Abstract:
A pressure control system of a torque control device comprises an electronic control device TCU ( 100 ), a control pressure regulating valve ( 110 ), a fixed pressure oil passage, a pressure switching valve ( 120 ) and a jointing pressure regulating valve ( 130 ). When a control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects a jointing pressure with a feedback interface ( 135 ) of the jointing pressure regulating valve ( 130 ) and a jointing pressure regulating valve ( 130 ) outputs the jointing pressure in direct proportion with a control signal; when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve ( 120 ) connects a fixed pressure with the feedback interface ( 135 ) of the jointing pressure regulating valve and the jointing pressure regulating valve ( 130 ) communicates a main pressure interface ( 131 ) with a jointing pressure interface ( 136 ) to increase the acting area of the control pressure of the jointing pressure regulating valve ( 130 ) through switching of the pressure switching valve ( 120 ) or reduce the feedback area, so as to increase the change slope of the jointing pressure and ensure enough torque capacity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US national phase entry of PCT Application No. PCT/CN2013/081284, entitled “PRESSURE CONTROL SYSTEM OF TORQUE CONTROL DEVICE” filed Aug. 12, 2013. The disclosure of said application is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to the field of hydraulic control, in particular to the field of hydraulic control to an automatic transmission. 
       BACKGROUND 
       [0003]    By now, the following existing techniques have been searched: 1. CN200510127583.5, entitled “Pressure Control Systems for Automatic Transmissions”; 2. CN200510117492.3, entitled “Hydraulic Control Systems for Automatic Transmission Units for Vehicles”; 3. U.S. Pat. No. 6,591,958, entitled “Pressure Control Apparatus for a Torque-transmitting Mechanism”; and 4. CN200510084452.3, entitled “Regulating valves of torque-transmitting mechanisms and method for engaging torque-transmitting mechanisms”. 
         [0004]    In an automatic transmission, the transmission torque of the torque control devices such as clutches, brakes or brake bands mainly depends on a jointing pressure of a piston chamber thereof. During the jointing process of the torque control devices such as clutches, the transmission torque thereof is controlled by controlling the jointing pressure. A TCU (short for automatic Transmission Control Unit, alternatively translated as Electronic Control Device) outputs a signal to control an electromagnetic valve, and a pressure of the electromagnetic valve controls a pressure regulating valve to provide this jointing pressure, wherein the pressure of the electromagnetic valve serves as a pilot control valve. Thus, if it is desired to ensure an adequate torque capacity, the resolution of a pressure control will reduce, which is disadvantageous for the precise control to a torque device. 
       SUMMARY 
       [0005]    An object of the present disclosure is to provide a control system which is advantageous for precise control to a pressure of a torque control device. 
         [0006]    To achieve above object, the present disclosure adopts any one of the following technical solutions. 
         [0007]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving a jointing pressure, an input interface for receiving a fixed pressure, an output interface connected to a feedback interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, a feedback interface and a spring chamber that are located on one side of a valve core of the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, and a control interface located on the other side of the valve core of the jointing pressure regulating valve and connected to the oil passage of the control pressure; and when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects the jointing pressure with the feedback interface of the jointing pressure regulating valve, and the jointing pressure regulating valve outputs a jointing pressure in proportion to the control signal; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects the fixed pressure with the feedback interface of the jointing pressure regulating valve, and the jointing pressure regulating valve allows a main pressure interface to communicate with a jointing pressure interface. 
         [0008]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving a jointing pressure, an input interface for receiving a fixed pressure, an output interface connected to a feedback interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, and a feedback interface and a spring chamber that are located on one side of a valve core of the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve; and when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects the jointing pressure with the feedback interface of the jointing pressure regulating valve, and the jointing pressure control valve outputs a jointing pressure in proportion to the control signal; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects the control pressure with the feedback interface of the jointing pressure regulating valve, and the jointing pressure regulating valve allows a main pressure interface to communicate with a jointing pressure interface. 
         [0009]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving a jointing pressure, an input interface for receiving the control pressure, an output interface connected to a control interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, a feedback interface and a spring chamber that are located on one side of a valve core of the jointing pressure regulating valve and used for receiving a jointing pressure, and a control interface located on the other side of the valve core of the jointing pressure regulating valve and used for receiving an output of the pressure switching valve; and when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects the control pressure with the control interface of the jointing pressure regulating valve, and the jointing pressure regulating valve outputs a jointing pressure in proportion to the control signal; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects the jointing pressure with the control interface of the jointing pressure regulating valve, and the jointing pressure regulating valve allows a main pressure interface to communicate with a jointing pressure interface. 
         [0010]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving a jointing pressure, an input interface for receiving a pressure relief chamber, an output interface connected to a control interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a selecting valve, which consists of a steel ball and has a first input port for receiving the control pressure, a second input port for receiving an output of the pressure switching valve and an output port connected to a control chamber of a jointing pressure regulating valve, the output port being always in communication with an input port having a larger pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, a feedback interface and a spring chamber that are located on one side of a valve core of the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, and a control interface located on the other side of the valve core of the jointing pressure regulating valve and used for receiving an output of the selecting valve; and when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects an oil drainage chamber with an input interface of the selecting valve, the control pressure enters a control chamber of the jointing pressure control valve via the selecting valve, and the jointing pressure control valve outputs a jointing pressure in proportion to the control signal; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects the jointing pressure with an input of the selecting valve, the jointing pressure is connected to the control interface of the jointing pressure regulating valve via the selecting valve, and the jointing pressure regulating valve allows a main pressure interface to communicate with a jointing pressure interface. 
         [0011]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving a jointing pressure, an input interface for receiving a oil drainage chamber, an output interface connected to a control interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, a feedback interface and a spring chamber that are located on one side of a valve core of the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, and a control interface for receiving an output of the pressure switching valve and a second control interface for receiving the control pressure located on the other side of the valve core of the jointing pressure regulating valve; and when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects a pressure relief chamber with the control interface of the jointing pressure regulating valve, and the jointing pressure regulating valve outputs a jointing pressure in proportion to the control signal; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects the jointing pressure with the control interface of the jointing pressure regulating valve, and the jointing pressure regulating valve allows a main pressure interface to communicate with a jointing pressure interface. 
         [0012]    According to above five technical solutions, the control pressure regulating valve is generally an electromagnetic valve. The pressure while the torque control devices are jointed is controlled by a precise control to the control pressure of the electromagnetic valve. In addition, after the torque transmission devices are jointed and when the pressure of the electromagnetic valve exceeds a set valve, a high pressure oil port in the pressure regulating valve is communicated with a piston chamber of the torque control device by means of the pressure switching valve, so as to ensure an adequate torque capacity. 
         [0013]    Two other pressure control systems, which can also achieve the above objective, will be further provided as below. 
         [0014]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving the control pressure, an input interface for receiving a pressure relief chamber, an output interface connected to a reverse control interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, a feedback interface and a spring chamber that are located on one side of a valve core of the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, a control interface located on the other side of the valve core of the jointing pressure regulating valve and connected to the oil passage of the control pressure; and a reverse control interface which has a reverse apply direction to the control interface; when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects the control pressure with the reverse control interface of the jointing pressure regulating valve, and the jointing pressure regulating valve outputs a jointing pressure with a smaller slope; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects the pressure relief chamber with the reverse control interface of the jointing pressure regulating valve, and the jointing pressure regulating valve outputs a jointing pressure with a larger variation slope. 
         [0015]    A pressure control system for a torque control device, the system comprises: an electronic control device (TCU); a control pressure regulating valve for receiving a control signal from the electronic control device (TCU) and outputting a control pressure; a fixed pressure oil passage, which is an oil passage for supplying oil to the control pressure regulating valve; a pressure switching valve, which has an input interface for receiving a jointing pressure, an input interface for receiving a oil drainage chamber, an output interface connected to a feedback interface of a jointing pressure regulating valve, and a control interface located on one side of a valve core of the pressure switching valve and connected to an oil passage of the control pressure; a jointing pressure regulating valve, which has an input interface connected to an oil passage of a system main oil pressure, an output interface of a jointing pressure for a piston chamber of a torque transmission device, a feedback interface and a spring chamber for receiving a pressure output from the pressure switching valve and a second feedback port connected to an output of the pressure switching valve that are located on one side of a valve core of the jointing pressure regulating valve, and a control interface located on the other side of the valve core of the jointing pressure regulating valve and used for receiving the output of the pressure switching valve; and when the control pressure is lower than a set value of a spring of the pressure switching valve, the pressure switching valve connects the jointing pressure with the second feedback port of the jointing pressure regulating valve, a feedback area of the jointing pressure regulating valve is increased, and the jointing pressure regulating valve outputs a jointing pressure with a smaller variation slope and being in proportion to the control signal; and, when the control pressure reaches the set value of the spring of the pressure switching valve, the pressure switching valve connects a pressure relief port with the second feedback port of the jointing pressure regulating valve, the feedback area of the jointing pressure regulation valve is decreased, and the jointing pressure regulating valve outputs a jointing pressure with a larger variation slope and being in proportion to the control signal. 
         [0016]    According to the two technical solutions described above, during the torque transmission devices are jointed, by a switching of the pressure switching valve, the apply area of the control pressure of the jointing pressure regulating valve is reduced or the feedback area is increased, it is advantageous for a precise control to the jointing pressure adopting a jointing pressure with a smaller variation slope and being in proportion to the control pressure of the control pressure regulating valve; Furthermore, after the torque transmission devices are jointed, that is, after there is no relative slip, by a switching of the pressure switching valve, the apply area of the control pressure of the jointing pressure regulating valve is increased or the feedback area is reduced, so that the variation slope of the jointing pressure is increased and an adequate torque capacity is ensured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  and  FIG. 2  are diagrams showing two specific relations between a control pressure and a jointing pressure, respectively; and 
           [0018]      FIGS. 3-9  are schematic diagrams of hydraulic control according to the present disclosure, respectively. 
       
    
    
     DETAILED DESCRIPTION 
     Embodiment 1 
       [0019]    In  FIG. 3 , a pressure control system includes an Electronic Control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve and connected to an oil passage of the control pressure, an input interface  122  located in the pressure switching valve and used for receiving a jointing pressure, an input interface  123  located in the pressure switching valve and used for receiving a fixed pressure, a spring chamber or an oil drainage pressure  124  in the pressure switching valve, an output interface  125  located in the pressure switching valve and connected to a feedback interface of a jointing pressure regulating valve, a valve core  126  in the pressure switching valve, and a spring  127  in the pressure switching valve; and a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve and connected to the oil passage of the control pressure, a pressure relief port  132  in the jointing pressure regulating valve, a pressure relief port  133  in the jointing pressure regulating valve, a control interface  134  located in the jointing pressure regulating valve and connected to a system main oil pressure, a feedback interface and a spring chamber  135  that are located in the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, an output interface  136  located in the jointing pressure regulating valve and used for a jointing pressure of a piston chamber, a valve core  137  in the jointing pressure regulating valve, and a spring  138  in the jointing pressure regulating valve. 
         [0020]    As shown in  FIG. 3 , the electronic control device (TCU)  100  outputs a control signal to the control pressure regulating valve  110 , and the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a control chamber of the jointing pressure regulating valve  130  and a control chamber of the pressure switching valve  120  via the control interface  131  and the control interface  121 . When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring of the pressure switching valve, the input interface  122  and the output interface  125  of the pressure switching valve  120  communicate with each other, and the jointing pressure enters the feedback interface and the spring chamber  135  of the jointing pressure regulating chamber  130  via the input interface  122  and the output interface  125 . The jointing pressure regulating valve  130  outputs a jointing pressure in proportion to the control pressure of the control pressure regulating valve  110 . When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring  127  of the pressure switching valve  120 , the input interface  123  and the output interface  125  of the pressure switching valve  120  communicate with each other, the fixed pressure for supplying oil to the control pressure regulating valve  110  enters the feedback interface  135  of the feedback chamber of the jointing pressure regulating valve  130  via the interfaces  123  and  125 , the valve core  137  of the jointing pressure regulating valve  130  moves rightward, and the control interface  134  is communicated with the output interface  136 , so that the jointing pressure is equal to the system main oil pressure. 
       Embodiment 2 
       [0021]    In  FIG. 4 , the pressure control system includes an electronic control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve and connected to an oil passage of the control pressure, an input interface  122  located in the pressure switching valve and used for receiving a jointing pressure, an input interface  123  located in the pressure switching valve and used for receiving a control pressure, a spring chamber or an oil drainage pressure  124  in the pressure switching valve, an output interface  125  located in the pressure switching valve and connected to a feedback interface of a jointing pressure regulating valve, a valve core  126  in the pressure switching valve, and a spring  127  in the pressure switching valve; and a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve and connected to the oil passage of the control pressure, a pressure relief port  132  in the jointing pressure regulating valve, a pressure relief port  133  in the jointing pressure regulating valve, a control interface  134  located in the jointing pressure regulating valve and connected to a system main oil pressure, a feedback interface and a spring chamber  135  that are located in the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, an output interface  136  located in the jointing pressure regulating valve and used for a jointing pressure of a piston chamber, a valve core  137  in the jointing pressure regulating valve, and a spring  138  in the jointing pressure regulating valve. 
         [0022]    The electronic control device (TCU)  100  outputs a control signal to the control pressure regulating valve  110 , then the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a control chamber of the jointing pressure regulating valve  130  and a control chamber of the pressure switching valve  120  via the control interface  131 , the control interface  121  and the input interface  123 . When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring  127  of the pressure switching valve  120 , the input interface  122  and the output interface  125  of the pressure switching valve  120  communicate with each other, and the jointing pressure enters the feedback interface and the spring chamber  135  of the jointing pressure regulating chamber  130  via the input interface  122  and the output interface  125 . The jointing pressure regulating valve  130  outputs a jointing pressure in proportion to the control pressure of the control pressure regulating valve  110 . When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring  127  of the pressure switching valve  120 , the input interface  123  and the output interface  125  of the pressure switching valve  120  communicate with each other, the control pressure output from the control pressure regulating valve  110  enters the feedback interface and spring chamber  135  of the jointing pressure regulating valve  130  via the input interface  123  and the output interface  125 , the valve core  137  of the jointing pressure regulating valve  130  moves rightward, and a system main oil pressure chamber (i.e., the control interface  134 ) is communicated with a piston chamber of a torque control device (i.e., the output interface  136 ), so that the jointing pressure is equal to the system main oil pressure. 
       Embodiment 3 
       [0023]    In  FIG. 5 , a pressure control system includes an electronic control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve and connected to an oil passage of the control pressure, an input interface  122  located in the pressure switching valve  120  and used for receiving a control pressure, an input interface  123  located in the pressure switching valve and used for receiving a jointing pressure, a spring chamber or an oil drainage pressure  124  in the pressure switching valve  120 , an output interface  125  located in the pressure switching valve and connected to a control interface of a jointing pressure regulating valve, a valve core  126  in the pressure switching valve, and a spring  127  in the pressure switching valve; and a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve and used for receiving an output of the pressure switching valve, a pressure relief port  132  in the jointing pressure regulating valve, a pressure relief port  133  in the jointing pressure regulating valve, a control interface  134  located in the jointing pressure regulating valve and connected to a system main oil pressure, a jointing pressure feedback interface and a spring chamber  135  in the jointing pressure regulating valve, an output interface  136  located in the jointing pressure regulating valve and used for a jointing pressure of a piston chamber, a valve core  137  in the jointing pressure regulating valve, and a spring  138  in the jointing pressure regulating valve. 
         [0024]    The electronic control device (TCU)  100  outputs a control signal to the electromagnetic valve  110 , the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a control chamber of the pressure switching valve  120 , i.e., a control chamber where the control interface  121  is communicated with the input interface  122 . When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring  127  of the pressure switching valve  120 , the input interface  122  and the output interface  125  of the pressure switching valve  120  communicate with each other. 
         [0025]    The control pressure enters a control chamber (i.e., the control interface  131 ) of the jointing pressure regulating valve  130  via the input interface  122  and the output interface  125 . The jointing pressure regulating valve  130  outputs a jointing pressure in proportion to the control pressure of the control pressure regulating valve  110 . When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring  127  of the pressure switching valve  120 , a chamber of the input interface  123  and a chamber of the output interface  125  of the pressure switching valve  120  communicate with each other, the jointing pressure enters the control chamber (i.e., the feedback interface and the spring chamber  135 ) of the jointing pressure regulating valve  130  via the interfaces  123  and  125 , the valve core  137  of the jointing pressure regulating valve  130  moves rightward, and a system main oil pressure chamber (i.e., the control interface  134 ) is communicated with a piston chamber (i.e., the output interface  136 ) of a torque control device, so that the jointing pressure is equal to the system main oil pressure. 
       Embodiment 4 
       [0026]    In  FIG. 6 , a pressure control system includes an electronic control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve  120  and connected to an oil passage of the control pressure, a pressure relief port  122  in the pressure switching valve  120 , an input interface  123  located in the pressure switching valve  120  and used for receiving a jointing pressure, a spring chamber or an oil drainage pressure  124  in the pressure switching valve  120 , an output interface  125  located in the pressure switching valve  120  and connected to a second input port  12  of a selecting valve  140 , a valve core  126  in the pressure switching valve  120 , and a spring  127  in the pressure switching valve  120 ; a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve  130  and used for receiving an output of the selecting valve  140 , a pressure relief port  132  in the jointing pressure regulating valve  130 , a pressure relief port  133  in the jointing pressure regulating valve  130 , a control interface  134  located in the jointing pressure regulating valve  130  and connected to a system main oil pressure, a jointing pressure feedback interface and a spring chamber  135  in the jointing pressure regulating valve  130 , an output interface  136  located in the jointing pressure regulating valve and used for a jointing pressure of a piston chamber, a valve core  137  in the jointing pressure regulating valve  130 , and a spring  138  in the jointing pressure regulating valve  130 ; and a selecting valve  140 , a first input port  141  for receiving a control pressure, a second input port  142  for receiving an output of the pressure switching valve  120 , and an output port  143  of the selecting valve  140 . 
         [0027]    The electronic control device (TCU)  100  outputs a control signal to the control pressure regulating valve  110 , the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a control chamber (i.e., the control interface  121 ) of the pressure switching valve  120  and the first input port  141  of the selecting valve  140 . When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring  127  of the pressure switching valve  120 , the pressure relief port  122  of the pressure switching valve  120  is communicated with the second input port  142  of the selecting valve  140 , and the pressure of an oil drainage chamber enters the second input port (i.e., a control chamber  142 ) of the selecting valve  140  via the interfaces  122  and  125 . The pressure of the control pressure enters the jointing pressure regulating valve  130  via the first input port  141  of the selecting valve  140 , and the control pressure regulating valve outputs a jointing pressure in proportion to the control pressure of the control pressure regulating valve  110 . When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring  127  of the pressure switching valve  120 , the input interface  123  of the pressure switching valve  120  is communicated with a chamber of the output interface  125 , the jointing pressure enters the second input port (i.e., a control chamber  142 ) of the selecting valve via the interfaces  123  and  125 , then enters a control chamber (i.e., the control interface  131 ) of the jointing pressure regulating valve  130  via the selecting valve  140 , the valve core  137  of the jointing pressure regulating valve  130  moves rightward, and the control interface  134  of a system main oil pressure chamber is communicated with the output interface  136  of a piston chamber of a torque control device, so that the jointing pressure is equal to the system main oil pressure. 
       Embodiment 5 
       [0028]    In  FIG. 7 , a pressure control system includes an electronic control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve and connected to an oil passage of the control pressure, a pressure relief port  122  in the pressure switching valve, an input interface  123  located in the pressure switching valve and used for receiving a jointing pressure, a spring chamber or an oil drainage pressure  124  in the pressure switching valve, an output interface  125  located in the pressure switching valve and connected to a control interface of a jointing pressure regulating valve, a valve core  126  in the pressure switching valve, and a spring  127  in the pressure switching valve; and a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve  130  and used for receiving an output of the pressure switching valve, a control interface  132  located in the jointing pressure regulating valve  130  and used for receiving a control pressure, a pressure relief port  133  in the jointing pressure regulating valve  130 , a pressure relief port  134  in the jointing pressure regulating valve  130 , a control interface  135  located in the jointing pressure regulating valve  130  and connected to a system main oil pressure, a jointing pressure feedback interface and a spring chamber  136  in the jointing pressure regulating valve  130 , an output interface  137  located in the jointing pressure regulating valve and used for a jointing pressure of a piston chamber, a spring  138  in the jointing pressure regulating valve  130 , a valve core  139  in the jointing pressure regulating valve  130 , and a small valve core  139   a  in the jointing pressure regulating valve  130 . 
         [0029]    The electronic control device (TCU)  100  outputs a control signal to the control pressure regulating valve  110 , the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a chamber to which a control chamber (i.e. the control interface  121 ) of the pressure switching valve  120  and the control interface  132  of the jointing pressure regulating valve  110  are connected. When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring  127  of the pressure switching valve  120 , the pressure relief port  122  of the pressure switching valve  120  is communicated with a chamber where the output interface  125  is located, and the pressure of an oil drainage chamber enters a control chamber (i.e., the control interface  131 ) of the jointing pressure regulating valve  130  via the pressure relief port  122  and the output interface  125 . The jointing pressure regulating valve  130  outputs a jointing pressure in proportion to the control pressure of the control pressure regulating valve  110 . When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring  127  of the pressure switching valve  120 , the input interface  123  of the pressure switching valve  120  is communicated with the chamber where the output interface  125  is located, the jointing pressure enters the control interface  131  of the jointing pressure regulating valve  130  via the interfaces  123  and  125  and then enters a control chamber of the jointing pressure regulating valve  130 , the valve core  139  of the jointing pressure regulating valve  130  moves rightward, and a system main oil pressure chamber (i.e., the control interface  135 ) is communicated with a piston chamber of a torque control device, i.e., the output interface  137  of the jointing pressure, so that the jointing pressure is equal to the system main oil pressure. 
         [0030]    In Embodiments 1-5 described above, the control pressure regulating valve is generally an electromagnetic valve. The relation between a control pressure and a jointing pressure is shown as  FIG. 1 , and the pressure while the torque control devices are jointed is controlled by a precise control to the control pressure of the electromagnetic valve. In addition, after the torque transmission devices are jointed and when the pressure of the electromagnetic valve exceeds a set valve, a high pressure oil port in the pressure regulating valve is communicated with a piston chamber of the torque control device by means of the pressure switching valve, so as to ensure an adequate torque capacity. 
       Embodiment 6 
       [0031]    In  FIG. 8 , a pressure control system includes an electronic control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve and connected to an oil passage of the control pressure, an input interface  122  located in the pressure switching valve and used for receiving a control pressure, an input interface  123  located in the pressure switching valve and used for receiving a pressure relief chamber, a spring chamber or an oil drainage pressure  124  in the pressure switching valve, an output interface  125  located in the pressure switching valve and connected to a reverse control interface of a jointing pressure regulating valve, a valve core  126  in the pressure switching valve, and a spring  127  in the pressure switching valve; and a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve and connected to the oil passage of the control pressure, a pressure relief port  132  in the jointing pressure regulating valve, a pressure relief port  133  in the jointing pressure regulating valve, a control interface  134  located in the jointing pressure regulating valve and connected to a system main oil pressure, a feedback interface and a spring chamber  135  which are located in the jointing pressure regulating valve and used for receiving a pressure output from the pressure switching valve, an output interface  136  located in the jointing pressure regulating valve and used for a jointing pressure of a piston chamber, a valve core  137  in the jointing pressure regulating valve, and a spring  138  in the jointing pressure regulating valve. 
         [0032]    The electronic control device (TCU)  100  outputs a control signal to the control pressure regulating valve  110 , the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a control chamber (i.e., the control interface  131 ) of the jointing pressure regulating valve  130  and a control chamber (i.e., the input interface  121 ) of the pressure switching valve  120 . When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring  127  of the pressure switching valve  120 , the input interface  122  of the pressure switching valve  120  is communicated with a chamber where the output interface  125  is located, and the control pressure enters a reverse control pressure chamber (i.e., the pressure relief port  132 ) of the jointing pressure regulating valve  130  via the interfaces  122  and  125 . As the control pressure of the control pressure regulating valve  110  is applied in a smaller area, the jointing pressure regulating valve  130  outputs a jointing pressure with a smaller variation rate. When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring  127  of the pressure switching valve  120 , the interface  123  and the interface  125  of the pressure switching valve  120  communicate with each other, and a pressure of the oil drainage chamber enters the reverse control pressure chamber (i.e., the pressure relief port  132 ) of the jointing pressure regulating valve  130  via the interfaces  123  and  125 , so that the control pressure of the control pressure regulating valve  110  is applied in a larger area and the variation rate of the jointing pressure is increased. 
       Embodiment 7 
       [0033]    In  FIG. 9 , a pressure control system includes an electronic control device (TCU)  100  and a control pressure regulating valve  110 , where the control pressure regulating valve  110  is generally an electromagnetic valve; a pressure switching valve  120 , a control interface  121  located in the pressure switching valve and connected to an oil passage of the control pressure, an input interface  122  located in the pressure switching valve and used for receiving a jointing pressure from a jointing pressure control valve, a pressure relief port  123  in the pressure switching valve, a spring chamber or an oil drainage pressure  124  in the pressure switching valve, an output interface  125  located in the pressure switching valve and connected to a feedback interface of a jointing pressure regulating valve, a valve core  126  in the pressure switching valve, and a spring  127  in the pressure switching valve; and a jointing pressure regulating valve  130 , a control interface  131  located in the jointing pressure regulating valve and used for receiving an output of the pressure switching valve, a pressure relief port  132  in the jointing pressure regulating valve, a pressure relief port  133  in the jointing pressure regulating valve, a system main pressure input port  134  in the jointing pressure regulating valve, a feedback interface  135  located in the jointing pressure regulating valve and connected to an output port of the pressure switching valve, a jointing pressure output interface  136  located in the jointing pressure regulating valve and connected to a piston chamber of a torque control device, a valve core  137  in the jointing pressure regulating valve, a spring  138  in the jointing pressure regulating valve, and a jointing pressure feedback interface and a spring chamber  138   a  in the jointing pressure regulating valve  130 . 
         [0034]    The electronic control device (TCU)  100  outputs a control signal to the control pressure regulating valve  110 , the control pressure regulating valve  110  outputs a pressure in proportion to the control signal, and the output pressure of the control pressure regulating valve  110  is applied to a control chamber (i.e., the control interface  121 ) of the pressure switching valve  120  and the control interface  131  of the jointing pressure regulating valve  130 . When the output pressure of the control pressure regulating valve  110  is lower than a set value of the spring  127  of the pressure switching valve  120 , the chambers where the interfaces  122  and  125  of the pressure switching valve  120  are located communicate with each other, and a jointing pressure of the piston chamber enters a feedback chamber (i.e., a chamber to which the feedback interface  135  is connected) of the jointing pressure regulating valve  130  via the interfaces  122  and  125 . As the feedback area of the pressure of the jointing pressure regulating valve  130  is increased, the jointing pressure regulating  130  outputs a jointing pressure with a smaller slope and being in proportion to the control pressure of the control pressure regulating valve  110 . When the output pressure of the control pressure regulating valve  110  is higher than the set valve of the spring of the pressure switching valve  120 , the chambers to which the interfaces  123  and  125  of the pressure switching valve  120  are connected communicate with each other, and an oil drainage chamber enters the feedback interface  135  located in the jointing pressure regulating valve and connected to the output port of the pressure switching valve via the interfaces  123  and  125 , and the feedback interface  135  of the jointing pressure regulating valve  130  releases pressure, so that the feedback area of the jointing pressure regulating valve  130  is reduced, and the jointing pressure regulating valve  130  outputs a jointing pressure with a larger slope and being in proportion to the control pressure of the control pressure regulating valve  110 . 
         [0035]    In Embodiments 6-7 described above, the relation between a control pressure and a jointing pressure is shown as  FIG. 2 . During the torque transmission devices are jointed, by a switching of the pressure switching valve, the apply area of the control pressure of the jointing pressure regulating valve is reduced or the feedback area is increased, it is advantageous for a precise control to the jointing pressure adopting a jointing pressure with a smaller variation slope and being in proportion to the control pressure of the control pressure regulating valve; Furthermore, after the torque transmission devices are jointed, that is, after there is no relative slip, by a switching of the pressure switching valve, the apply area of the control pressure of the jointing pressure regulating valve is increased or the feedback area is reduced, so that the variation slope of the jointing pressure is increased and an adequate torque capacity is ensured.