Cylinder head of an internal combustion engine

Abstract

To suppress inclination of a cam cap while preventing increases in weight and cost.SOLUTION: A cylinder head includes an injector holder 260 provided with a plurality of injector insertion holes 268. In a cam shaft housing 22 of the cylinder head, cam caps 241-245 are fastened at intervals. The injector holder 260 is fastened to each of the cam caps 241-245 at one place each. Odd-numbered fastening places X1, X3, X5 in the order in a direction from front toward rear of fastening places X1-X5 to the cam caps 241-245, are positioned at a side closer to an exhaust cam shaft 25 than an intermediate point between the exhaust cam shaft 25 and an intake cam shaft 23. The even-numbered fastening places X2, X4 are positioned at a side closer to the intake cam shaft 23 than the intermediate point between the exhaust cam shaft 25 and the intake cam shaft 23.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cylinder head for an internal combustion engine. [Background technology]

[0002] Patent Document 1 discloses a camshaft holding structure for an internal combustion engine. In this holding structure, a cylinder head is provided with a semicircular bearing portion that supports the camshaft journal. A cam cap is also provided with a semicircular cap-side bearing portion that supports the camshaft journal. The camshaft is placed so that the journal is located within this bearing portion. With the camshaft placed on the bearing portion, the cam cap is fastened to the cylinder head. As a result, the camshaft journal is held by the bearing portion and the cap-side bearing portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-024980 A Summary of the Invention [Problem to be solved by the invention]

[0004] The expansion of the combustion gas in each combustion chamber exerts a load on the intake and exhaust valves. The load is then transmitted to the camshaft via the intake and exhaust valves. The load transmitted to the camshaft also acts on the cam cap that supports the camshaft. If the cam cap tilts due to this load, the journals become more susceptible to wear. [Means for solving the problem]

[0005] The means for solving the above problems and their effects will be described below. A cylinder head for an internal combustion engine for solving the above problems supports a first camshaft and a second camshaft arranged in parallel with each other by fastening a plurality of cam caps to a camshaft housing. The cylinder head includes an injector holder that fixes a plurality of injectors between the first camshaft and the second camshaft by inserting an injector into each of a plurality of insertion holes, with the tip of the injector facing each combustion chamber. Each of the cam caps includes a first bearing portion that supports a journal of the first camshaft and a second bearing portion that supports a journal of the second camshaft. The plurality of cam caps are fastened to the camshaft housing at intervals in the axial direction in accordance with the positions of a plurality of journals arranged at intervals in the axial direction on the first camshaft and the second camshaft. The injector holder is fastened to each of the cam caps at one location. The fastening points with respect to each of the cam caps are arranged such that, in the order from one side of the axial direction to the other, the odd-numbered fastening points are located closer to the first camshaft than the midpoint between the first camshaft and the second camshaft, and the even-numbered fastening points are located closer to the second camshaft than the midpoint between the first camshaft and the second camshaft.

[0006] In the above configuration, a plurality of cam caps are arranged at intervals in the axial direction of the first camshaft and the second camshaft. The cam caps are connected by an injector holder. Therefore, the cam caps are less likely to tilt due to the load acting through the first camshaft and the second camshaft. In the above configuration, each cam cap is fastened to the injector holder at one location. The fastening locations are arranged in a zigzag pattern across the midpoint between the first camshaft and the second camshaft.

[0007] This minimizes the number of fastening points required to connect all the cam caps, and also distributes the load over a wider area than if the fastening points were lined up in a straight line.

[0008] That is, according to the above-described configuration, the injector holder can be used to suppress tilt of the cam cap while avoiding increases in weight and cost. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a front view of an engine equipped with a cylinder head according to one embodiment. [Diagram 2] FIG. 2 is a top view of a camshaft housing and an injector holder in the cylinder head of the embodiment. [Diagram 3] FIG. 3 is an exploded perspective view of the camshaft housing and the injector holder. [Figure 4] FIG. 4 is a perspective view of the camshaft housing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, one embodiment of a cylinder head for an internal combustion engine will be described with reference to Figs. <Engine 100 Configuration> FIG. 1 is a front view of an engine 100 equipped with a cylinder head 20. The engine 100 is an in-line four-cylinder engine. As shown in FIG. 1, the cylinder head 20 is fixed to the upper part of a cylinder block 10. An oil pan 30 is fixed to the lower part of the cylinder block 10. A crankshaft 11 is housed in the lower part of the cylinder block 10. A sprocket 12 is fixed to one end of the crankshaft 11. A head cover 40 is fixed to the upper part of the cylinder head 20 to cover the opening at the top of the cylinder head 20.

[0011] <Configuration of cylinder head 20> The cylinder head 20 is formed by combining a cylinder head body 21 and a camshaft housing 22. The cylinder head body 21 houses an intake valve and an exhaust valve. The cylinder head body 21 is fixed to the upper part of the cylinder block 10. As a result, the cylinder head body 21 forms the ceiling of the combustion chamber of each cylinder of the engine 100.

[0012] The camshaft housing 22 accommodates an intake camshaft 23 and an exhaust camshaft 25. An intake-side variable valve timing mechanism 27 is attached to the end of the intake camshaft 23. An exhaust-side variable valve timing mechanism 28 is attached to the end of the exhaust camshaft 25. The intake-side variable valve timing mechanism 27 and the exhaust-side variable valve timing mechanism 28 each comprise a sprocket.

[0013] As shown in FIG. 1, a timing chain 50 is wound around the valve timing change mechanisms 27, 28 and the sprocket 12. As a result, when the crankshaft 11 rotates, the intake camshaft 23 and the exhaust camshaft 25 also rotate in conjunction with the rotation of the crankshaft 11. In the engine 100, the surface on which the timing chain 50 is provided is the front surface of the engine 100. In the engine 100, the front surface is referred to as the front surface of the engine 100, and the rear surface is referred to as the rear surface of the engine 100. That is, FIG. 1 is a front view of the engine 100 as seen from the front side toward the rear side. In the engine 100, the timing chain 50 rotates counterclockwise in FIG. 1 as the engine operates. That is, the crankshaft 11, the intake camshaft 23, and the exhaust camshaft 25 also rotate counterclockwise.

[0014] <Configuration of camshaft housing 22> 2 to 4, the camshaft housing 22 has a rear wall 227 which is a side wall on the rear side, and a pair of side walls 228, 229. Of the pair of side walls 228, 229, the side wall 229 located on the right side when the engine 100 is viewed from the front side to the rear side is the right side wall 229. Of the pair of side walls 228, 229, the side wall 228 located on the left side when the engine 100 is viewed from the front side to the rear side is the left side wall 228.

[0015] 4, five horizontal frames 221-225 are suspended between the right side wall 229 and the left side wall 228 of the camshaft housing 22. The five horizontal frames 221-225 are, in order from the front side to the rear side, a first horizontal frame 221, a second horizontal frame 222, a third horizontal frame 223, a fourth horizontal frame 224, and a fifth horizontal frame 225. A first bearing portion 237 and a second bearing portion 238 are provided on each of the horizontal frames 221-225.

[0016] The first bearing portion 237 is a semicircular recess that supports the journal of the exhaust camshaft 25, which is the first camshaft, and the second bearing portion 238 is a semicircular recess that supports the journal of the intake camshaft 23, which is the second camshaft.

[0017] As shown in Figures 3 and 4, exhaust camshaft 25 is provided with eight exhaust cams 26, two for each cylinder. The exhaust cams 26 are provided in pairs for each cylinder and spaced apart in the axial direction of exhaust camshaft 25. Similarly, intake camshaft 23 is provided with eight intake cams 24, two for each cylinder. The intake cams 24 are provided in pairs for each cylinder and spaced apart in the axial direction of intake camshaft 23. Also, as shown in Figure 2, in addition to the intake cams 24, intake camshaft 23 is provided with a pump cam 29 that drives a high-pressure fuel pump.

[0018] Two intake cams 24 and two exhaust cams 26 corresponding to the first cylinder are positioned between the first horizontal frame 221 and the second horizontal frame 222. Two intake cams 24 and two exhaust cams 26 corresponding to the second cylinder are positioned between the second horizontal frame 222 and the third horizontal frame 223. Two intake cams 24 and two exhaust cams 26 corresponding to the third cylinder are positioned between the third horizontal frame 223 and the fourth horizontal frame 224. Two intake cams 24 and two exhaust cams 26 corresponding to the fourth cylinder are positioned between the fourth horizontal frame 224 and the fifth horizontal frame 225. In this way, the five horizontal frames 221 to 225 are provided at approximately equal intervals so as to sandwich the two intake cams 24 and two exhaust cams 26 paired for each cylinder.

[0019] 4, the camshaft housing 22 is provided with a vertical frame 226. The vertical frame 226 is provided between the intake camshaft 23 and the exhaust camshaft 25 so as to extend parallel to the intake camshaft 23 and the exhaust camshaft 25. The vertical frame 226 extends from the rear wall 227 to the first horizontal frame 221, and connects the rear wall 227 to the horizontal frames 221 to 225. This reinforces the camshaft housing 22.

[0020] 2 to 4, five cam caps 241 to 245 are fixed to the horizontal frames 221 to 225 with bolts 250. The five cam caps 241 to 245 are, in order from the front side to the rear side, a first cam cap 241, a second cam cap 242, a third cam cap 243, a fourth cam cap 244, and a fifth cam cap 245. Each of the cam caps 241 to 245 is provided with a first cap side bearing portion 247 and a second cap side bearing portion 248.

[0021] The first cap side bearing portion 247 is a semicircular recess that combines with the first bearing portion 237 to support the journal of the exhaust camshaft 25. The second cap side bearing portion 248 is a semicircular recess that combines with the second bearing portion 238 to support the journal of the intake camshaft 23.

[0022] A first cam cap 241 is fastened to the first horizontal frame 221 with bolts 250. A second cam cap 242 is fastened to the second horizontal frame 222 with bolts 250. A third cam cap 243 is fastened to the third horizontal frame 223 with bolts 250. A fourth cam cap 244 is fastened to the fourth horizontal frame 224 with bolts 250. And a fifth cam cap 245 is fastened to the fifth horizontal frame 225 with bolts 250. That is, the cam caps 241 to 245 are fastened to the camshaft housing 22 with intervals in accordance with the positions of the journals of the exhaust camshaft 25 and the intake camshaft 23. In this way, the intake camshaft 23 and the exhaust camshaft 25 are supported in parallel to each other by the camshaft housing 22.

[0023] <Configuration of injector holder 260> As shown in Fig. 2, an injector holder 260 is attached to the upper part of the camshaft housing 22. The injector holder 260 is provided with four injector insertion holes 268 through which the injectors are inserted and fixed. The injectors inserted into the injector insertion holes 268 pass between the intake camshaft 23 and the exhaust camshaft 25 until their tips reach the cylinder head main body 21. The injector holder 260 is then fixed to the injector holder 260 so that its tips face the combustion chambers. The injector holder 260 is a holder that fixes the four injectors to the cylinder head 20 in this manner so that they face the combustion chambers of the respective cylinders.

[0024] 3, the injector holder 260 is fastened to the camshaft housing 22 by six bolts 251-256. The injector holder 260 is provided with six bolt insertion holes 261-266 penetrating the injector holder 260. The cam caps 241-245 are provided with bolt holes 231-235 into which the bolts 251-255 are screwed.

[0025] When attaching the injector holder 260, the first bolt 251 is inserted into the first bolt insertion hole 261 and screwed into the first bolt hole 231 of the first cam cap 241. This fastens the first cam cap 241 and the injector holder 260 together. Hereinafter, the fastening point between the first cam cap 241 and the injector holder 260 by the first bolt 251 will be referred to as a first fastening point X1.

[0026] When attaching the injector holder 260, the second bolt 252 is inserted through the second bolt insertion hole 262 and screwed into the second bolt hole 232 of the second cam cap 242. This fastens the second cam cap 242 and the injector holder 260 together. Hereinafter, the fastening point between the second cam cap 242 and the injector holder 260 by the second bolt 252 will be referred to as the second fastening point X2.

[0027] When attaching injector holder 260, third bolt 253 is inserted into third bolt insertion hole 263 and screwed into third bolt hole 233 of third cam cap 243. This fastens third cam cap 243 and injector holder 260 together. Hereinafter, the fastening point between third cam cap 243 and injector holder 260 by third bolt 253 will be referred to as third fastening point X3.

[0028] When attaching the injector holder 260, the fourth bolt 254 is inserted into the fourth bolt insertion hole 264 and screwed into the fourth bolt hole 234 of the fourth cam cap 244. This fastens the fourth cam cap 244 and the injector holder 260 together. Hereinafter, the fastening point between the fourth cam cap 244 and the injector holder 260 by the fourth bolt 254 will be referred to as a fourth fastening point X4.

[0029] When attaching the injector holder 260, the fifth bolt 255 is inserted into the fifth bolt insertion hole 265 and screwed into the fifth bolt hole 235 of the fifth cam cap 245. This fastens the fifth cam cap 245 and the injector holder 260 together. Hereinafter, the fastening point between the fifth cam cap 245 and the injector holder 260 by the fifth bolt 255 will be referred to as a fifth fastening point X5.

[0030] Further, the rear wall 227 is provided with a bolt hole 236 into which a sixth bolt 256 is screwed. The rear wall 227 and the injector holder 260 are fastened together by inserting the sixth bolt 256 into the sixth bolt insertion hole 266 and screwing it into the sixth bolt hole 236 of the rear wall 227. Hereinafter, the fastening point between the rear wall 227 and the injector holder 260 by the sixth bolt 256 will be referred to as a sixth fastening point X6.

[0031] In this manner, the injector holder 260 is fastened to the camshaft housing 22 at six fastening points X1 to X6. 2, the central axis of the exhaust camshaft 25 attached to the camshaft housing 22 is indicated by a dashed line C1, and the central axis of the intake camshaft 23 is indicated by a dashed line C2.

[0032] The six fastening points X1 to X6 are arranged in the order of first, second, third, fourth, fifth and sixth in the direction from the front side to the rear side along the extending direction of the dashed dotted lines C1 and C2.

[0033] 2, a virtual line that is equidistant to the dashed-dotted lines C1 and C2 is indicated by a dashed-two-dotted line C3. That is, the dashed-two-dotted line C3 is a line that connects the midpoints of the exhaust camshaft 25 and the intake camshaft 23.

[0034] 2, in this cylinder head 20, the first fastening point X1, the third fastening point X3, and the fifth fastening point X5 are located on the right side wall 229 side of the two-dot chain line C3. That is, the first bolt hole 231 in the first cam cap 241 is provided in a position offset toward the first cap-side bearing portion 247. Similarly, the third bolt hole 233 in the third cam cap 243 and the fifth bolt hole 235 in the fifth cam cap 245 are also provided in positions offset toward the first cap-side bearing portion 247.

[0035] The second fastening point X2 and the fourth fastening point X4 are located on the left side wall 228 side of the two-dot chain line C3. That is, the second bolt hole 232 in the second cam cap 242 is provided at a position offset toward the second cap side bearing portion 248. Similarly, the fourth bolt hole 234 in the fourth cam cap 244 is provided at a position offset toward the second cap side bearing portion 248.

[0036] In this manner, in the cylinder head 20, the injector holder 260 is fastened to each of the cam caps 241-245 at one location each. Among the fastening locations X1-X5, in the order from the front side to the rear side, the odd-numbered fastening locations X1, X3, and X5 are located closer to the exhaust camshaft 25 than the two-dot chain line C3. The even-numbered fastening locations X2 and X4 are located closer to the intake camshaft 23 than the two-dot chain line C3.

[0037] <effect> The cam caps 241-245 are disposed at intervals in the axial direction of the exhaust camshaft 25 and the intake camshaft 23. The cam caps 241-245 are connected by an injector holder 260. Therefore, each cam cap is unlikely to tilt due to the load acting via the exhaust camshaft 25 and the intake camshaft 23.

[0038] In the above configuration, there is only one fastening point between each cam cap and the injector holder 260. The fastening points X1 to X5 are arranged in a zigzag pattern so as to straddle the midpoint between the exhaust camshaft 25 and the intake camshaft 23.

[0039] <Effects> All of the cam caps 241 to 245 are connected by minimizing the number of fastening points. Also, the load can be distributed over a wider range than if the fastening points X1 to X5 were arranged in a straight line.

[0040] That is, according to the above-described configuration, the injector holder 260 can be used to suppress tilting of the cam caps 241-245 while avoiding increases in weight and cost. <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0041] The configuration of the camshaft housing 22 can be changed as appropriate. For example, the number of horizontal frames may be changed according to the number of cylinders of the engine 100. That is, the number of cam caps may also be changed according to the number of cylinders. Even if the number of cam caps is changed, the same effect as in the above embodiment can be obtained as long as the fastening points of each cam cap and the injector holder 260 are arranged in a zigzag pattern. That is, it is sufficient that the odd-numbered fastening points in the order from one side to the other in the axial direction of the camshaft are located on one camshaft side, and the even-numbered fastening points are located on the other camshaft side. That is, the same configuration as in the above embodiment can be applied not only to a four-cylinder engine, but also to a three-cylinder engine and an engine with five or more cylinders. In addition, the same configuration as in the above embodiment can be applied to each bank of a multi-bank engine such as a V-type engine.

[0042] In the above embodiment, an example has been shown in which the first camshaft is the exhaust camshaft 25 and the second camshaft is the intake camshaft 23. The first camshaft may be the intake camshaft 23 and the second camshaft may be the exhaust camshaft 25. Even in this case, the fastening points are arranged in a zigzag pattern as long as the odd-numbered fastening points are located on one camshaft side and the even-numbered fastening points are located on the other camshaft side in the axial direction of the camshafts.

[0043] In the above embodiment, the order of the fastening points is determined in the order from the front side to the rear side, but the order of the fastening points may be determined in the order from the rear side to the front side. Even in this case, the fastening points will be arranged in a zigzag pattern if the odd-numbered fastening points are located on one camshaft side and the even-numbered fastening points are located on the other camshaft side in the order from one side to the other in the axial direction of the camshaft. [Explanation of symbols]

[0044] 20…Cylinder head 21...Cylinder head body 22…Camshaft housing 23…Intake camshaft 25…Exhaust camshaft 231…First bolt hole 232…Second bolt hole 233…3rd bolt hole 234…4th bolt hole 235…5th bolt hole 236...6th bolt hole 237...First bearing part 238…Second bearing part 241…1st cam cap 242…Second cam cap 243…Third cam cap 244…4th cam cap 245…5th cam cap 247…First cap side bearing part 248…Second cap side bearing part 251…First bolt 252…Second bolt 253…Third bolt 254…4th bolt 255...5th bolt 256...6th bolt 260…Injector holder

Claims

[Claim 1] A cylinder head for an internal combustion engine, in which a first camshaft and a second camshaft arranged in parallel are supported by a camshaft housing and a plurality of cam caps fastened to the camshaft housing, an injector holder for fixing the injectors between the first camshaft and the second camshaft by inserting the injectors into the respective insertion holes so that the tips of the injectors face the respective combustion chambers; Each of the cam caps includes a first bearing portion that supports a journal of the first camshaft and a second bearing portion that supports a journal of the second camshaft, the plurality of cam caps are fastened to the camshaft housing at intervals in the axial direction in accordance with positions of a plurality of journals arranged at intervals in the axial direction on the first camshaft and the second camshaft, The injector holder is fastened to each of the cam caps at one location, and the fastening locations of the cam caps are such that, in the order from one side of the axial direction to the other side, the odd-numbered fastening locations are located closer to the first camshaft than a midpoint between the first camshaft and the second camshaft, and the even-numbered fastening locations are located closer to the second camshaft than a midpoint between the first camshaft and the second camshaft. Cylinder head of an internal combustion engine.

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