Abstract:
An actuator device for actuating a coupling mechanism or a transmission in a drive wheel in a belt drive or chain drive, includes a shaft, releasably connectable to the drive wheel and at least partially hollow, a push rod connected to the coupling mechanism or transmission and displaceable coaxially to the longitudinal axis of the shaft, a housing having an internal bore for at least partially receiving the shaft, and at least one first bearing disposed in the internal bore of the housing for rotatably supporting the shaft. The actuator device constitutes a fluidic actuator having at least one first pressure chamber capable of being pressurized with a fluid.

Description:
[0001]    The present invention relates to an actuator device for actuating a coupling mechanism or a transmission in a drive wheel in a chain drive or belt drive, in particular of a controllable coolant pump for an internal combustion engine. 
       BACKGROUND 
       [0002]    Water-cooled engines have become predominant in the field of internal combustion engines. In such engines, cooling water is pumped by a coolant pump in a closed loop through cooling passages in the region of the cylinders in order to cool the internal combustion engine, and is then conveyed to an air/water radiator, where the heated water is cooled down by the relative wind generated by the motion of the vehicle. The pump required to circulate the water is typically connected by a belt drive and/or a chain drive to a pulley of the crankshaft of the internal combustion engine. 
         [0003]    Since the coolant pump is directly coupled to the crankshaft, the rotational speed of the pump is dependent on the rotational speed of the internal combustion engine. As a result, in the high speed range of the internal combustion engine, the pump delivers a correspondingly high flow rate, which exceeds that required for cooling. However, during cold starting of the internal combustion engine, the problem arises that coolant is immediately circulated through the cooling passages, thereby hindering the heating of the combustion chambers and delaying the attainment of an optimum operating temperature. 
         [0004]    A controllable coolant pump of the aforementioned type is known from German Patent Application DE 2008 046 424 A1. In this publication, a guide plate having a contour corresponding to the impeller is disposed between the impeller and a cover plate, the guide plate being guided by the axial webs connecting the impeller and the cover plate, and being axially displaceable by an actuation unit by means of a piston placed within the hollow shaft. By placing a guide plate between the impeller and the cover plate and axially displacing the same by means of a piston guided within the hollow shaft, it is possible to vary the flow rate of the coolant pump. 
         [0005]    The drawback here is that when the drive wheel is driven, the impeller rotates as well, even when cooling of the engine is not yet desired. This is because the drive wheel is connected directly to the crankshaft. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a cost-effective, space-optimized actuator device for actuating a coupling mechanism or a transmission for coupling or uncoupling a drive wheel in a belt drive or chain drive. 
         [0007]    The actuator device for actuating a coupling mechanism or a transmission in a drive wheel in a belt drive or chain drive, in particular of a controllable coolant pump for an internal combustion engine, includes a shaft, having a longitudinal axis, which is releasably connectable to the drive wheel and is at least partially hollow, a push rod which is connected to the coupling mechanism or transmission and is displaceable coaxially to the longitudinal axis of the shaft, a housing having an internal bore for at least partially receiving the shaft, and at least one first bearing disposed in the internal bore of the housing for rotatably supporting the shaft. In accordance with the present invention, the actuator device constitutes a fluidic actuator having at least one first pressure chamber capable of being pressurized with a fluid. 
         [0008]    The controllable coolant pump is drivable via a drive wheel, which can be connected to the shaft at an end opposite the impeller. The impeller can have vanes extending into a suction chamber. Rotation of the impeller allows cooling water to be drawn into the suction chamber through an intake port of the housing of the coolant pump and to be conveyed by the vanes into an annular channel of the pump housing. The guide plate is axially displaceable by a push rod at least partially disposed within the hollow shaft, whereby it is possible to vary the pumping volume of the suction chamber of the coolant pump. The shaft of the actuator device extends along a longitudinal axis and may be completely or partially hollow. Moreover, the shaft can be releasably connected at one end to a drive wheel. The shaft and the drive wheel can be designed to be releasably connectable to each other by a coupling mechanism. The push rod may be disposed within the shaft, partially within the shaft, or substantially outside the shaft in coaxial relationship with the longitudinal axis of the shaft. At the end opposite the drive wheel, the shaft is disposed at least partially within the housing having an internal bore. The internal bore may have at least one first bearing point for receiving a first bearing disposed in the internal bore of the housing for rotatably supporting the shaft. The internal bore may have a second bearing at a second bearing point for rotatably supporting the shaft. The first bearing and the second bearing may be axially spaced apart from each other. The coupling mechanism between the drive wheel and the shaft may, for example, take the form of a draw-key coupling capable of being actuated by the push rod. The draw-key coupling may have a draw key which may be connected to the push rod. The draw key is axially movable along the longitudinal axis of the shaft between a first position and a second position. In the first position, the shaft is connected to the drive wheel, while in the second position, the drive wheel and the shaft are uncoupled. Thus, in the first position, pumping of cooling water is possible, while in the second position, the drive wheel can rotate independently of the shaft, which may be standing still, so that no pumping of cooling water is possible. The drive wheel of the actuator device may, for example, take the form of a pulley in a belt drive or a gear wheel, for example, in a transmission. The shaft may, for example, by a pump shaft of, for example, a coolant pump for an internal combustion engine or a transmission shaft of a transmission. In accordance with the present invention, the actuator device constitutes a fluidic, in particular hydraulic, actuator forming at least one first pressure chamber. The at least one first pressure chamber can be pressurized with a fluid. The pressure applied may be either positive or negative with respect to atmospheric pressure. The actuator device according to the present invention enables actuation of a coupling mechanism or a transmission in a drive wheel in a belt or chain drive, allowing the drive wheel to be uncoupled from the rotating crankshaft wheel, as a result of which the shaft does not rotate, and thus the impeller connected to the shaft also does not rotate. The makes it possible to reduce the power requirements and also enables faster heating of an internal combustion engine during cold starting because no water is pumped through the system by the coolant pump. In particular, by designing the actuator device as a fluidic actuator, it is possible to provide an actuator for actuating a coupling mechanism which is optimized in terms of weight, space, and energy requirements. 
         [0009]    In a preferred embodiment of the present invention, an annular seal and a movable sealing ring axially spaced therefrom are provided in the internal bore, an annular variable first pressure chamber being formed between the seal, the sealing ring, the shaft, and the housing. The annular seal may bear against the first bearing on the inside. The sealing ring, which surrounds the shaft and may bear against the inner wall of internal bore, is axially spaced apart from the annular seal and movable in the axial direction. An annular variable first pressure chamber is formed axially between the annular movable sealing ring and the annular seal and is bounded radially between the shaft and the inner surface of the internal bore of the housing. The pressure chamber extends annularly around the shaft and is variable in the axial direction. The sealing ring can be axially displaced by a fluid entering the first pressure chamber, thereby allowing the first pressure chamber to be enlarged in the axial direction. The sealing ring may be connected to the push rod, which may be provided within the hollow shaft, whereby an axial movement of the sealing ring can be transmitted to the push rod. Thus, the coupling mechanism, in particular the draw-key coupling, can be actuated the push rod. The volume of the pressure chamber can be varied, in particular in the axial direction, as a function of the volume and pressure of the fluid that is introduced into the pressure chamber. Preferably, the push rod, which is at least partially disposed within the shaft, has a transmission element which contacts the sealing ring through at least one opening formed in the shaft. In order to transmit the axial movement of the sealing ring to the push rod, the push rod has a transmission element which contacts the sealing ring through at least one opening formed in the shaft. The transmission element may take the form of a transverse pin. The transverse pin may extend substantially perpendicularly to the longitudinal axis of the push rod and contacts the sealing ring through at least one opening of the shaft, preferably through two openings of the shaft. The transmission element may be permanently or detachably connected to the sealing ring. The at least one opening in the shaft is formed in the wall of the shaft in the region where the shaft is hollow. The opening may be configured as a slotted hole to allow axial movement of the transmission element. The at least one opening may be sealed axially by the sealing ring from the fluid of the pressure chamber, for example by axial overlapping. The transmission element makes it possible to reliably connect the sealing ring to the push rod to transmit motion. 
         [0010]    Particularly preferably, the push rod has a first push rod shoulder at a first end disposed within the shaft, and the shaft has formed therein a first shaft shoulder through which extends the push rod, a first annular variable pressure chamber being formed between the first push rod shoulder, the first shaft shoulder, the push rod, and the shaft. The push rod has a first end disposed within the shaft and a second end which is opposite the first end and may be located on the drive wheel side. The push rod has a first push rod shoulder at the first end. This push rod shoulder may be configured as a circular disk at the end of the push rod, and in such a way that it completely fills the diameter of the bore within the shaft, in particular the hollow shaft. A first shaft shoulder is disposed within the shaft, in particular the hollow shaft, at an axial distance from the first push rod shoulder. The push rod extends, in particular centrally, through the first shaft shoulder. A first pressure chamber is bounded axially between the first push rod shoulder and the first shaft shoulder, and radially by the inner wall of the hollow shaft and the surface of the push rod. The first push rod shoulder, or more specifically, the push rod with the first push rod shoulder, is disposed like a piston within the hollow shaft and can be axially moved like a slide valve. The movement of the push rod can be caused by pressurizing the first pressure chamber with a fluid. The first shaft shoulder may be formed as an annular insert within the at least partially hollow shaft. The annular insert has an opening for extension of the push rod therethrough. By forming the first pressure chamber of the actuator device within a hollow portion of the shaft, the space required for the actuator device can be further reduced. 
         [0011]    In a preferred embodiment, the push rod has a second push rod shoulder, and the shaft has formed therein a second shaft shoulder through which extends the push rod, a second annular variable pressure chamber being formed between the second push rod shoulder, the second shaft shoulder, the push rod, and the shaft. The second push rod shoulder of the push rod may be axially spaced apart from the first push rod shoulder in a direction toward the second end of the push rod. The second push rod shoulder may take the form of an annular disk having a diameter substantially equal to the inner diameter of the hollow portion of the shaft. The second shaft shoulder of the shaft may be located toward the second end of the push rod. The second shaft shoulder may be formed as an annular insert within the hollow shaft and has an opening for extension of the push rod therethrough. A second pressure chamber may be bounded axially between the second push rod shoulder and the second shaft shoulder, and radially by the inner surface of the hollow shaft and the push rod. The second pressure chamber may be formed at an axial distance from the first pressure chamber. The first and second pressure chambers may be designed to act equally or differently, for example through control by means of a 4/2 way valve. By incorporating a second pressure chamber within the hollow shaft of the actuator device, it is possible to produce a greater force for actuating a coupling mechanism within the same space and/or to enable the push rod to move in both axial directions. 
         [0012]    In one embodiment, an actuator housing is provided which is disposed on the side of the drive wheel facing away from the housing and has an opening for at least partially receiving the push rod. The actuator housing, together with the push rod, forms a first pressure chamber therein. The actuator housing may be in the form of a cylinder capable of at least partially receiving the push rod. The push rod may be disposed within the actuator housing in the manner of a piston. The push rod may have a first push rod shoulder within the actuator housing. The actuator housing is disposed on the side of the drive wheel facing away from the housing, and the second end of the push rod may be at least partially received within the actuator housing in the manner of a piston. The push rod, or more specifically, the face of the second end of the push rod, together with the actuator housing, may form a first pressure chamber capable of being pressurized with a fluid, whereby the push rod can be caused to move axially in the manner of a piston, thereby allowing actuation of the coupling mechanism. By disposing the actuator housing on the side of the drive wheel facing away from the housing, the space required for the coolant pump on the housing side can be further reduced. 
         [0013]    Preferably, the actuator housing and/or the shaft has/have at least one first bore allowing fluid passage therethrough for supplying and/or discharging the fluid. The housing and/or the actuator housing has at least one first bore allowing fluid passage therethrough, which bore allows a fluid to be supplied to and/or discharged from a first pressure chamber. The housing and/or the actuator housing may have at least one second bore for supplying and/or discharging a fluid for a second pressure chamber. The first and/or second pressure chambers can be pressurized with a fluid through the first and/or second bores. The fluid can also be discharged from the first and/or second pressure chambers through the first and/or second bores. In particular in the case of a pressure chamber disposed within the shaft, the first and/or second bores may extend through the wall of the hollow shaft. Thus, the first and/or second pressure chambers within the hollow portion of the shaft can be connected to the respective first and/or second bores within the housing. This allows a pressure chamber disposed within the shaft to be pressurized with a fluid. The housing, the actuator housing and/or the shaft may have a drain bore allowing a region that is not pressurized with the fluid to be connected to the environment, for example, to a reservoir. This allows any fluid leakage to be removed from the actuator device, thereby enabling the actuator device to function smoothly. The housing may have a shoulder in the internal bore at least on one side thereof, which shoulder extends radially inwardly toward the shaft and may contact the shaft at its radially outer surface. A bore may extend through the housing, the shoulder, and the shaft, thereby enabling a fluid connection to be established between the housing and a pressure chamber. The shoulder may for example be disposed between the first bearing and the second bearing and extend radially inwardly. 
         [0014]    Particularly preferably, a spring element is provided for actuating the push rod, the spring element being disposed between the push rod and the shaft or the actuator housing. The spring element for actuating the push rod may be a tension or compression spring. The spring element may be disposed between the push rod and the shaft and/or the actuator housing in a manner ensuring that the push rod can be retracted, for example, in response to a decrease in pressure. The spring element may be configured and disposed as a fail-safe device, so that the push rod can be moved to the first position by the spring element in response to a failure in fluid pressure. Thus, in the event of a failure in fluid pressure, it can be ensured that the coupling mechanism will be engaged, and thus, that the coolant will be pumped by the coolant pump. 
         [0015]    The present invention further relates to a coupling mechanism in a drive wheel in a belt drive or chain drive, including an actuator device embodied and refined as described above. By designing the actuator device as a fluidic actuator, it is possible to provide an actuator for actuating a coupling mechanism, which is optimized in terms of weight, space, and energy requirements. 
         [0016]    The present invention also relates to a pump, in particular a coolant pump, for a motor vehicle and/or internal combustion engine, having an actuator device embodied and refined as described above, as well as a coupling mechanism embodied and refined as described above. By designing the actuator device as a fluidic actuator, it is possible to provide a pump, in particular a coolant pump, which is optimized in terms of weight, space, and energy requirements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention will now be illustrated with reference to preferred exemplary embodiments and the accompanying drawings, in which: 
           [0018]      FIG. 1  is a schematic sectional view of an actuator device according to the present invention; 
           [0019]      FIG. 2  is a schematic sectional view of an actuator device having a pressure chamber incorporated in a shaft; 
           [0020]      FIG. 3  is a schematic sectional view of an actuator device having a first and a second pressure chamber; 
           [0021]      FIG. 4  is a schematic sectional view of an actuator housing. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The actuator device  10  shown in  FIG. 1  has a drive wheel  12  which is non-rotatably connectable to a shaft  16  via a coupling mechanism  14 , such as a draw-key coupling. Coupling mechanism  14  is shown in an open condition, a first position, in which drive wheel  12  is rotatable independently of shaft  16 . Shaft  16  is at least partially hollow and closed at both ends. Shaft  16  is rotatably supported in an internal bore  22  of a housing  24  via a first bearing  18  and a second bearing  20  in the form of ball bearings. An annular seal  26  is disposed within the internal bore at first bearing  18 , and a sealing ring  28  is disposed within the internal bore at an axial distance from annular seal  26 . Annular seal  26  and sealing ring  28  are in contact with shaft  16  at their radially inner peripheries and with housing  24  at their radially outer peripheries. A first pressure chamber  30  is bounded axially by annular seal  26  and sealing ring  28 , and radially between shaft  16  and the inner surface of housing  24 . First pressure chamber  30  can be pressurized, e.g., with a fluid, in particular a liquid or a gas, through a first bore  32  formed in housing  24 . Pressurizing first pressure chamber  30  with a fluid can cause sealing ring  28  to move axially, thereby allowing first pressure chamber  30  to be enlarged. The axial movement of sealing ring  28  can be transmitted to a push rod  36  via a transmission element  34  connected to push rod  36 . Push rod  36  is disposed within the at least partially hollow shaft  16 . Push rod  36  is axially movably within shaft  16  in coaxial relationship therewith. Push rod  36  has a first end  38 , which is located on the housing side and connected to transmission element  34 , e.g., a transverse pin. The push rod has a second end  40  opposite its first end  38 . The second end is located on the drive wheel side and has, for example, a draw key  42  of coupling mechanism  14 , which takes the form of a draw-key coupling. Transmission element  34  projects substantially perpendicularly from push rod  36  on opposite first and second sides. Transmission element  34  extends through openings  44  in the wall of hollow shaft  16  and contacts sealing ring  28 . Disposed between first push rod end  38  and shaft  16  is a spring element  46 , e.g., a compression spring, which, in the event of a drop or decrease in pressure, moves push rod  36  axially from a second position, in which coupling mechanism  14  is disengaged, to a first position, whereby coupling mechanism  14  non-rotatably connects shaft  16  to drive wheel  12 . Housing  24  has a drain bore  48  between second bearing  20  and sealing ring  28 , allowing any leakage, in particular leakage of the fluid of first pressure chamber  30 , to be removed therethrough from internal bore  22  and housing  24 . 
         [0023]      FIG. 2  shows an actuator device  10  having a first pressure chamber  30  incorporated in shaft  16 . The push rod  36  disposed within hollow shaft  16  has at its first end  38  a first push rod shoulder  50 . First push rod shoulder  50  is configured as an annular disk-shaped surface at the end face of push rod  36 . First push rod shoulder  50  is supported against shaft  16  via spring element  46 . A first shaft shoulder  52  is formed toward second push rod end  40  within shaft  16 , which is hollow in this region. First shaft shoulder  52  has an opening for receiving push rod  36  and is configured substantially as an annular disk. First pressure chamber  30  is formed between first shaft shoulder  52  and first push rod shoulder  50  and is bounded radially by shaft  16  and push rod  36 . Shaft  16  is rotatably supported within housing  24  in first bearing  18  and second bearing  20 . Housing  24  has a shoulder  54  between first bearing  18  and second bearing  20 . Shoulder  54  extends radially inwardly to shaft  16  and contacts shaft  16 . First bore  32  and drain bore  48  are formed within housing  24  and shoulder  54 . First bore  32  and drain bore  48  extend through shoulder  54  to shaft  16 , where first bore  32  and drain bore  48  are formed correspondingly in the wall of shaft  16 , which is hollow in this region. Pressure chamber  30  can be pressurized with a fluid through first bore  32 , which is formed in housing  24 , or more specifically, in shoulder  54  of housing  24 , and the wall of shaft  16 . First bore  32  serves as an inlet to pressure chamber  30  and as an outlet therefrom for the fluid. Drain bore  48  opens into a region between first push rod shoulder  50  and shaft  16  in the area of spring element  46 , whereby any fluid leakage that may occur from first pressure chamber  30  in the direction of first push rod shoulder  50  can be removed from shaft  16  through drain bore  48 . 
         [0024]      FIG. 3  shows an actuator device  10  similar to the one shown in  FIG. 2 . Actuator device  10  includes shaft  16  and push rod  36 , and is rotatably supported in first bearing  18  and second bearing  20 . Housing  24  has, between first and second bearings  18 ,  20 , a shoulder  54  which extends radially into internal bore  22  and contacts shaft  16  at its radially outer surface. Next to drain bore  48 , actuator device  10  has the first bore  32 , through which a fluid can be supplied into first pressure chamber  30 . First pressure chamber  30  is bounded axially by first push rod shoulder  50  and first shaft shoulder  52 , and radially between shaft  16  and push rod  36 . Push rod  36  has a second push rod shoulder  56  at an axial distance from first push rod shoulder  50 , the second push rod shoulder being configured as an annular disk and axially spaced from first push rod shoulder  50  in a direction toward second end  40  of push rod  36 . 
         [0025]    Shaft  16  has a second shaft shoulder  58  at an axial distance from second push rod shoulder  56 , the second shaft shoulder being axially spaced from second push rod shoulder  56  in a direction toward second push rod end  40 . Second shaft shoulder  58  is configured as an annular disk, which has an opening for extension of push rod  36  therethrough. Second pressure chamber  60  is bounded axially between second push rod shoulder  56  and second shaft shoulder  58 , and radially by shaft  16  and push rod  36 . Second pressure chamber  60  can be pressurized with a fluid through a second bore  62  extending through housing  24 , shoulder  54  of the housing  24 , and the wall of shaft  16 . The pressurization of first pressure chamber  30  and second pressure chamber  60  may be performed uniformly or non-uniformly, for example, alternatingly and oppositely. First pressure chamber  30  and second pressure chamber  60  are formed in succession in the axial direction by shaft shoulders  52 ,  58  and push rod shoulders  50 ,  56 . First pressure chamber  30  and second pressure chamber  60  may be designed to act equally, so that when first pressure chamber  30  and second pressure chamber  60  are pressurized, push rod  36  can move in a direction toward first push rod end  38  and shaft  16 . The push rod can be moved from a first locked position to a second unlocked position of coupling mechanism  14 . Push rod can be moved axially by spring element  46  from the unlocked second position to the locked first position of coupling mechanism  14 . Via drain bore  48 , any leakage from the interior of shaft  16  can be discharged to the outside through housing  24 , in particular via a drain bore  48  in shoulder  54 . 
         [0026]      FIG. 4  shows an actuator device  10  having an actuator housing  64 . Actuator housing  64  is disposed on the side of drive wheel  12  facing away from the housing (not shown). Actuator housing  64  is cylindrical in shape and receives push rod  36  in the manner of a piston. First push rod shoulder  50  of push rod  36  is disposed within actuator housing  64  and is configured as a circular disk. 
         [0027]    First pressure chamber  30  is formed between first push rod shoulder  50  and actuator housing  64 . Pressure chamber  30  can be pressurized with a fluid through first bore  32 . Spring element  46  is formed around push rod  36  between first push rod shoulder  50  and a cover  66  of actuator housing  64 . After pressurization, push rod  36  can be moved by spring element  46  axially, for example, back to the first position. On the drive wheel side, push rod  36  has a draw key  42  disposed within shaft  16 , which is at least partially hollow and in which is disposed a coupling mechanism  14 . Draw key  42  and push rod  36  are shown in the second, unlocked position, in which drive wheel  12  is rotatable independently of shaft  16 . When pressure chamber  30  is pressurized with a fluid through first bore  32 , push rod  36  may be moved axially toward drive wheel  12 , whereby coupling mechanism  14 , or more specifically, draw key  42 , creates a non-rotatable connection between the shaft and drive wheel  12 . In the event of a pressure drop or a negative pressure acting on pressure chamber  30 , push rod  36  may be moved axially by spring element  46  to the second, unlocked position. The movement of push rod  36  to the second, unlocked position may be achieved by applying a negative pressure to pressure chamber  30  through first bore  32 . Actuator housing  64  has a drain bore  48 , which opens into actuator housing  64  in the region of spring element  46  between first push rod shoulder  50  and cover  66 , whereby any fluid leakage can be discharged from actuator housing  64  from this region through drain bore  48 . 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           10  actuator device 
           12  drive wheel 
           14  coupling mechanism 
           16  shaft 
           18  first bearing 
           20  second bearing 
           22  internal bore 
           24  housing 
           26  annular seal 
           28  sealing ring 
           30  first pressure chamber 
           32  first bore 
           34  transmission element 
           36  push rod 
           38  first end 
           40  second end 
           42  draw key 
           44  opening 
           46  spring element 
           48  drain bore 
           50  first push rod shoulder 
           52  first shaft shoulder 
           54  shoulder 
           56  second push rod shoulder 
           58  second shaft shoulder 
           60  second pressure chamber 
           62  second bore 
           64  actuator housing 
           66  cover