Engine Camshaft And Accessory Drive

Abstract

An overhead camshaft engine has a toothed belt drive wherein the back side of the belt is grooved to mate with multiple vee grooves and ridges of the water pump and fan drive pulley. The water pump is laterally movable on the engine block to provide a belt tension adjustment. The arrangement provides positive drive of the camshaft with nonpositive drive of the water pump and fan to permit slippage of the latter during excessive torque loadings.

Description

FIELD OF THE INVENTION

This invention relates to camshaft and accessory drives for internal combustion engines and, in its more particular aspects, to a drive arrangement which provides positive drive of the camshaft and nonpositive drive of the engine water pump and fan.

SUMMARY OF THE INVENTION

The present invention provides a camshaft drive arrangement for an overhead camshaft engine which utilizes a cog or toothed belt to positively connect the crankshaft and camshaft for driving the latter. The back of the cog belt is provided with multiple longitudinally extending grooves which drivingly engage the drive pulley of the engine water pump and fan to drive these accessories in a nonpositive manner. The engine water pump is adjustably mounted on the engine block to provide an adjustment for tensioning the cog belt and is also arranged to deliver coolant directly to the coolant cavity with clearance being provided for the required adjusting movement of the water pump impeller.

The arrangement provides the required positive drive of the camshaft while permitting excessive acceleration loads on the belt to be relieved by slippage of the water pump and fan portion of the drive during excessive torque situations. These and other advantages of the present arrangement will be more thoroughly understood from the following description of a preferred embodiment, taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a pictorial view of an internal combustion engine having camshaft and accessory drive means according to the invention;

FIG. 2 is a front view of the engine of FIG. 1 showing the belt and pulley drive arrangement and details of the adjustable water pump; and

FIG. 3 is a cross-sectional view taken generally in the plane indicated by the line 3--3 of FIG. 2 and showing the application of the water pump to the engine cylinder block.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in more detail, numeral 10 generally indicates an internal combustion engine having a cylinder block 12 in which is rotatably mounted a crankshaft 14. A cylinder head 16 is secured to the upper portion of block 12, closing the upper ends of the engine cylinders 18 and rotatably mounting an overhead camshaft 20. The interior portion of the cylinder block 12 includes a coolant cavity 22 through which cooling liquid is passed for cooling the cylinders. Coolant cavity 22 connects with passages (not shown) in the cylinder head for cooling portions thereof in a conventional manner.

Crankshaft 14 has a toothed pulley 24 mounted on one end thereof which extends from the front of the engine block. Camshaft 20 extends parallel to crankshaft 14 and has a second toothed pulley 26 mounted at one end thereof and in alignment with the crankshaft pulley 24.

Intermediate the two pulleys is a water pump 28 mounted on the front of the engine block so as to close an opening from the coolant cavity 22. The water pump carries an impeller 30 located inside the cavity 22 and secured to the end of a rotatable shaft 32. The shaft extends through a seal 34 and bearing 36 to connect with a drive pulley 38 carried on the shaft. An inlet connection 40 is adapted to receive water from an external source to be delivered by rotation of the impeller 30 directly into the coolant cavity 22. Clearance is provided within the coolant cavity to permit lateral movement of the water pump on its mounting, such movement being provided for by slotted openings 42 and extended gasketing surfaces 44 of the water pump housing. Bolts 46 are utilized to secure the water pump in any desired position within its range of lateral adjustment.

On the front of pulley 38 there is secured a fan 48, which is adapted for moving air through the radiator of a vehicle in which the engine may be mounted. Pulley 38 includes on its periphery a plurality of longitudinally spaced annular vee grooves 50 for a purpose to be subsequently described.

A drive belt 52 is provided to drivingly interconnect pulleys 24, 26 and 38 and thereby provide for driving the camshaft, water pump and fan from the crankshaft. The interior surface of belt 52 is provided with cogs or teeth 54 which engage the toothed surfaces of pulleys 24 and 26 so as to positively time the camshaft rotation with respect to that of the crankshaft. The water pump and fan drive pulley 38 engages the outer surface 56 of belt 52 which includes a plurality of longitudinally extending ridges and grooves having vee-angled sides which mate with the vee grooves 50 of the pulley 38 so as to provide a relatively large load carrying drive surface in spite of the relatively short length for which belt 52 wraps around pulley 38.

In operation, the crankshaft positively drives the camshaft by means of the toothed portions of belt 52. In addition, the water pump and fan are driven through their engagement with the grooved back of belt 52. Proper tension of the drive belt is maintained through manual lateral adjustment of the position of the water pump on the engine cylinder block in the manner previously indicated. The amount of tension may be selected to drive the water pump and fan at desired normal operating speeds but to permit the belt to slip under extreme loads such as may be caused by fast engine accelerations when the belt loadings might otherwise become excessive.

While the invention has been described by means of a specific embodiment, it should be understood that numerous changes could be made within the scope of the inventive concepts disclosed.

Claims

I claim:

1. An internal combustion engine of the type having a cylinder block mounting a crankshaft and an overhead camshaft for rotation on coplanar axes, said block containing a coolant cavity for the circulation of cooling fluid therethrough, said engine including

a toothed pulley mounted on said crankshaft at one end of said block

a second toothed pulley mounted on said camshaft and aligned with said first toothed pulley,

a water pump mounted on said one end of said block and arranged to deliver cooling fluid into said coolant cavity, said water pump having a drive pulley including a plurality of annular ridges and grooves and disposed generally intermediate and in alignment with said first and second toothed pulleys, the position on said block of said water pump and grooved pulley being adjustable to a limited extend in a direction generally transverse to the plane of said crankshaft and camshaft axes and

a drive belt having a toothed interior surface in driving engagement with said first and second toothed pulleys and an exterior surface having longitudinal ridges and grooves mating with the ridges and grooves of said water pump drive pulley and in driving engagement therewith, whereby said camshaft is positively driven by said drive belt, said water pump is nonpositively driven by said drive belt and the tension on said belt may be adjusted by lateral adjustment of the position of said water pump on said block.

2. An internal combustion engine of the type having a cylinder block mounting a crankshaft and an overhead camshaft for rotation on coplanar axes, said block including a coolant cavity for the circulation of cooling liquid therethrough, said engine including

a first toothed pulley mounted on said crankshaft at one end of said block,

a second toothed pulley mounted on said camshaft and aligned with said first toothed pulley,

a water pump mounted on said one end of said block and having an impeller extending into said coolant cavity, said impeller being arranged to deliver cooling fluid directly into said coolant cavity, the position of said water pump on said block being adjustable to a limited extent in a direction generally transverse to the plane of said crankshaft and camshaft axes, clearance being provided within said cylinder block for the necessary lateral movement of said impeller on account of such adjustment,

a drive pulley carried on said water pump and drivably connected with said impeller, said drive pulley having a plurality of annular ridges and grooves and being disposed generally intermediate and in alignment with said first and second toothed pulleys,

a fan drivably secured to said drive pulley for rotation therewith, and

a drive belt having a toothed interior surface in driving engagement with said first and second toothed pulleys and an exterior surface having longitudinal ridges and grooves mating with the ridges and grooves of said water pump and fan drive pulley and in driving engagement therewith, whereby said camshaft is positively driven by said drive belt, said water pump and fan are nonpositively driven by said drive belt and the tension on said drive belt may be adjusted by lateral adjustment of the position of said water pump on said block.