JP2022153891A - engine - Google Patents

Abstract

To provide an engine which can be attached with a VVT device at high accuracy, and can secure even seal performance between and among a head cover, a chain cover and a cylinder head 2.SOLUTION: A camshaft 5 for an intake valve is rotatably held to a cam housing 7 fixed to a cylinder head 2, and arranged in a position higher than the cylinder head 2. A rearward protrusion 28a of a main body case 28 constituting an electric VVT device 19 is tightly fit into a VVT positioning hole 13 which is formed at an upper support part 12 of a chain cover 3, and loosely fit to a VVT attachment hole 17 formed at a front wall 16 of the head cover 4. An exposure part 28b of the main body case 28 is fixed to the front wall 16 of the head cover 4 with bolts 21. A lower end face of the front wall 16 of the head cover 4 abuts on a flange 35 which is protrusively arranged at the chain cover 3 via a seal member 36.SELECTED DRAWING: Figure 4

Description

The present invention relates to an engine equipped with a VVT device (variable valve timing device).

2. Description of the Related Art VVT devices are widely used to change the opening/closing timing of intake valves and exhaust valves in gasoline engines and diesel engines. There are various structures and layouts of the VVT device, and as an example, Patent Documents 1 and 2 disclose that in an engine equipped with an electric VVT device, a chain cover that covers a timing chain protrudes higher than the upper surface of the cylinder head. It is disclosed to provide an upper support to which the VVT device is secured.

More precisely, the upper support portion of the chain cover is provided with a positioning hole into which the rear-facing projection of the main body case of the VVT device fits from the front side, and the main body case is exposed while the main body case is accurately positioned on the chain cover. bolts to the upper support of the chain cover.

On the other hand, the front end portion of the head cover overlaps the chain cover from above. has an arch shape that rises upward from the upper surface of the cylinder head and is recessed upward, and both are fastened with bolts in a state in which these arch-shaped portions are stacked one on top of the other.

The head cover overlaps the upper surface of the cylinder head and the upper surface of the chain cover, but overlapping in an arch shape complicates the shape and deteriorates the sealing performance. In view of this, for example, as in Patent Documents 3 and 4, techniques have been proposed for securing sealing performance on the premise of an arch shape.

JP 2017-044075 A JP 2017-218923 A JP 2015-031183 A JP 2011-127455 A

The sprocket of the VVT device must be kept concentric with the camshaft, so it is necessary to position the VVT device with the upper support of the chain cover. However, in the structures in which the VVT device is fixed to the upper support portion of the chain cover as in Patent Documents 1 and 2, the front end portion of the head cover must be pushed upward from the upper surface of the cylinder head, as described above. In order to connect the rising portion and the arch portion smoothly, flat portions are required at both right and left ends of the arch portion, and there is a risk that the width of the head cover and the chain cover will be increased by this flat portion.

In other words, since the lateral width of the arch-shaped portion cannot be reduced due to the relationship with other members, extra flat portions are formed on the left and right outer sides of the arch-shaped portion to smoothly connect the head cover, cylinder head, and chain cover. As a result, there is a risk that the width of the front portion of the engine will be expanded more than necessary.

Although it is necessary to position the VVT device by the upper support portion of the chain cover, conventionally, the need to position the VVT device causes the head cover and the like to have an arched shape, making it difficult to ensure sealing performance. It has been difficult to achieve both the certainty of device positioning and the sealing performance between the head cover and the chain cover.

The present invention is intended to improve such a situation.

The claimed invention is
"A camshaft rotatably held via a cam housing at a position higher than the cylinder head,
a timing chain disposed on the front side of the cylinder head when viewed from the crankshaft direction to transmit the rotation of the crankshaft to the camshaft;
a chain cover covering the timing chain and overlapping and fixed to the front surface of the cylinder head;
a head cover that covers the camshaft and is fixed to the upper surface of the cylinder head;
a VVT device that changes the rotational phase of the camshaft with respect to the rotation of the crankshaft,
The VVT device includes a sprocket arranged concentrically with the camshaft and around which the timing chain is wound, and a body case that rotatably holds the sprocket.
It has a basic configuration.

And in the above basic configuration,
"The chain cover has an upper support portion located on the front side of the sprocket, and the upper support portion is formed with a positioning hole into which the rear-facing protrusion of the main body case of the VVT device is fitted without being displaced from the front side. while
The head cover is formed with a front wall positioned in front of the upper support portion of the chain cover, and the front wall is formed with a VVT mounting hole into which a rearward projection of the main body case of the VVT device is fitted with clearance. is formed and the VVT device is bolted to the front face of the front wall of the head cover;
In addition, the lower surface of the front wall of the head cover is in close contact with the forward-facing flange provided on the chain cover via a sealing material."
configuration is added.

Ideally, the lower end surface of the front wall of the head cover should be formed in a straight line flush with the upper surface of the cylinder head. In some cases, there is no choice but to have a shape that bulges downward. In this case as well, the lower end surfaces of the left and right ends of the front wall are set flush with the upper surface of the cylinder head, so that the lower end surfaces of the side walls of the head cover and the lower end surfaces of the front wall are smoothly connected, and the chain cover The overlapping surface with the flange can be changed smoothly.

In the present invention, the body case of the VVT device is tightly fitted into the positioning hole formed in the upper support portion of the chain cover, so that the sprocket and cam shaft can be accurately positioned concentrically. Therefore, control of the phase of the camshaft (control of valve opening/closing timing) can be performed smoothly with high accuracy.

Since the front wall is formed at the front end of the head cover, there is no complicated arch-shaped portion as in Patent Documents 1 and 2, and the lower end surfaces of the left and right ends of the front wall are the upper surface of the cylinder head. Since the front wall can be set on the same plane as the front wall, even if the front wall is not in a straight line and has a shape that bulges downward, the change in shape is gradual.

Since there is no arch-shaped portion, the lower end surface of the side wall and the lower end surface of the front wall are smoothly continuous in the head cover. Therefore, it is not necessary to project the front wall of the head cover and the upper support portion of the chain cover to the left and right outer sides, thereby preventing the front portion of the engine from becoming wide.

The main body case of the VVT device is fixed to the front wall of the head cover, but since the main body case is fitted into the mounting hole provided in the front wall with a clearance, the height of the head cover is affected by variations in the amount of compression of the sealing material. Even if the thickness changes slightly, it can absorb the change and fix it firmly.

Therefore, in the present invention, it is possible to simultaneously achieve accurate positioning of the VVT device and firm fixation of the VVT device while ensuring high sealing performance, and also contribute to preventing an engine from becoming large.

(A) is a front view of the embodiment, and (B) is a cross-sectional view taken along line BB of (A). FIG. 4 is a front view in which the head cover and the chain cover are separated; It is a partial plan view. FIG. 2 is a sectional view taken along line IV-IV of FIG. 1;

Next, embodiments of the present invention will be described based on the drawings. This embodiment is applied to an automotive gasoline engine. In this application, the terms front-rear and left-right are used to specify the direction, but as defined in the claims, the front-rear direction is the direction of the crank axis, and the left-right direction is the direction orthogonal to the crank axis and the cylinder bore axis. be. Regarding the front and rear, the side where the timing chain is arranged is the front, and the side where the transmission case is arranged is the rear.

(1).Basic structure As shown in Fig. 1, the engine consists of a cylinder block 1, a cylinder head 2 fixed to the upper surface of the cylinder block 1, and a chain cover (front cover) 3 fixed to the front surface of the cylinder block 1 and the cylinder head 2. , and a head cover 4 which is overlapped and fixed on the upper surface of the cylinder head 2 .

As indicated by dotted lines in FIG. 1 , the intake valve camshaft 5 and the exhaust valve camshaft 6 are arranged at positions higher than the cylinder head 2 . Also, as shown only partially in FIG. 4, a cam housing 7 is disposed inside the head cover 4, and a bearing portion 8 formed in the cam housing 7 and a cam overlapped and fixed to the lower surface thereof with bolts. The cam shafts 5 and 6 are rotatably held by the cap 9 .

Although not shown, the cam housing 7 has a plurality of pairs of legs, and the legs are fixed to the bottom surface of the cylinder head 2 to a host body. The bearing portion 8 located at the front end and the front surfaces of the cam cap 9 are aligned with the front surface of the cylinder head 2 . As shown in FIG. 1, a large number of bolt insertion holes 10 for fixing the chain cover 3 to the cylinder head 2 and the cylinder block 1 are formed at intervals in the vertical direction on the left and right sides of the chain cover 3 .

Needless to say, a pair of intake valves and a pair of exhaust valves are slidably held in the cylinder head 2. directly or via a rocker arm.

As clearly shown in FIG. 2 , the chain cover 3 is formed with an upper support portion 12 that protrudes above the cylinder head 2 . A positioning hole 13 and a cam angle sensor positioning hole 14 concentric with the exhaust valve camshaft 6 are open.

On the other hand, the head cover 4 is formed in the shape of a tray that opens downward. Therefore, as shown in FIGS. and a front wall 16 integrally connected to the front ends of the left and right side walls 15 and the top plate. The front wall 16 is the upper support portion of the chain cover 3. 12 (there may be a gap between the front wall 16 and the upper support 12).

A front wall 16 of the head cover 4 is provided with a VVT mounting hole 17 corresponding to the upper support portion 12 of the chain cover 3 and concentrically with the intake valve camshaft 5. 18 is open concentrically with the camshaft 6 for exhaust. An electric VVT device 19 and an OCV integrated hydraulic VVT device 20 are fixed to the front wall 16 of the head cover 4 with bolts 21 and 22 .

(2) VVT device As shown in Fig. 4, the electric VVT device 19 includes a rotor 25 having a sprocket 24 around which a timing chain 23 is wound, and a relay shaft to which the front half of the rotor 25 is rotatably fitted. 26, and a body case 28 containing a variable mechanism 27 controlled by a motor.

The main body case 28 has a rear projection (small diameter portion) 28 a fitted into the downward front wall 16 of the head cover 4 and the upper support portion 12 of the chain cover 3 , and an exposed portion (large diameter portion) 28 b overlapping the front surface of the front wall 16 . have. The rearward projecting portion 28a has a circular shape and is tightly fitted into the VVT positioning hole 13 of the upper support portion 12, and into the VVT mounting hole 17 of the front wall 16 with a slight clearance (loose fit). there is.). On the other hand, the exposed portion 28b is fixed to the front wall 16 of the head cover 4 by bolts 21 at three locations spaced apart in the circumferential direction.

An inward boss portion 29 for forming an internal thread into which the bolt 21 is screwed is formed at the upper end and the side end of the head cover 4 , and a bolt located at the lower end is formed at the lower end of the front wall 16 . A forward facing boss 30 is formed for forming an internal thread into which 21 is screwed. As shown in FIGS. 1 and 3, a connector receiving portion 31 for connecting a cable is provided at an oblique upper portion of the exposed portion 28b of the main body case 28. As shown in FIGS.

As shown in FIG. 4 , the front end portion of the intake valve camshaft 5 is fitted into the rear half portion of the rotor 25 via the drive portion 32 . , the relay shaft 26 described above is fitted. The relay shaft 26 is attached to the variable mechanism section 27 via a rod 33 so as to rotate by a predetermined angle.

The driving portion 32 is made up of a plurality of members, and rotates together with the rotor 25 and the intake valve camshaft 5. When the intermediate shaft 26 is rotated, the intake valve camshaft 5 is moved to the rotor through the driving portion 32. 25. Therefore, when the driving portion 32 is operated by the variable mechanism portion 27 via the relay shaft 26, the intake valve camshaft 5 advances or retards with respect to the crankshaft, thereby changing the opening/closing timing of the intake valve. do. A front end portion of the rotor 25 is rotatably held by a small-diameter portion 28a of a body case 28 via an oil seal 34. As shown in FIG.

(2) Summary The side wall 15 and rear wall of the head cover 4 are fixed to the upper surface of the cylinder head 2 by a group of bolts (not shown). On the other hand, as shown in FIG. 1B, the front wall 16 of the head cover 4 is in contact with the upper surface of a flange 35 protruding forward from the upper support portion 12 of the chain cover 3 via a sealing material 36. . An annular groove 37 filled with a sealing material 36 is formed in the lower surface of the head cover 4 over the entire circumference. The sealing material 36 is formed by applying a liquid material with a dispenser and then solidifying it, but a ring body made of a soft material such as an O-ring can also be used.

Since the flange 35 of the head cover 4 is formed to avoid the VVT device 19 , it has a shape that bulges downward when viewed from the front so that the lower portion of the VVT device 19 is the lowest. Accordingly, the lower end of the front wall 16 of the head cover 4 is also swollen downward.

The left and right end portions 35a of the flange 35 are flat portions having the same height as the upper surface of the cylinder head 2. , the amount by which the front wall 16 of the head cover 4 bulges below the cylinder head 2 is much smaller than the height dimension from the cylinder head 2 to the upper end of the head cover 4 . Therefore, although the lower end of the front wall 16 and the flange 35 of the chain cover 3 bulge downward, the amount of bulging is small compared to the conventional arch shape. , high sealing performance can be ensured.

Further, since the left and right end portions 35a of the flange 35 are at the same height as the upper surface 2a of the cylinder head 2, sealing performance between the flange 35, the cylinder head 2 and the head cover 4 can be ensured. Further, since the rigidity of the head cover 4 is significantly improved by the presence of the front wall 16 in the head cover 4, a high sealing performance can be ensured without fixing the front wall 16 and the flange 35 with bolts (however, bolts may be used). It is not excluded to conclude.).

Now, a configuration in which the electric VVT device 19 is fixed to the upper support portion 12 of the chain cover 3 and the top plate of the head cover 4 is superimposed on the upper surface of the upper support portion 12 is indicated by a dashed line in FIG. , the side end portion 4a of the head cover 4 and the side end portion 12a of the upper support portion 12 must be raised from the upper surface of the cylinder head 2, so that the side end portion 4a of the cylinder head 2 and the upper support portion 12 By projecting the side ends 4a and 12a to the left and right outwards, the side ends 4a and 12a must be formed flat to form a stable and continuous sealing surface. There is a possibility that it will spread more than necessary and increase the size of the engine.

On the other hand, in the present embodiment, the lower surface of the side end portion 16a of the front wall 16 and the upper surface of the side end portion 35a of the flange 35 of the head cover 4 are at the same height as the upper surface of the cylinder head 2. Even if the side ends 16a and 35a are formed flat, the front wall 16 and the flange 35 are formed in a downwardly bulging shape to form a smoothly continuous sealing surface without extending the side ends 16a and 35a to the left and right outer sides. can be formed. Therefore, it is possible to prevent the front portion of the engine from becoming wider than necessary.

In a state in which the small diameter portion 28a of the body case 28 constituting the electric VVT device 19 is accurately positioned by the VVT positioning hole 13 of the upper support portion 12 of the chain cover 3, the exposed portion 28b of the body case 28 is placed on the head cover. 4, the small-diameter portion 28a of the main body case 28 is loosely fitted in the VVT mounting hole 17 of the front wall 16. Therefore, the height of the head cover 4 varies depending on the amount of compression of the sealing material 36. Even if there is some error in , it can be fixed in a state in which the error is absorbed.

Therefore, in the present embodiment, the electric VVT device 19 can be fixed with high precision while ensuring the sealing performance between the head cover 4, the chain cover 3 and the cylinder head 2, and an increase in size of the engine can be prevented.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the sizes of the positioning holes and VVT mounting holes can be arbitrarily set according to the type of VVT device. It is also possible to place the cam angle sensor on the top plate of the head cover. In this case, the flange has a shape that bulges downward only at the location of the VVT device. In the embodiment, the VVT device on the exhaust side is configured as a hydraulic type, but it is also possible to adopt an electric VVT device on the exhaust side and apply the present invention.

The present invention can be embodied in an engine with a VVT device. Therefore, it can be used industrially.

2 Cylinder head 3 Chain cover 4 Head cover 5 Intake valve camshaft 6 Exhaust valve camshaft 7 Cam housing 9 Cam cap 12 Chain cover upper support 13 VVT positioning hole 16 Head cover front wall 17 VVT mounting hole 19 Electric VVT Device 21 Bolt for fastening VVT device 23 Timing chain 24 Sprocket 25 Rotor 28 Main body case 28a Rear projection (small diameter portion)
28b exposed part (large diameter part)
35 Flange 36 Sealing material 37 Annular groove

Claims (1)

a camshaft rotatably held at a position higher than the cylinder head via a cam housing;
a timing chain arranged on the front side of the cylinder head when viewed in the crankshaft direction to transmit the rotation of the crankshaft to the camshaft;
a chain cover covering the timing chain and overlapping and fixed to the front surface of the cylinder head;
a head cover that covers the camshaft and is fixed to the upper surface of the cylinder head;
a VVT device that changes the rotational phase of the camshaft with respect to the rotation of the crankshaft,
The VVT device includes a sprocket arranged concentrically with the camshaft and around which the timing chain is wound, and a body case that rotatably holds the sprocket,
The chain cover has an upper support portion located on the front side of the sprocket, and a positioning hole is formed in the upper support portion into which the rearward projection of the main body case of the VVT device is fitted so as not to shift from the front side. on the other hand,
The head cover is formed with a front wall positioned in front of the upper support portion of the chain cover, and the front wall is formed with a VVT mounting hole into which a rearward protrusion of the main body case of the VVT device is fitted with clearance. is formed and the VVT device is bolted to the front face of the front wall of the head cover;
The lower surface of the front wall of the head cover is in close contact with a forward facing flange provided on the chain cover via a sealing material.
engine.

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