Abstract:
An automotive steering rack-stroke adjusting device with which a driver can conveniently control the length of a steering rack-stroke as needed for changing a minimum turning radius, the device including: a rotational body rotatively arranged at both ends of a power cylinder of a steering system; a stop plate fixed at a rack for inserting or overlapping to the center of the rotational body according to the rotational state of the rotational body when the rack is pulled to the power cylinder to the maximum extent; and an actuator for rotating the rotational body forwards or backwards under the control of a control unit which is manipulated by a driver with an operational switch.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an automotive steering rack-stroke adjusting device and more particularly to an automotive steering rack-stroke adjusting device with which a driver can conveniently control the range of a steering rack-stroke as required for changing a minimum rotation radius, thereby providing convenience for the driver. 
     2. Description of the Prior Art 
     In driving an auto vehicle, a driver makes frequent U turns. In case of a vehicle with a large minimum rotation radius, a U turn cannot be completed by one trial, but with several adjustments, which brings about inconvenience and disruption in driving, an aggravating a problem during traffic congestion. 
     Recently, there has been introduced a model of a large passenger vehicle with an entire length of over 5000 mm in addition to large-scale cargo trucks or family vans, thereby worsening the aforementioned problem of making a U turn. 
     In addition, the problem as such gets more serious with any vehicles with front engine and front wheel drives because the engine is horizontally positioned to occupy a large space of the engine room, so that it gets difficult to accommodate a steering space for setting up a steering angle of the front wheel. 
     Furthermore, according to a conventional method for setting up a rack-stroke of a steering gear box for steering operations, the rack-stroke is set up to maintain a gap from side members of a body and the related parts to the minimum assumed that a maximum cross-sectional size of a tire is measured under a worst driving condition where a snow chain is wound at a front wheel (driving wheel). 
     However, there is a problem in that if the rack-stroke of a steering gear box is set up as described above, a rotation size of a wheel is made with an overall surface including a largest tire utilized or a snow chain mounted to a regular tire, such that in case of using only a regular tire or a tire without a snow chain to the regular tire, the gap to an actually interfering object point gets bigger. 
     There is another problem in that the aforementioned problem occurs when a U turn is made in the course of a regular driving at a low speed in a city, and in most cases, although a steering handle can be allowed to make a further wider turn, the rack-stroke is set up at its worst condition. 
     Particularly, although the minimum rotation radius is a factor to significantly affect the quality of a product like large passenger cars or any other front driving vehicles, the rack-stroke of steering gear box is still inefficiently constructed as described above. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention is disclosed to solve the aforementioned problem and it is an object of the present invention to provide an automotive steering rack-stroke adjusting device with which a driver can conveniently control the range of a steering rack-stroke as required for changing a minimum rotation radius, thereby providing convenience for the driver. 
     In order to accomplish the aforementioned object of the present invention, there is provided an automotive steering rack-stroke adjusting device comprising: 
     a rotational body rotatably arranged at both ends of a power cylinder of a steering system; 
     a stop plate fixed at a rack for inserting or overlapping to the center of the rotational body according to the rotational state of the rotational body when a rack is pulled toward the power cylinder to a maximum extent; and 
     an actuator for rotating the rotational body back and forth under the control of a control unit is manipulated by a driver with an operational switch, the operational switch being operable independently of a steering wheel of the steering system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For fuller understanding of the nature and object of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block diagram of an automotive steering rack-stroke adjusting device of the present invention; 
     FIG. 2 is a partial perspective view of a steering gear box for illustrating a part to which the present invention is applied; 
     FIG. 3 is a cross-sectional view taken along line I—I shown in FIG. 2 for illustrating the structure of the first embodiment in accordance with the present invention; 
     FIG. 4 is an analytical perspective partial view of an important part for illustrating the first embodiment of the present invention; 
     FIG. 5 a  is a front view for illustrating a state of a steering rack-stroke adjusting device prior to operation of the first embodiment in accordance with the present invention; 
     FIG. 5 b  is a cross-sectional view taken along line II—II for illustrating a state of a steering rack-stroke adjusting device prior to operation of the first embodiment in accordance with the present invention; 
     FIG. 6 a  is a front view for illustrating a state of a steering rack-stroke adjusting device after operation of the first embodiment in accordance with the present invention; 
     FIG. 6 b  is a cross-sectional view taken along line III—III for illustrating a state of a steering rack-stroke adjusting device after operation of the first embodiment in accordance with the present invention; 
     FIG. 7 illustrates a steering rack-stroke adjusting device in accordance with a second embodiment of the present invention; 
     FIG. 8 illustrates a steering rack-stroke adjusting device in accordance with a third embodiment of the present invention; and 
     FIG. 9 is a cross-sectional view taken along line IV—IV shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, preferred embodiments of the present invention will be described in detail with accompanying drawings. 
     FIG. 1 is a block diagram of a steering system in accordance with the present invention, and reference numeral  2  indicates an operational switch. 
     The operational switch  2  is arranged near a driver&#39;s seat. When a driver manipulates the operational switch  2  as needed, a control unit  4  recognizes it to thereby adjust rack-stroke by controlling left and right actuators  6 , 8 , in other words, driving means arranged at a predetermined position of a steering gear box. 
     As described above, the left and right actuators  6 , 8 , driving means to be operated with an electrical signal of the control unit  4 , as shown in FIG. 2, are to control rack-stroke adjusting means arranged at left and right sides of a steering gear box  10 . At this time, the left and right rack-stroke adjusting means are integrally constructed, so that only one of the adjusting means is illustrated in the drawing of the present invention as shown in FIG.  2 . 
     In addition, if a steering handle (not shown) is rotated in a steering direction, the steering system using rack and pinion of the present invention conveys the rotational motion to the steering gear box  10  via a steering shaft. In the steering box  10 , a rack  14  installed in a power cylinder  12  is moved to the left or right by a rack and pinion method to steer a wheel via a tie-rod  18  connected with an insertion of a ball joint  16  at a free end of the rack  14 , thereby accomplishing the steering operation of a vehicle. 
     In accordance with the present invention, a first embodiment of a rack-stroke adjusting means applicable to the steering system as such comprises: a driving motor  20 , that is, an actuator, a rotational body  22  to be driven by the driving motor  20  and a stop plate  26  to selectively pass through a throughhole  24  formed at the center of the rotational body  22 . 
     At this time, the driving motor  20  is embedded with a circuit breaker to automatically stop its operations when the motor is excessively loaded in its operation. 
     Furthermore, the rotational body  22  is made of a circular plate with a gear part  28  being formed at its external circumference. At this time, the gear part  28  is formed at any part of the external circumference of the rotational body  22 , but it may also be formed within the range of a rotation to be drawn by the rotational body  22 . 
     Also, a throughhole  24  is formed at the center of the rotational body  22 , and the throughhole  24  is formed with curved surfaces  30  at the center, and with two sector grooves  32  connecting the curved surfaces  30  and a protruder  36  on a side of the rotational body. 
     The sector type grooves  32  define an internal angle (α) of 90 degrees, which means that the rotational body  22  is set to be controlled to rotate forwards or backwards by 90 degrees. It is not necessary to restrict the internal angle of the sector type grooves  32  to 90 degrees, so that a slight variation from 90 degrees is achievable. In case of variations of the internal angle (α), the rotational angle of the rotational body  22  should be adjusted according to its varied internal angle. 
     Additionally, a stop protruder  36  is formed at one side of the two sector type grooves  32  for limiting the range of moving the rack  14 . 
     Also, the stop plate  26  selectively passing through the throughhole  24  includes diametrically opposed protruders  42  which correspond to the sector grooves  32 . 
     The parts constructed as such are arranged to allow the rotational body  22  to rotate within the power cylinder  12  as shown in FIG.  3 . 
     As further shown in FIG. 3, the driving motor  20  drives the rotational body  22  when it is fixed within the power cylinder  12  with an insertion of an idling gear  44 , and the stop plate  26  is fixed at an internal side of a ball joint  16  around the rack  14 , allowing the sector protruders  42  to be inserted into the sector grooves  32  of the rotational body  32  before its operations. 
     According to the first embodiment of the present invention as described above, in case of the regular driving state where the stroke of the rack  14  is controlled at its maximum extent, as shown in FIG. 5, the sector type grooves  32  and protruders  42  of the rotational body  22  are positioned at an identical level of a line. If rack  14  is pulled toward the power cylinder  12  to the maximum extent according to its steering operation, the sector type of protruders  42  are inserted to the sector type grooves  32 , to thereby maximize the level of its steering operation. 
     Accordingly, it becomes possible to increase the minimum rotational radius to the maximum extent in the regular driving status, thereby being very advantageous in the driving condition of maintaining the minimum rotational radius. 
     However, in case of reducing a stroke of the rack  14  by winding a chain onto a wheel, a driver can manipulate the operational switch  2  arranged at the driver&#39;s seat to control the left and right actuators  6 ,  8  of the control unit  4 . 
     In other words, when power is supplied to the driving motor  20  relevant to the left and right actuators  6 , 8  from the control unit  4  to rotate the rotational body  22  to a predetermined angle (approximately 90 degrees), thereby resulting in the state illustrated in FIG. 6 a.    
     Then, the sector protruders  42  of the stop plate  26 , and the protruders  36  of the rotational body  22  are positioned at an identical level. When the rack  14  is pulled to its maximum level according to a steering operation, the sector protruders  42  contact the protruders  36  as shown in FIG. 6 b , thereby restricting movement of the rack  14 . 
     Likewise, if the rack  14  is restricted to reduce its movement by the thickness (β) of the rotational body  22  in comparison with its normal state, the steering angle gets as small as the reduction in movement of the rack  14 . 
     In other words, the reduction of a steering angle means that it is possible to prevent a chain wound around a wheel from making any damage to the body in contact. 
     FIG. 7 illustrates a second embodiment of the present invention. In the first embodiment described above, the gear part  28  at the external circumference of the rotational body  22  is constructed in a spur gear arrangement with insertion of the idling gear  44  to be driven by the driving motor  20 . In contrast, a circular drive motor  20  rotates a worm gear arrangement in the second embodiment of the present invention. 
     In other words, a worm  52  is mounted at an end of a motor shaft  50 , and a worm gear  54  is formed at an external circumference of the rotational body  22 . At this time, even the second embodiment has a difference in its driving method from the first embodiment, its operations and effects are the same as those of the first embodiment, so as to omit detailed descriptions. 
     FIG.  8  and FIG. 9 illustrate a third embodiment of the present invention using a solenoid  60 , differently from the second and third embodiments motors using rotating drive. 
     In other words, a cable  64  is connected at an end of an operating rod  62  of the solenoid  60 , which is further connected with the rotational body  22 . When power is supplied to the solenoid  60 , the operational rod  62  and the cable  64  are sequentially pulled to rotate the rotational body  22 . 
     In contrast, when power is shut off to the solenoid  60 , the operational rod  62  returns by a return spring embedded at the solenoid  60  to thereby return the rotational body  22 . 
     Also, the cable  64  is made of a kind of elastic material to be wound around the external circumference of the rotational body  22 , preventing the rotational body  22  from returning by recovery of the pulled cable  64 . 
     In addition, in FIG. 9 an elastic member  66  is included between the rotational body  22  and the power cylinder  12 . The arrangement of the elastic member  66  as such can make sure of the recovery of cable  64 . 
     As described above, there is an advantage in the present invention in that the dimension of stroke of a steering rack can be conveniently controlled as needed for changing its minimum rotation radius, thereby minimizing its minimum rotation radius and providing convenience in driving. 
     Additionally, the present invention is advantageous in solving a problem of contacting a tire chain with the body by a reduction in range of a stroke of the rack when the chain is wound around the wheel on snowy days, thereby improving the quality of vehicle steering. 
     Furthermore, the present invention is also advantageous in securing the minimum rotation radius according to the driving conditions to improve convenience of parking the vehicle, driving it at low speeds, making a U turn, or driving on a narrow road, and in securing the cross-sectional surfaces of side members and lower arms to reinforce strength and improve endurance to collision or impact and NVH.