Abstract:
The present invention A hydraulic control valve with a regeneration function, including a main body formed of a supply fluid passage to which pressurized fluid is supplied, at least one port, a tank fluid passage for discharging the pressurized fluid to an outside storage tank, and a first regeneration fluid passage; a spool movably installed inside the main body for controlling the flow of the pressurize fluid, and including a second generation fluid passage formed therein; and a regeneration valve for returning only part of the pressurized fluid of the first regeneration fluid passage to the tank fluid passage to maintain pressure of the first regeneration fluid passage at a designated value, and for supplying the pressurized fluid to the second regeneration fluid passage, and if the pressure of the supply fluid passage is higher than a predetermined pressure, changing the pressure of the first regeneration fluid passage in accordance with a change of the pressure of the supply fluid passage.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to a hydraulic control valve with a regeneration function for heavy construction equipment such as an excavator, more specifically, to a hydraulic control valve capable of maintaining the pressure in a regeneration fluid passage, irrespective of changes in the discharge flow rate of a hydraulic pump, the location of working equipment, the regeneration flow rate and the return flow rate. 
   2. Description of the Related Art 
   Traditionally, a hydraulic control valve for use in heavy construction equipment, e.g., an excavator, had two functions: firstly, it controls the flow of pressurized fluid discharged from a hydraulic pump and supplies it to an actuator, e.g., a hydraulic cylinder; and secondly, it sends pressurized fluid returning during the operation of the hydraulic cylinder to a tank. With technical advances, a hydraulic control valve of recent years now has a regeneration function, whereby part of the pressurized fluid returning to the tank is supplied back to the hydraulic cylinder. 
   As aforementioned, the hydraulic control valve with a regeneration function sends the return pressurized fluid en route to the tank back to the hydraulic cylinder. In result, the work speed and the energy efficiency can be increased. Besides, it is possible to prevent the so-called cavitation phenomenon generated by insufficiency of a flow rate supplied to the chamber of hydraulic cylinder due to the transport speed of the hydraulic cylinder increased by the self-weight of the working equipment. Cavitation usually occurs at insufficiency of a flow rate into the chamber of the hydraulic cylinder and causes each component&#39;s life to be shorten. When actions for cavitation preventing are taken, the components&#39; life can thus be extended. 
     FIG. 1  is a cross-sectional view of a related art hydraulic control valve with a regeneration function;  FIG. 2  is a partial exploded view of a regeneration valve in  FIG. 1 ; and  FIG. 3  is a schematic view illustrating an example of the operation of a working equipment. The following will now describe the operation of a hydraulic control valve  3 . 
   A pressurized fluid discharged from a hydraulic pump  1  is supplied to the hydraulic control valve  3  through a feed line (or supply line)  2 . When a spool  7  inside the hydraulic control valve  3  switches to the left or right side, the pressurized fluid of the hydraulic pump  1  is supplied to a first port  4  or a second port  5  via a supply fluid passage  6 . 
   The first port  4  is connected to a large chamber  8   a  of a hydraulic cylinder  8 , and the second port  5  is connected to a small chamber  8   b  thereof. Hence, if the spool  7  switches to the right side, pressurized fluid is supplied to the large chamber  8   a  through the first port  4 , and the hydraulic cylinder  8  is extended to the right side. Meanwhile, the pressurized fluid discharged from the small chamber  8   b  returns to a reservoir or a storage tank T by way of the second port  5  and a tank fluid passage  10   b.    
   If the spool  7  switches to the left side, pressurized fluid is supplied to the small chamber  8   b  through the second port  5 , and the hydraulic cylinder  8  is retracted to the left side. Meanwhile, the pressurized fluid discharged from the large chamber  8   a  returns to the tank T by way of the first port  4  and the tank fluid passage  10   a.    
   When the spool  7  switches to the right side, as shown in  FIG. 3 , the hydraulic cylinder  8  is extended and an ‘arm-in’ is performed. Here, the pressurized fluid discharged from the small chamber  8   b  of the hydraulic cylinder  8  is supplied to the supply fluid passage  6  by the regeneration valve  12 . Thus, by supplying part of this pressurized fluid en route to the tank back to the supply side (e.g., the hydraulic cylinder), it becomes possible to increase energy efficiency. 
   The pressurized fluid discharged from the small chamber  8   b  sequentially passes through the second port  5 , first regeneration fluid passage  13 , connection fluid passage  14 , return fluid passage  16 , and tank fluid passage  10   b . Because the original area of the return fluid passage  16  is small, a pressure is created in the first regeneration fluid passage  13 . If this pressure is higher than the pressure in a second generation fluid passage  15 , a poppet  9  housed in the spool  7  moves to the right side, and the pressurized fluid of the first generation fluid passage  13  flows into the direction of the supply fluid passage  6  through the second regeneration fluid passage  15 . 
   On the other hand, if a large force is required to operate the hydraulic cylinder  8 , the pressure of the second port  5  should be lower than the pressure of the first port  4 . That is, the lower the pressure of the first regeneration fluid passage  13 , the larger the operational force for the hydraulic cylinder  8 . 
   The regeneration spool  22  is elastically supported by a spring  23 , and its front part comes in contact with a piston  21  which moves by the pressure from the supply fluid passage  6 . Thus, if the pressure of the supply fluid passage  6  is higher than a designated value the piston  21  of the regeneration valve  12  is pressed by the pressure from the supply fluid passage  6 , and the regeneration spool  22  moves to the right side. In result, the area of the return fluid passage  16  gradually increases and the pressure of the first regeneration fluid passage  13  is lowered accordingly, providing a larger force for the operation of the hydraulic cylinder  8 . 
   The change of pressure in the first regeneration fluid passage  13 , the flow rate passing through the first regeneration fluid passage  13  and the tank fluid passage  10   b , and the area of the return fluid passage  16  satisfy the following equation: 
   
     
       
         
           
             Δ 
             ⁢ 
             
                 
             
             ⁢ 
             P 
           
           = 
           
             C 
             × 
             
               
                 ( 
                 
                   Q 
                   A 
                 
                 ) 
               
               2 
             
           
         
       
     
       
       
         
           ΔP: The change of pressure in the first regeneration fluid passage  13 ; 
           C: Flow coefficient; 
           Q: Flow rate from the first regeneration fluid passage  13  to the tank fluid passage  10   b ; and 
           A: Variable area of the return fluid passage  16 . 
         
       
     
  
   Here, the flow rate Q is related to several variables, e.g., the feed rate of the hydraulic pump  1 , the location of a working equipment shown in  FIG. 3  for example, and the flow regenerated through the second regeneration fluid passage  15 . 
   The change of pressure of the first regeneration fluid passage  13  and the pressure in the supply fluid passage  6  react sensitively to the flow rate Q and the area A. The change of the pressures in the first and second ports  4 ,  5  make the motion of the hydraulic cylinder unnatural and awkward (this phenomenon is called hunting) as a result of poor hydraulic stability. Therefore, it becomes very difficult to control the motion of the hydraulic cylinder  8 . 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a hydraulic control valve with a regeneration function, capable of maintaining the pressure in a regeneration fluid passage, irrespective of changes in the discharge flow rate of a hydraulic pump, the location of working equipment, the regeneration flow rate and the return flow rate. 
   To achieve the above object, there is provided a hydraulic control valve equipped with a regeneration valve, in which the regeneration valve regenerates the return fluid from the hydraulic cylinder and supplies it to a supply fluid passage, and maintains the pressure of a regeneration fluid passage at a constant level in accordance with the change of pressure of the supply fluid passage. 
   Accordingly, the present invention provides a hydraulic control valve with a regeneration function, including: a main body formed of a supply fluid passage to which pressurized fluid from outside is supplied, at least one port for supplying the pressurized fluid in the supply fluid passage to an actuator or receiving the return fluid from the actuator, a tank fluid passage for discharging the return fluid from the actuator to an outside storage tank, and a first regeneration fluid passage for supplying part of the return fluid from the actuator to the supply fluid passage; a spool movably installed inside the main body for controlling the flow of pressurized fluid by opening/closing the connections of the supply fluid passage, the port(s), the tank fluid passage, and the first regeneration fluid passage, respectively, and comprising a second generation fluid passage that supplies the pressurized fluid of the first regeneration fluid passage to the supply fluid passage; and a regeneration valve installed between the first regeneration fluid passage and the tank fluid passage for returning only part of the pressurized fluid of the first regeneration fluid passage to the tank fluid passage to maintain pressure of the first regeneration fluid passage at a designated value, and for supplying the pressurized fluid to the second regeneration fluid passage; and if the pressure of the supply fluid passage is higher than a predetermined pressure, changing the pressure of the first regeneration fluid passage in accordance with a change of the pressure of the supply fluid passage. 
   Preferably, the regeneration valve includes a sleeve installed between the first regeneration fluid passage and the tank fluid passage, and formed of a first fluid passage communicating with the first regeneration fluid passage and a second fluid passage communicating with the tank fluid passage; a main poppet movably installed inside the sleeve by being elastically supported by a first spring for changing an opening area of the second fluid passage, and comprising a back pressure chamber formed therein; a pilot poppet movably installed inside the sleeve by being elastically supported by a second spring, and if pressure of the back pressure chamber exceeds a predetermined pressure, discharging pressurized fluid of the back pressure chamber to the tank fluid passage; a pilot piston movably installed on a piston passage formed in front of the main poppet to be in contact with the front end portion of the pilot poppet; and a piston slidably installed on the front side of the sleeve for the rear end of the piston to be in contact with the front end portion of the pilot piston, and if the pressure of the supply fluid passage applied to the front end portion of the pilot piston exceeds the predetermined pressure set for the pilot poppet, moving the pilot piston and the pilot poppet backward. 
   More preferably, the hydraulic control valve of the present invention further includes a pressure regulator installed on the rear end of the regeneration valve for assisting the second spring to change the predetermined pressure set for the pilot poppet. 
   More preferably, the pressure regulator is operated by a signal pressure inputted from outside. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a cross-sectional view of a related art hydraulic control valve with a regeneration function in a partly sectional and partly schematic environment; 
       FIG. 2  is a partial exploded view of a regeneration valve in  FIG. 1 ; 
       FIG. 3  is a schematic view illustrating an example of the operation of a working equipment 
       FIG. 4  is a cross-sectional view of a hydraulic control valve according to one embodiment of the present invention in a partly sectional and partly schematic environment; 
       FIG. 5  is a partial exploded view of a regeneration valve in  FIG. 4 ; 
       FIG. 6  graphically illustrates the change of pressure in the hydraulic control valve according to one embodiment of the present invention; 
       FIG. 7  is a partial cross-sectional view of a regeneration valve for a hydraulic control valve according to another embodiment of the present invention; and 
       FIG. 8  is a partial cross-sectional view of a regeneration valve in a hydraulic control valve according to yet another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. For example, pressure adjustment valve caps are shown at  140 ,  240  and  340  in  FIGS. 5 ,  7  and  8 , respectively. 
     FIG. 4  is a cross-sectional view of a hydraulic control valve according to one embodiment of the present invention, and  FIG. 5  is a partial exploded view of a regeneration valve in the hydraulic control valve of  FIG. 4 . 
   The hydraulic control valve with a regeneration function of the present invention supplies pressurized fluid to a hydraulic cylinder  8 , one of actuators, and controls the operation thereof. The hydraulic control valve includes a main body  103  in which fluid passages for pressurized fluid are formed; a spool  107  slidably installed in the main body  103  for supplying pressurized fluid to the hydraulic cylinder  8 ; and a regeneration valve  112  for regenerating part of the pressurized fluid returning from the hydraulic cylinder  8 . 
   Examples of the fluid passages formed in the main body  103  include a supply fluid passage  106  to which pressurized fluid discharged from a hydraulic pump  1  is supplied; a first port  104  and a second port  105  for supplying the pressurized fluid in the supply fluid passage  106  to the hydraulic cylinder  8 , or receiving the return fluid from the hydraulic cylinder  8 ; and tank fluid passages  110   a ,  110   b  for discharging the return fluid from the hydraulic cylinder  8  to a storage tank T (e.g., reservoir). Further, the main body  103  includes a first regeneration fluid passage  113  for supplying pressurized fluid returning from the hydraulic cylinder  8  to the supply fluid passage  106 , and regenerating the return fluid. 
   The spool  107  is slidably installed (e.g., in the lateral direction on the drawing) inside the main body  103 . The spool  107  opens/closes the connections of the supply fluid passage  106 , the first and second ports  104 ,  105 , the tank fluid passage  110   a,   110   b, and the first regeneration fluid passage  113 , respectively, in order to control the flow of pressurized fluid. In addition, inside the spool  107  is a second regeneration fluid passage  115  that supplies the pressurized fluid of the first regeneration fluid passage  113  to the supply fluid passage  106 . A poppet  109  is slidably installed in the longitudinal direction of the second regeneration fluid passage  115 . 
   The regeneration valve  112  is installed between the first regeneration passage  113  and the tank fluid passage  110   b  so that only a part of pressurized fluid in the first regeneration passage  113  returns to the tank fluid passage  110   b . As a result, the pressure of the regeneration passage  113  is maintained regularly, and the regeneration function of supplying the pressurized fluid to the second regeneration passage  115  is carried out. 
   The regeneration valve  112  includes a sleeve  120  installed between the first regeneration fluid passage  113  and the tank fluid passage  110   b  inside the main body  103 ; a main poppet  134  slidably installed in the sleeve  120 ; a pilot poppet  133  installed on the rear side of the main poppet  134 ; a pilot piston  136  slidably installed, passing through the main poppet  134 ; and a piston  135  slidably installed on the front side of the sleeve  120 . 
   The sleeve  120  of the regeneration valve  112  is formed of three bodies, namely, a first body  121 , a second body  122 , and a third body  123 , being sequentially connected. Inside the second body  122  is a first fluid passage  124  communicating with the first regeneration fluid passage  113 , and a second fluid passage  125  communicating with the tank fluid passage  110   b.    
   The main poppet  134 , being elastically supported by a first spring  137 , is slidably installed inside the sleeve  120 . If the main poppet  134  translates laterally inside the sleeve  120 , the opening area of the second fluid passage  125  changes. Moreover, the main poppet  134  has a back pressure chamber  132 , that opens towards the back. 
   The pilot poppet  133 , being elastically supported by a second spring  138 , is slidably installed inside the sleeve  120 . 
   The pressure from the supply fluid passage  106  moves the piston  135  to the right side, and because of this, the pilot piston  136  and the pilot poppet  133  in contact with the piston  135  move to the right side as well. 
   Therefore, as the pilot poppet  133  moves backward, pressurized fluid of the back pressure chamber  132  passes through a discharge fluid passage  150 , and is discharged through a separate external drain  151 , or (although not shown) if the discharge fluid passage  150  is communicated with the tank fluid passage  110   b  the pressurized fluid of the back pressure chamber  132  can be discharged to the storage tank T. In such case, the main poppet  134  also moves to the right side, and the pressurized fluid of the first regeneration fluid passage  113  travels to the connection fluid passage  114  and the second fluid passage  125 , and eventually is discharged to the tank fluid passage  110   b.    
   The rear end portion of the pilot piston  136  comes in contact with the front end portion of the pilot poppet  133 , whereas the front end portion of the pilot piston  136  passes through a piston passage  134   b  formed in front of the main poppet  134 , whereby the pilot piston  136  can slide with respect to the main poppet  134 . 
   The rear end portion of the piston  135  comes in contact with the front end portion of the pilot piston  136 , whereas the front end portion of the piston  135  is movably inserted into a front passage  135   b  of the first body  121  of sleeve  120 . Thus, the pressure of the supply fluid passage  106  is applied to the front end portion of the piston  135 . When the pressure of the supply fluid passage  106  exceeds a predetermined pressure for the pilot poppet  133 , the piston  135  pressurizes the pilot piston  136  and the pilot poppet  133  backward. 
   The following will now explain the operation of the hydraulic control valve with a regeneration function. 
   Pressurized fluid discharged from the hydraulic pump  1  is supplied to the hydraulic control valve  103  through the supply fluid passage  2 . As the spool  107  switches to the right or the left side, the pressurized fluid of the hydraulic pump  1  is supplied to the first port  104  or the second port  105  through the supply fluid passage  106 . 
   If the spool  107  switches to the right side, the pressurized fluid is supplied to the large chamber  8   a  through the first port  104 . In result, the hydraulic cylinder  8  is extended to the right side, and the pressurized fluid discharged from the small chamber  8   b  returns to the storage tank T via the second port  105  and the tank fluid passage  10   b . Here, part of the return fluid is regenerated by the regeneration valve  112  and flows into the supply fluid passage  106 . 
   If the pressure formed in the supply fluid passage  106  is higher than the pressure of the pilot poppet  133  predetermined by the second spring  138 , the pilot poppet  133  will be shift to right so that the back pressure chamber  132  is opened to the tank passage portion  110   b . This means to drop the pressure of regeneration passage  113 . Therefore, the pressure of supply passage  106  can be used to move the cylinder  8 , it is connected an attachment, with more power. 
   In another case, the regeneration process is performed when the pressure of the supply fluid passage  106  is lower than the predetermined pressure. For instance, the pressurized fluid discharged from the small chamber  8   b  of the hydraulic cylinder  8  is supplied to the first regeneration fluid passage  113  via the second port  105 . Then, it sequentially passes through the first and second fluid passages  124 ,  125  of the regeneration valve  112 , and returns to the storage tank T through the tank fluid passage  110   b.    
   Because the second passage  125  is blocked at first by the main poppet  134 , a pressure is created in the first regeneration fluid passage  113 . If this pressure is higher than the pressure of the second regeneration fluid passage  115 , the poppet  109  installed inside the spool  107  moves to the right side and thus, the pressurized fluid of the first regeneration fluid passage  113  flows into the supply fluid passage  106  through the second regeneration fluid passage  115 . 
   In the course of the regeneration process, if an applied pressure to the back pressure chamber  132  is higher than the predetermined pressure set for the pilot poppet  133  by the second spring  138 , the pilot poppet  133  moves to the right side. Accordingly, the pressure of the back pressure chamber  132  is lowered and at the same time, the pilot piston  136  moves to the left side and the main poppet  134  moves to the right side. In result, the pressurized pressure of the first regeneration fluid passage  113  is discharged to the storage tank  110   b.    
   Thanks to the regeneration function, the pressure of the first regeneration fluid passage  113  is not much affected by the change of the flow rate, but maintains a constant level. Thus, hunting does not occur and the motion of the hydraulic cylinder  8  can be controlled gently. 
   When the hydraulic cylinder  8  is up to a large-load-requiring work, the regeneration valve  112  lowers the pressure of the first regeneration fluid passage  113 . So that the pressure of supply passage  106  is used to move the cylinder  8 , it is connected an attachment, with more power. 
   The pilot poppet  133  is elastically supported by the second spring  138 , and this makes setting pressure predetermined. Meanwhile, the pressure of the supply fluid passage  106  is applied to the front end portion of the piston  135 . If the pressure of the supply fluid passage  106  exceeds the predetermined pressure of the pilot poppet  133 , the piston  135  pressurizes the pilot piston  136  and the pilot poppet  133  backward. 
   Therefore, when the pilot poppet  133  moves backward and thus the pressurized fluid of the back pressure chamber  132  is discharged to the tank fluid passage  110   b , the pressure created in the first regeneration fluid passage  113  is reduced proportionally to an increase of pressure of the supply fluid passage  106 . As a result, the change of pressure of the supply fluid passage  106  connected to the first regeneration fluid passage  113  becomes very small, and the motion of the hydraulic cylinder  8  is stabilized without being unnatural or awkward (i.e., hunting). 
     FIG. 6  graphically illustrates the change of pressure in the hydraulic control valve according to one embodiment of the present invention. In the drawing, PR denotes an applied pressure to the first regeneration fluid passage; Px denotes a signal pressure inputted from outside; P denotes an applied pressure of the supply fluid passage; and A, B and C denote arbitrary input values from outside (A&lt;B&lt;C). 
   As can be seen in  FIG. 6(   a ), the ratio of the pressure of the supply fluid passage  106  to the pressure of the first regeneration fluid passage  113  can be controlled in dependence of the size correlation between the piston  135  and the pilot poppet  133 . 
   Sometimes, there is need to combine the operation of one hydraulic-driven working equipment with another working equipment. In this case, the pressure on the supply side of the hydraulic pump is increased compulsorily to carry out a large work load. This can be realized by other embodiments of the present invention shown in  FIG. 7  and  FIG. 8 , respectively. 
     FIG. 7  is a partial cross-sectional view of a regeneration valve for a hydraulic control valve according to another embodiment of the present invention. 
   In this embodiment, the regeneration valve  212  of a hydraulic control valve is operated additionally by a signal pressure Px inputted from outside. When a signal pressure Px is inputted from outside through a signal-inlet  242 , a pressure piston  243  whose rear side is supported by a third spring  241  pressurizes the rear end of the pilot poppet  133 , whereby the piston  243  together with a second spring  138  changes a predetermined pressure set for the pilot poppet  133 . 
   According to another embodiment of the present invention, when the pressure of a first regeneration fluid passage  113  increased at a result of the applied signal pressure Px, the pressure of a supply fluid passage  106  also increases. In this manner, the combined operation with another working equipment of a large load can be achieved.  FIG. 6(   b ) briefly illustrates the relation between the pressure of the supply fluid passage  106  and the pressure of the first regeneration fluid passage  113 . 
     FIG. 8  is a partial cross-sectional view of a regeneration valve in a hydraulic control valve according to yet another embodiment of the present invention. 
   Similar to the embodiment shown in  FIG. 7 , the regeneration valve  312 , and a cut-off valve  345  connected to the signal-inlet  342  is installed on a signal passage  344  for supplying an external signal pressure Px. 
   If a signal pressure Py is inputted to the cut-off valve  345 , the cut-off valve  345  switches, say, upward as shown in  FIG. 8 , to cut off the input of the signal pressure Px to the signal-inlet  342 . Meanwhile, if the signal pressure Py is not inputted to the cut-off valve  345 , the cut-off valve  345  switches, say, downward as shown in  FIG. 8 , and allows the signal pressure Px to be inputted to the signal-inlet  342 . In result, the front end portion of a pressure piston  343  together with a second spring  138  pressurize the rear end portion of a pilot poppet  133 , and change a predetermined pressure set for the pilot poppet  133 . 
   According to yet another embodiment of the present invention, if a large load is applied to the work all the time, the signal pressure Px can always be applied to the signal-inlet  342  anytime to increase the pressure of the supply fluid passage  106 . And, when another work equipment requesting a large load is used, the signal pressure Px is cut off and one makes sure that the signal pressure Px is not inputted to the signal-inlet  342 . In this manner, the pressure of the supply fluid passage  106  will not be high. 
   As described above, the hydraulic control valve with the regeneration function according to the present invention is capable of maintaining the pressure in a regeneration fluid passage, irrespective of changes in the discharge flow rate of a hydraulic pump, the location of working equipment, the regeneration flow rate and the return flow rate, so that hunting of the actuator rarely occurs. 
   While the invention has been described in conjunction with various embodiments, they are illustrative only. Accordingly, many alternative, modifications and variations will be apparent to persons skilled in the art in light of the foregoing detailed description. The foregoing description is intended to embrace all such alternatives and variations falling with the spirit and broad scope of the appended claims.