Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
  • B62D6/02—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits responsive only to vehicle speed

Definitions

• My invention relates to power steering gears and to valves for controlling steering torque reaction.
• My invention comprises improvements in power steering systems of the kind shown, for example, in U.S. patent No. 3,877,540. Also of interest are U.S. patents Nos. 3,690,400; 3,692,137; 3,744,515 and 3,777,839, which illustrate the state of the art.
• a rotary valve comprising an inner valve member and a sur ⁇ rounding valve sleeve is located in a fluid circuit between a fluid motor and a power steering pump for establishing a variable pressure in the fluid motor, the output or driven member of which is connected to the steering shaft of the steering system to provide a power assist to the manual steering effort of the driver of the vehicle.
• the inner valve member which is connected to the steering shaft, is displaced angularly with respect to the valve sleeve, the latter being connected to the steering pinion or sector gear.
• reaction cylinders have been provided to resist relative displace ⁇ ment of the inner valve member with respect to its cooper- ating sleeve.
• Such devices are shown, for example, in patents Nos. 3,690,400; 3,692,137; 3,744,515 and 3,777,839. These devices comprise a reaction piston acting within a reaction pressure chamber, and the pressure that is made available to the reaction chamber is dependent upon speed thus providing relatively effortless steering perform ⁇ ance at low speeds and providing a stabilized steering performance during relatively high speed driving.
• 3,877,540 expands upon this early concept by providing a zero power assist when the valve members are in a rela- tively centered position, one with respect to the other, and that zero power assist condition remains until the resisting torque established by a speed sensitive pressure applied to the reaction pistons is overcome thereby allow ⁇ ing the steering valve to assume a relatively displaced position and to initiate a power assist operating mode.
• the improvements of my invention comprise a power steering mechanism having rotary valve elements wherein pressure reaction pistons are subjected to a steering pressure that is developed by the valve mechanism in cooperation with the positive displace ⁇ ment pump and flow control valve.
• the steering effort does not depend upon a governor pressure or a separate vehicle speed sensitive pressure that acts on the reaction pistons for the steering valve.
• the improved steering pressure sensitive power steering system of my invention creates a hydraulic reac ⁇ tion pressure that equals the power steering pump intake pressure while parking the vehicle thus causing light steering efforts in that operating mode.
• the magnitude of the steering effort while parking or while maneuvering the vehicle at low speeds is controlled only by the torsion bar that resists relative displacement of the inner valve member with respect to the valve sleeve.
• a speed sensor pump output pressure driven by a driven part of the vehicle driveline increases.
• the reaction pressure that is developed is sufficient to operate a selector valve thereby causing the reaction chambers in the steering gear itself to become ported to the steering pressure of the power steering pump.
• the reaction pressure increases accordingly.
• a vehicle speed sensing signal such as an automatic transmission governor pressure valve
• a vehicle speed sensing signal can be used to operate the selector valve thus causing the reaction chambers to be connected through the power steering pressure of the power steering pump as communication between the reaction chambers and the suction side of the pump is interrupted.
• Figure 1 shows in cross-sectional form and in partial schematic form a power steering gear mechanism together with a flow control valve and power steering pump for a wheeled automotive vehicle.
• Figure 2 is a cross-sectional view showing the reaction cylinders for the gear mechanism of Figure 1 as seen from the plane of section line 2-2 of Figure 1. - 4 -
• Figure 3 is a chart that shows the relationship between steering pressure and steering effort for the mechanism of Figure 1.
• Figure 4 is a modified form of my invention which includes a steering gear mechanism and a flow control valve that establishes a variable reaction pressure on the reac ⁇ tion cylinders for the steering gear mechanism.
• Figure 5 shows a modification of the proportional reaction pressure valve assembly of Figure 4 which effects a gradual increase in the proportionality of reaction pres ⁇ sure to steering pressure.
• Figure 6 is a chart showing the relationship bet ⁇ ween steering pressure and steering effort for a steering gear mechanism of the kind described here when it is pro- vided with a valve of the kind shown in Figure 5.
• Numeral 10 in Figure 1 designates a power steering gear housing. It is provided with a valve chamber 12 in which is positioned a rotary valve sleeve 14 and a cooperat- ing inner valve member 16.
• the valve 16 forms a part of or is connected to a steering shaft 18 which is adapted to be connected to a steering shaft to which the vehicle operater may apply steering torque.
• my patent No. 4,063,490 for a description of a typical rotary valve mechanism for use in controlling the steering pres ⁇ sures in a steering gear mechanism of the kind disclosed here.
• the inner valve member 16 has external valve lands 20 which register with internal valve lands 22 on valve sleeve 14. As the valve member 16 is displaced angularly with respect to sleeve 14, the lands 20 and 22 control the degree of communication between a steering pressure port 24 in the valve sleeve and each of two distribution passages 26 and 28, which extend to opposite sides of a pressure movable member such as a power steering piston, the latter in turn being connected to a vehicle steering linkage. Port 24 communicates with power steering pump pressure passage 30 that is connected to the output side of a power steering pump 32.
• a steering gear 34 is rotatably supported on the left hand end of the steering housing 10, and it is adapted to mesh with a gear rack as described in patent No. 4,063,490.
• Bushing 36 rotatably supports gear 34.
• One end of torsion rod spring 38 is pinned as shown at 40 to the right hand end of the gear 34.
• the opposite end of the torsion rod spring 38 is pinned at 42 to the driver controlled shaft 18.
• Valve sleeve 14 is adapted to be connected positively to the right hand end of gear 34.
• a positive driving connection between the sleeve 14 and the gear 34 is achieved by a hydraulic reaction mechanism generally identified in Figure 1 by reference numeral 44. That reaction mechanism will be described with respect to Figure 2 subsequently.
• a limited amount of lost motion is provided bet ⁇ ween the mechanism 44 and the right hand end of the gear 34 by means of an interlocking lug and slot device 46.
• torque is transmitted through the torsion rod 38 from the shaft 18 to the gear 34. If for some reason steering torque should exceed a predeter ⁇ mined value, torque then is transmitted directly from the shaft 18 and through a valve member 16 to the gear 34 through the lost motion connection.
• fluid pressure is distrib- uted from the passage 30 to the control passages 26 and 28. Pressure in passage 26 increases, and a corresponding decrease in pressure occurs in passage 28. If torque is applied in the opposite direction, the pressure in passage 28 increases; and a corresponding decrease occurs in passage 26.
• a bearing 48 maintains registry between the valve elements, and radial port 50 on the left hand side of the bearing 48 communicates with the central opening 52 in the valve member 16 through which the torsion rod 38 extends. That opening 52 communicates with exhaust port 54. Inter ⁇ nal porting, not shown, connects radial port 50 and region 56 to pressure return passage 58, which communicates with the intake side of the pump 32. Region 56 is located at the left hand side of the valve sleeve 14.
• a vehicle speed sensor pump 60 provides a vehicle speed pressure P ⁇ to passage 62. Pump 60 may be a pump that is connected through gearing to the tail shaft of a vehicle transmission. However, it may be replaced by a speed governor such as the governor of an automatic trans- mission in a vehicle driveline. The intake side of the pump 60 communicates with the supply passage 58 for the pump 32. Pump 32 is driven by the vehicle engine in known fashion.
• a pressure relief valve 64 comprises a valve spool that is biased in a left hand direction as seen in Figure 1 by valve spring 66. It controls the degree of communica ⁇ tion through a parallel flow passage 68 for the pump 60.
• a constant bleed orifice 70 bypasses the relief valve 64. The relief valve limits the pressure build up in the pas- sage 62 to a useful value.
• a selector valve 70 Arranged in parallel disposition with respect to the relief valve 64 is a selector valve 70. This comprises a valve spool having spaced lands 72 and 74. The left hand end of the land 72 communicates with passage 62. The right hand end of the land 74 communicates with the supply pas ⁇ sage 58. The selector valve is biased in a left hand direction by valve spring 76.
• a reaction element of generally rectangular shape forms a part of the reaction mechanism 44, as seen in Figure 2 at 82. It is connected directly to the rotary valve member 16 by means of a driving connection 84 seen in Figure 1.
• Figure 2 shows also a sleeve element 86 which surrounds the element 82 and which is formed with four reaction cylinders identified separately by reference characters 88, 90, 92 and 94. Each of these reaction cylinders receives a reaction piston as seen at 96, 98, 100 and 102.
• Each reaction piston is formed with a round nose which directly engages element 82 at a point offset from the central axis 104 of the valve mechanism.
• the selector valve 72 is shifted in a right hand direction against the opposing force of the spring 76 and against the opposing force of the suction pressure in passage 58. This interrupts communication between reaction pressure passage 80 and passage 78 and establishes communi ⁇ cation between passage 30 and passage 80. This causes an increase in pressure in the reaction chambers of Figure 2 thereby causing an increased steering effort during steer ⁇ ing maneuvers of the vehicle in such a high speed driving mode.
• the characteristic curve is as shown at 108.
• the slope of the characteristic curve changes dramatically as the steering mechanism changes from one operating mode to the other.
• the flow control valve shown in Figure 4 may be similar to the flow control valve illustrated, for example, in prior art patent No. 4,199,304 issued to Strikis, Halacka and Crain, which is assigned to the assignee of my invention.
• the steering gear and the valve arrangement in the Figure 4 construction are similar to that described with reference to Figure 1 and will not be repeated here.
• the supply passage for the reaction pressure is distributed to the reaction chambers of the Figure 4 construction through a reaction pressure passage 110 which corresponds to the passage 80 in the Figure 1 arrangement.
• Passage 10 is comprised in part by a hose 112 which, because of its flexibility, prevents transient and instantaneous pressure pulses to a magnitude beyond a desired value.
• Flow control valve 114 for the- power steering pump comprises valve spool 116 and spaced valve lands 118 and 120 of equal diameter. Spool 116 is biased, as seen in
• Pump discharge passage 124 communicates with the valve chamber 126 within which valve spool 116 is positioned. Pressure in passage 124 acts on the left hand side of valve land 118. A calibrated flow orifice 128 extends from the valve chamber 126 and acts to distribute flow to the high pressure inlet port for the steering gear which in Figure 4 is represented by passage 130. This passage corresponds to passage 30 in the embodiment of Figure 1. The inlet side of the power steering pump communi ⁇ cates with supply passage or suction pressure passage 132. This communicates with passage 134. Steering gear valve passage 134 corresponds to the passage 58 in the embodiment of Figure 1.
• a valve 114 includes a crossover or feedback passage 136 which distributes a venturi pressure from the calibrated orifice 128 to the end of the spring chamber 126 occupied by the spring 122. This makes the valve 114 respond to the rate of flow to the steering gear.
• the 114 responds also to pressure since the pressure in passage 124 acts on the left hand end of the valve spool 116.
• the flow control valve spool 116 moves to the right thereby bypassing excess fluid to the return passage 132.
• This ports the passage 110 to the steering pressure in passage 124.
• the reaction pressure P R in passage 110 acts on the appropriate pair of reaction pistons 96, 98, 100 and 102 thereby resisting rotation of the inner valve element with respect to the valve sleeve and increasing the steering effort in proportion to the magnitude of the pressure in passage 124.
• valve spool 116 ' is shown in a position such that port 138 is uncovered while port 130 continues to communicate with low pressure passage 132'. Port 138 communicates with the higher pressure in passage 124.
• the valve spool 116" is shown in an inter ⁇ mediate speed operating mode. At low speeds both ports 138 and 140 are covered so that the magnitude of the pressure in reaction pressure passage 110' is equal to the lower pressure in passage 132'. During operation in the highest speed mode both ports 138 and 140 are uncovered so that the reaction pressure in passage 110 is determined by the steering pressure in passage 124.
• the valve of Figure 5 provides a gradual increase in the steering effort as speed increases as it increases gradually the proportionality of P R to P.
• the improvements of this invention are useful for rack-and-pinion type power steering gear mechanisms as well as sector gear type steering mechanisms for automotive vehicles.

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

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22168007

Family Applications (1)

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Citations (5)

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• 1982
  • 1982-05-19 DE DE19823249477 patent/DE3249477C2/de not_active Expired
  • 1982-05-19 JP JP50209582A patent/JPS59500857A/ja active Pending
  • 1982-05-19 WO PCT/US1982/000687 patent/WO1983004008A1/en active Application Filing
  • 1982-05-19 GB GB08334052A patent/GB2130989B/en not_active Expired

Patent Citations (5)

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