GB2117837A

GB2117837A - Internal combustion engine with mass balancing

Info

Publication number: GB2117837A
Application number: GB08233917A
Authority: GB
Inventors: Manfred Abts; Herbert Kaniut
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1982-03-30
Filing date: 1982-11-29
Publication date: 1983-10-19
Also published as: FR2524594A1; DE3211655A1; GB2117837B; JPS58180854A; FR2524594B1

Abstract

A four-cylinder in-line engine comprises two balancer shafts 12, 24 provided with balancing weights and disposed at different levels on both sides of the crankshaft 2 and parallel thereto. The upper balance shaft is driven by way of a chain drive 7 in the same direction of rotation as the crankshaft 2 and the lower balance shaft is driven via a pair of gearwheels 27, 29 in the opposite direction at double the rotational speed of the crankshaft. Moreover, the chain drive 7 drives a lubricating-oil pump 10 on the front end of the engine, while the gearwheels 27 and 29 are disposed directly in the transverse median plane of the engine. <IMAGE>

Description

SPECIFICATION Internal combustion engine with mass balancing The invention relates to an internal combustion engine with mass balancing, described in the preamble of Patent Claim 1.

The German Offenlegungsschriften (Laid-Open Specifications) 24 55 667, 25 08 325 and 25 31 239 disclose internal combustion engines with mass balancing of the second order which, in the case of a four-cylinder in-line engine, comprises two balancer shafts which are provided with balancing weights and are disposed at different levels on both sides of the crankshaft parallel thereto and the upper one of which is driven by way of a chain drive in the same direction of rotation as the crankshaft and the lower one of which is driven through the intermediary of a pair of gearwheels in the opposite direction of rotation at double the rotational speed.

In this connection the first of the abovementioned Offenlegungsschriften discloses the theoretical basis for determining the position and masses of the balancer shafts, while the other two Offenlegungsschriften describe drive and bearing arrangements for the two balancer shafts.

In the case of these known internal combustion engines the two balancer shafts are driven by way of a chain drive disposed on the front end of the engine through the intermediary of a pair of gearwheels. The balancer shafts are mounted by way of a bearing in the front end of the engine and by way of a bearing in a transverse median plane of the engine, the balancing weights formed integrally with the balancer shafts being arranged on both sides of the latter bearing.

This known mass balancing has the disadvantage that the two balancer shafts are of substantial length and their bearing in the transverse median plane of the engine must have a diameter of such magnitude that they may be fitted, by axial insertion from the front end of the engine, in the tubular blind-end spaces formed in the engine block. In this way the weight of the internal combustion engine is increased on the one hand and an undesirably high bearing friction occurs in the large bearings.

Internal combustion engines with mass balancing of the second order are known from the German Offenlegungsschriften 2916181 and 29 35 384, in which the two balancer shafts are driven approximately in the transverse median plane of the engine by way of a chain or gearwheel drive. In this case the driven sprocket wheel or gearwheel is disposed on a crank web of the crankshaft of the motor. In this connection the balancer shafts, which are kept very short, are mounted in one case on a bearing cap - made suitably enlarged -- of a crankshaft bearing and in the other case on a bearing cap of a crankshaft bearing and a cover laterally on the cylinder block.

These known internal combustion engines have the advantage that their balancer shafts are substantially shorter and hence lighter, otherwise the arrangement of the bearings for the balancer shafts could result in problems of tolerance in components to be secured on the engine block.

According to the present invention, there is provided an internal combustion engine with a mass balancing of the second order which comprises two balancer shafts which are provided with balancing weights and disposed at different levels on both sides of the crankshaft parallel thereto and the upper one of which is driven by way of a chain drive in the same direction of rotation as the crankshaft and the lower one of which is driven through the intermediary of a pair of gearwheels in the opposite direction of rotation and at double the rotational speed, wherein the upper balancer shaft is driven by way of an extension of a chain drive provided for driving a lubricating-oil pump on the front end of the engine, while the lower balancer shaft is driven by way of a pair of gearwheels disposed in the transverse median plane of the engine.

The preferred embodiment of the invention offers the following advantageous features: 1. a chain drive already present for driving a iubricating oil pump is made use of in order to drive the upper balancer shaft; 2. the bearing means for the balancer shafts are provided directly in the engine block; and 3. because the drive for the lower balancer shaft is effected directly by way of a pair of gearwheels the dimensions and the weight of the said balancer shaft are kept to a minimum.

Furthermore, the problems of tolerance are avoided by superimposed components and the expenditure required for mounting and driving the balancer shafts is kept to a minimum.

If the upper balancer shaft extends in known manner from the front edge of the engine as far as the transverse median plane of the engine and if the rear one of the balancing weights, disposed on both sides of the bearing, is releasably secured to the balancer shaft by way of a groove and tongue joint and a screw connection, a small bearing diameter may be selected which reduces the bearing friction in an advantageous manner.

If the lower balancer shaft is in the form of a gearwheel formed integrally with the balancing weight and is mounted on a stationary axle which may be mounted from the outside in a receiving pocket in the cylinder block, a small bearing diameter is achieved in this case too with a minimum of expenditure on the bearing.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partial front view of the cylinder block of an internal combustion engine according to the invention, the drive of the upper balancer shaft on the front end of the engine being shown in the left-hand half of Figure 1 and the drive of the lower balancer shaft in the transverse median plane of the engine being shown in the right-hand side of Figure 1: Figure 2 is a section along the Il-Il in the left hand half of Figure 1; and Figure 3 is a section along the line Ill-Ill in the right-hand half of Figure 1.

The cylinder block 1 of an internal combustion engine is shown in Figure 1, a crankshaft 2 being received in bearings which are formed on bearing blocks 3 and bearing caps 4. The cylinder block 1 is open at the bottom in conventional manner and is closed by an oil sump 5.

As may be seen from the left-hand half of Figure 1 and from Figure 2, a chain drive 7 is provided on the front end 6 of the engine and extends between a sprocket wheel 8 secured to the crankshaft 2 and a sprocket wheel 9 of a lubricating-oil pump 10 which is only indicated diagrammatically. The chain drive 7 is provided with a conventional chain tensioner 11.

An upper balancer shaft 12 is disposed above the lubricating-oil pump 10 and is rotatably mounted in bearings 16 and 17 with a small diameter by way of a bearing flange 13 on the front end 6 of the engine and a bearing bush 14 in the transverse median plane 1 5 of the engine. In this connection the upper balancer shaft 1 2 extends axially through a tubular space 1 8 which is formed parallel to the crankshaft 2 in the cylinder block 1. Balancing weights are disposed on the balancer shaft 1 2 in a known manner adjacent its bearing 17, and the front balancing weight 1 9 is formed integrally with the balancer shaft 12 while the rear balancing weight 21 is releasably secured to the balancer shaft 12 by way of a groove and tongue joint 22 and a screw connection 23.

As may best be seen from the right-hand half of Figure 1 in conjunction with Figure 3, the lower balancer shaft 24 is disposed inside a pocket 25 of the cylinder block 1 in the region of the transverse median plane 1 5 of the engine. The lower balancer shaft 24 is formed integrally with a balancing weight 26 and a gearwheel 27 and is rotatably mounted on an axle 28 fixed in the cylinder block 1. The gearwheel 27 engages with a gearwheel 29 which is secured to an attachment 30 of a crank web arranged concentrically on the crankshaft 2. In this connection, the gearwheel 29 may be connected rotationally rigidly to the crankshaft 2 in known manner by shrink fitting, serrations or electron beam welding. The toothing may also be applied directly.

The cooperating gearwheels 27 and 29 may, of course, be constructed in known manner with a noise-reducing helical gearing.

The tubular space 1 8 and the pocket 25 may be arranged on the cylinder block 1 in such a way that the bores required for receiving the bearings and the axle for the balancer shafts respectively may be machined as continuous bores which are subsequently closed by simple covers after assembly has taken place.

Claims

1. An internal combustion engine with a mass balancing of the second order which comprises two balancer shafts which are provided with balancing weights and disposed at different levels on both sides of the crankshaft parallel thereto and the upper one of which is driven by way of a chain drive in the same direction of rotation as the crankshaft and the lower one of which is driven through the intermediary of a pair of gearwheels in the opposite direction of rotation and at double the rotational speed, wherein the upper balancer shaft is driven by way of an extension of a chain drive provided for driving a lubricating-oil pump on the front end of the engine, while the lower balancer shaft is driven by way of a pair of gearwheels disposed in the transverse median plane of the engine.

2. An internal combustion engine according to Claim 1, wherein the upper balancer shaft extends in known manner from the front end of the engine through a tubular space as far as the transverse median plane of the engine and a front balancing weight is formed integrally with the balancer shaft, whereas a rear balancing weight is releasably secured to the rear end of the balancer shaft in such a manner as to be fast in rotation with the balancer shaft.

3. An internal combustion engine according to Claim 1 or 2, in which the lower balancer shaft is directly driven by way of a pair of gearwheels substantially in the region of the transverse median plane of the engine, the lower balancer shaft being formed integrally with a balancing weight and the gearwheel, and being rotatably mounted on a stationary axle.

4. An internal combustion engine according to Claim 1,2 or 3, in which bores in the tubular space or a pocket receiving the respective balancer shafts are constructed as continuous bores.

5. An internal combustion engine according to any of Claims 1 to 4, in which a gearwheel disposed on the crankshaft to drive the lower balance shaft is secured thereto by a serration, by shrink fitting or by electron beam welding.

6. An internal combustion engine substantially as herein described with reference to and as illustrated in the accompanying drawings.