Abstract:
A friction gear for a separate accessory of a combustion engine equipped with belt-driven auxiliary units, including a frictional wheel guided by a swivel arm coupled to the engine, to which a protection device is assigned, with the swivel arm and the frictional wheel/protection device provided as a single assembly. The swivel arm provided in the form of a hollow profile includes, on the one hand, a housing which has a single part, flat-cylindrical design and which serves as an essentially closed frictional wheel/protection device with a frictional wheel that can be rotationally mounted between housing end walls and, on the other hand, a coupling location, such that the swivel arm forming a whole with the protective housing and with the coupling location is designed so that it can be assembled over at least one longitudinal partition.

Description:
[0001]     This application is a continuation application of International application PCT/EP2004/010108 filed Sep. 10, 2004 and claims the priority of German application No. 103 46 425.5, filed Oct. 7, 2003, the disclosure of which are expressly incorporated by reference herein. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     The invention relates to a friction gear for a separate accessory unit in an internal combustion engine equipped with belt-driven auxiliary units, comprising a friction wheel in continuous or controlled drive connection with a drive wheel for the accessory unit, and a belt for a belt drive of the internal combustion engine which the friction wheel contacts or may be brought into contact therewith, whereby the friction wheel, which is held or controllable in/out of the drive connection via a swivel arm coupled on the engine side by means of a control device, is provided with a protective device which is connected to the swivel arm in parts.  
         [0003]     Such a friction gear has been proposed in the unpublished German patent application 103 30 672, wherein the swivel arm shown in  FIGS. 2 and 3  is designed as shown in the perspective view in  FIG. 4  of another German patent application 103 09 061, namely, as a swivel arm having a bearing eye on which two guide levers which support the friction wheel are positioned. As shown in  FIG. 2  of the above-cited P 103 30 672, a cover is associated with the guide lever farthest from the engine and is connected as a single piece to the protective housing covering the friction wheel on one side.  
         [0004]     An object of the invention is to refine the swivel arm and friction wheel/protective device to produce a single component that has a simple design and is economically manufactured.  
         [0005]     This object is achieved by a swivel arm in the form of a hollow profile which comprises, on the one hand, a housing with a one-piece, integrally molded flat-cylindrical design which serves as an essentially closed friction wheel/protective device having a friction wheel that can be rotationally mounted between housing end walls and, on the other hand, comprises a one-piece, integrally molded coupling point, whereby the swivel arm, which together with the protective housing and the coupling point forms a single unit, is designed so that it can be assembled over at least one longitudinal partition.  
         [0006]     The invention advantageously results in a single component having a simple design.  
         [0007]     A structure which contributes to the simple design also with respect to high rigidity is achieved in that the protective housing is connected to the coupling point, designed as a bearing eye, via a single arm element of the swivel arm having a hollow profile with a box-shaped, edgewise cross section. Compared to two arm elements, for example, a single arm element provides a flat, compact design.  
         [0008]     For a design which produces a favorable power flux in the single arm element, it is further provided that the bearing eye, having a relatively thick bearing wall, is joined as a single piece to the top sides of the hollow profile of the arm element by adapted transitions, and the hollow profile is closed off on the eye side by a circumferentially closed bearing wall, thereby advantageously increasing the torsional rigidity of the arm element in the region of connection to the bearing eye.  
         [0009]     Cooperation of the arm element and the protective housing which is advantageous with respect to rigidity is further achieved by the fact that the side boundaries supplementing the top sides of the hollow profile are flush with the end faces of the protective housing, and the top sides of the hollow profile also form rounded transitions to the outer periphery of the protective housing, whereby contact openings for the friction wheel are situated in the housing-side connection regions of the transitions, adjacent to the outer periphery of the housing, with the belt and the accessory unit/drive wheel.  
         [0010]     An advantageously rigid protective housing is achieved by a further embodiment of the invention by the fact that recesses coaxial with the friction wheel axis are molded into the end faces of the protective housing, and have spacer rings associated with the interior of the housing which by a threaded connection are braced against an inner bearing ring of the friction wheel. The recesses preferably have the shape of a truncated cone, and are indented in such a way that the threaded connection at either end does not project beyond the end faces of the housing, thus advantageously providing an essentially smooth-surface design of the protective housing.  
         [0011]     To achieve proper operation of the friction wheel, according to the previously mentioned German patent application 103 30 672 the protective housing is also designed such that a shearing device which keeps the inlet gap between the friction wheel and the belt substantially free of spun-off particles and liquid droplets is associated with the belt-side contact opening on the outer periphery of the protective housing. In this manner, in particular a liquid film which interferes with the respective friction-fit drive connection during operation of the friction wheel is significantly reduced.  
         [0012]     This objective is also achieved by the further feature of the embodiment, according to which the protective housing at a distance from the belt-side contact opening has a radially outwardly situated circumferential section on the outer periphery, in the opposite rotational direction of the friction wheel, which is provided with shear walls oriented in the rotational direction of the friction wheel and at a mutual distance from one another, whereby each of the two end faces of the protective housing is provided with discharge openings between the shear walls for liquid spun off from the rotating friction wheel.  
         [0013]     For an advantageously simple production with a simultaneously advantageous highly stress-resistant swivel arm designed as a single unit according to the invention, the swivel arm is formed by a longitudinal partition composed of two essentially half-shells which are detachably or nondetachably connected to one another. As detachable connections, preferably locking connections are considered in which the material selected for the swivel arm has sufficient elasticity, whereby the threaded connection serving as the friction wheel axis provides protection for the particular locking connection.  
         [0014]     Integral connections such as welding or soldering may be considered as nondetachable connections, depending on the material selected for the swivel arm, and in addition the swivel arm half-shells may be adhesively bonded together.  
         [0015]     With regard to an advantageously simple production with the additional advantage of easily applied reinforcements for increased rigidity, the swivel arm shells in approximate halves are each formed as injection-molded parts from a light metal or a fiber-reinforced plastic, and in particular for increasing the rigidity are integrally connected to one another following prior assembly of the friction wheel,  
         [0016]     According to the proposal of a hollow profile design of the swivel arm closed off on the protective housing side, a cavity is provided in the arm element of the swivel arm for accommodating one or more separate devices, such as control electronics, a drive element, or a damping or quenching element for the swivel arm according to the invention.  
         [0017]     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings for example. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  shows a strictly sectional view of a belt drive having a friction gear for a separate accessory unit in accordance with an embodiment of the present invention, together with a friction wheel disengaged according to the first illustration in the above-cited P 103 30 672.  
         [0019]      FIG. 2  shows an exploded view of a swivel arm according to an embodiment of the invention designed as a single unit, composed of half-shells. 
     
    
     DETAILED DESCRIPTION  
       [0020]     To facilitate association of the subject matter of the application,  FIG. 1  shows an illustration of a belt drive  1  for an internal combustion engine  2 , shown in a strictly sectional view, reproduced-according to P 103 30 672, comprising a friction gear  3 ′ for an accessory unit  4  which is provided separately on the internal combustion engine  2  and which preferably is a coolant pump for the cooling circuit of the internal combustion engine  2 .  
         [0021]     According to  FIG. 1  of P 103 30 672, the friction gear  3 ′ shown without regard to the subject matter of the application comprises a friction wheel  3  in continuous or controlled drive connection with a drive wheel  5  for the accessory unit  4 , and a belt  6  for the belt drive  1  of the internal combustion engine  2  which the friction wheel  3  contacts or may be brought into contact therewith. The friction wheel  3 , which is held or controllable in/out of the drive connection via a fork-shaped swivel arm  7 ′ coupled to the engine by means of a control device  9  (not shown) which is situated in the coupling point  8  and comprises a torsion spring-loaded eccentric cam, is provided with a protective device according to  FIG. 2  of the above-cited P 103 30 672.  
         [0022]     In order to refine the swivel arm and friction wheel/protective device to produce a single component that has a simple design and is economically manufactured according to the object of the invention, a swivel arm  7  in the form of a hollow profile  10  comprises, on the one hand, a housing  11  with a one-piece, integrally molded flat-cylindrical design which serves as an essentially closed friction wheel/protective device  12  having a friction wheel  3  that can be rotationally mounted between housing end walls  13  and, on the other hand, comprises a one-piece, integrally molded coupling point  8 , whereby the swivel arm  7 , which together with the protective housing  11  and the coupling point  8  forms a single unit, is designed so that it can be assembled over at least one longitudinal partition.  
         [0023]     As shown in  FIG. 2 , the protective housing  11  is connected via a single arm element  7 ″ of the swivel arm  7  to the coupling point  8  designed as a bearing eye  14 , whereby the arm element  7 ″ has a hollow profile  10  with a box-shaped, edgewise cross section for achieving a rigid swivel arm  7 .  
         [0024]     As a further measure for achieving a rigid swivel arm  7 , the bearing eye  14  having a relatively thick bearing wall  14 ′ is joined as a single piece to the top sides  16  of the hollow profile  10  by adapted transitions  15 , and the hollow profile  10  is closed off on the bearing eye side via a circumferentially closed bearing wall  14 ′. This design achieves a torsionally rigid connection of the arm element  7 ″ to the bearing eye  14 .  
         [0025]     To advantageously transmit in particular tensile stresses from the arm element  7 ″ into the protective housing  11 , the side boundaries  17  supplementing the top sides  16  of the hollow profile  10  are flush with the end faces  13  of the protective housing  11 . In addition, the top sides  16  form rounded transitions  18  to the outer periphery  19  of the protective housing  11 , whereby contact openings  20 ,  20 ′ for the friction wheel  3  are situated in the housing-side connection regions of the transitions  18 , adjacent to the outer periphery  19  of the housing, for friction-fit contact with the belt  6  and the drive wheel  5 .  
         [0026]     To reinforce the protective housing  11 , recesses  22  coaxial with the friction wheel axis  21  are molded into the end faces  13  of the protective housing, and have spacer rings  23  associated with the interior of the housing which by means of a threaded connection  24  are braced against an inner bearing ring  25  of the friction wheel  3 .  
         [0027]     To ensure a proper friction-fit drive connection of the friction wheel  3  when the belt  6  is loaded with water, a shearing device  26  which keeps the inlet gap between the friction wheel  3  and the belt  6  substantially free of spun-off water droplets is associated with the belt-side contact opening  20  on the outer periphery  19  of the protective housing  11 . In order to essentially keep the additional water, which is nevertheless entrained by the friction wheel  3  at the outer periphery, from the inlet gap, the protective housing  11  at a distance from the belt-side contact opening  20  has a radially outwardly situated circumferential section  19 ′ on the outer periphery  19 , in the opposite rotational direction of the friction wheel, which is provided with shear walls  27  oriented in the rotational direction of the friction wheel  3  and at a mutual distance from one another. Each of the two end faces  13  of the protective housing  11  is provided with discharge openings  28  between the shear walls  27  for discharging water spun off from the friction wheel  3  against the shear walls  27 .  
         [0028]     A structure of the swivel arm  7  which contributes to a simple design and economical manufacture and forms a single unit with the coupling point  8  and the protective housing  11  is achieved by an advantageous longitudinal partition which preferably divides the swivel arm  7  into two half-shells  70 ,  70 ′. The design thereof may be selected so that the shells  70 ,  70 ′ are provided for a detachable or nondetachable connection.  
         [0029]     The manufacture of the swivel arm  7  in a one-piece design according to the invention from two approximate half-shells  70 ,  70 ′ allows their advantageous production as injection molded parts made of a relatively low-weight material such as a light metal, for example, or a fiber-reinforced plastic. Within the scope of the invention, the shells  70 ,  70 ′ may also be produced as pressed sheet metal parts. Furthermore, within the scope of the invention, instead of two half-shells  70 ,  70 ′ only a single shell (not shown) may be provided, the open side of which is closed by a cover.  
         [0030]     To achieve a rigid swivel arm  7 , the half-shells  70 ,  70 ′ forming same are integrally connected to one another.  
         [0031]     By means of an additional hollow profile  10  (not illustrated) closed off on the protective housing side, the swivel arm  7  according to the invention is provided with a cavity  29  which may be used for accommodating one or more devices such as a damping or quenching element for the swivel arm  7 .  
         [0032]     By use of the bearing eye  14 , the swivel arm  7  may cooperate with an eccentric cam mounted so as to be rotatable about an axis stationary with respect to the engine, whereby via the swivel arm  7  the eccentric cam, driven by means of a pretensioned torsion spring, maintains the friction wheel  3  in a permanent drive connection with the drive wheel  5  of the accessory unit  4  and the belt  6  of the belt drive  1  for the internal combustion engine  2  according to the subject matter of the application P 102 55 074.  
         [0033]     The automatic adjustability of the friction wheel  3  provided by the eccentric cam may be offset in a targeted fashion by a servomotor driven in a controlled manner on the eccentric cam against the effect of the torsion spring for achieving a desired interruption of the previously described drive connection, primarily during, and in a time-limited manner, after, the cold start of a liquid-cooled internal combustion engine  2  to reduce the starting power, and for warming up the internal combustion engine  2  more rapidly by the lack of coolant circulation resulting from the stopped coolant pump acting as accessory unit  4 .  
         [0034]     Thus, for such a servomotor, P 103 09 063, for example, has proposed an electric stepping motor which is in drive connection with the eccentric cam by means of a gear that is rotatable in both rotational directions without self-locking. A free-wheel device which is rotationally blocked only in the drive direction is provided between this servomotor and the gear in a drive connection in order to achieve a fail-safe function.  
         [0035]     In another proposed design of a servomotor, the rotational motion of the eccentric cam is achieved by a lifting motion of the eccentric cam along a steep thread guide. According to the subject matter of P 102 55 075, the lifting motion of the eccentric cam is controlled by an electromagnet. In contrast, according to the subject matter of application P 103 09 061 the lifting motion is achieved by inserting a membrane pressurized by a pneumatic or hydraulic pressure medium.  
         [0036]     The German patent application 102 55 073 illustrates and describes a further design of a servomotor, according to which an eccentric cam is designed as a hydraulically impingeable rotary piston.  
         [0037]     Lastly, the friction wheel  3  according to P 103 09 062 is provided on the outer periphery with a contact surface made of liquid-repellent rubber, plastic, or elastomer, the contact surface being provided with drainage channels  30  for reducing a liquid deposit. Furthermore, the contact surface of the friction wheel  3  may have a convex design to prevent the friction wheel  3  from running over one of the edges of one of its friction partners as a result of dimensional and production deviations, which could advantageously cause increased weal.  
         [0038]     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.