JP2008265648A - Power steering device - Google Patents

Abstract

A power steering apparatus including a disturbance detection sensor capable of directly detecting a frequency component of disturbance is provided.
A disturbance detection sensor 27 of an electric power steering apparatus 1 fixes a magnet 25 to a rack shaft 8 and corresponds to a magnet 25 on an outer peripheral portion of a rack housing (not shown) covering the rack shaft 8. The coil 26 is arranged in the configuration. As a result, when the rack shaft 8 is vibrated and displaced in the axial direction due to disturbance of the steering system, the magnet 25 and the coil 26 are relatively vibrated and displaced in the axial direction. An induced electromotive force corresponding to is generated. Therefore, the induced electromotive force generated in the coil 26 is detected, and the pushing force of the rack guide 19 is controlled using the induced electromotive force as a feedback signal, thereby suppressing the influence of the disturbance received by the steering system.
[Selection] Figure 2

Description

  The present invention relates to a power steering device that assists steering of steered wheels.

As a power steering device, an electric power steering device, a hydraulic power steering device, and the like are widely known. For example, an electric power steering device is an apparatus in which an electric motor generates an auxiliary torque corresponding to the magnitude of a steering torque and transmits the auxiliary torque to a steering system to reduce a steering force that a driver steers. However, depending on the road surface state where the vehicle travels, unpleasant vibrations may be transmitted to the steering wheel due to disturbance from the road surface.
Therefore, in order to solve such problems, electric power steering that suppresses vibration and disturbance of the steering system by extracting and removing the vibration frequency component of the vehicle so that unpleasant vibration is not transmitted to the steering wheel. An apparatus is disclosed (for example, see Patent Document 1). In addition, an electric power steering device is disclosed in which a frequency band component of disturbance is extracted and removed by a low-pass filter so that comfortable steering performance can be obtained (see, for example, Patent Document 2).
JP 2006-335228 A (paragraphs [0017] to [0019], FIG. 1) JP 2006-199219 A (paragraphs [0019], [0030], FIG. 1 and FIG. 2)

However, in the disturbance detection sensor of the conventional electric power steering device, after shaping the rotation speed signal of a clutch or the like detected in the vehicle steering system, the pulse period sampled at a constant period is measured to calculate the frequency, Whether or not it is a disturbance is judged by the magnitude of the frequency. This complicates the circuit and system for waveform shaping and frequency calculation of the detection signal of the disturbance detection sensor, and as a result, the electric power steering apparatus equipped with the disturbance suppression system becomes complicated and expensive. There was a point.
Further, in the electric power steering control device described in Patent Document 1 and the control device for the electric power steering device described in Patent Document 2, means for extracting the vibration frequency component of the disturbance and means for removing the vibration Since complicated processing means are provided, there is a problem that the mechanism for suppressing disturbance becomes complicated and expensive.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a power steering apparatus including a disturbance detection sensor that can directly detect a frequency component of disturbance.

  In order to solve the above problems, a power steering apparatus according to the present invention is a rack-and-pinion type power steering apparatus that applies a steering assist force in accordance with a steering force input to a steering wheel, and is a part of a rack shaft. And a coil provided on the outer periphery of the position corresponding to the magnetized portion. When the rack shaft is displaced, the magnetized portion and the coil move relative to generate an induced electromotive force in the coil. It comprises a disturbance detection sensor, and disturbance suppression means for suppressing the influence of the disturbance received by the steering system based on the induced electromotive force generated by the disturbance detection sensor.

  According to this configuration, the disturbance detection sensor composed of a magnetized portion such as a magnet and a coil uses the induced electromotive force generated in the coil due to the relative movement of the magnetized portion and the coil caused by the displacement of the rack shaft as a disturbance signal as it is. Can be caught. Therefore, the disturbance suppression means can suppress the disturbance of the steering system using the disturbance signal (that is, the induced electromotive voltage) received from the disturbance detection sensor.

  Preferably, in the power steering apparatus according to the present invention, the disturbance suppression unit further increases the pressing force pressing the rack shaft as the induced electromotive force generated by the disturbance detection sensor increases. It is characterized by adjusting the friction acting on the shaft. This suppresses an unpleasant signal from being transmitted to the steering wheel operated by the driver.

  According to the first aspect of the present invention, an induced electromotive force generated by electromagnetic induction using a coil and a magnet is detected, and an induced electromotive force corresponding to the frequency based on the displacement speed of the steering system and the number of axial movements of the rack shaft is detected. The voltage level of power is calculated as a disturbance. And the disturbance of a steering system is suppressed according to the voltage level of this induced electromotive force. For this reason, it is possible to directly detect the frequency component of the disturbance and suppress the disturbance without providing an additional circuit such as a waveform shaping circuit or a filter. Therefore, it is possible to realize a power steering device that is inexpensive and has high added value.

  According to the second aspect of the present invention, since the disturbance suppression control of the steering system is performed by adjusting the pressing force of the rack guide or the like, the disturbance suppression is performed not only in the electric power steering apparatus but also in the hydraulic power steering apparatus. It can be performed. Furthermore, since disturbance suppression control can be performed only with a disturbance detection sensor consisting of a coil and a magnet and an adjustment motor for pressing the rack guide, the disturbance of the steering system can be suppressed with a simple and inexpensive power steering device. Is possible.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(Electric power steering device 1)
First, an electric power steering apparatus 1 according to an embodiment of the present invention will be described.
FIG. 1 is an overall configuration diagram showing an outline of the operation of an electric power steering apparatus 1 according to an embodiment of the present invention.

  The electric power steering apparatus 1 has a steering wheel 2, and the steering wheel 2 is connected to a pinion shaft 4 via a steering shaft 3. Steering torque generated by the driver operating the steering wheel 2 is transmitted to the pinion shaft 4 via the steering shaft 3. For example, a magnetostrictive torque sensor 5 and torque transmission means 6 for detecting steering torque acting on the steering system are attached to the pinion shaft 4. The torque transmission means 6 is connected to an electric motor 7 such as a brushless motor for applying auxiliary torque to the steering system.

  The electric power steering apparatus 1 has a so-called rack and pinion type configuration. That is, the pinion 4A provided at the lower end of the pinion shaft 4 is meshed with the rack teeth 8A formed on the rack shaft 8, and when the pinion shaft 4 rotates, the rotation is displaced in the axial direction of the rack shaft 8. The wheels 9 and 9 are steered after conversion. The torque sensor 5 is connected to the control device 10 and outputs a steering torque signal T. The control device 10 calculates the auxiliary torque based on the steering torque signal T output from the torque sensor 5 and outputs the motor control voltage Vo to the motor 7 to control the motor 7.

FIG. 2 is a cross-sectional view of a main part showing the electric power steering apparatus 1.
The torque transmission means 6 has a worm wheel 11 fixed coaxially to the pinion shaft 4. A worm shaft 12 is connected to the electric motor 7, and a worm gear 13 provided on the worm shaft 12 is engaged with the worm wheel 11. When the electric motor 7 is driven and the worm shaft 12 rotates, the worm wheel 11 meshed with the worm gear 13 rotates, and the pinion shaft 4 rotates together with the worm wheel 11. Thus, the auxiliary torque from the electric motor 7 is transmitted to the pinion shaft 4 and is transmitted from the rack shaft 8 to the steering system via the pinion shaft 4.

  On the other hand, the rack shaft 8 is disposed inside a rack housing 14 formed of a nonmagnetic material such as an aluminum alloy. Both ends of the rack housing 14 are covered with boots 15 and 15 to protect the inside of the rack housing 14 and prevent dust and the like from being mixed. Tie rods 16 and 16 are connected to both ends of the rack shaft 8, respectively. The tie rods 16 and 16 are connected to the wheels 9 and 9 (see FIG. 1) via a knuckle (not shown).

  Further, reinforcing ribs 17 are formed on the outside of the rack housing 14 to enhance the rigidity of the rack housing 14 in the bending direction. Further, an attachment portion 18 for attaching the rack housing 14 to a chassis (not shown) is formed at a lower portion of the rack housing 14 and slightly closer to one end side (left side in the drawing) from the intermediate portion.

In the rack housing 14, first support means 21, second support means 22, and third support means 23 that support the rack shaft 8 are disposed.
The first support means 21 supports one end side (the left side in the figure) of the rack shaft 8, and meshes with the pinion 4 </ b> A formed at the lower end of the pinion shaft 4 and the rack teeth 8 </ b> A formed on the rack shaft 8. It is configured. A rack guide 19 is provided on the back side of the rack teeth 8A to press the rack shaft 8 from the back toward the pinion 4A.

The second support means 22 is constituted by a support bearing provided on the other end side (the right side in the figure) of the rack shaft 8, and the other end side of the rack shaft 8 extends along the axial direction of the rack shaft 8 (the left and right sides in the figure). (In the direction) is slidably supported.
The third support means 23 is configured by a support bearing provided between one end side and the other end side (intermediate portion) of the rack shaft 8, and the intermediate portion between the one end side and the other end side of the rack shaft 8 is the rack shaft 8. Is supported so as to be slidable along the axial direction (along the horizontal direction in the figure).

  Further, as shown in part B, a recess is provided in a part of the rack shaft 8, and a cylindrical magnet (magnetization part) 25 is fitted in the recess. A gap may be provided in the rack housing 14 so that the magnet (magnetization portion) 25 does not interfere, and the magnet 25 may be simply attached to the surface of the rack shaft 8. The magnet 25 has, for example, a cylindrical shape, and one end (the left side in the figure) is magnetized to the N pole and the other end (the right side in the figure) is magnetized to the S pole. (Right side of the figure) may be magnetized to the N pole.

  A coil 26 wound around a bobbin (not shown) is fitted on the outer periphery of the rack housing 14 corresponding to the portion of the rack shaft 8 into which the cylindrical magnet 25 is fitted. That is, since the magnet 25 is fixed to the rack shaft 8 and the coil 26 is fixed to the rack housing 14, the relative positional relationship between the magnet 25 and the coil 26 does not change when the electric power steering apparatus 1 is stationary. As described above, the disturbance detection sensor 27 is formed by the magnet 25 and the coil 26 in the portion B shown in FIG.

  The coil 26 may be formed on the inner surface of the rack housing 14 so as to face the magnet 25. Further, the disturbance detection sensor 27 is not only based on the combination of the magnet 25 and the coil 26, but also physically detects the displacement of the rack shaft 8, and includes an electrode and a voltage application circuit (both not shown), and has a capacitance. It is also possible to detect the displacement of the rack shaft 8 based on the change of.

(Disturbance detection sensor 27)
Next, the disturbance detection sensor 27 will be described in detail.
3 is a cross-sectional view showing the disturbance detection sensor 27 in detail. FIG. 3A is a cross-sectional view taken along a plane along the axial direction of the rack shaft 8 in FIG. 3 (b) shows a CC cross section shown in FIG. 3 (a). FIG. 4 is an enlarged perspective view of a portion B (disturbance detection sensor 27) shown in FIG.

  As shown in FIG. 3A, the magnet 25 is housed in the recess of the rack shaft 8. As shown in FIG. 3B, the magnet 25 itself has a cylindrical portion divided into two parts. Therefore, as shown in FIG. 3 (a), after the same polarity of the semi-cylindrical magnets 25 divided into two are combined and stored in the recesses of the rack shaft 8, they are fixed as the magnets 25 with an adhesive or the like. A magnet 25 is arranged on a part of the rack shaft 8 with substantially the same outer diameter as the rack shaft 8 other than the recess. For example, as shown in FIG. 4, a magnet 25 having an N pole on the left side and an S pole on the right side is arranged on a part of the rack shaft 8.

  Returning to FIG. 2, when the electric power steering apparatus 1 is in the neutral position, the coil 26 is disposed on the outer periphery of the rack housing 14 corresponding to the position of the magnet 25. The coil 26 is disposed by accommodating the coil 26 wound around the cylindrical bobbin from the right side of the rack housing 14 before fitting the boot 15 on the right side of the rack housing 14, and corresponding to the position of the magnet 25. By the way, the coil 26 is fixed to the outer periphery of the rack housing 14 with an adhesive or the like. Thereafter, the right boot 15 of the rack housing 14 is fitted. In addition, if the relative position of the magnet 25 and the coil 26 is marked on the outside of the rack housing 14 in advance, the coil 26 can be easily stored in a predetermined position.

  As shown in FIG. 3A, when the coil 26 is arranged corresponding to the magnet 25 fixed to the rack shaft 8 and the disturbance detection sensor 27 is formed, the magnet is caused by the reciprocating movement (displacement) of the rack shaft 8. 25 moves (displaces) in the longitudinal direction of the coil 26.

  That is, as shown in FIG. 4, when the magnet 25 reciprocates with respect to the coil 26, the magnetic flux φ changes inside the coil 26 and an induced electromotive force is generated in the coil 26. Here, when the number of turns of the coil 26 is N, the induced electromotive force e generated in the coil 26 can be expressed by e = N × (dφ / dt). That is, when the magnet 25 reciprocates, the induced electromotive force e of the coil 26 increases as the change in magnetic flux per unit time increases.

  In other words, the induced electromotive force e of the coil 26 increases as the displacement speed of the rack shaft 8 (see FIG. 2) increases. In addition, the higher the displacement speed of the rack shaft 8, the greater the vibration transmitted to the steering wheel 2 via the steering shaft 3 in the electric power steering apparatus 1 (see FIG. 1). Therefore, when the vibration frequency of the disturbance transmitted from the steering system to the rack shaft 8 is increased, the displacement speed of the rack shaft 8 is increased, the induced electromotive force e of the coil 26 is increased, and the steering wheel 2 (FIG. 1). The vibration transmitted to (see) also increases. Therefore, if the magnitude of the induced electromotive force e of the coil 26 is detected as the magnitude of the disturbance, and feedback control is performed so that the friction of the steering shaft 3 increases according to the induced electromotive force e, the steering wheel 2 caused by the disturbance Can be suppressed.

  For example, when traveling on a road surface covered with gravel, the frequency of disturbance received from the road surface is about 10 to 20 Hz. Accordingly, returning to FIG. 2, the induced electromotive force e of the coil 26 when the rack shaft 8 is displaced at this frequency (that is, 10 to 20 Hz) is regarded as a disturbance, and this induced electromotive force e is used as a feedback signal to determine the rack guide 19 If the pressing force is controlled to be increased, the friction of the steering wheel 2 can be suppressed by increasing the friction of the steering shaft 3.

  In the steering performed by the driver during normal driving of the vehicle, the displacement speed of the rack shaft 8 is much slower than the displacement speed due to the disturbance described above, and the change frequency of the magnetic flux φ due to the relative movement of the magnet 25 and the coil 26 is about 3 to 4 Hz. is there. Therefore, since the value of (dφ / dt) indicating the temporal change of the magnetic flux is extremely small, the induced electromotive force e of the coil 26 is also extremely small. Therefore, since the displacement speed of the rack shaft 8 is slow in normal steering, the friction of the steering shaft 3 is small and the feedback control amount by the induced electromotive force e is small. For this reason, even if the pressing force of the rack guide 19 is weak, the vibration transmitted to the steering wheel 2 is small. At this time, since the steering force of the steering wheel 2 is light, the steering burden imposed by the driver can be reduced.

  In other words, the disturbance detection sensor 27 of the present embodiment has the magnet 25 disposed on a part of the rack shaft 8 and the coil 26 is disposed facing the magnet 25 on the outer peripheral portion of the rack housing 14 that covers the rack shaft 8. It is the composition made to do. When the rack shaft 8 is displaced in the left-right direction in accordance with the steering displacement of the steering shaft 3, the magnet 25 moves (displaces) in the coil 26.

  With such a mechanism, when the rack shaft 8 is displaced, an induced electromotive force e is generated in the coil 26 due to electromagnetic induction by the coil 26 and the magnet 25. Since this induced electromotive force e changes according to the displacement speed of the rack shaft 8, the magnitude of the induced electromotive force generated in the coil 26 becomes the displacement speed of the rack shaft 8 (that is, the magnitude of the disturbance of the steering system). . Therefore, by controlling the pressing force of the rack guide 19 based on the value of the induced electromotive force, the friction transmitted to the steering wheel 2 (see FIG. 1) can be suppressed by adjusting the friction of the steering shaft 3. it can.

  In the electric power steering apparatus 1 of the present embodiment, a magnet 25 is fixed to the rack shaft 8, and a coil 26 is disposed at a position corresponding to the magnet 25 on the outer peripheral portion of the rack housing 14 covering the rack shaft 8. For this reason, when the rack system 8 vibrates in the axial direction due to the disturbance of the steering system, the relative position between the magnet 25 and the coil 26 vibrates and displaces in the axial direction of the rack shaft 8. Generates an induced electromotive force having a frequency corresponding to the vibration frequency due to the disturbance. Therefore, the induced electromotive force generated in the coil 26 is detected, the induced electromotive force is fed back, and the pressing force of the rack guide 19 is controlled according to the frequency and magnitude of vibration to suppress disturbance. . That is, as the induced electromotive force of the frequency component corresponding to the disturbance is increased, the pressing force of the rack guide 19 is controlled so that the disturbance received by the steering system is transmitted to the steering wheel 2 via the steering shaft 3. Can be suppressed.

(Disturbance suppression system)
Next, a specific embodiment of a disturbance suppression system using the disturbance detection sensor 27 will be described.
FIG. 5 is a cross-sectional view taken along line AA of the electric power steering apparatus 1 shown in FIG.
In addition, the overlapping description is abbreviate | omitted using the same code | symbol.

  First, a mechanism for preventing unnecessary vibration from being transmitted to the steering wheel 2 (see FIG. 1) by pressing the rack teeth 8A of the rack shaft 8 against the pinion 4A so as not to cause friction in the steering shaft 3 will be described. The rack guide 19 includes a concave tip 64 of a guide portion 61 for contacting the back surface of the rack shaft 8, and an adjustment bolt 63 that presses the concave tip 64 toward the rack shaft 8 via a compression spring 62. ing.

  According to the rack guide 19 having this configuration, the concave tip 64 presses the rack shaft 8 by pressing the guide portion 61 with an appropriate pressing force via the compression spring 62 by the adjusting bolt 63 screwed into the rack housing 14. Thus, the rack teeth 8A can be pressed against the pinion 4A. As a result, the teeth of the rack teeth 8A and the teeth of the pinion 4A mesh with each other without loosening, so that the vibration of the rack shaft 8 due to disturbance does not give friction to the steering shaft 3. As a result, the disturbance generated in the rack shaft 8 is suppressed from being transmitted to the steering wheel 2 (see FIG. 1).

  Therefore, in the present embodiment, the adjusting motor 66 is rotated by the detection signal of the disturbance detection sensor 27 including the magnet 25 and the coil 26 described above, and the adjusting bolt 63 is rotated by the rotating torque of the adjusting motor 66. Accordingly, the compression spring 62 in the guide portion 61 is appropriately compressed according to the magnitude of the disturbance, the rack shaft 8 is pressed by the concave tip 64 through the guide portion 61, and the rack teeth 8A are appropriately applied to the pinion 4A. It can be pressed with great force. Therefore, the vibration generated in the rack shaft 8 due to the disturbance of the steering system is suppressed from being transmitted to the steering wheel 2. Here, a disturbance suppressing means is realized by the adjusting motor 66, the adjusting bolt 63, the compression spring 62, the guide portion 61, and the concave tip 64.

  In the above-described embodiment, the electric power steering device 1 has been described as an example. However, the electric power steering device 1 is not limited to this method, and is similarly applied to other types of power steering devices such as a hydraulic power steering device. it can.

It is a whole block diagram which shows the operation | movement outline | summary of the electric power steering apparatus of one Embodiment by this invention. It is principal part sectional drawing which shows an electric power steering apparatus. It is sectional drawing which shows a disturbance detection sensor in detail, Comprising: (a) shows the cross section which cut | disconnected the B section shown in FIG. 2 by the surface along the axial direction of the rack axis | shaft 8, (b) shows (a). The CC cross section shown in FIG. It is the perspective view which expanded the B section (disturbance detection sensor) shown in FIG. It is AA sectional drawing of the electric power steering device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering device 2 Steering wheel 3 Steering shaft 4 Pinion shaft 4A Pinion 5 Torque sensor 6 Torque transmission means 7 Electric motor 8 Rack shaft 8A Rack tooth 9 Wheel 10 Control device 11 Worm wheel 12 Worm shaft 13 Worm gear 14 Rack housing 15 Boot 16 Tie rod 17 Rib 18 Mounting portion 19 Rack guide 21 First support means 22 Second support means 23 Third support means 25 Magnet 26 Coil 27 Disturbance detection sensor 61 Guide portion 62 Compression spring 63 Adjustment bolt 64 Concave tip 66 Adjustment motor

Claims (2)

A rack and pinion type power steering device that applies a steering assist force in accordance with a steering force input to a steering wheel,
It consists of a magnetized portion provided on a part of the rack shaft and a coil provided on the outer periphery of the position corresponding to the magnetized portion. When the rack shaft is displaced, the magnetized portion and the coil are relatively moved to induce the coil. A disturbance detection sensor for generating an electromotive force;
Based on the induced electromotive force generated by the disturbance detection sensor, disturbance suppressing means for suppressing the influence of the disturbance received by the steering system,
A power steering apparatus comprising:   The said disturbance suppression means increases the pressing force which presses the said rack shaft, and adjusts the friction which acts on the said rack shaft, so that the said induced electromotive force which the said disturbance detection sensor generate | occur | produces is large. The power steering apparatus according to 1.

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