JPH07293210A - Engine variable valve timing device - Google Patents

Abstract

PURPOSE:To prevent any expansion of an engine width by connecting an exhaust cam transmission member, to an air intake cam transmission member, and a timing transmission member to a crank shaft transmission member respectively and positioning a valve timing variable mechanism for relatively rotating an exhaust cam shaft and the timing transmission member within the axial direction projecting surface of the timing transmission member. CONSTITUTION:An air intake cam sprocket 12 is mounted on an air intake shaft 7 and connected to an exhaust cam sprocket 14 mounted on an exhaust cam shaft 8 by means of a transmission chain 15. A timing sprocket 16 is mounted rather outside the exhaust cam sprocket 14 so as to be relatively rotatable with the exhaust cam shaft 8. The timing sprocket 16 is connected to a crank sprocket linked with a crank shaft by means of a timing chain 19. The variable mechanism 21 of a variable valve timing device 20 is arranged within the cam shaft direction projecting surface of the timing sprocket and thus a V type engine can be prevented from being enlarged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing device for changing the opening / closing timing of an intake valve and an exhaust valve in a V-type engine.

[0002]

2. Description of the Related Art A variable valve timing device has been proposed in which the opening / closing timing of intake and exhaust valves is changed according to the engine speed and load. As such a variable valve timing device, conventionally, for example, a timing gear and a camshaft are connected via a piston with a helical gear, and the piston is hydraulically moved in the camshaft direction so that the camshaft and the timing gear are opposed to each other. There is a variable mechanism for rotating the intake valve and the exhaust valve to change the phase of the intake valve and the exhaust valve by changing the phase of both of them by supplying and stopping the hydraulic pressure by a solenoid valve.

In mounting the solenoid valve, the solenoid valve is generally mounted directly on the cylinder head in the cam shaft direction so as to face the end face of the cam shaft on which the variable mechanism is mounted. is there.

[0004]

By the way, when the variable valve timing device is adopted in a V-type engine, when the engine as a whole is viewed depending on the variable mechanism, the arrangement position of the solenoid valve, the arrangement direction, etc., There is a concern that the size will increase in the length direction (crank axis direction) and the width direction (direction perpendicular to the crank axis). In particular, when the solenoid valve is arranged so as to face the camshaft, the advantage of the V-type engine that the length of the engine in the crankshaft direction can be shortened may be impaired.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a variable valve timing device in which the engine does not become large.

[0006]

According to the invention of claim 1, a plurality of cylinders are arranged so as to form a V bank, the intake cam shaft is arranged inside the V bank, and the exhaust cam shaft is arranged outside the V bank. In the installed engine variable valve timing device,
An exhaust cam transmission member provided on the exhaust cam shaft and an intake cam transmission member provided on the intake cam shaft are connected to each other, and the timing transmission member and the crank shaft are mounted on the exhaust cam shaft so as to be rotatable relative to each other. A variable mechanism that changes the valve timing by connecting the crank transmission member and rotating the exhaust cam shaft and the timing transmission member relative to each other so as to be located in the axial projection plane of the timing transmission member. It is characterized in that it is arranged on the exhaust cam shaft.

According to a second aspect of the present invention, the variable mechanism is configured to relatively rotate the timing transmission member and the exhaust cam shaft by axial movement of a hydraulically driven piston. A switching valve for switching between the supply and the discharge of the exhaust gas is attached to the bearing cap of the exhaust cam shaft, and the invention of claim 3 is
It is characterized in that the switching valve is arranged substantially parallel to the bisector of the V bank.

According to a fourth aspect of the present invention, in the variable valve timing device, an exhaust cam transmission member provided on the exhaust cam shaft and an intake cam transmission member mounted on the intake cam shaft so as to be rotatable relative to each other are connected to each other. , A valve timing is changed by connecting a timing transmission member provided on the exhaust cam shaft and a crank transmission member provided on a crank shaft, and relatively rotating the intake cam shaft and the intake cam transmission member. A variable mechanism for controlling the intake cam shaft is provided on the intake cam shaft.

According to a fifth aspect of the invention, in the fourth aspect of the invention, the variable mechanism relatively rotates the intake cam transmission member and the intake cam shaft by axial movement of a piston driven by hydraulic pressure. It is characterized in that the switching valve for switching the supply or discharge of the hydraulic pressure is mounted on the bearing cap of the intake camshaft.

[0010]

According to the invention of claim 1, when the variable valve timing device is adopted in a V-type engine, a timing transmission member is attached to the exhaust cam shaft arranged outside the V bank, and the variable mechanism has a large diameter. Since it is arranged in the timing transmission member portion, the variable mechanism can be reasonably arranged so as to be located in the projection plane of the timing transmission member in the axial direction, and the expansion of the engine width can be avoided. By the way, the timing transmission member is V
When it is mounted on the intake cam shaft located inside the bank, it is necessary to take measures such as increasing the V bank angle in order to avoid interference between the timing transmission member having a large diameter and the components arranged in the V bank. There is a concern that

According to the second and fifth aspects of the present invention, the switching valve for switching the supply or discharge of the hydraulic pressure to the hydraulic variable mechanism is mounted on the bearing cap constituting the upper half of the camshaft bearing. It is possible to avoid the problem that the length of the engine in the crankshaft direction becomes long due to the mounting of the switching valve.

Further, since the changeover valve is mounted on the bearing cap, the space for arranging the changeover valve can be easily secured as compared with the case where the changeover valve is directly attached to the cylinder head, and the sealing surface, the fixing boss, etc. are provided in the cylinder head. The structure can be simplified as much as there is no need to provide it inside, and the cylinder head can be shared with a cylinder head not equipped with a variable valve timing device.

Further, in the invention of claim 3, since the switching valve is arranged in the direction of the bisector of the V bank, the switching valve can be easily placed in the engine projection plane in the direction of the bisector. The engine width can be avoided from this point as well.

According to the fourth aspect of the present invention, since the variable mechanism for relatively rotating the intake cam transmission member which is relatively rotatably attached to the intake cam shaft is attached to the intake cam shaft, the phase of only the intake cam shaft is changed. Therefore, the opening / closing timing of only the intake valve can be changed.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 6 are views for explaining a variable valve timing device for an engine according to a first embodiment of the present invention, wherein FIG. 1 is a partial sectional front view of the engine, and FIG. 3 and 4 are sectional views taken along the lines III-III and IV-IV in FIG. 2, and FIGS. 5 and 6 are schematic views for explaining the operation.

In these drawings, reference numeral 1 is a water-cooled 4-cycle V-type multi-cylinder 5-valve engine in which the apparatus of this embodiment is adopted, and the engine 1 is formed so that a plurality of cylinders form a V bank A. Lower mating surface 2a of cylinder block 2
An oil pan 3 (see FIGS. 5 and 6) is mounted on the upper side, a cylinder head 4 is mounted on the left and right upper side facing surfaces 2b, and a head cover 5 is covered on the upper side facing surfaces 4a of the left and right cylinder heads 4. It is a composition. A seal member 34 made of an elastic material such as rubber is interposed between the upper mating surface 4a and the head cover 5, so that the head cover 5 is so-called floating supported.

A surge tank 6 is provided in the V bank A.
An intake system 6 including an intake manifold 6b and an intake manifold 6b is arranged so as to substantially fill the inside of the V bank A, and the downstream end of the intake manifold 6b is formed on the inner wall of the V bank of the cylinder head 4. External connection port of intake port 4
connected to b. In addition, 6c is a fuel injection valve.

The upper mating surface 4a of the cylinder head 4 is
The intake cam shaft 7 is arranged in parallel with the inside of the V bank, and the exhaust cam shaft 8 is arranged in parallel with the outside of the V bank.
The journal portions 7a, 8 of the intake and exhaust camshafts 7, 8
a is a bearing portion 4c integrally formed on the upper mating surface 4a of the cylinder head 4, and a bolt 11 is attached to the bearing portion 4c.
Intake and exhaust cam caps 9 and 1 that are detachably fastened
It is rotatably supported by 0.

Here, of the exhaust cam cap 10, the exhaust cam cap 10 arranged at an end portion (the lower end portion in FIG. 2) on the side of a timing sprocket, which will be described later, has a boss portion 10a for mounting a solenoid valve, which will be described later, and a hydraulic pressure. A boss portion 10b for forming a passage is integrally bulged. Reference numerals 7b and 8b denote intake and exhaust cam noses, and three intake cam noses 7b and two exhaust cam noses 8b are formed per cylinder.

An intake cam sprocket 12 is provided at the end of the intake cam shaft 7 on the timing sprocket side (lower end in FIG. 2).
Is mounted so as to rotate together with the cam shaft 7 by a key connection or the like, and is fixed by a bolt 13. The intake cam sprocket 12 is connected by a transmission chain 15 to an exhaust cam sprocket 14 mounted on the end of the exhaust cam shaft 8 so as to rotate together with the cam shaft 8 by key connection or the like.

A timing sprocket 16 is provided outside the exhaust cam sprocket 14 of the exhaust cam shaft 8.
Are mounted so as to be rotatable relative to the exhaust cam shaft 8. The timing sprocket 16 is connected by a timing chain 19 to a crank sprocket 18 keyed to a crank shaft 17 arranged at the lower portion of the cylinder block 2. The camshafts and crankshafts may be connected via gears.

Each sprocket, chain and the like are provided with an end surface opening 4e of the cylinder head 4, a chain cover 32 detachably attached to the end surface opening 2c of the cylinder block 2, and an upward bulging portion 5a of the head cover 5. The cam chamber D, which is covered with the chain cover 32, the bulging portion 5a, and the end faces of the cylinder head 4 and the cylinder block 2, is surrounded by the upper mating surface 4a of the cylinder head 4 and the head cover 5. A chain chamber B communicating with the oil pan 3 is formed. The head cover 5
3, the top wall portion 5b located in a portion other than the bulging portion 5a forming the chain chamber B is formed so as to cover the vicinity of the upper surfaces of the intake and exhaust cam caps 9 and 10 as shown in FIG. Further, a cover portion 5c having a shape along the boss portion 10a is formed at a portion of the exhaust cam cap 10 that faces the boss portion 10a.

The variable mechanism 21 of the variable valve timing device 20 is mounted on the timing sprocket 16 portion. This variable valve timing device 20
Is for rotating the timing sprocket 16 and the exhaust cam shaft 8 relative to each other to change the phases of the two, thereby changing the opening / closing timing of the exhaust valve and the intake valve.

The variable mechanism 21 has a bottomed cylindrical cylinder member 22 fixed to the outer end of the exhaust camshaft 8 with bolts 23, and the cylinder member 22, the timing sprocket 16 and the exhaust formed integrally therewith. A space surrounded by the cylindrical boss portion 16a covering the cam shaft 8 is a cylinder chamber C,
The piston 24 is slidable in the cam axis direction in the cylinder chamber C, and is urged outward by a spring 25 to be inserted and arranged. And the piston 2
4, helical splines 24a, 24b having opposite twist directions are formed on the outer peripheral surface of the boss 4, and mesh with helical splines formed on the outer peripheral surface of the boss portion 16a and the inner peripheral surface of the cylinder member 22, respectively. ing. 2
Reference numeral 6 is a cover for sealing the sliding surface between the cylinder member 22 and the timing gear 16.

Further, as schematically shown in FIGS. 5 and 6, one end of a hydraulic passage 27a bored in the exhaust cam shaft 8 is opened in the cylinder chamber C, and the hydraulic passage 27a is opened.
The other end of is connected to one end of a hydraulic passage 27b formed in the exhaust cam cap 10 at the outer end. The other end of the hydraulic passage 27b communicates with one end of a hydraulic passage 27c formed in the cylinder block 2, and the hydraulic passage 27c is
The oil pan 28, the oil pump 29, and the oil strainer 30 communicate with the inside of the oil pan 3.

The hydraulic passage 27b formed in the exhaust cam cap 10 is divided into a variable mechanism side portion 27b 'and a pump side portion 27b''by a valve hole 10c formed in the boss portion 10a. The valve hole 10c
Is parallel to the bisector a of the V bank A, and the lower end opening of the valve hole 10c is above the oil groove 4d formed in the upper mating surface 4a of the cylinder head 4. Is located in. The oil groove 4d is for allowing the return oil from the valve hole 10c to flow down into the chain chamber C in which the transmission chain 19 is arranged.

The valve portion 31a of the solenoid valve 31 is inserted into the valve hole 10c. Further, a valve body 31b is arranged in the valve portion 31a so as to be able to move forward and backward, and when the valve body 31b moves to the upper end (the position in FIG. 5), the hydraulic passage 27b 'communicates with 27b''and the lower end thereof. (Position in FIG. 6) When moved, the hydraulic passage 27b 'is discharged to the discharge port 31d.
It is adapted to communicate with the chain chamber B via the.

The coil housing portion 31c of the solenoid valve 31 penetrates the cover portion 5c of the head cover 5 and is located outside. A seal member 33 made of an elastic material such as rubber is provided between the cover portion 5c and the solenoid valve 31 (see FIG. 4). As a result, sealing is performed without impairing the floating support of the head cover 5.

Here, the axis b of the solenoid valve 31 is
Is parallel to the V bank bisector a, that is, the solenoid valve 31 is arranged vertically. The solenoid valve 31 is located in the engine projection plane in the bisector direction.

Further, the valve portion 31 of the solenoid valve 31
The upper end portion of the valve hole 10c in which a is disposed is located at the highest position, that is, higher than the cylinder chamber C of the variable mechanism 21, when viewed in the entire hydraulic passage. It is easy to collect in this valve hole 10c part. Further, the discharge port 31d from the valve portion 31a is located at the lowest position when viewed in the cam chamber D as a whole, so that the hydraulic oil discharged from the discharge port 31d is mostly retained in the cam chamber D. Instead, it immediately returns to the oil pan 3 through the chain chamber B.

Next, the function and effect of the apparatus of this embodiment will be described. The rotation of the crankshaft 17 is transmitted to the exhaust camshaft 8 via the timing chain 19 and the timing sprocket 16 after being reduced in speed to 1/2 the rotational speed, and the rotation of the exhaust camshaft 8 is transmitted to the exhaust cam sprocket 14 and the transmission chain 1.
5, and the intake cam sprocket 12 transmits the same speed to the intake cam shaft 7, and the intake and exhaust valves are opened and closed at predetermined opening and closing timings by the cam noses 7a and 8a of the intake and exhaust cam shafts 7 and 8, respectively.

In this case, in order to change the valve opening / closing timing, the solenoid valve 31 of the variable valve timing device 20 is turned on and the valve body 31b is raised as shown in FIG. Then, the hydraulic passage 27b 'communicates with 27b''and is cut off from the discharge port 31d. As a result, the hydraulic oil discharged from the oil pump 29 is supplied to the cylinder chamber C of the variable mechanism 21 through the hydraulic passages 27c, 27b ″, 27b ′, and 27a. The supplied hydraulic pressure moves the piston 24 to the right in FIG. 5, whereby the timing sprocket 16 and the cylinder member 22 fixed to the exhaust cam shaft 8 relatively rotate, and the phases of both are changed. This relative rotation is also transmitted to the intake camshaft 7 via the transmission chain 15. As a result, the valve opening / closing timings of both the exhaust cam shaft 8 and the intake cam shaft 7 change.

To restore the valve opening / closing timing, the solenoid valve 31 is turned off and the valve element 31b is lowered as shown in FIG. Then, the hydraulic passage 27b 'communicates with the discharge port 31d, and the hydraulic passage 27b''is shut off. As a result, the hydraulic oil in the cylinder chamber C is discharged from the discharge port 31d through the hydraulic passages 27a and 27b '.
The piston 24 returns to its original position by the urging force of the spring 25, and as a result, the exhaust camshaft 8 and the timing sprocket 1
The phase difference of 6 disappears, and the valve opening / closing timing returns to the original state. At this time, the opening / closing timing of the intake valve also returns to the original state. The hydraulic oil discharged from the discharge port 31d is discharged to the lowest position in the cam chamber D, and the oil groove 4
It immediately returns from d to the oil pan 3 through the chain chamber B.

According to this embodiment which operates in this way, V
Since the timing sprocket 16 having a large diameter is attached to the exhaust camshaft 8 arranged outside when viewed from the bank A, and the variable mechanism 21 is arranged on the timing sprocket 16 portion, the intake system on the V bank A side, etc. The variable mechanism 21 can be reasonably arranged in the projection plane of the timing sprocket 16 in the cam axis direction without affecting the arrangement space, and the expansion of the engine width can be avoided. By the way, when a timing sprocket is mounted on the intake camshaft 7 arranged on the V bank A side, the V bank inner space is narrowed by a large space for disposing the timing sprocket. It is necessary to take measures such as increasing the V bank angle in order to avoid interference with other types, and there is a concern that the engine width will increase.

Further, the exhaust cam shaft 8 is arranged closer to the oil pan 3 than the intake cam shaft 7 due to its arrangement structure. Since the exhaust cam shaft 8 is provided with the variable mechanism 21, the intake cam shaft 7 is provided. In comparison with the case of the above, the hydraulic passage length, and hence the passage volume, can be made smaller, so that the rise of hydraulic pressure can be accelerated.

Further, in the present embodiment, the solenoid valve 31 for switching the supply or discharge of the hydraulic pressure to the variable mechanism 21.
Since the engine is mounted on the exhaust cam cap 10 in the vertical direction, it is possible to avoid the problem that the length of the engine in the crankshaft direction becomes longer due to the mounting of the solenoid valve 31. Incidentally, in the case of the conventional device in which the solenoid valve is arranged outside the variable mechanism mounted on the end of the cam shaft in the direction of the cam shaft, there is a problem that the entire length of the engine becomes longer by the length of the solenoid valve.

Further, since the solenoid valve 31 is attached to the exhaust cam cap 10, it is easier to secure a space for arranging the valve as compared with the case where the solenoid valve is directly attached to the cylinder head, and when the solenoid valve 31 is directly attached to the cylinder head. It is necessary to provide a sealing surface, a fixing boss, etc. inside the cylinder head, but this is not necessary in the present embodiment, so the cylinder head of this embodiment does not include a variable valve timing device. Since the structure is almost the same as that of a normal cylinder head, parts can be shared.

Furthermore, in this embodiment, since the solenoid valve 31 is arranged parallel to the bisector a of the V bank A, the solenoid valve 31 is connected to the bisector a.
Can be easily arranged in the engine projection plane of the direction, and the expansion of the width of the engine in the direction perpendicular to the crank axis can be avoided.

Further, in this embodiment, since the upper end of the valve hole 10c in which the valve portion 31a of the solenoid valve 31 is disposed is located at the highest position of the entire hydraulic passage, The air can be discharged from the valve hole 10c, and the air can be easily and surely removed.

When the solenoid valve 31 is arranged at a high place as described above, the coil housing portion 31c of the solenoid valve 31 is projected to the outside of the head cover 5, so that overheating of the coil can be avoided and the head cover 5 can be prevented.
Can be prevented from increasing in size. Further, since the sealing between the head housing 5 and the coil housing portion 31c is performed by the sealing material 33 made of an elastic material such as rubber, the floating property of the head cover 5 is not impaired.

Furthermore, since the discharge port 31d of the solenoid valve 31 is located at the lowest position of the cam chamber D as a whole, the working oil discharged from the discharge port 31d immediately flows down into the chain chamber B. It is possible to reduce the total required amount of hydraulic oil.

In the above embodiment, the case where the opening / closing timing of the intake valve is changed when the opening / closing timing of the exhaust valve is changed has been described. However, the opening / closing timing of the exhaust valve is fixed and the opening / closing timing of the intake valve is fixed. It is also possible to make only the variable, and the inventions of claims 4 and 5 are made in this way.

7 to 9 are views for explaining the second embodiment according to the invention of claims 4 and 5, and the same reference numerals as those in FIGS. 1 to 6 designate the same or corresponding parts. An exhaust cam sprocket 14 and a timing sprocket 16 are mounted on the exhaust cam shaft 8 by a pin 14a so as not to rotate, and fixed by bolts 13.

An intake cam sprocket 12 is mounted on the intake cam shaft 7 so as to be rotatable relative to the intake cam shaft 7. The above-mentioned variable mechanism is provided with an extension of the boss portion of the intake cam sprocket 12. A variable mechanism 20 ′ similar to 20 is attached. The solenoid valve 31 'is arranged on the boss portion 9a of the intake cam cap 9'so that its axis b'is substantially perpendicular to the bisector a, that is, substantially horizontal. The intake cam cap 9'is provided with cap portions 10d, 10e arranged between the intake cam noses 7b, 7b.
And a cap portion 9e arranged at the outer end are integrally formed, and the boss portion 9a is formed in a bridge-like portion between the cap portions 10e and 9e. As a result, the support rigidity of the solenoid valve 31 'can be improved as compared with the overhang type support structure of the first embodiment.

Further, as shown in FIG. 7, the timing sprocket 16 and the flange portion 2 of the variable mechanism 20 '.
1a is located so that a part thereof overlaps when viewed in the cam axis direction. As a result, the intake cam shaft 7 and the exhaust cam shaft 8 can be arranged close to each other, the angle between the intake and exhaust valves can be reduced, the combustion chamber can be made compact, and the compression ratio can be improved.

As described above, in this embodiment, only the opening / closing timing of the intake valve can be made variable, and the variation of the opening / closing timing can be expanded in combination with the first embodiment described above.

[0047]

According to the invention of claim 1, since the timing member is attached to the exhaust cam shaft arranged outside the V bank, the arrangement inside the V bank as in the case where the timing member is arranged on the intake cam shaft side. Since the problem of interference with parts can be avoided and a variable mechanism that changes the phase between the timing member and the exhaust cam shaft is attached to the exhaust cam shaft, this variable mechanism is not possible within the projection plane of the timing member in the cam axis direction. Therefore, it is possible to avoid the expansion of the engine width when the variable valve timing device is adopted in the V-type engine.

According to the second and fifth aspects of the present invention, the changeover valve for changing over the supply and discharge of the hydraulic pressure to the variable hydraulic mechanism is mounted on the bearing cap constituting the cam bearing. Has the effect of avoiding the problem of lengthening due to the mounting of the switching valve, and has the effect of easily securing the space for arranging the switching valve and simplifying the structure as compared with the case where the switching valve is directly attached to the cylinder head .

According to the third aspect of the invention, since the switching valve is arranged in the direction of the bisector of the V bank,
This switching valve can be easily arranged on the engine projection plane in the bisector direction, and there is an effect that the expansion of the engine width due to the provision of the switching valve can be avoided.

According to the fourth aspect of the present invention, since the variable mechanism for relatively rotating the intake cam transmission member which is relatively rotatably mounted on the intake cam shaft is mounted on the intake cam shaft, the phase of only the intake cam shaft is changed. Thus, there is an effect that the opening / closing timing of only the intake valve can be changed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional front view of an engine equipped with a variable valve timing device according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional plan view of the device of the first embodiment.

FIG. 3 is a partially sectional front view of the device of the first embodiment (see FIG.
III-III line sectional view).

FIG. 4 is a partial cross-sectional front view of the device of the first embodiment (cross-sectional view taken along the line IV-IV in FIG. 2).

FIG. 5 is a schematic diagram for explaining the operation of the device of the first embodiment.

FIG. 6 is a schematic diagram for explaining the operation of the first embodiment device.

FIG. 7 is a cross-sectional plan view of a second embodiment device according to the invention of claims 4 and 5.

FIG. 8 is a front view of the second embodiment device.

9 is a sectional view taken along line IX-IX in FIG.

[Explanation of symbols]

 1 V-type engine 7 Intake cam shaft 8 Exhaust cam shaft 10 Exhaust cam cap (bearing cap) 12 Intake cam sprocket (Intake cam transmission member) 14 Exhaust cam sprocket (Exhaust cam transmission member) 16 Timing sprocket (Timing member) 18 Crank sprocket (Crank transmission member) 20 Variable valve timing device 21 Variable mechanism 24 Piston 31 Solenoid valve (switching valve) AV bank a Bisecting line

Claims (5)

[Claims] 1. A variable valve timing apparatus for an engine, wherein a plurality of cylinders are arranged to form a V bank, an intake cam shaft is arranged inside the V bank, and an exhaust cam shaft is arranged outside the V bank. An exhaust cam transmission member provided on the exhaust cam shaft and an intake cam transmission member provided on the intake cam shaft are connected to each other, and a timing transmission member mounted on the exhaust cam shaft for relative rotation and a crank shaft are provided. A variable mechanism that changes the valve timing by connecting the crank transmission member and rotating the exhaust cam shaft and the timing transmission member relative to each other so as to be located in the axial projection plane of the timing transmission member. A variable valve timing device for an engine, which is provided. 2. The hydraulic mechanism according to claim 1, wherein the variable mechanism is configured to relatively rotate the timing transmission member and the exhaust cam shaft by axial movement of a piston driven by hydraulic pressure. A variable valve timing device for an engine, wherein a switching valve for switching between supply and discharge of the engine is mounted on a bearing cap of an exhaust camshaft. 3. The switching valve according to claim 2, wherein:
A variable valve timing device for an engine, wherein the variable valve timing device is arranged substantially parallel to the bisector of the V bank. 4. A variable valve timing device for an engine, wherein a plurality of cylinders are arranged to form a V bank, an intake cam shaft is arranged inside the V bank, and an exhaust cam shaft is arranged outside the V bank. An exhaust cam transmission member provided on the exhaust cam shaft and an intake cam transmission member rotatably mounted on the intake cam shaft are connected to each other, and a timing transmission member provided on the exhaust cam shaft and a crank shaft are provided. And a crank transmission member, and a variable mechanism for changing valve timing by relatively rotating the intake cam shaft and the intake cam transmission member is arranged on the intake cam shaft. Variable valve timing device. 5. The variable mechanism according to claim 4, wherein the variable mechanism is configured to relatively rotate the intake cam transmission member and the intake cam shaft by axial movement of a piston driven by hydraulic pressure. A variable valve timing device for an engine, wherein a switching valve for switching supply or discharge of hydraulic pressure is mounted on a bearing cap of an intake camshaft.