Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
2001-10-03
2003-03-11
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C123S041440, C123S041740, C123S041100
Reexamination Certificate
active
06530356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an engine block structure for a reciprocating engine, and, in more particularly, to a structure for a cylinder block of a multi-cylinder engine block that is provided with a water jacket on opposite sides of a raw of cylinders and oil return means for returning an oil for lubrication to oil source means from sliding parts and mechanisms.
2. Description of Related Art
There have been known various multi-cylinder reciprocating engines. Such an engine needs lubrication for the purposes of reducing wear and frictional losses of sliding parts of the engine, improving cooling efficiency of the sliding parts and dispersing impact pressure on the sliding parts. Specifically, an engine oil in an oil pan is sucked up by an oil pump and filtered by an oil filter, it is distributed to a main oil gallery in a cylinder block. The engine oil is distributed as a lubrication oil to sliding parts such as a crankshaft and pistons and mechanisms including sliding parts such as a valve drive mechanism installed to a cylinder head for cooling and lubrication of the sliding parts. The lubrication oil seeps out of the sliding parts and drops and then returns into the oil pan. The lubrication oil distributed to the crankshaft and the pistons escapes from sliding parts of the crankshaft and the pistons and seeps out of the sliding parts and drops directly to the oil pan. However, the lubrication oil distributed to, for example, the valve drive mechanism escapes from sliding parts such as camshafts and tappets and drops on a middle deck of the cylinder head. Then, the lubrication oil flows on the middle deck of the cylinder head and returns to the oil pan through oil return passages extending in both cylinder head and cylinder block.
In the case of a front engine-front drive system that is the mainstream of compact cars, it is general to install a power train from an engine to a differential as one whole transversely in an engine compartment. On the other hand, there are cars employing rear drive systems that provide drivers with satisfactory steering feelings. Such a rear drive car has an engine installed longitudinally in an engine compartment. In light of these circumstances, engines are preferable to be installed in both types of cars with only small or miner changes in structure.
However, in general, while a transverse engine that is installed transversely in the engine compartment places a crankshaft in a horizontal transverse direction, a longitudinal engine that is installed longitudinally in the engine compartment places a crankshaft a little inclined rearward down in most cases because it is accompanied by a transmission behind the engine. That is, there is a difference in inclination between the transverse engine and the longitudinal engine. Accordingly, an adverse influence is exerted on a flow of a lubrication oil in the oil return passages due to the positional difference. For example, in the case where an engine is installed transversely in the engine compartment, in order to cause a lubrication oil to drop from the cylinder head all around without staying in the cylinder head and to return to the oil pan, it can be thought to arrange a plurality of oil return passages at proper intervals along a straight row of cylinders. However, if this engine is installed longitudinally in the engine compartment, the lubrication oil is apt to stay near the rear end of the engine. Stagnation of a lubrication oil flow that occurs due to a stay of the lubrication oil is possibly one of causes of seizure of the sliding parts due to breaking of oil films.
In this regard, it can be thought to provide the cylinder head and/or the cylinder block with additional oil return passages at their rear end portions. However, it is very hard for the cylinder block to have oil return passages having desired sizes and shapes at the rear end portion. This is because, in light of providing an entire power train with a sufficient rigidity, the additional oil return passages exert a rigid restraint on a structure of the rear end portion of the cylinder block in which a coupling mount to which a transmission is coupled is.
Further, some engine block has a cylinder block provided with a water jacket that surrounds a straight row of cylinders of an in-line cylinder engine. In this cylinder block, as disclosed in, for example, Japanese Unexamined Patent Publication No. 10-141154, the water jacket comprises two parts of water jacket, an intake side water jacket and an exhaust side water jacket, disposed on opposite sides of the straight row of cylinders, respectively, that are connected to each other at front and rear ends thereof by front and rear communication channels, respectively. Cooling water is introduced into the water jacket through one of the communication channels. A water pump that supplies the cooling water is disposed on one of opposite side walls of the cylinder block near front end of the cylinder block and driven by a crankshaft of the engine through a V-belt.
Generally, in the engine block, cooling water is discharged from the water pump and enters the water jacket through front end of either one part of the water jacket. It is not always easy to appropriately divide a cooling water stream into two parts for the intake side water jacket and the exhaust side water jacket. In this regard, the prior art cylinder block has a water guide passage formed separately from the front communication channel of the water jacket in a front end wall of the cylinder block. According to the prior art cylinder block, cooling water is directed to a front position of the cylinder block through the water guide passage and then introduced into both intake side water jacket and exhaust water jacket. This separate water guide passage makes the cylinder block large in overall length. In addition, although on behalf of providing reliable distribution of cooling water into the intake side water jacket and the exhaust side water jacket, because the prior art cylinder block causes the cooling water stream to sharply turn after a stay at an end of the water guide passage, the distribution of cooling water to the water jacket is hard to be smooth and, in consequence, there possibly occurs an increase in mechanical loss in driving the water pump.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an engine block structure for a reciprocating engine in which a cylinder block at a rear end portion is provided with oil return passages showing reliable oil returning performance.
It is another object of the present invention to provide an engine block structure for a reciprocating engine including a cylinder block provided with a water jacket surrounding a row of cylinders that has a shortened overall length.
It is another object of the present invention to an engine block structure for a reciprocating engine including a cylinder block provided with a water jacket surrounding a row of cylinders that provides improved performance of introducing and distributing cooling water into a water jacket on opposite sides of the row of cylinders.
The above objects are achieved by an engine block structure including an cylinder block that is provided with a plurality of oil return passages formed along the straight row of cylinders in each of opposite side walls of a cylinder block. Each of the oil return passage extends approximately straight from top to bottom of the cylinder block between each adjacent cylinders so as to reliably return a lubrication oil which is the basic performance of the oil return passage. In addition to the oil return passages, the cylinder block is provided with an auxiliary oil return passage that extends from the rear top of the cylinder block to the middle of the oil return passage with an effect of preventing the lubrication oil from staying in the oil return passage.
According to a preferred embodiment of the invention, in the engine block structure including a cylinder block that is provided with a straight row of
Inoue Yasushi
Matsue Arata
Mitsuhara Takashi
Ohtsuru Takashi
Shinohara Masako
Kamen Noah P.
Mazda Motor Corporation
Nixon & Peabody LLP
Studebaker Donald R.
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