WO1990014501A1

WO1990014501A1 - Multi-cylinder positive displacement machines

Info

Publication number: WO1990014501A1
Application number: PCT/GB1990/000802
Authority: WO
Inventors: Michael Richard Lionel Daniel; Christopher Downton
Original assignee: Collins Motor Corporation Limited
Priority date: 1989-05-22
Filing date: 1990-05-22
Publication date: 1990-11-29
Also published as: AU5727790A; GB8911747D0

Abstract

A multi-cylinder positive displacement machine such as an internal combustion engine has its cylinders arranged both in radial sets (1, 2, 3; 4, 5, 6; 7, 8, 9) and in banks (1, 4, 7; 2, 5, 8; 3, 6, 9). Six, eight and nine cylinder engines are disclosed, all of compact construction.

Description

MULTI-CTLINDER POSITIVE DISPLACEMENT MACHINES

This invention relates to multi-cylinder positive displacement machines.

According to the invention there is provided a multi-cylinder positive displacement fluid machine in which the cylinders are arranged in sets and in banks, each set having at least three cylinders and each bank having at least two cylinders, the cylinders in each set being radial to a common crankshaft for the machine and having their pistons coupled by driving means to the same eccentric portion of the crankshaft, the

crankshaft having one eccentric portion associated with each set.

Suitable coupling means are disclosed in European Patent Application 0293233A and PCT Application No. PCT/GB89/01431.

Several forms of internal combustion engine (which may be compression-ignition or spark-ignition engines) will now be described by way of example with reference to the drawings, in which

Figure 1 shows diagrammatically the arrangement of the axes of a nine-cylinder four-stroke engine in accordance with the invention.

Figure 2 is a side-elevational view of the engine.

Figure 3 is a front view of the engine.

Figure 4 is a horizontal section through the engine.

Figure 5 shows one vertically reciprocating assembly of the engine.

Figure 6 shows portions of Figure 5 in side elevation,

Figure 7 shows the fibring order and intervals of the engine shown in Figures 1 to 6,

Figure 8 is a front view of an 8-cylinder four-stroke engine, and

Figure 9 shows an alternative to Figure 5.

Figure 1 shows diagramatically the layout of the axes of the nine cylinders 1 to 9 respectively relative to the crankshaft axis 10. The four-stroke engine thus has three banks of cylinders (extending from front to rear), the first bank A containing the cylinders 1, 4 and 7, the second bank B the cylinders 2, 5 and 8 and the third bank C the cylinders 3, 6 and 9. These cylinders may also be regarded as forming a first or front set 1, 2 and 3, a second set 4, 5 and 6 and a third set 7, 8 and 9.

Figure 2 is an outline view of the engine as seen in side elevation and Figure 3 a front view of the engine. Each bank of three cylinders has a common cylinder head 11 to which is secured a rocker cover 12 enclosing valve gear which may include an overhead camshaft for each bank of cylinder A, B, C. The inlet ducts of the cylinders of banks A and B are supplied with air from respective manifolds 13A and 13B located in the space between the banks A and B. The inlet ducts 14 of the third bank C are supplied by a further manifold in the space between the banks B and C. Where the engine is to be tilted, dry-sump lubrication may be used. Figure 4 shows a horizontal section through the crankshaft axis. The crankshaft 21 is mounted for rotation about its axis 10 in suitable bearings in a crankcase 22. The crankcase is divided at a horizontal plane through the axis 10 and provides front and rear main bearings 23 and 24 and two intermediate bearings 25 and 26. The crankshaft 21 has three throws defining three crankpins 27, 28 and 29 respectively for the front set of three cylinders 1, 2, 3, the middle set 4, 5 and 6 and the rear set 7, 8 and 9. The axes of the three crankpins are displaced relative to each other at intervals of 120° about the crankshaft axis 10.

Rotatably mounted on each crankpin 27, 28, 29 is generally square drive block 31 which is split along one diagonal plane and secured together by bolts (not shown).

Adjacent to each edge, the drive block 31 is formed with a cylindrical bore 32 which is connected to the peripheral face 33 by a slot 34. Slidable in each bore 32 is a generally cylindrical slider 35 of the same length as the bore 34

(greater than twice the throw of the crankshaft).

Each slider 35 is itself formed with a central longitudinal groove 36 to receive a web portion 37 of a connecting rod 38. The web portion 37 is secured in its slider by means of rivets 39.

At its outer end (relative to the crankshaft) each connecting rod 38 has an eye or 'little end' 39 through which passes a gudgeon or wrist pin 40 secured in a piston 41 sliding in the respective cylinder.

The slider in the lowermost groove 32D, however, is secured in a similar manner to a web portion 42 of a reciprocating guide assembly 43 to which are secured guide plates 44 by means of screws 45. Where the guide assembly 43 is formed of a metal, such as steel, having a different co-efficient of linear expansion to that of the crankcase 22, the pads 44 are secured to the outer ends of a bar 46 of material having the same co-efficient of linear expansion as that of the crankcase. The bar 46 is secured to the guide assembly 43 by a central pin 47.

The guide pads 44 co-operate with vertical guides 48 which can be secured directly to the crankcase 22 for example hy screws 49.

In order to reduce the axial length required for each drive block 31, the spacing in the axial direction between any two adjacent bores 32 (which have their axis at right angles to each other) may be made somewhat less than the diameter of each bore. To enable the outer ends of the sliders 35 to clear each other, these outer end portions are each formed with a flat 51 (Figure 4).

As can be seen in Figure 5, the sliders and grooves can be lubricated by oil fed from suitable drillings (not shown) in the crankpins 27, 28 and 29 into passages 52 leading frcm oil grooves 53 in the drive block into the bores 32.

As can be seen in Figure 4, the front end of the crankshaft 21 carries a tiining gear 55 meshing with a further timing gear 56 driving a spocket wheel 57 for a chain or ribbed belt driving the camshafts for each bank of cylinders.

The engine has a conventional electric starter motor 58.

Additionally, the front end of the crankshaft carries a pulley 59 for a driving belt 60 (Figures 2 and 3) for driving various accessories such as a pump 61 for an air conditioning installation, an alternator 62, a hydraulic pump 63 for power steering and a water pump 64 for circulating coolant ttøough water spaces in the banks of cylinders. In practice, the spacing between adjacent cylinders will be somewhat greater than shown in Figure 4 to accommodate water passages around liners forming the cylinders. These liners 65 are preferably extended inwards towards the crankshaft axis to just clear the throws of the crankshaft but have cutouts 66 to clear the drive blocks.

In operation, as the crankshaft rotates, the drive blocks 31 perform an orbiting movement around the crankshaft axis 10. The component of this motion which lies along the axis of each associated cylinder is transmitted to the piston (and vice versa) while the component of motion at right angles thereto is accommodated by relative sliding movement between the slider 35 and its bore 32. The blocks 31 are of sufficient size in relation to the throw of the crankshaft to ensure that the block never passes completely beyond the axis of each cylinder. Where, as shown for the slider 35D, it has a length of at least four times the throw T of the crankshaft, the slider is always in engagement with the block at positions on both sides of the centre line of the block. Exhaust manifolds are shown at 69.

Figure 7 shows the firing order of such an engine. Ideally, the engine, having nine cylinders, would fire at intervals of 8o°. As can be seen from Figure 7, the firing order is very nearly, but not quite regular since the intervals between the firing of cylinders Nos. 3 and 4, cylinders Nos. 6 and 7 and cylinders 9 and 1 is 60° while the other intervals are all 90°. Figure 8 is a front view of an eight cylinder four-stroke engine. This engine is constructed on similar lines to the previously described engine but has four banks of cylinders P Q R and S. Each bank consists of two cylinders. The crankshaft has two throws spaced angularly apart by 180°. The crankshaft thus has one intermediate bearing between the front and rear banks of cylinders and two drive blocks. Since each of the front and rear sets of cylinders has four piston and cylinder assemblies, the guide assembly 43 is replaced by a fourth connecting rod and piston assembly of the kind shown at 38 and 41 in Figure 5.

The driving belt (or chain) 71 for the valve gear passes over the four camshaft sprocket wheel 72 (one for each bank of cylinders) and around tvro diametrically opposed driving sprockets 73 (similar to the sprocket 57) and over two dimetrically opposed tensioning devices having sprocket wheel 74. Thus, variation in the valve t-hning of each bank relative to another is minimized in the event of an increase in length of the driving belt or chain 71.

The firing order in such an engine can conveniently consist of arranging for the four cylinders of the front set to fire at intervals of 90° as the crankshaft rotates, followed by firing of the four cylinders of the rear set, the cylinders in each bank firing at intervals of 360° relative to each other.

Each of the two engines described is statically balanced as the result of its construction. For this purpose, the mass of the guide asseaibly 43 and its slider 35D is made equal to that of the reciprocating assembly formed by the slider 35B, connecting rod 38B and piston 41B. Since the planes of action of the reciprocating assemblies and drive blocks on the crankshaft are distributed along the crankshaft axis, there sill be a rotating couple acting on the crankshaft. This can be readily balanced out by appropriate eccentric weights at the front and rear of the crankshaft, at opposite sides of the crankshaft axis.

In the modification shown in Figure 9, each of the three pistons 84A, 84B, 84C of one group is attached by a gudgeon pin 83 to one end of a connecting rod 85 the other end of which forms a guide surface 86 for a drive block 31' rotatable on the crankpin. At each end of the guide surface, the connecting is secured by tie bolts 87 and tubular spacers 88 either to the connecting rod of the opposed piston (84A, 84C), or in the case of the third piston 84B, to a T-shaped guide member 90 which includes a guide rod 91 slidable in a guide way 92 in the sump 93 of the engine.

A six cylinder engine can be constructed in a similar manner to the nine cylinder engine described above (using the arrangement of Figure 5 or Figure 9). In this case, there are two sets of three cylinders so that each bank contains two cylinders. Each set is associated with a respective crankpin and these two crankpins are at 180° to each, preferably with an intermediate bearing between them.

Claims

1. A multi-cylinder positive displacement fluid machine in which the cylinders are arranged in sets and in banks, each set having at least three cylinders and each bank having at least two cylinders, the cylinders in each set being radial to a common crankshaft for the machine and having their pistons coupled by driving means to the same eccentric portion of the crankshaft, the crankshaft having one eccentric portion associated with each set.

2. A machine according to claim 1, wherein at least one pair of banks are diametrically opposed and their pistons in each set are interconnected by constant length means of the driving means which include a drive block rotatably mounted on the corresponding eccentric portion of the crankshaft, the drive block being slidable relatively to the remainder of the constant length means perpendicularly to the common axis of the pair of pistons.

3. A machine according to claim 2, in the form of an internal combustion engine having three cylinders in each set, two being diametrically opposed and the third at right angles to the other two.

4. A machine according to claim 2, having four cylinders in each set arranged as two pairs of diametrically opposed cylinders with the axes of the two pair perpendicular to each other.