JPH06307216A - High and low speed switching mechanism in valve system of internal combustion engine - Google Patents

Abstract

PURPOSE:To make the valve timing accurate by preventing the shift of the valve timing by means of a high and low speed switching mechanism in the valve system of an internal combustion engine and to increase the valve lift to be generated by a high speed cam. CONSTITUTION:The allowable projecting amount of a cam nose part 37 of a high speed cam 35 not affecting the timing of an intake/exhaust valve is increased by the phase wherein the cam nose part 37 of the high speed cam 35 from the valve lift starting to the valve lifting is rotated later than a cam nose part 34 of the low speed cam 32 in the operating state of the low speed cam 32, thereby the adverse effect on the timing can not be easily avoided. On the other hand, the cam nose part 37 of the high speed cam 35 is retreated to the part where the valve opening and closing is not affected until the valve lift and synchronized with the cam nose part 34 of the low speed cam 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating device for opening and closing an intake / exhaust valve of an internal combustion engine by rotating a cam, and more particularly to a mechanism for switching between a low speed cam and a high speed cam.

[0002]

2. Description of the Related Art Conventionally, the variable cam mechanism utilizing a cam shaft in the disclosed direct drive type valve operating device can be roughly classified into the following two types.

For example, Japanese Patent Laid-Open No. 62-131907, Japanese Patent Laid-Open No. 2-223616, and Japanese Utility Model Laid-Open No. 3-7700.
As shown in Japanese Patent Publication No. 5, a variable cam piece idles relative to a cam shaft, and a pin or the like is inserted into or removed from the variable cam piece so that the cam piece can be in a locked state or an unlocked state. A type that can be switched.

For example, as shown in JP-A-1-157211 and JP-A-1-167405, the cam nose portion of the variable cam piece moves in a direction orthogonal to the rotation center of the cam shaft.

The problems of these items are summarized as follows. Problems of the variable cam mechanism related to the above type When a non-rotating cam piece is rotated integrally with a high-speed rotating cam shaft by inserting and removing pins, etc., the pins and cam pieces receive a significant impact force, causing abnormalities. It cannot be designed so that it can be worn or damaged and can function in practice. In addition, since the relative rotational speed difference between the cam piece and the cam shaft is large, there is a problem that the pin bounces when inserted and switching cannot be performed.

In order to avoid the basic problem resulting from such a large difference in relative rotational speed, there has been proposed a variable cam mechanism of the above-mentioned type for switching the cam piece and the cam shaft in a synchronously rotating state.

Problems of Variable Cam Mechanism According to the Above-mentioned Form First, the main points of the structure of this form are summarized as follows.
Has a detent mechanism to prevent the cam piece and the cam shaft from rotating relative to each other, and the cam nose portion moves in the radial direction of the cam shaft along the detent mechanism. Second, the hydraulic pressure at the time of switching. The cam nose portion is projected by the cam nose portion, and the pin is inserted into and fixed to the hole provided in the cam nose portion substantially in the axial direction of the cam shaft.
In addition, the cam piece is roughly half-divided into the cam nose portion and the cam base circular portion in consideration of the assemblability to the cam shaft, and the assembly is assembled to the cam shaft and then fastened.

However, since the cam piece is divided in half,
The cam piece is structurally low in rigidity and is easily deformed by hydraulic pressure. Due to the deformation and inclination due to the gap on the sliding surface of the cam piece, it is difficult to center the pin and the insertion hole on the cam nose portion side, and it takes time to switch the pin. Therefore, the cam piece itself receives the hydraulic pressure until the pin insertion is completed, and due to the hydraulic pressure, the cam piece cannot smoothly return to the original closed state even when receiving the valve opening reaction force from the intake and exhaust valves. At this time, the low-speed cam integrated with the cam shaft and the movable high-speed variable cam become mathematically discontinuous surfaces to push down the valve lifter, causing abnormal movement of the valve and producing abnormal noise. Problem arises.

In order to avoid this problem, it is necessary to switch quickly and surely. Therefore, it is necessary to increase the clearance of the pin insertion hole in the cam piece to facilitate the insertion of the pin, or to increase the projection speed of the cam nose portion by setting the clearance on the sliding surface of the cam piece large. .

However, if these gaps are made large, the impact force applied to the pins and the cam pieces due to the torque fluctuation of the cam shaft becomes large, and their wear becomes large, resulting in a serious obstacle to the reliability of the mechanism.

The problem caused by this torque fluctuation is basically an unavoidable problem because the insertion gap cannot be eliminated by the pin insertion method, and this gap setting is very important.

Next, since the outer diameter of the pin cannot be increased due to the fact that the pin is inserted into the cam nose portion, a large hydraulic pressure is required for inserting the pin, which cannot be driven by an ordinary engine oil pump, and the entire engine cannot be driven. The scale of remodeling is also large and the cost is high. Further, it is necessary to make the precision of the parts extremely high, and for that purpose, it is necessary to select an assembly part, and the cost itself becomes a big obstacle.

[0013]

As described above, the conventional mechanism has various problems, but the present invention, which is of the type described above, intends to solve the following problems. is there.

That is, in order to further increase the valve lift in the operating state of the high speed cam as compared with the valve lift in the operating state of the low speed cam, for example, the cam nose portion of the high speed cam from the center of rotation of the cam shaft. It is conceivable to increase the difference between the radius up to and the radius up to the cam nose portion of the low speed cam. In this case, the centrifugal force applied to the cam nose portion of the high-speed cam due to the rotation of the cam shaft also becomes large, so that the centrifugal force between the force that pulls the cam nose portion of the high-speed cam back toward the center of rotation of the cam shaft and the centrifugal force. The balance changes, the speed at which the cam nose portion of the high speed cam moves toward the center of rotation of the cam shaft becomes slow, and the cam nose portion of the high speed cam cannot follow the rotation of the cam nose portion of the low speed cam. Therefore, the cam nose portion of the high speed cam is not sufficiently retracted when the valve lift is started in the operating state of the low speed cam, and the valve opening operation is not smoothly performed under the influence of the cam nose portion of the high speed cam.

An object of the present invention is to prevent such deviation of the valve timing to make the valve timing accurate, and to increase the valve lift by the high speed cam accordingly.

[0016]

In a high / low speed switching mechanism in a valve operating system for an internal combustion engine according to the present invention, a low speed cam and a high speed cam are juxtaposed on a cam shaft which rotates in synchronization with a crankshaft. At the same time, the cam nose portion of the high-speed cam is movable with respect to the cam nose portion of the low-speed cam in the radial direction orthogonal to the rotation center of the cam shaft. A means for moving the cam nose portion of the high speed cam in accordance with the operating state is provided, and the high speed cam moving means changes the position of the cam nose portion of the high speed cam with respect to the rotation center of the cam shaft. And a high-speed cam operating state can be switched. The rotational movement of these cams is transmitted by the interlocking mechanism as opening / closing movement of the intake valve or the exhaust valve of the internal combustion engine.

A means for rotating the cam nose portion of the high speed cam so as to delay the cam nose portion of the low speed cam by a predetermined angle when the valve lift is started in the operating state of the low speed cam so as to cause a phase shift between the cam nose portions. Is provided. Further, during the valve lift, there is provided means for rotating the cam nose portion of the high speed cam with respect to the cam nose portion of the low speed cam so as to advance the cam nose portion by the predetermined angle so as to synchronize the both cam nose portions with each other. Further, at the time of valve lift, there is provided means for making the radius from the rotation center of the cam shaft to the cam nose portion of the high speed cam equal to or smaller than the radius to the cam nose portion of the low speed cam.

[0018]

Therefore, in the low speed cam operating state, the cam nose portion of the high speed cam rotates later than the cam nose portion of the low speed cam between the start of the valve lift and the valve lift. The allowable protrusion amount of the cam nose portion of the high-speed cam that does not affect the valve opening / closing timing becomes large, and it is easy to avoid the adverse effect on the timing. On the other hand, by the time of valve lift, the cam nose portion of the high speed cam retracts to a position where it does not affect the opening and closing of the valve and synchronizes with the cam nose portion of the low speed cam.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A valve operating system for an internal combustion engine according to an embodiment of the present invention will be described below with reference to the drawings.

This embodiment is embodied in a 4-cycle in-line 4-cylinder engine, and in each cylinder shown schematically in FIG.
Is a cylinder, 2 is a piston, 3 is a combustion chamber, 4 is an intake port, 5 is an intake valve, 6 is an exhaust port, 7 is an exhaust valve, 8 is a fuel injection nozzle, and 9 is a spark plug. A direct drive type DOHC is adopted as the valve operating system 10 of this embodiment, and a pair of intake side high / low speed switching cam mechanisms 13 including high speed cam moving means are attached to the intake side cam shaft 11 in each cylinder. At the same time, a pair of exhaust side high / low speed switching cam mechanisms 14 including high speed cam moving means are attached to the exhaust side cam shaft 12. A pair of the intake valve 5 and the exhaust valve 7 are provided in each cylinder, the pair of intake valves 5 correspond to the pair of intake-side high / low speed switching cam mechanisms 13, and the pair of exhaust valves 7 include the pair of exhausts. It corresponds to the side high / low speed switching cam mechanism 14.

The cylinder unit 15 shown in FIG. 2 is assembled on each of the intake side and the exhaust side in each cylinder, and the following description of the cylinder unit 15 is common to the intake side and the exhaust side.

A journal 17 is provided at the center of the shaft body 16 between the pair of high / low speed switching cam mechanisms 13-13 or 14-14.
The connecting cylinder 19 is press-fitted and fixed to the outer periphery of the connecting end portion 18 of the shaft body 16 outside the shafts 3, 14. A main cylinder 20 is provided through the shaft body 16 in the axial direction thereof, and an oil supply hole 21 formed in the journal 17 communicates with the cylinder 20. Deformed pistons 22 are fitted in the cylinder 20 in correspondence with the pair of high and low speed switching cam mechanisms 13 and 14, so that the deformed pistons 20 can move in the cylinder 20 in the axial direction of the shaft body 16. Has become.

In the deformed piston 22, as shown in FIG. 4, a piston main body 23 is formed at one end thereof, and an oil supply groove 25 is formed between both wall portions 24 from the piston main body 23 to the other end. A notch 26 is formed on the piston body 23 adjacent to the oil supply groove 25. At the inner bottom of the oil supply groove 25, a deep recess 27 is formed in the piston main body 2.
3, an oblique pressing surface 28 is formed from the recess 27 to the other end side of the deformed piston 22 so that the depth of the oil supply groove 25 gradually becomes shallow. A chamfer 29 is formed on both wall portions 24.

A plug 30 is press-fitted and fixed in the connecting end portion 18 of the shaft body 16. A return spring 31 is fitted between the inside of the plug 30 and the inside of the piston body 23, and the deformed piston 22 is urged toward the center of the shaft body 16 by the elastic force of the return spring 31.

A journal 1 is provided on the outer periphery of the shaft body 16.
A low speed cam 32 is integrally formed on both sides of the low speed cam 7, and a base circle portion 33 and a cam nose portion 34 are formed in series on the outer periphery of the low speed cam 32 as shown in FIG. A tubular high-speed cam 35 is provided between the low-speed cam 32 and the connecting cylinder 19.
Is inserted into the outer periphery of the shaft body 16 and the low speed cam 32
Are arranged in parallel with each other. This high speed cam 35
A base circle portion 36 and a cam nose portion 37 are also formed in series on the outer periphery of the high speed cam 35 so that the base circle portion 36 of the high speed cam 35 is adjacent to the base portion 33 of the low speed cam 32 and the cam nose of the high speed cam 35 is formed. The portion 37 is adjacent to the cam nose portion 34 of the low speed cam 32.

Inside the high-speed cam 35, a sub-cylinder 38 is provided in the shaft body 16 so as to extend in a radial direction orthogonal to the axis of the shaft body 16, and the sub-cylinder 38 communicates with the main cylinder 20. is doing. A sub-piston 39 is fitted in the sub-cylinder 38 and is movable in the radial direction. A pair of arms 40 is projectingly provided on the sub-piston 39, and a roller 41 is rotatably supported by a support shaft 42 between the arms 40. The arms 40 are inserted into the recess 27 between the wall portions 24 of the deformed piston 22, and the roller 41 is in contact with the inner bottom surface of the recess 27. Since both wall portions 24 of the deformed piston 22 hit the arm 40, the deformed piston 22
Does not rotate. Since there are chamfers 29 on both wall portions 24, both arms 40 can be easily inserted into the oil supply groove 25.

A pressing pin 43 is inserted inside the cam nose portion 37 of the high speed cam 35.
3 and the sub-piston 39 between the return spring 44
Is pressed in and the pressing pin 43 is pressed against the inside of the cam nose portion 37 by its elastic force. A pressing pin 45 is inserted inside the base circle portion 36 of the high speed cam 35 on the center of the sub-cylinder 39, and a return spring 46 is fitted between the pressing pin 45 and the shaft body 16 to press the pressing pin 45. 45 is the base circle part 36
Is pressed inside. Therefore, the high-speed cam 35 is supported by the sub-piston 39, both return springs 44 and 46, and both pressing pins 43 and 45 with respect to the shaft body 16 and the deformed piston 22, and is moved to the low-speed cam 32 in the radial direction of the shaft body 16. It becomes possible to move along. The cutout portion 26 of the deformed piston 22 has a sub-piston 39.
This is to avoid interference with.

This cylinder unit 15 is prepared for each of the intake side and the exhaust side by the number of cylinders. Then, each cylinder unit 1 is also used as the connecting cylinder 19 between both adjacent units 15.
5 are connected to each other and an intake side camshaft 11 having four sets of intake side high / low speed switching cam mechanisms 13 and an exhaust side camshaft 1 having four sets of exhaust side high / low speed switching cam mechanisms 14
It becomes 2.

As shown in FIGS. 1 and 5, the journal 17 of the shaft body 16 is supported by a half-split bearing portion 47 on the head of the cylinder 1. A valve lifter 49 is slidably supported by a lifter bore 48 in the head of the cylinder 1, and a shim 50 on the valve lifter 49 can contact the low speed cam 32 and the high speed cam 35. A valve spring 51 is fitted between the head of the cylinder 1 and the valve lifter 49, and the elastic force of the valve spring 51 causes the intake and exhaust valves 5 and 7 to close the intake and exhaust ports 4 and 6. The valve lifter 49 and the valve spring 50 constitute an interlocking mechanism for opening / closing the intake / exhaust valves 5, 7.

As shown in FIG. 3, the shape of the inner peripheral surface along the outer peripheral surface of the high speed cam 35 is such that the outer peripheral shape of the shaft main body 16 and the outer peripheral surface of the low speed cam 32 face the inner peripheral surface. The low speed cam 3 is determined by the relative relationship between
High speed cam 3 when opening and closing intake and exhaust valves 5, 7 by 2
5 may geometrically prevent the intake and exhaust valves 5 and 7 from opening and closing. That is, as shown in FIG. 9 and FIG. 6, the return springs 44, 46 in the pressing pins 43, 45
In the most contracted state, within a difference between the diameter L from the rotation center of the shaft body 16 to the outermost surfaces of the pressing pins 43 and 45 and the radius R of the outer peripheral surface of the low speed cam 32, The thickness T is set. Also, the shaft body 1
The outer peripheral shape of 6 is formed in a perfect circular shape having the same center as the rotation center of the shaft body 16 except for the mounting portions of the pressing pins 43 and 45, and mass productivity is taken into consideration. The inner peripheral surface of the high-speed cam 35 is line-symmetric with respect to the center line connecting the pressing pins 43 and 45 through the center of rotation of the shaft body 16 and is in contact with the outer peripheral surface of the shaft body 16. The guide surface 52 between a and b has a planar shape, and the length between the points a and b is set to be equal to or larger than the maximum movement range of the high speed cam 35 with respect to the low speed cam 32. The guide surface 53, which is continuous with the guide surface 52 at the points a and b, has an arc shape that can follow the outer peripheral surface of the shaft body 16. Further, the guide surfaces 54 and 55 that come into contact with the pressing pins 43 and 45 have an arcuate shape in accordance with them, and are smoothly continuous with the respective guide surfaces 53.

Although not shown, a hydraulic regulator is connected to the oil supply hole 21 of the shaft body 16, and the oil supply to the hydraulic pressure regulator is controlled by the operation of the electromagnetic switching valve so that the oil is supplied from the oil supply hole 21 into the main cylinder 20 or the sub-cylinder 38. The supplied hydraulic pressure is adjusted.

First, the case where the intake / exhaust valves 5, 7 are opened / closed by the low speed cam 32 under a low control oil pressure will be described in detail. When the intake side high / low speed switching cam mechanism 13 or the exhaust side high / low speed switching cam mechanism 14 is in the state of FIGS. 5 and 6, the intake / exhaust valves 5, 7 are closed. In this state, a small setting gap is provided between the base circle portion 32 of the low speed cam 32 and the shim 50, but the base circle portion 36 of the high speed cam 35 presses the reaction force of the return spring 46 against the pressing pin 45. Since it is received via, it rotates while being in contact with the shim 50. But,
The reaction force of the return spring 46 is the valve spring 51.
Since the elastic force is sufficiently smaller than the elastic force, the base circular portion 33 does not open the intake and exhaust valves 5, 7.

On the other hand, the high-speed cam 35 projects along the radial direction of the shaft body 16, and the gap between the cam nose portion 37 and the shaft body 16 is maximized. In that case,
Since the pressing pin 43 is pressed by the guide surface of the cam nose portion 37 by the extension 54 of the return spring 44,
The high speed cam 35 is stabilized, and the phases of the cam nose portion 37 and the cam nose portion 34 of the low speed cam 32 do not deviate from each other.

In the sub-cylinder 38, the hydraulic pressure applied to the sub-piston 39 is controlled by a pressure regulating valve (not shown), and the return spring 44 has an elastic force higher than the hydraulic pressure. Not fixed.

The shaft body 16 rotates in the direction of the arrow, and the states shown in FIGS. 7 to 10 are sequentially reached. In the state shown in FIG. 7, the cam nose portions 34 and 37 are on a plane parallel to the upper surface of the shim 50. In this state, both pressing pins 4
Since no external force acts on 3,45, high speed cam 3
The base circle portion 36 and the cam nose portion 37 of No. 5 project from the base circle portion 33 and the cam nose portion 34 of the low speed cam 32 to the same extent and are in a neutral state.

FIG. 8 shows a lift start state in which the lift is rotated about 45 degrees from the state shown in FIG. In this state, for example, it is expected that the movement of the high-speed cam 35 cannot follow the rotation speed of the low-speed cam 32 in an operating range close to the upper limit rotation speed of the low-speed cam 32. Therefore, in a state where the cam nose portion 34 of the low speed cam 32 and the cam nose portion 37 of the high speed cam 35 share the tangent line on the shim 50, the center line 37a of the cam nose portion 37 forms an angle with the center line 34a of the cam nose portion 34. The cam nose portion 37 rotates with a delay from the cam nose portion 34 so as to be offset by θ, and they smoothly continue. Therefore, the opening and closing of the intake / exhaust valves 5 and 7 is normally performed only by the low speed cam 32 without being influenced by the high speed cam 35. When the pressing pin 43 contracts the return spring 44 and is most inserted into the sub-piston 39, the pressing pin 43 is pressed by the high-speed cam 35.
It acts as a rotation stop for the phase shift and maximizes the phase shift.

At this point in time, the reaction force of the valve spring 51 causes the component force acting in the direction of the center line 37a of the cam nose portion 37 to become considerably large. Therefore, the component force acting on the return spring 46 on the base circle portion 36 side is counteracted by this component force. The forces oppose each other, and the high speed cam 36 smoothly moves and retreats.

FIG. 9 shows a lifted state in which the intake and exhaust valves 5 and 7 are most opened. During the lift to reach this state, the high speed cam 3
While rotating the cam nose portion 37 of No. 5 so as to advance the cam nose portion 34 of the low speed cam 32 by the angle θ,
The high speed cam 35 retracts smoothly as described above. Therefore, as the phase shift disappears, the low speed cam 3
The cam nose portion 37 of the high-speed cam 35 does not protrude from the cam nose portion 34 of No. 2 and both cam nose portions 34, 3
7 on the shim 50, the radius from the center of rotation of the shaft body 16 to the cam nose portion 37 becomes equal to or smaller than the radius to the cam nose portion 34.

As described above, the guide surface 53 of the outer peripheral surface of the shaft main body 16 and the inner peripheral surface of the high-speed cam 35 which matches the outer peripheral surface thereof.
Since both and are arcuate, the contact area between them is widened, and sufficient damping by the oil film (reduction of vibration amplitude at the resonance point) can be expected. Therefore, no trouble such as abnormal noise occurs.

Further, both the pressing pin 43 and the guide surface 54 of the cam nose portion 37 of the high speed cam 35 which matches the pressing pin 43 are arcuate, and each guide surface 5 of the high speed cam 35 is also formed.
Since 3, 54 are smoothly continuous, the pressing pin 43
Is aligned with the center line 37a of the cam nose portion 37 of the high speed cam 35, and the cam nose portion 34 of the low speed cam 32 is
The phase shift of the cam nose portion 37 of the high speed cam 35 with respect to is reliably eliminated.

From the neutral state (state in which the shaft body 16 is further rotated 180 degrees from the state in FIG. 7) shown by the imaginary line in FIG. 10, the base circular portion 36 of the high speed cam 35 is shim 50.
The state where the upper contact starts is shown by the solid line in FIG. Even in this state, a phase shift occurs between the cam nose portions 34 and 37. At this time as well, since the operation is similar to that described above, the high speed cam 35 moves smoothly and the cam nose portion 37 thereof projects from the cam nose portion 34 of the low speed cam 32.

Further rotation from the state shown in FIG.
It returns to the state shown in FIG. As described in detail above, the intake / exhaust valves 5, 7 can be opened and closed by operating only the low speed cam 32 under a low control hydraulic pressure without being affected by the high speed cam 35.

Next, the case where the intake / exhaust valves 5, 7 are opened and closed by the high speed cam 35 under a high control oil pressure will be described in detail. As shown in FIGS. 11 and 12, the main cylinder 2
0 and the control hydraulic pressure in the sub-cylinder 38 becomes high, the sub-piston 39 is pushed against the elastic forces of the return springs 44 and 46 to move, and the sub-piston 39 pushes the pressing pin 43 to accelerate the movement. It matches the guide surface 54 of the cam nose portion 37 of the working cam 35. Therefore,
The cam nose portion 37 is supported by the pressing pin 43.
At this time, the roller 41 also moves together with the sub-piston 39 and separates from the recess 27 of the odd-shaped piston 22. Therefore, the piston body 23 of the deformed piston 22 is pushed against the elastic force of the return spring 31 and the deformed piston 2
2 moves, and the roller 41 rests on the pressing surface 28 from the recess 27. In this case, the pressing pins 43 and 45 are connected to the guide surface 54 of the cam nose portion 37 of the high speed cam 35 and the base circle portion 3.
Since they are pressed against the guide surfaces 55 of 6, the high speed cam 35 is integrated with the low speed cam 32 and the relative movement between them is eliminated. Therefore, the high speed cam 35
Even if the cam nose portion 37 comes into contact with the shim 50 and a force is exerted on the cam nose portion 37, abnormal wear or abnormal noise due to rattling does not occur.

The larger the angle of inclination of the pressing surface 28 with respect to the center of rotation of the shaft body 16, the closer the roller 41 can be made to the cam nose portion 37 side, and the smaller the amount of movement of the deformed piston 22 is. However, in this case, during the lift shown in FIG.
Since the reaction force of 1 acts on the pressing surface 28, there is a disadvantage that the component force for pushing the deformed piston 22 back against the control hydraulic pressure becomes large. Therefore, a control hydraulic pressure that overcomes the resultant force of this component force and the reaction force of the return spring 31 is required. Therefore,
By suppressing the inclination angle of the pressing surface 28 to about 20 degrees or less,
A normal pressure oil pump is available.

On the contrary, when switching from the operating state of the high speed cam 35 to the operating state of the low speed cam 32,
The reaction force of each of the return springs 31, 44, 46 immediately returns from the state of FIG. 11 to the state of FIG. 5 simply by changing the control oil pressure from high to low.

This embodiment has the following effects. (A) Since the pistons 22 and 39 move in the cylinders 20 and 38 and the operating states of the pressing pins 43 and 45 with respect to the high speed cam 35 are switched simply by changing the control oil pressure,
The switching can be reliably performed.

(B) When switching from low speed to high speed, FIG.
Since the cam nose portion 37 of the high speed cam 35 is in contact with the shim 50 as shown in FIG.
Since the reaction force of 1 is applied to the cam nose portion 37, even if a high control oil pressure is applied to the main cylinder 20 and the sub cylinder 38, the sub piston 3 is driven by the control oil pressure.
The force that moves 9 toward the cam nose portion 37 side defeats the reaction force of the valve spring 51, and the high speed cam 35 cannot be switched. Further, at the time of switching from high speed to low speed, when the cam nose portion 37 of the high speed cam 35 is in contact with the shim 50 as shown in FIG. 13, the main cylinder 20 and the sub cylinder 38 are controlled from high control oil pressure to low control oil. Even if hydraulic pressure is applied, the reaction force of the valve spring 51 acts on the cam nose portion 37, so that the valve spring 51 is pressed between the pressing surface 28 on the deformed piston 22 and the roller 41.
The contact pressure generated by the reaction force of 8 overcomes the reaction force of the return spring 31, and the high speed cam 35 cannot be switched. However, when the cam nose portion 37 begins to separate from the shim 50 and the influence of the reaction force of the valve spring 51 on the cam nose portion 37 becomes small, switching between high speed and low speed becomes possible. That is, there is an advantage that the switching can be performed only when the base circle portion 36 of the high speed cam 35 is in contact with the shim 50. Therefore, a switching timing mechanism for avoiding switching when the cam nose portion 37 of the high speed cam 35 is in contact with the valve lifter 49 is unnecessary.

(C) Since the phase shift of the high speed cam 35 with respect to the low speed cam 32 is allowed in the operating state of the low speed cam 32, the movement of the high speed cam 35 is smoothed and the valve lifter 49 is affected. Without giving, abnormal valve opening and abnormal noise are eliminated.

(D) Since the roller 41 of the sub-piston 39 is pressed against the pressing surface 28 of the deformed piston 22 by utilizing the reaction force of the valve spring 51 while the high-speed cam 35 is in operation, it is basically conventional. Unlike the example, there is no rattling between the cam nose portion 37 of the high-speed cam 35 and the pressing surface 28, wear and the like can be prevented, and reliability becomes extremely high.

(E) Since the outer shape of the shaft body 16 is enlarged and the deformed piston 22 and the sub-piston 39 are inserted therein, the outer shapes of the pistons 22 and 39 are enlarged to increase the switching operation force. It is possible to switch between the pistons 22 and 39 even at a low control oil pressure.

(F) Intake side and exhaust side camshafts 1
It is only necessary to change 1 and 12, and the deformed piston 2
Even if the outer shape of 2 or the sub piston 39 is set to be large, the size of the entire cylinder does not need to be basically changed. Therefore, it is not necessary to change the basic size of the cylinder head, and it is easy to assemble the conventional engine as it is. The variable cam mechanism currently mass-produced is a type that applies a rocker arm. Compared with this, the total height of the cylinder head is 15
It can be made compact about mm.

(G) Since the high speed cam 35 is locked to the low speed cam 32 by receiving the reaction force of the valve spring 51 by the pressing surface 28 of the deformed piston 22, the high speed cam 3 is locked.
Even if the pressing pin 43, the return spring 44, and the sub-piston 39 between the cam nose portion 37 and the pressing surface 28 of FIG. No need to install a special oil pump because it can be switched over with a low control oil pressure, and the outer shapes of the deformed piston 22 and the sub-piston 39 in the shaft body 16 can be enlarged, so that the pistons 22 and 39 can be No special processing is required to increase the operating force, and since the intake side and exhaust side cylinder units 15 only need to be connected according to the number of cylinders, the structure is simple. Since it can be easily mounted on the engine of the cylinder as it is, the modification cost will be low. Since changes's is not necessary, can be lighter without the need to enlarge the engine size, it is possible to reduce the cost reasons such as.

The present embodiment has various advantages as described above, but particularly in the operating state of the low speed cam 32, the following excellent effects are exhibited. That is, as shown in FIG. 8, when the cam nose portion 34 of the low speed cam 32 starts to come into contact with the valve lifter 49, the cam nose portion 37 of the high speed cam 35 is moved at a speed smaller than that of the low speed cam 32. It rotates and delays by the rotation angle θ, causing a phase shift between them. Then, during the lift, the cam nose portion 37 of the high speed cam 35 rotates at a speed higher than that of the cam nose portion 34 of the low speed cam 32 and advances by the rotation angle θ, so that both cam nose portions 34, 37 are aligned with each other. Both cams 32 and 35 are synchronized. Further, during the lift shown in FIG. 9, the radius from the rotation center of the shaft body 16 to the cam nose portion 37 of the high speed cam 35 is equal to or smaller than the radius to the cam nose portion 34 of the low speed cam 32. Therefore, the cam nose portion 37 of the high speed cam 35 does not affect the movement of the valve lifter 49,
The valve timing becomes accurate in the operating state of the low speed cam 32. When the influence of the cam nose portion 37 of the high speed cam 35 is small as described above, the cam nose portion 37 is largely projected from the cam nose portion 34 of the low speed cam 32 in the operating state of the high speed cam 35 so that the intake / exhaust valves 5, 7 are provided. You can also increase the lift.

[0054]

According to the valve operating system for an internal combustion engine of the present invention, the cam nose portion of the high speed cam is more than the cam nose portion of the low speed cam when the valve lift is started by the cam nose portion when the low speed cam is operating. Since it rotates with a delay, the cam nose portion of the high speed cam is allowed to protrude by the phase shift, and the radius from the center of rotation of the cam shaft to the cam nose portion of the high speed cam is the same as the radius to the cam nose portion of the low speed cam. Even if it becomes large, the valve timing becomes accurate without being affected by the cam nose portion of the high speed cam, and the valve lift can be increased in the operating state of the high speed cam.

[Brief description of drawings]

FIG. 1 is a schematic front view showing a valve operating system for an internal combustion engine according to a present embodiment.

FIG. 2 is a cross-sectional view showing a cylinder unit that is a part of an intake side and an exhaust side camshaft in this valve train.

3 is an enlarged partial sectional view taken along line XX of FIG.

4 is a perspective view showing a deformed piston which is one component of the cylinder unit shown in FIG.

5 is a partial cross-sectional view showing a low-speed cam operating state of a cylinder unit, which is a part of the intake side and exhaust side camshafts in which the cylinder units shown in FIG. 2 are assembled by the number of cylinders.

6 is a partial cross-sectional view taken along line YY of FIG. 5, showing a state in which the cam nose portions of the low speed cam and the high speed cam are directed upward in the intake side and exhaust side high / low speed switching cam mechanisms.

FIG. 7 is a partial cross-sectional view showing a state in which the cam has rotated about 90 degrees from the state shown in FIG.

8 is a partial cross-sectional view showing a valve lift starting state in which the cam rotates about 45 degrees from the state of FIG. 7 and the cam nose portion of the high speed cam is out of phase with the cam nose portion of the low speed cam.

9 is a partial cross-sectional view showing a valve lift state in which the cam further rotates from the state of FIG. 8 and the cam nose portion of the high speed cam matches the cam nose portion of the low speed cam.

10 is a partial cross-sectional view showing a state immediately before FIG. 6 in which the cam has further rotated from the state of FIG. 9.

FIG. 11 is a partial cross-sectional view of the cylinder unit in which the low speed cam operating state shown in FIG. 5 is switched to the high speed cam operating state.

12 is a partial cross-sectional view taken along line ZZ of FIG. 11 with the cam nose portion facing upward.

13 is a partial cross-sectional view showing a valve lift state in which the cam has rotated from the state of FIG.

[Explanation of symbols]

5 intake valve, 7 exhaust valve, 10 valve operating device, 11 intake side camshaft, 12 exhaust side camshaft, 13 intake side high / low speed switching cam mechanism, 14 exhaust side high / low speed switching cam mechanism, 15 intake side or exhaust side Cylinder unit, 16 shaft body, 20 main cylinder, 22 deformed piston, 23 piston body, 27 recessed portion, 28 pressing surface,
31 Return Spring, 32 Low Speed Cam, 33
Base circle part, 34 cam nose part, 35 high speed cam,
36 base circle part, 37 cam nose part, 38 sub cylinder, 39 sub piston, 41 roller, 43 pressing pin, 44 return spring, 45 pressing pin, 46 return spring, 49 valve lifter,
51 Valve spring.

Claims (1)

[Claims] 1. A low-speed cam and a high-speed cam are arranged side by side on a camshaft which rotates in synchronization with a crankshaft, and a cam nose portion of the high-speed cam is arranged in a radial direction orthogonal to a rotation center of the camshaft. The cam nose of the high speed cam is provided so as to be movable with respect to the cam nose of the low speed cam, and means for moving the cam nose of the high speed cam according to the operating state is provided. The internal combustion engine is provided with an interlocking mechanism that enables switching between the low-speed cam operating state and the high-speed cam operating state in which the positions of the parts are changed and that transmits the rotational movement of these cams as the opening / closing movement of the intake valve or the exhaust valve of the internal combustion engine. In the engine valve operating system, when the low speed cam is in operation, the cam nose part of the high speed cam becomes the cam nose part of the low speed cam when the valve lift is started. The cam nose portion of the high speed cam is advanced by the predetermined angle with respect to the cam nose portion of the low speed cam while the valve is being lifted. When the valve is lifted, the radius from the center of rotation of the camshaft to the cam nose of the high speed cam is equal to the radius of the cam nose of the low speed cam. A high / low speed switching mechanism in a valve operating system for an internal combustion engine, characterized in that it is provided with a means for increasing or decreasing.