GB2180022A - Variable speed accessory drive - Google Patents

Abstract

The variable speed accessory drive comprises an accessory drive gear unit 48 having a torque input element 54 connected to a driveline input member 10, a reaction element 50, and a torque output element 52 connected to engine driven accessories. The ratio of the speeds of the accessories with respect to the driving engine speed is variable by the reaction element 50 and is functionally related to the magnitude of the speed ratio in the geared torque delivery path. In the first embodiment shown the input (10) drives a planet carrier (46), a torque converter turbine (16) is connected via a one way clutch (60) with a brakeable ring gear (50), and the accessories are driven from a sun gear (52) the main vehicle driveline (40) being driven via a transfer belt or chain gearing. In a second embodiment the sun gear is connected to the vehicle driveline, a cluster gear assembly, and the ring gear to the accessories. <IMAGE>

Description

SPECIFICATION Variable speed accessory drive The invention relates to an accessory drive for a vehicle driveline, which driveline includes an internal combustion engine with engine driven accessories, and a variable ratio transmission mechanism including atorque input member driven by the engine, a torque output member, and gearing establishing plural torque delivery paths between said torque input member and said torque output member.

The invention is intended for application to an internal combustion engine driveline for a wheeled vehicle wherein the engine crankshaft is connected to the vehicle traction wheelsthrough multiple ratio gearing and wherein components ofthe gearing are used to establish a variable ratio drive between a torque output element ofthe gearing and the accessoriesfortheenginesuch asthe engine cooling fan, the water pu m p, the a Iternator, the air conditioning compressor and the power steering pump.

According to the present invention, there is provided a variable speed accessory drive for a vehicle driveline, which driveline includes an internal combustion engine with engine driven accessories, and a variable ratio transmission mechanism including a torque input member driven by the engine, a torque output member, and gearing establishing plural torque delivery paths between said torque input member and said torque output member, the variable speed accessory drive comprising an accessory drive gear unit having a torque input element adapted to be connected to said torque input member, a reaction element, and a torque output element adapted to be connected to engine driven accessories, the ratio of the speeds of the accessories with respect to the driving engine speed being variable by the reaction element and being functionally related to the magnitude ofthe speed ratio in the geared torque delivery path.

In afirstembodimentoftheinvention,to use in a vehicle in which the multiple ratio transmission mechanism comprises a hydrokinetictorque converter having an impeller and aturbine,the impeller being connected to said torque input member, clutch means are provided for connecting the turbineto the reaction element of said accessory drive gear unit.

In this case, the connection between the turbine and the reaction input element preferably comprises an overrunning clutch, and brake means for anchoring selectively the reaction element.

In a second embodiment ofthe invention, for use in a vehicle in which the variable ratio transmission mechanism comprises a cluster gear assembly, the torque input member and the cluster gear assembly having meshing pairs of gear elements, each pair having a separate gear ratio, the reaction element of said accessory drive is geared to the cluster gear assembly so that the accessories may be driven at a speed that varies relative to the speed ofthetorque input member depending upon the selected gear ratio of said multiple ratio transmission mechanism.

The improvement ofthe present invention makes it possible to design the accessories for the engine with a reduced size and capacitythereby reducing the cost, the weight and the rotational inertia ofthe accessory drive elements. This is accomplished by enabling the accessories to be driven at a speed that is increased with respect to the speed of the engine when the engine is idling and progressively reducing the speed relative to engine speed as the transmission speed ratio changes during acceleration of the vehicle from a standing start to a cruising drive mode.

In this way, the load requirements of the accessories are reduced as the vehicle approaches a cruising condition. The invention therefore make it possible to reducethe parasitic engine power loss by designing the capacity of the accessory components to be more compatible with the actual power requirements ofthe accessories at each speed ratio ofthe driveline.

In the first embodiment of the invention, as mentioned above, provision is made in the accessory drive gearing for achieving an overdrive ratio for the accessories with respect to the engine speed when the engine is idling. The driveline includes a hydrokinetictorque converter, the turbine ofwhich is stalled when the engine is idling and the vehicle is stationary. As the vehicle accelerates, the torque converter speed ratio changes from zero to a value approaching unityattheconvertercoupling point.

That change in speed ratio is accompanied by a corresponding reduction in the speed ratio ofthe accessory drive so that the accessory drive gearing approaches a ratio of approximately 1:1 with respect to the engine speed. A lockup clutch then is applied to prevent converter slip, and thereafter the accessories are driven at a 1:1 drive ratio.

In the second embodiment ofthe invention the accessory drive gearing has been combined with countershaft gearing in a transaxle driveline. The accessories are overdriven with respect to the engine when the vehicle is stationary and the neutral clutch is released. When the clutch is engaged the vehicle driveline ratio is changed in increments until a high speed ratio is achieved. As gear ratio changes occur in sequence, the accessory drive ratio decreases until it reaches its minimum valuewhen thevehicle is in the high speed ratio cruising condition.

The invention will now be described further, by way of example with reference to the accompanying drawings in which: Figure lisa schematic representation of a hydrokinetictorque converter transmission in combination with an accessory drive, and Figure2 is a countershaft multiple ratio transmission for a vehicle driveline wherein the accessory drives are combined with the stepped ratio gearing rather than the torque converter of the Figure 1 embodiment.

In Figure 1 numeral 10 designated the crankshaft of an internal combustion engine. It is connected by means of a drive plate to the bladed impeller 12 of a hydrokinetic torque converter 14. The converter 14 includes a bladed turbine 16 and a bladed stator 18 arranged in toroidal fluid flow relationship with respect to the impeller 12. An overrunning brake 20 is adapted to distribute reaction torque on the stator 18 to a stationary sleeve shaft 22, which is connected to thestationarytransmission housing.

Crankshaft 10 is connected directly to torque input shaft 14.Aconverter lock-up clutch 26, which maybe a flu id pressure servo operated friction clutch selectively operable by control elements, not shown, connects input shaft 24 with drive sleeve shaft 28 to which is connected a drive sprocket or pulley 30. The sprocket or pulley 30 is connected drivablyto a driven sprocket or pulley 32 mounted for rotation about the axis of shaft 34 which is situated in spaced parallel disposition with respect to the shaft 24. The driving connection between the sprocket or pulley 30 and the sprocket or pulley 32 is a constant ratio belt or chain drive connection such as that shown in U.S.

patent 3,605,522. Figure 3, or patent 3,031,893, Figure 6. In the alternative,the drive connection may be a continuously variable ratio belt or chain such as that shown in U.S. patent 4,060,012 where adjustable sheavesonthetorque inputend of a driveline andon the torque output end of the driveline are comprised of axially adjustable sheave portions that register with a belt or chain so that the effective pitch diameter ofthe pulleys is changed upon axial adjustmentofthe sheave portions.

Output shaft 34 is a sleeve shaft that is connected to each of two output drive shafts 36 and 38 by multiple ratio gearing schematically illustrated at 40.

Each driveshaft36 and 38 is connected to a traction wheel, not shown, by means of a U-joint as shown at 42 and 44, respectively.

Input shaft 24 is connected to the carrier 46 of a simple planetary accessory drive unit 48. The drive unit 48 includes a ring gear 50, sun gear 52 and planet pinions 54 carried by the carrier 46 in meshing engagementwith the ring gear50 and the sun gear 52. The sun gear 52 is connected to an accessory drive pulley 56 which in turn is adapted to be connected to engine driven accessories such as the engine water pump, the cooling fan, the alternator, the power steering pump, the air conditioning compressor and possibly the automatic transmission oil pump. The ring gear 50 is adapted to be braked by a selectively engageable reaction brake 58.When the brake 58 is disengaged, reaction torque may be accommodated by one way clutch 60 which connects sun gear 50 with lockup clutch portion 62, the latter in turn being connected to drive sleeve shaft 28.

During operation ofthe driveline in neutral and when the transmission is in the part condition, accessory drive pulleys 56 are overspeeded as the brake 58 is applied. The turbine ofthetorque converter rotates at engine speed since the converter speed ratio under such no-torque drive conditions is approximately 1:1. Turbine torque during operation in one ofthe drive modes is transferred through the drive chain or belt 64to the multiple ratio gearbox 40.

When the gearbox40 is shifted into gear, brake 58 is released and reaction torque on the ring gear 50 is accommodated bythe one-way clutch 60 which holds the ring gear stationary until the vehicle begins to move. If desired, vehicle creep can be avoided after the gearbox is shifted into gear by reapplying brake 58 thereby preventing accessory drive torque from feeding backfrom the ring gear to the turbine.

The brake 58 may be useful also as a kill holder while the vehicle is idling in gear and the vehicle is parked on a grade.

When the accelerator is depressed, the brake 58 is released and the reaction torque of the accessory drive bears fully on the turbine shaft th rough the one way clutch.

Asthe vehicle accelerates the turbine gains speed with respect to the impeller and the engine. This causes the gearset element speeds to approach a 1:1 speed ratio relationship so that the sun gear 52 drives the accessories at a progressively decreasing speed until the speed of the drive pulley 56 approaches engine speed.

In the embodiment of Figure 2 the engine crankshaft is shown at 66. It is connected through a selectively engageable neutral clutch 68 to torque input sleeve shaft 70 which surrounds torque input shaft 72, the latter in turn being connected to carrier 74 of accessory drive planetary gear unit 76. Gear unit 76 includes, in addition to the carrier 74, sun gear 78, ring gear80 and planet pinions 82 which are journalled on carrier 74. Ring gear 80 is connected to accessory drive pulley 84.

Sun gear 78 is connected to first ratio torque input gear86which meshes with gear element 88 of a countershaft gear assembly 90. A second ratio torque input gear 92 meshes with second ratio gear element 94 of countershaft gear assembly90, a third ratio input gear 96 meshes with a third ratio gear element 98 of countershaft gear assembly 90 and a fourth ratio input gear 100 meshes with a fourth ratio gear element 102 of countershaft gear assembly 90.

Final drive gearing 104 meshes with gear element 106 ofcountershaft gear assembly 90. Final drive gear 104 drives the carrier of a differential unit 108, the side gears 110 and 112 of which are connected respectively to the traction wheels through U joints 114 and 116.

Double acting synchronizerclutch means is adapted to connect selectively the input sleeve shaft with the first ratio input gear 86 and the second ratio input gear92. Such synchronizer assemblies are common, an example of such a synchronizer being shown in U.S. patent 3,318,168. In a similarfashion the double acting synch ronizer assembly provides selectively a connection between driving input gear 96 and the input shaft 70 and a driving connection between input gear 100 and input shaft 70. The synchronizer assemblies for the first and second ratio and for the third and fourth ratio are shown respectively at 118 and 120.

In the embodiment of Figure 2, with the vehicle stationary, the accessories are overspeeded with respect to the engine. When the clutch is engaged and the vehicle proceeds from a standing start in the first ratio, the accessory drive ratio becomes 1:1. In the higher gear ratios the sun gear rotates fasterthan the rest ofthe elements of accessory drive gear unit 76 thereby slowing the accessory drive pulley to a speed less than engine speed. The slowing of the accessory drive becomes more pronounced in each successive gear.

At each of the two embodiments it is possible to design the accessories with a lower capacity while covering all ofthe design requirements regardless of engine speed thereby saving fuel and leaving more engine power available for performance purposes.

The design criteria for the accessories can be simplified further because they may be designed for high efficiency in a narrowed speed range.

Claims (5)

1. Avariable speed accessory drive for a vehicle driveline, which driveline includes an internal combustion engine with engine drive accessories, and a variable ratio transmission mechanism including a torque input member driven bythe engine, a torque output member, and gearing establishing plural torque delivery paths between said torque inputmemberand saidtorqueoutput member, the variable speed accessory drive comprising an accessory drive gear unit having a torque input element adapted to be connected to said torque input member, a reaction element, and a torque output element adapted to be connected to engine driven accessories, the ratio of the speeds of the accessories with respect to the driving engine speed being variable by the reaction element and being functionally related to the magnitude ofthe speed ratio in the geared torque delivery path.

2. A variable speed accessory drive as claimed in Claim 1 ,wherein said multiple ratio transmission mechanism comprises a hydrokinetictorque converter having an impeller and a turbine, the impeller being connected to said torque input member and wherein clutch means are provided for connecting saidturbinetothe reaction element of said accessory drive gear unit.

3. Avariable speed accessory drive as claimed in Claim 2, wherein the connection between said turbine and said reaction input element comprises an overrunning clutch, and brake means for anchoring selectively said reaction element.

4. Avariable speed accessory drive as claimed in Claim 1, wherein said variable ratio transmission mechanism comprises a cluster gear assembly, said torque input member and said cluster gear assembly having meshing pairs of gear elements, each pair having a separate gear ratio, and wherein the reaction element of said accessory drive is geared to said cluster gear assembly whereby said accessories may be driven at a speed that varies relative to the speed of the torque input member depending upon the selected gear ratio of said multiple ratio transmission mechanism.

5. A variable speed accessory drive constructed arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.