Abstract:
The hybrid excavator includes: a first detection sensor for detecting an RCV-manipulated quantity; a second detection sensor for detecting the rotational speed of an electric motor; a hydraulic pump-motor connected to the electric motor; a hydraulic cylinder connected to the hydraulic pump-motor; first and second hydraulic valves installed in first and second passages, respectively, between the hydraulic pump-motor and the hydraulic cylinder; a third hydraulic valve for compensating for or bypassing a flow rate and a controller for receiving an RCV-manipulation signal from the first detection sensor and the rotational speed of the electric motor from the second detection sensor to compare the received values to data of previously stored working conditions, to output a control signal for switching the first and second hydraulic valves, and to block a working fluid from returning into the hydraulic cylinder, so as to thereby quickly stop the working device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the National Phase application of International Application No. PCT/KR2011/003458 filed on May 11, 2011, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a hybrid excavator including a device that brings are electro-hydraulic actuator mounted thereon to a quick stop. More particularly, the present invention relates to a hybrid excavator that is configured to quickly stop a work apparatus (or attachment) operated, i.e., descending at high speed upon occurrence of a dangerous situation during the work in which a heavyweight object is moved such as pipe laying using an excavator mounted with a hybrid actuator (i.e., electro-hydraulic actuator: EHA). 
     BACKGROUND OF THE INVENTION 
     In general, an electro-hydraulic excavator expands and contracts a boom cylinder or the like by a hydraulic fluid discharged from an electro-hydraulic actuator (hydraulic pump-motor) operated according to the drive of an electric motor-generator (hereinafter, referred to as “electric motor”) to manipulate a work apparatus. In other words, the expansion and contraction of the boom cylinder can be controlled according to the forward and reverse rotation of the electric motor. A high pressure is generated in a large chamber of the boom cylinder due to its own weight during a boom-down operation in which the boom descends or is lowered. In addition, the hydraulic pump-motor is driven by the hydraulic fluid fed back thereto from the large chamber of the boom cylinder to cause the electric motor to generate electricity. 
       FIG. 3  is a graph showing the characteristics of the electro-hydraulic actuator (EHA). 
     In  FIG. 3 , a graph curve (a) represents the number of rotations and a torque, which can be generated by the electric motor constituting the electro-hydraulic actuator. A torque that can be generated by the electric motor which was applied with power is substantially equal to a torque that can be applied to the outside during the generation of electricity. 
     In  FIG. 3 , a graph curve (b) represents necessary energy converted into the number of rotations and a torque of the electric motor constituting the electro-hydraulic actuator in the case where an excavator receives a force from an engine to drive the work apparatus. In other words, since the graph curve (a) includes the entire section of the graph curve (b), a hybrid excavator having the electro-hydraulic actuator mounted thereon can generate a driving speed and a force larger than those of a hydraulic excavator that receives a torque from the engine to drive the work apparatus. 
     Meanwhile, in a hybrid excavator, in the case where the work apparatus is decelerated or descends by its own weight such as the boom-down operation, it is not operated by controlling a meter-out valve, but by receiving energy from the engine. For this reason, even when the work apparatus is operated at high speed, it can be stopped at high torque. If the energy is converted into the number of rotations and the torque of the electric motor-generator, it includes a hatched region (d). 
     In other words, during a high speed boom-down operation, the energy is equal to a speed and a torque corresponding to a point (c) where the graph curves (a) and (b) intersect with each other, and thus the work apparatus can be brought to a quick stop by closing the valve in the hydraulic excavator. 
     On the other hand, in the hybrid excavator having the electro-hydraulic actuator mounted thereon, when the work apparatus (i.e., a boom) performs a high speed boom-down operation (in this case, a point (e) requires a pressure higher than that in the point (c) where the graph curves (a) and (b) intersect with each other), the torque of the electric motor-generator being operated cannot be increased any longer, which makes it impossible to bring the work apparatus to a quick stop. 
     For this reason, in the case where a work such as pipe laying is performed with the aid of a worker, the work apparatus is not brought to a quick stop upon occurrence of a dangerous situation, thereby causing a safety accident. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problems 
     Accordingly, the present invention has been made to solve the aforementioned problem occurring in the prior art, and it is an object of the present invention to provide a hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop, which is configured to quickly stop a work apparatus being operated at high speed upon occurrence of a dangerous situation during the work in which a heavyweight object is moved using a hybrid excavator, thereby securing safety of an operator during the work such as pipe laying. 
     Technical Solution 
     To accomplish the above object, in accordance with a first embodiment of the present invention, there is provided a hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop, including: 
     an RCV configured to output a manipulation signal based on a manipulation amount so as to manipulate an work apparatus; 
     a first detection sensor configured to detect the manipulation signal outputted from the RCV based on the manipulation amount and output a detection signal; 
     an electric motor; 
     a second detection sensor configured to detect the number of rotations of an electric motor and output a detection signal; 
     a hydraulic pump-motor connected to the electric motor; 
     a hydraulic cylinder connected to the hydraulic pump-motor and configured to be driven to expand and contract in response to supply of hydraulic fluid thereto; 
     first and second hydraulic valves respectively installed in first and second flow paths between the hydraulic pump-motor and the hydraulic cylinder; 
     a third hydraulic valve installed in a connection path which is connected to first and second branched flow paths that are branch-connected to first and second flow paths on the upper stream sides of the first and second hydraulic valves and first and second flow paths on the lower stream sides of the first and second hydraulic valves, respectively, and configured to compensate for or bypass a flow rate to overcome a difference in flow rates that occurs when forward and reverse rotation of the hydraulic pump-motor is changed due to a difference in cross-sectional area between a large chamber and a small chamber of the hydraulic cylinder; and 
     a control unit configured to receive the manipulation signal of the RCV from the first detection sensor and the number of rotations of the electric motor from the second detection sensor, compare the received manipulation signal and the number of rotations with data of pre-stored working conditions, and output a control signal for application to the first hydraulic valve or the second hydraulic valve to switch the first hydraulic valve or the second hydraulic valve so that the hydraulic fluid is blocked from being fed hack to the hydraulic pump-motor from the hydraulic cylinder to suddenly stop the work apparatus. 
     In according with a more preferable embodiment, the first and second hydraulic valves may be implemented as on off type hydraulic valves that are shifted in response to the application of the control signal thereto from the control unit to open/close the first and second flow paths. 
     The first and second hydraulic valves may be implemented as proportional control type hydraulic valves configured to output a secondary signal pressure that is in proportion to the control signal applied thereto from the control unit. 
     The hybrid excavator may further include a third detection sensor configured to detect the number of rotations of the hydraulic pump-motor and transmit a detection signal to the control unit. 
     The hybrid excavator may further include a fourth detection sensor configured to detect a driving speed of the hydraulic cylinder and transmit a detection signal to the control unit. 
     The first detection sensor may detect a manipulation angle of the RCV during the manipulation of the RCV and transmit a detection signal to the control unit. 
     The first detection sensor may detect a pilot signal pressure that is generated based on the manipulation amount of the RCV during the manipulation of the RCV and transmit a detection signal to the control unit. 
     In accordance with a second embodiment of the present invention, there is provided a hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop, including: 
     an RCV configured to output a manipulation signal based on a manipulation amount so as to manipulate an work apparatus; 
     a first detection sensor configured to detect the manipulation signal outputted from the RCV based on the manipulation amount and output a detection signal; 
     an electric motor; 
     a second detection sensor configured to detect the number of rotations of the electric motor and output a detection signal; 
     a hydraulic cylinder configured to be driven to expand and contract in response to supply of hydraulic fluid thereto; 
     first and second hydraulic pump-motors connected to the electric motor to discharge and supply a flow rate, which is equal to a ratio of a cross-sectional area of a large chamber to a cross-sectional area of a small chamber of the hydraulic cylinder, to the hydraulic cylinder; 
     first and second hydraulic valves respectively installed in first and second flow paths between the first and second hydraulic pump-motors and the hydraulic cylinder; and 
     a control unit configured to receive the manipulation signal of the RCV from the first detection sensor and the number of rotations of the electric, motor from the second detection sensor, compare the received manipulation signal and the number of rotations with data of pre-stored working conditions, and output a control signal for application to the first hydraulic valve or the second hydraulic valve to switch the first hydraulic valve or the second hydraulic valve so that the hydraulic fluid is blocked from being fed back to the first and second hydraulic pump-motors from the hydraulic cylinder to cause the work apparatus to be brought to a quick stop. 
     In according with a more preferable embodiment, the hybrid excavator may further include fifth and sixth detection sensors configured to detect the numbers of rotations of each of the first and second hydraulic pump-motors and transmit detection signals to the control unit. 
     Advantageous Effect 
     The hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop in accordance with embodiments of the present invention as constructed above has the following advantages. 
     It is possible to quickly stop a work apparatus being operated at high speed upon occurrence of a dangerous situation during the work in which a heavyweight object is moved such as pipe laying using a hybrid excavator, thereby protecting a worker from a safety accident and securing safety of hybrid equipment when the work is performed with the aid of the worker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a circuit diagram showing a use state of a hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop in accordance with a first embodiment of the present invention; 
         FIG. 2  is a circuit diagram showing a use state of a hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop in accordance with a second embodiment of the present invention; and 
         FIG. 3  is a graph showing the characteristics of an electro-hydraulic actuator. 
     
    
    
     EXPLANATION ON REFERENCE NUMERALS OF MAIN ELEMENTS IN THE DRAWINGS 
     
         
           10 ; first detection sensor 
           11 ; electric motor 
           12 ; second detection sensor 
           13 ; hydraulic pump-motor 
           14 ; hydraulic cylinder 
           15 ; first path 
           16 ; second path 
           17 ; first hydraulic valve 
           18 ; second hydraulic valve 
           19 ; first branched flow path 
           20 ; second branched flow path 
           21 ; connection path 
           22 ; third hydraulic valve 
           23 ; third detection sensor 
           24 ; fourth detection sensor 
           25 ; first hydraulic pump-motor 
           26 ; second hydraulic pump-motor 
       
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     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. 
     A hybrid excavator including a device that brings an electro-hydraulic actuator (EHA) mounted thereon to a quick stop in accordance with a first embodiment of the present invention as shown in  FIG. 1 , includes: 
     an RCV (remote control valve)  9  that outputs a manipulation signal based on a manipulation amount so as to manipulate an work apparatus  7  such as a boom  1  or the like; 
     a first detection sensor  10  that detects the manipulation signal outputted from the RCV  9  based on the manipulation amount and output a detection signal; 
     an electric motor-generator (hereinafter, referred to as “electric motor”)  11 ; 
     a second detection sensor  12  that detects the number of rotations of the electric motor  11  and output a detection signal; 
     a hydraulic pump-motor  13  that is connected to the electric motor  11 ; 
     a hydraulic cylinder  14  that is connected to the hydraulic pump-motor  13  and is driven to expand and contract in response to supply of hydraulic fluid thereto; 
     first and second hydraulic valves  17  and  18  that are respectively installed in first and second flow paths  15  and  16  between the hydraulic pump-motor  13  and the hydraulic cylinder  14 ; 
     a third hydraulic valve  22  that is installed in a connection path  21  which is connected to first and second branched flow paths  19  and  20  that are branch-connected to first and second flow paths  15   a  and  16   a  on the upper stream sides of the first and second hydraulic valves  17  and  18  and first and second flow paths  15   b  and  16   b  on the lower stream sides of the first and second hydraulic valves  17  and  18 , respectively, and is configured to compensate for or bypass a flow rate to overcome a difference in flow rates that occurs when forward and reverse rotation of the hydraulic pump-motor  13  is changed due to a difference in cross-sectional area between a large chamber and a small chamber of the hydraulic cylinder  14 ; and 
     a control unit (not shown) that receives the manipulation signal of the RCV from the first detection sensor  10  and the number of rotations of the electric motor from the second detection sensor  12 , compares the received manipulation signal and the number of rotations with data of pre-stored working conditions, and outputs a control signal for application to the first hydraulic valve  17  or the second hydraulic valve  18  to switch the first hydraulic valve  17  or the second hydraulic valve  18  so that the hydraulic fluid is blocked from being fed back to the hydraulic pump-motor  13  from the hydraulic cylinder  14  to cause the work apparatus (for example, referring to “boom”) descending at high speed to be brought to a quick stop. 
     The first and second hydraulic valves  17  and  18  are implemented as on/off type hydraulic valves that are shifted in response to the application of the control signal thereto from the control unit to open/close the first and second flow paths  15  and  16 . 
     The first and second hydraulic valves  17  and  18  are implemented as proportional control type hydraulic valves that output a secondary signal pressure that is in proportion to the control signal applied thereto from the control unit. 
     The hybrid excavator further includes a third detection sensor  23  that detects the number of rotations of the hydraulic pump-motor  13  and transmits a detection signal to the control unit. 
     The hybrid excavator further includes a fourth detection sensor  24  that detects a driving speed of the hydraulic cylinder  14  and transmits a detection signal to the control unit. 
     The first detection sensor  10  detects a manipulation angle of the RCV during the manipulation of the RCV by an operator and transmits a detection signal to the control unit. 
     The first detection sensor  10  detects a pilot signal pressure that is generated based on the manipulation amount of the RCV during the manipulation of the RCV by an operator and transmits a detection signal to the control unit. 
     In this case, the configuration of the work apparatus  7 , which includes a boom  1 , an arm  2 , and a bucket  3 , and is driven by a boom cylinder  14 , an arm cylinder  5 , and a bucket cylinder  6 , and an operator&#39;s cab  8  is the same as that of an excavator in the art to which the present invention pertains, and thus the detailed description of the configuration and operation of the work apparatus  7  and the operator&#39;s cab  8  will be omitted to avoid redundancy. 
     Hereinafter, Hereinafter, a use example of the hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop in accordance with a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     As shown in  FIG. 1 , in the case where an operator manipulates an RCV  9  to descend the work apparatus at high speed in order to lift and carry a heavyweight object using the boom as in a pipe-laying work, a detection signal outputted by the first detection sensor  10  that detects a manipulation signal of the RCV  9  during the manipulation of the RCV  9  is transmitted to the control unit. In addition, a detection signal outputted by the second detection sensor  12  that detects the number of rotations of the electric motor  11  is transmitted to the control unit. 
     Thus, the control unit receives the manipulation signal of the RCV by the operator from the first detection sensor  10  and the number of rotations of the electric motor front the second detection sensor  12 , and compares the received manipulation signal and the number of rotations with data of pre-stored working conditions. Thereafter, if the electric motor  11  is driven at a speed more than a predetermined speed, the control unit outputs a control signal for application to the first hydraulic valve  17  installed in the first flow path  15  or the second hydraulic valve  18  installed in the second flow path  15  to switch the first hydraulic valve  17  or the second hydraulic valve  18 . Thus, the first hydraulic valve  17  or the second hydraulic valve  18  is switched to cause the first flow path  15  or the second flow path  16  to be interrupted, so that the hydraulic fluid is blocked from being fed back to the hydraulic pump-motor  13  from the hydraulic cylinder (i.e., boom cylinder)  14  along the first and second flow path  15  and  16 , and thus the boom descending at high speed can be brought to a quick stop. 
     When forward and reverse rotation of the hydraulic pump-motor  13  is changed to supply the hydraulic fluid front the hydraulic pump-motor  13  to a large chamber of the hydraulic cylinder  14  via the second flow path  16  or a small chamber of the hydraulic cylinder  14  via the first flow path  15 , a difference in flow rates may occur due to a difference in cross-sectional area between the large chamber and the small chamber of the hydraulic cylinder  14 . 
     In other words, when the hydraulic fluid from the hydraulic pump-motor  13  is supplied to the large chamber of the hydraulic cylinder  14  via the second flow path  16  and the hydraulic fluid from the small chamber of the hydraulic cylinder  14  is fed back to the hydraulic pump-motor  13  via the first flow path  15  to cause the hydraulic cylinder  14  to be driven to expand, a flow rate of the hydraulic fluid fed back to the hydraulic pump-motor  13  from the small chamber of the hydraulic cylinder  14  is lower than that of the hydraulic fluid supplied to the large chamber of the hydraulic cylinder  14 , and thus a deficit flow rate is compensated for by the third hydraulic valve  22 . That is, when the third hydraulic valve  22  is shifted upwardly on the drawing sheet, the hydraulic fluid flowing on the first flow path  15  sequentially passes through the third hydraulic valve  22  and the connection path  21  in this order, and then joins the hydraulic fluid flowing on the second flow path  16  and is introduced into the large chamber of the hydraulic cylinder  14 . 
     On the other hand, when the hydraulic fluid from the hydraulic pump-motor  13  is supplied to the small chamber of the hydraulic cylinder  14  via the first flow path  15  and the hydraulic fluid from the large chamber of the hydraulic cylinder  14  is fed back to the hydraulic pump-motor  13  via the second flow path  16  to cause the hydraulic cylinder  14  to be driven to contract, a flow rate of the hydraulic fluid fed back to the hydraulic pump-motor  13  from the large chamber of the hydraulic cylinder  14  is higher than that of the hydraulic fluid supplied to the small chamber of the hydraulic cylinder  14 , and thus a surplus flow rate is by-passed by the third hydraulic valve  22 . That is, when the third hydraulic valve  22  is shifted downwardly on the drawing sheet, the hydraulic fluid flowing on the second flow path  16  sequentially passes through the first branched flow path  19 , the third hydraulic valve  22 , and a drain line  30  in this order, and then is drained to a hydraulic tank T. 
     A hybrid excavator including a device that brings an electro-hydraulic actuator (EHA) mounted thereon to a quick stop in accordance with a second embodiment of the present invention as shown in  FIG. 2 , includes: 
     an RCV  9  that outputs a manipulation signal based on a manipulation amount so as to manipulate an work apparatus  7  such as a boom  1  or the like; 
     a first detection sensor  10  that detects the manipulation signal outputted from the RCV  9  based on the manipulation amount and output a detection signal; 
     an electric motor  11 ; 
     a second detection sensor  12  that detects the number of rotations of the electric motor  11  and output a detection signal; 
     a hydraulic cylinder  14  that is driven to expand and contract in response to supply of hydraulic fluid thereto; 
     first and second hydraulic pump-motors  25  and  26  that are connected to the electric motor to discharge and supply a flow rate, which is equal to a ratio of a cross-sectional area of a large chamber to a cross-sectional area of a small chamber of the hydraulic cylinder  14 , to the hydraulic cylinder  14 ; 
     first and second hydraulic valves  17  and  18  that are respectively installed in first and second flow paths  15  and  16  between the first and second hydraulic pump-motors  25  and  26  and the hydraulic cylinder  14 ; and 
     a control unit (not shown) that receives the manipulation signal of the RCV from the first detection sensor  10  and the number of rotations of the electric motor from the second detection sensor  12 , compares the received manipulation signal and the number of rotations with data of pre-stored working conditions, and outputs a control signal for application to the first hydraulic valve  17  or the second hydraulic valve  18  to switch the first hydraulic valve  17  or the second hydraulic valve  18  so that the hydraulic fluid is blocked from being fed back to the first and second hydraulic pump-motors  25  and  26  from the hydraulic cylinder  14  to cause the work apparatus to be brought to a quick stop. 
     In according with a more preferable embodiment, the hybrid excavator further includes fifth and sixth detection sensors  27  and  28  that detects the numbers of rotations of each of the first and second hydraulic pump-motors  25  and  26  and transmits detection signals to the control unit. 
     In this case, the configuration of the excavator in accordance with the second embodiment shown in  FIG. 2  is the same as that of the excavator in accordance with the first embodiment shown in  FIG. 1  except the first and second hydraulic pump-motors  25  and  26  having a discharge flow rate, which is equal to a ratio of a cross-sectional area of a large chamber to a cross-sectional area of a small chamber of the hydraulic cylinder  14 . Thus, the detailed description of the same configuration and operation thereof will be omitted avoid redundancy, and the same elements are denoted by the same reference numerals. 
     Hereinafter, a use example of the hybrid excavator including a device that brings an electro-hydraulic actuator (EHA) mounted thereon to a quick stop in accordance with the second embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     As shown in  FIG. 2 , it is possible for the first and second hydraulic pump-motors  25  and  26  to overcome a difference in flow rates that occurs when forward and reverse rotation of the first and second hydraulic pump-motors  25  and  26  is changed due to a difference in cross-sectional area between the large chamber and the small chamber of the hydraulic cylinder  14 . In other words, the first and second hydraulic pump-motors  25  and  26  have a discharge flow rate, which is equal to a ratio of a cross-sectional area of the large chamber to a cross-sectional area of the small chamber of the hydraulic cylinder  14 . Thus, even when the cross-sectional areas between the large chamber and the small chamber of the hydraulic cylinder  14  is different from each other, the hydraulic fluid can be supplied to the hydraulic cylinder  14  under the optimal conditions. 
     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 
     As described above, according to the hybrid excavator including a device that brings an electro-hydraulic actuator mounted thereon to a quick stop in accordance with embodiments of the present invention, when an operator manipulates the work apparatus, particularly lowers the work apparatus at high speed while watching the movement of a heavyweight object and a worker using a hybrid excavator such as a pipe-laying work, it is possible to quickly stop the work apparatus being operated at high speed upon occurrence of an unexpected dangerous situation, thereby protecting the worker from a safety accident and securing safety of hybrid equipment.