CYLINDER BLOCK AND ENGINE BODY

Abstract

 A cylinder block includes a bore wall having at least one cylinder bore, an outer wall located outside an outer periphery of the bore wall, and a water jacket defined between the outer periphery of the bore wall and an inner periphery of the outer wall. The cylinder block is an open-deck cylinder block in which a top end of the water jacket is opened. The outer periphery of the bore wall and the inner periphery of the outer wall have respective top edges at the top end of the water jacket. At least one of the outer periphery of the bore wall and the inner periphery of the outer wall has at least one recess at the corresponding top edge. The cylinder block includes at least one reinforcing member that is fitted in the at least one recess and covers part of the water jacket.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an open-deck cylinder block having therein a water jacket having an opening at the top surface of the cylinder block and to an engine body having such a cylinder block.

[0002] An open-deck cylinder block is known in the art which has therein a water jacket that is formed between a cylindrical bore wall and an outer wall of the cylinder block and is opened at the top surface of cylinder block. The use of such an open-deck cylinder block can reduce the weight and improve the cooling performance of the engine because of the presence of the water jacket. Additionally, the open-deck type cylinder block is advantageous in terms of its castability. On the other hand, however, there is a problem in the open-deck cylinder block in which the top end of the bore wall is a free end in that deformation of the cylinder block increases. To solve the problem, Japanese Patent Application Publication No. H03-253752 discloses an open-deck cylinder block that prevents its deformation by disposing a reinforcing member at a position in the cylinder block adjacent to the top end of a water jacket.

[0003] In casting a cylinder block, the die for the cylinder block has a draft so that the cast cylinder block is removed easily from the die. Therefore, the width dimension of the water jacket tends to have variation. In the case of the cylinder block disclosed in the above Publication, the reinforcing member may not be inserted into the water jacket if the width of the water jacket is smaller than design value and the reinforcing member may fall into the water jacket if the water jacket width is larger than the design value. To avoid such a problem, the tolerance of dimensions of the water jacket may be set smaller, which inevitably increases the cost of controlling the dimension of the water jacket.

[0004] The present invention which has been made in light of the above problems is directed to providing an open-deck cylinder block having a reinforcing member mounted securely in the water jacket while relaxing the dimensional tolerance of the water jacket.

SUMMARY OF THE INVENTION

[0005] In accordance with one aspect of the present invention, there is provided a cylinder block including a bore wall having at least one cylinder bore, an outer wall located outside an outer periphery of the bore wall, and a water jacket defined between the outer periphery of the bore wall and an inner periphery of the outer wall. The cylinder block is an open-deck cylinder block in which a top end of the water jacket is opened. The outer periphery of the bore wall and the inner periphery of the outer wall have respective top edges at the top end of the water jacket. At least one of the outer periphery of the bore wall and the inner periphery of the outer wall has at least one recess at the corresponding top edge. The cylinder block includes at least one reinforcing member that is fitted in the at least one recess and covers part of the water jacket that extends from the at least one recess.

[0006] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a fragmentary top view of a cylinder block according to a first embodiment of the present invention;

FIG. 2 is a fragmentary sectional view of an engine body with a cylinder head disposed on the cylinder block, taken along the line II-II of FIG. 1;

FIG. 3 is a fragmentary top view of a cylinder block according to a second embodiment of the present invention;

FIG. 4A is a fragmentary top view of a cylinder block according to a third embodiment of the present invention; and

FIG. 4B is a fragmentary sectional view of the cylinder block of FIG. 4A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

First embodiment

[0008] The following will describe a cylinder block and an engine body having the cylinder block according to a first embodiment of the present invention with reference to FIGS. 1 and 2. The cylinder block according to the present invention may be used in a gasoline engine and a diesel engine, but an ignition plug of a gasoline engine or a fuel injection nozzle of a diesel engine is not shown in FIG. 2.

[0009] Referring to FIG. 1, there is shown a cylinder block 10 of an engine body 1 shown in FIG. 2. The cylinder block 10 includes a plurality of cylinder bores 11 (only two cylinder bores shown in FIG. 1) each accommodating therein a piston 50 and formed by a bore wall 12. The plural cylinder bores 11 are arranged at a predetermined interval in the axial direction (up and down direction as seen in FIG. 1) of a crank shaft 51 shown schematically in FIG. 2. For the sake of the description, an imaginary plane extending in the axial direction of the crank shaft 51 and containing the axis A of each cylinder bore 11 will hereinafter be referred to as the imaginary plane C of the cylinder block 10.

[0010] A water jacket 14 is defined in the cylinder block 10 between the outer periphery of the bore wall 12 and an inner periphery of an outer wall 13 of the cylinder block 10 located radially outward of the bore wall 12 and has a groove shape. The water jacket 14 has a shape that combines a plurality of continuous connected arcs surrounding circumferentially the cylinder bores 11. The cooling water flowing in the water jacket 14 cools the engine body 1.

[0011] In the present embodiment, the cylinder block 10 is made of aluminum alloy for reducing the weight of the engine body 1. For improved castability and cooling performance of the cylinder block 10, as well as for further weight reduction, the cylinder block 10 is of an open-deck type in which a coolant passage or the water jacket 14 formed in the cylinder block 10 is opened at the top surface of the cylinder block 10. The cylinder block 10 is provided with reinforcing members 15 for suppressing the deformation of the open-deck cylinder block 10. The reinforcing members 15 will be described in detail later.

[0012] Referring to FIG. 2, there is shown an engine body 1 including the cylinder block 10, a cylinder head 20 provided on the cylinder block 10, and a gasket 30 provided between the cylinder block 10 and the cylinder head 20. The cylinder head 20 has therein an intake port 21 and an exhaust port 22. An intake valve 23 is provided in the intake port 21. An exhaust valve 24 is provided in the exhaust port 22.

[0013] When the piston 50 is moved reciprocally up and down in the cylinder bore 11 during the operation of the engine body 1, the piston 50 is displaced slightly in the right and left direction as seen in FIG. 2, or in the direction that is perpendicular to the imaginary plane C in FIG. 1, thereby causing the piston 50 to be pressed against the bore wall 12. Such direction will hereinafter be referred to as the thrust direction and anti-thrust direction. The cylinder block 10 thus receiving the thrust force of the piston 50 tends to be deformed in the thrust and anti-thrust directions. Especially, the deformation of the cylinder block 10 tends to occur on the side where the piston 50 is pressed against the bore wall 12 in explosion stroke (expansion stroke) of the engine body 1, or on the left side as seen in FIG. 2. Such side will hereinafter be referred to as thrust side. The deformation need to be suppressed.

[0014] In the present embodiment, the reinforcing members 15 are provided in the water jacket 14 on the thrust side of the respective cylinder bores 11 for suppressing the deformation on the thrust side of the cylinder block 10. Specifically, as shown in FIG. 1, the reinforcing member 15 is disposed at a position in the water jacket 14 where an imaginary plane B passing through the axis A of the cylinder bore 11 and extending perpendicularly to the imaginary plane C and the water jacket 14 intersect each other. No reinforcing member such as 15 is disposed at the position in the water jacket 14 on the side of the cylinder bore 11 opposite to the thrust side. Such side of the cylinder bore 11 will hereinafter be referred to as anti-thrust side.

[0015] The reinforcing member 15 is formed in a rectangular parallelepiped shape and made of an aluminum alloy or the same material as the cylinder block 10. If the reinforcing member 15 and the cylinder block 10 are made of different materials, strain may occur due to the difference of the linear expansion coefficient of the two materials and a gap may be formed, and there may be a fear of corrosion caused by corrosion potential. However, using the same material for the cylinder block 10 and the reinforcing member 15 may prevent these problems.

[0016] A recess 12a is formed for each cylinder bore 11 in the outer periphery of the bore wall 12 of the cylinder block 10 at a top edge thereof facing the water jacket 14 and along the imaginary plane B. Similarly, a recess 13a is formed for each cylinder bore 11 in the inner periphery of the outer wall 13 of the cylinder block 10 at a top edge thereof facing the water jacket 14 and along the imaginary plane B. The paired recesses 12a and 13a are formed across the water jacket 14 and complementarily to the reinforcing member 15 so that the reinforcing member 15 is fitted closely at the opposite ends thereof in the recesses 12a, 13a.

[0017] The reinforcing member 15 fitted in the recesses 12a, 13a covers part of the water jacket 14 between the paired recesses 12a, 13a. The top surface of the reinforcing member 15 is substantially flush with the top surfaces of the bore wall 12 and the outer wall 13 of the cylinder block 10. The reinforcing member 15 is fitted in the paired recesses 12a, 13 with no clearance therebetween.

[0018] In the present embodiment, the engine body 1 has the intake port 21 on the thrust side of the cylinder bore 11 and the exhaust port 22 on the anti-thrust side, as shown in FIG. 2. That is, the reinforcing member 15 is disposed only on the intake side of the cylinder bore 11.

[0019] The first embodiment has the following advantageous effects. In the cylinder block 10 according to the present embodiment, in which the reinforcing member 15 is fitted in the recesses 12a, 13a, as long as the recesses 12a, 13a are formed appropriately facing each other across the water jacket 14, the reinforcing member 15 may be prevented from being too tight to be inserted into the recesses 12a, 13a or from falling off in the water jacket 14 even if there is variation of width dimension of the water jacket 14. That is, the cylinder block 10 according to the present embodiment allows the reinforcing member 15 to be mounted securely across the water jacket 14 while relaxing the tolerance of the dimension of the water jacket 14.

[0020] To obtain the above effects, the recess such as 12a, 13a may be formed in at least either one of the outer periphery of the bore wall 12 and the inner periphery of the outer wall 13. However, in the present embodiment, in which the paired recesses 12a, 13a are formed at the respective top edges of the outer periphery of the bore wall 12 and the inner periphery of the outer wall 13 so as to face each other across the water jacket 14, the reinforcing member 15 may be held securely across the water jacket 14 at the recesses 12a, 13a of the cylinder block 10.

[0021] Although the provision of the reinforcing member 15 is advantageous in the improvement of the rigidity of the cylinder block 10 and hence suppresses the deformation of the cylinder block 10, the cooling performance of the cylinder block 10 may be decreased because the reinforcing member 15 partially blocks the flow of cooling water in the water jacket 14. In the present embodiment, the reinforcing member 15 is provided only on the thrust side of the cylinder bore 11, against which the piston 50 is pressed more strongly during the explosion stroke of the engine body 1 in contact with the bore wall 12. Such structure enhances the rigidity of the cylinder block 10 on the thrust side that is easy to be deformed and smoothen the flow of cooling water in the water jacket 14 on the anti-thrust side that is hard to be deformed, so that deterioration cooling performance is suppressed.

[0022] In the engine body 1 according to the present embodiment, the intake port 21 is formed on the thrust side of the cylinder bore 11 and the exhaust port 22 is formed on the anti-thrust side. The engine body 1 tends to become higher temperature in the anti-thrust side where the exhaust port 22 is formed due to the influence of high temperature exhaust gas. According to the present embodiment, however, the reinforcing member 15 provided on the thrust side opposite from the anti-thrust side and, therefore, the temperature rise on the exhaust side of the engine body 1 can be reduced effectively.

Second embodiment

[0023] The following will describe a second embodiment according to the present invention with reference to FIG. 3. The same reference numerals will be used to denote those components or elements which correspond to the counterparts of the first embodiment and the description or the advantageous effects thereof will not be reiterated.

[0024] In the cylinder block 10 according to the second embodiment, the reinforcing member 15 is provided not only on the thrust side of the cylinder bore 11, but also on the anti-thrust side. The provision of the reinforcing member 15 on both the thrust and anti-thrust sides can improve the rigidity of the cylinder block 10 in both thrust and anti-thrust directions and suppress the deformation of the cylinder block 10 more effectively.

Third embodiment

[0025] The following will describe a third embodiment according to the present invention with reference to FIGS. 4A and 4B. The same reference numerals will be used to denote those components or elements which correspond to the counterparts of the first and the second embodiments and the description and the advantageous effects thereof will not be reiterated.

[0026] In the cylinder block 10 according to the third embodiment, the reinforcing members 15 are disposed in the same manner as in the second embodiment, but differs from the second embodiment in that a cooling fin 16 is mounted to the reinforcing member 15. The cooling fin 16 is made of a material such as copper that has a higher thermal conductivity than reinforcing member 15. The cooling fin 16 may be made of a bent copper plate and fixed to the reinforcing member 15 by a bolt. It is noted that according to the present embodiment, the material, shape, and method for mounting are changeable.

[0027] The structure in which the cooling fin 16 having a higher thermal conductivity than the reinforcing member 15 is mounted to the reinforcing member 15 locating in the water jacket 14 permits effective thermal exchange of the cooling fin 16 with cooling water thereby to cool the engine body 1 effectively.

[0028] The cooling fin 16 which is fixed between two adjacent reinforcing members 15 may be mounted to the reinforcing members 15 easily and held securely at the opposite ends thereof.

[0029] The present invention is not limited to the embodiments described above, but it may be modified into various alternative embodiments as exemplified below.

[0030] In the first, the second, and the third embodiments, the reinforcing member 15 is disposed at a position where the imaginary plane B passing through the axis A of the cylinder bore 11 and extending perpendicularly to the imaginary plane C and the water jacket 14 intersect each other. According to the present invention, however, the position of the reinforcing member 15 is not limited to the above.

[0031] From a point of view of enhancing the rigidity of the cylinder block 10 in the thrust and anti-thrust direction and suppressing the deformation of the cylinder block 10 in this direction effectively, the reinforcing member 15 should be disposed within the range of an angle θ of about 45 degrees about the center A and as measured from the imaginary plane B (shown FIG. 1), and preferably within an angle θ of about 30 degrees. As disclosed in the foregoing embodiments, the reinforcing member 15 should most preferably be disposed at a position corresponding to zero degree, or disposed on the imaginary plane B.

[0032] Although the reinforcing member 15 in the foregoing embodiments is formed in a rectangular parallelepiped shape, the reinforcing member 15 may be formed in any other shape. For example, the reinforcing member 15 may be formed in a cylindrical shape extending along the axis A of the cylinder bore 11 so that the recesses 12a, 13a having a curved shape are easily formed to fit to the reinforcing member 15 by drilling the cylinder block 10 from the upper direction.

[0033] In the first embodiment, the reinforcing member 15 is disposed only on the thrust side of the cylinder bore 11, and the intake port 21 and the exhaust port 22 are provided on the thrust side and the anti-thrust side, respectively. The exhaust port 22 and the intake port 21 may be provided on the thrust side and the anti-thrust side, respectively.

Claims

1. A cylinder block (10) comprising:

a bore wall (12) having at least one cylinder bore (11);

an outer wall (13) located outside an outer periphery of the bore wall (12); and

a water jacket (14) defined between the outer periphery of the bore wall (12) and an inner periphery of the outer wall (13), wherein the cylinder block (10) is an open-deck cylinder block (10) in which a top end of the water jacket (14) is opened,

characterized in that the outer periphery of the bore wall (12) and the inner periphery of the outer wall (13) have respective top edges at the top end of the water jacket (14), wherein at least one of the outer periphery of the bore wall (12) and the inner periphery of the outer wall (13) has at least one recess (12a, 13a) at the corresponding top edge, wherein the cylinder block (10) includes at least one reinforcing member (15) that is fitted in the at least one recess (12a, 13a) and covers part of the water jacket (14) that extends from the at least one recess (12a, 13a).

2. The cylinder block (10) according to claim 1, characterized in that the outer periphery of the bore wall (12) and the inner periphery of the outer wall (13) have respective recesses (12a, 13a) that are located on opposite sides of the at least one reinforcing member (15), wherein the at least one reinforcing member (15) is fitted in the recesses (12a, 13a) and covers part of the water jacket (14) between the recesses (12a, 13a).

3. The cylinder block (10) according to claim 1 or 2, characterized in that a cooling fin (16) is mounted to the at least one reinforcing member (15) to be located in the water jacket (14), the cooling fin (16) having a higher thermal conductivity than the at least one reinforcing member (15).

4. The cylinder block (10) according to claim 3, characterized in that the at least one reinforcing member (15) includes a plurality of reinforcing members (15), wherein the cooling fin (16) is extended between adjacent two of the reinforcing members (15).

5. The cylinder block (10) according to any one of claims 1 through 4, characterized in that the cylinder block (10) for an engine has a thrust side and an anti-thrust side that are opposite to each other with respect to the at least one cylinder bore (11), wherein the at least one reinforcing member (15) is provided only on the thrust side.

6. An engine body (1) comprising:

the cylinder block (10) according to claim 5; and

a cylinder head (20) disposed above the cylinder block (10) and having an intake port (21) and an exhaust port (22),

characterized in that the intake port (21) is formed on the thrust side of the cylinder block (10), wherein the exhaust port (22) is formed on the anti-thrust side.

Drawing