Abstract:
A drive control system for preventing a sudden slowdown of driving speed to reduce the shock felt by a driver, when compound-operating two-way driving and a work device in an excavator.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a traveling control system of a construction machine such as an excavator. More particularly, the present invention relates to a traveling control system of a wheel-type construction machine in which sudden slowdown of the traveling speed can be prevented to reduce a shock felt by the operator in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed. 
       BACKGROUND OF THE INVENTION 
       [0002]    A hydraulic system applied to an excavator supplies some of a hydraulic fluid discharged from a plurality of variable displacement hydraulic pumps to left and right traveling motors through the shift of traveling spools, and supplies the remaining hydraulic fluid to a boom cylinder through the shift of work apparatus spools to drive a work apparatus such as a boom. 
         [0003]    In the case where a low traveling speed is selected by an operator, a low-speed traveling selection signal is applied to a controller to cause the traveling mode of a solenoid valve to be converted into a low speed traveling mode in response to a control signal from the controller. Thus, a signal pressure passing through the solenoid valve is supplied to a speed conversion valve mounted in the traveling motor to drive the speed conversion valve so that the swivel angle of a swash plate of the traveling motor can be maximized to perform a low-speed traveling mode. 
         [0004]    In a state in which the low-speed traveling mode is selected, when the two-way traveling operation is performed, the hydraulic fluid discharged from the hydraulic pump is respectively supplied to the left-traveling motor and the right-traveling motor via the traveling spools. 
         [0005]    In this case, when the work apparatus is manipulated by the operator (i.e., a combined operation of the two-way traveling operation and the operation of the work apparatus is operation), some of the hydraulic fluid discharged from the hydraulic pumps is supplied to the traveling motors and the remaining hydraulic fluid is supplied to the boom cylinder to drive the work apparatus, and thus the traveling speed is suddenly reduced. For this reason, the operator feels a shock, thereby lowering manipulability and thus degrading workability. 
       DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problems 
       [0006]    Accordingly, the present invention was made to solve the aforementioned problem occurring in the prior art, and it is an object of the present invention to provide a traveling control system for a construction machine, in which in the case where a combined operation is performed by manipulating the work apparatus during a low speed traveling operation of an excavator, the traveling mode is automatically converted into a high-speed traveling mode irrespective of a traveling speed selection signal so that sudden slowdown of the traveling speed can be prevented to reduce a shock felt by the operator and improve manipulability. 
       Technical Solution 
       [0007]    To accomplish the above object, in accordance with an embodiment of the present invention, there is provided a traveling control system for a construction machine, including: 
         [0008]    first and second variable displacement hydraulic pumps connected to an engine; 
         [0009]    a variable displacement left-traveling motor and a first hydraulic cylinder for a work apparatus that are connected to the first hydraulic pump and respectively driven when their spools are shifted; 
         [0010]    a variable displacement right-traveling motor and a second hydraulic cylinder for the work apparatus that are connected to the second hydraulic pump and respectively driven when their spools are shifted; 
         [0011]    a traveling speed selector configured to select either a low traveling speed or a high traveling speed; 
         [0012]    a low-speed/high-speed switching solenoid valve configured to output a signal pressure to control the swivel angles of swash plates of the left and right traveling motors in response to a selection signal outputted from the traveling speed selector; 
         [0013]    left and right traveling spools configured to control a start, a stop, and a direction change of the left and right traveling motors; 
         [0014]    a left and right traveling manipulator configured to shift the left and right traveling spools; 
         [0015]    first and second work apparatus spools configured to control a start, a stop and a direction change of the first and second hydraulic cylinders; 
         [0016]    a first and second work apparatus manipulator configured to shift the first and second work apparatus spools; and 
         [0017]    a controller configured to determine whether or not the a left and right traveling manipulator and the a first and second work apparatus manipulator are manipulated in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed in a low speed traveling mode and output a high speed traveling control signal to the solenoid valve to minimize the swivel angles of the swash plates of the left and right traveling motors. 
         [0018]    In accordance with an embodiment of the present invention, there is provided a traveling control system for a construction machine, wherein the traveling control system includes: first and second hydraulic pumps connected to an engine; left and right traveling motors and first and second hydraulic cylinder respectively connected to the first and second hydraulic pumps; a traveling speed selector configured to select either a low traveling speed or a high traveling speed; a low-speed/high-speed switching solenoid valve configured to output a signal pressure to control the swivel angles of swash plates of the left and right traveling motors; left and right traveling spools configured to control a start, a stop, and a direction change of the left and right traveling motors; a left and right traveling manipulator configured to shift the left and right traveling spools; first and second work apparatus spools configured to control a start, a stop and a direction change of the first and second hydraulic cylinders; a first and second work apparatus manipulator configured to shift the first and second work apparatus spools; and a controller configured to determine whether or not the a left and right traveling manipulator and the a first and second work apparatus manipulator are manipulated and output a control signal for controlling the swivel angles of the swash plates of the left and right traveling motors, the traveling control system including: 
         [0019]    a first step of determining whether or not a two-way traveling operation is performed by detecting manipulation of the traveling manipulator; 
         [0020]    a second step of determining whether or not a low speed traveling mode is selected in response to a selection signal outputted from the traveling speed selector  12 ; 
         [0021]    a third step of determining whether or not the operation of the work apparatuses is performed by detecting manipulation of the work apparatus manipulator in the low speed traveling mode; and 
         [0022]    a fourth step of determining whether or not the two-way traveling manipulator and the a first and second work apparatus manipulator are manipulated at the same time in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed in the low speed traveling mode, and converting the traveling mode into a high speed traveling mode by minimizing the swivel angle of the swash plates of the left and right traveling motors. 
         [0023]    In accordance with a more preferable embodiment, the traveling manipulator may output an electric output value according to the manipulation. 
         [0024]    The traveling manipulator may output a hydraulic pressure value according to the manipulation. 
         [0025]    The first and second work apparatus manipulator may output an electric output value according to the manipulation. 
         [0026]    The first and second work apparatus manipulator may output a hydraulic pressure value according to the manipulation. 
         [0027]    The electric output values of the traveling manipulator and the first and second work apparatus manipulator may be inputted to the controller so that the controller determines whether or not the traveling manipulator and the work apparatus manipulator are manipulated, and a plurality of electronic proportional valves for converting the electric output values into hydraulic pressures for shifting the left and right traveling spools and the first and second work apparatus spools are mounted between the controller and each of the spools. 
         [0028]    Whether or not the traveling manipulator and the first and second work apparatus manipulator are manipulated may be detected by a plurality of pressure sensor, which in turn outputs an electric output value for application to the controller. 
       Advantageous Effect 
       [0029]    The traveling control system for a construction machine in accordance with an embodiment of the present invention as constructed above has the following advantages. 
         [0030]    In the case where a combined operation is performed by manipulating the work apparatus during a low speed traveling operation of an excavator, the traveling mode is automatically converted into a high-speed traveling mode irrespective of a traveling speed selection signal so that sudden slowdown of the traveling speed can be prevented to reduce a shock felt by the operator and improve manipulability and workability. 
     
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         [0031]    The above objects, other features and advantages of the present invention will become more apparent by describing the preferred embodiments thereof with reference to the accompanying drawings, in which: 
           [0032]      FIG. 1  is a hydraulic circuit diagram showing a traveling control system for a construction machine in accordance with an embodiment of the present invention; and 
           [0033]      FIG. 2  is a flowchart showing the operation of a traveling control system for a construction machine in accordance with an embodiment of the present invention. 
       
    
    
     EXPLANATION ON REFERENCE NUMERALS OF MAIN ELEMENTS IN THE DRAWINGS 
       [0000]    
       
         
           
               1 ; engine 
               2 ; first hydraulic pump 
               3 ; second hydraulic pump 
               4 , 8 ; traveling spools 
               5 , 9 ; work apparatus spools 
               6 ; left-traveling motor 
               7 , 11 ; hydraulic cylinders 
               10 ; right-traveling motor 
               12 ; traveling speed selection switch 
               13 ; low-speed/high-speed switching solenoid valve 
               14 ; traveling manipulation detector 
               15 ; work apparatus manipulation detector 
               16 ; controller 
           
         
       
     
       PREFERRED EMBODIMENTS OF THE INVENTION 
       [0047]    Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and the present invention is not limited to the embodiments disclosed hereinafter. 
         [0048]    A traveling control system for a construction machine in accordance with an embodiment of the present invention as shown in  FIG. 1  includes: 
         [0049]    first and second variable displacement hydraulic pumps  2  and  3  (hereinafter, referred to as “first and second hydraulic pumps”) connected to an engine  1 ; 
         [0050]    a variable displacement left-traveling motor (hereinafter, referred to as “left-traveling motor”)  6  and a first hydraulic cylinder  7  for a work apparatus that are connected to the first hydraulic pump  2  and respectively driven when a left traveling spool  4  and a first work apparatus spool  5  are shifted; 
         [0051]    a variable displacement right-traveling motor (hereinafter, referred to as “right-traveling motor”)  10  and a second hydraulic cylinder  11  for the work apparatus that are connected to the second hydraulic pump  3  and respectively driven when a right traveling spool  8  and a second work apparatus spool  9  are shifted; 
         [0052]    a traveling speed selector  12  configured to select either a low traveling speed or a high traveling speed; 
         [0053]    a low-speed/high-speed switching solenoid valve  13  configured to output a signal pressure to control the swivel angles of swash plates of the left and right traveling motors  6  and  10  in response to a selection signal outputted from the traveling speed selector  12 ; 
         [0054]    left and right traveling spools  4  and  8  configured to control a start, a stop, and a direction change of the left and right traveling motors  6  and  10 ; 
         [0055]    a left and right traveling manipulator (not shown) configured to shift the left and right traveling spools  4  and  8 ; 
         [0056]    first and second work apparatus spools  5  and  9  configured to control a start, a stop and a direction change of the first and second hydraulic cylinders  7  and  11 ; 
         [0057]    a first and second work apparatus manipulator (not shown) configured to shift the first and second work apparatus spools  5  and  9 ; and 
         [0058]    a controller  16  configured to determine whether or not the a left and right traveling manipulator and the a first and second work apparatus manipulator are manipulated in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed in a low speed traveling mode and output a high speed traveling control signal to the low-speed/high-speed switching solenoid valve  13  to minimize the swivel angles of the swash plates of the left and right traveling motors  6  and  10 . 
         [0059]    In this case, the traveling manipulator (not shown) outputs an electric output value according to the manipulation. 
         [0060]    The traveling manipulator outputs a hydraulic pressure value according to the manipulation. 
         [0061]    The first and second work apparatus manipulator (not shown) outputs an electric output value according to the manipulation. 
         [0062]    The first and second work apparatus manipulator outputs a hydraulic pressure value according to the manipulation. 
         [0063]    The electric output values of the traveling manipulator and the first and second work apparatus manipulator are inputted to the controller  16  so that the controller determines whether or not the traveling manipulator and the work apparatus manipulator are manipulated, and a plurality of electronic proportional valves (not shown) for converting the electric output values into hydraulic pressures for shifting the left and right traveling spools  4  and  8  and the first and second work apparatus spools  5  and  9  are mounted between the controller  16  and each of the spools. 
         [0064]    Whether or not the traveling manipulator and the first and second work apparatus manipulator are manipulated is detected by a plurality of pressure sensors (not shown), which in turn outputs an electric output value for application to the controller  16 . 
         [0065]    In accordance with an embodiment of the present invention as shown in  FIG. 2 , there is provided a traveling control method using a traveling control system for a construction machine, the traveling control system including: first and second variable displacement hydraulic pumps  2  and  3  connected to an engine  1 ; left and right variable displacement traveling motors  6  and  10  and first and second hydraulic cylinder  7  and  11  respectively connected to the first and second hydraulic pumps  2  and  3 ; a traveling speed selector  12  configured to select either a low traveling speed or a high traveling speed; a low-speed/high-speed switching solenoid valve  13  configured to output a signal pressure to control the swivel angles of swash plates of the left and right traveling motors  6  and  10 ; left and right traveling spools  4  and  8  configured to control a start, a stop, and a direction change of the left and right traveling motors  6  and  10 ; a left and right traveling manipulator  14  (not shown) configured to shift the left and right traveling spools  4  and  8 ; first and second work apparatus spools  5  and  9  configured to control a start, a stop and a direction change of the first and second hydraulic cylinders; a first and second work apparatus manipulator (not shown) configured to shift the first and second work apparatus spools  5  and  9 ; and a controller  16  configured to determine whether or not the a left and right traveling manipulator and the a first and second work apparatus manipulator are manipulated and output a control signal for controlling the swivel angles of the swash plates of the left and right traveling motors  6  and  10 . 
         [0066]    The traveling control method includes: 
         [0067]    a first step (S 100  and S 200 ) of determining whether or not a two-way traveling operation is performed by detecting manipulation of the traveling manipulator; 
         [0068]    a second step (S 300 , S 400 , S 500 ) of determining whether or not a low speed traveling mode is selected in response to a selection signal outputted from the traveling speed selector  12 ; 
         [0069]    a third step (S 600 , S 700 , S 800 ) of determining whether or not the operation of the work apparatuses is performed by detecting manipulation of the a first and second work apparatus manipulator in the low speed traveling mode; and 
         [0070]    a fourth step (S 900 ) of determining whether or not the two-way traveling manipulator and the a first and second work apparatus manipulator are manipulated at the same time in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed in the low speed traveling mode, and converting the traveling mode into a high speed traveling mode by minimizing the swivel angle of the swash plates of the left and right traveling motors  6  and  10 . 
         [0071]    Hereinafter, a use example of the traveling control system for a construction machine in accordance with an embodiment of the present invention will be described in detail with reference to  FIGS. 1 and 2 . 
         [0072]    At step S 100 , when a travel manipulator (not shown) is manipulated by an operator, the manipulation of the traveling manipulator is detected by a traveling manipulation detector  14 , which in turn generates a manipulation signal for application to the controller  16 . 
         [0073]    In the case where the traveling manipulator is a hydraulic manipulator, the traveling manipulation detector  14  detects a hydraulic pressure such as a pressure sensor or a pressure switch and converts the detected hydraulic pressure into an electric signal for application to the controller  16 . In the case where the traveling manipulator is an electric manipulator, the electric manipulator detects outputs an electric signal for application to the controller  16  without a separate detector. 
         [0074]    At step S 200 , the controller  16  determines whether or not the construction machine is in a traveling mode based on the manipulation signal inputted to the controller  16 . If it is determined at step S 200  that the construction machine is in the traveling mode, the program proceeds to step S 300  where the controller  16 . On the contrary, if it is determined at step S 200  that the construction machine is not in the traveling mode, the program is terminated. 
         [0075]    At step S 300 , if the construction machine is in the traveling mode, the operator manipulates the traveling speed selector  12  to select either a low traveling speed or high traveling speed, and a selection signal outputted from the traveling speed selector  12  is applied to the controller  16 . 
         [0076]    At step S 400 , the controller  16  determines whether or not the traveling mode is in a low speed traveling mode based on the selection signal applied to the controller  16 . If it is determined at step S 400  that the traveling mode is in the low speed traveling mode, the program proceeds to step S 600 . On the contrary, if it is determined at step  4200  that the traveling mode is not in the low speed traveling mode, the program proceeds to step S 500 . 
         [0077]    At step  5 , in the case where a high speed traveling mode is selected by the manipulation of the traveling speed selector  12 , the traveling mode is converted into the high speed traveling mode by minimizing the swivel angles of swash plates of the left and right traveling motors  6  and  10 . 
         [0078]    At step S 600 , when the first and second work apparatus manipulator (not shown) is manipulated by the operator, the manipulation of the work apparatus manipulator is detected by a work apparatus manipulation detector  15 , which in turn generates a manipulation signal for application to the controller  16 . 
         [0079]    In the case where the first and second work apparatus manipulator is a hydraulic manipulator, the work apparatus manipulation detector  15  detects a hydraulic pressure such as a pressure sensor or a pressure switch and converts the detected hydraulic pressure into an electric signal for application to the controller  16 . In the case where the work apparatus manipulator is an electric manipulator, the electric manipulator detects outputs an electric signal for application to the controller  16  without a separate detector 
         [0080]    At step S 700 , the controller  16  determines whether or not a work apparatus such as a boom is manipulated based on a detection signal from the work apparatus manipulation detector  15  in a state in which the low speed traveling mode is selected. If it is determined at S 700  that the work apparatus is manipulated, the program proceeds to step S 900 . On the contrary, if it is determined at S 700  that the work apparatus is in a stop state based on the detection signal from the work apparatus manipulation detector  15 , the program proceeds to step S 800  where the low speed traveling mode is maintained. 
         [0081]    At step S 900 , the controller  16  calculates a low-speed traveling election signal applied thereto from the traveling speed selector  12 , a traveling manipulation signal applied thereto from the traveling manipulation detector  14 , and a work apparatus manipulation signal applied thereto from the work apparatus manipulation detector  15  in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed in the low speed traveling mode. 
         [0082]    For this reason, the controller  16  outputs a control signal to the low-speed/high-speed switching solenoid valve  13  to control the left and right traveling motors  6  and  10 . Thus, the traveling mode can be converted into the high speed traveling mode by minimizing the swivel angles of swash plates of the left and right traveling motors  6  and  10  by means of speed conversion valves  6   a  and  10   a  mounted in the left and right traveling motors  6  and  10 . 
         [0083]    As a result, the hydraulic fluid discharged from the first and second hydraulic pumps  2  and  3  is distributedly supplied to the left and right traveling motors  6  and  10  and the hydraulic cylinders  7  and  11 . In this case, as the traveling mode is converted into the high speed traveling mode by minimizing the swivel angles of swash plates of the left and right traveling motors  6  and  10 , so that sudden slowdown of the traveling speed can be prevented to reduce a shock felt by the operator in case of a combined operation in which the two-way traveling operation and the operation of the work apparatus are performed, 
         [0084]    While the present invention has been described in connection with the specific embodiments illustrated in the drawings, they are merely illustrative, and the invention is not limited to these embodiments. It is to be understood that various equivalent modifications and variations of the embodiments can be made by a person having an ordinary skill in the art without departing from the spirit and scope of the present invention. Therefore, the true technical scope of the present invention should not be defined by the above-mentioned embodiments but should be defined by the appended claims and equivalents thereof. 
       INDUSTRIAL APPLICABILITY 
       [0085]    As described above, according to the traveling control system for a construction machine in accordance with an embodiment of the present invention, 
         [0086]    In the case where a combined operation is performed by manipulating the work apparatus during a low speed traveling operation of an excavator, the traveling mode is automatically converted into a high-speed traveling mode irrespective of a traveling speed selection signal so that sudden slowdown of the traveling speed can be prevented to reduce a shock felt by the operator and improve manipulability.