1. Field of the Invention
The present invention generally relates to a cooling structure in an engine, in which cooling water from a water pump is supplied via a water jacket in a cylinder head to a water jacket in a cylinder block.
2. Discussion of the Relevant Art
There is a cooling structure in an engine known from Japanese Patent Application Laid-open No. 10-37799, in which a projection for making cooling water difficult to flow is formed in a portion of a water jacket defined to surround outer peripheries of a plurality of cylinders disposed in a row in a cylinder block so that the cooling water flows in substantially one direction toward the projection within the water jacket by supplying the water jacket from the water pump to one side of the projection, thereby enhancing the cooling effect.
In an engine of a so-called cylinder-head first cooling type, in which cooling water from a water pump is supplied via a water jacket in a relatively high-temperature cylinder head to a water jacket in a relatively low-temperature cylinder block, if the cooling water supplied to the cylinder head flows into the cylinder block before sufficiently cooling the cylinder head, there is a possibility that the cooling of the cylinder head is insufficient. In addition, if the cooling water does not flow smoothly in one direction in the water jacket in the cylinder block, there is a possibility that the cooling of the cylinder block is also insufficient.
The present invention has been accomplished with such problems in mind. It is thus an object of the present invention to enhance the cooling performance for the cylinder head and the cylinder block in the engine of the cylinder-head first cooling type.
In order to achieve the above object, according to a first embodiment of the present invention, there is proposed a cooling structure in an engine, in which cooling water from a water pump is supplied via a water jacket in a cylinder head to a water jacket in a cylinder block, wherein the water jacket in the cylinder head is defined to extend along opposite sides of a plurality of cylinders disposed in a row, and has a cooling-water inlet and a cooling-water outlet provided at lengthwise one end thereof and the lengthwise other end thereof, respectively. The water jacket in the cylinder block is annularly defined to surround outer peripheries of the plurality of cylinders disposed in the row, and is shielded at one point by a shield member, has a cooling-water inlet provided on one side of the shield member to communicate with the cooling-water outlet in the water jacket in the cylinder head, and has a cooling-water outlet provided in the other side of the shield member.
With the above structural arrangement, the cooling water from the water pump flows from the cooling-water inlet in the one end to the cooling-water outlet in the other end of the water jacket defined to extend along the opposite sides of the plurality of cylinders in the cylinder head. The cooling water is then supplied to the cooling-water inlet provided on one side of the shield member in the water jacket annularly defined in the cylinder block to surround the outer peripheries of the cylinders, and flows therefrom to the cooling-water outlet on the other side of the shield member. Therefore, the cylinder head having a relatively high temperature during operation of the engine is first cooled by a lower-temperature cooling water; and the cylinder block having a relatively low temperature is then cooled by the cooling water, whereby the cooling effect for the entire engine can be enhanced. More particularly, a substantially total amount of the cooling water flows over the entire region of the water jacket provided annularly in the cylinder block, leading to an enhancement in cooling effect for the cylinder block.
According to a second embodiment of the present invention, in addition to the arrangement of the first embodiment, in the water jacket in the cylinder block, its portion upstream in a direction of flow of the cooling water is disposed to extend along a side face of the cylinder block on an intake side, and its portion downstream in the direction of flow of the cooling water is disposed to extend along a side face of the cylinder block on an exhaust side.
With the above structural arrangement, the upstream portion of the water jacket provided annularly in the cylinder block is disposed to extend along the side face of the cylinder block on the intake side, and the downstream portion is disposed to extend along the side face of the cylinder block on the exhaust side. Therefore, the side face of the cylinder block on the intake side can be preferentially cooled, whereby a deterioration of intake efficiency can be minimized.
According to a third embodiment of the present invention, in addition to the arrangement of the first and second embodiments, the cooling-water outlet of the water jacket in the cylinder block communicates with a heater core through cooling-water passages defined in the cylinder block and the cylinder head.
With the above structural arrangement, the cooling water exiting from the cooling-water outlet of the water jacket in the cylinder block is supplied to the heater core through the cooling-water passages defined in the cylinder block and the cylinder head. Therefore, the cooling water which has cooled both the cylinder head and the cylinder block to obtain a sufficiently raised temperature, can be supplied to the heater core, thereby enhancing the heating effect.
According to a fourth embodiment of the present invention, in addition to the arrangement of the third embodiment, a portion of the cooling-water passage communicating with the heater core is used commonly as a cooling-water passage for supplying the cooling water to a radiator.
With the above arrangement, the cooling-water passage communicating with the heater core is partially used commonly as the cooling-water passage for supplying the cooling water to the radiator, which can contribute to an enhancement in space efficiency.
According to a fifth embodiment of the present invention, in addition to the structural arrangement of any of the first to fourth embodiments, the water jacket in the cylinder head and the cooling-water passage communicating with the heater core are connected to each other by a cooling-water passage having an orifice.
With the above structural arrangement, because the water jacket in the cylinder head and the cooling-water passage communicating with the heater core are connected to each other by the cooling-water passage having the orifice, when the engine is hot, even if the amount of the cooling water flowing in the radiator increases and the amount of the cooling water flowing in the heater core decreases, the heating ability can be maintained by supplying the cooling water from the water jacket in the cylinder head through the orifice directly to the heater core.
According to a sixth embodiment of the present invention, in addition to the structural arrangement of any of the first to fifth embodiments, the water jacket in the cylinder head and the water jacket in the cylinder block are put into communication with each other by communication bores defined between opposed portions of the adjacent cylinders.
With the above structural arrangement, because the water jackets in the cylinder head and the cylinder block are put into communication with each other by the communication bores defined between the opposed portions of the adjacent cylinders, the opposed portions of the adjacent cylinders liable to have a high temperature can be cooled, but also the flow rate of the cooling water flowing in the water jacket in the cylinder when the engine is cold, can be decreased to promote the warming-up of the engine.