GB2468486A

GB2468486A - Variable compression ratio internal combustion engine with displaceable crankshaft

Info

Publication number: GB2468486A
Application number: GB0904011A
Authority: GB
Inventors: Trevor Derek Chesterton
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-09
Filing date: 2009-03-09
Publication date: 2010-09-15
Also published as: GB0904011D0

Abstract

This invention allows the crankshaft to be displaced relative to the cylinder to allow smaller and larger volumes in the cylinder at top dead centre whilst maintaining a fixed output shaft for primary and secondary drives, allowing conventional camshaft and ancillary drives, and a fixed output shaft. The crankshaft 1 may be carried in a ladder frame bearing carrier 2 which has additional bearings 4 allowing the ladder frame to pivot around the output shaft 5 having a gear set 6 in constant mesh with a gear on the crankshaft 1. An actuator shaft 7 is fitted to the side of the ladder frame bearing carrier 2 opposite the output shaft 5 and has teeth engaging teeth 8 on the ladder frame bearing carrier 2. Rotation of the actuator shaft 7 gives the ladder frame 2 an angular displacement which alters the position of top dead centre.

Description

Page 1 A Dynamically Variable Compression Ratio Internal Combustion Engine with a Fixed Output Shaft

Background

Internal combustion engines are most usually designed with a fixed compression ratio.

In order to optimise efficiency it is beneficial to have an ability to dynamically adjust the compression ratio.

One method of adjusting the compression ratio of an internal combustion engine is to raise and lower the crankshaft relative to the cylinder. This will directly affect the cylinder volume at top dead centre and hence affect the compression ratio.

A requirement for a conventionally manufactured engine is to allow primary drive and secondary drives, for ancillaries and camshaft drives for example, to be taken from a fixed output shaft. Displacing the crankshaft will make this difficult.

This invention is for a variable compression ratio internal combustion engine achieved by displacing the crankshaft whilst still allowing a fixed output shaft, allowing conventional existing primary and secondary drives to be employed. It allows a multi-cylinder in-line variable compression ratio engine to be built with the addition of 3 moving parts to an existing design. Fundamental to this invention is that the fixed output shaft also acts as a pivot to provide angular displacement of the crankshaft Page 2

Description of the Art

Figures la) and ib) shows the general construction of this design, The crankshaft (1) is carried in a ladder frame bearing carrier (2) using bearing caps (3) to support the journals. The ladder frame has additional bearings (4) in line with the crankshaft bearing caps. These allow the ladder frame to pivot around a shaft (5).

The shaft (5) that supports the ladder frame has a gear set (6) at one end that connects to the crankshaft. Because the angular displacement of the ladder frame (2) is around the same axis as its pivot (5), the gears are always in constant mesh. This allows the pivot shaft (5) to also function as the engine output shaft. Because this shaft is fixed conventional drive trains can be used for output, camshaft and ancillary equipment drives.

An actuator mechanism is fitted to the side of the ladder frame bearing carrier opposite the output shaft. This is shown as a geared shaft (7) which meshes with equivalent teeth (8) on the bearing carrier. Another actuating mechanism that would raise and lower the bearing carrier in the same angular fashion may be used.

By rotating the shaft (7), the ladder frame bearing carrier will have an angular displacement about the horizontal. This means the absolute position of top dead centre will change. In this way the compression ratio is altered dynamically.

The Design in Operation Figure 2 shows the design in operation When the bearing carrier is horizontal, the engine will have a nominal compression ratio. This is shown in figure 2 a).

When the actuating shaft is rotated anti-clockwise, shown in figure 2b) the bearing carrier will have an angular displacement resulting in the centreline of the crankshaft being displaced away from the cylinder head. This will mean the volume in the cylinder at top dead centre is greater than when the bearing carrier were horizontal.

This will result in a lower compression ratio.

When the actuating shaft is rotated clockwise, shown in figure 2c), the bearing carrier will have an angular displacement resulting in the centreline of the crankshaft being displaced towards the cylinder head. This will mean the volume in the cylinder at top dead centre is smaller than when the bearing carrier were horizontal. This will result in a higher compression ratio.

In all 3 instances, because there is an angular displacement of the bearing carrier about the pivot, and because the pivot is also the engine output shaft, the engine output shaft gears remain in constant mesh. This means a fixed output shaft for the engine is maintained and these operations can be achieved dynamically.