DE102005056198A1 - Belt drive for propelling cam shaft of internal combustion engine, has propelling wheel whose radius, depending upon its angle of rotation, is changed such that intake speed of traction mechanism on propelled wheel is constant - Google Patents

Abstract

Belt drive has a propelling wheel. The radius of a propelled wheel (11), depending upon its angle of rotation, is changed in such a way that an intake speed (vE) of traction mechanism (9) on the propelled wheel or delivery speed (vA) of traction mechanism from propelled wheel (12) is constant. An independent claim is included for the internal combustion engine.

Description

The The invention relates to a belt drive, in particular for driving of at least one camshaft of an internal combustion engine, with a driving wheel, at least one non-round driven wheel on this is a periodically oscillating, rotational angle and speed the driven wheel dependent Torque acts as well as with a traction device. The invention relates further an internal combustion engine with at least one camshaft, from his crankshaft over one such belt drive is driven.

If one of the actuated by a camshaft of an internal combustion engine valves pressed against the force of its valve spring in the open position, the camshaft is slightly slowed down, because the valve has a short-term, the rotation of the camshaft counteracting torque on the camshaft exercised becomes. Upon subsequent closing the valve also becomes a short-term torque from the valve exerted on the camshaft, however, has an opposite sign and in the direction of rotation the camshaft acts so that there is a slight acceleration of the Camshaft causes. These torques act on all, with the camshaft engaged valves of the internal combustion engine, so that the camshaft periodically oscillating speed fluctuations subject to its size and phase depends on the number, arrangement and design of the valve trains. These fluctuations of the speed thus occur in a rotationally fixed or over a camshaft Drehversteller connected to the camshaft Gear on that over a belt drive, for example a chain or toothed belt drive, from a drive gear on the crankshaft of the internal combustion engine is driven. The speed fluctuations in the driven gear in turn lead to fluctuating inlet and outlet speeds of the traction device, i.e. the chain or the toothed belt of the belt drive, so that in the traction means due to the speed changes load changes, the is called an alternating stretch and relaxation, as well as unwanted torsional vibrations the camshaft are caused. As a result of the load change is the wear of the Traction means accelerates and thereby reduces its useful life, especially when using toothed belt drives. In addition, will through constant Load changes in the traction means also consumes energy.

From the DE 195 20 508 A1 it is already known per se in a belt drive of the type mentioned for driving camshafts of an internal combustion engine to form out of alignment with the camshaft connected driven wheel of the belt drive to reduce torsional vibrations in the belt drive and to eliminate audible vibration noises.

outgoing This is the object of the invention, a belt drive or an internal combustion engine of the type mentioned in the effect to improve that reduces load changes and vibrations in the traction device which are generally due to periodically oscillating torques in the driven wheel of the belt drive and especially due to the torque fluctuations of the camshaft in the driven wheel a belt drive driving the belt drive caused become.

These Task is inventively characterized solved, a radius of the driven wheel depending on its rotation angle so changed is that an input speed of the traction means on the driven Wheel and / or an outlet speed of the traction device from the driven Wheel despite the speed fluctuations of the driven wheel or the camshaft are kept almost constant.

Of the Invention is based on the idea that periodically oscillating Torque due to a corresponding shape of the out-of-roundness of the driven Compensate for the speed of the traction means at the wheel Inlet point and / or at the outlet point of the driven wheel almost keep constant and thereby increase the smoothness of the traction means and reduce its load, which in terms of wear, acoustics, Durability and friction reduction brings benefits.

To For this purpose, the driven wheel is designed so that by the out-of-roundness conditional change its radius at the inlet point or at the outlet point of the traction device always counteracts the speed fluctuations of the shaft and this thus balances. In other words, the course of the radius of the driven Rades over its angle of rotation at the inlet point or at the outlet point of the traction device chosen so that it is in phases of acceleration of the driven wheel or the camshaft decreases due to the torque applied thereto, while he is in phases of delay the driven wheel or the camshaft as a result of acting thereon Torque increases, so that the speed of the traction means its entry point or exit point is made uniform.

A constant speed of the traction means is achieved when for the speed v _E at the inlet side and the speed v _A at the outlet side the relationship v A = v e = constant (1) applies. Since the speed v of the traction means on the driven wheel corresponding to the relationship v = r (φ) · ω (φ) (2) results, for example, applies at the inlet side or at the inlet point of the driven wheel: v e = r (φ) · ω (φ) = constant (3)

Thus, for a constant velocity v _E , the variations of r (φ) and ω (φ) must orderly equalize, that is, when the camshaft pushes the valve down and slows down, thus decreasing ω (φ), the radius r ( φ) increase synchronously at the entry point.

When using the belt drive according to the invention for driving a camshaft of an internal combustion engine, the design of the radius profile, for example, at the inlet point of the traction means on the rotationally fixed to the camshaft connected non-circular gear for the case of any torque curve is possible, in this case for r (φ) applies : r (φ) = [r 0 + r k1 cos (k1 · 2φ + α k1 ) + r k2 cos (k2 · 2φ + α k2 ) + ...] (4)

Correspondingly, for ω (φ): ω (φ) = [ω 0 + ω k1 cos (k1 * 2φ + β k1 ) + ω k2 cos (k2 · 2φ + β k2 ) + ...] (5)

For the oscillating torque applies there M (φ) = [M 0 + M k1 cos (k1 · 2φ + γ k1 ) + ω k2 cos (k2 · 2φ + γ k2 ) + ...] (6) where, in equations (4), (5) and (6), r _{0 is} the mean radius of the driven wheel where its average angular velocity and M _{0 is} the average torque applied to the driven wheel, k1, k2 ... the engine orders are to be controlled by balancing the vibrations on the driven wheel, α _k1 , α _k2 ... the phase angles of the harmonic oscillation of the radius r (φ) in the motor order k1, k2 ..., β _k1 , β _k2 . the phase angles of the harmonic oscillation of the angular velocity ω (φ) in the motor order k1, k2 ... and γ _k1 , γ _k2 ... the phase angles of the harmonic oscillation of the torque M (φ) in the motor order k1, k2 .. are each in the same coordinate system as φ.

The torque curve M (φ) of the driven wheel is determined by the number, arrangement and design of the valve trains of the camshaft and thus all coefficients in (6). Designable sizes are r _k and α _k , ie the size and phase of the out-of-roundness of the driven wheel in the considered engine orders k1, k2 .... These are inventively determined by a corresponding design of the out-of-roundness of the driven wheel so that cancel the oscillating terms in the product r (φ) · ω (φ) orderly and thus (3) is satisfied.

If the torque M consists only of a periodic component of the order k, it follows from the relationship M = θω., Where θ is the moment of inertia of the camshaft and ω. whose angular acceleration is, for the amplitude ω _{k of} the torsional vibration in engine order k, the relationship ω k = (1 / θω 0 ) ∫M k dφ = M k / 2ω 0 kθ (7) and for the phase β _k β k = 90 ° - γ k (8th) what used in equation (5) gives the relationship: ω (φ) = [ω 0 + (M k1 / K1 · 2ω 0 θ) sin (k1 · 2φ + γ k1 ) + + (M k2 / K2 * 2ω 0 θ) sin (k2 · 2φ + γ k2 ) + ...] (9) (3) can now be written as the product of (9) and (4). If the desired terms are to be properly eliminated, the following applies to the amplitude condition: r k = r 0 M k / 2kω 0 2 θ (10) and for the phase condition: α k = γ k + 90 ° (11)

If only the oscillations of an order are to be compensated, only one radius oscillation is superimposed on the mean radius r _{0 of} the driven wheel, for example in the case of order k1 with the profile r _k1 cos (k1 * 2φ + α _k1 ). However, the average radius r _{0 may} also be superimposed with several oscillations, as indicated above by equation (4). For example, in a V6 engine, engine orders k1 = 1.5 and k2 = 3.0 are important, while for other types and / or numbers of cylinders, other engine orders may be relevant, for example, k = 2.

in the The following is the invention with reference to an illustrated in the drawing embodiment explained in more detail. It demonstrate:

1 : A perspective view of a trained as a toothed belt belt drive between a crankshaft and two camshafts of an internal combustion engine;

2 a schematic view of parts of the belt drive;

3 a graph of the course of the valve lift of one of in 1 illustrated valves on the cam angle;

4 a graph of the curve of the camshaft torque over the same cam angle as in 3 ;

5 a graph of the radius profile of driven gears of the belt drive on the camshaft over the same cam angle as in 3 ;

6 a graph of the course of the angular velocity of driven gears of the belt drive on the camshaft over the same cam angle as in 3 ,

The in 1 only partially shown internal combustion engine 1 a motor vehicle comprises in a known manner with the piston 2 (only one shown) of the engine 1 connected crankshaft 3 and two camshafts 4 . 5 for controlling intake and exhaust valves 6 respectively. 7 the cylinder (not shown). To the two camshafts 4 . 5 in synchronization with the rotation of the crankshaft 3 It is between the crankshaft 3 and the camshafts 4 . 5 a toothed belt drive 8th intended. The toothed belt drive 8th includes a timing belt 9 that with a gear 10 on the crankshaft 3 a gear 11 on the camshaft 4 and a gear 12 on the camshaft 5 in meshing engagement and by a tensioning rail or a freewheeling tensioner 13 is tense. The gears 10 . 11 and 12 each have a spur toothing. The diameter or the number of teeth z of the gears 11 . 12 on the camshafts 4 . 5 is at the same pitch p twice the diameter or the number of teeth z of the gear 10 on the crankshaft 3 so that one turn of the camshafts 4 . 5 two revolutions of the crankshaft 3 equivalent.

The Indian 1 shown toothed belt drive 8th is shown only as an example and can except the two camshafts 4 . 5 drive even more waves, for example, control or balance shafts or a drive shaft of a cooling water pump of the engine 1 , which are not shown for the sake of simplicity. Next is the in 1 exemplified internal combustion engine 1 a four-cylinder in-line engine, while the invention will be described below in connection with a six-cylinder V-engine.

How best in 2 shown schematically, have the two camshafts 5 . 6 including the gears 11 . 12 in each case a moment of inertia θ1 or θ2 and must in operation against an acting on periodically oscillating torque M ₁ (n, φ) and M ₂ (n, φ) (in 2 and subsequently simplified in part as M ₁ (φ) and M ₂ (φ)) moving through the opening and closing operations of the respective camshaft 4 . 5 controlled valves 6 . 7 caused by the rotational speed n and the rotational angle (φ) of the camshaft 4 . 5 are dependent.

As a result of these oscillating torques M ₁ (φ) and M ₂ (φ), the camshafts are subject 4 . 5 and the rotatably connected with them gears 11 . 12 Speed fluctuations, wherein their angular velocities ω ₁ (φ) and ω ₂ (φ) as well as the torques M ₁ (φ) and M ₂ (φ) of the rotation angle (φ) of the respective camshaft 4 . 5 depend.

To avoid the speed fluctuations of the camshafts 4 . 5 on the timing belt 9 of the toothed belt drive 8th are transferred, the gears 11 and 12 the camshafts 4 . 5 in 2 out of round, with the variations of their radius r at the inlet point 14 of the toothed belt 9 on the gear 11 and at the exit point 15 of the toothed belt 9 from the gear 12 the speed fluctuations of the camshaft 4 respectively. 5 counteract and compensate for this. The compensation thus takes place during the configuration 2 at the entry point 14 of the gear 11 and at the exit point 15 of the gear 12 that is, at the end and at the beginning of a longer section of the timing belt 9 that is about the gear 10 on the crankshaft 3 extends. This is the out-of-roundness of the gears 11 and 12 designed so that the speed v _{E of} the timing belt 9 at the entry point 14 of the gear 11 and the velocity v _A at the exit point 15 of the gear 12 are constant and thus v _{E is} equal to v _A. This means that in phases of acceleration of the camshaft 4 . 5 when closing a valve 6 . 7 the radius r (φ) at the inlet point 14 or at the outlet point 15 decreases while in phases of deceleration of the camshaft 4 . 5 when opening a valve 6 . 7 at the entry point 14 and exit point 15 increases.

The out-of-roundness of the gears produced, for example, by wire erosion or by sintering 11 . 12 is in the range of a few percent of its diameter.

If the torques M ₁ (φ) and M ₂ (φ) have a sinusoidally oscillating course over the rotation angle φ and consist only of a periodic component of the motor order k, the course of the radius r (φ) is also at the entry point 14 or at the outlet point 15 sinusoidal, that is the gears 11 and 12 are ovals of the 2nd order, for those at the entry point 14 or at the outlet point 15 the following amplitude or phase conditions apply:
r _k = r ₀ M _k / 2kω ₀ ² θ amplitude condition
α _k = γ _k + 90 ° phase condition
where r _{0 is} the mean radius of the gear 11 respectively. 12 is where its mean angular velocity and M _k that on the gear 11 respectively. 12 acting torque for the motor order k, α _{k is} the phase angle of the harmonic of the radius r (φ) in the motor order k, and γ _{k is} the phase angle of the harmonic of the torque in the motor order k, respectively in the same coordinate system as φ.

As can be seen from a comparison of 3 and 4 can be inferred, the peak value of r _k is running with a phase of 90 ° / 2k above the peak value of _k M, while the maximum value of the radius (r _max in 2 ) coincides with the maximum value of the valve lift, as can be seen from a comparison of 3 and 5 results. The course of the radius r (φ) at the inlet point 14 or at the outlet point 15 and the course of the angular velocity .omega. (. phi.) balance properly as in FIGS 5 and 6 shown where r ₀ and where the mean radius of the gear 11 . 12 or indicate its mean angular velocity. In the 3 to 6 are the valve lift when opening a valve, the associated camshaft torque M (φ), the radius r (φ) at the inlet point 14 and the angular velocity ω (φ) for the camshaft 14 each applied over the cam angle.

If, for example, the vibration of the engine order k = 1.5 should be compensated in a 6-cylinder V-engine, results for the gear 11 . 12 a trio form, as in 2 exaggerated. For k = 3.0, the gear becomes 11 . 12 hexoval, ie with six peaks over the circumference.

For any given camshaft torque M ₁ (φ) or M ₂ (φ), k = 1.5 and k = 3.0, which are of particular importance in the case of 6-cylinder V-engines, can be used for the two aforementioned engine arrangements. the course of the radius at the entry point 14 or at the outlet point 15 generally expressed by the following relationship: r (φ) = [r 0 + r 1.5 cos (3φ + α 1.5 ) + r 3.0 cos (6φ + α 3.0 ) + ...]

Correspondingly, for ω (φ): ω (φ) = [ω 0 + ω 1.5 cos (3φ + β 1.5 ) + ω 3.0 cos (6φ + β 3.0 ) + ...] where, if necessary, further terms can be used which correspond to higher engine orders than k = 3.0.

1

internal combustion engine

2

piston

3

crankshaft

4

camshaft

5

camshaft

6

intake valves

7

exhaust

8th

toothed belt drive

9

toothed belt

10

gear crankshaft

11

gear camshaft

12

gear camshaft

13

idler

14

Inlet point gear 11

15

Outlet point gear 12

Claims (9)

Circumferential drive, in particular for driving a camshaft of an internal combustion engine, with a driving wheel, at least one non-round driven wheel, which is acted upon by a periodically oscillating, the rotational angle and the rotational speed of the driven wheel torque, and with a traction means, characterized in that a Radius (r) of the driven wheel ( 11 . 12 ) is changed in dependence on its angle of rotation (φ) such that an entry speed (v _E ) of the traction means ( 9 ) on the driven wheel ( 11 ) and / or an outlet speed (v _A ) of the traction means ( 9 ) of the driven wheel ( 12 ) is constant. Belt drive according to claim 1, characterized in that the radius r (φ) at the inlet point ( 14 ) of the traction means ( 9 ) on the driven wheel ( 11 ) and / or at the exit point ( 15 ) of the traction means ( 9 ) of the driven wheel ( 12 ) out of phase with the oscillating torque (M ₁ (n, φ), M ₂ (n, φ)). Belt drive according to claim 2, characterized in that the radius r (φ) of the driven wheel ( 11 . 12 ) with a phase shift of 90 degrees to the torque (M ₁ (n, φ), M ₂ (n, φ)). Belt drive according to one of the preceding claims, characterized in that for the radius r (φ) of the driven wheel ( 11 . 12 ) at the entry point ( 14 ) of the traction means ( 9 ) on the driven wheel ( 11 ) and / or at the exit point ( 15 ) of the traction means ( 9 ) of the driven wheel ( 12 ) the following condition applies: r k (φ) = [r 0 + r k1 cos (k1 · 2φ + α k1 ) + r k2 cos (k2 · 2φ + α k2 ) + ...] where r _{0 is} the mean radius of the driven wheel, where k1, k2 ... is the order of vibration of the driven wheel, and where α _k1 , α _k2 ... is the phase angle of the radius r (φ) in the order of oscillation k. Belt drive according to one of the preceding claims, characterized in that for the radius r (φ) of the driven wheel ( 11 . 12 ) at the entry point ( 14 ) of the traction means ( 9 ) on the driven wheel ( 11 ) and / or at the exit point ( 15 ) of the traction means ( 9 ) of the driven wheel ( 12 ) the following condition applies:

where r _{0 is} the mean radius of the driven wheel, where k is the vibration order to be compensated for the periodic oscillating vibration of the torque, where M _k (n, φ) is the periodic oscillating torque acting on the driven wheel in motor order k where wo is the mean Angular velocity of the driven wheel, and where θ is the mass moment of inertia of the driven wheel and of a shaft ( 4 . 5 ). Circumferential drive according to one of the preceding claims, characterized characterized in that it is a chain drive. Circumferential drive according to one of the preceding claims, characterized in that it comprises a toothed belt drive ( 8th ). Belt drive according to one of the preceding claims, characterized in that it comprises at least one camshaft ( 4 . 5 ) of an internal combustion engine ( 1 ) rotatably or via a camshaft Drehversteller with the driven wheel ( 11 . 12 ) connected is. Internal combustion engine, with at least one camshaft, characterized by a belt drive ( 8th ) according to one of the preceding claims.