Abstract:
A cylinder block comprises a cylinder-barrel structure having a plurality of cylinder barrels; a water jacket outer wall structure disposed spaced from the cylinder-barrel structure to define therebetween a water jacket, the outer wall structure being fully spaced from said cylinder-barrel structure at the top surface of the cylinder block onto which top surface a cylinder head is to be secured, the outer wall structure including first and second side wall sections which are located opposite so as to interpose therebetween the cylinder-barrel structure; and a reinforcement member disposed to rigidly connect the first and second side wall sections in a manner to traverse said cylinder-barrel structure, thereby suppressing the vibration of the water jacket outer wall structure thus preventing noise emission therefrom.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a cylinder block of an internal combustion engine, and more particularly to an improvement in a cylinder block of the so-called open-deck type wherein a water jacket fully opens through the cylinder block top surface onto which a cylinder head is secured. 
     2. Description of the Prior Art 
     In connection with so-called open-deck type cylinder blocks, a water jacket outer wall is fully spaced from a cylinder-barrel structure at the cylinder block top surface onto which a cylinder head is secured, while the water jacket outer wall is securely connected at a lower block deck with the cylinder-barrel structure. Accordingly, the water jacket outer wall is not rigidly supported at the cylinder head top surface, so that the water jacket outer wall tends to readily vibrate, thereby emitting noise therefrom. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, a cylinder block comprises a cylinder-barrel structure having a plurality of cylinder barrels. A water jacket outer wall structure is disposed spaced from the cylinder barrel structure to define therebetween a water jacket. The water jacket outer wall structure being fully spaced from the cylinder-barrel structure at the top surface of the cylinder block onto which top surface a cylinder head is to be secured. The water jacket outer wall structure includes first and second side wall sections which are located opposite each other so as to interpose therebetween said cylinder-barrel structure. Additionally, a reinforcement member is disposed to rigidly connect first and second side wall sections of the water jacket outer wall structure in a manner to traverse the cylinder-barrel structure in which a part of the reinforcement member is secured to said cylinder-barrel structure. In the thus arranged engine, by virtue of the reinforcement member, the water jacket outer wall structure is greatly improved in rigidity while improving the torsional rigidity of the entire cylinder block. This greatly contributes to engine noise reduction and guards a head gasket from damage and breakage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the cylinder block according to the present invention will be more clearly appreciated from the following description taken in conjunction with the accompanying drawing in which like reference numerals designate like parts and elements, and in which: 
     FIG. 1 is a plan view of a conventional open-deck type cylinder block; 
     FIG. 2 is a vertical section view taken in the direction of arrows substantially along the line II--II; 
     FIG. 3 is a vertical section view of a preferred embodiment of a cylinder block in accordance with the present invention; 
     FIG. 4 is a fragmentary transverse section view taken in the direction of arrows substantially along the line IV--IV of FIG. 3; and 
     FIG. 5 is a perspective view of a reinforcement plate member used in the cylinder block of FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, a conventional cylinder block 1 will be described along with its major shortcomings. This conventional cylinder block 1 includes a cylinder-barrel structure 2 which is constructed of a row of cylinder barrels 2a-2d which are integrally connected with each other side-by-side. A water jacket 3 is formed around the cylinder barrel structure 2. A water jacket outer wall 4 located outside of the water jacket 3 is separate from the cylinder-barrel structure 2 at an upper block deck 5 onto which a cylinder head (not shown) is securely mounted; but is integrally connected to the cylinder barrel structure 2 at a section in the vicinity of a lower block deck 6. In such a cylinder block configuration, the water jacket 3 opens at or through the upper block deck 5, and therefore the thus arranged cylinder block is referred to as &#34;an open-deck type cylinder block&#34;. 
     The cylinder block of this type has been employed for the reason that the water jacket 3 can be readily formed by drawing out a metal die corresponding to the water jacket after casting. However, in such an open-deck type cylinder block, the water jacket outer wall 4 around the water jacket 3 is rigidly supported at the section in the vicinity of the lower block deck 6 but not supported at the upper block deck 5, and therefore the water jacket outer wall 4 tends to readily vibrate. This not only generates noise but also breaks down the head gasket (not shown) interposed between the upper block deck 5 and the cylinder head, thereby allowing the leakage of coolant and combustion gas. 
     In view of the above description of the conventional cylinder block arrangement, reference is now made to FIGS. 3, 4 and 5, wherein a preferred embodiment of a cylinder block of the present invention is illustrated by the reference numeral 10. The cylinder block 10 is, in this instance, of an automotive internal combustion engine and comprises a cylinder-barrel structure 12 which is constructed of a row of aligned cylinder barrels 12a which are integrally connected with each other side-by-side, at connecting sections C through which the neighboring cylinder barrels 12a, 12b are integral with each other as clearly shown in FIG. 4. A water jacket outer wall structure 14 is formed around the cylinder-barrel structure 12 but is located spaced from the cylinder-barrel structure 12 to define therebetween a water jacket 16. The water jacket outer wall structure 14 is separate or spaced from the cylinder-barrel structure 12 at a so-called upper block 18 onto which a cylinder head (not shown) is rigidly mounted, so that the water jacket 16 opens through the upper block deck 18. In this regard, this cylinder block 10 is of the open-deck type. It will be understood that the water jacket outer wall structure 14 is integrally connected to the cylinder-barrel structure 12 at a section in the vicinity of a so-called lower block deck 20. The water jacket outer wall structure 14 includes opposite side wall sections 14a,  14b between which the cylinder barrel structure 12 is located. 
     As shown, a reinforcement plate member 22 is disposed at each connecting section C in a manner to traverse the cylinder-barrel structure 12 and the opposite sections of the water jacket 16 to be connected to the opposite side wall sections 14a, 14b of the water jacket outer wall structure 14. The reinforcement plate member 22 is, in this instance, formed of steel plate and in generally of the rectangular shape. The reinforcement plate member 22 includes a flat main body 22a of the rectangular shape. The main body 22a is provided at its opposite vertical end portions with two flanges or bent portions 22a, 22b which have been already formed by bending, in the opposite directions, the two opposite vertical end edges of the plate member 22 in the flat state. The reinforcement plate member 22 is so located that its main body section 22a is perpendicular to an imaginary vertical plane containing the axes of cylinder barrels 12a. In this connection, the reinforcement plate member 22 is formed with a row of relatively large diameter circular openings 24 which are aligned along the center vertical line (not shown) of reinforcement plate member 22. The reinforcement plate member 22 is further formed with two rows of relatively small diameter circular openings 26A, 26B which two rows are positioned parallel with and opposite to each other with respect to the row of the relatively large diameter openings 24, so that the row of the openings 26A is positioned between the flange portion 22b and the row of openings 24 while the row of openings 26B is positioned between the other flange section 22b and the row of openings 24. 
     More specifically, the reinforcement plate member 22 has a vertically elongate central section S 1  which is located and embedded in the connecting section C of the cylinder-barrel structure 12. The reinforcement plate member 22 further has vertically elongate opposite end sections S 2  which are respectively located and embedded in the opposite side wall sections 14a, 14b of the cylinder-barrel structure 14. Additionally, vertically elongate two medium sections S 3  are positioned between the central section S 1  and the end sections S 2  and located in the water jacket 16. In this connection, the row of openings 24 are positioned at the central section S 1  ; the row of openings 26A are positioned at one of the medium sections S 3  while the other row of openings 26B are positioned at the other of the medium sections S 3  ; and the two flange sections 22b are positioned respectively at the end sections S 2 . 
     As will be understood from the above and FIGS. 3 and 4, the reinforcement plate member 22 is so disposed in the cylinder block 10 that the rows of openings 26A, 26B are located in the water jackets 16 so that a coolant passage is formed through the reinforcement plate member, and the row of openings 24 are located in the connecting section C of the cylinder-barrel structure 12 so that the openings 24 are filled with the material of the cylinder block 1, for example, aluminum alloy. In addition to this, the flange sections 22b formed at the opposite end parts are disposed or embedded in the opposite side wall sections 14a, 14b of the water jacket outer wall structure 14. The reference numeral 28 denotes bolt holes for head bolts (not shown) for securing the cylinder head onto the cylinder block 10. The reference numeral 30 denotes reinforcement ribs formed at the outer surface of the side wall sections 14a, 14b of the water jacket outer wall structure 14. 
     While only one reinforcement plate member 22 has been shown and described, it will be understood that a plurality of the reinforcement plate members 22 are used at similar positions and in similar manner as shown in FIGS. 3 and 4. It will be appreciated in this embodiment, that by suitably selecting the diameter and the number of the above-mentioned openings 24, 26A, 26B, the flow amount of engine coolant can be controlled while maintaining temperature distribution of various engine parts at an appropriate condition. 
     The production method of the above-described cylinder block 10 will be discussed. Firstly, a plurality of the reinforcement plate members 22 which have been already produced are inserted in predetermined positions to form a shell mold (not shown) or the like. Thereafter, molten metal of aluminum alloy or the like is poured into the mold so as to obtain the casting of the cylinder block 10. Accordingly, the opposite side wall sections 14a, 14b are securely connected with the central cylinder-barrel structure 22 by the reinforcement plate members 22 as shown in FIGS. 3 and 4. In order to accomplish inserting the reinforcement plate members 22, slits are formed at a metal die (not shown) corresponding to the water jacket 16, and the shell mold is formed upon inserting the reinforcement plate members 22 into the slits, the metal die corresponding to the water jacket 16 being drawn out after pouring the molten metal. This facilitates the proper location of the reinforcement plate members 22. In such casting of the cylinder block 10, it is preferable that the reinforcement plate members 22 are plated with metal materials, such as zinc, liable to be familiar with the material, such as aluminum alloy, of the cylinder block 10, thereby making complete the pouring of the molten metal while exhibiting rust-preventing and anticorrosion effect. 
     As appreciated from the above, according to the present invention, the cylinder block outer walls are securely connected with the centrally located cylinder-barrel structure by means of the reinforcement plate members each of which traverses the cylinder-barrel structure and is embedded in the side wall sections of the water jacket outer wall structure. Therefore, the rigidity of the water jacket outer wall structure is greatly improved, thereby decreasing lateral or open-and-close movement vibration of the outer wall structure while noticeably improving the tortional rigidity of the entire cylinder block. This effectively reduces total engine noise. Additionally, since the water jacket outer wall structure can be suppressed in its movement, the head gasket interposed between the cylinder head and cylinder block is effectively guarded from its damage or breakage.