MODULAR CONSTRUCTION CAMSHAFT ADJUSTER WITH A CHAIN OR BELT WHEEL

Abstract

A modular construction camshaft adjuster for the camshaft drive of an internal combustion engine with a chain or belt wheel, which has at least one wheel rim facing radially outwards with tooth engagement recesses, an annular wheel plate around a central circular opening and an essentially cylindrical wheel wall with a wall thickness, projecting in an axial direction from the annular wheel plate, such that the wheel wall and the wheel plate together form a cup shape. The minimum wall thickness of the essentially cylindrical wheel wall beneath the at least one wheel is equal to half the tooth engagement recess and the cup-shaped chain or belt wheel is made from a lightweight material.

Description

FIELD OF THE INVENTION

The invention relates to a modular construction camshaft adjuster with a chain or belt wheel for the camshaft drive of an internal combustion engine, having the features of the preamble of claim 1.

Camshafts of internal combustion engines are generally driven by crankshafts via a chain or a toothed belt and are continuously adjusted within a closed control loop during this process, with typical adjustment ranges being between 40 and 60° of crank angle. Crank angles to be set are stored in characteristic maps. Adjustments are made hydraulically, for example, with the supply coming from the engine oil circuit via an electrically actuated control valve, and they allow optimized valve timings using the engine load and speed as parameters. Depending on the engine concept and the number of adjusters, it is thus possible to achieve a significant reduction in fuel consumption and exhaust gas emissions and an increase in power and torque.

US 2005/0051121 A1 has disclosed a camshaft adjuster with a chain or belt wheel for a camshaft drive of an internal combustion engine. The housing of the camshaft adjuster, including a profiled groove, is composed of aluminum or magnesium. The profiled groove accommodates the chain or belt wheel, which is manufactured from steel. The profiled groove complicates the manufacture of the housing of the camshaft adjuster, and the mounting of the chain or belt wheel on the housing is an involved process.

DE 103 03 991 A1 has disclosed a modular construction camshaft adjuster for the camshaft drive of an internal combustion engine with a chain or belt wheel, which has a radially outwardly oriented wheel rim with a tooth engagement depth Z. The chain or belt wheel is provided with an annular wheel bed around a central circular opening. A substantially cylindrical wheel wall projects with a wall thickness X in an axial direction from the annular wheel bed, with the result that the wheel wall and the wheel bed together form a cup shape, the wall thickness X of the substantially cylindrical wheel wall beneath the single wheel rim being a multiple of the tooth engagement depth Z, giving enough room for radially distributed bores in the substantially cylindrical wheel wall to allow coaxial mounting of the chain or belt wheel on a stator of the camshaft adjuster (see FIG. 2, in the place cited). The effect of the solid wall thickness X of the cylindrical wheel wall in DE 103 03 991 A1 is to increase the weight of the chain or belt wheels and hence to disadvantageously increase the overall mass of the camshaft adjuster and the chain or belt wheels.

Cup-shaped chain or belt wheels of low mass have a correspondingly limited stability and are deformed when subjected to high loads by driving chains or belts, something that can compromise the camshaft drive and thus lead to engine damage.

It is an object of the invention to provide a modular construction camshaft adjuster with a chain or belt wheel for the camshaft drive of an internal combustion engine, having an improved load capacity combined with a low overall mass.

The solution is provided by a modular construction camshaft adjuster with a chain or belt wheel for the camshaft drive of an internal combustion engine, having the features of claim 1. Advantageous embodiments are described in the subclaims.

According to the invention, a modular construction camshaft adjuster for a camshaft drive of an internal combustion engine has a chain or belt wheel with an annular wheel bed around a central circular opening for accommodating a camshaft, on which the chain or belt wheel is mounted by means of a rotor of the camshaft adjuster. At least one wheel rim with tooth engagement depths Z is provided in a radially outward orientation on the chain or belt wheel. A substantially cylindrical wheel wall with a minimum wall thickness X projects freely in an axial direction from the annular wheel bed, at the outer periphery of the latter, and together with the wheel bed forms a cup shape, the minimum wall thickness X of the wheel wall projecting from the annular wheel bed, beneath the at least one wheel rim, being equal to half the tooth engagement depth Z in order to ensure an adequate load capacity. At least one wheel rim is arranged in the projecting region of the wheel wall. According to the invention, the cup-shaped chain or belt wheel is manufactured from a lightweight material such as aluminum in order to ensure a low weight. Radially distributed bores in the annular wheel bed serve to allow coaxial mounting of the chain or belt wheel on a stator of the camshaft adjuster. This also advantageously reduces the particularly large distortion of cup-shaped chain or belt wheels after heat treatment.

According to an advantageous embodiment of the invention, the cup-shaped chain or belt wheel is provided with at least one substantially radially oriented reinforcing rib extending from the annular wheel bed to the wheel wall to allow weight-optimized reinforcement at the periphery of the cup-shaped chain or belt wheel.

According to a further advantageous embodiment of the invention, a reinforcement is provided all the way around, extending from the annular wheel bed to the substantially frustoconical wheel wall, for the purpose of uniform reinforcement at the periphery of the cup-shaped chain or belt wheel.

According to a further advantageous embodiment of the invention, the wheel wall projects from the outer edge of that side of the camshaft adjuster which faces away from the camshaft adjuster.

According to a further advantageous embodiment of the invention, the reinforcing ribs are constructed at an angle, in a stepped manner or with rounded portions to optimize reinforcement in the given design circumstances and load conditions.

The invention is explained below with reference to preferred illustrative embodiments. In the drawing:

FIG. 1: shows a cup-shaped chain wheel according to the invention;

FIG. 2: shows an alternative cup-shaped chain wheel according to the invention; and

FIG. 3: shows a further alternative cup-shaped chain wheel according to the invention.

FIG. 1: a cup-shaped chain wheel 1 made from a lightweight material such as aluminum is mounted coaxially on a camshaft adjuster 2, manufactured in modular form from steel, of an internal combustion engine (not shown), with bolts 3 distributed uniformly in the radial direction passing through an annular wheel bed 4 of the cup-shaped chain wheel 1, a stator 5 and a front cover 6 of the camshaft adjuster 2. A central circular opening 7 in the annular wheel bed 4 serves to accommodate a camshaft (not shown), on which the chain wheel 1 is rotatably mounted by way of the camshaft adjuster 2. A bearing 8 for the camshaft in a rotor 9 of the camshaft adjuster 2 has lubricant openings 10.

A wheel wall 11 of the cup-shaped chain wheel 1, said wheel wall being substantially cylindrical from the outside, projects substantially in an axial direction—away from the camshaft adjuster 2—at the outer periphery of the annular wheel bed 4. Two wheel rims 12 oriented radially outward, each with tooth engagement depths Z, are provided in the projecting region of the wheel wall 11, which has a wall thickness X. Respective chains (not shown), by means of which the camshaft is driven by a crankshaft (not shown), run over each of the wheel rims 12. The wheel wall 11 of the cup-shaped chain wheel 1 projects from the periphery of the annular wheel bed 4 with a minimum wall thickness X which is substantially constant over its entire axial extent and which is greater than half the tooth engagement depth Z. The axial extent of the wheel wall 11 is greater than the width of 2 wheel rims 12.

FIG. 2: corresponding features are indicated by the reference signs from FIG. 1. At its free end 13, the wheel wall 11 of the cup-shaped aluminum chain wheel 1 which faces away from the camshaft adjuster 2 has a minimum wall thickness X which is greater than the tooth engagement depth Z and which increases in a linear manner radially inward from the free end 13 as far as the annular wheel bed 4 to give a substantially frustoconical reinforcement 14 for the wheel bed 4 and the wheel wall 11 all the way around the periphery thereof, recesses being provided in the reinforcement 14 for the heads of the bolts 3.

FIG. 3: corresponding features are indicated by the reference signs from FIGS. 1 and 2. At its free end 13, the cylindrical wheel wall 11 of the cup-shaped aluminum chain wheel 1 has a minimum wall thickness X which is somewhat greater than the tooth engagement depth Z. Reinforcing ribs 15, which are distributed uniformly over the periphery and the wall thickness of which initially increases in a quasi-linear manner over as much as approximately ⅓ of the total axial extent of the wheel wall 11 to about twice the tooth engagement depth Z, extend radially inward toward the wheel bed 4 from the free end 13 of the cylindrical wheel wall 11. The wall thickness of the reinforcing ribs 15 then increases with a radial offset 16 to about three times the tooth engagement depth Z as far as the annular wheel bed 4. The heads of the bolts 3 are provided between the ribs 15.

The cylindrical wheel wall 11 with a minimum wall thickness X projects freely in an axial direction from the annular wheel bed 4, at the outer periphery of the latter, by an amount which is more than the width of a wheel rim 12, the width of a wheel rim 12 being at least 5 mm.

Claims

1. A modular construction camshaft adjuster for a camshaft drive am internal combustion engine with a chain or belt wheel, comprising:

at least one radially outwardly oriented wheel rim with a tooth engagement depth Z;

an annular wheel bed around a central circular opening; and

a substantially cylindrical wheel wall with a wall thickness, which projects substantially in an axial direction from the annular wheel bed, with the result that the substantially cylindrical wheel wall and the wheel bed form a cup shape, a minimum wall thickness of the substantially cylindrical wheel wall beneath the at least one wheel rim being equal to half the tooth engagement depth, wherein the cup-shaped chain or belt wheel is manufactured from a lightweight material and is provided with radially distributed bores in the annular wheel bed for the purpose of coaxial mounting on a stator.

2. The camshaft adjuster of claim 1, wherein at least one substantially radially oriented reinforcing rib extending from the annular wheel bed to the substantially cylindrical wheel wall is provided.

3. The camshaft adjuster of claim 1, wherein a reinforcement is provided at the periphery, extending from the annular wheel bed the wheel wall.

4. The camshaft adjuster of claim 1, wherein the wheel wall of the cup-shaped chain or belt wheel projects from an outer edge of a side of the annular wheel bed which faces away from the camshaft adjuster.

5. The camshaft adjuster of claim 1, wherein the at least one wheel rim is arranged in the projecting region of the wheel wall.

6. The camshaft adjuster of claim 2, wherein the reinforcing ribs are constructed at an angle, in a stepped manner or with rounded portions.