Abstract:
A clutch control device for controlling the operation of a hydraulically operated clutch with a flow control valve. The control device includes a volume flow regulating valve that enables both volume flow regulated filling and volume flow regulated emptying of a hydraulic clutch positioning element, to provide rapid and precise operation of the clutch.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of International Application Serial No. PCT/DE2007/00029, having an international filing date of Feb. 15, 2007, and designating the United States, the entire contents of which is hereby incorporated by reference to the same extent as if fully rewritten. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a clutch control device for controlling the operation of a hydraulically operated clutch with a valve. The present invention also relates to a clutch, in particular a wet clutch, having a clutch control Furthermore, the present invention relates to a power train including an engine and a transmission, in particular an automatic shift transmission, a dual clutch transmission, or a CVT transmission. 
         [0003]    Distance-regulated or pressure-regulated valves can be used, for example, to operate a clutch by means of a hydraulic system. 
         [0004]    An object of the present invention is to provide a clutch control device for controlling the operation of a hydraulically actuated clutch with a valve that enables rapid and precise actuation of the clutch. 
       SUMMARY OF THE INVENTION 
       [0005]    The object is achieved with a clutch control device for controlling the operation of a hydraulically actuated clutch with a valve. The valve includes a volume flow regulating valve that enables both volume flow regulated filling and volume flow regulated emptying of a hydraulic clutch positioning element. The volume flow regulating valve makes it possible to control the clutch independently of the clutch force characteristic curve. 
         [0006]    A preferred exemplary embodiment of the clutch control device is characterized in that the volume flow regulating valve includes a valve body that is movable between a filling position, in which a filling volumetric flow from a source of hydraulic medium to the clutch positioning element is released, and an emptying position in which an emptying volumetric flow from the clutch positioning element to a hydraulic medium sink is released. The valve body is preferably a valve spool that is guided so that it is movable back and forth within a valve housing, and that has control edges that release flow cross sections of different sizes in the filling or emptying direction, depending upon the position of the valve spool. 
         [0007]    Another preferred exemplary embodiment of the clutch control device is characterized in that the volume flow regulating valve has, between the filling position and the emptying position, a closed position for the valve body, at which both volume flows are interrupted. That prevents a short circuit between the hydraulic medium source and the hydraulic medium sink when switching back and forth between the filling position and the emptying position. 
         [0008]    Another preferred exemplary embodiment of the clutch control device is characterized in that the valve spool is biased into its emptying position by a spring that acts on one end of the valve spool. The spool is movable to its filling position by a proportional magnet that acts on the other end of the valve spool. The spring is preferably a compression spring. The proportional magnet is preferably designed so that it applies a pressure force to the valve spool when it is energized. However, other springs or proportional magnets can also be used within the scope of the present invention. 
         [0009]    Another preferred exemplary embodiment of the clutch control device is characterized in that an orifice plate is positioned between the volume flow regulating valve and the hydraulic clutch positioning element. The pressure upstream of the orifice plate, viewed in the filling direction of the clutch positioning element, is fed back to one end of the valve spool, in particular to the end of the valve spool against which the spring acts. The pressure downstream from the orifice plate, as viewed in the filling direction of the clutch positioning element, is fed back to the other end of the valve spool, in particular to the end of the valve spool against which the proportional magnet acts. The pressure fed back causes an additional force to act on the valve spool when the clutch positioning element is being filled, the magnitude of which depends upon the volume flow rate. When the volume flow rate increases, the valve spool is returned to its emptying position by the increasing pressure differential at the orifice plate, which supports the effect of the spring force. The volume flow rate and the pressure differential are reversed when the clutch positioning element is being emptied, so that the pressure differential that occurs at the orifice plate acts in the opposite direction from when the clutch positioning element is being filled. 
         [0010]    Another preferred exemplary embodiment of the clutch control device is characterized in that a filling orifice plate is inserted between the hydraulic medium source and the volume flow regulating valve, with the pressure being fed back to one end upstream of the filling orifice plate, as viewed in the filling direction of the clutch positioning element, in particular to the end of the valve spool against which the spring acts, and in that the pressure is fed back to the other end downstream from the filling orifice plate, as viewed in the filling direction of the clutch positioning element, in particular to the end of the valve spool against which the proportional magnet acts. In the exemplary embodiment described in the preceding paragraph the pressure differential at the orifice plate also causes a lower pressure at the clutch. Hence, at high clutch pressures the adjustment can only occur more slowly. If one uses a larger orifice plate in order to reduce that effect, then under some circumstances an infinitesimally small pressure differential occurs at low volume flow rates. 
         [0011]    The orifice plate must also be designed appropriately for emptying the clutch or the clutch positioning element. It is preferable here to reduce the controllability rather than to forego high volume flows, since the clutch must in any case be released very quickly in emergencies. Furthermore, the residual pressure in the clutch acts as a pressure accumulator in that functional direction. If the clutch or the clutch positioning element is almost empty, then it is no longer possible to build up a great pressure differential. Hence, the orifice plate must be large enough so that the clutch can be completely disengaged at high speed. To fulfill those different requirements for the orifice plate, the orifice plate in the form of the described filling or supply orifice plate can be placed ahead of the volume flow regulating valve, i.e., in the supply conduit. 
         [0012]    Another preferred exemplary embodiment of the clutch control device is characterized in that an emptying orifice plate is positioned between the volume flow regulating valve and the hydraulic medium sink, with the pressure being fed back to one end upstream of the emptying orifice plate, as viewed in the emptying direction of the clutch positioning element, in particular to the end of the valve spool against which the proportional magnet acts. Since a separate orifice plate is present for each of the two flow-through directions, they can ideally be matched to the respective needs. Since the decisive factor for regulating with this valve system is only the pressure differential, not the absolute pressure in the system, it operates independently of the system pressure. 
         [0013]    Another preferred exemplary embodiment of the clutch control device is characterized in that the volume flow regulating valve is a spring-biased 3/3 directional proportional solenoid valve. That design has proven to be especially advantageous compared to conventional directional valves. 
         [0014]    The invention also relates to a clutch, in particular a wet clutch, having a clutch control device as described herein. 
         [0015]    In a power train, in particular that of a motor vehicle having an engine and a transmission, in particular an automatic shift transmission, a dual clutch transmission, or a CVT transmission, the object stated earlier is achieved by the fact that a clutch as described earlier is positioned between the engine and the transmission, in particular as a startup clutch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Additional advantages, features, and details of the invention derive from the following description, in which various exemplary embodiments of the present invention are described in detail with reference to the drawing. The drawing figures show the following: 
           [0017]      FIG. 1 : a hydraulic circuit diagram of a clutch control device in accordance with a first exemplary embodiment of the present invention, having an orifice plate, and 
           [0018]      FIG. 2 : a hydraulic circuit diagram of a clutch control device in accordance with a second exemplary embodiment of the present invention, having a filling orifice plate and an emptying orifice plate. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]      FIG. 1  shows a hydraulic circuit diagram for a clutch control device  1 . A hydraulic medium source  2  is indicated only by a rectangle. The hydraulic medium source  2  is, for example, a hydraulic oil tank, a hydraulic oil pump, and/or a hydraulic oil pressure tank. The hydraulic medium source transports hydraulic medium, in particular hydraulic oil, into a hydraulic line, which is indicated by an arrow  3 . A hydraulic medium sink is designated by  4 . The hydraulic medium sink  4  is, for example, a hydraulic oil tank. An additional hydraulic line, which is indicated by an arrow  5 , leads into the hydraulic medium sink  4 . 
         [0020]    Hydraulic lines  3  and  5  are connected to 3/3 directional proportional solenoid valve  8 , which is also referred to as a volume flow regulating valve. Volume flow regulating valve  8  includes a valve housing, within which a valve body  9  is guided so that it can move back and forth. Valve body  9 , which is also referred to as a valve spool, is movable among three different positions F, S, and E. A proportional magnet  10  acts on one end  11  of valve spool  9 . A compression spring  12  acts on the other end  13  of valve spool  9 . Valve spool  9  is biased by compression spring  12  to the position E shown in  FIG. 1 . When proportional magnet  10  is energized, valve spool  9  shifts to the right in  FIG. 1 , against the biasing force of compression spring  12 , i.e., toward compression spring  12 . 
         [0021]    An additional hydraulic line is connected to volume flow regulating valve  8 , as indicated by an arrow  14 . The additional hydraulic line  14  connects volume flow regulating valve  8  to a clutch positioning element  16 . Clutch positioning element  16  is, for example, a piston and cylinder unit, by which a clutch (not shown) is hydraulically actuated. An orifice plate  20  is positioned between volume flow regulating valve  8  and clutch positioning element  16 . The direction of arrows  3  and  14  indicates the flow direction of the hydraulic medium when clutch positioning element  16  is being filled. A dashed line  23  indicates a pressure feedback line through which the pressure in hydraulic line  14 , when viewed in the filling direction upstream of orifice plate  20 , and thus away from the hydraulic medium pressure source  2 , is returned to the end  13  of valve spool  9 . An additional dashed line  25  indicates another pressure feedback line, through which the pressure downstream of orifice plate  20  is returned to the end  11  of valve spool  9 . 
         [0022]    Valve  8  is biased into the illustrated position E by compression spring  12 . When proportional magnet  10  is energized, then valve  8  opens, which means that valve body  9  is moved to position F. In position F a volumetric flow of hydraulic fluid is released from hydraulic source  2  to clutch positioning element  16 . At the same time a pressure differential builds up at orifice plate  20 , whereby the higher pressure upstream of orifice plate  20  is returned to end  13  of valve spool  9 . The lower pressure downstream from orifice plate  20  is returned to end  11  of valve spool  9 . To set a certain volumetric flow from hydraulic source  2  into clutch positioning element  16 , proportional magnet  10  must be set to a defined magnetic field strength. A rising volumetric flow brings about a higher pressure differential at orifice plate  20 . The pressure differential returned through pressure return lines  23  and  25  to valve spool  9  ensures that valve spool  9  is moved far enough toward compression spring  12  so that the desired volumetric flow is restored. 
         [0023]    If clutch positioning element  16  is to be emptied of hydraulic fluid, then the volumetric flow direction is reversed, and is also the pressure differential at orifice plate  20 . However, when hydraulic fluid from clutch positioning element  16  is emptied into tank  2 , the corresponding control edges of valve  8  are also reversed. Thus, the orifice plate  20 , through which there is a backward flow when emptying the clutch positioning element, has a supportive effect on the magnetic force provided by proportional magnet  10 . Hence in this flow direction as well, the pressure differential at orifice plate  20  acts on the relevant control edge of valve  8 . Accordingly, volume flow regulating valve  8  can be used to set a defined volumetric flow both when filling and when emptying clutch positioning element  16 . 
         [0024]      FIG. 2  shows a similar hydraulic circuit diagram as in  FIG. 1 . The same reference numerals are used to designate like parts. To avoid repetition, reference is made to the earlier description of  FIG. 1 . The next section will primarily examine the differences between the two exemplary embodiments. 
         [0025]      FIG. 2  shows a clutch control device  41  in which the hydraulic line  3  between hydraulic source  2  and volume flow regulating valve  8  is provided with an inlet orifice  50 . A dashed line  52  indicates that the pressure downstream of inlet orifice  50  is fed back to end  11  of valve spool  9 . Another dashed line  51  indicates that the pressure upstream of inlet orifice  50  is fed back to end  13  of valve spool  9 . 
         [0026]    Furthermore, in the exemplary embodiment shown in  FIG. 2  the hydraulic line  5  between volume flow regulating valve  8  and hydraulic sink  4  is provided with an emptying orifice plate  60 . An additional dashed line  61  indicates another pressure feedback line, through which the pressure upstream of emptying orifice plate  60  is fed back to the end  11  of valve spool  9 . 
         [0027]    Since in the exemplary embodiment shown in  FIG. 2  a separate orifice plate  50 ,  60  is provided for each of the different flow directions through valve  8 , orifice plates  50 ,  60  can be matched ideally to the particular needs. When clutch positioning element  16  is being filled, the volumetric flow in the direction of arrow  3  causes a pressure differential at filling orifice plate  50 , also referred to as the inlet orifice, which is fed back to both ends  11 ,  13  of valve spool  9 . If clutch positioning element  16  is to be emptied, then the system pressure of hydraulic source  2  is present at both sides of filling orifice plate  50 . The forces acting on valve spool  9  through pressure feedback lines  51 ,  52  cancel each other out. Emptying orifice plate  60  causes a back pressure, which is fed back via pressure return line  61  to end  11  of valve spool  9 , and thus enables regulation of the volumetric flow rate.