JP2005306317A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain large steering auxiliary force without increasing power loss and energy loss in a state where excessive load is not locally applied. <P>SOLUTION: The power steering device is equipped with a steering shaft 2, an electric motor 4 as a first steering auxiliary means connected to the steering shaft through a speed reduction mechanism 22, a ball screw mechanism 5 converting the rotation of the steering shaft to the axial movement, and a sector gear 6 interlocking with the ball screw mechanism. The power steering device is provided with a second steering auxiliary means steer-assisting the sector gear 6 in addition to the electric motor 4. The second steering auxiliary means comprises a cylinder part 71 housing a ball screw mechanism 5 and a hydraulic supply circuit 9 which supplies pressure oil into the cylinder part 71 and axially moves the ball screw mechanism 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power steering device that reduces steering force by a driver of a vehicle, and more particularly to a power steering device that assists steering by two power sources.

  Conventionally, a steering device includes a steering shaft that is rotated by a steering input, a ball screw mechanism that converts rotation of the steering shaft into axial movement, and a sector gear that swings in conjunction with the ball screw mechanism. The ball nut of the ball screw mechanism is moved in the axial direction by the rotation of the steering shaft, the sector gear is swung by the movement of the ball nut in the axial direction, and the members such as the pitman arm are swung. The vehicle is steered by transmitting the movement to a steering wheel via a connecting member such as a tie rod or a knuckle arm (for example, see Patent Document 1).

  The power steering device is configured to apply a steering assist force by a hydraulic pressure or an electric motor to any member that forms a transmission path of an operation input from the steering shaft to the sector gear with respect to the steering device.

  Among such power steering devices, the hydraulic type has a large output and can be applied to large vehicles. However, it is necessary to use a hydraulic cylinder, hydraulic piping, etc., and the configuration is complicated, and it is practically impossible to store the hydraulic pressure used as a power source, so the hydraulic pump is always driven by the engine. The power loss and energy loss are large.

  On the other hand, the electric type has the advantage that the components need only be connected by wiring, the configuration is simple, and various controls can be easily performed, and the electric motor is driven when steering assistance is required. This is advantageous in terms of energy saving, but a large output cannot be obtained.

Recently, in order to facilitate steering of a large vehicle, a power steering device that generates a larger steering assist force is desired. In this case, if an attempt is made to obtain a large steering assist force by any one of the electric motor and the hydraulic assisting means, a part where an excessively large load is applied is generated, and there is a possibility that a problem in terms of strength may occur. There is. In the case of the hydraulic type, it is necessary to set the hydraulic pressure to an extremely high pressure, which further increases the size and weight of the device, and further increases the loss of power and energy. In the case of the electric type, it becomes necessary to supply an excessive driving current to the electric motor, and implementation is not easy.
JP-A-9-11921

  The problem to be solved by the present invention is to obtain a large steering assist force with little loss of power and loss of energy without applying an excessively large load locally.

  A power steering apparatus according to the present invention includes a steering shaft, an electric motor as first steering assisting means connected to the steering shaft via a speed reduction mechanism, and a ball screw that converts rotation of the steering shaft into axial movement. And a sector gear swinging in conjunction with the ball screw mechanism, and a second steering assist means for assisting the steering of the sector gear separately from the first steering assist means. Is.

  According to the above configuration, when the driver operates the steering member, the rotational power of the electric motor serving as the first steering assist means is transmitted to the sector gear via the speed reduction mechanism, the steering shaft, and the ball screw mechanism, and the sector The gear is assisted in steering, and the sector gear is assisted in steering by the second steering assist means. Therefore, the steering force of the driver is assisted by the steering assist means, and even a large vehicle can be lightly steered with a small operating force.

  In this case, as in the conventional power steering apparatus, when a large steering assist force is obtained by the steering assist means of either the electric motor or the hydraulic pressure alone, a part where an excessively large load is applied is generated, and the strength is increased. Problems may occur. Further, in the case of an electric motor, it is necessary to supply an excessive drive current to this, and in the case of hydraulic pressure, it is necessary to set this to an extremely high pressure, and neither is easy to implement. On the other hand, in the present invention, since the first and second steering assisting means share the steering assisting force, there is no portion where an excessively large load is applied locally, causing a problem in strength. And can be easily implemented.

  Further, at least one of the two steering assist means is an electric motor, and this electric motor only needs to be driven when steering assist is necessary, so that there is little power loss, which is advantageous in terms of energy saving. It is.

  In the power steering apparatus having the above-described configuration, the second steering assisting unit is configured to move the ball nut of the ball screw mechanism in the axial direction by supplying pressure oil into the cylinder portion that houses the ball screw mechanism and the cylinder portion. And a hydraulic pressure supply circuit. In such a configuration, since the hydraulic oil is supplied from the hydraulic pressure supply circuit into the cylinder portion and the ball nut is moved in the axial direction, a steering assist force for swinging and rotating the sector gear is thereby generated. The hydraulic pump constituting the hydraulic pressure supply circuit is desirably a pump driven by an electric motor in order to reduce power loss and energy loss.

  In the power steering apparatus having the above-described configuration, the second steering assisting unit can be configured by another sector gear provided coaxially with the sector gear and another electric motor that swings the other sector gear. . In such a configuration, by driving another electric motor in the second steering assisting means, the other sector gear can be swung to generate a steering assisting force. Since the two electric motors by the two steering assisting units are used, the configuration is simplified and complicated control can be performed relatively easily as compared with the case of using the hydraulic pressure.

  According to the present invention, the steering assist force can be increased and the steering operation of a large vehicle can be performed lightly without applying an excessive load locally and without increasing power loss or energy loss. Can be.

  A power steering apparatus according to the best mode of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing the power steering apparatus together with a related vehicle configuration, and a main part is along an axial direction. The cross section is shown.

  This power steering apparatus includes a steering shaft 2 having one end connected to a steering wheel (handle) 1 as a steering member, and a set of two rotation sensors that operate as a torque sensor that detects steering torque applied to the steering shaft 2. 31, 32, an electric motor 4 as first steering assisting means, a ball screw mechanism 5 for converting the rotation of the steering shaft 2 into axial movement, and a sector gear interlocked with a ball nut 51 of the ball screw mechanism 5 6, a cylinder housing 7 that accommodates the sector gear 6 and the ball screw mechanism 5, a pitman arm 8 fixed to the shaft (gear shaft 6 a) of the sector gear 6 outside the cylinder housing 7, and a second steering A hydraulic pressure supply circuit 9 as auxiliary means, and an electronic control unit (ECU) 1 for controlling the operation of the electric motor 4 and the hydraulic pressure supply circuit 9 It includes bets, pitman arm 8 is connected to the wheel 12 for steering via a coupling member 11 consisting of a tie rod and a knuckle arm or the like.

  Hereinafter, in the description of the main part of the illustrated power steering apparatus, the side closer to the steering wheel 1 is referred to as the upper side or the upper end, and the side closer to the wheel 12 is referred to as the lower side or the lower end in accordance with the mounting state of the power steering apparatus in the vehicle. .

  The lower part of the steering shaft 2 is composed of an intermediate shaft 13, a cylindrical input shaft 14, a torsion bar 15, and a cylindrical output shaft 16 in order from the steering wheel 1 side. It is rotatably supported inside the divided sensor housings 171 and 172.

  The input shaft 14 is connected to the lower end portion of the intermediate shaft 13 by a pin 18 penetrating in the radial direction together with the torsion bar 15 inserted in the cylindrical shape. The torsion bar 15 has a long and narrow torsional region at its middle part, and has a large-diameter upper end connected to the intermediate shaft 13 and the input shaft 14 as described above, and also a large-diameter lower end. The portion is inserted into the cylindrical shape of the output shaft 16 and connected to the output shaft 16 by a pin 19 that penetrates in the radial direction. On the outer periphery of the torsion bar 15, the input shaft 14 extends to the lower end side of the torsion bar 15, and the output shaft 16 extends to the upper end side of the torsion bar 15. The outer circumferences face each other in the axial direction.

  One rotation sensor 31 constituting the torque sensor is provided inside the upper sensor housing 171 and faces the pulsar ring 20 attached to the outer periphery of the input shaft 14. The other rotation sensor 32 is provided inside the lower sensor housing 172 and faces the pulsar ring 21 attached to the outer periphery of the output shaft 16. The sensor signals of these two rotation sensors 31 and 32 are input to the ECU 10. The ECU 10 detects the steering torque applied to the steering shaft 2 from the rotational phase difference between the input shaft 14 and the output shaft 16 detected by the rotation sensors 31 and 32.

  The electric motor 4 serving as the first steering assist means is mounted on the upper sensor housing 171 with the rotation shaft 4a facing downward. A small-diameter drive gear 221 is coaxially provided on the rotating shaft 4a of the electric motor 4, and a large-diameter driven gear 222 that meshes with the drive gear 221 is coaxially attached to the output shaft 16. The rotation of the rotary shaft 4 a of the motor 4 is decelerated by the speed reduction mechanism 22 including the drive gear 221 and the driven gear 222 and transmitted to the output shaft 16. The speed reduction mechanism 22 including the drive gear 221 and the driven gear 222 is housed between the upper sensor housing 171 and the lower sensor housing 172.

  The ball screw mechanism 5 includes a ball screw shaft 52, a large number of balls 53, and a ball nut 51 that meshes with the ball screw shaft 52 via these balls 53.

  The ball screw shaft 52 is coaxially coupled to the output shaft 16 by coupling means such as press fitting or serration fitting, and is rotatably supported by a lid member 23 that closes the upper end opening of the cylinder housing 7. The ball 53 is interposed between a screw groove 52 a on the outer periphery of the ball screw shaft 52 and a screw groove 51 a on the inner periphery of the ball nut 51, for example, through a reflux passage (not shown) formed in the wall thickness of the ball nut 51. It comes to circulate. The ball nut 51 is formed with a rack 54 that meshes with the sector gear 6 at a part of the outer periphery, and the outer peripheral surface other than the portion where the rack 54 is formed is a cylindrical outer peripheral surface with a non-circular cross section. It has a piston shape. The lower end opening of the ball nut 51 is closed with a cap 24.

  The cylinder housing 7 is formed by connecting a cylindrical cylinder part 71 having a non-circular cross section along the axial direction of the ball screw shaft 52 and a gear accommodating part 72 for accommodating the sector gear 6 so as to communicate with each other. It is. The ball nut 51 is closely fitted as a piston inside the cylinder portion 71 and can slide in the axial direction in a state where the hydraulic chambers 25 and 26 exist on both sides of the cylinder portion 71 in the axial direction.

  The hydraulic pressure supply circuit 9 includes an electric hydraulic pump 91, a switching valve 92, an oil tank 93, and the like, and supplies pressure oil from the switching valve 92 to the hydraulic chambers 25 and 26 in the cylinder housing 7 through pipes 94 and 95. It has become. The switching valve 92 is provided with a solenoid 96 for switching and driving it. The cylinder portion 71 and the hydraulic pressure supply circuit 9 constitute second steering assist means.

  The ECU 10 controls driving of the electric motor 4, the electric motor 91 a of the electric hydraulic pump 91, and the solenoid 96 for the switching valve 92 based on output signals from sensors such as the rotation sensors 31 and 32. Sensors that supply output signals to the ECU 10 include a vehicle speed sensor and an engine rotation sensor in addition to the two rotation sensors 31 and 32 constituting the torque sensor. Although not particularly illustrated, the ECU 10 is configured with a microcomputer as the center, and includes peripheral circuits such as a sensor interface, a motor drive circuit, and a solenoid drive circuit.

  In the above configuration, the steering force applied to the steering wheel 1 by the driver is transmitted from the upper part of the steering shaft 2 to the ball screw shaft 52 from the intermediate shaft 13, the input shaft 14, the torsion bar 15, and the output shaft 16. , The rotation of the ball screw shaft 52 is converted into the movement of the ball nut 51 in the axial direction. As the ball nut 51 moves in the axial direction, the sector gear 6 swings and rotates, and the pitman arm 8 swings. This movement is transmitted to the steering wheel 12 as a steering force.

  In this case, the steering torque applied to the steering wheel 1 is detected as a rotational phase difference between the input shaft 14 and the output shaft 16 from the sensor signals of the two rotation sensors 31 and 32. In accordance with the magnitude of the steering torque detected in this way, the ECU 10 requires each of the first electric motor 4, the motor 91a of the electric hydraulic pump 91, and the solenoid 96 for the switching valve 92 to operate. Supply current.

  When the rotary shaft 4a of the electric motor 4 rotates, the rotational power is decelerated by the speed reduction mechanism 22 and transmitted to the output shaft 16, thereby supplementing the driver's steering force.

  Further, when pressure oil is supplied to one of the two hydraulic chambers 25 and 26 in the cylinder housing 7 by driving the electric hydraulic pump 91 and switching operation of the switching valve 92, the ball oil 51 is generated by the pressure oil. Slides in one axial direction, and the gear shaft 6 a is swung and rotated by the meshing of the rack 54 and the sector gear 6. This also supplements the steering force by the driver.

  As described above, the steering assist force of the electric motor 4 constituting the first steering assist means and the steering assist force due to the hydraulic pressure constituting the second steering assist means are added to the steering force of the driver. The user's steering force is small, and even a large vehicle can be steered easily.

(Other embodiments)
2 and 3 show another embodiment of the present invention. FIG. 2 is a cross-sectional view along the axial direction of the main part of a power steering apparatus according to another embodiment, and FIG. It is sectional drawing along line (3)-(3).

  In this embodiment, the portion (the portion shown in the upper half of FIG. 2) in which the first electric motor 4 as the first steering assist means is provided below the steering shaft 2 is the same as that of the embodiment of FIG. The lower part of the steering shaft 2 includes an intermediate shaft 13, a cylindrical input shaft 14, a torsion bar 15, and a cylindrical output shaft 16. One rotation sensor 31 constituting the torque sensor is provided at a position facing the outer peripheral portion of the input shaft 14, and the other rotation sensor 32 is provided at a position facing the outer peripheral portion of the output shaft 16. The rotation of the rotary shaft 4 a of the first electric motor 4 is decelerated by the speed reduction mechanism 22 including the small-diameter drive gear 221 and the large-diameter driven gear 222 and transmitted to the output shaft 16. In addition, about the part illustrated in the upper half part of FIG. 2, the code | symbol same as FIG. 1 is attached | subjected and detailed description is abbreviate | omitted.

  In the lower half of FIG. 2, the ball screw shaft 52 constituting the ball screw mechanism 5 is coaxially coupled to the output shaft 16 while being accommodated in the gear housing 27, and the portion on the output shaft 16 side is the gear A lid member 28 that closes an upper end opening portion of the housing 27 and a lower end portion are rotatably supported by a bottom portion of the gear housing 27, respectively. The ball nut 51 of the ball screw mechanism 5 meshes with the ball screw shaft 52 via a large number of balls 53, and a rack 54 is formed on a part of the outer periphery. The ball 53 circulates through a tube 55 provided on the outer periphery of the ball nut 51.

  The gear housing 27 is formed by connecting a cylindrical housing portion 271 having a shape along the axial direction of the ball screw shaft 52 and a gear housing portion 272 for housing the sector gear 6 so as to communicate with each other. Between the cylindrical housing portion 271 and the gear housing portion 272, the rack 54 of the ball nut 51 and the sector gear 6 are engaged with each other.

  As shown in FIG. 3, the gear shaft 6 a integrally having the sector gear 6 is rotatably supported by a gear housing portion 272 of the gear housing 27 by a bush bearing 29 and extended to the outside of the gear housing portion 27. Thus, another sector gear 30 constituting the second steering assist means is fixed to the middle part of the extension part. A pitman arm indicated by reference numeral 8 in FIG. 1 is attached to the distal end of the extension portion of the gear shaft 6a. The inner end portion of the gear shaft 6a is received by the receiving member 33, and the position in the axial direction is restricted.

  On the other hand, two motor housings 341 and 342 are provided outside the gear housing portion 272 of the gear housing 27, and another electric motor as second steering assisting means is provided on one side 342 of the motor housings 341 and 342. A motor 35 is mounted, and its rotating shaft 35a is parallel to the gear shaft 6a. A speed reduction mechanism 36 including a planetary gear mechanism is connected to the rotation shaft 35 a of the electric motor 35.

  The speed reduction mechanism 36 includes a sun gear 361, a plurality of planet gears 362 that mesh with the sun gear 361, a carrier 363 that rotatably supports the planet gear 362, and an inner gear that meshes with the planet gear 362 on the outer peripheral side of the planet gear 362. And a tooth ring 364. The sun gear 361 is provided coaxially with the rotating shaft 35 a of the electric motor 35, the internal tooth ring 364 is fixed to the motor housing 342, and the shaft of the carrier 363 serves as the output shaft, and the small-diameter drive that meshes with the sector gear 30. A gear 37 is provided.

  The sector gear 30 and the drive gear 37 that meshes with the sector gear 30 as a driven gear are accommodated between the two motor housings 341 and 342. The second electric motor 35 and the speed reduction mechanism 36 on the rotating shaft 35a side are mounted on a cylindrical mounting portion 342a formed on one of the two motor housings 341 and 342.

  The electric motor 4 that is the first steering assist means and the electric motor 35 that is the second steering assist means are controlled by the ECU 10 that captures sensor signals from the rotation sensors 31 and 32 and the like.

  In the above configuration, the steering force applied to the steering wheel 1 by the driver is transmitted from the upper part of the steering shaft 2 to the ball screw shaft 52, and the rotation of the ball screw shaft 52 is converted into the movement of the ball nut 51 in the axial direction. With the movement of the shaft 51 in the axial direction, the sector gear 6 swings and rotates, and this movement is transmitted to the wheel 12 as a steering force via a member such as the pitman arm 8.

  In this case, the steering torque applied to the steering wheel 1 is detected by the sensor signals of the two rotation sensors 31 and 32. The ECU 10 supplies a required current to each of the first electric motor 4 and the second electric motor 35 so as to operate according to the magnitude of the detected steering torque.

  The output shaft 16 is rotationally driven by the rotation of the rotating shaft 4a of the electric motor 4, thereby supplementing the steering force by the driver. Further, when the rotating shaft 35a of the electric motor 35 rotates, the rotation is decelerated by the speed reducing mechanism 36 formed of a planetary gear mechanism, and then transmitted to the driving gear 37, from the driving gear 37 to the sector gear 30, and to the gear shaft. 6a is swung and rotated. This also supplements the steering force by the driver.

  Thus, since the steering assist force by the electric motor 4 as the first steering assist means and the steering assist force by the electric motor 35 as the second steering assist means are added to the steering force of the driver, The steering force of the person is greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The power steering device which concerns on the best form of this invention is a schematic block diagram shown with a related vehicle structure, and the principal part is shown in cross section along an axial direction. Sectional drawing along the axial direction of the principal part of the power steering apparatus which concerns on other embodiment of this invention. Sectional drawing along the (3)-(3) line | wire of FIG.

Explanation of symbols

1 Steering wheel (steering member)
2 Steering shaft 31, 32 Rotation sensor (torque sensor)
4 Electric motor (first steering assist means)
5 Ball screw mechanism 51 Ball nut 52 Ball screw shaft 54 Rack 6 Sector gear 6a Gear shaft 7 Cylinder housing 71 Cylinder portion (second steering assisting means)
9 Hydraulic supply circuit (second steering assist means)
22 Deceleration mechanism 30 Sector gear (second steering assist means)
35 Electric motor (second steering assist means)
36 Deceleration mechanism

Claims (3)

  A steering shaft, an electric motor as a first steering assist means coupled to the steering shaft via a speed reduction mechanism, a ball screw mechanism for converting rotation of the steering shaft into axial movement, and the ball screw mechanism A power steering apparatus comprising: a sector gear that swings in conjunction with the second steering assist means, and a second steering assist means that assists the steering of the sector gear separately from the first steering assist means.   The second steering assist means includes a cylinder portion that houses the ball screw mechanism, and a hydraulic pressure supply circuit that supplies pressure oil into the cylinder portion to move a ball nut of the ball screw mechanism in the axial direction. The power steering apparatus according to claim 1. The said 2nd steering assistance means contains another sector gear provided coaxially with the said sector gear, and another electric motor which rocks the said another sector gear, It is characterized by the above-mentioned. The power steering apparatus described.

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