JP7168381B2 - Valve gear with variable valve lift for multi-cylinder internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a valve gear that can change the lift amount of an intake valve, an exhaust valve, or both valves in a multi-cylinder internal combustion engine.

2. Description of the Related Art In an internal combustion engine, it is possible to change the lift amount of an intake valve or an exhaust valve. In Patent Document 1, the cam shaft is composed of a core shaft and a cam carrier (outer cylinder) fitted thereon. The cam carrier is individually arranged for each cylinder, and each cam carrier is formed with a cam portion unit composed of two unit cam portions having different heights (different profiles) from the rotation axis, thereby forming a cam carrier. is moved in the axial direction by an actuator (shifter), two unit cam portions having different heights are selectively brought into contact with a valve-side member such as a rocker arm.

In Patent Document 1, each cam carrier corresponding to each cylinder is provided with a pair of guide grooves, a pair of pins that slide in the guides, and a pair of actuators that drive the pins. By bringing any pin into sliding contact with the inner surface of the groove, any cam carrier can be slid in the axial direction to switch the cam portion contacting the valve-side member, and as a result, the valve lift amount can be changed. can be done.

However, in Patent Document 1, the cam carrier is divided for each cylinder and is individually controlled to slide. Since these members take up a considerable amount of space, there is a problem that the arrangement of other members becomes very troublesome.

As a solution to this problem, in Patent Document 2, one cam carrier is formed so as to straddle a plurality of cylinders, and a set of cam portions (cam unit unit) corresponding to each cylinder is provided on one cam carrier. ) is disclosed.

Japanese Patent Publication No. 2006-520869 JP 2009-228543 A

In claim 1 of Patent Document 2,
"It has a cam carrier provided with a linear groove and a high-lift cam and a low-lift cam, and by sliding an electromagnetic pin in the groove, the cam carrier is slid in the axial direction. A variable valve mechanism for an internal combustion engine capable of switching between high-lift and low-lift cams, wherein the cam carrier is formed across a plurality of cylinders of the internal combustion engine.
is described, but following this,
A first groove for sliding the cam carrier in one direction, a first electromagnetic pin inserted into the first groove, and a A first actuator is provided, and a second groove for sliding the cam carrier in the other direction opposite to the one direction is provided in the portion corresponding to the other cylinder of the cam carrier, and the second groove is inserted into the second groove. and a second actuator for driving the second electromagnetic pin."
is described as
Although it is described that "the cam carrier is formed so as to straddle a plurality of cylinders", as in the embodiment, the cam carrier straddles two cylinders, a portion corresponding to one cylinder and a portion corresponding to the other cylinder. However, there is no disclosure or suggestion of a carrier straddling two or more cylinders and a driving method thereof. Therefore, the effect of reducing the number of parts was still insufficient.

The present invention is made to improve such a situation.

The claimed invention is
“On the camshaft, which rotates in conjunction with the crankshaft, cam unit units, which are composed of unit cam portions with different projecting heights from the base circle, are arranged at multiple locations corresponding to each of the multiple cylinders. are arranged with the
When each cam unit moves axially by a predetermined distance while the cam shaft rotates by a predetermined angle, the drive unit cam portion that is in sliding contact with the rocker arm and other valve-side members is switched to increase the lift amount of the valve. is intended to be changed,
In addition, each of the cam portion units can be simultaneously moved in the axial direction by the predetermined distance to sequentially switch the driving unit cam portions in each cam portion unit.
It has a basic configuration.

And in the above basic configuration,
" The axial width dimension of each unit cam portion in each cam portion unit is set to be an integral multiple of the axial width dimension of the valve-side member, and the width of the tall unit cam portion A cam portion unit whose dimension is larger than the width dimension of a low unit cam portion and a cam portion unit whose width dimension of a high unit cam portion is smaller than the width dimension of a low unit cam portion coexist. and
When each of the cam portion units simultaneously moves by an integral multiple of the width dimension of the valve side member, the valve side member is set so as to always pass the base circle on the boundary line between adjacent unit cam portions. It is done
It is configured.

In the present invention, the structure of the cam shaft may be such that each cam portion unit is formed integrally with one cam shaft, or the cam shaft is slidably fitted on one core shaft. A unit cam portion (cam portion unit) may be formed in the outer cylinder by forming a composite structure with one outer cylinder. When each cam portion unit is formed on the cam shaft itself, the cam shaft is slid in the axial direction.

Since it is usually not allowed to move the camshaft driving device (timing gear, sprocket, pulley, etc.) in the axial direction, the driving device and the camshaft are spline-fitted together. It should be configured such that it is allowed to slide in the axial direction while rotating freely. When the camshaft is formed with a double structure of a core member and an outer cylinder, only the outer cylinder should be slid. In any case, the camshaft or the outer cylinder is slidably held by the bearing portion and the cam cap.

As a method for sliding the cam portion unit in conjunction with the rotation of the camshaft, as in Patent Documents 1 and 2, a guide groove, a pin fitted therein, and an actuator (for example, an electromagnetic A device consisting of a solenoid or a motor) can be used.

When a mechanism consisting of a guide groove and a slide pin is adopted as means for sliding the cam portion unit, if the transition between the unit cam portions is performed while the cam shaft rotates at an angle of less than 180 degrees, high A groove for transitioning from a low-height unit cam portion to a high- height unit cam portion and a groove for transitioning from a high- height unit cam portion to a low -height unit cam portion are formed side by side in the circumferential direction. Therefore, it is possible to change the lift amount with one slide pin and actuator.

When the cam portion unit is slid within a range of rotation angles of 180 degrees or more, a groove for moving the cam portion unit in one direction and a groove for moving the cam portion unit in the other direction are formed separately in the axial direction. good.

As can be understood from the embodiment, the rotation angle of the camshaft for completing switching in each cam portion unit depends first on the number of cylinders, and secondly on the width dimension of the unit cam portion in each cam portion unit. It depends on the relationship with the width dimension of the valve-side member. For example, in the case of a 4-cylinder engine, the switching of each cam portion unit can be completed while the cam shaft rotates once (while it rotates 360 degrees). It is possible not only to switch between high and low, but also to switch between three levels of high, medium, and low.

In the present invention, the specific structure for switching the driving unit cam portion corresponding to the valve-side member while moving each cam portion unit together depends on the number of cylinders and the order of explosion (unit cams in adjacent cam portion units). The difference is in the magnitude of the phase angle of the part). The embodiment exemplifies the case of 3 cylinders and 4 cylinders. Therefore, the features of the present invention can be easily understood by referring to the embodiments .

A cam portion is formed on a portion of the outer periphery of the cam shaft, and the portion other than the cam portion forms a base circle having an equal distance from the axis (that is, a perfect circle). In Patent Documents 1 and 2, the cam portion is moved while the valve-side member such as the rocker arm is in sliding contact with the base circle. While a plurality of cams are connected almost without interruption, valve-side members such as rocker arms are lined up parallel to the cam shaft. It is impossible to pass through the boundary line between adjacent unit cam portions while making them slide in contact with each other.

On the other hand, in the present invention, when the group of cam portion units is moved axially by a predetermined distance in conjunction with the rotation of the cam shaft, the valve-side member must be positioned on the boundary line between adjacent unit cam portions. Since the ratio of the width dimension in the axial direction of each unit cam portion in each cam portion unit is set so as to pass on the base circle, interference between the valve-side member and the unit cam portion does not occur. , the switching of the driving unit cam portions can be sequentially performed from one cam portion unit to another cam portion unit, and the switching of the valve lift amount can be completed in the cam portion units corresponding to all cylinders.

Therefore, the driving device (actuator) for controlling the switching of the unit cam portion can be simplified, contributing to cost reduction and weight reduction, as well as eliminating the erosion of the arrangement space of other members and allowing freedom in the design of member arrangement. sexuality can also be improved. In particular, when the cam shaft completes the sliding of the cam unit within an angle range of less than 180 degrees, if the driving device has a structure consisting of a groove and a pin, the groove for switching from high to low The grooves for switching from low to high can be formed side by side in the circumferential direction, so switching from high to low and switching from low to high can be performed with one type of drive device, resulting in cost reduction and weight reduction effects. is particularly good at

In the case where the driving device has a structure consisting of a guide groove and a pin, when the slide of the cam portion unit is completed within a range of rotation at a rotation angle greater than 180 degrees, a guide groove for switching from high to low; The guide grooves for switching from low to high are arranged in the axial direction, but in this case also, switching from high to low and switching from low to high can be performed by a pair of driving devices, which reduces costs. You can enjoy the effect of weight reduction.

It is a diagram showing the first embodiment applied to a three-cylinder internal combustion engine, (A) is a side view of the whole, (B) is a BB view of (A), (C) is CC of (A) (D) is a DD view of (A). It is a schematic diagram which shows the 1st usage example of 1st Embodiment. It is a schematic diagram which shows the 2nd usage example of 1st Embodiment. It is a schematic diagram of 2nd Embodiment. It is a schematic diagram of 2nd Embodiment. It is a schematic diagram of 3rd Embodiment. It is a schematic diagram of 3rd Embodiment.

(1). Structure of First Embodiment Next, an embodiment of the present invention will be described based on the drawings. First, a first embodiment shown in FIGS. 1 to 3 will be described. This embodiment applies to a three-cylinder internal combustion engine. The camshaft 1 is for intake or exhaust, and includes one core shaft 2 and one outer cylinder 3 fitted thereon. By fitting or the like, they are fitted so as to be slidable in the axial direction and to rotate integrally. One end (front end) of the core shaft 2 that is closer to the timing chain is attached to a part of the driving device that transmits the power of the timing chain, but these structures are omitted in the figure for simplified representation. .

The outer cylinder 3 has a plurality of bearing portions 4, and between the adjacent bearing portions 4, a first cam portion unit 5a, a second cam portion unit 5b, and a third cam portion unit 5c are arranged in order from the front. are provided. Each cam portion unit 5a, 5b, 5c is composed of high unit cam portions 6a, 6b, 6c and low unit cam portions 7a, 7b, 7c corresponding to the fact that each cylinder has a two-valve intake and exhaust valve. It consists of a pair of unit cams, one high and one low.

Although the unit cam portion is formed in the range of 120° in FIGS. 1B to 1D, it is actually formed in the range of 90°. Accordingly, at each unit cam portion, the spread range of the base circle 8 is longer in the circumferential direction than in the illustrated state.

Hereinafter, the three cylinders will be referred to as the first, second, and third cylinders in order from the front end to the rear end of the internal combustion engine (from left to right in FIG. 1(A)). , correspondingly, the cam portion units 5a, 5b, 5c are arranged from the front end to the rear end of the internal combustion engine (from left to right in FIG. 1), the first cam portion unit 5a, the second cam portion The unit 5b and the third cam portion unit 5c are called. The explosion order of the cylinders is the order of the first cylinder, the second cylinder, and the third cylinder.

In each of the cam portion units 5a to 5c, the high unit cam portions 6a to 6c and the low unit cam portions 7a to 7c are formed on a part of the outer periphery. 6c and 7a-7c are provided. The first cam portion unit 5a, the second cam portion unit 5b, and the third cam portion unit 5c are out of phase with each other at intervals of 120° in the circumferential direction.

The first cam portion unit 5a faces downward, while the second and second cam portion units 5b and 5c face obliquely upward. In FIG. 1, for the sake of convenience, the second and second cam units are indicated by dash-dotted lines in order to clarify the relationship of the width dimensions of the unit cam portions 6a to 6c and 7a to 7c that constitute the respective cam portion units 5a to 5b. A state in which 5b and 5c are displayed downward is displayed.

A valve side member 9 such as a rocker arm or a tappet is pushed down by the unit cam portions 6a to 6c and 7a to 7c of the respective cam portion units 5a to 5c. In FIG. 1, portions of the valve-side member 9 that are in sliding contact with the unit cam portions 6a to 6c and 7a to 7c are indicated by horizontally elongated white lines for the sake of convenience (the same applies to other drawings).

Assuming that the width dimension of the valve-side member 9 in the axial direction is W, the width dimension of the high unit cam portion 6a in the first cam portion unit 5a is substantially the same as W, and the width dimension of the low unit cam portion 7a is substantially the same as W. It is set to 2W. On the other hand, in the second and third cam portion units 5b and 5c, the width dimension of the high unit cam portions 6b and 6c is approximately 2W, and the width dimension of the low unit cam portions 7b and 7c is approximately the same as W. there is
Accordingly, the width dimension of each of the motion unit cam portions 6a to 6c and 7a to 7c is an integer multiple of the width dimension W of the valve-side member 9. As shown in FIG. Further, in the first cam portion unit 5a, the width dimension W of the high unit cam portion 6a is smaller than the width dimension 2W of the low unit cam portion 7a, whereas the second cam portion unit 5b and the third cam portion unit 5c , the width dimension 2W of the high unit cam portions 6b, 6c is larger than the width dimension W of the low unit cam portions 7b, 7c.

A helical groove (guide groove) 11 is formed in the rear end portion of the outer cylinder 3. By inserting a pin 13 provided in an actuator 12 such as an electromagnetic solenoid into the helical groove 11, the outer cylinder 3 rotates. It slides in the axial direction. The spiral groove appearing in FIG. 1(A) is for sliding the outer cylinder 3 rightward, and the spiral groove 11 is formed in a range of about 120° (phase 0° to 120°) on the outer circumference. there is The spiral groove for sliding the outer cylinder 3 leftward is formed on the far side of the paper surface, and is also formed in the range of about 120° (phase 240° to 360°) on the outer circumference.

(2). First Aspect of Switching from Low Lift State to High Lift State Next, a control aspect of the first embodiment will be described. First, the first control mode will be described with reference to FIG. In the drawing, the valve-side member 9 is shown in a moved state, but this is a convenient measure for drawing, and in reality, the cam shaft 1 rotates to move the cam portion units 5a to 5c. Move (slide) sideways.

Also, in the following description, the expression that the valve-side member 9 moves is used, but this is also for convenience in order to make the description easier to understand. and the unit cam portion moves. Furthermore, although only one cam portion unit 5a to 5c is shown in FIG. 2, each pair actually exists. These are the same for the embodiments in FIG. 3 and subsequent figures.

Since this embodiment has three cylinders, base circles 8 extend at phase intervals of about 120° when viewed in the axial direction between the adjacent cam portion units 5a to 5c. In FIG. 1, the valve side member 9 is driven by the low unit cam portions 7a to 7c of the respective cam portion units 5a to 5c. That is, in FIG. 2, the low unit cam portions 7a, 7b, and 7c are driving unit cam portions.

Then, in shifting the unit cam portions for driving the valve-side member 9 from the low unit cam portions 7a to 7c to the high unit cam portions 6a to 6c, as indicated by the arrow X, the low unit in the first cam portion unit 5a. The state in which the apex of the cam portion 6a is in contact with the valve-side member 9 is defined as the starting point (phase angle 0°=360°) of the start of sliding of the outer cylinder 3, and the outer cylinder 3 starts to move rightward from this state. rotates 120 degrees, each cam unit 5a, 5b, 5c is moved by 2W, so that the driving unit cams of each cam unit 5a, 5b, 5c move to the lower unit cams 7a, 7b, 7c to the high unit cam portions 6a, 6b and 6c.

When the outer cylinder 3 slides leftward, the spiral groove 11 is formed in a range of about 120° (phase 0° to 120°) on the outer circumference, so that the outer cylinder 3 rotates about 60° in the first cam unit 5a. Then, the valve-side member 9 moves by a distance of 1/2 of the total sliding distance (the distance (2W) required for the left end of the valve-side member 9 to reach the left end of the high unit cam portion 6a). The sliding contact surface of the partial unit 5a completely transitions to the base circle 8.

In the first cam portion unit 5a, the lateral width of the low unit cam portion 7a is 2W , which is approximately twice the width of the high unit cam portion 7a. remains in contact with the low unit cam portion 6a, and the valve-side member 9 does not interfere with the high unit cam portion 6a.

That is, in the first cam portion unit 5a, the valve-side member 9 is in sliding contact with the low unit cam portion 7a within a range of about 60° after the start of lateral movement of the outer cylinder 3. The valve-side member 9 moves relatively toward the boundary line 14a with the high unit cam portion 6a. 8 has been reached.

Therefore, the valve-side member 9 does not collide with (interfere with) the high unit cam portion 6a, and the transition from the unit cam portion 7a to the high unit cam portion 6a is performed smoothly. Conversely, in the range where the outer cylinder 3 rotates by about 60°, the valve-side member 9 does not move from the low unit cam portion 7a to the high unit cam portion 6a beyond the boundary line 14a . The relationship between the width dimension W1 of the unit cam portion 7a and the width dimension W of the valve-side member 9 is set.

The phase of the second cam portion unit 5b is delayed by 120° with respect to the cam profile of the first cam portion unit 5a. Therefore, when the cam portion unit 5b starts to move, the valve side member 9 is in sliding contact with the base circle 8, and when the outer cylinder 3 rotates about 60°, the distance of 1/2 of the total sliding distance (valve side member 9), the valve-side member 9 has already passed the boundary line 14b between the low unit cam portion 7b and the high unit cam portion 6b.

That is, in the second cam portion unit 5b, while the low unit cam portion 7b is in sliding contact with the base circle 8, the valve-side member 9 crosses the boundary line 14b and shifts to the high unit cam portion 6b. Therefore, the valve-side member 9 does not collide with the high unit cam portion 6b. After the remaining 60° rotation and movement by W, the valve-side member 9 slides on the high unit cam portion 6b and is positioned at the left end of the high unit cam portion 6b to complete the sliding.

The phase of the third cam portion unit 5c is delayed by 240° with respect to the cam profile of the first cam portion unit 5a. Therefore, the valve-side member 9 is in sliding contact with the base circle 8 for about 180° after the outer cylinder 3 starts moving, and while the outer cylinder 3 rotates about 120°, The valve-side member 9 passes through the boundary line 14c while sliding on the base circle 8, and has finished moving to a portion where it can slide on the high unit cam portion 6c. Therefore, the valve-side member 9 does not collide with the high unit cam portion 6c, and switching from the low unit cam portion 7c to the high unit cam portion 6c is performed smoothly. The width of the entire third cam portion unit 5c should be 3W.

(3). First mode of switching from high-lift state to low-lift state The switching mode from the high-lift state to the low-lift state is performed by the procedure indicated by the arrow Y in FIG. That is, with the state where the valve-side member 9 is in contact with the vertex of the high unit cam portion 6c at the third cam portion unit 5c as the slide starting point, the rightward slide is completed while the outer cylinder 3 rotates 120 degrees. ing.

In this case, at the location of the third cam portion unit 5c, the valve-side member 9 moves by 1/2 of the total slide amount (=2W), that is, by W (the width dimension of the valve-side member 9 in the axial direction). In the range of about 60° after the start of lateral movement of the cylinder 3, the valve-side member 9 slides on the high unit cam portion 6c, and the outer cylinder 3 rotates more than 60°, causing the valve-side member 9 to move. exceeds the boundary line 14c, the valve-side member 9 reaches the base circle 8. As shown in FIG. Therefore, the valve-side member 9 is smoothly switched from the high unit cam portion 6c to the low unit cam portion 7c without falling from the high unit cam portion 6c to the low unit cam portion 7c.

In the first cam portion unit 5a, the valve-side member 9 is in sliding contact with the base circle 8 at the start of sliding. The width of the high unit cam portion 6a in the axial direction is W, but when the outer cylinder 3 is rotated by 60°, the valve-side member 9 moves toward the boundary line between the high unit cam portion 6a and the low unit cam portion 7a. 14a, and when it shifts to sliding contact with the low unit cam portion 7a and rotates 60°, the valve side member 9 shifts from left to right on the low unit cam portion 7a, and from the start of rotation, After passing 120 degrees, the valve-side member 9 reaches the right end of the low unit cam portion 7a and the slide ends. Therefore, even at the location of the first cam portion unit 5a, the switching can be performed smoothly without incurring a problem such as the valve side member 9 falling into the low unit cam portion 7a.

At the second cam portion unit 5b, the valve-side member 9 is in sliding contact with the base circle 8 from the start to the end of the movement of the outer cylinder 3, and the valve-side member 9 is in sliding contact with the base circle 8. In this state, it passes through the boundary line 14b between the high unit cam portion 6b and the low unit cam portion 7b. Therefore, the switching from the high unit cam portion 6b to the low unit cam portion 7b is smoothly performed.

(4). Second Mode of Switching FIG. 3 shows the second mode of switching in the first embodiment. In the first mode, switching is completed while the outer cylinder 3 rotates 120°, but in this second mode, while the outer cylinder 3 rotates 240°, the cam portion units 5a, 5b, and 5c move. set to terminate.

First, switching from the low unit cam portions 7a, 7b, 7c to the high unit cam portions 6a, 6b, 6c will be described. In this second aspect, the rotation of the outer cylinder 3 is started from a state in which the cam portions 6b and 7b of the second cam portion unit 5b are directed upward.

At the start of rotation of the outer cylinder 3, in the first cam portion unit 5a, the unit cam portions 6a and 7a are directed obliquely downward, the valve-side member 9 is in contact with the base circle 8, and the outer cylinder 3 is 120°. During the rotation, the valve-side member 9 laterally moves a distance W while slidingly contacting the low unit cam portion 7a.

On the other hand, when the outer cylinder 3 rotates 120°, the valve-side member 9 reaches the boundary line 14a between the low unit cam portion 7a and the high unit cam portion 6a. At the stage when the outer cylinder 3 has rotated by 120°, the valve-side member 9 has come off the low unit cam portion 7a and has completely moved to the base circle 8 . Therefore, the valve-side member 9 does not collide with the high unit cam portion 6a, and switching from the low unit cam portion 7a to the high unit cam portion 6a is performed smoothly.

At the location of the second cam portion unit 5b, as described above, when the outer cylinder 3 starts rotating, the unit cam portions 6b and 7b face straight up, and the valve-side member 9 abuts the base circle 8. in contact with Therefore, the valve-side member 9 moves laterally while sliding on the base circle 8 as the outer cylinder 3 rotates. and the low unit cam portion 7b, and after the outer cylinder 3 rotates 120°, the valve-side member 9 moves to the high unit cam portion 6a via the base circle 8, It laterally moves to the left while making sliding contact with the high unit cam portion 6b.

When the 240° rotation of the outer cylinder 3 is completed, the outer cylinder 3 is positioned at the left end of the high unit cam portion 6b. Therefore, switching from the low unit cam portion 7b to the high unit cam portion 6b in the second cam portion unit 5b is performed smoothly.

At the position of the third cam portion unit 5c, when the outer cylinder 3 starts to rotate, the valve-side member 9 has come off the lower unit cam portion 7c. The valve-side member 9 remains in sliding contact with the base circle 8 all the time, and the valve-side member 9 passes through the boundary line 14c between the low unit cam portion 7c and the high unit cam portion 6c while slidingly contacting the base circle 8. .

The valve-side member 9 is positioned at the left end of the base circle 8 even when the outer cylinder 3 is rotated by 240°. Accordingly, switching from the low unit cam portion 7c to the high unit cam portion 6c is smoothly performed even at the location of the third cam portion unit 5c.

Switching from the high unit cam portions 6a, 6b, 6c to the low unit cam portions 7a, 7b, 7c is performed starting from a state in which the unit cam portions 6a, 7a in the first cam portion unit 5a are directed directly upward.

When the outer cylinder 3 rotates 120° in switching from the high unit cam portion 6a to the low unit cam portion 7a, in the first cam portion unit 5a, the outer cylinder 3 passes the boundary line 14a between the high and low unit cam portions 6a and 7a. However, in the first cam unit 5a, the valve-side member 9 is kept in sliding contact with the base circle 8 within a range of 120° after the outer cylinder 3 starts rotating. , passes through the boundary line 14a while being in sliding contact with the base circle 8. As shown in FIG. Therefore, switching from the high unit cam portion 6a to the low unit cam portion 7a is performed smoothly.

At the second cam portion unit 5b, when the outer cylinder 3 starts rotating, the outer cylinder 3 has just left the high unit cam portion 6b and has just moved to the base circle 8. During the 240° rotation, the outer cylinder 3 laterally moves while sliding on the base circle 8 . Therefore, the valve-side member 9 passes through the boundary line 14b between the elevation unit cam portions 6b and 7b while sliding on the base circle 8. As shown in FIG. Accordingly, switching from the high unit cam portion 6b to the low unit cam portion 7b can be performed smoothly without any trouble even at the location of the second cam portion unit 5b.

At the third cam portion unit 5c, the valve-side member 9 is in contact with the base circle 8 when the outer cylinder 3 starts rotating. It moves laterally while sliding on the portion 6c. Then, when the outer cylinder 3 rotates 120°, the valve-side member 9 leaves the high unit cam portion 6c, shifts to the base circle 8, and then passes through the boundary line 14c between the high and low unit cam portions 6c and 7c. Therefore, switching from the high unit cam portion 6c to the low unit cam portion 7c can be performed smoothly without any trouble even at the location of the third cam portion unit 5c.

In the second mode, switching is performed while the outer cylinder 3 rotates 240°, so the movement distance of the valve-side member 9 per unit rotation angle of the outer cylinder 3 is smaller than in the first mode. Therefore, the sliding between the valve-side member 9 and the cam portion units 5a, 5b, 5c can be smoothed. The guide grooves 11 shown in FIG. 1 are for switching from the low unit cam portions 7a, 7b, and 7c to the high unit cam portions 6a, 6b, and 6c, and for switching from the high unit cam portions 6a, 6b, and 6c to the low unit cam portions. Since the two guide grooves 11 are formed so as to be shifted in the axial direction from those for switching to the unit cam portions 7a, 7b, and 7c, the flexibility of the formation positions of the two guide grooves 11 is improved.

In the first embodiment, the overall width of the cam units 5a, 5b, 5c is set to 3W, and the movement stroke of the outer cylinder 3 is set to 2W. By setting the dimension to 3W, the movement stroke of the outer cylinder 3 may be set to 3W.

(5). Second Embodiment A second embodiment shown in FIG. 4 is applied to a valve gear that can switch the valve lift amount in three stages of high, medium, and low in a three-cylinder internal combustion engine. Therefore, in this embodiment, intermediate unit cam portions 15a-15c exist between the high unit cam portions 6a-6c and the low unit cam portions 7a-7c.

In this embodiment, when the lateral width of the valve-side member 9 is W, first, in the first cam portion unit 5a, the high unit cam portion 6a has a width dimension of approximately 2W, and the middle unit cam portion 15a has a width dimension of W and the width of the low unit cam portion 7a are assumed to be approximately 2W. At the second cam portion unit 5b, the high unit cam portion 6a has a width dimension of W, the middle unit cam portion 15a has a width dimension of 3W, and the low unit cam portion 6a has a width dimension of W. Further, in the third cam portion unit 5c, the width of the high unit cam portion 6a and the low unit cam portion 7c is 2W, and the width of the middle unit cam portion 15c is W.

In this embodiment, the transition from the low unit cam portions 7a to 7c to the middle unit cam portions 15a to 15c is started when the valve side member 9 in the first cam portion unit 5a is in contact with the apex of the low unit cam portion 6a. , the outer cylinder 3 is rotated by 120 degrees. Since the total width of each cam unit 5a, 5b, 5c is 5W, the movement stroke of the valve-side member 9 is 4W.

(6). Switching of Increase in Lift Amount in Second Embodiment In this embodiment, the outer cylinder 3 moves by a distance W when rotated by 60°. Switching from the low unit cam portions 7a, 7b, 7c to the middle unit cam portions 15a to 15c starts from the posture in which the high and low unit cam portions 6a, 7a are directed downward in the first cam portion unit 5a. , the outer cylinder 3 is rotated by 120°.

Switching from the middle unit cam portions 15a to 15c to the high unit cam portions 6a, 6b, and 6c starts from the posture in which the high and low unit cam portions 6b and 7b are facing directly downward in the second cam portion unit 5b. This is done within a range where the cylinder 3 rotates 120°. The switching from the low unit cam portions 7a, 7b, 7c to the high unit cam portions 6a, 6b, 6c is a combination of both, and the high/low unit cam portions 6a, 7a are directed downward in the first cam portion unit 5a. This is performed within a range in which the outer cylinder 3 rotates 240° from the starting position.

In switching from the low unit cam portions 7a, 7b, 7c to the middle unit cam portions 15a to 15c, in the first cam unit 5a, the low unit cam portion 7a has a width of 2W, so the outer cylinder 3 rotates 60°. Then, the valve-side member 9 shifts to the left end of the low unit cam portion 7a, but at this stage the valve-side member 9 shifts to the base circle 8. As shown in FIG. Therefore, the valve-side member 9 passes through the boundary line 14a between the low and middle unit cam portions 7a and 15a on the base circle 8. As shown in FIG. Therefore, switching from the low unit cam portion 7a to the middle unit cam portion 15a is smoothly performed without any trouble.

Further, when shifting from the middle unit cam portion 15a to the high unit cam portion 6a, the valve side member 9 is in sliding contact with the base circle 8, but during the 120° The state of sliding contact with the circle 8 is maintained. Therefore, the valve-side member 9 passes through the boundary line 16a between the middle unit cam portion 15a and the high unit cam portion 6a while being in sliding contact with the base circle 8. As shown in FIG. Therefore, switching from the middle unit cam portion 15a to the high unit cam portion 6a is smoothly performed without any trouble.

At the second cam portion unit 5b, switching from the low unit cam portion 7b to the middle unit cam portion 15b starts from the state where the valve-side member 9 is in contact with the base circle 8. As shown in FIG. When the valve-side member 9 moves by W, the valve-side member 9 completely passes through the boundary line 14b between the low and middle unit cam portions 7b and 15b. Because of the movement, switching from the low unit cam portion 7b to the middle unit cam portion 15b is performed smoothly.

In the second cam portion unit 5b, switching from the middle unit cam portion 15b to the high unit cam portion 6b starts from the state where the valve-side member 9 is in contact with the intermediate portion of the middle unit cam portion 15b. The cam portion 15b has a width of 3W, and the valve-side member 9 is in sliding contact with the base circle 8 within the range in which the outer cylinder 3 rotates by 120°. , the boundary line 16b of the middle/high unit cam portions 15b and 6b. Therefore, also in the second cam portion unit 5b, switching from the middle unit cam portion 15b to the high unit cam portion 6b is smoothly performed.

At the third cam portion unit 5c, switching from the low unit cam portion 7c to the middle unit cam portion 15c starts from the state where the valve-side member 9 is in contact with the base circle 8. The valve-side member 9 is kept in sliding contact with the base circle 8 within the range of rotation. Therefore, the valve-side member 9 passes through the boundary line 14c between the low and middle unit cam portions 7c and 15c while sliding on the base circle 8. As shown in FIG. Therefore, switching from the low unit cam portion 7c to the middle unit cam portion 15c is smoothly performed.

In the third cam portion unit 5c, switching from the middle unit cam portion 15c to the high unit cam portion 6c starts from a state in which the valve-side member 9 is in contact with the base circle 8. , while the valve-side member 9 is kept in sliding contact with the base circle 8, the intermediate unit cam portion 15c has a width of W, and the valve-side member 9 is rotated by 60° while the outer cylinder 3 is rotated by 60°. Since it passes through the middle unit cam portion 15c, the valve-side member 9 passes through the boundary line 16c between the middle and high unit cam portions 15c and 6c while making sliding contact with the base circle 8. As shown in FIG.

Therefore, also in the third cam portion unit 5c, switching from the low unit cam portion 7c to the middle unit cam portion 15c and switching from the middle unit cam portion 15c to the high unit cam portion 6c are performed smoothly.

(7). Switching to Decrease Lift Amount in Second Embodiment In the second embodiment, an example of switching control for decreasing the lift amount is shown in FIG. Switching from the high unit cam portions 6a, 6b, and 6c to the middle unit cam portions 15a to 15c, and from the middle unit cam portions 15a to 15c to the low unit cam portions 7a and 7b, in contrast to the switching control for increasing the lift amount. , 7c is performed by rotating the outer cylinder 3 by 120°, and the switching from the high unit cam portions 6a, 6b, 6c to the low unit cam portions 7a, 7b, 7c is performed by combining the two. , while rotating the outer cylinder 3 by 240°.

Switching from the high unit cam portions 6a, 6b, 6c to the middle unit cam portions 15a to 15c is performed starting from a state in which the unit cam portions 6a, 15a, 7a in the first cam portion unit 5a are directed downward.

In the first cam portion unit 5a, the valve side member 9 is separated from the high unit cam portion 6a after 120° has passed since the start of rotation. ing. Therefore, the valve-side member 9 passes through the boundary line 16a between the high and middle unit cam portions 6a and 15a on the base circle 8. As shown in FIG. Therefore, switching from the high unit cam portion 6a to the medium unit cam portion 15a is smoothly performed.

In the first cam portion unit 5a, the valve-side member 9 is in sliding contact with the base circle 8 while switching from the middle unit cam portion 15a to the low unit cam portion 7a is being performed. Therefore, the valve-side member 9 passes through the boundary line 14a between the middle-low unit cam portions 15a and 7a while being in sliding contact with the base circle 8. As shown in FIG. Therefore, it is possible to smoothly switch from the middle unit cam portion 15a to the low unit cam portion 7a.

In the second cam portion unit 5b, when the outer cylinder 3 starts rotating, the valve-side member 9 is in contact with the base circle 8, and within the range of 60° rotation, the valve-side member 9 is in sliding contact with the base circle 8. maintained. When rotated by 60°, the valve-side member 9 shifts to the middle unit cam portion 15b. Therefore, when the valve-side member 9 is in sliding contact with the base circle 8, the valve-side member 9 passes through the boundary line 16b between the high and middle unit cam portions 6b and 15b.

The transition from the middle unit cam portion 15b to the low unit cam portion 7c is performed within a range of 120°, and the valve-side member 9 is kept in sliding contact with the base circle 8 within this range. Therefore, also in the second cam portion unit 5b, switching from the high unit cam portion 6b to the middle unit cam portion 15b and switching from the middle unit cam portion 15b to the low unit cam portion 7b are performed smoothly.

The same applies to the third cam portion unit 5c. As can be clearly understood from the drawing, when the valve-side member 9 shifts from the high unit cam portion 6c to the middle unit cam portion 15c, the valve-side member 9 While in sliding contact with the circle 8, it passes through the boundary line 14c between the high, middle, and low unit cam portions 15b and 7c. Further, when the middle unit cam portion 15c shifts to the low unit cam portion 7c, the valve side member 9 is in sliding contact with the base circle 8 while the outer cylinder 3 rotates by 60°. , slides on the base circle 8 and passes through the boundary line 14c between the middle-low unit cam portions 15c and 7c.

(8). Third Embodiment The sixth and seventh embodiments show a third embodiment applied to a four-cylinder internal combustion engine. In this embodiment, first to fourth cam portion units 5a to 5d are provided corresponding to the first to fourth cylinders, and the first cam portion units 5a to 5d are sequentially out of phase by 90 degrees. ing. The phases of the first cam unit 5a and the second cam unit 5b are out of phase by 90°, and the phases of the second cam unit 5b and the third cam unit 5c are out of phase by 180°. The third cam unit 5c and the fourth cam unit 5d are out of phase by 270° (-90°), and the fourth cam unit 5d and the first cam unit 5a are out of phase by 180°. .

Based on the width W of the valve-side member 9, in the first and second cam unit units 5a and 5b, the high unit cam portions 6a and 6b are 3W, and the low unit cam portions 7a and 7b are 2W. In the third and fourth cam portion units 5c and 5d, the high unit cam portions 6c and 6d are W and the low unit cam portions 7c and 7d are 4W. Therefore, the outer cylinder 3 moves by a dimension of 4W.

In this embodiment, the switching from the low unit cam portions 7a to 7d to the high unit cam portions 6a to 6d is performed starting from the posture in which the unit cam portions 6a and 7a are directed directly downward in the first cam portion unit 5a. This is done by rotating the outer cylinder 3 by 360°.

In the first cam portion unit 5a, the valve-side member 9 shifts to the base circle 8 when the outer cylinder 3 rotates 90 degrees. In the third cam portion unit 5a, the valve-side member 9 slides on the base circle 8 in the range from the start of transition to 90 degrees, and after passing 90 degrees, the high unit cam passes through the low unit cam portion 7c. Go to part 6a. In the second and fourth cam portion units 5b and 5d, the valve-side member 9 contacts the base circle 8 from the start to the end of movement. Therefore, in any of the cam portion units 5a to 5d, the valve-side member 9 passes through the boundary lines 14a to 14d while making sliding contact with the base circle 8. As shown in FIG.

The transition from the high unit cam portions 6a to 6d to the low unit cam portions 7a to 7d is performed by the movement of the valve side member 9 in the first cam portion unit 5a, as shown in FIG. Starting from a state in which the unit cam portions 6c and 7c of the third cam portion unit 5c are in an upward posture, the rotation range is 360°.

In the first cam portion unit 5a, the valve-side member 9 starts in contact with the base circle 8, passes through the high unit cam portion 6a, moves to the base circle 8, and then moves to the low unit cam portion 7a. do. Then, the valve-side member 9 slides on the base circle 8 and passes through the boundary line 14a between the elevation unit cam portions 6a and 7a.

In the second cam portion unit 5b, the valve-side member 9 starts from the high unit cam portion 6b, passes through the base circle 8, and transitions to the low unit cam portion 7b. Then, the valve-side member 9 slides on the base circle 8 and passes through the boundary line 14b between the elevation unit cam portions 6b and 7b.

In the third and cam portion units 5c and 5d, the valve-side member 9 starts from the base circle 8, and while sliding on the base circle 8, the valve-side member 9 moves along the boundary lines 14c and 14d of the elevation unit cam portions 6b and 7b. After passing through, it shifts to the low unit cam portions 7c and 7d.

(9).Others Above, examples of application to 3-cylinder and in-line 4-cylinder internal combustion engines were explained, but the present invention can also be applied to other multi-cylinder internal combustion engines such as in-line 6-cylinder internal combustion engines and V-type 6-cylinder internal combustion engines. Applicable. The sliding means for the outer cylinder is not limited to the combination of a guide groove (cam groove) and a pin as in the embodiment, and a mechanism similar to a gear shifter can also be employed.

The setting of the width dimension of each unit cam portion can be appropriately changed according to the width dimension of the valve-side member, the movement distance of the outer cylinder per predetermined rotation angle of the camshaft, and the number of cylinders. Also, even if a VVT device that varies the cam phase is mounted on the front end of the camshaft, the rotation phase of the cam with respect to the rotation of the crank is only shifted integrally with the helical groove. It is established as it is by changing

The present invention can be embodied in a valve train for a multi-cylinder internal combustion engine. Therefore, it can be used industrially.

1 cam shaft 2 core shaft 3 outer cylinder 4 bearing portion 5a, 5b, 5c, 7d cam portion unit 6a, 6b, 6c, 6d high unit cam portion 7a, 7b, 7c, 7d low unit cam portion 8 base circle 9 valve side member (e.g. rocker arm)
11 Spiral groove constituting slide means 12 Actuator 13 Pins 14a to 14d, 16a to 16d Boundary lines between unit cam portions 15a to 15d Middle unit cam portion

Claims (1)

On the camshaft, which rotates in conjunction with the crankshaft, the cam unit consists of unit cams with different projection heights from the base circle at multiple locations corresponding to each of the multiple cylinders. placed staggered,
When each cam unit moves axially by a predetermined distance while the cam shaft rotates by a predetermined angle, the drive unit cam portion that is in sliding contact with the rocker arm and other valve-side members is switched to increase the lift amount of the valve. is intended to be changed,
In addition, each of the cam portion units is simultaneously moved in the axial direction by the predetermined distance to sequentially switch the drive unit cam portions in each cam portion unit,
The axial width dimension of each unit cam portion in each cam portion unit is set to be an integral multiple of the axial width dimension of the valve-side member, and the width dimension of the tall unit cam portion A cam portion unit with a width dimension larger than that of a unit cam portion with a lower height and a cam portion unit with a width dimension of a unit cam portion with a higher height smaller than that of a unit cam portion with a lower height coexist. and
When each of the cam portion units simultaneously moves by an integral multiple of the width dimension of the valve side member, the valve side member is set so as to always pass on the base circle on the boundary line between adjacent unit cam portions. has been
A variable valve lift system for a multi-cylinder internal combustion engine.

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