WO2017147251A1

WO2017147251A1 - Belt tensioner for motor generator unit

Info

Publication number: WO2017147251A1
Application number: PCT/US2017/019057
Authority: WO
Inventors: Keith D. Van Maanen; Philip J. Mott
Original assignee: Borgwarner Inc.
Priority date: 2016-02-28
Filing date: 2017-02-23
Publication date: 2017-08-31

Abstract

A tensioner system for engine accessories, particularly motor generator units. The system includes a curved tension member attached to a pivot member having two free ends. Pulley assemblies are positioned adjacent the two ends. A leaf spring can be added for additional tension force. The tensioner system provides spring force on a continuous belt in both torque directions.

Description

BELT TENSIONER FOR MOTOR GENERATOR UNIT

TECHNICAL FIELD

[0001] The present invention relates to tensioners for vehicle engine belt systems, and more particularly to tensioners for vehicle engine belt systems which include a generator.

BACKGROUND OF THE INVENTION [0002] Vehicles typically include one or more continuous belts which are operated by the engine to provide power to drive various engine accessories. These are called "serpentine" belts and are often included in front end accessory drive ("FEAD") systems. The accessories driven by the continuous belts include alternators, generators, AC compressors, power steering pumps, water pumps, and the like.

[0003] Tensioners and tensioning systems are routinely included in the path of the continuous belts in order to maintain tension in the belt spans as they pass around pulleys and prevent slippage.

[0004] Tensioning systems for continuous belt drives that include a motor generator unit (MGU) are challenging because MGUs develop torques in both directions (clockwise or counter clockwise). These tensioning systems require maintenance of tension in the belt spans on both sides of the MGU pulley. Known torque tensioner systems for MGUs are complex and expensive. They include numerous components and are difficult to assemble and repair.

[0005] It is an object of the present invention to provide an improved continuous belt tensioning system, particularly for MGUs, which has fewer components, is earlier to assemble and maintain, and which is less expensive than known l SUMMARY OF THE INVENTION [0006] The present invention provides a tensioning system for a continuous belt drive which meets these objects. The present invention provides a unique and beneficial continuous belt tensioning system which has fewer components, is less expensive, and is easier to manufacture, assemble and repair.

[0007] The inventive tensioning system includes a curved single piece tensioning member which is attached to a rotatable pivot member and has two free ends. Pulley assemblies are provided adjacent each of the two free ends and are adapted to be positioned on a continuous belt on either side of a MGU. The tensioner system maintains belt tension and prevents belt slip regardless of the torque direction of the MGU.

[0008] The pivot member is connected to the MGU or adjacent to it, and preferably includes a damping member, such as a bushing, Belleville washer or the like, to control the rotation. The two ends of the tensioning member locate and constrain the pulley assemblies, and also provide a spring force on the continuous belt at two belt spans. The spring force maintains the appropriate tension on the belt on either side of the MGU and prevents belt slippage.

[0009] The spring force created by the tensioning system on the continuous belt is adjustable depending on the torque generated by the MGU, as well as the geometry of the system. The spring force also permits deflection of the tensioning member without causing fatigue. The tensioner spring rate in combination with the belt system geometry is designed such that the belt tension increases exponentially when the MGU torque increases. This helps maintain the dynamic behavior of the system.

[0010] Openings can be provided in the tensioner member adjacent each of the two free ends. The openings can be adjusted in size and location to optimize the spring rate for the particular MGU and engine belt system.

[0011] Other features, benefits and advantages of the present invention will become apparent from the following written description of the invention, in combination with the attached drawings and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIGURE 1 is perspective view of an embodiment of the present invention.

[0013] FIGURE 2 is a schematic depiction of the use of an embodiment of the present invention on a vehicle engine.

[0014] FIGURE 3 depicts the movement of the free ends of a tensioner member in use maintaining belt tension adjacent a MGU.

[0015] FIGURE 4 is a cross-section taken along line 4-4 in Figure 3 and in the direction of the arrows.

[0016] FIGURE 5 depicts an alternate embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0017] Vehicle engines normally include a serpentine belt system to drive various engine accessories, such as AC compressors, water pumps, alternators and generators. Some of these systems are called front end accessory drive ("FEAD") systems. A single continuous belt driven by a pulley attached to the crankshaft of the engine is wrapped around and drives one or more pulleys which in turn operate the accessories. In order to prevent slippage of the belts on the pulleys, one or more tensioners or tensioning systems are utilized in order to maintain tension in the continuous belt as it is driven.

[0018] Continuous belt systems are more efficient than older multiple belt systems and consume less space in the engine compartment. By way of a single, wider belt instead of multiple, thinner belts, the continuous belt may be put under increased tension without stretching. Higher tension reduces slip which increases belt life and mechanical efficiency. Reduced slip can allow the use of lower-ratio pulleys; this reduces the load on the engine, increasing fuel economy and available power. The tendency of V-belts to "flip over" in the pulley groove is eliminated, and a serpentine belt is also easier to maintain and replace.

[0019] Most of the engine accessories operated by pulleys require torque only in one direction, typically clockwise. Motor generator units, or MGUs, can provide torque in both the clockwise and counter-clockwise directions. MGUs thus require tensioner systems which can accommodate torque in both directions.

[0020] Over time, many systems have developed to accommodate and provide b e l t tensioners in both torque directions for a MGU. These systems, however, typically have two separate tensioners with numerous components and are expensive to manufacture and assemble, as well as to maintain and repair.

[0021] The present invention provides a belt tensioning system which accomplishes the same result, but which is less expensive and has fewer components. In general, the system provides a single belt tensioner member affixed generally in its middle section to a rotatable pivot member. Pulley members are attached to the two free ends of the tensioner member and, by spring forces, maintain the appropriate tension in the continuous belt.

[0022] Although the present invention is described herein relative to its use with MGUs, it is also possible to utilize the tensioning systems with other engine components or accessories which require belt tension in both torque directions. These could include a water pump or an AC compressor, for example.

[0023] The preferred embodiment of the present invention is depicted in Figures 1 -4 and referred to generally by the reference number 10. The tensioning system 10 includes a main tensioning member 20, a pivot member 30, and a pair of pulley assemblies 40 and 50.

[0024] The tensioning member 20 is preferably made of a spring steel material or the equivalent which is bent into a generally U-shaped configuration as shown. The tensioner member 20 preferably is also heat treated. The material needs to provide a spring force in the free ends 22 and 24. The spring force provides a force inwardly in the direction of arrows 25 in Figures 1 and 3, in order to provide a tensioning force on the continuous belt member 60, regardless of the direction of the torque being applied to the belt by the MGU 70.

[0025] The tensioner member 20 is fixedly secured to the pivot member 30 generally in the middle section of the tensioner member 20. The manner of attachment could be, for example, welding, but any other conventional method or manner of attachment could be utilized.

[0026] The pivot member 30 shown in the drawings is a hollow metal tubular member, but any strong, durable member or material could be utilized, solid or tubular The pivot member also is preferably finished precision faced and bored. As shown in Figure 4, the pivot member 30 is attached to a shaft member 32 which in turn is rigidly affixed to a component or engine block or head 34. The component preferably is a MGU 70, as shown in Figures 2 and 3.

[0027] A damping member 36 is provided to control the rotation of the pivot member 30 relative to its fixed mount. The damping member could be, for example, a spring member like a Belleville-type washer, or a bushing member. One or more axial thrust washers could also be utilized.

[0028] With the spring force applied by the tensioner members attached to a rotatable pivot member, backside tension is provided during torque transients of the MGU.

[0029] In the tensioning system shown in Figures 2 and 3, the serpentine belt 60 is wound around a pulley member 62 on the MGU, a pulley member 64 on AC compressor 65 and a pulley member 66 on the face of a vehicle engine 68. An idler pulley 69 is also included in the system. The idler pulley is used to guide the continuous belt and allow it to operate effectively to drive the various accessories in the belt drive system.

[0030] The pulley members 40 and 50 are attached to the tensioner member 20 at or near the free ends 22 and 24. U-shaped bracket members 42 and 52 are used to attach the pulleys to the tensioner member 20 and hold them in place. The pulley members rotate in the bracket members on axle members, such as axle 54 shown in Figure 4.

[0031] The pulley members and bracket members can be any of the conventional pulley members and brackets used with engine belt systems today. They can be made of a metal or plastic material. The continuous belt member 60 also can be any of the conventional type of continuous belt members in use today for driving engine accessories.

[0032] The free ends 22 and 24 of the tensioner member 20 provide a spring force at all times on the continuous belt member 60. The static spring force can be adjusted depending on the torque provided by the MGU and the system geometries.

[0033] One manner of adjusting or tuning the spring force of the free ends of the tensioner member to provide openings adjacent the free ends, such as openings 80. The length, width and shape of the openings 80 can be varied to optimize the spring rate of the tensioner member on the belt member. Eliminating a portion of the material in the tensioner member also reduces the weight of the tensioner system 10 which is a benefit.

[0034] The length, width and thickness of the tensioner member are selected according to several factors, such as the size and power of the MGU and engine, and the space provided in the engine compartment for the tensioner system. The main factor is to provide the spring force required to maintain the appropriate amount of belt tension.

[0035] When the motor generator torque increases, tension in one side of the belt member will increase. At the same time, it is necessary to maintain some tension in the opposite side span (backside) to prevent belt slip. With the tensioner system 10, as the tight span tension increases, the tensioner assembly will rotate and the backside tensioner will also move and insure backside tension. This prevents belt slip during torque transients.

[0036] In addition, the tensioner and belt geometry is such that as the torque increases, the effective tensioner spring rate in the tight belt span increases exponentially. This maintains good system dynamic behavior. The damping at the center pivot also can be tuned to control the system's dynamic behavior.

[0037] The tensioner system 10 has a relatively simple construction and consists of only a few parts. This creates significant economics in the cost, manufacture and assembly of the tensioner system 10, as well as its maintenance and repair. The tensioner system 10 also is relatively small in size relative to known tensioner assemblies and systems for MGUs. This saves space in the engine compartment, particularly in the axial direction of the engine, since the system is mostly contained within the plane of the belt member.

[0038] An alternate embodiment 100 of the invention is depicted in Figure 5. In this embodiment, a curved single piece leaf spring member 105 is attached to the tension member 20. The remainder of the components are the same as those shown in Figures 1 -4 and described above. The embodiment has a main tensioning member 120 (the same as tension member 20) fixedly attached to a pivot member 130 (the same as pivot member 30), as well as two pulley assemblies 140 and 150 (the same as pulley assemblies 40 and 50). The leaf spring member 105 is fixedly attached, such as by welding, to the tensioning member 120 near the pivot member The leaf spring member 105 is preferably a metal made of a spring steel material and applies additional tensioning forces to the tensioning member 120 in the direction of arrows 125.

[0039] Bent ends 107 and 109 on the ends of the leaf spring member 105 are utilized to direct the tensioning forces at certain locations as desired. The relative motion between ends 107 and 109 with member 120 also provide damping to the system when member 120 flexes.

[0040] While the invention has been described in connection with one or more embodiments, it is to be understood that the specific mechanisms and techniques which have been described are merely illustrative of the principles of the invention, numerous modifications may be made to the methods and apparatus described without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

What is claimed is:

1. A belt tensioner system for a motor generator unit, said system comprising a rotatable pivot member, a curved single piece tensioner member fixedly attached to said pivot member, said tensioner member having two free ends, and a pair of pulleys, each of the pulleys being attached to an associated one of said two free ends of said tensioner member, said tensioner member biasing the pulleys toward one another.

2. The belt tensioner system as described in claim 1 wherein said tensioner member has a general U-shaped configuration.

3. The belt tensioner system as described in claim 2 wherein said pivot member is attached to said tensioner member substantially in the midpoint of said U- shaped configuration.

4. The belt tensioner system as described in claim 1 further comprising a damping member attached to said pivot member, wherein rotation of said pivot member and tensioner system is controlled.

5. The belt tensioner system as described in claim 1 wherein each of said pulleys comprise a pulley member rotatably positioned in a bracket member, said bracket member being attached to said tensioner member adjacent said free ends.

6. The belt tensioner system as described in claim 1 further comprising openings in said tensioner member, wherein the spring force of said free ends of said tensioner member is adjusted.

7. The belt tensioner system as described in claim 1 further comprising a leaf spring member attached to said tensioner member.

8. A method of applying tension to a continuous belt member provided to drive an engine accessory member, said method comprising:

providing a tensioner member on the continuous belt member, said tensioner member being a curved single piece member fixedly attached to a pivot member, said tensioner member having a substantially U-shaped configuration with two free ends, and a pulley assembly positioned on each of said two free ends; positioning the pulley assembly on the two free ends of the tensioner member on the continuous belt member on each side of the accessory member; and providing spring tensioning forces on said continuous belt member at each of said two ends of said tensioner member.

9. The method as described in claim 8 further comprising the step of providing a damping member on said pivot member, wherein rotation of said pivot member is controlled.

10. The method as described in claim 8 further comprising the step of providing at least one opening in said tensioner member, wherein the spring force of said free ends on the continuous belt member is adjusted.

11. A method as described in claim 8 further comprising fixedly attaching a leaf spring member to the tensioner member.