Abstract:
A driven accessory that includes an input member, a cover, an output member, a clutch and a clutch actuator. The input member is rotatable about an axis and has a hub, an outer rim, and a radially extending web that couples the hub to the outer rim. The cover is coupled to the input member for common rotation about the axis and cooperates with the input member to define a clutch cavity. The clutch is received in the clutch cavity and selectively transmits rotary power between the input member and the output member. The clutch actuator is selectively operable to change the operational state in which the clutch operates. The clutch actuator has an electromagnetic coil that is disposed outside the clutch cavity. The hub is disposed along the axis between the clutch and the electromagnetic coil.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 14/149,664 filed Jan. 7, 2014, which is a continuation-in-part of U.S. application Ser. No. 14/135,280 filed Dec. 19, 2013, which claims the benefit of U.S. Provisional Application No. 61/745,647 filed Dec. 24, 2012. This application is also a continuation-in-part of U.S. application Ser. No. 14/149,694 filed Jan. 7, 2014, which is a continuation-in-part of U.S. application Ser. No. 14/135,280 filed Dec. 19, 2013, which claims the benefit of U.S. Provisional Application No. 61/745,647 filed Dec. 24, 2012. This application is also a continuation-in-part of U.S. application Ser. No. 14/149,713 filed Jan. 7, 2014, which is a continuation-in-part of U.S. application Ser. No. 14/135,280 filed Dec. 19, 2013, which claims the benefit of U.S. Provisional Application No. 61/745,647 filed Dec. 24, 2012. Each of the above-referenced applications is incorporated by reference as if fully set forth in detail herein. 
    
    
     FIELD 
     The present disclosure relates to a driven accessory. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Accessories such as coolant pumps and cooling fans are in common use in modern vehicles that employ an internal combustion engine for the production of propulsive power or the generation of electricity. Such accessories are commonly driven by a belt directly or indirectly attached to the crankshaft of the engine and thus operate at a rotational speed that is related in a fixed manner to the rotational speed of the crankshaft. 
     It would be desirable to reduce the power that is consumed by such accessories to improve fuel economy and to reduce engine emissions. It would thus be preferable if such accessories could be made to operate with less power, or only when needed, in order to reduce the load on the engine and, in turn, improve fuel economy and reduce undesirable emissions from the engine. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form, the present teachings provide a driven accessory that includes an input member, a cover, an output member, a clutch and a clutch actuator. The input member is rotatable about an axis and has a hub, an outer rim, and a radially extending web that couples the hub to the outer rim. The cover is coupled to the input member for common rotation about the axis and cooperates with the input member to define a clutch cavity. The output member is rotatable about the axis independently of the input member. The clutch is received in the clutch cavity and is operable in a plurality of operational states including a first operational state, in which the output member is decoupled from the input member, and a second operational state in which the output member is coupled to the input member for common rotation. The clutch actuator is selectively operable to change the operational state in which the clutch operates. The clutch actuator has an electromagnetic coil that is disposed outside the clutch cavity. The hub is disposed along the axis between the clutch and the electromagnetic coil. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a cross-sectional view of a driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is an exploded perspective side view of the driven accessory of  FIG. 1 ; 
         FIG. 2A  is an exploded perspective top view of the driven accessory of  FIG. 1 ; 
         FIG. 3  is a view similar to that of  FIG. 1  but illustrating a solenoid in an unenergized condition and a clutch in an engaged state; 
         FIG. 4  is a view similar to that of  FIG. 1  but illustrating a solenoid in an energized condition and a clutch in a disengaged state; and 
         FIG. 5  is a cross-sectional view of another driven accessory constructed in accordance with the teachings of the present disclosure. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     For the purpose of promoting and understanding the principles of the present invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe them. It will nevertheless be understood that no limitation as to the scope of the invention is hereby intended. The invention includes any alternatives and other modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to persons of ordinary skill in the art to which the invention relates. 
     A driven accessory is shown in  FIGS. 1-4  and is generally indicated by reference numeral  200 . In the particular example provided, the driven accessory  200  is a coolant pump. The driven accessory  200  includes a housing  202  and an impeller  204  which is used to circulate the engine cooling fluid in the vehicle. 
     The housing  202  includes a base member  206  and a cover member  208 , which can be secured together by a plurality of threaded fasteners  210 . A solenoid actuated friction clutch assembly  212  is positioned in the housing  202 . A central shaft member  214  is positioned centrally in the housing  202  and is used to rotate the impeller  204 . The impeller  204  is positioned in a housing (not shown) and is connected to the shaft member  214  by a fitting assembly  216 . The lower end  214 L of the shaft is secured to the fitting assembly  216  in any conventional manner. 
     The driven accessory  200  also includes a pulley member  220 . The pulley member  220  is adapted to be driven by an engine belt, either directly or indirectly by the engine crankshaft. Although the outside surface  223  of the pulley member  220  is smooth in the drawings, but it can have any conventional shape in order to mesh or mate with the engine belt. 
     The shaft member  214  is rotatably supported in the housing  202  by a bearing  230 . Although only the bearing  230  is depicted and the bearing  230  is depicted with a single row of bearing elements, it will be appreciated that the bearing  230  can have more than one rows of bearing elements or can comprise stacked bearings. 
     The friction clutch assembly  212  includes an armature plate  232 , a friction plate  234  and two friction members  236 ,  238  that can be formed as annular rings from a friction material. The armature plate  232  is preferably made of a magnetically-susceptible material, such as low carbon steel. The friction plate  234  is preferably made of a non-magnetically susceptible material, such as stainless steel. 
     The friction members  236 ,  238  can be formed from any conventional friction material used in friction clutches today, and can be formed as complete rings, segments of rings, or simply pieces of friction material positioned generally where the friction members  236 ,  238  are shown in the drawings. The friction members  236 ,  238  are fixedly attached to the two sides of the friction plate  234  by, for example, bonding using a bonding agent. 
     The cover member  208  which preferably is made of a non-magnetically susceptible material, such as stainless steel, is connected directly to the pulley member  220 . In the example provided, the fasteners  210  fixedly couple the cover member  208  to the pulley member  220 . The ends of the fasteners can be threaded for mating with corresponding mating threads in openings  221  in the pulley member  220 . Thus, when the pulley member  220  is rotated by an engine belt (not shown); the cover member  208  rotates at the same speed. 
     The pulley member  220  is preferably made of a magnetically susceptible material, such as low carbon steel. The pulley member  220  rotates freely around bearings  240 . Although the bearings  240  can be of any type that will have sufficient durability and performance, a pair of stacked bearings  240  can be utilized, as shown in the drawings. 
     The operation of the friction clutch assembly  212  is performed by a solenoid assembly  250 . The solenoid assembly  250  includes a solenoid coil  252  that is positioned in the base member  206  of the housing  202 . The solenoid coil  252  comprises a donut-shaped coil of copper wires, while the base member  206  is preferably made of a magnetically susceptible material, such as low carbon steel. The solenoid coil  252  is preferably potted in the base member  206 . 
     A nut member  260  is threaded, or otherwise firmly fixed, on the end of the shaft member  214 . The friction plate  234  is connected, such as being keyed, to the nut member  260 . As shown in  FIG. 2 , the nut member  260  has a plurality of spline members  261  which fit within corresponding notches  235  in the center of the friction plate  234 . In this manner, the nut member  260  and friction plate  234  rotate with the shaft member  214 . The nut member  260  and the shaft member  214  firmly clamp a stop member  270  and the bearing  230  together. The shaft member  214  and all components fixed on it are positioned axially by the bearing  230 . The stop member  270  is preferably made of a non-metallically susceptible material, such as stainless steel. 
     To fix the bearing  230  in an axial position inside the base member  206 , a wave spring member  280  and bearing retainer member  282  are utilized. The bearing retainer member  282  is threaded to the base member  206  as shown by reference number  284 . 
     The stop member  270  is utilized to stop the axial movement of the friction plate  234  when the solenoid assembly  250  is energized, as explained below. A return spring  290  is positioned between the nut member  260  and the friction plate  234  and acts to return the friction plate  234  to its mechanical disengaged position when the solenoid assembly  250  is actuated. 
     The solenoid coil  252  is electrically powered through a controller (not shown) that can comprise a circuit board (not shown). Electrical leads and wires (not shown) can be insert molded in the base member  206  in order to carry the electrical signals to the solenoid coil  252 . The controller further communicates with the electronic control unit (ECU) of the vehicle through the vehicle communication network such as a CAN network. The controller could also be positioned inside the base member  206 , possibly having a donut shape. 
     The driven accessory  200  is selectively operated according to the cooling required for the engine. Sensors feed relevant data to the ECU which then sends a signal to the controller requesting that the driven accessory  200  be operated. The controller controls engagement of the friction clutch assembly  212  to cause the impeller  204  to be driven by the pulley member  220 . 
     When operation of the driven accessory  200  is not required, the friction clutch assembly  212  is held in a disengaged position by the solenoid assembly  250 . This is shown in  FIG. 4 . When the solenoid coil  252  is electrically activated, a flux circuit  300  is created which acts to pull the armature plate  232  toward the solenoid coil  252  overcoming the force of the coil springs  302 . With the armature plate  232  pulled toward the solenoid coil  252 , the return spring  290  holds the friction plate  234  against the stop member  270 . In this condition, the friction members  236 ,  238  on the friction plate  234  are not in contact with either the cover member  208  or the armature plate  232 . 
     The number of coil springs  302  and their biasing force is determined according to the force needed in the assembly. Six coil springs  302  are shown in the drawings, but there can be more or less than this amount depending on the force needed. 
     In this deactivation mode of operation, there are air gaps on the exterior sides of the friction materials on the friction plate  234 , and the input (pulley member  220 ) and output (shaft member  214 ) are disconnected. This eliminates any interaction, such as bearing drag between the input and output. 
     In order to create an appropriate flux circuit  300 , the pulley member  220  has a plurality of openings  310  which create air gaps. This is particularly shown in  FIG. 2A , as well as  FIG. 4 . The openings  310  essentially form an annular open ring. With the air gaps, the pulley member  220  is, for electromagnetic purposes, essentially an outer annular ring  312  and a separated annular inner ring  314 . The size, shape and number of openings or slots  310  are not critical, so long as they fulfill the purposes of creating a break in the magnetic flux. If desired, the openings can be closed by a non-magnetically susceptible material that permits the transmission of a magnetic field there through. For example, a plastic material can be fixedly coupled to the pulley member  220  to close the openings  310 . Configuration in this manner closes the cavity that is formed between the pulley member  220  and the cover member  208  so that dirt, debris and moisture does not enter into the cavity, which could deleteriously affect the operation of the friction clutch assembly  212  in some situations. 
     The flux circuit  300  is shown in  FIG. 4 . The flux circuit  300  runs through the base member  206 , the belt engaging portion  223  of the pulley member  220 , outer annular ring portion  312  of the pulley member  220 , and then jumps to the armature plate  232  and then back to the inner annular ring portion  314  of the pulley member  220  where it returns to the base member  206 . This circuit pulls the armature plate  232  tightly against the pulley member  220  such that the armature plate  232  rotates with the pulley member  220  and at the same speed. In this condition, the return spring  290  is able to urge the friction plate  234  away from the cover member  208  so that the coolant pump impeller  204  is not activated (i.e., neither the friction plate  234  nor the coolant pump impeller  204  are driven). 
       FIG. 3  depicts the situation where the solenoid assembly  250  is not activated. This is the “fail safe” condition in which the driven accessory  200  is configured to be driven by an engine belt and so that the impeller  204  is driven. In this situation, coil springs  302  force the armature plate  232  in a direction away from the pulley member  220  and away from the solenoid assembly  250 . This causes the armature plate  232  to contact the friction member  236  which in turn forces the friction member  238  to contact the inner surface  209  of the cover member  208 . Since the armature plate  232 , the pulley member  220  and cover member  208  are all fixed together; this causes the shaft member  214  and impeller  204  to rotate at the same speed. 
     A path of torque transfer which mechanically rotates the shaft member  214  is shown by arrows  320  in  FIG. 3 . When the friction clutch assembly  212  is in an engaged state, the friction plate  234  is clamped between the cover member  208  and armature plate  232  and torque is transferred through both sides of the friction plate  234 . There also is a torque transfer path from the pulley member  220 , through the fastener  210 , the armature plate  232 , the friction plate  234 , the nut member  260  and to the shaft member  214 . 
       FIG. 5  schematically depicts the use of the inventive friction clutch for operating a fan mechanism. The fan mechanism is referred to generally by the reference numeral  400 . 
     The friction clutch mechanism  410  is substantially the same as the friction clutch mechanism described above which is utilized to selectively rotate a coolant pump impeller. In this embodiment, the friction clutch mechanism is utilized to rotate a cooling fan. The components which are the same are referred to by the same reference numerals as set forth in the other Figures. The main differences are that the shaft member  214 ′, when activated, rotates a cooling fan assembly  420 . The fan assembly  420  includes a cooling fan  430  with a number of blade members  440  and central hub member  450 . The hub member  450  is securely attached to the shaft member  214 ′, and the fan  430  is securely attached to the hub member  450 , such that the housing fan and blades will rotate when the shaft member rotates and at the same speed. Any conventional means or mechanisms can be utilized to attach the components together so they all rotate together. 
     The present coolant pump and cooling fan devices are designed to be spring engaged so the accessory device is powered in the event of a control failure such as a loss of electrical power. This is done to provide “Fail-Safe” functionality meaning that the device defaults to its “on” state when it is not powered. If the electrical system of the coolant pump were to fail, the solenoid would be de-energized allowing the coil springs to force the friction clutch assembly to become engaged. Therefore the pump would operate in mechanical mode with the impeller driven by the pulley member through the clutch assembly, thus preventing overheating. 
     Although the invention has been described with respect to preferred embodiments, it is to be also understood that it is not to be so limited since changes and modifications can be made therein which are within the full scope of this invention as detailed by the following claims.