Cylinder head structure of a top-injection internal combustion engine

Abstract

To arrange an ignition plug 52 and fuel system components (a fuel injection valve 51 and a common rail boss 56) without increasing width direction dimensions of a cylinder head 1 and a cam carrier 2.SOLUTION: A ladder shape cam carrier 2 is fixed to an upper surface of a cylinder head 1 and cam shafts 5, 6 are supported by the cam carrier 2. An injection valve opening 23 and a plug hole 24 are formed at a bottom wall part 25 of the cam carrier 2 between the cam shafts 5, 6. In the injection valve opening 23, a fuel injection valve 51 and a common rail boss 56 are disposed adjacent to each other in an anteroposterior direction of an internal combustion engine. The fuel injection valve 51 and the common rail boss 56 are fixed to the cylinder head 1 through the injection valve opening 23.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] This invention relates to a cylinder head structure of an internal combustion engine in which a ladder-shaped cam carrier is combined with a cylinder head, and particularly to a cylinder head structure of a direct injection type internal combustion engine provided with a fuel injection valve at the center of a cylinder.

Background Art

[0002] A cylinder head structure has been proposed in which a ladder-shaped cam carrier configured in a ladder shape is fixed to the upper surface of a cylinder head, and an intake camshaft and an exhaust camshaft are rotatably supported by this cam carrier. In this type of configuration, the cam carrier also functions as a cover that covers a so-called valve operating chamber, and does not include a general cylinder head cover.

[0003] Patent Document 1 discloses a ladder-shaped cam carrier that covers the upper surface of a cylinder head in a cover shape and rotatably supports two camshafts. This cam carrier is configured to have openings for inserting ignition plugs at positions above the center of the combustion chamber.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of a direct injection type internal combustion engine provided with a fuel injection valve at the center of a cylinder, in addition to an ignition plug, a fuel injection valve needs to be arranged in each cylinder. Since this fuel injection valve is arranged penetrating through the cam carrier, the widthwise dimensions of the cylinder head and the cam carrier tend to increase. In general, since the fuel injection valve is configured to be supported by a common rail, a structure for attaching this common rail to the cylinder head is also required.

[0006] Patent Document 1 does not disclose an appropriate arrangement of both the spark plug and the fuel injector in such a direct injection type internal combustion engine. [Means for solving the problem]

[0007] This invention is Cylinder head and, Two camshafts, one for the intake valve and one for the exhaust valve, A ladder-shaped cam carrier fixed to the top of the cylinder head and supporting the two camshafts mentioned above, A spark plug is positioned in the center of each cylinder, These spark plugs are each positioned adjacent to a fuel injector supported by a common rail, A cylinder head structure for an upward-injection type internal combustion engine, comprising: The above cam carrier includes, in the bottom wall between the two camshafts, an opening for a spark plug through which the spark plug is inserted, and a common rail boss and a fuel system opening through which the fuel injector is inserted. The spark plug opening and the fuel system opening are arranged adjacent to each other in the width direction of the internal combustion engine. The common rail boss and the fuel injector are arranged adjacent to each other in the front-to-back direction of the internal combustion engine. Occasionally, moreover, The ignition coil unit connected to the above-mentioned spark plug is supported in the opening for the spark plug, The common rail boss and the fuel injector are supported by the cylinder head without contacting the opening edge of the fuel system opening. . [Effects of the Invention]

[0008] According to this invention, the spark plug opening and the fuel system opening are adjacent to each other in the width direction of the internal combustion engine, and the common rail boss and fuel injector are adjacent to each other in the front-rear direction of the internal combustion engine within the fuel system opening. As a result, the overall layout is compact, and the cam carrier and cylinder head can be made smaller, especially in the width direction. [Brief explanation of the drawing]

[0009] [Figure 1] Front view of a cylinder head with a cam carrier. [Figure 2] Plan view of the cam carrier. [Figure 3] A diagram showing the underside of the cam carrier. [Figure 4] A diagram showing the top surface of the cylinder head corresponding to Figure 3. [Figure 5] A diagram illustrating the main components of the cam carrier and cylinder head, viewed from above. [Figure 6] Cross-sectional view of the cam carrier and cylinder head. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of this invention will be described in detail with reference to the drawings. Figure 1 is a front view showing the cylinder head 1 of a top-injection type internal combustion engine according to this invention together with the cam carrier 2. The cylinder head 1 is integrally cast using a metal material, such as an aluminum alloy, and is mounted on the upper surface of the cylinder block 3. The internal combustion engine of this embodiment is a three-cylinder in-line spark-ignition internal combustion engine, a so-called gasoline engine, which is mounted in a so-called transverse position at the front of the vehicle. When mounted on the vehicle, the cylinder center axis is generally vertical, and therefore Figure 1 generally corresponds to the position when mounted on the vehicle.

[0011] Furthermore, the internal combustion engine of the embodiment has a pent-roof type combustion chamber equipped with a spark plug and a fuel injection valve in the center of the combustion chamber, as will be described later, and each cylinder is equipped with a pair of intake valves and a pair of exhaust valves.

[0012] The cylinder head 1 includes an intake camshaft 5 for intake valves and an exhaust camshaft 6 for exhaust valves. The cam carrier 2 is configured in a cover shape that covers the upper surface opening of the cylinder head 1, and is joined and fixed to the upper surface of the cylinder head 1 via a suitable sealing member such as a liquid gasket. The cam carrier 2 has an intake-side camshaft bearing portion 11 and an exhaust-side camshaft bearing portion 12 that form a substantially semi-circular shape toward the lower surface, and rotatably supports the intake camshaft 5 and the exhaust camshaft 6 between the cam brackets 13 and 14 that are attached to face these camshaft bearing portions 11 and 12, respectively.

[0013] As shown in FIG. 1, as a height position along the cylinder center axis, the intake camshaft 5 is arranged at a relatively lower position compared to the exhaust camshaft 6. Correspondingly, the height position of the upper edge portion of the cam carrier 2 that covers the upper sides of the respective camshafts 5 and 6 is also configured such that the intake camshaft 5 side is lower than the exhaust camshaft 6 side. The internal combustion engine of one embodiment is mounted in the engine room at the front of the vehicle in such a direction that the intake camshaft 5 side is the front of the vehicle and the exhaust camshaft 6 side is the rear of the vehicle. Therefore, the clearance between the engine hood of the vehicle (indicated by the virtual line L) that is inclined so that the front end portion is at a lower position is appropriate on both the intake camshaft 5 side and the exhaust camshaft 6 side.

[0014] As shown in FIG. 2, the cam carrier 2 of one embodiment has a ladder-shaped configuration in which two camshaft accommodating portions 21 and 22 that extend细长ly in the cylinder bank direction are connected to each other at the position between the cylinders. At three locations corresponding to the cylinder positions in the cylinder bank direction, relatively large injection valve openings 23 are provided in the bottom wall portion 25 between the two camshaft accommodating portions 21 and 22, respectively. Also, plug holes 24 for inserting ignition plugs are formed in a cylindrical shape on the exhaust camshaft 6 side (the camshaft accommodating portion 22 side) rather than the injection valve opening 23. The cam carrier 2 is integrally cast using a metal material such as an aluminum alloy.

[0015] The opening 23 for the injection valve corresponds to the "injection system opening" in the claims, and the plug hole 24 corresponds to the "opening for the ignition plug" in the claims. The opening 23 for the injection valve and the plug hole 24 corresponding to the same cylinder are arranged adjacent to each other in the width direction of the internal combustion engine.

[0016] FIG. 3 shows the configuration of the inner surface of the cam carrier 2, that is, the lower surface side. As shown in FIG. 3, the opening 23 for the injection valve has a so-called heart shape. The pointed end portion in the heart shape faces the intake valve side, and the recessed portion faces the exhaust valve side. The periphery of the heart-shaped opening 23 for the injection valve is surrounded by a seal surface 31 joined to the cylinder head 1 side via a seal member such as a liquid gasket. Further, the plug hole 24 opens in a perfect circle with a slightly inclined central axis and is arranged adjacent to the recessed portion in the heart shape of the opening 23 for the injection valve. The periphery of the plug hole 24 is surrounded by a seal surface 31A continuous with the seal surface 31 surrounding the opening 23 for the injection valve. Here, a relief portion 33 extending from the plug hole 24 toward the opening 23 for the injection valve is formed between the plug hole 24 and the opening 23 for the injection valve, and the seal surface 31A surrounds the peripheral edge portion of the relief portion 33 and the plug hole 24.

[0017] FIG. 4 shows the configuration of the upper surface of the cylinder head 1 facing the lower surface of the cam carrier 2 configured as shown in FIG. 3. On the upper surface side of the cylinder head 1, a heart-shaped recess 35 for the injection valve corresponding to the opening 23 for the injection valve is formed. The periphery of the recess 35 for the injection valve is surrounded by a seal surface 36 joined to the seal surface 31 on the cam carrier 2 side via a seal member such as a liquid gasket. An injection valve insertion hole 37 is formed in a slightly inclined state at approximately the center of the recess 35 for the injection valve. Further, inside the recess 35 for the injection valve, a mounting seat portion 39 provided with a screw hole 38 is formed at a position corresponding to the right shoulder portion of the heart shape. The seat surface, that is, the upper surface of this mounting seat portion 39 is provided at a height position slightly lower than the seal surface 36 surrounding the recess 35 for the injection valve. The mounting seat portion 39 and the injection valve insertion hole 37 are adjacent to each other in the front-rear direction (cylinder bank direction) of the internal combustion engine.

[0018] Furthermore, a cylinder head-side plug hole 40 (corresponding to the "spark plug hole" in the claim) is formed so as to be continuous with the plug hole 24 on the cam carrier 2 side. The area around this cylinder head-side plug hole 40 is surrounded by a sealing surface 36A that is continuous with the sealing surface 36 surrounding the injection valve recess 35. Between the cylinder head-side plug hole 40 and the injection valve recess 35, a cylinder head-side weight-reducing portion 41 is formed opposite to the weight-reducing portion 33 on the cam carrier 2 side, and the sealing surface 36A surrounds the peripheral edges of the cylinder head-side plug hole 40 and the cylinder head-side weight-reducing portion 41.

[0019] The sealing surfaces 31, 31A on the cam carrier 2 side and the sealing surfaces 36, 36A on the cylinder head 1 side have corresponding shapes and are joined together with a sealing material such as a liquid gasket sandwiched between them. In addition, the central axes of the plug holes 24, 40 and the central axis of the injection valve insertion hole 37 are inclined with respect to the cylinder central axis so that they form a V shape together.

[0020] Figure 5 shows the cylinder head 1 equipped with a cam carrier 2 and a fuel injector 51. Figure 6 is a cross-sectional view of the cam carrier 2 and cylinder head 1 cut along the cross-section passing through the fuel injector 51 and spark plug 52.

[0021] As shown in Figure 6, the spark plug 52 is integrated with an ignition coil unit 53, and the cylindrical portion 53a of the ignition coil unit 53 is fitted into and supported by the plug hole 24 of the cam carrier 2. The rectangular coil portion 53b at the top of the ignition coil unit 53 is exposed on the upper surface of the cam carrier 2 and is fixed to the cam carrier 2 by screws (not shown). The tip of the spark plug 52 reaches the combustion chamber 54 through the cylinder head side plug hole 40. In this way, the cylindrical portion 53a of the ignition coil unit 53 is fitted relatively tightly into the plug hole 24 of the cam carrier 2, which supports the upper part of the ignition coil unit 53 and suppresses the oscillation of the ignition coil unit 53.

[0022] The fuel injectors 51 have a so-called common rail configuration, and as shown in Figures 5 and 6, three fuel injectors 51 are mounted on a high-pressure fuel pipe, i.e., a common rail 55. The common rail 55 is a straight circular tube, and the upper end of each fuel injector 51 is supported by the common rail 55. The fuel injectors 51 are inserted through the injector opening 23 of the cam carrier 2, and their tips reach the combustion chamber 54 through the injector insertion hole 37 of the cylinder head 1.

[0023] The common rail 55, which extends in the longitudinal direction of the internal combustion engine, is equipped with common rail bosses 56 at three locations adjacent to the fuel injector 51 for attaching the common rail 55 to the internal combustion engine. Each common rail boss 56 is cylindrical and is fixed to a mounting seat 39 of the cylinder head 1 by a bolt 57 that passes through its center. The bolt 57 is screwed into a threaded hole 38 of the mounting seat 39. The common rail boss 56 is inserted through the injection valve opening 23 of the cam carrier 2. In particular, the fuel injector 51 and the common rail boss 56 that pass through the injection valve opening 23 are supported by the cylinder head 1 without contacting the opening edge of the injection valve opening 23 of the cam carrier 2. In this way, the common rail 55 and the fuel injector 51 are directly supported by the cylinder head 1, allowing the fuel system components (common rail 55 and fuel injector 51) to be firmly fixed to the cylinder head 1.

[0024] Furthermore, as shown in Figure 5, the fuel injector 51 is equipped with a connector 60 for connecting a harness. In a plan view as shown in Figure 5, this connector 60 is located on the opposite side of the common rail boss 56, with the center of the fuel injector 51 in between. As shown in Figure 5, the connector 60 is positioned at a location corresponding to the left shoulder of the heart shape of the injection valve opening 23 of the cam carrier 2 and the injection valve recess 35 on the cylinder head 1 side, and is located inside the injection valve recess 35 on the cylinder head 1 side, passing through the injection valve opening 23 of the cam carrier 2. By positioning the connector 60 on the opposite side of the common rail boss 56 in this way, the common rail boss 56 and the connector 60 (and the harness connected thereto) do not interfere with each other, and the connector 60 can be placed in a narrow space without being obstructed by the common rail 55 or the cam carrier 2.

[0025] As described above, with the configuration of this embodiment, the ignition plug 52 and fuel system components (common rail boss 56 and fuel injector 51) can be efficiently laid out in the limited space above the cylinder, which is achieved by arranging the ladder-shaped cam carrier 2 on the upper surface of the cylinder head 1. In particular, by arranging the fuel injector 51 and the common rail boss 56 adjacent to each other in the front-rear direction of the internal combustion engine and placing them within a common injection valve opening 23, when these and the ignition plug 52 are arranged adjacent to each other in the width direction of the internal combustion engine, the width dimension of the internal combustion engine does not increase, and the width dimensions of the cam carrier 2 and cylinder head 1 can be reduced.

[0026] Furthermore, the space between the cam carrier 2 and the cylinder head 1 is sealed via a sealing member such as a liquid gasket, thereby configuring the two camshaft housings 21 and 22 as enclosed spaces from the outside. However, the injection valve opening 23 and plug hole 24 provided between the two camshaft housings 21 and 22 are individually sealed, and the spark plug 52 and fuel system components are positioned through these openings, so no special sealing structure is required for the spark plug 52 or fuel system components.

[0027] The weight-reducing cutouts 33 and 41, provided on the cam carrier 2 side and the cylinder head 1 side in a corresponding manner, contribute to the weight reduction of the cam carrier 2 and cylinder head 1. Furthermore, the provision of these weight-reducing cutouts 33 and 41 causes the surrounding sealing surfaces 31A and 36A to expand in an elliptical shape. The two are sealed together via a sealing material such as a liquid gasket.

[0028] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, the present invention is not limited to a three-cylinder engine as in the above embodiment, but can be applied to an internal combustion engine with an appropriate number of cylinders. [Explanation of Symbols]

[0029] 1…Cylinder head 2…Camcarrier 5, 6… Camshaft 21, 22... Camshaft housing 23…Opening for injection valve 24… Plug Hole 25...Bottom wall 31, 31A, 36, 36A... sealing surface 33...Weight-removed section 35…Recess for injection valve 37…Injection valve insertion port 39…Mounting base 40…Cylinder head side spark plug hole 41...Lightening section on the cylinder head side 51…Fuel injector 52... Spark plug 55... Common Rail 56... Common Rail Boss 60… Connector

Claims

1. Cylinder head and, Two camshafts, one for the intake valve and one for the exhaust valve, A ladder-shaped cam carrier fixed to the top of the cylinder head and supporting the two camshafts mentioned above, A spark plug is positioned in the center of each cylinder, These spark plugs are each positioned adjacent to a fuel injector supported by a common rail, A cylinder head structure for an upward-injection type internal combustion engine, comprising: The above cam carrier is provided with a spark plug opening in the bottom wall between the two camshafts through which the spark plug is inserted, and a common rail boss and a fuel system opening through which the fuel injector is inserted. The spark plug opening and the fuel system opening are arranged adjacent to each other in the width direction of the internal combustion engine. The common rail boss and the fuel injector are arranged adjacent to each other in the front-to-rear direction of the internal combustion engine. moreover, The ignition coil unit connected to the above-mentioned spark plug is supported in the opening for the spark plug, The common rail boss and the fuel injector are supported by the cylinder head without contacting the opening edge of the fuel system opening. Cylinder head structure of a top-injection internal combustion engine.

2. The connector for the fuel injector is located on the side opposite the common rail boss, with the center of the fuel injector in between. A cylinder head structure for an upward-injection type internal combustion engine according to claim 1.

3. At the joint surface of the cam carrier with the cylinder head, a weight-reducing portion is formed extending from the spark plug opening toward the fuel system opening. The cylinder head structure for a top-injection type internal combustion engine according to claim 2.

4. Opposite to the above-mentioned weight-reducing portion, a weight-reducing portion on the cylinder head side is formed continuously with the spark plug hole of the cylinder head. The peripheral edges of the weight-reducing portion on the cylinder head side and the weight-reducing portion on the cylinder head side are joined to each other via a sealing member. A cylinder head structure for an upward-injection type internal combustion engine according to claim 3.

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