JP5994940B2 - Cylinder head of internal combustion engine - Google Patents

Description

  The present invention relates to a cylinder head of an internal combustion engine.

  During operation of the internal combustion engine, the temperature of the cylinder head rises due to heat propagation from the combustion chamber and the exhaust manifold, and accordingly, the temperature of the wall surface of the intake port provided in the cylinder head also rises. When the wall surface temperature of the intake port rises and the temperature of the intake air flowing inside rises, knocking is likely to occur.

  Therefore, JP2008-144740A describes that an intake insert port having a heat insulating function is inserted into the intake port to prevent contact between the intake port wall surface and the intake air, thereby suppressing a rise in the temperature of the intake air.

  From the viewpoint of preventing heat transfer from the intake port wall surface to the intake air, the contact area between the intake port wall surface and the intake air should be as small as possible, that is, intake air from the intake manifold side end to the vicinity of the combustion chamber. It seems desirable to insert an insert port. However, when the tip of the intake insert port is heated by the burned gas blown back from the combustion chamber, heat is accumulated at the tip because the heat conductivity of the intake insert port is low. Heat exchange is not possible. On the other hand, when the intake insert port is not inserted, the heat received from the burnt gas can escape to the entire cylinder head, and the cylinder head is cooled by the cooling water. Is done. That is, if the intake insert port is inserted close to the combustion chamber, the tip temperature of the intake insert port becomes higher than the base material temperature of the cylinder head, and there is a possibility that the effect of suppressing the temperature rise of the intake air cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a cylinder head of an internal combustion engine having an intake port capable of obtaining an effect of suppressing a rise in temperature of intake air.

  According to an aspect of the present invention, a cylindrical member formed of a material having a lower thermal conductivity and a lower specific heat than the base material of the cylinder head, and an intake port that communicates the connection portion with the intake manifold and the combustion chamber A cylinder head of an internal combustion engine is provided that includes an intake insert port that functions as an intake port extending from a connection portion with the intake manifold in the intake port toward the combustion chamber.

  When the cylinder head is operated under a predetermined operating condition, the temperature of the combustion chamber side end portion of the intake insert port is equal to the base material temperature of the cylinder head at the combustion chamber side end portion of the intake insert port.

FIG. 1 is a cross-sectional view of a cylinder head 1 according to a first embodiment of the present invention. FIG. 2 is a graph showing the relationship between the distance from the opening on the combustion chamber side in the intake port and the intake port wall surface temperature. FIG. 3 is a diagram showing an effect of lowering the average temperature in the port by inserting the intake insert port. FIG. 4 is a diagram showing the effect of improving the charging efficiency by inserting the intake insert port. FIG. 5 is a diagram showing an effect of improving torque by inserting an intake insert port. FIG. 6 is a diagram showing the output improvement effect by inserting the intake insert port.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of a cylinder head 1 according to a first embodiment of the present invention. In the present embodiment, the base material of the cylinder head 1 is an aluminum alloy, but is not limited thereto, and may be another alloy.

  A concave combustion chamber 9 is provided on the lower surface of the cylinder head 1 in the drawing (hereinafter simply referred to as “lower surface”). Inside the cylinder head 1 are formed an intake port 3 and an exhaust port 4 having one end opened to the combustion chamber 9 and the other end opened to a side surface of the cylinder head 1 (hereinafter also referred to as a cylinder head side surface). An intake manifold 2 communicating with the intake port 3 is connected to a side surface of the cylinder head where the intake port 3 opens. An exhaust manifold communicating with the exhaust port 4 is connected to the side surface of the cylinder head where the exhaust port 4 opens, but is omitted in FIG.

  On the other hand, an intake valve 5 and an exhaust valve 6 are arranged at openings of the intake port 3 and the exhaust port 4 to the combustion chamber 9, respectively.

  A coolant passage 8 for cooling the cylinder head 1 is formed inside the cylinder head 1.

  A cylindrical intake insert port 7 made of a material having lower thermal conductivity and lower specific heat than the base material of the cylinder head 1 is inserted into the intake port 3, and the intake air is contained in the intake insert port 7. Pass the circumference side. That is, the intake insert port 7 functions as the intake port 3 while being inserted into the intake port 3. The range in which the intake insert port 7 is inserted will be described later.

  As a material for the intake insert port 7, resin, ceramic, or the like can be used. In the present embodiment, resin is used. Although not shown in FIG. 1, an air layer is provided between the outer periphery of the intake insert port 7 and the wall surface of the intake port 3.

  Next, the purpose of inserting the intake insert port 7 and the range of insertion will be described.

  During engine operation, the temperature of the cylinder head 1 rises as heat propagates from the combustion chamber 9. Although this temperature rise is suppressed by heat exchange with the coolant flowing through the coolant passage 8, the cylinder head 1 becomes higher than the intake air temperature. For this reason, the intake air receives heat from the wall surface of the intake port 3 and rises in temperature, leading to a decrease in filling efficiency and a deterioration in knock characteristics. Therefore, the intake insert port 7 is inserted into the intake port 3 in order to suppress heat transfer from the wall surface of the intake port 3 to the intake air.

  By the way, from the viewpoint of suppressing the transfer of heat from the wall surface of the intake port 3 to the intake air, it seems that it is desirable to cover the widest possible range of the intake port 3 with the intake insert port 7. However, if the entire area of the intake port 3 is covered by the intake insert port 7, for example, when the intake valve 5 is operated at a valve timing having a valve overlap period, the intake insert is caused by the burned gas blown back from the combustion chamber 9 when the intake valve 5 is opened. Port 7 is heated. Since the intake insert port 7 has a low thermal conductivity, it is difficult for heat to diffuse from the heated portion to other portions, and heat exchange with the cylinder head 1 is not possible. For this reason, heat tends to accumulate in the portion heated by the burned gas near the combustion chamber 9, and the temperature rises every time the burned gas blows back. If the temperature of the intake insert port 7 rises, the temperature of the intake air passing through the inside will also rise. That is, when the intake insert port 7 is inserted close to the combustion chamber 9, the portion near the combustion chamber 9 of the intake insert port 7 becomes higher than the base material temperature of the cylinder head 1 due to the blow-back of the burned gas. There is a risk of temperature rise.

  On the other hand, when the intake insert port 7 is not inserted, the base material of the cylinder head 1 is an aluminum alloy having excellent heat conductivity. Therefore, even if a part of the intake port 3 is heated by burned gas, the heat is generated in the cylinder. It diffuses to other parts of the head 1. The temperature of the cylinder head 1 is increased by the heat from the combustion chamber 9 but is cooled by the coolant, so that the upper limit value of the wall surface temperature of the intake port 3 is maintained even if heating with the burned gas is repeated. Is suppressed.

  That is, the effect of suppressing the temperature rise of the intake air due to the insertion of the intake insert port 7 is obtained when the temperature of the intake insert port 7 does not become higher than the base material temperature of the cylinder head 1. Therefore, as described below, a range for inserting the intake insert port 7 is set.

  FIG. 2 shows the relationship between the distance from the opening on the combustion chamber 9 side and the wall surface temperature in contact with the intake air (hereinafter also simply referred to as the wall surface temperature) when the intake insert port 7 is inserted and not inserted. The vertical axis represents the wall surface temperature, and the horizontal axis represents the distance from the combustion chamber side opening.

  The distance from the combustion chamber side opening is the distance along the axis C of the intake port 3. The wall surface temperature when the intake insert port 7 is inserted (also referred to as having an intake insert port) is the temperature of the inner peripheral surface of the intake insert port 7 and is not inserted (also referred to as having no intake insert port). The temperature is the temperature of the base material of the portion constituting the intake port 3.

  Without the intake insert port 7, the combustion chamber side opening is the hottest, and the wall surface temperature gradually decreases as the distance from the combustion chamber side opening increases.

  On the other hand, even when the intake insert port 7 is provided, the wall surface temperature becomes higher as the position becomes closer to the combustion chamber 9. However, the opening on the intake manifold 2 side is lower in temperature than the case without the intake insert port 7, but as it approaches the combustion chamber 9, it approaches the wall surface temperature without the intake insert port 7 and from the combustion chamber side opening. When the distance becomes shorter than L1, the temperature becomes higher than that without the intake insert port 7. The reason why the temperature from the combustion chamber side opening nearer than L1 is higher than that without the intake insert port 7 is due to the above-described heating by the reburning of burned gas.

  Therefore, the intake insert port 7 is set so that the position of the distance L1 at which the wall surface temperature is the same with and without the intake insert port 7 is the end portion (hereinafter also referred to as the front end portion) on the combustion chamber 9 side. insert. That is, the range from the distance L1 to the intake manifold side opening is covered with the intake insert port 7.

  As a result, it is possible to avoid a situation in which the temperature of the intake air rises by inserting the intake insert port 7 for the range less than the distance L1, and the intake air by the intake insert port 7 for the range greater than the distance L1. A temperature rise suppression effect is obtained. That is, when the intake insert port 7 is provided, the temperature of the intake air flowing into the combustion chamber 9 is lower than that when the intake insert port 7 is not provided. As a result, effects such as improved filling efficiency and improved knock margin can be obtained.

  By the way, the burned-back amount of burned gas varies according to operating conditions such as engine load, rotation speed, and valve timing, and the wall surface temperatures of the intake port 3 and the intake insert port 7 also change according to the blow-back amount. Varies depending on the operating conditions.

  Therefore, in the present embodiment, the distance L1 under the operating condition in which knocking occurs without the intake insert port 7 is the distance from the combustion chamber side opening to the tip of the intake insert port 7, and the intake insert port 7 is inserted. Avoid knocking.

  The effect of suppressing the rise in the temperature of the intake air by inserting the intake insert port 7, that is, the allowance for improving the knock margin, varies depending on the cross-sectional area, length, shape of the intake port 3 and other specifications of the internal combustion engine. , “Operating conditions under which knocking occurs” are determined by conformance.

  The effect when the position of the tip portion of the intake insert port 7 is set as described above will be described.

  FIG. 3 is a diagram showing the relationship between the rotational speed of the internal combustion engine and the average temperature in the intake port 3 when the intake insert port 7 is provided and when the intake insert port 7 is not provided. The vertical axis represents the average temperature in the port, and the horizontal axis represents the rotational speed of the internal combustion engine. The reason why the average temperature in the port is used is that the effect of suppressing the increase in the temperature of the intake air by inserting the intake insert port 7 can be evaluated without measuring the temperature of the intake air flowing into the combustion chamber 9.

  As shown in FIG. 3, when the intake insert port 7 is provided, the average temperature in the port is lower in the entire rotational speed region than when the intake insert port 7 is not provided.

  FIG. 4 is a diagram showing the relationship between the rotational speed of the internal combustion engine and the charging efficiency when the intake insert port 7 is provided and when the intake insert port 7 is not provided. The vertical axis represents the charging efficiency, and the horizontal axis represents the rotational speed of the internal combustion engine.

  When the intake insert port 7 is provided, the charging efficiency is improved in almost the entire rotational speed region as compared with the case without the intake insert port 7. Specifically, an average of 1.5% is improved in the entire rotation speed region. This is because the intake air temperature is lowered over the entire rotational speed region by inserting the intake insert port 7.

  Moreover, the engine output is also improved by improving the charging efficiency. FIG. 5 shows the relationship between the torque of the internal combustion engine (crankshaft shaft torque) and the rotational speed, and FIG. 6 shows the relationship between the output of the internal combustion engine and the rotational speed. In either case, the horizontal axis represents the rotational speed, and the vertical axis represents the torque and the output, respectively.

  By inserting the intake insert port 7, the torque is improved by about 1.2% on average over the entire rotational speed region, and the maximum output is improved by about 1.1%.

  Further, since the knock margin is improved as the average temperature in the port decreases, the ignition timing can be advanced and the compression ratio can be increased. Thereby, a torque and an output can be improved more.

  As described above, according to the present embodiment, the following effects can be obtained.

  The intake insert port 7 has a lower thermal conductivity and a lower specific heat than the base material of the cylinder head 1. Then, during operation under an operating condition in which knocking occurs without the intake insert port 7, the temperature of the tip of the intake insert port 7 and the wall surface temperature of the intake port 3 at the position of the tip of the intake insert port 7, that is, the cylinder head 1 Is equal to the base metal temperature. Thereby, even when burnt gas blows back from the combustion chamber 9, the temperature of the intake insert port 7 can be prevented from becoming higher than the base material temperature of the cylinder head 1, so that the temperature rise of the intake air flowing into the combustion chamber 9 can be prevented. It is suppressed and the filling efficiency and the knock margin are improved.

  Further, by providing an air layer between the wall surface of the intake port 3 and the intake insert port 7, heat is hardly transmitted from the wall surface of the intake port 3 to the intake insert port 7, and suction by inserting the intake insert port 7 is performed. The effect of suppressing the temperature rise of air is further improved. By the way, even if the thermal conductivity is lower than that of the base material, the thermal conductivity does not become zero, and the temperature rises as time passes by being exposed to high-temperature exhaust gas. For this reason, as the heat capacity of the intake insert port 7 increases, the amount of heat radiation for lowering the temperature once increased increases, and the time for increasing the temperature of the intake port 3 may become longer. . However, the intake insert port 7 of this embodiment not only has a lower thermal conductivity than the base material, but also has a smaller specific heat so that heat is dissipated as soon as the temperature rises. 3 can be prevented from being raised.

(Second Embodiment)
In this embodiment, the basic configuration of the cylinder head 1 is the same as that of the first embodiment, but the method for positioning the tip of the intake insert port 7 is different from that of the first embodiment.

  In the present embodiment, the distance L1 when operating under the operating condition in which the wall surface temperature of the intake port 3 is the highest without the intake insert port 7 is from the combustion chamber side end to the front end of the intake insert port 7. Distance.

  The operating condition in which the wall surface temperature of the intake port 3 is the highest is an operating condition in which the burned gas blowback amount is maximized. Specifically, it is a case where the valve timing is the low rotation speed / low load region and the valve overlap period is maximum within the changeable range.

  The maximum value of the intake air temperature can be suppressed by setting the distance from the combustion chamber side end of the front end of the intake insert port 7 to the distance L1 under the operating condition in which the wall surface temperature of the intake port 3 is the highest. it can. As a result, similar to the first embodiment, effects such as improvement of filling efficiency and improvement of knock margin can be obtained.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  This application claims the priority based on Japanese Patent Application No. 2013-123605 for which it applied to Japan Patent Office on June 12, 2013, and all the content of this application is integrated in this specification by reference.

Claims (3)

An intake port that communicates the connection with the intake manifold and the combustion chamber;
A cylindrical member formed of a resin material having a lower thermal conductivity and a lower specific heat than the base material of the cylinder head, and extending from the connection portion with the intake manifold in the intake port toward the combustion chamber. An intake insert port that functions as an intake port;
In a cylinder head of an internal combustion engine comprising:
During operation under a predetermined operating condition, an average temperature of the combustion chamber side end portion of the intake insert port and an average temperature of the base material of the cylinder head at the combustion chamber side end portion position of the intake insert port are: A cylinder head of an internal combustion engine in which the position of the combustion chamber side end of the intake insert port is set to be equal. The cylinder head of the internal combustion engine according to claim 1,
The predetermined operating condition is a cylinder head of an internal combustion engine that is an operating condition in which knocking occurs. The cylinder head of the internal combustion engine according to claim 1,
The predetermined operating condition is a cylinder head of an internal combustion engine that is an operating condition in which the temperature of the end portion on the combustion chamber side of the intake insert port is highest.

Images