GB2294994A

GB2294994A - A reciprocating-piston internal combustion engine with torsional vibration balancing

Info

Publication number: GB2294994A
Application number: GB9522212A
Authority: GB
Inventors: Dirk Petersen
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1994-11-11
Filing date: 1995-10-31
Publication date: 1996-05-15
Anticipated expiration: 2015-10-31
Also published as: FR2726876B1; FR2726876A1; GB2294994B; DE19540765B4; GB9522212D0; DE19540765A1

Abstract

A reciprocating-piston internal combustion engine has for the purpose of torsional vibration balancing, a balancer shaft (6) which is driven by the crankshaft (2) and is of two-part design. An input part (6) is connected by means of a universal joint (7) bent through a bend angle ( alpha ) to an output part (9) which carries a balance weight (8). The non-uniform rotational excitation by the reciprocating-piston internal combustion engine (1) is transformed into a uniform rotation at the output part (9) as a function of the bend angle ( alpha ). <IMAGE>

Description

DESCRIPTION A RECIPROCATING-PISTON INTERNAL COMBUSTION ENGINE WITH TORSIONAL VIBRATION BALANCING The present invention relates to a reciprocatingpiston internal combustion engine with torsional vibration balancing.

In the case of reciprocating-piston internal combustion engines with a certain cylinder arrangement, for example in the case of 3-cylinder or 5-cylinder in-line internal combustion engines, torsional vibrations resulting essentially from gas forces and having a rotational non-uniformity of the 1,5the 3rd, 4.5th ... order about the longitudinal axis of the crankshaft occur. These excite pronounced vibrations in the internal combustion engine, particularly at idle or in the engine speed range close to idle and the said vibrations are transmitted to the frame of the internal combustion engine via the internal combustion engine mounts.

In the case of internal combustion engines of this kind installed in motor vehicles, especially diesel internal combustion engines, such vibrations should be reduced to a minimum for reasons of comfort.

DE-41 19 065 Al has disclosed a reciprocatingpiston internal combustion engine of the generic type with torsional vibration balancing, the engine having, to compensate the alternating torques, a balancer shaft with a moment of inertia which is approximately half as great as the moment of inertia of the centrifugal masses at the crankshaft.

US Patent 4,300,649 discloses a motor vehicle with an internal combustion engine and a gearbox, each of these being held independently as a separate unit in mountings and being connected in terms of drive via at least one cardan joint.

The aim of the present invention is to provide a reciprocating-piston internal combustion engine with torsional vibration balancing which largely eliminates the torsional vibrations of the 1,5to 3rd, 4.5th etc.

order about the axis of rotation of the crankshaft arising principally from gas forces.

According to the present invention there is provided a reciprocating-piston internal combustion engine comprising a balancer shaft for torsional vibration balancing, the balancer shaft being connected at its input end to the crankshaft of the internal combustion engine via at least one gear stage, the balancer shaft being split into two parts, an input part carrying the input end and being connected by means of a universal joint, at the bend angle (a) of the latter, to an output part which carries a balance weight, the gear stage having a transmission ratio such that the non-uniform rotational excitation transmitted by the crankshaft to the input part takes the form of a uniform rotary motion of the output part by virtue of the degree of non-uniformity of the universal joint.

The present invention exploits the essentially known behaviour of a universal joint. The uniform angular velocity at the input side of a universal joint is usually converted into a second angular velocity of the output pulsating at twice the angular velocity, this second angular velocity depending essentially on the bend angle of the universal joint.

The degree of non-uniformity of a universal joint is the product of the tangent and sine of the bend angle.

It is here that the present invention intervenes, reversing the customary application such that the universal joint is excited in a non-uniform manner by the internal combustion engine and the transmission behaviour of the universal joint is used to achieve a uniform rotary motion on its output side. This is achieved by means of a balancer shaft which is divided into an input part and an output part, the input part being driven by the crankshaft by means of a gear stage, and being connected to the output part by the universal joint, said output part carrying a balance weight, at a bend angle by virtue of the universal joint, The gear stage transforms the order of the vibration of the internal combustion engine to the level of the order of vibration produced by the universal joint due to the degree of non-uniformity of the latter.

The universal joint produces a second-order opposing vibration, thus making is possible, for example, to eliminate the vibrations of the 1.5th order produced in the case of a 3-cylinder in-line engine by means of a transmission ratio of 1 to 0.75.

As an advantageous refinement of the present invention, the balance weight arranged on the output part of the balancer shaft can be formed by the flywheel of the internal combustion engine. This can be followed directly by a clutch arranged between the internal combustion engine and a gearbox arranged on the output side.

It is likewise possible to arranged the torsional vibration balancing means as a separate unit on the side of the internal combustion engine remote from the gearbox.

Particularly in the case of diesel internal combustion engines, an optimum setting of the bend angle, once found, can be left unaltered since, here, the excitation results from largely load-independent gas forces.

For more refined tuning or different types of internal combustion engine, load dependence can be allowed for by control, the vibrations of the unit/units being measured and fed to an adjusting device which, by means of a feedback control circuit, adjusts the bend angle to give a minimum of vibration for the internal combustion engine.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a first embodiment of the present invention with a balancer shaft arranged between an internal combustion engine and a gearbox; and Fig. 2 shows a second embodiment of the present invention with a separately arranged device for torsional vibration balancing.

At the end of a crankshaft 2, a 3-cylinder inline internal combustion engine denoted overall by 1 has one gear wheel 3 of a gear stage 4 which drives an input part 5 of a balancer shaft 6 split into two parts.

The input part 5 is connected to the output part 9 of the balancer shaft 6, said output part 9 carrying a balance weight 8, by means of a universal joint 7, the universal joint 7 having a bend angle a.

According to a first embodiment of the invention, the balancer shaft 6 is arranged between the internal combustion engine 1 and a gearbox, denoted overall by 10, arranged on its output side.

In a second embodiment, the gear stage 4 is arranged on the opposite side of the internal combustion engine 1 from the gearbox 10. The output part 9 carrying the balance weight 8 is here mounted in a housing 13.

Both the internal combustion engine 1 and the gearbox 10 are held in unit bearings 14. Torsional vibration balancing is accomplished as follows.

The non-uniform rotary excitation by the internal combustion engine 1 is transmitted to the input part 5 as a non-uniform angular velocity W1 by means of the crankshaft 2 and the gear stage 4. The universal joint 7 transforms this angular velocity W1 into an output angular velocity W2 pulsating at twice the angular velocity. This second angular velocity W2 is dependent on the bend angle a and on the current rotational angle of the input part 5. The degree of non-uniformity U of the universal joint 7 is the product of tan a and sine a. The universal joint 7 produces an opposing second-order vibration, but in the case of the 3-cylinder reciprocating-piston internal combustion engine 1 it is the vibration with the greatest disturbing amplitude, that of the 1.5th order, which needs to be eliminated.It is here that the gear stage 4 intervenes with a transmission ratio of 1 to 0.75, transforming the 1.5th order vibration into a second order vibration.

By optimization, the bend angle a and the position of the universal-joint axis 15 can be configured in such a way that a virtually uniform rotary motion is present on the output side of the universal joint 7.

As already explained, the bend angle a can be made variable to provide improved compensation of the torsional vibrations. For this purpose, the housing 13 is, according to Figure 2, held so as to be pivotable about the universal-joint axis 15. An adjusting device 16 arranged on the internal combustion engine 1 has a measuring element for torsional vibrations generated in the internal combustion engine and an angle-setting element connected to its output, which acts on the housing 13 via a connecting rod 17.

Variation of the bend angle a can likewise be employed in the case of the first embodiment in accordance with Figure 1. The drive unit shown there, formed by the internal combustion engine 1 and the gearbox 10, drives wheels 19 of a motqr vehicle (not shown) by means of output shafts 18. The adjusting device 16 is here mounted on the motor vehicle and pivots the internal combustion engine 1 about the universal-joint axis 15 by means of a connecting rod.

Claims

1. A reciprocating-piston internal combustion engine comprising a balancer shaft for torsional vibration balancing, the balancer shaft being connected at its input end to the crankshaft of the internal combustion engine via at least one gear stage, the balancer shaft being split into two parts, an input part carrying the input end and being connected by means of a universal joint, at the bend angle (a) of the latter, to an output part which carries a balancer weight, the gear stage having a transmission ratio such that the non-uniform rotational excitation transmitted by the crankshaft to the input part takes the form of a uniform rotary motion of the output part by virtue of the degree of non-uniformity of the universal joint.

2. An internal combustion engine as claimed in claim 1, in which the transmission ratio has a value smaller than one and greater than 0.5.

3. An internal combustion engine as claimed in claim 2, in which the transmission ratio has a value of 0.75.

4. An internal combustion engine as claimed in claim 1, in which the balance weight is formed by a flywheel of the internal combustion engine.

5. An internal combustion engine as claimed in claim 4, in which the balancer shaft is arranged between the reciprocating-piston internal combustion engine and a gearbox connected to the output of the latter, and the flywheel drives a clutch on its output side.

6. An internal combustion engine as claimed in claim 1, in which at its end opposite the input end, the reciprocating-piston internal combustion engine is connected rigidly to an output-side gearbox, and the output part projects freely from the universal joint.

7. An internal combustion engine as claimed in claim 5 or 6, in which the bend angle can be adjusted during the operation of the reciprocating-piston internal combustion engine by means of an adjusting device containing a measuring element for torsional vibrations generated in the reciprocating-piston internal combustion engine and an angle-setting element connected to its output.

8. An internal combustion engine as claimed in claim 7, in which the reciprocating-piston internal combustion engine is provided as the drive unit of a motor vehicle and the adjusting device is held in the latter on the body, and this adjusting device acts on the reciprocating-piston internal combustion engine to pivot the latter about the universal-joint axis in order to adjust the bend angle.

9. An internal combustion engine as claimed in claim 7, in which the adjusting device is arranged on the reciprocating-piston internal combustion engine and acts on a housing supporting the input part in order to adjust the bend angle.

10. A reciprocating-piston internal combustion engine constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.