GB2079375A

GB2079375A - Five-cylinder in line internal combustion engine with weight- balancing arrangement

Info

Publication number: GB2079375A
Application number: GB8121203A
Authority: GB
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1980-07-10
Filing date: 1981-07-09
Publication date: 1982-01-20
Also published as: DE3026079A1; IT1195044B; ATA292681A; FR2486588A1; JPS5740143A; IT8122846A0

Abstract

A crankshaft with 1-3-5-4-2 crank- displacement diagram has a parallel weight-balancing shaft means which rotates at the same speed as but oppositely to the crankshaft and has balance weights disposed in the regions of the ends of the crankshaft. The balance weights 13, 14 are secured, respectively, on two hollow coaxial shafts 11, 12 which are each mounted in two bearings 16, 17; 18, 19 on or in the crankcase, a driving wheel 21 being secured on one of the two shafts, which are interconnected by a hollow inserted shaft 20. Suitably, the shaft on which the driving wheel is secured is mounted with its balance weight in the timing case, while the other shaft is mounted in a crankcase compartment covered by the cylinder head. Alternatively Figure 3 (not shown) the shafts may be mounted in bearing caps for the crankshaft. <IMAGE>

Description

SPECIFICATION Five-cylinder in line internal combustion engine with weight-balancing arrangement This invention relates to a five-cylinder in line internal combustion engine of the kind comprising a crankshaft with a 1-3-5-4-2 crank-angle crankdisplacement diagram and, parallel to the crankshaft, weight-balancing shaft means which rotates at the same speed as but in the opposite direction to the crankshaft and of which the balance weights are disposed in the regions of the end planes of the crankshaft. In a known arrangement of this kind, disclosed in German Patent Specification 1 142 727, second-order mass moments which occur during operation of the engine are reduced substantially by specified crank-angle displacement. It is then possiblue to counterbalance first-order mass moments by means of a single balancing shaft.For this purpose, suitably, the balance weights are arranged in the region of the end planes of the crankshaft. The considerable distance between the balance weights results in adequate balancing moments even when the balance weights are small and therefore light. On the other hand, the long balancing shaft, which is subjected to high bending moments, is not easily supported in its bearings and requires additional expenditure of work to produce precisely aligned bearings.

The present invention seeks to support as well as possible the weights which serve to balance the first-order mass moments with little additional weight, so that these weights will maintain their precise position to the crankshaft axis under all conditions of operation.

In accordance with the invention, in an arrangement of the aforesaid kind, the balance weights are secured, respectively on two coaxial shafts which are doubly mounted on or in the crankcase, a driving wheel being secured on one of the said two shafts, which are connected to each other in rotationally fast manner by an insert shaft. In this manner a particularly rigid bearing arrangement can be achieved for the two balance weights on short shafts which are independent of one another. Slight deviations by the shafts, located at the opposite ends of the engine, from a common axis due to inaccuracies in production or occurring during operation of the engine may be compensated for by permitting a certain angular movement of the interconnecting shaft. In addition, thermal expansion in the axial direction may be counter-acted by virtue of the interconnecting shaft.

Because the interconnecting shaft serves only to transmit torque, it can be made relatively light.

In accordance with a further development of the invention, the shaft on which the driving wheel is secured may be mounted, together with the balance weight, in the timing case of the engine, so that a separate housing for these components is unnecessary. The bearings of the shaft can be mounted advantageously in opposite walls of the narrow timing case. In addition, with this arrangement, the shaft can be driven directly by the timing chain of the engine.

The shaft on which only a balance weight is secured may be mounted on a crankcase compartment which is covered above by the cylinder head.

This short, shaft can thus be properly mounted in rigid compartment walls located close together. A separate cap or cover is not required.

In another advantageous embodiment of the invention, the two balance-weight shafts may each be mounted in a bearing cap for the crankshaft. This arrangement, utilising transverse walls which serve to support the crankshaft does not require substantial modification of the crankcase and also permits subsequent installation of the balance weights.

The balance-weight shafts and interconnecting shaft may be hollow shafts. This results in the light construction and permits lubricating oil to be supplied in simple manner to the shaft bearing through the interiors of the shafts. Consequently additional channels through the case can be avoided.

Embodiments of the invention by way of example will now be more fully described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through the bearing arrangement and driving means for balance weights of an internal combustion engine, Figure 2 is a diagrammatic view of driving means in this engine, and Figure 3 is a longitudinal section through the bearing arrangement and balance-weight driving means of another engine.

The weight-balancing arrangement shown in Figure 1 of a five-cylinder in line engine whose crankshaft has a 1-3-5-4-2 crank-angle displacement diagram comprises balance weights 13 and 14which are non-rotatably mounted respectively on short coaxial shafts 11 and 12 and are offset by 180 in relation to each other. The ends of the two shafts 11 and 12 are mounted on or, as shown, in the crankcase 15 in two sliding-contact bearings 16,17 and 18, 19 respectively, and the said two shafts are inter-connected in rotationally fast manner by an inserted shaft 20. A sprocket wheel 21, which is mounted in rotationally fast manner on the shaft 11 beside the balance weight 13, serves to drive the weights 13 and 14.

The weight 13 and the wheel 21 are housed in the timing case 22 of the engine, which case is bounded in the region of the weight 13 by an end wall 23 and further wall portions of the crank-case 15 and by parts of the cylinder head 24 and by a cover 25. The bearing 17 is disposed in the wall 23 and the bearing 16 in the cover 25. By removing the cover 25, the shaft 11 can be readily dismounted together with the weight 13 and wheel 21.

The weight 14 is arranged in a cavity or compartment 26 in or on the other end wall 27 of the crankcase 15. The cavity 26 is closed at the top by a concave wall section 28 of the cylinder head 24. The sliding-contact bearings 18 and 19 are disposed, respectively, in the walls 29 and 30 of the cavity. A boss 31 for the bearing 19 is sealed on the outside by acap32.

Because the two balance weights 13 and 14 are mounted on or in the crankcase 15, the forces developed and acting on the bearings 16 to 19 are transmitted directly into the crankcase 15.

The shaft 20 extends with clearance through a bore 33 in the crankcase 15. Both ends of this shaft are provided with external teeth or serrations 34 which engage in complementary internal formations 35 at the inner ends of the shafts 11 and 12. This arrangement permits of a certain angular movement of the shaft 20 so as to compensate for relatively small deviations from a common central axis by the shafts 11 and 12. The arrangement may also be made such that the shaft connections permit compensation for the effects of thermal expansion.

Lubricating oil for the bearings 16 to 19 of the shafts 11 and 12 is supplied under pressure through a channel 36 in the wall 23. The interior of the bearing 17 is directly connected to the channel 36 by a bore 37. For supplying oil to the remaining bearings 16,18 and 19, the shafts 11 and 12 and the connecting shaft 20 are designed as hollow shafts having axal ducts 38,39 and 40 respectively. The oil passes through an annular groove 41 and transverse bore 42 in the shaft 11 into and through the duct 38 and, from the latter, is fed through the duct 40 in the shaft 20 to the duct 39 in the shaft 12. Transverse bores 43 in the shafts 11 and 12 serve to supply oil to the bearings 18 and 19. The shafts 11 and 12 are tightly sealed at their outer ends by covers 44.

O-rings 46 fitted in annular grooves 45 in the shaft 20 afford seals, in the area of the serrations 34 and 35, between the shaft 20 and the shafts 11 and 12.

As shown in Figure 2, the driving means housed in the timing case 22 of the engine consists essentially of a sprocket wheel 48 which is mounted on the engine crankshaft 47 and which, by the inside 49 of a double roller chain 50, drives sprocket wheels 51 and 52 mounted on the camshaft 53 of the engine and/or on the shaft 54 of an additional unit, for example a fuel-injection pump. In addition, on the outside 55, the chain 50 drives the sprocket wheel 21 on the shaft 11 which, consequently, rotates in the opposite direction to the wheel 48 on the crankshaft 47. The directions of rotation of the wheels 48,51,52 and 21 are indicated in the drawing by arrows. The shaft 11 and the crankshaft 47 rotate at the same speed because the wheels 21 and 48 have the same diameter.The weights 13 and 14 on the shaft 11 and on the shaft 12, which is driven by way of the interconnecting shaft 20, thus rotate at the same speed as and in the opposite direction to the crankshaft 47. A tensioning bar or rail 56 is provided for the chain 50. Instead of disposing the wheel 21 on the shaft 11 between the wheels 51 and 52, as shown in Figure 2, it may be disposed in some other position atwhich it is engaged by the outside of the chain 50. Instead of a chain drive, a toothed-belt drive may be used to drive the shafts 11 and 12.

In the arrangement shown in Figure 3, the balance weights 57 and 58, which are offset by 180 in relation to each other and which have equal unbalanced masses, are again mounted on short coaxial shafts, 59 and 60 respectively, which are connected to each other in rotationally fast manner by an insert shaft 61 provided with serrations at both ends. The ends of the shafts 59 and 60 are mounted in sliding-contact bearings, 62, 63 and 64, 65 respectively, which, in contrast with the preceding example, are arranged, respectively, in the bearing caps 66 and 67 for the front bearing 68 and the rear bearing 69 for the crankshaft 70 of the engine.

Cavities 71 and 72 in the caps 66 and 67 permit the rotation of the balance weights, 57 and 58 respectively, each of which extends, when in its lower position into the oil sump of the engine.

Atoothed wheel 73 acting as a driving wheel is mounted on the shaft 59 beside the balance weight 57. Mounted in the cap 66, in a sliding-contact bearing 74, is a stepped shaft 75 with a central section 76 which has a larger diameter than an outer section 77 and an inner section 78. Mounted on the section 78 which projects into the cavity 71 is a toothed wheel 79 which meshes with the toothed wheel 73, of equal diameter, on the shaft 59.

Mounted on the outer section 77 of the shaft 75 is a sprocket wheel 80 which is connected by a chain (not shown) to a sprocket wheel of equal size mounted on the crankshaft 70. The balance weights 57 and 58 are driven, through the sprocket wheel 80 and the pair of toothed wheels 79/73, which acts as a rotationreversing gear, at the same speed as but in the opposite direction of rotation to the crankshaft 70.

Claims

1. A five-cylinder in line internal combustion engine comprising a crankshaft with 1-3-5-4-2 crankangle crank-displacement diagram and, parallel to the crankshaft, weight-balancing shaft means which rotates at the same speed as but in the opposite direction to the crankshaft and of which the balance weights are disposed in the regions of the end planes of the crankshaft, the balance weights being secured, respectively, on two coaxial shafts which are doubly mounted on or in the crankcase, a driving wheel being secured on one of the said two shafts, which are connected to each other in rotationally fast manner by an insert shaft.

2. An engine according to Claim 1,wherein the said shaft on which the driving wheel is secured is mounted with its balance weight in the timing case of the engine.

3. An engine according to Claim 1 or 2, wherein the said shaft on which only a balance weight is secured is mounted in a crankcase compartment, covered above by the cylinder head of the engine.

4. An engine according to Claim 1, wherein the - said two balance-weight shafts are mounted, respectively, in bearing caps for the crankshaft of the engine.

5. An engine according to any one of the preceding claims, wherein the balance-weight shafts and the shaft connecting them are hollow shafts.

6. An internal combustion engine with balancing weights provided substantially in the manner described with reference to Figures 1 and 2 orto Figure 3 of the accompanying drawings.