Patent Publication Number: US-2013233257-A1

Title: Mechanical coolant pump

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2010/063123, filed on Sep. 7, 2010. The International Application was published in English on Mar. 15, 2012 as WO 2012/031624 A1 under PCT Article 21(2). 
    
    
     FIELD 
     The present invention relates to a mechanical coolant pump for an internal combustion engine. 
     BACKGROUND 
     A mechanical coolant pump is a coolant pump which is driven by a combustion engine itself, for example, by using a driving belt driving a pulley-wheel of the coolant pump. The pulley-wheel drives the rotor shaft or a pump wheel, which is rotatably fixed at the rotor shaft. The rotational speed of such a coolant pump is proportional to the rotational speed of the engine&#39;s crankshaft so that the coolant pump runs permanently even if no coolant flow is needed by the engine. However, this unnecessarily increases the fuel consumption of the combustion engine. Switchable coolant pumps are therefore used to optimize the energy consumption of the system. Particularly for as long as the combustion engine is cold and no coolant flow is needed, the coolant pumps can be switched-off with the result that the combustion engine&#39;s warming-up phase is shortened, exhaust emission decreases, and fuel consumption reduced. 
     A mechanical coolant pump of the prior art which is switchable is described in DE 10 2006 039 680 A1. The coolant pump is provided with an internal mechanical clutch which is arranged inside the pump housing. The mechanical clutch is provided by the pump wheel-sided end of the rotor shaft and the pump wheel so that the rotor shaft can be disengaged from the pump wheel, for example, in the warm-up phase of the combustion engine. The mechanical clutch of such a coolant pump is controlled by a separate external actuator which is connected to the opposite end of the rotor shaft. An external actuator requires additional installation space in the engine compartment. 
     SUMMARY 
     An aspect of the present invention is to provide a compact mechanical coolant pump. 
     In an embodiment, the present invention provides a mechanical coolant pump for an internal combustion engine which includes a pump housing configured to be stationary. The pump housing comprises an internal pneumatic actuator configured to be supplied by a pneumatic supply device. A pump wheel comprises a pump wheel shaft. The pump wheel shaft is configured to be rotatably supported by the pump housing. A driven shaft is directly connected to a pulley-wheel. An internal pneumatic clutch unit comprises a fixed clutch disk attached to the driven shaft or to the pump wheel shaft, and a slidable clutch disk configured to be axially slidably. The slidable clutch disk is arranged at the pump wheel shaft or at the driven shaft and is configured to be rotatably fixed to the pump wheel shaft or to the driven shaft. The internal pneumatic actuator is configured to axially actuate the slidable clutch disk. The driven shaft is connectable to the pump wheel shaft via the internal pneumatic clutch unit]. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
         FIG. 1  shows a cross-sectional view of a mechanical coolant pump. 
     
    
    
     DETAILED DESCRIPTION 
     The mechanical coolant pump for an internal combustion engine according of the present invention comprises a stationary cylindrical pump housing with an internal pneumatic actuator which is supplied by a pneumatic supply means supplying a low-pressure, i.e., a pressure below atmospheric pressure. The pump further comprises a pump wheel rotatably fixed with a pump wheel shaft, whereby the pump wheel shaft is rotatably supported by the pump housing. The pump wheel shaft is connectable to a separate driven shaft by an internal pneumatic clutch unit, whereby the driven shaft is directly connected with a pulley-wheel which is driven by a driving belt. The internal clutch unit comprises a clutch disk which is completely fixed to the driven shaft or, alternatively, to the pump wheel shaft, and an axially slidable clutch disk which is slidably arranged at the pump wheel shaft or, alternatively, at the driven shaft. The slidable clutch disk is rotatably fixed to the pump wheel shaft or, alternatively, to the driven shaft and is axially actuated by the pneumatic actuator. 
     The internal pneumatic actuator uses a low-pressure to actuate the clutch unit, more specifically, to actuate the slidable clutch disk. The low-pressure is supplied by the pneumatic supply means, more specifically, by the intake section of the combustion engine so that the coolant pump does not need an external actuator. This minimizes the size of such a switchable coolant pump so that the required installation space is minimized in comparison to a switchable coolant pump with a separate external actuator. 
     In an embodiment of the present invention, the pump wheel shaft or, alternatively, the driven shaft can, for example, be provided with a longitudinal slide-bar at the clutch-sided end of the shaft. This end is defined by a reduced cross-section compared to the other part of the shaft. The slidable clutch disk is rotatably fixed by the slide-bar and slidably arranged at the slide-bar. The axial movement of the slidable clutch disk into the disengaged position is limited at the opposite end by a radial stopping face, for example, by a circular step in the shaft. 
     In an embodiment of the present invention, the slidable clutch disk can, for example, be pretensioned into the engaged position by a pretensioning element, whereby the pretensioning element can, for example, be a compression spring. The pretension element can, for example, be supported by the shaft, for example, by a spring supporting plate which is fixed to the shaft. The spring supporting plate is a mechanical support of the pretensioning element. The pretensioning into the engaged position makes the pump fail-safe so that the operation or the cooling of the engine, respectively, is provided even if the actuator fails. The clutch can be disengaged when needed, for example, during the warm-up phase of the engine by the pneumatic actuator which is supplied by the pneumatic supply means. The pneumatic supply means comprises an intake section which supplies the low-pressure, a pneumatic valve, and a pneumatic control unit which controls the pneumatic valve. 
     In an embodiment of the present invention, the internal pneumatic actuator can, for example, be defined by the slidable clutch disk and the pump housing. The clutch disk is an integral part of the pneumatic actuator. 
     In an embodiment of the present invention, the pump housing can, for example, be provided with a pneumatic opening provided axially between the slidable clutch disk and the pump wheel or, alternatively, the pulley-wheel. The pneumatic opening is connected to the pneumatic supply means. The slidable clutch disk can be disengaged from the fixed clutch disk by using the internal pneumatic actuator which is supplied by the pneumatic supply means. The pneumatic actuator therefore acts against the force of the pretensioning element or the force of the compression spring, respectively. 
     In an embodiment of the present invention, the circumference of the slidable clutch disk can, for example, be provided with a ring-like sealing element which seals the circular gap between the slidable clutch disk and the inner side wall of the circular pump housing. The sealing element provides an air-tight internal pneumatic actuator so that the slidable clutch disk can be disengaged from the fixed clutch disk by the pneumatic actuator or the low-pressure, respectively. The sealing element can be, for example, be a lip seal or a Teflon-element. 
     In an embodiment of the present invention, the gap between the slidable clutch disk and the pump wheel shaft or, alternatively, the driven shaft can, for example, be provided with a shaft sealing so that the gap is closed gas-tight. The pneumatic actuator supplied with the low-pressure is therefore able to disengage the slidable clutch disk from the fixed clutch disk by using the pneumatic supply means. 
       FIG. 1  shows a mechanical coolant pump  10  for providing a coolant to an internal combustion engine. The mechanical coolant pump  10  comprises a stationary circular pump housing  12  with an internal pneumatic actuator  13 , a pump wheel  18  with a pump wheel shaft  20 , and a separate driven shaft  22  connected directly with a pulley wheel  24 . 
     The shafts  20 ,  22  are rotatably supported at each axial end of the shafts  20 ,  22  by a ball bearing  40 ,  41  and a friction bearing  32 ,  33 , respectively. The pump wheel shaft friction bearing  32  is a sealing arrangement sealing an internal pneumatic actuator  13  against the ambient pressure. 
     The driven shaft  22  is connectable to the pump wheel shaft  20  via an internal pneumatic clutch unit  11 , which is positioned inside the pump housing  12 . The clutch unit  11  comprises a fixed clutch disk  26  which is attached completely fixed to the driven shaft  22  and an axially slidable clutch disk  28  which is arranged at the clutch-sided end of the pump wheel shaft  20  and which is axially actuated by the internal pneumatic actuator  13 . 
     The clutch-sided end of the pump wheel shaft  20  provides a reduced cross-section diameter compared to the main portion of the pump wheel shaft  20 , and is provided with a longitudinal slide-bar  34  on which the slidable clutch disk  28  is axially slidable and rotatably fixed. The gap between the slidable clutch disk  28  and the pump wheel shaft  20  or the longitudinal slide-bar  34 , respectively, is closed by a shaft sealing  17  so that the gap is closed gas-tight. The axial movement of the slidable clutch disk  28  into the disengaged position is limited at the opposite end of the pump wheel shaft  20  by a radial stopping face  44 , for example, by a circular step in the shaft. 
     The slidable clutch disk  28  is pretensioned into the engaged position by a pretensioning element  36 , whereby the pretensioning element  36  is a single compression spring which is positioned around the pump wheel shaft  20 . The compression spring  36  acts with a constant pressure on the thrust face  27  of the slidable clutch disk  28  so that no tilting moment is generated and jamming of the slidable clutch disk  28  with the inner side wall  30  of the pump housing  12  can be effectively avoided. The pretensioning element  36  is supported by the pump wheel shaft  20  via a spring supporting plate  42  which is completely fixed to the pump wheel shaft  20 . 
     The circumference of the slidable clutch disk  28  is provided with a ring-like sealing element  38 . The sealing element  38  seals the circular gap between the inner side wall  30  of the circular pump housing  12  and the slidable clutch disk  28 . 
     The internal pneumatic actuator  13  is defined by the slidable clutch disk  28  and the circular pump housing  12 . The internal pneumatic actuator  13  is arranged inside the pump housing  12 . The pump housing  12  is provided with a pneumatic opening  16  which connects the internal pneumatic actuator  13  with a pneumatic supply means  15 . The pneumatic supply means  15  comprises an intake section  45  which supplies the low-pressure, a pneumatic valve  19  and a pneumatic control unit  21  which controls the pneumatic valve  19 . The pneumatic opening  16  is axially positioned between the pump wheel  18  and the slidable clutch disk  28  so that the slidable clutch disk  28  can be disengaged by the internal pneumatic actuator  13  when needed, for example, during the warm-up phase of the cold combustion engine. 
     The mechanical coolant pump  10  can be mounted directly to the engine block by a flange  48 . 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims.