Buckling spring members, preferably for friction clutch assemblies, are disclosed.
Water pumps are used in water cooled engines, primarily for operation of vehicles such as automobiles and trucks with internal combustion engines. The water pumps are typically driven by a belt attached to the crankshaft of the engine and thus operate at some percentage of engine speed. The pumps have an impeller that is used to circulate the engine coolant from the engine to the radiator and back in order to keep the coolant within acceptable temperature limits.
Efforts are being made today to reduce the power consumption of engine accessories, such as water pumps, in order to improve fuel economy and reduce emissions. A unique dual mode water pump is disclosed in U.S. patent application Ser. No. 61/474,862. That device operates with less power, reduces engine load, improves fuel economy and reduces undesirable emissions.
The water pumps disclosed in Ser. No. 61/474,862, have two modes of operation, a first mode mechanical driven by the engine belt, and a second mode operated by an electric motor, such as a brushless DC (BLDC) motor. The components for the two modes of operation are contained within a housing that includes the pulley member as part of the housing. A shaft connected to the impeller of the water pump is positioned in the housing and is controlled by one mode of operation or the other, depending on certain factors.
The housing is turned at input speed by the belt of the engine positioned on the pulley member. A friction clutch mechanism is provided inside the housing to selectively allow operation of the water pump mechanically by the pulley member. A solenoid is utilized to control operation of the friction clutch mechanism. A spring member is provided which “softens” as it is displaced and minimizes the electrical power consumed by the clutch.
The water pump is normally driven by the electric motor throughout most of its range of operation. Where peak cooling requirements are needed, the mechanical mode of operation takes over and the water pump is driven directly by the pulley member. The dual mode cooling pump uses less power, improves fuel economy for the vehicle, and reduces emissions.
An improved spring member is disclosed for a friction clutch mechanism for a dual mode water pump. The unique structure of the spring member has a region of positive stiffness and another region of negative stiffness in its performance. As the spring member is compressed, the spring force increases rapidly to its maximum. As it is further compressed, the spring force decreases almost linearly to a small value.
The spring member has a circular shape and an outer annular planar ring and an inner annular planar ring. The center area of the spring member is concave and has a plurality of openings or “windows” positioned between the inner and outer rings. The rings are flat and add stiffness and rigidity to the structure.
In a preferred embodiment, the spring member is made of a thin metal material, preferably about 0.3 mm in thickness. Due to the concave structure of the device, the height difference between the inner and outer rings in the preferred embodiment is about 2.5 mm.
The openings in the center area are preferably “heart” shaped. Six openings are preferably provided, although a different number also could be utilized. The areas between the openings are called “spokes”.
In use in a dual mode water pump, the spring member is positioned adjacent an armature plate which is selectively moved axially by a solenoid assembly. Friction lining members are connected or attached to an outer ring positioned around the spring member and attached to an armature plate. Return of the spring member to its normal shape moves the friction lining members into contact with the inside surface of the pump housing and effects mechanical operation of the pump.
Further objects, features and benefits of the invention are set forth below in the following description of the invention when viewed in combination with the drawings and claims.
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 buckling spring member and friction clutch mechanism which would normally occur to persons of ordinary skill in the art to which the invention relates.
The present inventions described herein particularly relate to spring members which are selectively solenoid activated in order to change the mode of operation of a dual mode water pump. The present invention, however, can also be used in other situations and other assemblies for other products.
For purposes of describing the structure, use and operation of the inventive buckling spring member, and its improvement over the compression spring members disclosed in U.S. application Ser. No. 61/474,862, the unique and beneficial dual mode water pump assembly in that application will first be discussed.
As a coolant pump, the dual mode water pump is electrically driven under most conditions. However, it also can be mechanically engaged where more cooling is required. When the vehicle is being driven under most normal conditions, the water pump is being driven and operated by the electric motor. During “worst case” cooling conditions, such as when the vehicle is heavily loaded, when it is pulling a trailer, when it is going up hill in the summertime, etc., the water pump is adapted to be mechanically driven by the belt directly from the engine. This provides the necessary cooling under such circumstances.
In accordance with a preferred embodiment of the dual mode water pump, the electric motor is a brushless DC (BLDC) motor and the motor is positioned inside a pulley assembly. The pump is also adapted to be driven mechanically when needed by the engine belt, such as a serpentine belt, attached to the crankshaft of the engine.
The dual mode water pump is shown in
A cross-sectional view of the water pump 20 is shown in
The water pump has an impeller shaft 40 which is positioned within the pulley assembly 22 and also is attached to a water pump impeller 42. The impeller shaft 40 is held in place in the pump housing 24 by needle bearing 44 and middle bearing 84. A coolant seal 46 is used to prevent coolant in the pump from leaking into the pulley assembly.
A motor stator 50 is positioned inside a stator housing 52 in the pulley assembly 22. A nut, such as a spanner nut 54, is used to hold the stator housing 52 to the pump housing 24. A second needle bearing 60 is positioned between the pulley member 28 and the pump housing 24 in order to allow the pulley assembly 22 to rotate freely relative to the pump housing.
A motor rotor 70 is positioned inside a front bearing carrier 72, which preferably is made from an aluminum material. The motor is preferably a brushless DC (BLDC) electric motor. A solenoid member 80 is positioned immediately adjacent the front bearing carrier 72. A friction clutch assembly 90 is positioned adjacent the front cover of the motor housing 22 and operated by the solenoid member 80. Bearing member 84 is positioned between the bearing carrier 72 and the impeller shaft 40.
A fastening member such as a hex nut 92 secures the pulley assembly 22 to the impeller shaft 40 via the front bearing 82. As indicated particularly in
As indicated, the water pump is normally driven by the electric motor. The electric motor is electrically powered through a circuit board (not shown) connected to pin-type contact members 86. Electrical leads and wires can be insert molded in housing 25 and lead frame 29 in order to carry the electrical signals to the electric motor stator 50 and solenoid 80. The circuit board further communicates with the electronic control unit (ECU) of the vehicle through the vehicle communication network such as a CAN network. The pump controller circuit board could also be positioned inside the pulley assembly 22 rearward of the stator housing 52 and having a donut shape.
The speed of the motor and thus the water pump is selected according to the cooling required for the engine. Sensors feed relevant data to the ECU which then sends a signal to the pump controller requesting the desired speed. The pump controller then determines whether the desired speed is best achieved using the electric motor or by engaging the friction clutch and driving the impeller directly from the pulley.
An enlarged view of the friction clutch assembly 90 is shown in
An enlarged view of one embodiment of a compression spring member 104 is shown in
The spring member 104 has a plurality of holes or openings in order to be attached to the friction lining carrier member and the clutch carrier member. In this regard, a series of four holes 110 are provided on the compression spring member 104 in order to mate with openings 112 in the friction lining carrier member 106. A plurality of rivets 114 or the like are used to secure the compression spring member 104 to the friction lining carrier member 106. The compression spring member can be joined to the friction lining carrier member by any conventional method, such as by welding, brazing, threaded fasteners, etc.
The second series of openings in the compression spring member include four openings 120. These openings mate with corresponding post members 122 on the clutch carrier member 100. The post members 122 are deformed or swaged over when the friction clutch assembly 90 is assembled in order to securely hold the components of the friction clutch assembly together. The compression spring member embodiment 104 has an outer ring member 130 and an inner ring member 132. The two ring members 130 and 132 are connected together by a plurality of connecting members 134, 135, 136 and 137.
When the friction clutch assembly 90 is in the engaged position, torque is transferred from the pulley assembly 22 through the friction lining members 108 to the friction lining carrier 106. The friction lining carrier then transfers torque through the compression spring member 104 to the clutch carrier 100 which turns the impeller shaft.
When the friction clutch assembly 90 is energized by the solenoid 80, the flux plate 102 is attracted to the solenoid assembly due to the force developed in the air gap between the solenoid core 81 and the flux plate. As the flux plate 102 moves toward the solenoid, the compression spring member 104 is compressed separating the friction lining carrier member 106 and friction members from their engaged positions against the inside surface of the clutch housing member 26. In the compressed condition, the connecting members 134, 135, 136 and 137 are buckled and distorted. In this position, the water pump is operated only by the electric motor.
The flux plate 102 is securely attached to the friction lining carrier 106 through tabs 107 (
The load/deflection curves comparing the operation of the compression spring member 104 with the buckling spring member 150 discussed later is shown in
It is common in automotive accessories such as air conditioning compressors, pumps, etc. to use spring engaged, electromagnetically disengaged clutches to selectively turn on and off the drive to the accessory component. This is typically done to conserve energy when the device is not needed. These devices are typically 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 unpowered.
As indicated above, the dual mode water pump provides a “fail safe” friction clutch design. If the electrical system of the vehicle were to fail, the solenoid would be de-energized allowing the spring 104 to engage the friction clutch assembly to the clutch housing. Therefore the pump would operate in mechanical mode with the impeller driven by the pulley through the clutch assembly. The clutch is thus engaged whenever circulation of coolant is needed.
The primary disadvantage of these “Fail-Safe” clutch designs is that they require continuous electrical power to keep the device disengaged when it is not needed. For many accessory devices this condition can constitute a large percentage of their operating life. Furthermore, these devices often require 20+ watts of electrical power, which can be a significant portion of the alternator output. On modern vehicles which employ a large number of electrical components (seat heaters, window defrosters, electric seats, and a host of other devices), it is not uncommon to exceed the maximum power capacity of the alternator.
An embodiment of a solenoid assembly is shown in
The solenoid assembly includes a solenoid core 260, a coil member 270, a flux plate member 280, an armature plate 290 and a stop member 200.
The solenoid core has basically a dish or cup-shape with a cavity 262 and preferably is made of a magnetic metal material, such as low carbon steel. The coil member is made of a coiled copper wire and has a typical “donut shape.” In the assembly, the coil member 270 is press fit or potted in the cavity 262 in the solenoid core 260 to minimize air gaps.
The flux plate member 280 has an outer ring member 282 and an inner ring member 284. The two ring members are connected by several connection members 286 (a/k/a “bridge members”). Although three connection members 286 are shown in
The flux plate member 280 is made of a magnetic metal material, such as low carbon steel. The flux plate member 280 is pressed into the cavity 262 in the solenoid core 260 on top of the coil member 270 and preferably is positioned directly against the coil member.
The solenoid core 260 has a central opening 264 with an annular flange 266 which allows the solenoid core to be positioned around the central shaft member 40 in the dual mode water pump. The coil member 270 has a corresponding opening 272 which fits tightly around the flange 266.
The armature plate 290 is also made of a magnetic metal material, such as low carbon steel. It has a central opening 292 in order to be positioned around the shaft member 40 and stop member 300.
The stop member 300 is made of a non-magnetic material, such as aluminum or stainless steel. It has a central opening 302 in order to be positioned around the shaft member 40 and also has a ledge or shoulder member 304. The length of the body of the stop member is sized to rest against the bearing members 84 or another member which cannot move axially in the dual mode water pump. This prevents the stop member from sliding or moving axially.
As indicated in the drawings, the height 306 of the ledge or shoulder member 304 is above or greater than the height or top edge 268 of the solenoid core 260. This prevents the armature 290 from coming directly in contact with the flux plate 280 when the solenoid is activated. For this purpose, the armature plate 290 has a properly sized central opening 292, or a series of finger members 294 which allow the armature plate to contact the ledge or shoulder member 304.
A deformable spring member 310 is positioned in contact with armature plate 290 (see
During normal operation of the dual mode water pump, the solenoid assembly is activated. The flux plate 280 which is energized by the solenoid coil 270, pulls the armature plate 290 against the ledge or shoulder on the stop member 300. This compresses and buckles the spring member 310, and prevents the friction members 314 from contacting the inside surface of the pump housing. This allows the water pump to be rotated solely by the electric motor. When it is necessary to mechanically operate the water pump (as explained above), or operate it under both of the dual modes, power to the solenoid is turned off. This allows the spring member 310 to return toward its rest condition and forces the friction members 314 into the contact with the pump housing.
The flux circuit 320 is shown in
The flux plate 280 reduces the reluctance of the solenoid. This allows the solenoid to have more force. The flux plate also reduces the current necessary to maintain the same force.
The unique buckling spring member 310 is shown in more detail in
A plurality of openings or “windows” 360 and a plurality of spoke members 362 are provided in the center portion 356. The windows 360 are preferably heart-shaped with the pointed ends of the openings adjacent the inner ring member 354. The areas marked “A” in
Preferably six openings 360 and six spokes 362 are provided, although the number of openings and spokes could be in the range from 4 to 8. Under four spokes, the spokes could be too wide, making the spring too rigid, and over 8 spokes, the spokes could be too narrow, and not providing sufficient return biasing force, in order to effectively achieve the advantages of the invention.
A plurality of holes 370 are provided on the outer ring 352. The holes are used to mount the friction member 314, or an annular carrier member 312 with friction members on it. Such a carrier member is shown in
As indicated from
When the shape of the buckling spring member is formed, the inner and outer rings are clamped while a press or other fixture is used to form the concave structure of the center portion.
In a preferred embodiment, the thickness of the metal material for the spring member is about 0.3 mm. Also the distance “D” in
A load-deflection curve of the concave buckling spring member 310 is shown in
The buckling spring member provides the engagement force for the friction clutch in the mechanical mode of the dual mode water pump. The spring member also transfers torque. Also, as shown in
The structure and design of the spring member is easier to make and to hold tolerances than spring member 104. The tooling is not difficult to make and the positioning is easier during stamping. Assembly into a friction clutch mechanism is also easier and less time consuming since there are no rivets, rollover or spot welding needed.
As shown in
The unique configuration also transfers torque from the outer ring to the inner ring.
The friction carrier member 312 also is attached to the armature plate member 290. A plurality of connection members 402 are provided which are secured to the armature plate 290 by fastener members 404, such as small screw members. As shown in
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.
This application claims priority to U.S. application Ser. No. 61/725,467 filed on Nov. 12, 2012, which is related to U.S. patent application Ser. No. 61/474,907, entitled “Compression Spring Members,” filed on Apr. 13, 2011, now PCT/US2012/032876 filed on Apr. 10, 2012.
Filing Document | Filing Date | Country | Kind |
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PCT/US2013/068246 | 11/4/2013 | WO | 00 |
Number | Date | Country | |
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61725467 | Nov 2012 | US |