GB2338745A

GB2338745A - Reciprocating piston engine with Z-crank and adjustable piston stroke

Info

Publication number: GB2338745A
Application number: GB9813621A
Authority: GB
Inventors: William May Stott
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-06-25
Filing date: 1998-06-25
Publication date: 1999-12-29
Anticipated expiration: 2018-06-25
Also published as: GB9813621D0; GB2338745B

Abstract

By fitting an axial moving and tilting bearing 2,3 on to a rotary shaft 1, a variable stroke Z-crank mechanism is obtained. Axial movement of the bearing on the shaft moves the piston 9 axially in the cylinder and tilts the piston arm 5. The stroke of the engine may thus be varied steplessly from the maximum stroke to zero, while allowing the piston location to be adjusted in the cylinder. The compression ratio is thus maintained at the optimum value and throttling of the inlet charge is not needed, enabling the engine to operate more efficiently in the part-load condition. Piston and ring friction, heat loss to the cylinder wall and induction and pumping loads are reduced.

Description

1

PATENT APPLICATION SPECIFICATION

1 Subject; Reciprocating piston engine 2338745 2 Scope; An arrangement whereby the stroke of a reciprocating piston engine may be varied in a continuous manner, from the maximum stroke to a zero figure.

Means are also incorporated to maintain / ad ust the compression pressures.

li 3 Introduction

3.1 Background The present design of internal combustion engine has nearly reached its Emit in efficiency in its present form. Any significant improvement will require a more radical design approack The present design of 1 C engine is generally determined by:1 maximum power - engine capacity - say approximately 2% usage 2 maximum compression ratio - fiffi throttle operation - say approx 3% usage 3 part load - by throttling inlet charge say approx 95% usage Items 1 and 2 produce maximum efficiency, and item 3 decreases this efficiency. This decrease becoming larger as the throttling increases. Clearly throttling is an extremely inefficient method of engine operation, and is used for the majority of the engine running time. The decrease in efficiency is caused by the lowering of the achieved compression ratio ( CR and the increased pumping losses. The criteria for improvement is therefore to avoid throttling the inlet charge whilst still maintaining the compression ratio at a suitable level. In order to avoid throttling the inlet charge the engine must be run at the fix power setting, or open throttle. To reduce this power to the level required by the vehicle to run in the lower power / speed ranges efficiently, the amount of inlet charge must be reduced. This can be achieved by reducing the engine capacity in a stepless manner i.e. piston stroke. Providing the C.R. can be maintained at the required figure, this is a very efrective method as the engine can nom- operate at part load in a much improved Specific Fuel Consumption range, with reductions in:a) piston and ring ffiction b) beat loss to the cylinder wall c) induction and pumping loads d) exhaust gas quantity as these items are approximately proportional to the piston stroke length.

2 3.2 Example

The following general data enables comparison between an engine being operated conventionally and in unthrottled modes.

Using 20 mph / 1000 rpm data Data Conventional Mode Unthrottled Mode Road B11P Spec Fuel Fuel Spec Fuel Fuel Improv % Full Speed Reqd, Consump Used Consump Used %Stroke mph lb/hp/hr lb lb/hp/hr lb 5 1 5 0.52 2.6 92 11.4 7.5 0.9 6.75 0.49 3.675 84 17 so 10 0.8 8 0.49 4.9 63 22.7 14 0.72 10.1 0.51 7.14 42 31.8 20 0.65 13 0.53 10.6 23 45.5 30.5 0.61 18.6 0.56 17.08 9 69.3 44 0.65 28.6 0.65 28.6 0 100 average44.6% assuming power output proportional to stroke Note a) a more realistic average would be say from the 30 to 70 Mph range ( 60.8 % b) modem engines being more eflicient, say 60 bhp / litre, will require more throttling to reduce the power output c) it can also be seen that the fiffi stroke reserve engine power output is retained for acceleration and hill climbing 4 Technical 4.1 Basic Principle, see figure 1 By fitting a axial moving and Tilting bearing on to a rotary shaft, a variable stroke Z-Crank mech see fig 2 is obtained. Axial movement of the bearing on the shaft, moves the piston axially in the cylinder, and tilts the piston arm. The piston stroke being the product of the tilt arm radial movement tirnes the ratio of the tilt arm length and the piston arm length times two. The C. R. adjustment being controlled by the ratio of the radial tilt to axial movement..

4.2 Design components, see figures 3 and 4 1# Engine shaft 2# Axial sliding pivot 3# Tilt bearing 4# Tilt / torque arm 5# Piston arm 6# Piston arm slide bearing - prevents rotation of 54 7# Engine shaft fixed guide block 8# Axial power actuator ( or alternatively 10# 9# Piston 10# Control 1 power axial actuator rod ( or alternatively 8# 1 3 2 3 4.3 Operating arrangement 1 axial movement of actuator bearing 8# (or 10#),produces two actions a) axial movement of the piston 94, in the cylinder b) annular movement of the tilt arm 4#, in the fixed guide block guide path at the fixed guide block 7#, ratios the tilt arm 4#, axial to radial movement radial movement of the tilt arm 4#, tilts bearing 3#, and piston arm 5#. The radial movement times the ratio of the piston arm 5# length / tilt arm 4# length, moves the piston one half stroke.

4 one complete revolution of engine shaft 1#, and tilt bearing 39, moves the piston one complete stroke. Note:- piston arm 5#, does not rotate. the difference in the axial movement dimension initiated by action 1, minus the resultant dimension produced by action 3, allows the C. R. to be adjusted.

1 1 4

Claims

Claims 5.1 A mechanical arrangement, which allows the stroke of a

reciprocating piston engine to be varied in a stepless continuous manner, from zero to maximum.

The arrangement also allows the piston location in the cylinder to be adjusted.

These movements may be carried out as separate individual actions or in a combined coordinated action.

/1 5.2 This arrangement enables an internal combustion engine to operate more efficiently in the part load range with;a) much improved part load Specific Fuel Consumption ( Conservation) figures by -maintaining high C. R. throughout speed range lower internal engine friction lower pumping losses lower heat loss to cylinder walls b) lower starting torque ( minimum starting stroke required c) lower quantity of exhaust gas output ( reduced Pollution) 1 W