JP3837829B2 - Shock absorber for electric power steering - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device for absorbing a large impact force generated at a steering end in a vehicle equipped with an electric power steering device such as a battery forklift when it is stationary.
[0002]
[Prior art]
4 to 7 show a steering mechanism of a counter-type battery forklift well known in the art. This steering mechanism includes an electric power steering device. Referring to the drawings in detail, reference numeral 1 shown in FIG. 4 denotes a steering shaft that is rotated by a driver, and a steering wheel (not shown) is attached to the upper end of the steering shaft. Further, a rack and pinion type or ball screw type steering gear 2 is attached to the lower end thereof, and the rotation of the steering shaft 1 is converted into the swing of the pitman arm 3. One end of a connecting link 4 is pivotally attached to the tip of the pitman arm 3, and the other end of the connecting link 4 is connected to one end of an arm 6 rotatably supported by a fulcrum shaft 5 fixed to a vehicle body frame (not shown). It is pivotally attached. The other end of the arm 6 is pivotally attached to the front end of a long drag rod 7 extending toward the rear of the vehicle body frame, and the rear end of the drag rod 7 is attached to a rear axle beam 8 that supports the rear wheel, as shown in FIG. It is pivotally attached to one end of a bell crank 10 which is supported so as to be rotatable around the vertical axis 9 formed.
[0003]
An axle 12 that rotatably supports a pair of left and right rear wheels 11 (in this case, a steered wheel of a vehicle) via bearings is turned around a substantially vertical axis by a king pin 13 attached to the rear axle beam 8. Supported as possible. The turning of the axle 12 and the steering wheel 11, that is, the steering, is the other end of the tie rod 15 in which the tip of the knuckle arm 14 provided integrally with the axle 12 is pivotally attached to the other end of the bell crank 10. It is operated by being pivotally attached via a ball joint or the like. The support structure of the king pin 13 is clearly shown in FIG. 6 and FIG. 7 which is an enlarged view of a main part thereof. That is, a steering wheel support portion 16 is attached to the rear axle beam 8 corresponding to each steering wheel 11, and the upper and lower jaws that project laterally toward the steering wheel 11 are respectively attached to the support portions 16. Portions 17 and 18 are formed. The kingpin 13 is supported by their jaws 17 and 18.
[0004]
As shown in FIG. 4, an electric power steering device (EPS device) 19 is provided so as to be in parallel with the drag rod 7. Since the internal structure of the EPS device 19 is well known, a detailed description thereof will be omitted, but the EPS device 19 includes one electric motor 20 for boosting. A torque sensor 21 is provided in the vicinity of the lower end of the steering shaft 1 described above, and detects the magnitude and direction of the steering torque applied to the steering shaft 1 by the driver, and the signal is not shown in the controller. Send to. Since the controller controls the electric power supplied to the electric motor 20 in accordance with the signal, the electric motor 20 generates an additional steering force that increases approximately in proportion to the magnitude of the steering torque via a gear device (not shown), Add it to the drag rod 7 described above. For this purpose, the base end 22 of the EPS device 19 is pivotally attached to a part of a body frame (not shown) by a ball joint, and the distal end 23 of the output rod is also connected to a part of the drag rod 7 via the ball joint.
[0005]
When the electric power steering device (EPS device) 19 is operating normally, the steering force generated by the EPS device 19 is many times greater than the steering force of the driver transmitted to the tip 23 of the drag rod 7. Therefore, the turning of the steering wheel 11, that is, the steering operation is almost performed by the output of the EPS device 19. Accordingly, since the driver does not need to apply a large steering torque to the steering shaft 1, the rotation operation of a steering wheel (not shown) attached to the upper end of the steering shaft 1 is lightened, and the labor required for driving is greatly reduced. . Should the EPS device 19 break down, the driver's steering force is transmitted from the steering shaft 1 to the drag rod 7 via the arm 6 or the like, and the steering wheel 11 can be steered even though it is relatively weak. it can.
[0006]
In order to set a limit, that is, a steering end, to the turning angle (also referred to as a steering angle or a turning angle) of the steering wheel 11, a stopper 24 is provided on the steering wheel support portion 16. The stopper 24 is an integral part of the knuckle arm 14 and touches a portion protruding in the radial direction when viewed from the axial center of the kingpin 13, for example, a portion such as the base of the axle 12, so that the knuckle arm 14 is further rotated. Is to prevent. As shown in an enlarged view in FIG. 7, the stopper 24 generally used in the past is screwed into a stopper bracket 25 fixed to the steering wheel support 16 side by a method such as welding and a female screw hole formed thereon. The stopper bolt 26 is inserted. Accordingly, the stopper bolt 26 is screwed into the female screw hole of the stopper bracket 25, the height of the head 26a of the stopper bolt 26 is adjusted, and the height is fixed by the lock nut 26b, whereby the knuckle arm integral with the axle 12 is obtained. The 14 pivotable angles are limited.
[0007]
[Problems to be solved by the invention]
Since the conventional stopper 24 has a so-called rigid body structure as described above, a portion such as the base portion of the axle 12 that protrudes in the radial direction integrally with the knuckle arm 14 contacts the head portion 26a of the stopper bolt 26. When the vehicle is prevented from turning, that is, at the steering end, the raised portion of the knuckle arm 14 is supported by the steering wheel support portion of the rear axle beam 8 by the stopper bracket 25 by the large steering force increased by the operation of the EPS device 19. It will collide with the head 26a of the stopper bolt 26 which is completely fixed on the top 16.
[0008]
In addition, unlike the hydraulic power steering device, the EPS device 19 generates additional steering force by the rotation of the electric motor 20, and therefore when the torque sensor 21 detects a sudden increase in steering torque at the steering end. From the fact that there is a slight time lag before the controller (not shown) cuts off the supply of power to the electric motor 20, the rotor of the rotating electric motor 20 has an inertial force. This is because even if the supply of electric power is cut off, it cannot be stopped immediately, and a decrease in steering force is delayed.
[0009]
In particular, when the steering wheel is fixed in a stationary state, an extremely large impact force acts on both the stopper 24 side and the knuckle arm 14 side at the steering end. As described above, the knuckle arm 14 is connected to the EPS device 19 and the steering mechanism including a number of links going back to the steering shaft 1 via the drag rod 7, which is uncomfortable with the steering wheel held by the driver. Not only is the impact transmitted, but there is a risk that the EPS device 19 itself, the link and joints of the steering mechanism, the steering gear 2 and other components will be rattled or damaged due to repeated impacts. . Therefore, if the mechanism is strengthened in order to avoid this problem, there is a problem that the cost increases or the weight increases. Therefore, in general, a countermeasure that lowers the steering performance, that is, the maximum current of the electric motor 20 is limited. Usually, passive measures such as keeping the steering speed low were taken.
[0010]
The present invention addresses the above-mentioned problems in the prior art, but does not take a passive countermeasure such as lowering the steering performance of the electric power steering apparatus, and further improves the steering mechanism. It is an object of the present invention to provide a simple and inexpensive means that can effectively absorb an impact at the steering end of an electric power steering apparatus without the need for further strengthening, and to solve the aforementioned problems.
[0011]
[Means for Solving the Problems]
The present invention provides an impact absorbing device in an electric power steering apparatus described in each claim as a novel means for solving the above-mentioned problems.
[0012]
According to the present invention, in a vehicle steering mechanism such as a cargo handling vehicle equipped with an electric power steering device, a stopper provided for determining a steering end is subjected to a relatively large bending deformation by elasticity. An elastic means capable of absorbing the impact force is used. As this elastic means, for example, an elastic body obtained by bending a round bar made of spring steel into a U shape can be used. In this case, it is preferable that the base portion of the elastic body is fixed to the vehicle body side, and the tip portion is disposed so as to be in contact with the base portion of the axle that supports the steering wheel. Further, it is desirable to provide adjusting means for adjusting the height substantially at the tip of the elastic means. The adjusting means can be configured, for example, by screwing a bolt into a female screw hole at the tip of the elastic means.
[0013]
[Action]
Since the present invention has the above-described configuration, the electric power steering device is activated in accordance with the steering operation by the driver, and a large steering force is transmitted to the steering wheel through the mechanism, so that the steering wheel is It turns lightly and quickly, but when it reaches the steering end, which is the limit of the steering angle, a part of the mechanism comes into contact with the stopper to prevent further turning. In the present invention, since the impact force at this time is absorbed by the elastic means, the turning of the steering wheel can be stopped without damaging the mechanism and without causing the driver to feel an unpleasant impact. .
[0014]
If an elastic body bent in a U shape is used as the elastic means, the depth is deep so that it can be greatly bent by elastic deformation when it receives a large steering force. Further, when the adjusting means is provided at the tip of the elastic means, the steering angle of the steering end can be freely changed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The most preferred embodiment of the present invention will be described with reference to FIGS. Since the present invention is characterized by an improved structure of the stopper 24 that defines the steering end as compared with the above-described prior art (see FIGS. 4 to 7), other configurations are substantially the same as those of the prior art. May be the same. Therefore, also in the illustrated embodiment, the same reference numerals are assigned to portions that are substantially the same as those of the prior art except for the stopper 24, and redundant detailed description will be omitted. In that sense, FIG. 4 and FIG. 5 are incorporated as showing the overall configuration of the embodiment of the present invention.
[0016]
In the preferred embodiment of the present invention shown in FIGS. 1 to 3, the stopper 24 for defining the steering end is made of an elastic body 27 manufactured by bending a round bar made of a steel material such as spring steel having strong elasticity into a U shape. I use it. The base end 27a of the elastic body 27 is fixed to a part of the steered wheel support 16 or, in some cases, directly to the left and right tip portions of the rear axle beam 8 by welding. The distal end 27b of the elastic body 27 is a free end, and a female screw hole is formed in the end surface, and a stopper bolt 28 is screwed into the female screw hole. The height at which the head 28a of the stopper bolt 28 protrudes from the tip 27b of the elastic body 27 can be freely changed by changing the depth of screwing, and the set height is shown enlarged in FIG. As described above, the lock nut 29 can be tightened and fixed securely.
[0017]
Since the illustrated embodiment has such a configuration, a large steering force is transmitted from the EPS device 19 to the knuckle arm 14 via the tie rod 15 as shown in FIGS. 4 and 5, and at the steering end, When the base portion of the axle 12, which is an integral raised portion in the radial direction, comes into contact with the head 28a of the stopper bolt 28 attached to the tip 27b of the elastic body 27 as shown in FIG. 3, the elastic body 27 is U-shaped. Since it is bent to a large depth, it can be bent greatly by elastic deformation, so that a large impact force due to contact can be absorbed.
[0018]
Therefore, by providing the stopper 24 using the elastic body 27 bent into a U-shape as a preferred embodiment of the present invention, the EPS device 19 and the steering mechanism connected to the knuckle arm 14 due to the impact force at the steering end. Since breakage can be effectively prevented, the strength of the mechanism is increased to a level that is normally necessary to increase the cost and weight, or the current supplied to the electric motor 20 is limited to decrease the steering speed. There is no need to take any passive measures.
[0019]
In the illustrated embodiment, an elastic body 27 bent into a U-shape is used as the elastic means provided in the stopper 24. However, the elastic means is strong and can receive a large steering force, and thereby relatively large. If it is an elastic body that bends and deforms, it does not necessarily have to be formed into a U-shape. For example, a strong coil spring or bamboo shoot spring of about 1 or 2 turns, a block made of hard synthetic rubber or plastic, etc. As a means, the elastic body 27 can be used instead.
[0020]
【The invention's effect】
According to the present invention, since it is possible to avoid the generation of a large impact force at the steering end by providing the elastic means at the stopper that determines the steering end, the electric power steering device connected to the steering wheel In addition, it is possible to effectively prevent the steering mechanism including many members from being damaged. Therefore, it is possible to avoid increasing the cost and weight by increasing the strength of the mechanism beyond the necessary level, and of course, limiting the current supplied to the electric motor of the electric power steering device to reduce the steering speed. It is possible to obtain a sufficiently high steering speed by a relatively low-strength mechanism without having to take passive measures such as causing a light power steering effect with a small steering force of the driver. become.
[Brief description of the drawings]
FIG. 1 is a plan view showing a preferred embodiment of the present invention.
FIG. 2 is a front view of the embodiment shown in FIG.
FIG. 3 is a plan view showing a main part of the embodiment shown in FIG. 1;
FIG. 4 is a perspective view showing an overall configuration of a steering mechanism.
5 is a plan view showing a portion related to a steered wheel in the steering mechanism shown in FIG. 4; FIG.
FIG. 6 is a front view showing a conventional example of a rear axle beam and a steered wheel support portion.
7 is an enlarged front view showing only the main part of the conventional example shown in FIG. 6. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Steering shaft 3 ... Pitman arm 7 ... Drag rod 8 ... Rear axle beam 10 ... Bell crank 11 ... Steering wheel (rear wheel)
DESCRIPTION OF SYMBOLS 12 ... Axle 13 ... Kingpin 14 ... Knuckle arm 15 ... Tie rod 16 ... Steering wheel support part 17, 18 ... Upper and lower jaw part 19 ... Electric power steering device (EPS device)
20 ... Electric motor 21 ... Torque sensor 24 ... Stopper 25 ... Stopper bracket (conventional example)
26 ... Stopper bolt (conventional example)
27. Elastic body bent in U shape (elastic means)
27a ... fixed base end 28 ... stopper bolt 29 ... lock nut

Claims (3)

The steering mechanism for a vehicle having an electric power steering apparatus, the stopper defining the steering end, set the elastic means can be a deformed by elasticity to absorb impact forces,
The elastic means is formed of an elastic body bent into a U-shape;
A shock absorber in an electric power steering device characterized in that a base portion of the elastic means is fixed to the vehicle body side, and a tip portion is arranged so as to be in contact with a base portion of an axle supporting a steering wheel. apparatus. 2. The impact absorbing device according to claim 1 , wherein an adjusting means for substantially adjusting the height of the elastic means is provided at a tip portion of the elastic means. The impact absorbing device according to claim 1 or 2 , wherein the adjusting means comprises a bolt screwed into a tip portion of the elastic means.

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