GB2564409A

GB2564409A - Radial piston machine

Info

Publication number: GB2564409A
Application number: GB1710904.2A
Authority: GB
Inventors: Pendell Michael
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-07-06
Filing date: 2017-07-06
Publication date: 2019-01-16
Also published as: GB201710904D0

Abstract

A radial reciprocating piston machine has multiple pistons 11, each slidable in a respective cylinder 2, the cylinders being arranged radially around a central drive shaft 3. Each piston is connected via a piston rod 10 to an offset annular gear 5 having inwardly-directed teeth meshing with external gear teeth on the drive shaft. The annular gear thus rotates about an axis which is in turn orbiting about the shaft, either driving the shaft or being driven therefrom. The machine may be an internal combustion engine, pump or compressor. Preferably it comprises at least one bank of cylinders with an even number of pistons, more preferably multiple such banks, each one having a respective ring gear meshing with a common drive shaft. The or each ring gear is carried by cranks 8 mounted on respective crank journals (9, fig. 3) carried by mountings which are fixed with respect to the cylinders. Preferably there are four pairs of cranks, each pair supporting the ring gear on both axial sides thereof, and the crankpins also serve as gudgeon pins for the piston rods 10. Any additional piston rods are preferably connected to the annular gear at locations intermediate the cranks.

Description

RADIAL PISTON MACHINE

Field of the Invention

This invention relates to a radial piston machine, for example a radial internal combustion engine or a radial compressor or pump.

Background to the Invention

Conventionally, a radial engine has an odd number of cylinders arranged around a main crankshaft. It is usual to have an odd number of cylinders, as this is considered to ensure a smooth firing sequence with a 4-stroke cycle. A typical radial engine has a single crankshaft to which the master connecting rod attaches, with the other cylinder rods connected to pivot points around the master rod. The force on the master connecting rod assembly when the pistons are on the downward stroke transfers to the crankpin to produce turning, which rotates the crankshaft. It is thought that the inefficiency of the crankshaft arrangement is where the majority of an engine’s power losses occur when transferring the energy of a reciprocating piston to rotational force.

The present invention seeks to improve on the efficiency.

Summary of the Invention

According to the present invention, there is provided a radial reciprocating piston machine having a plurality of pistons, each slidable in a respective cylinder, the cylinders being arranged radially around a central drive shaft, each piston being connected via a respective piston rod to an offset annular gear having inwardly-directed gear teeth meshing with external gear teeth on the drive shaft, the annular gear having an internal diameter greater than the external diameter of the toothed shaft so as to rotate about an axis which is in turn orbiting about the shaft, thereby transmitting drive to or from the shaft.

The arrangement may be compared with a Tusi couple, but operating in reverse, that is to say, the annular gear is caused to orbit around a gear having a fixed axis of rotation.

Preferably, the machine has at least a single bank comprising an even number of pistons, but may be provided with multiple banks of even numbers of cylinders, each bank having a respective offset annular gear meshing with a common drive shaft. Although an odd number of cylinders may be incorporated in the machine of the invention, the geometry tends to favour an even number.

It will be appreciated that the drive shaft will be configured to cause reciprocation of the pistons in the case of a compressor or pump and to be rotated by the pistons in the case of an engine.

The or each annular gear is preferably carried by a plurality of cranks mounted on respective crank journals carried by mountings which are fixed with respect to the cylinders. Conveniently the or each annular gear is mounted between four pairs of said cranks, the positions of the cranks on the annular gear or gears corresponding with the connection of piston rods. If the machine has more than four cylinders in a bank, the additional piston rods may be connected to the annular gear at locations intermediate the cranks.

While conventional mechanical valve trains may be employed to operate the valves, electromechanical operation of the inlet and outlet valves for the cylinders will simplify construction of the machine, while offering flexibility and efficiency of operation.

While maintaining the advantages already known with radial configured internal combustion engines, which have significantly better power to weight ratio than inline engines, this design should reduce the mechanical energy losses suffered from conventional crankshaft design when converting reciprocating motion into rotary motion.

The engine should offer smoother power delivery, more torque and be more fuel efficient whilst in turn delivering a larger power output than conventional radial engine design.

Brief Description of the Drawings

In the drawings, which illustrate an exemplary embodiment of the invention:

Figure 1 is an isometric view of a radial engine, omitting the cylinder heads and valve and ignition arrangements;

Figure 2 is a sectional elevation on Line A-A in Figure 1, with some items not sectioned for clarity;

Figure 3 is a sectional plan view on line B-B in Figure 1, with some items not sectioned for clarity;

Figure 4 is an enlarged simplified view corresponding to that of Figure 2, but with the cylinders and associated components removed; and

Figure 5 is a sectional plan view corresponding to that of Figure 3, but illustrating a double-bank engine.

Detailed Description of the Illustrated Embodiment

The engine shown in Figures 1 to 4 is an eight-cylinder radial engine, having a housing 1 with the eight coplanar cylinders 2 equally spaced around it. A straight drive shaft 3 is mounted with its longitudinal axis along the axis of symmetry of the housing 1. A piston 11 slides within each cylinder 2 and is connected to one end of a respective connecting rod 10 through a gudgeon pin 12 in conventional manner. Each connecting rod 10 is connected at its other end to an annular gear 5 through a crankpin journal 6 or a gudgeon pin 7. The annular gear 5 has inwardly-directed teeth 5a, which mesh with external gear teeth 3a on the drive shaft 3, and is carried between four pairs of cranks 8 mounted on crank journals 9 supported by bearings 9a mounted in housing rings 4, which are in turn secured on opposed sides of the housing 1. The housing rings 4 also carry central bearings 20 for the drive shaft 3.

Four of the connecting rods 10 are connected to the annular gear 5 through the respective crankpin journals 6 which carry the cranks 8, while the other four connecting rods 10 are connected to the annular gear 5 by gudgeon pins 7.

The cranks 8 constrain the movement of the annular gear 5 to perform an orbit around the drive shaft 3 while the internal teeth 5a of the annular gear remain in mesh with the external teeth 3a of the shaft 3, transferring drive to the shaft. The annular gear 5 performs its orbit around the shaft 3 in the opposite direction to the rotation of the shaft.

In one example according to the invention, with reference to Figure 2, the annular gear 5 is a 40 tooth 100mm PCD which drives the gear 3a on the main drive shaft 3 which is a 20 tooth 50mm PCD. Guided by the cranks the orbital motion of the internal gear ring drives the main output shaft at a ratio of 1:1.

The engine is fuel injected, a fuel pump drawing fuel from an external fuel reservoir to a fuel filter, the fuel then flowing through tubing into the top of the fuel rails (not shown). Fuel injectors are connected to the fuel rails. The fuel injector ends are mounted in the final air intake manifolds and fuel is sprayed directly in front of the inlet vale, in conventional manner. The main air inlet manifold is mounted on the top of the engine and there are four vertical secondary air inlet manifolds extending downwards. From these are bolted the final air inlet manifolds that are attached to the cylinder bodies. Control of the injectors will be by an electronic control unit (ECU) in conventional manner, according to the speed of rotation of the drive shaft and the throttle settling.

For timing of the inlet and exhaust valves (not shown) sensors are mounted at the top of the engine to provide control signals to the ECU, reading the rotational speed of the drive shaft. The drive shaft drives an epicyclic gear arrangement providing the timing signals (the epicyclic gear arrangement for the timing sensors in the example is 8:1, Sun Gear=24 tooth, Planet gears=84 tooth and Internal gear=192 tooth Module 1). The valves will be actuated electrome-chanically and thus require no camshaft or associated timing gear. The ECU will provide the timing signals for their operation. This will permit fully adjustable valve timing. Every inlet and outlet valve should open once in every two rotations of the drive shaft.

The drive shaft 3 has an output spline 21 at one end thereof and an externally toothed gear 22 at the opposite end. The output spline 21 engages a secondary shaft (not shown), either directly or via a coupling, the secondary shaft having a helical bevel gear which extends vertically into the base and drives a horizontal output shaft and various layshafts for the alternator and starter motor. The externally toothed gear 22 acts as the sun gear for the epicyclic gear arrangement that controls the timing sensors.

Figure 5 illustrates another embodiment including two banks of cylinders and pistons mounted side-by-side and driving a common drive shaft. The engine thus becomes a sixteen-cylinder engine. It will be seen from the Figure that the annular gears are arranged to rotate 180 degrees out of phase to balance the motion, meaning that piston number 1 in Bank 1 is at TDC the same time as piston number 5 in Bank 2 is at TDC which helps maintain engine smoothness by allowing each piston to cancel out the reciprocating opposite force. The internal gear rings will also assist engine inertia. The number of teeth on the annular gear and drive shaft will need to be even to ensure correct alignment for both banks.

With a large number of cylinders operating at high compression, the load on the starter motor may be such that the electromechanical valves are all initially opened to assist the starter in spinning the engine up to a minimum operating speed, say 400 rpm, before normal operation is resumed and the engine combustion cycle is started.

The engine may be a spark-ignition engine or a compression-ignition engine, and further performance enhancing features such as turbochargers or superchargers may be added.

It will be appreciated that, while the specific examples illustrated are internal combustion engines, the arrangement shown may be readily adapted to operate as a pump or compressor. It will be further appreciated that the machine may have fewer than eight cylinders in a bank - at least four - but may also have more.

Claims

1. A radial reciprocating piston machine having a plurality of pistons, each slidable in a respective cylinder, the cylinders being arranged radially around a central drive shaft, each piston being connected via a respective piston rod to an offset annular gear having inwardly-directed gear teeth meshing with external gear teeth on the drive shaft, the annular gear having an internal diameter greater than the external diameter of the toothed shaft so as to rotate about an axis which is in turn orbiting about the shaft, thereby transmitting drive to or from the shaft.

2. A machine according to Claim 1, comprising at least a single bank of cylinders comprising an even number of pistons.

3. A machine according to Claim 2, comprising multiple banks of even numbers of cylinders, each bank having a respective annular gear meshing with a common drive shaft.

4. A machine according to Claim 1 or 2, wherein the or each annular gear is carried by a plurality of cranks mounted on respective crank journals carried by mountings which are fixed with respect to the cylinders.

5. A machine according to Claim 4, wherein the or each annular gear is mounted between four pairs of said cranks, the positions of the cranks on the annular gear or gears corresponding with the connection of piston rods.

6. A machine according to Claim 5 having more than four cylinders in a bank of cylinders, wherein the additional piston rods are connected to the annular gear at locations intermediate the cranks.

7. A machine according to any preceding claim, wherein each cylinder is provided with electromechanically operated inlet and outlet valves.

8. A machine according to any preceding claim, which is an internal combustion engine.

9. A machine according to any of Claims 1 to 7, which is a pump or compressor.