical parking maneuver that starts on-center might begin at an operating point of full speed and about 40% torque for the drive motor of a prior art EHPS system.
  • a locus of instant operating points follows line 104 and hyperbolic curve 102 to maximum steering deflection operating point 108. Then, assuming that the driver forcibly holds the steering system at its end point or stop, the locus of instant operating points follows hyperbolic curve 102 to maximum power and torque operating point 110 where it remains as long as the driver continues to apply torque.
  • a parking maneuver at 400 degrees per second steering wheel velocity that similarly starts on-center begins at an operating point of about 45% of full speed and about 40% torque for the servo motor 16 as depicted by point 112.
  • a locus of instant operating points follows line 114 to maximum steering deflection operating point 116.
  • the locus of instant operating points follows curve 118 to maximum torque and metering flow operating point 120 where it remains as long as the driver continues to apply torque.
  • Instant power requirements of the servo motor 16 relative to those of the drive motor of a prior art EHPS system are linearly related to the horizontal fraction of the distance to line 104 or hyperbolic curve 102 depicted by positions along line 114 or curve 118. And, this is for the industry standard for maximum steering wheel velocity during parking. A more normally seen steering wheel velocity of 200 degrees per second would proportionately reduce these instant power levels to those depicted by line 114a and curve 118a. Overall, such a typical parking maneuver could be accomplished by the first EHPS System 80 with about 1/3 of the energy expended by the prior art EHPS system.
  • Fig. 4 Depicted in Fig. 4 is a flow chart showing the steps of a method for controlling first EHPS System 80.
  • the method includes the steps of providing a flow of pressurized fluid; separating a flow of metering fluid from the flow of pressurized fluid; applying the flow of metering fluid to a metering valve (e.g., the high impedance metering valve 82); controlling pressure values of the flow of metering fluid, and thus pressure values of the flow of pressurized fluid, via manipulation of the metering valve; measuring the value of the flow of metering fluid (e.g., with flow measuring transducer 22) in order to provide a signal indicative thereof; comparing the signal indicative of the value of the flow of metering fluid with a selected value therefor in order to provide an error signal indicative of the difference between the value of the flow of metering fluid and the selected value therefor; controlling the provision of pressurized fluid (e.g., by amplifying the error signal for suitably driving the servo motor
  • FIG. 5 Shown in Fig. 5 is a schematic flow circuit which depicts the function of a second EHPS System 130 in accordance with the alternate preferred embodiment of the invention.
  • Second EHPS System 130 comprises many of the elements of the test flow circuit 10 and first EHPS System 80. They are similarly numbered and will not be further described herein.
  • a separate metering fluid supply module 132 supplies a selected value of metering fluid flow directly to the high impedance metering valve 82.
  • a temperature transducer 36 provides a temperature signal representative of the instant temperature of the metering fluid to a metering control module 134.
  • the metering control module 134 also receives other desired parameters from the host vehicle's control module 40 (as described above with reference to control module 38) and selectively provides electric power to a metering motor/pump 136 via power buss 138. This results in the provision of the selected value of metering fluid flow to the high impedance metering valve 82 via metering fluid line 140 according to a selected function of fluid temperature, vehicle speed, engine speed, road conditions and/or any other desired parameter.
  • the spent flow of metering fluid then returns to a system reservoir 142 via metering flow return line 144. Fluid is drawn via suction line 146 (from the system reservoir 142) by the metering motor/pump 136 as required.
  • Instant values of metering pressure present in the metering fluid line 140 are applied to a biasing port 148 of a null value differential pressure transducer 150.
  • electrically driven pump unit 12 provides a flow of power fluid to power fluid line 152 wherefrom instant values of control pressure are applied to control port 154 of the null value differential pressure transducer 150.
  • a signal representative of the differential pressure therebetween is delivered to a control module 156, via differential pressure signal line 158, wherein it is digitized and filtered as described above with reference to control module 38.
  • a linearized multi- bit error signal is then conveyed from the control module 156 to a power amplifier 162 via linearized multi-bit error signal line 160.
  • the power amplifier 162 then issues a suitable amplified power signal to the servo motor 16 via power buss 164.
  • servo motor 16 drives the pump 14 continually toward volumetric output values which minimize the linearized multi-bit error signal.
  • null value differential pressure transducer 150 biasing pressure is conveyed to the spring loaded end of a spring biased, differentially activated, normally closed two-way valve 166, and control pressure is conveyed to its opposite end.
  • Regenerative power can be dissipated in a dynamic braking manner by the null value differential pressure transducer 150 via dynamic braking line 165 similarly to the dynamic braking action described above with respect to dynamic braking section 66 of the metering fluid flow regulation module 24.
  • a position measuring transducer 168 provides a position signal indicative of the actual position of a moving element 170 of the spring biased, differentially activated, normally closed two-way valve 166 to the control module 156.
  • the control module 156 utilizes digitizing means, lookup tables and the like to provide a linearized multi-bit error signal conveyed to the power amplifier 162.
  • the flow of power fluid delivered to power fluid line 152 from electrically driven pump unit 12 is also conveyed to a control valve assembly 86 and thereby to a power cylinder 88.
  • the second EHPS System 130 performs in a substantially identical manner to the first EHPS System 80.
  • the operational power requirements of second EHPS System 130 are substantially identical to those illustrated in Fig. 3B.
  • Fig. 6 Depicted in Fig. 6 is a flow chart showing the steps of a method for controlling second EHPS System 130.
  • the method includes the steps of providing a flow of metering fluid; applying the flow of metering fluid to a metering valve; controlling pressure values of the flow of metering fluid via manipulation of the metering valve; providing a flow of power fluid; comparing the pressure value attained by the flow of power fluid with the controlled pressure value of the flow of metering fluid in order to provide an error signal indicative of the difference therebetween; controlling the provision of power fluid in a manner which reduces the error signal, thus substantially maintaining instant pressure values of the flow of power fluid equal to instant pressure values of the flow of metering fluid, regardless of the instant flow and pressure values of the flow of power fluid; and utilizing the flow of power fluid for driving a load.
  • Figs. 7A, 7B and 7C Depicted in Figs. 7A, 7B and 7C are common elements of control valves suitable for use in the implementation of either of the preferred or alternate preferred embodiments of the invention. Included are two identical high impedance open-center circuits 180. As shown in Fig. 7A, pressurized fluid enters the high impedance open-center circuits
  • Each high impedance open-center circuit 180 includes a series arrangement of three transverse slots including input slot 184, transverse connecting slot 186 and output slot 188 as particularly shown in Fig. 7C wherein an input port 182 is indicated in phantom by dashed lines.
  • metering fluid enters each high impedance open-center circuit 180 via input port 182 and flows over a first metering ramp 190 to a first axial connecting slot 192 as particularly shown in Fig.
  • the metering fluid then flows along first axial connecting slot 192 and enters transverse connecting slot 186 by flowing over a second metering ramp 194.
  • the metering fluid then flows over a third metering ramp 196 to a second axial connecting slot 198.
  • the metering fluid flows along second axial connecting slot 198, enters output slot 188 by flowing over a fourth metering ramp 200, and exits via sensing pressure port 202.
  • Relative rotation of input shaft 204 with respect to valve sleeve 206 is attained in a well known manner by applying torque to input shaft 204 and twisting interconnecting torsion bar 208.
  • Relative clockwise rotation of input shaft 204 with respect to valve sleeve 206 results in progressive closure of the sure control orifice 210a which is tween first metering ramp 190 and corner 212 of first axial connecting slot 192, and a similar pressure control orifice 210b associated with second metering ramp 194.
  • relative counterclockwise rotation of input shaft 204 with respect to valve sleeve 206 results in progressive closure of similar pressure control orifices 210c and 21 Od associated with third and fourth metering ramps 196 and 200.
  • there is progressive closure of two series connected pressure control orifices whereby the total pressure drop associated with the high impedance open-center circuits 180 is substantially equal to twice the pressure drop associated with each closing pressure control orifice.
  • Fig. 8 Depicted in Fig. 8 are additional details of a control valve 220 in accordance with the preferred embodiment of the invention.
  • Fig. 8 is a sectional view taken along section lines respectively labeled A-A and B-B in Fig. 7A.
  • Additional general details of control valve 220 include a positive attachment of torsion bar 208 to a pinion 222 with a pin 224 and a driving attachment of the pinion 222 to a valve sleeve 206a via pin 226.
  • the first and second axial connecting slots 192 and 198 as well as respective left and right turn slots 228a and 228b are formed as axially oriented slots in the valve sleeve 206a and sealed off by rings 230 on each end.
  • An input shaft 204 is supported for relative rotation with respect to the pinion 222 by bushing or needle bearing 232.
  • the input shaft 204 and the pinion 222 are respectively formed with three shaft extension notches 234 and three arms 236 as described in my U.S. Patent Application Serial Number 08/577,415 filed on December 22, 1995 and entitled "Method and Apparatus for Forming a Control Valve for Hydraulic Circuits".
  • metering and power fluid commonly enter power fluid annular groove 238 via power fluid supply line 62 and an input housing port (not shown). Then the metering fluid passes through input port 182 to input slot 184. Then the metering fluid passes on through transverse connecting slot 186 and output slot 188 to a sensing pressure port 202 as described above. Sensing pressure is conveyed to the sensing pressure node 44 (shown in Figs. 1 and 2) via sensing pressure annular groove 240 and a sensing housing port (not shown).
  • the power fluid flows from the open one of the input power orifices 90a or 90b and through respective ones of left or right turn slots 228a or 228b, left or right turn ports 246a or 246b and left or right turn passages (i.e., passages generally provided in a rack-and-pinion power steering gear by left and right turn tubes) 248a or 248b to left or right ports 94a or 94b of power cylinder 88.
  • left or right turn slots 228a or 228b left or right turn ports 246a or 246b and left or right turn passages (i.e., passages generally provided in a rack-and-pinion power steering gear by left and right turn tubes) 248a or 248b to left or right ports 94a or 94b of power cylinder 88.
  • returning power fluid flows from the other of left or right ports 94a or 94b through the other of left or right turn passages 248a or 248b and left or right turn ports 246a or 246b to the other of left or right turn slots 228a or 228b.
  • Power fluid flows through the concomitantly open opposite one of return power orifices 92a or 92b, formed via superposition of the appropriate ones of left or right turn slots 228a or 228b and return slots 250, and then through return ports 252 to annular passage 254 formed between input shaft 204 and the torsion bar 208.
  • the spent power fluid exits through return ports 256 formed in the three shaft extension notches 234 and flows to the reservoir 28 via a return housing port (not shown).
  • Figs. 9A and 9B Depicted in Figs. 9A and 9B are respective sectional views of the flow restrictive portions of fixed and variable orifices 32 and 34 alternately utilized in first EHPS System 80.
  • the fixed orifice 32 comprises a nozzle shape characterized by the flow of metering fluid serially passing through a radiused entry section 258 and a divergent passage 260 as indicated by flow direction arrow 262.
  • variable orifice 34 is configured as a solenoid (not shown) operated needle valve 264 similarly characterized by the flow of metering fluid serially passing through a radiused entry section 266 and a divergent passage 268 as indicated by flow direction arrow 270.
  • divergent passage 268 is formed between solenoid driven needle 272 and conical bore 274 of housing 276. Divergent geometries are utilized to avoid silting problems while divergence angles and lengths of divergent passages 260 and 268 are experimentally developed to substantially match low temperature flow characteristics to those of pressure control orifices 210a-d.
  • Fig. 10 Depicted in Fig. 10 are alternate control valve details of a control valve 280 utilized in second EHPS System 130.
  • Fig. 10 is a sectional view taken along section lines respectively labeled A-A and B-B in Fig. 7A.
  • Most details of control valve 280 are identical to those of control valve 220. They are similarly numbered and will not be further described herein.
  • metering fluid is separately provided by the metering fluid supply module 132 to metering fluid annular groove 282.
  • the metering fluid enters input slot 184 via input port 284 and exits output slot 188 by flowing through return port 286 formed in an input shaft 204a to annular passage 254 and on to reservoir 28 as described above.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
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  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

L'invention concerne des procédés et un appareillage destinés à réguler la pression et des systèmes de servodirection électro-hydraulique à flux sensiblement adapté. En particulier, ces procédés consistent à prévoir des valeurs sélectionnées de débit de fluide de mesure pour une soupape de dosage (20) conçue pour faire varier des valeurs de pression du débit de mesure. Dans un mode de réalisation préféré, le débit de mesure est obtenu à partir d'un débit de fluide pressurisé, lequel est appliqué de façon concomitante à une vanne de charge (64) en vue d'amener une charge à une pression sensiblement égale en valeur à celle du débit de mesure. Dans un autre mode de réalisation préféré de cette invention, un débit d'énergie hydraulique fourni indépendamment est régulé de façon à être égal en valeur de pression à celui du débit de mesure, et utilisé par une vanne de charge en vue d'amener une charge à une pression sensiblement égale en valeur à celle du débit de mesure.
PCT/US1997/018358 1996-10-10 1997-10-10 Procedes et appareillage destines a reguler la pression et systemes de servodirection electro-hydraulique a flux sensiblement adapte WO1998015749A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US2844696P 1996-10-10 1996-10-10
US60/028,446 1996-10-10
US3254596P 1996-12-05 1996-12-05
US60/032,545 1996-12-05
US94618597A 1997-10-07 1997-10-07
US08/946,185 1997-10-07

Publications (1)

Publication Number Publication Date
WO1998015749A1 true WO1998015749A1 (fr) 1998-04-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1997/018358 WO1998015749A1 (fr) 1996-10-10 1997-10-10 Procedes et appareillage destines a reguler la pression et systemes de servodirection electro-hydraulique a flux sensiblement adapte

Country Status (1)

Country Link
WO (1) WO1998015749A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4573319A (en) * 1981-08-10 1986-03-04 Clark Equipment Company Vehicle hydraulic system with single pump
US4776165A (en) * 1985-12-05 1988-10-11 Honda Giken Kogyo Kabushiki Kaisha Clutch control system for hydraulically operated automotive transmission
US4944201A (en) * 1987-12-23 1990-07-31 Honda Giken Kogyo Kabushiki Kaisha Apparatus for controlling continuously variable automotive transmission

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4573319A (en) * 1981-08-10 1986-03-04 Clark Equipment Company Vehicle hydraulic system with single pump
US4776165A (en) * 1985-12-05 1988-10-11 Honda Giken Kogyo Kabushiki Kaisha Clutch control system for hydraulically operated automotive transmission
US4944201A (en) * 1987-12-23 1990-07-31 Honda Giken Kogyo Kabushiki Kaisha Apparatus for controlling continuously variable automotive transmission

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