Cylinder head

Abstract

The cylinder head includes: an intake port; a low-temperature cooling water channel for circulating low-temperature cooling water; a high-temperature cooling water channel for circulating cooling water of a higher temperature than the cooling water flowing through the low-temperature cooling water channel; and a gas channel for recirculating a portion of blow-by gas or EGR gas to the intake port. The low-temperature cooling water channel is configured to include a first water jacket that covers at least one portion of the wall surface of the intake port on an intake-air upstream side relative to an opening end opening at a wall surface of the intake port from the gas channel.

Claims

1. A cylinder head for an internal combustion engine including two cooling water circulation systems in which temperatures of cooling water are different, comprising: an intake port; a low-temperature cooling water channel for circulating cooling water of a low temperature, a high-temperature cooling water channel for circulating cooling water of a higher temperature than cooling water flowing through the low-temperature cooling water channel; a gas channel for recirculating a portion of blow-by gas or EGR gas to the intake port; an opening end opening at a wall surface of the intake port from the gas channel; and a port injector provided in the intake port, wherein the low-temperature cooling water channel is configured to include a first water jacket covering at least one portion of the wall surface of the intake port, the at least one portion being located on an intake-air upstream side relative to the opening end, wherein the opening end is provided on an intake-air upstream side relative to a spray region of fuel from the port injector.

2. A cylinder head for an internal combustion engine including two cooling water circulation systems in which temperatures of cooling water are different, comprising: an intake port; a low-temperature cooling water channel for circulating cooling water of a low temperature; a high-temperature cooling water channel for circulating cooling water of a higher temperature than cooling water flowing through the low-temperature cooling water channel; a gas channel for recirculating a portion of blow-by gas or EGR gas to the intake port; and an opening end opening at a wall surface of the intake port from the gas channel; wherein the low-temperature cooling water channel is configured to include a first water jacket covering at least one portion of the wall surface of the intake port, the at least one portion being located on an intake-air upstream side relative to the opening end, wherein the low-temperature cooling water channel is configured to include a second water jacket covering at least one portion of the wall surface of the intake port, the at least one portion being located on an intake-air downstream side relative to the opening end; and a straightening vane is provided inside the intake port to prevent gas introduced from the opening end into the intake port from contacting the wall surface covered by the second water jacket.

3. The cylinder head according to claim 2, wherein: the second water jacket is configured so as to cover a wall surface on a side facing the opening end; and the straightening vane is provided from the opening end to the wall surface covered by the second water jacket, so as to separate the intake port into a side of the wall surface covered by the second water jacket and a side of the opening end.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view illustrating a configuration of a cooling apparatus of a first embodiment;

(2) FIG. 2 is a cross-sectional view illustrating a cross section that is perpendicular to a longitudinal direction that includes a central axis of an intake valve insertion hole of a cylinder head;

(3) FIG. 3 is a flowchart illustrating a control flow of LT flow rate control;

(4) FIG. 4 is a cross-sectional view of a cylinder head for illustrating a modification of the first embodiment;

(5) FIG. 5 is a cross-sectional view of a cylinder head for illustrating a modification of the first embodiment;

(6) FIG. 6 is a cross-sectional view of a cylinder head for illustrating a modification of the first embodiment;

(7) FIG. 7 is a cross-sectional view of a cross section that is perpendicular to a longitudinal direction that includes a central axis of an intake valve insertion hole of a cylinder head of a second embodiment; and

(8) FIG. 8 is a cross-sectional view of a cylinder head for illustrating a modification of the second embodiment.

DETAILED DESCRIPTION

(9) Embodiments of the present invention are described hereunder with reference to the accompanying drawings. However, it is to be understood that even when the number, quantity, amount, range or other numerical attribute of an element is mentioned in the following description of the embodiments, the present invention is not limited to the mentioned numerical attribute unless it is expressly stated or theoretically defined. Further, structures or steps or the like described in conjunction with the following embodiments are not necessarily essential to the present invention unless expressly stated or theoretically defined.

(10) First Embodiment

(11) 1. Configuration of Cooling Apparatus

(12) An internal combustion engine of the present embodiment is a water-cooled engine (hereunder, referred to as simply engine) that is cooled by cooling water. The cooling water for cooling the engine is circulated between the engine and a radiator by a cooling water circulation system (cooling water circulation circuit). The cooling water is supplied to both a cylinder block and a cylinder head that constitute the main body of the engine. The configuration of a cooling apparatus of the engine of the present embodiment is described hereunder.

(13) FIG. 1 is a view illustrating the configuration of the cooling apparatus of the present embodiment. The cooling apparatus of the present embodiment includes two cooling water circulation systems 10 and 30 that supply cooling water to an engine 2. Supply of cooling water is performed with respect to both of a cylinder block 6 and a cylinder head 4 of the engine 2. Each of the two cooling water circulation systems 10 and 30 is an independent closed loop, and the temperatures of the cooling water circulated through the respective circulation systems can be made to differ from each other. Hereunder, the cooling water circulation system 10 in which cooling water of a relatively low temperature circulates is referred to as LT cooling water circulation system, and the cooling water circulation system 30 in which cooling water of a relatively high temperature circulates is referred to as HT cooling water circulation system. Further, cooling water that circulates through the LT cooling water circulation system 10 is referred to as LT cooling water, and cooling water that circulates through the HT cooling water circulation system 30 is referred to as HT cooling water. Note that, LT is an abbreviation of low temperature and HT is an abbreviation of high temperature.

(14) The LT cooling water circulation system 10 includes an in-head LT cooling water channel 12 that is formed inside the cylinder head 4, and an in-block LT cooling water channel 14 that is formed inside the cylinder block 6. The in-head LT cooling water channel 12 is provided in the vicinity of an intake port 8. In FIG. 1, four intake ports 8 that are the intake ports for four cylinders are shown. The in-head LT cooling water channel 12 extends in the direction of a crankshaft of the engine 2, along the bottom surface of the intake ports 8 of the respective cylinders. The in-block LT cooling water channel 14 is provided so as to surround a portion in which a flow of intake air is particularly liable to collide against an upper portion of the cylinder. The sensitivity of the temperature of the intake port 8 and an intake valve and also a wall surface temperature of the upper portion of the cylinder with respect to knocking is high. Hence, by cooling the aforementioned parts in a concentrated manner by means of the in-head LT cooling water channel 12 and the in-block LT cooling water channel 14, the occurrence of knocking in a high-load region can be effectively suppressed. Note that, the in-head LT cooling water channel 12 and the in-block LT cooling water channel 14 are connected through an opening formed in a mating surface between the cylinder head 4 and the cylinder block 6.

(15) A cooling water inlet and a cooling water outlet that communicate with the in-head LT cooling water channel 12 are formed in the cylinder head 4. The cooling water inlet of the cylinder head 4 is connected to a cooling water outlet of an LT radiator 20 by a cooling water introduction pipe 16, and the cooling water outlet of the cylinder head 4 is connected to a cooling water inlet of the LT radiator 20 by a cooling water discharge pipe 18. The cooling water introduction pipe 16 and the cooling water discharge pipe 18 are connected by a bypass pipe 22 that bypasses the LT radiator 20. A three-way valve 24 is provided at a branching portion at which the bypass pipe 22 branches from the cooling water discharge pipe 18. An electric water pump 26 for circulating LT cooling water is provided downstream of a merging portion with the bypass pipe 22 in the cooling water introduction pipe 16. The discharge rate of the electric water pump 26 can be arbitrarily changed by adjusting the output of a motor. A temperature sensor 28 for measuring the temperature of LT cooling water (cooling water outlet temperature) that passes through the inside of the engine 2 is installed on the upstream side of the three-way valve 24 in the cooling water discharge pipe 18. In the present embodiment, the term temperature of LT cooling water refers to a cooling water outlet temperature that is measured by the temperature sensor 28.

(16) The HT cooling water circulation system 30 includes an in-block HT cooling water channel 34 that is formed inside the cylinder block 6, and an in-head HT cooling water channel 35 that is formed inside the cylinder head 4. In contrast to the aforementioned in-block LT cooling water channel 14 that is a locally provided cooling water channel, the in-block HT cooling water channel 34 constitutes a major portion of a water jacket that surrounds the periphery of a cylinder. The in-head HT cooling water channel 35 is provided from the vicinity of an exhaust port to the vicinity of an intake port. Note that, the in-head HT cooling water channel 35 and the in-block HT cooling water channel 34 are connected through an opening formed in the mating surface between the cylinder head 4 and the cylinder block 6.

(17) A cooling water inlet and a cooling water outlet that communicate with the in-block HT cooling water channel 34 are formed in the cylinder block 6. The cooling water inlet of the cylinder block 6 is connected to a cooling water outlet of a HT radiator 40 by a cooling water introduction pipe 36, and the cooling water outlet of the cylinder block 6 is connected to a cooling water inlet of the HT radiator 40 by a cooling water discharge pipe 38. The cooling water introduction pipe 36 and the cooling water discharge pipe 38 are connected by a bypass pipe 42 that bypasses the HT radiator 40. A thermostat 44 is provided at a merging portion at which the bypass pipe 42 merges with the cooling water introduction pipe 36. A mechanical water pump 46 for circulating HT cooling water is provided downstream of the thermostat 44 in the cooling water introduction pipe 36. The water pump 46 is connected through a belt to the crankshaft of the engine 2. A temperature sensor 48 for measuring the temperature of HT cooling water (cooling water outlet temperature) that passes through the inside of the engine 2 is installed upstream of a branching portion with the bypass pipe 42 in the cooling water discharge pipe 38. In the present embodiment, the term temperature of HT cooling water refers to a cooling water outlet temperature that is measured by the temperature sensor 48.

(18) As described above, in the HT cooling water circulation system 30, because the water pump 46 is driven by the engine 2, HT cooling water is always circulating while the engine 2 is operating. The temperature of the cooling water circulating through the HT cooling water circulation system 30 is automatically regulated by the thermostat 44. On the other hand, in the LT cooling water circulation system 10, since the electric water pump 26 is used, LT cooling water can be circulated or caused to stop circulating regardless of whether or not the engine 2 is operating. Further, the flow rate of circulating LT cooling water can be controlled by means of a drive duty applied to the electric water pump 26. In addition, the temperature of LT cooling water circulating through the LT cooling water circulation system 10 can be actively adjusted by actuating the three-way valve 24 or the electric water pump 26.

(19) Actuation of the three-way valve 24 and the electric water pump 26 of the LT cooling water circulation system 10 is performed by a control apparatus 80. The control apparatus 80 is a control apparatus of the cooling apparatus and at the same time is also a control apparatus that controls operation of the engine 2. The control apparatus 80 is configured to include as a main constituent an ECU (electronic control unit) that includes one or a plurality of CPUs and memories. The control apparatus 80 adjusts the temperature of the LT cooling water that flows through the in-head LT cooling water channel 12 or the in-block LT cooling water channel 14 to an appropriate temperature by actuating the electric water pump 26 to control the flow rate of the LT cooling water (hereunder, referred to as LT flow rate), and by actuating the three-way valve 24 to control the proportion of LT cooling water that bypasses the LT radiator 20.

(20) 2. Configuration of Cooling Water Channel formed in Cylinder Head

(21) As shown in FIG. 1, the in-head LT cooling water channel 12 through which LT cooling water that has a low temperature flows and the in-head HT cooling water channel 35 through which HT cooling water that has a high temperature flows are formed in the cylinder head 4. Hereunder, the configurations of these cooling water channels are specifically described referring to a cross-sectional view of the cylinder head 4.

(22) FIG. 2 is a cross-sectional view illustrating a cross section that is perpendicular to a longitudinal direction (direction of crankshaft) that includes a central axis of an intake valve insertion hole of the cylinder head. However, in FIG. 2, an intake valve and an exhaust valve are illustrated in an abbreviated form. A combustion chamber 104 having a pent-roof shape is formed in a cylinder block mating surface 4a that contacts against the underside of the cylinder head 4.

(23) As viewed from the side of the front end of the cylinder head 4, the intake port 8 opens in an inclined face on a right side of the combustion chamber 104. A connecting portion between the intake port 8 and the combustion chamber 104, that is, an opening end on the combustion chamber side of the intake port 8 is an intake opening that is opened and closed by an intake valve which is not illustrated in the drawing. Since two intake valves are provided for each cylinder, two intake openings of the intake port 8 are formed in the combustion chamber 104. The intake port 8 extends in an approximately straight line towards the combustion chamber 104 from an inlet that opens in a side face of the cylinder head 4, and branches into two branch ports along the way, with each of the branch ports connecting to an intake opening formed in the combustion chamber 104. A branch port 8L on the side of the front end of the engine in the longitudinal direction is illustrated in FIG. 2. Note that, the intake port 8 is a tumble flow generating port that can generate a tumble flow in the cylinder.

(24) As viewed from the side of the front end of the cylinder head 4, an exhaust port 103 opens in an inclined face on a left side of the combustion chamber 104. A connecting portion between the exhaust port 103 and the combustion chamber 104, that is, an opening end on the combustion chamber side of the exhaust port 103 is an exhaust opening that is opened and closed by an exhaust valve that is not illustrated in the drawing.

(25) In the cross section shown in FIG. 2, a region denoted by reference character 35a is a partial cross section of the in-head HT cooling water channel 35 shown in FIG. 1. Hereunder, the term in-head HT cooling water channel 35a is used when referring to the region denoted by reference character 35a, for example. The in-head HT cooling water channel 35a is disposed between a bottom surface 8b of the intake port 8 and the cylinder block mating surface 4a.

(26) In the cross section shown in FIG. 2, a region denoted by reference character 12a is a partial cross section of the in-head LT cooling water channel 12 shown in FIG. 1. The in-head LT cooling water channel 12 extends along the bottom surface 8b of the intake port 8 of each cylinder in the longitudinal direction of the cylinder head 4. Hereunder, the term first water jacket 12a is used when referring to the region denoted by reference character 12a, for example. The first water jacket 12a is provided so as to cover one part of the bottom surface 8b of the intake port 8.

(27) According to the above described configuration that is illustrated in FIG. 2, the intake port 8 can be effectively cooled by the first water jacket 12a through which the LT cooling water which has a lower temperature than the HT cooling water flows. By this means, intake air that flows through the intake port 8 can be efficiently cooled.

(28) 3. LT Flow Rate Control

(29) The control apparatus 80 controls the LT flow rate in order to cool the principal portions of each of the cylinder head 4 and the cylinder block 6 to an appropriate temperature. FIG. 3 is a flowchart illustrating a control flow of LT flow rate control that is performed by the control apparatus 80. The control apparatus 80 repeatedly executes a routine represented by this control flow at predetermined control periods that correspond to the clock speed of the ECU.

(30) First, the control apparatus 80 sets an LT target water temperature that is a target temperature of LT cooling water that flows through the in-head LT cooling water channel 12 or the in-block LT cooling water channel 14 (step S2).

(31) Next, the control apparatus 80 calculates an LT requested flow rate that is a requested value of the LT flow rate based on the LT target water temperature determined in step S2 (step S4). More specifically, the control apparatus 80 refers to a previously prepared map in which the LT target water temperature and the LT requested flow rate are associated, and calculates a feedforward term of the LT requested flow rate, and also calculates a feedback term of the LT requested flow rate based on a difference between the LT target water temperature and a current temperature (outlet temperature) of the LT cooling water that is measured by the temperature sensor 28.

(32) Next, the control apparatus 80 determines a drive duty of the electric water pump 26 based on the LT requested flow rate determined in step S4 (step S6). However, if a valve that adjusts the LT flow rate is provided inside the LT cooling water circulation system 10, the LT flow rate can also be adjusted by actuating the valve to adjust the opening degree thereof.

(33) Finally, the control apparatus 80 actuates the electric water pump 26 in accordance with the drive duty that is determined in step S6 to thereby cause LT cooling water to flow through the in-head LT cooling water channel 12 and the in-block LT cooling water channel 14 (step S8). By this means, the LT flow rate changes and the principal portions of each of the cylinder head 4 and the cylinder block 6 are cooled to an appropriate temperature.

(34) 4. Blow-By Gas Recirculation Apparatus

(35) The engine of the present embodiment includes a blow-by gas recirculation apparatus for recirculating blow-by gas that is generated inside the engine main body to an intake passage via a PCV passage. In this case, as described above, the wall surface of the intake port 8 that is covered by the first water jacket 12a is cooled by the LT cooling water. Therefore, when blow-by gas is introduced at a position that is on the intake-air upstream side relative to a portion of the wall surface that is covered by the first water jacket 12a, the blow-by gas contacts a portion of the wall surface that is covered by the first water jacket 12a and is cooled. Because fuel or oil is contained in the blow-by gas, condensed water containing fuel will be generated if the blow-by gas is cooled. If such condensed water circulates to the intake-air downstream side, the condensed water will vaporize upon colliding with an intake valve that is at a high temperature, and as a result deposits will build up.

(36) Therefore, the engine of the present embodiment is configured so that a location at which blow-by gas is recirculated into the intake passage is on the intake-air downstream side relative to the first water jacket 12a. More specifically, as shown in FIG. 2, an opening end 50a of a PCV passage 50 is connected at the intake-air downstream side relative to the first water jacket 12a that covers a portion of the bottom surface 8b of the intake port 8. According to this configuration, blow-by gas that passes through the PCV passage 50 and is introduced into the intake port 8 circulates to the intake-air downstream side together with intake air that flows through the inside of the intake port. By this means, because blow-by gas does not contact a portion of the wall surface of the intake port that is covered by the first water jacket 12a, it is possible to effectively suppress the occurrence of a situation in which blow-by gas is cooled and condenses.

(37) Note that, as shown in FIG. 2, a port injector insertion hole 52 for mounting a port injector is formed on a top surface 8a side of the intake port 8. The port injector insertion hole 52 intersects at an acute angle with the intake port 8, and opens into a port injector mounting portion 8c that is formed in an upward convexity on a top surface of a branching portion of the intake port 8. A port injector (not illustrated) that is inserted into the port injector insertion hole 52 projects a nozzle tip out from the port injector mounting portion 8c and injects fuel into the intake port 8. Consequently, if fuel injected from the port injector adheres to the wall surface of the intake port 8 at a location on the intake-air upstream side relative to the opening end 50a of the PCV passage 50, there is a risk that the fuel will flow to the intake-air downstream side and will block the opening end 50a.

(38) Therefore, it is preferable that the opening end 50a of the PCV passage 50 is provided so as to be on the intake-air upstream side relative to a spray region of fuel that is injected from the port injector. Note that, the term spray region used herein refers to a region in which fuel that is injected from the port injector disperses. By this means it is possible to effectively suppress the occurrence of a blockage of the PCV passage 50 that is caused by fuel injected from the port injector.

(39) In this connection, in the above described embodiment a configuration is adopted in which, in an engine equipped with a blow-by gas recirculation apparatus, the opening end 50a of the PCV passage 50 to the intake port 8 is provided at a position on the intake-air downstream side relative to the first water jacket 12a. However, an engine to which the present invention can be applied is not limited thereto, and the present invention may also be applied to an engine that is equipped with an EGR apparatus that recirculates a portion of exhaust gas as EGR gas to an intake passage. In this case, it is sufficient to adopt a configuration in which an opening end of the EGR passage for recirculating EGR gas to the intake passage is provided at a position on the intake-air downstream side relative to the first water jacket 12a. By this means, cooling by the first water jacket 12a of EGR gas that is introduced into the intake port from the EGR passage can be avoided, and hence a buildup of deposits that are caused by condensed water that contains fuel can be effectively suppressed. Note that this similarly applies to a second embodiment that is described later.

(40) Further, although in the foregoing embodiment a configuration is described in which the opening end 50a of the PCV passage 50 is connected to the bottom surface 8b of the intake port 8, a configuration may also be adopted in which the opening end 50a of the PCV passage 50 is connected to the top surface 8a of the intake port 8. FIG. 4 is a cross-sectional view of a cylinder head for illustrating a modification of the first embodiment. Note that, similarly to FIG. 2, FIG. 4 illustrates a cross section that is perpendicular to a longitudinal direction including a central axis of an intake valve insertion hole 107. Further, elements in FIG. 4 that are common with the configuration shown in FIG. 2 are denoted by the same reference characters, and a description thereof is omitted. In a cylinder head 60 of the modification shown in the present view, an opening end 62a of a PCV passage 62 is connected to the top surface 8a of the intake port 8. The opening end 62a is provided at a position that is on the intake-air downstream side relative to the first water jacket 12a. According to this configuration, since cooling of introduced blow-by gas by the first water jacket 12a can be avoided, a buildup of deposits caused by condensed water containing fuel can be effectively suppressed.

(41) In the foregoing embodiment, a configuration of the first water jacket 12a that covers a portion on the bottom surface 8b side of the intake port 8 is described. However, the configuration of the first water jacket 12a is not limited thereto, and as long as the first water jacket 12a is provided so as to cover a portion of the wall surface that is located on the intake-air upstream side relative to the opening end 50a, the first water jacket 12a may be configured so as to cover a portion on the top surface 8a side of the intake port 8.

(42) Further, as long as the first water jacket 12a is provided so as to cover a portion of the wall surface that is located on the intake-air upstream side relative to the opening end 50a, it is not necessary for all of the first water jacket 12a to be located on the intake-air upstream side relative to the opening end 50a. FIG. 5 and FIG. 6 are cross-sectional views of cylinder heads for illustrating modifications of the first embodiment. Similarly to FIG. 2, FIG. 5 and FIG. 6 each illustrate a cross section that is perpendicular to a longitudinal direction including a central axis of the intake valve insertion hole 107. As illustrated by the configuration of a cylinder head 64 of the modification shown in FIG. 5, the first water jacket 12a may also be provided on the bottom surface 8b side of the intake port 8 so as to cover a portion of the wall surface that extends from the intake-air upstream side to the intake-air downstream side of the opening end 50a. Further, as illustrated by the configuration of a cylinder head 65 of the modification shown in FIG. 6, the first water jacket 12a may also be configured to include a channel that passes through a region between the intake valve insertion hole 107 and the top surface 8a of the intake port 8, in addition to a channel that covers one portion of the wall surface that is on the intake-air upstream side of the opening end 50a.

(43) In addition, with respect to the portion of the in-head LT cooling water channel 12, preferably a configuration is adopted in which the first water jacket 12a covers only one portion of the wall surface on the intake-air upstream side of the opening end 50a as shown in FIG. 2, and in which covering of the wall surface on the intake-air downstream side of the opening end 50a is avoided. According to this configuration, it is possible to suppress to the maximum the cooling of blow-by gas that is introduced from the opening end 50a.

(44) Note that, in the cylinder head of the first embodiment that is described above, the in-head LT cooling water channel 12 corresponds to low-temperature cooling water channel of the first aspect of the present invention, the in-head HT cooling water channel 35 corresponds to high-temperature cooling water channel of the first aspect of the present invention, the PCV passage 50 or the EGR passage corresponds to gas channel of the first aspect of the present invention, the opening end 50a or the opening end of the EGR passage corresponds to opening end of the first aspect of the present invention, and the first water jacket 12a corresponds to first water jacket of the first aspect of the present invention.

(45) Second Embodiment

(46) Next, a second embodiment of the present invention will be described using the drawings. The basic configuration of a cylinder head of the second embodiment is the same as that of the cylinder head of the first embodiment except that in the second embodiment a configuration including a straightening vane that is described later and the positional relation between the opening end of the PCV passage and the in-head LT cooling water channel are different from the first embodiment. Therefore, with respect to the other basic configuration of the cylinder head of the second embodiment excluding the aforementioned differences, the description of the basic configuration of the cylinder head of the first embodiment is incorporated as it is into the description of the second embodiment and a duplicate description thereof is not provided here. Hereunder, the characteristic configuration of the cylinder head of the second embodiment is described. The following description is made using cross-sectional views that are perpendicular to a longitudinal direction that includes the central axis of the intake valve insertion hole 107, similarly to FIG. 2. Further, in each of the drawings, elements that are common with elements of the first embodiment are denoted by the same reference characters.

(47) FIG. 7 is a cross-sectional view that is perpendicular to a longitudinal direction including a central axis of an intake valve insertion hole of a cylinder head of the second embodiment. In a cylinder head 70 illustrated in FIG. 7, an opening end 72a of a PCV passage 72 is connected to the top surface 8a of the intake port 8. Further, a second water jacket 12b that is a portion of the in-head LT cooling water channel 12 is provided on the bottom surface 8b side of the intake port 8 that is a side that faces the opening end 72a. The second water jacket 12b is configured so that a portion thereof is located further on the downstream side than the opening end 72a of the PCV passage 72. In addition, a straightening vane 74 for isolating a space on the top surface 8a side and a space on the bottom surface 8b side from each other is provided inside the intake port 8. The straightening vane 74 is a flat plate that is disposed along the direction of the flow of intake air, and is set to a length that isolates the aforementioned spaces from each other in a region extending from an intake-air upstream side end of the second water jacket 12b to an intake-air downstream side end thereof. Note that, the straightening vane 74 may be fixed inside the intake port 8, or may be rotatably fixed to a shaft that is parallel to the longitudinal direction of the cylinder head that is provided inside the intake port 8 and configured to also have a function that is capable of controlling the strength of a tumble flow by adjustment of a rotational angle thereof.

(48) According to the configuration shown in FIG. 7, blow-by gas that passes through the PCV passage 72 and is introduced from the opening end 72a into the intake port 8 circulates to the intake-air downstream side together with intake air that flows through the inside of the intake port. Because the space on the opening end 72a side and the space on the second water jacket 12b side are isolated from each other by the straightening vane 74, blow-by gas that is introduced into the intake port 8 from the opening end 72a is prevented from contacting a portion of the wall surface that is covered by the second water jacket 12b. By this means, the occurrence of a situation in which blow-by gas is cooled and condenses can be effectively suppressed.

(49) In this connection, although in the above described second embodiment the straightening vane 74 is set to a length that isolates the aforementioned spaces in a region from an intake-air upstream side end of the second water jacket 12b to an intake-air downstream side end thereof, the configuration of the straightening vane 74 is not limited thereto. That is, the shape and arrangement and the like thereof are not particularly limited as long as the configuration prevents blow-by gas that passes through the PCV passage 72 and is introduced from the opening end 72a into the intake port 8 from contacting a portion of the wall surface that is covered by the second water jacket 12b.

(50) Further, although in the foregoing second embodiment a configuration is described in which the opening end 72a of the PCV passage 72 is connected to the top surface 8a of the intake port 8, a configuration may also be adopted in which the opening end 72a of the PCV passage 72 is connected to the bottom surface 8b of the intake port 8. FIG. 8 is a cross-sectional view of a cylinder head for illustrating a modification of the second embodiment. Note that FIG. 8 illustrates a cross section that is perpendicular to a longitudinal direction that includes the central axis of the intake valve insertion hole 107, similarly to FIG. 7. Further, elements in FIG. 8 that are common with elements in FIG. 7 are denoted by the same reference characters, and a description of such elements is omitted hereunder.

(51) In a cylinder head 90 of the modification illustrated in FIG. 8, an opening end 92a of a PCV passage 92 is connected to the bottom surface 8b of the intake port 8. Further, in the cross section illustrated in FIG. 8, a portion 35b of the in-head HT cooling water channel is arranged in a region that is near to a top portion of the pent roof of the combustion chamber 104 and that is a region that lies between a top surface 103a in the vicinity of the exhaust opening of the exhaust port 103 and the top surface 8a in the vicinity of the intake opening of the intake port 8. Note that, although the in-head HT cooling water channels 35a and 35b are separated in the cross section illustrated in FIG. 8, the in-head HT cooling water channels 35a and 35b are connected to form a single channel at a plurality of places in the longitudinal direction inside the cylinder head 4.

(52) In the cross section illustrated in FIG. 8, first water jackets 12a and 12c are provided on the intake-air upstream side of the opening end 92a. The first water jacket 12a is provided on the bottom surface 8b side of the intake port 8. The first water jacket 12c is provided on the top surface 8a side of the intake port 8. Further, in the cross section shown in FIG. 8, second water jackets 12d and 12e are provided on the intake-air downstream side of the opening end 92a. The second water jacket 12d is a channel that passes through a region between the intake valve insertion hole 107 and the top surface 8a of the intake port 8. The second water jacket 12e is a channel that passes through a region that is nearer to the center of the cylinder head 4 than the intake valve insertion hole 107. Note that, although the first water jackets 12a and 12c and the second water jackets 12d and 12e of the in-head LT cooling water channel 12 are separated in the cross section illustrated in FIG. 8, these water jackets 12a and 12c and water jackets 12d and 12e are connected to form a single water jacket at a plurality of places in the longitudinal direction inside the cylinder head 4.

(53) In addition, in the cross section illustrated in FIG. 8, a straightening vane 94 for isolating a space on the top surface 8a side and a space on the bottom surface 8b side from each other is provided inside the intake port 8. The straightening vane 94 is set to a length that isolates the aforementioned spaces from each other in a region from an intake-air upstream side end of the intake port 8 at which the first water jacket 12a is arranged to an intake-air downstream side end of the intake port 8 at which the second water jackets 12d and 12e are arranged. Note that, similarly to the straightening vane 74 shown in FIG. 7, the shape and arrangement and the like of the straightening vane 94 are not particularly limited as long as the configuration prevents blow-by gas that passes through the PCV passage 92 and is introduced from the opening end 92a into the intake port 8 from contacting a portion of the wall surface that is covered by the second water jackets 12d and 12e.

(54) According to the configuration illustrated in FIG. 8, blow-by gas that passes through the PCV passage 92 and is introduced from the opening end 92a into the intake port 8 circulates to the intake-air downstream side together with intake air that flows through the inside of the intake port. Because the space on the side of the opening end 92a and the space on the side of the second water jackets 12d and 12e are isolated from each other by the straightening vane 94, blow-by gas that is introduced from the opening end 92a into the intake port 8 is prevented from contacting a portion of the wall surface that is covered by the second water jackets 12d and 12e. By this means, even in a case where the in-head LT cooling water channel 12 is provided on both the intake-air upstream side and the intake-air downstream side of the opening end 92a, it is possible to effectively suppress the occurrence of a situation in which blow-by gas that is introduced into the intake port 8 is cooled and condenses.

(55) Note that, in the cylinder head of the second embodiment that is described above, the in-head LT cooling water channel 12 corresponds to low-temperature cooling water channel of the first aspect of the present invention, the in-head HT cooling water channel 35 corresponds to high-temperature cooling water channel of the first aspect of the present invention, the PCV passage 50 or EGR passage corresponds to gas channel of the first aspect of the present invention, the opening end 50a or opening end of the EGR passage corresponds to opening end of the first aspect of the present invention, and the first water jacket 12a corresponds to first water jacket of the first aspect of the present invention.

(56) Further, in the cylinder head of the second embodiment that is described above, the second water jackets 12b, 12d and 12e correspond to second water jacket in the fourth aspect of the present invention, and the straightening vanes 74 and 94 correspond to straightening vane of the fourth aspect of the present invention.

(57) Further, in the cylinder head of the second embodiment that is described above, the in-head LT cooling water channel 12 corresponds to low-temperature cooling water channel of the sixth aspect of the present invention, the in-head HT cooling water channel 35 corresponds to high-temperature cooling water channel of the sixth aspect of the present invention, the PCV passage 50 or EGR passage corresponds to gas channel of the sixth aspect of the present invention, the opening end 50a or opening end of the EGR passage corresponds to opening end of the sixth aspect of the present invention, and the first water jacket 12a corresponds to water jacket of the sixth aspect of the present invention.