Composite cylinder block of an I.C. engine

Abstract

A composite cylinder block comprises an inner component defining one or more cylinder bores and main bearing supports of a crankshaft, and an outer component defining an upper crankcase, the inner component being inserted in the outer component, and being rigidly attached thereto. The arrangement provides a comparatively lightweight and rigid cylinder block.

Claims

1. A cylinder block for an internal combustion engine, the block comprising an inner component that is a unitary core separate from an outer component, the inner component comprising a cylinder bore and the outer component defining, at least in part, a crankcase, the inner component being inserted in the outer component and being rigidly attached thereto, and wherein the inner component comprises, at least in part, a main bearing housing for a crankshaft, and wherein the inner component is provided with an integral coolant passage configured to receive coolant from or supply coolant to a cylinder head, the coolant passage defined solely by the unitary core, whereby coolant flowing through the integral coolant passage is isolated from the outer component such that the coolant is separated from and cannot flow into contact with the outer component.

2. The cylinder block of claim 1, wherein the inner component is inserted in the outer component to define a clearance therebetween.

3. The cylinder block of claim 2, wherein the inner and outer components define a void therebetween, and said inner component is adapted for mounting of moving parts on the exterior thereof in said void.

4. The cylinder block of claim 1, wherein the inner component is wholly within the outer component.

5. The cylinder block of claim 1, wherein the outer component extends below a center line of the crankshaft.

6. The cylinder block of claim 5, wherein the inner and outer components include mating surfaces adapted to maintain the inner and outer components in register transversely and longitudinally of the center line of the crankshaft.

7. The cylinder block of claim 5, wherein the inner and outer components are coupled transversely substantially at the center line of the crankshaft.

8. The cylinder block of claim 1, wherein the outer component is in the form of a continuous skirt.

9. The cylinder block of claim 1, and further including main bearing caps connected to the inner component and comprising a bed plate.

10. The cylinder block of claim 1, wherein the inner and outer components are connected by screw-threaded fasteners.

11. The cylinder block of claim 1, wherein the inner and outer components are indirectly connected.

12. The cylinder block of claim 11, wherein the outer component and inner component are connected by a cylinder head.

13. The cylinder block of claim 12, wherein the cylinder head holds the unitary core and the outer component in a fixed rigid relationship.

14. The cylinder block of claim 1 incorporated in a multi-cylinder internal combustion engine.

15. The cylinder block of claim 1 is incorporated in an engine of a vehicle.

16. A reciprocating piston internal combustion engine comprising a cylinder block and a cylinder head, the cylinder block comprising an inner component that is a unitary core separate from an outer component, the inner component comprising a cylinder bore and the outer component defining, at least in part, a crankcase, the inner component being inserted in the outer component and being rigidly attached thereto, and wherein the inner component comprises, at least in part, a main bearing housing for a crankshaft, and wherein the inner component is provided with an integral coolant passage configured to receive coolant from or supply coolant to a cylinder head, the coolant passage defined solely by the unitary core, whereby coolant flowing through the integral coolant passage is isolated from the outer component such that the coolant is separated from and cannot flow into contact with the outer component, and the cylinder head indirectly attaching the inner component to the outer component to define a clearance therebetween.

17. An engine according to claim 16, and including a moving part mounted on the exterior of said inner component within said clearance.

18. An engine according to claim 16, wherein the inner and outer components are coupled transversely at the thrust side of said cylinder block.

19. An engine according to claim 18, wherein said inner and outer components are connected by opposed screw fixings substantially at a center line of the crankshaft.

Description

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(1) The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic perspective view of the inner core of an engine, defining cylinders and crankshaft center line, with pistons and rotating components;

(3) FIG. 2 corresponds to FIG. 1 and shows the assembly of FIG. 1 within a casing comprising upper crankcase and cylinder jacket;

(4) FIG. 3 is a flywheel end view of an assembly of similar appearance to FIG. 2, but without pistons or rotating components;

(5) FIG. 4 is an example section through an assembly corresponding to FIG. 3, with schematic cylinder head;

(6) FIG. 5 is a scrap section showing a welded connection;

(7) FIG. 6 is a schematic cross-section through another embodiment of the invention;

(8) FIG. 7 is a schematic cross-section through a further embodiment of the invention; and

(9) FIG. 8 is a schematic cross-section through still a further embodiment of the invention.

(10) With reference to FIG. 1, an inner component provided by a unitary core (10) of an in-line four cylinder engine defines the cylinders (11) and main bearing housings (12). Typically a main bearing will be provided at either end of the crankshaft, and between each cylinder pair, but fewer bearings are possible. The material of the core may be for example an aluminium alloy or cast iron.

(11) In the arrangement depicted, material content of the core (10) is minimized and thus pillars (13) connect the cylinders (11) and main bearing housings (12), and reinforcing ribs (14) are provided in the regions between the cylinders. The nature and form of the connecting and stiffening sections can be optimized by any known means according to the required duty, but it will be understood that internal and external surfaces of the core are generally accessible for machining. In the illustrated embodiment the cylinders are provided with an integral coolant passages (15) to be supplied via a cylinder head (not shown). However a coolant jacket could for example be provided by an assembled or welded component, in whole or in part, or be omitted if cylinder cooling is provided by other means. For example, the barrel like crankcase allows space for oil spray cooling onto the outside faces of the cylinders, from spray nozzles arranged between the inner and outer components.

(12) Although not clearly shown in FIG. 1, the main bearing housings (12) depend individually from the upper portion which defines the cylinder bores.

(13) FIG. 1 also illustrates pistons (16), crankshaft (17), balancer shafts and drive gear (18) and a multi-vee drive pulley (19). Protruding portions (21) of the core (10) provide bearing housings for the balancer shafts, and are an example of support for auxiliary moving components which can be provided on the core.

(14) A particular advantage of the core is that cylinder axes and crankshaft center line can be precisely aligned, along with associated moving components such as the balancer shafts. Thus misalignment of axes due to assembly of components can be obviated.

(15) The core can also provide fixing locations for relatively fixed internal components.

(16) The core (10) avoids deep internal recesses and hollows which characterize conventional cylinder block construction, in which the outer cylinder block wall is the outermost surface.

(17) Also illustrated in FIG. 1 are thickened ribs (23) for receiving cylinder head screws, and external bosses 24, 25 for engaging an outer component of the cylinder block.

(18) FIG. 2 illustrates the assembly of FIG. 1 inserted into an outer component provided by an enclosure (31) comprising a cylinder jacket and upper crankcase. For the purposes of illustration, the inner core assembly (with pistons, connecting rods, crankshaft etc.) is shown inserted, but it will be appreciated that the bare core (10) could be inserted into the enclosure (31) first, and the moving components added later.

(19) The inner core (10) is generally at a spacing from the enclosure (31) but suitable centralizing and locating features can be provided, such as by bosses (24, 25) fitting against corresponding bosses of internal faces of the enclosure. Such features, if provided, are for positioning purposes, are few, and need not add significant mass or material.

(20) As is clear from FIG. 2, the enclosure (31) can be wide throughout the axial length thereof, thus significantly increasing stiffness thereof compared with a narrow equivalent. The internal spaces are much less obstructed than those of a narrow block, as will be further described with reference to FIG. 4.

(21) The core (10) and enclosure (31) are rigidly attached by suitable means. For example if of compatible materials, the core and enclosure may be welded. Alternatively the components may be fixed by screws or bolts, for example via the cylinder head as a linking component.

(22) FIG. 3 shows a perspective view of a short engine assembly comprising the core 10 of FIG. 1 and the enclosure 31 of FIG. 2. The view is taken from a flywheel end of the assembly, showing a crankcase 50 defined at least in part by the volume enclosed by an oil pan 33 and enclosure 31.

(23) FIGS. 3 and 4 show an arrangement of bare components and consisting of a unitary core (10) and an enclosure (31); FIG. 4 illustrates a schematic cylinder head (32). Features common to FIGS. 1 and 2 have like reference numerals. The oil pan (33) is also depicted, though it will be appreciated that this component is in use attached after insertion of the internal moving components of the engine.

(24) With reference to FIG. 4, the cylinder head (32) is provided to hold the core (10) and enclosure (31) in a fixed rigid relationship. Thus, the cylinder head is typically provided with machine screws or bolts which pass through from the upper face to engage an array of threaded holes (34, 35) extending around the periphery of the core (10) and enclosure (31). The arrangement of holes (34, 35) is shown for illustration purposes, and more or less could be provided depending on the design duty. A conventional cylinder head gasket (not shown) is provided. Dowels or shouldered bolts may be provided to hold the components in a precise relationship. Through bolts or studs extending from the cylinder head to the bedplate are also possible, such fixings extending through or past the core (10).

(25) The block and core are thus unitized at the head face upon assembly. It will be appreciated that a bare core, or an inner core assembly, of the kind illustrated in FIG. 1 can be inserted into the enclosure (31), depending upon the preferred assembly sequence.

(26) As noted above the inner core (10) and enclosure (31) may have mutual location or abutment faces to permit correct positioning thereof. Thus in FIG. 4, transverse shoulders (36) extend to internal contact faces of the enclosure from the main bearing region (38). These shoulders need not be provided in the plane of the main bearings, nor at every such plane, nor in opposition to one another.

(27) In an alternative, the lower main bearing supports may be provided together on a deck plate, which extends transversely to meet a downwardly extended enclosure (31) (not shown). In this arrangement the shoulders (36) are no longer necessary, and a greater volume is thus provided within the crankcase above the crankshaft center line.

(28) In addition to locating the core (10) within the enclosure (31), the shoulders (36) may also provide a path from the inner core to the engine mountings for resisting engine torque. For this purpose the shoulders (36) should preferably be provided below the cylinders, and generally transversely to the crankshaft center line. Additional support may be provided in the region of the cylinder wall of the core (10), in order to resist transverse piston thrust. As is well understood, owing to the unidirectional rotation of four-stroke engines, support against crankshaft loads and piston thrust is required substantially on one side of an engine, so that the required support may not be provided equally on both sides. Such considerations may not apply for two-stroke or other kinds of combustion cycle to which the invention can be applied. In particular in a two-stroke variant, the space between the core and enclosure may be used to confine the crankcase charge induced by engine rotation.

(29) In order to improve stiffness of the assembly of core and enclosure, screw fixings may be provided at touching points, as illustrated by reference numerals (37). Cross-bolts in the form of set screws inserted from the outside into threaded holes (47) of the core (10) are one possibility, and may include a plane shank portion so as to precisely locate a corresponding hole of the enclosure (31) with respect to the core (10). The core and enclosure may alternatively be placed in register by dowels and secured by screw fixingsor be connected via shouldered bolts having a dowel diameter for engaging a precise through hole of the enclosure.

(30) In the embodiment of FIG. 4, such fixings have the additional function of holding the core and enclosure in precise pre-determined relationship upon removal of the cylinder head.

(31) The touching points between the core and enclosure are typically machined surfaces sized for a sliding or interference fit. The transverse location of the contact face(s) and profile of the adjacent structure is selected according to design requirements and available space. Accordingly the shoulders could extend inwardly wholly from the enclosure (31), or suitable shoulders could extend part-way from core (10) and enclosure (31), as illustrated by the contact face (41) of FIG. 3. One or more machined abutments may determine insertion depth of the core or core assembly within the enclosure.

(32) FIGS. 2 and 3 also indicate that contact faces of the enclosure could have an internal mouth (42) in order to recess cross-bolts, and provide additional wall stiffness in the connection area.

(33) As noted above the core and enclosure can be welded, or otherwise permanently attached, if of compatible material. Such a weld (43) may for example lie in the mouth (48) of the space between the core and enclosure just below the cylinder head face, as illustrated in FIG. 5. Alternatively a proud weld could be skimmed so as to give a flat head mounting face across both core and enclosure.

(34) FIG. 4 clearly shows that substantial internal voids or spaces and apertures 44-46 can be formed in and around the core (10) so as to permit movement of the crankcase gases. As a result, windage caused by reciprocal piston movement can be substantially eliminated.

(35) FIG. 6 shows an alternative embodiment of the composite cylinder block of the present invention. In the Figure, an inner component, in the form of an inner core (110) defines a cylinder bore. An outer component provided by an enclosure (131) defines a barrel-like upper crankcase (151), and unitary upper bed plate (154) defining the cylinder side main bearing supports of a crankshaft (not shown). A cylinder head (132) unitizes the inner and outer components so that the cylinder block is a composite.

(36) Typically the cylinder head (132) may be attached to both the inner component and to the outer component by screw-threaded fasteners engageable in locally thickened portions thereof.

(37) The inner component may be located within the outer component by suitable lateral ribs or bosses, and/or by axial features such as the upstanding crankcase collar 15. The inner component may also be recessed within the cylinder head as illustrated, to give a close-fitting upper location.

(38) In FIG. 6, one separate main bearing cap 156 is illustrated; in practice it will be understood that such caps are required for each main bearing location, and in one embodiment of the invention these caps are integrated into a lower bed plate (not shown), which may extend transversely across substantially the entire width of the upper bed plate 154.

(39) Typically the inner component is formed at least in part from cast iron, and the outer component of cast aluminium. This arrangement provides a substantial weight saving in a stiff unitized structure.

(40) As will be clear from FIG. 6, the usual lateral ribs, formed by the runners of a conventional casting, are absent so that the spaces 144, 146 on either side of the cylinder are relatively large, and unobstructed. These spaces are of the order of the cylinder bore, or larger. The wide barrel-like upper crankcase (151) thus gives a stiff structure with reduced internal windage in use.

(41) It will be understood that the separate inner and outer components may be finish machined on both internal and external faces. This allows possibilities of weight saving and surface finishing which are not possible with a conventional unitary engine block.

(42) The spaces 144, 146 may be utilized, at least in part, for other engine components. For example cylinder cooling may be provided by oil spray, illustrated schematically at 118, and internal mounting of engine ancillaries 119 becomes possiblethe latter may comprise for example a pump.

(43) The inner component 110 may incorporate a coolant jacket (not shown) around the cylinder, and connecting with coolant supply and return passages of the cylinder head 132. The outer component (131) may comprise integrated engine mountings and the like (not shown for clarity).

(44) The variant of FIG. 7 differs by the provision of a coolant jacket (121) as an annular close-fitting projection (122) of the cylinder head (132). Such an arrangement can provide effective cooling of the working part of the cylinder whilst obviating a gasket to seal the cylinder head (132) to the inner component (110). Other options, as described in relation to FIG. 6 remain possible, though it will be understood that spray cooling may not be necessary if a coolant jacket (121) is to be used.

(45) In FIG. 8, the outer component (131) extends inwardly toward the cylinder at 153 so as to provide an upper location for the inner component (110). This arrangement obviates the need for a locating portion of the cylinder head (132), as illustrated in FIGS. 6 and 7. The cylinder head (132) and outer component (131) are typically located in the transverse plane by suitably placed dowels or fitted bolts (not shown). In the FIG. 8 embodiment it will be appreciated that the inner component (110) may be a press or interference fit within the outer component (131).

(46) As illustrated in FIGS. 6-8, the inner component (110) has lateral location provided by the outer component (131); this lateral location may be continuous about the inner component (110) or may be constituted by a sufficient number of spaced abutments.

(47) It will also be understood that typically the inner and outer components are of different materials having different melting temperatures. Accordingly one component may be fixed relative to another component by form locking during casting of the lower melting point material.

(48) This application describes an engine or engine block having an inner component defining a cylinder bore and an outer component defining, at least in part, a crankcase for a crankshaft of the engine, the inner component being inserted into the outer component and rigidly attached thereto. In one embodiment, the inner component defines, at least in part, a main bearing support for a crankshaft. In other embodiments, the outer component defines, at least in part, a main bearing support for the crankshaft. Each of these disclosed embodiments achieves the aims stated hereinabove and thus involve a common inventive concept.

(49) This application claims priority from UK patent application no. GB 1019356.3, filed 16 Nov. 2010, the entire contents of which are expressly incorporated herein by reference.