JPH037525Y2 - - Google Patents

Description

[Detailed explanation of the idea]

<Industrial field of application> The present invention is a method for applying two or more valves that are installed at the intake or exhaust ports of each combustion chamber of an internal combustion engine and are driven to open by a cam that rotates in synchronization with the crankshaft via a plurality of cam followers. Regarding a valve train having a valve,
In particular, the present invention relates to a valve mechanism whose operating state can be changed depending on the rotational speed. <Prior Art> The intake of air-fuel mixture and the discharge of combustion gas into the combustion chamber of an internal combustion engine are performed by the operation of the above-mentioned valve mechanism, and the operation timing of these valves is as follows:
It is set to be optimal according to the rotation angle of the crankshaft, that is, the stroke of the piston. Incidentally, in order to reduce the suction resistance of the air-fuel mixture, it is desirable that the valve opening degree be increased to some extent. On the other hand, in order to make the concentration distribution of the air-fuel mixture in the combustion chamber uniform, it is preferable to make the air-fuel mixture flowing into the combustion chamber turbulent, and for this purpose, it is preferable to make the operating states of adjacent valves different from each other. However, in order to do this, a plurality of cams having different cam profiles and cam followers for transmitting the lift of the cams to the corresponding valves are required for the same number of valves. However, when trying to obtain the necessary opening degree with a single valve, the valve becomes larger and its inertial mass increases, which causes disadvantages such as deterioration of valve followability. Therefore, in order to obtain as large an opening area as possible within a limited cylinder bore, it is preferable to operate a large number of valves in parallel to reduce the size and weight of each valve. On the other hand, when the engine is operating at a low speed, the piston speed is low and the air-fuel mixture flow rate is small. Therefore, if the opening area of the intake port is too large, the intake air flow speed decreases, causing a disadvantage that the air-fuel mixture filling efficiency deteriorates. In order to correct such inconvenience, the applicant
We propose a valve operating mechanism that selectively changes the valve operating timing according to the cam profile of either the high-speed cam or the low-speed cam by switching between connection and disconnection between the three rocker arms. (Refer to Japanese Unexamined Patent Publication No. 1989-19911). <Problems to be solved by the invention> However, when the number of valves is increased, and the number of cam followers such as rocker arms is increased accordingly, the valve mechanism becomes larger and problems arise in assembly. In view of these problems in the prior art, the main purpose of the present invention is to improve mixing over a wide rotational speed range in internal combustion engines that have two or more valves per cylinder at the intake or exhaust ports. It is an object of the present invention to provide a valve operating mechanism in which a valve operation state switching device for improving gas filling efficiency or combustion gas discharge efficiency can be constructed in a relatively compact manner. <Means for solving the problem> According to the present invention, this purpose is achieved by using a camshaft installed at the intake or exhaust port of each combustion chamber of an internal combustion engine, which rotates synchronously with the crankshaft. A plurality of two or more valves that are driven to open by a plurality of cams having different contours and a plurality of cam followers corresponding to the plurality of cams, and connection and non-coupling between mutually adjacent ones of the plurality of cam followers. In the valve train having a switching means for selecting, at least some of the plurality of cam followers have a plurality of valve contact portions provided at positions having different lever ratios, and the valve contact portion This is achieved by providing a valve operating mechanism for an internal combustion engine, which is characterized in that the valves in contact with each of the valves are simultaneously driven. <Operation> In this way, the operating state of two or more valves can be variable-driven without increasing the number of cam followers more than necessary. A single cam profile can drive a plurality of valves to open with mutually different valve lift amounts. <Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the internal combustion engine main body (not shown) has three intake valves 1a to 1 for each cylinder.
1c is provided on a predetermined circumference centered on a spark plug (not shown), and these intake valves 1a to
1c is provided integrally with a camshaft 2 that is synchronously driven at half the speed of a crankshaft (not shown).
The opening/closing operation is performed by the first to third cams 3 to 5, each having a different cam profile, and the first to third rocker arms 6 to 8, which act as cam followers and engage with these cams 3 to 5 to perform rocking motion. They are supposed to do it. Further, this internal combustion engine is equipped with a pair of exhaust valves (not shown), which are driven to open and close in correspondence with the above-mentioned intake valves 1a to 1c. The first to third rocker arms 6 to 8 are pivoted adjacent to each other so as to be able to swing freely on a rocker shaft 9 fixed below the camshaft 2 in parallel to the camshaft 2. is pivotally supported at its base by the rocker shaft 9, and its free end extends toward each of the intake valves 1a to 1c. Second
The rocker arm 7 is formed with two arms 10a, 10b that abut the upper ends of the two intake valves 1a, 1b, and the third rocker arm 8 is formed with an arm 10c that abuts the upper end of the remaining intake valve 1c. has been done. A tappet screw 11 is attached to the end of each of the arms 10a to 10c in contact with each intake valve 1a to 1c.
a to 11c are screwed together so that they can move forward and backward, and the tappet screws are connected to lock nuts 12a.
~12c prevents it from loosening. The free end of the first rocker arm 6 slightly extends from the rocker shaft 9 in the same direction as the second and third rocker arms 7, 8, and as clearly shown in FIG. The first cam 3 is on the top surface.
A cam slipper 6a is formed which slides in contact with the cam slipper 6a, and the upper end surface of a lifter 15 which slides into a guide hole 14 formed in the cylinder head 13 is in contact with the lower surface of the end of the cam slipper 6a. The inner surface of this lifter 15 and the guide hole 14
A coil spring 16 is compressed between the bottom surface and the bottom surface. As a result, the lifter 15 is always urged upward, and the cam slipper 6a of the first rocker arm 6 is always in sliding contact with the first cam 3. As described above, the camshaft 2 is rotatably supported above the engine body, and includes a first cam 3 corresponding to the first rocker arm 6, a second cam 4 corresponding to the second rocker arm 7, and a second cam 4 corresponding to the second rocker arm 7. A third cam 5 corresponding to the third rocker arm 8 is integrally connected. As clearly shown in Figure 3, these cams all have the same base circle C,
The first cam 3 has a large lift over a relatively wide angular range, and is formed into a cam profile suitable for the high-speed operating range of the engine.
Its outer peripheral surface can be slidably contacted with a cam slipper 6a formed on the upper surface of the cam slipper 6a. 2nd cam 4
is formed in a cam profile suitable for the medium speed operating range of the engine, which has a narrower angular range and a somewhat smaller lift than the first cam 3, and is slid onto the cam slipper 7a of the second rocker arm 7. are in contact with each other.
The third cam 5 is formed into a cam profile suitable for the low-speed operating range of the engine with a narrower angle range and smaller lift, and is in sliding contact with the cam slipper 8a of the third rocker arm 8. The first to third cams that engage with these first to third cams 3 to 5
The third rocker arms 6 to 8 are each rocker arm 6 to
The first and second shafts (to be described later) are installed in holes drilled through the center of the shaft 8 and parallel to the shaft 9.
The connecting devices 17 and 18 enable switching between a state in which adjacent parts can swing integrally and a state in which they can be relatively displaced. On the other hand, the valve stems of these intake valves 1a to 1c extend parallel to each other, and therefore the arm 10b that abuts the central intake valve 1b is short in size and abuts the intake valves 1a and 1c on both sides. Arm 1
The dimensions of 0a and 10c are made equal. That is,
The two intake valves 1a and 1b driven by the second rocker arm 7 are connected to the arm 1 with different lever ratios.
0a and 10b will be driven simultaneously. Further, a retainer 19 is provided above each of the intake valves 1a to 1c, and a retainer 19 is provided between each of the intake valves 1a to 1c between the retainer 19 and the engine body.
A valve spring 20 is interposed to surround the stem portion of the intake valves 1a to 1c.
That is, it is biased upward in FIG. As clearly shown in FIG. 4, a first coupling device 17 is provided between the first and second rocker arms 6, 7.
A second coupling device 18 is provided between the second and third rocker arms 7 and 8, respectively. These first and second coupling devices 17 and 18 are substantially the same in structure and operating procedure, and only the first coupling device 17 will be described below. The first locking arm 6 has a second locking arm 7.
A first guide hole 21 that opens toward the side is bored parallel to the rocker shaft 9. and,
The second rocker arm 7 is provided with a second guide hole 22 that is concentric and has the same diameter as the first guide hole 21 of the first rocker arm 6 and opens toward the first rocker arm 6 side. A reduced diameter portion 23 is formed at the bottom side of the second guide hole 22, and a stepped portion 24 is formed accordingly. Inside the second guide hole 22, the first and second guide holes 21, 2 are located between the position where the first and second rocker arms 6, 7 are connected and the position where the connection is released.
A piston 25 that can move astride the first guide hole 21 is provided with a stopper 26 that defines the plunge distance of the piston 25 into the first guide hole 21. The axial dimension of the piston 25 is set such that when one end thereof contacts the stepped portion 24 in the second guide hole 22, the other end does not protrude into the first guide hole 21. A hydraulic chamber 27 is defined between the end surface of the piston 25 and the small diameter portion 23. Moreover, the inner surface of the stopper 26 and the first guide hole 21
A coil spring 28 is compressed between the piston 26 and the bottom surface of the piston 25, and constantly presses the stopper 26 toward the piston 25. A hydraulic oil supply passage 29 is bored in the rocker shaft 9 and communicates with a hydraulic pressure supply device to be described later.
The hydraulic oil supplied from the hydraulic oil supply passage 29 can be introduced into the hydraulic chamber 27 through the communication hole 31 bored in the peripheral wall of the hydraulic oil supply passage 29 regardless of the swinging state of the second rocker arm 7. It's like that. That is, the piston 25 is displaced by the hydraulic pressure of the hydraulic oil against the biasing force of the coil spring 28, thereby connecting the adjacent rocker arms to each other. Furthermore, the first and second coupling devices 17 and 18 are arranged symmetrically around the hydraulic chamber 27, and it is possible to apply hydraulic pressure to both the first and second coupling devices 17 and 18 at the same time. It is done like this. In both the first and second coupling devices 17 and 18, the spring constants of the coil springs 28 that bias the stopper 26 are set to different values, and the first coupling device 17 is connected to the second coupling device 18. In contrast, it is designed to operate with low oil pressure. FIG. 5 schematically shows the hydraulic pressure supply path for the above embodiment. For example, the oil discharged from the lubricating oil pump 40 connected to the crankshaft of the engine is regulated to a predetermined pressure by a pressure regulating device 41. rear,
It is connected to the hydraulic oil supply passage 29 via a 3-port 2-position first solenoid valve 42 . The pressure regulator 41 includes a relief passage 46 that releases the pressure of the discharge passage 45 into the oil tank via the relief valve 44, and an orifice 47 that adds the pressure of the discharge passage 45 to the spring biasing force of the relief valve 44. The set pressure of the relief valve 44 can be changed in two stages by intermittent the back pressure applied to the back pressure passage 48 by a second electromagnetic valve 49. has been done. A first solenoid valve 42 that connects and disconnects the hydraulic oil supply passage 29
Normally, the input port is closed and the output port and tank port communicate with each other, and the input port and output port communicate with each other during excitation, and the hydraulic pressure is applied to each coupling device 17 and 18 only during excitation. It is designed to supply Next, the operating procedure of the apparatus described above will be explained. When the first electromagnetic valve 42 is in a demagnetized state, hydraulic pressure is not supplied to the hydraulic oil supply passage 29, and therefore, the first and second coupling devices 17 and 18 are operated by the biasing force of the coil spring 28 of the stopper 26, respectively. , is in the disconnection position side, and all the rocker arms are in a state where they can swing independently. In this state, the swinging motion of the first rocker arm 6 by the first cam 3 has no effect on each of the intake valves 1a to 1c, and the two intake valves 1a and 1b are
The intake valves 1c are driven to open via the rocker arm 7 according to the cam profile of the second cam 4, and the remaining intake valves 1c are driven to open via the third rocker arm 8 according to the cam profile of the third cam 5. Next, the second solenoid valve 49 is opened, the back pressure acting on the relief valve 44 is released, the circuit pressure is set to low pressure, and the first solenoid valve 42 is excited.
Low pressure hydraulic pressure acts on both the first and second coupling devices 17 and 18 via the hydraulic oil supply passage 29. By the way, since the operating pressure of the second coupling device 18 is set to a high pressure, only the first coupling device 17, which is set to a low pressure, is displaced to the coupling position side as shown in FIG. and 2nd Rotsuka Arm 7
Connect with. Therefore, both the first and second rocker arms 6, 7 respond to the cam profile of the first cam 3 which has a higher lift than the second cam 4, and the valve lift and valve opening angle of the two intake valves 1a, 1b are adjusted accordingly. The opening/closing drive is changed from the state described above. When the second solenoid valve 49 is closed, back pressure acts on the relief valve 44 and the circuit pressure is set to high pressure. When the first solenoid valve 42 is excited here, both the first and second coupling devices 17 and 18 are operated to the coupling position side,
The first to third rocker arms 6 to 8 are all integrally connected. In this state, since the lift of the first cam 3 is the highest, all the intake valves 1a to 1c are driven to open in response to the cam profile of the first cam 3. Each of the above-mentioned coupling devices 12, 13 and each intake valve 1a
Table 1 summarizes the operational relationship with ~1c.

[Table] By adopting the above configuration, it is possible to selectively change the three types of states as shown in Table 1, and the intake valve or exhaust valve is selected according to the rotational speed of the engine. It becomes possible to control the In the above embodiment, the valve stems of the intake valves arranged on a certain circumference extend parallel to each other, and the lever ratios of the arms 10a and 10b corresponding to the two intake valves 1a and 1b that are adjacent to each other are Since the two intake valves 1a and 1b are made to be different from each other, a difference occurs between the lift amounts of the two intake valves 1a and 1b even though the two intake valves 1a and 1b are simultaneously driven by one rocker arm 7. In particular, the central valve 1b has a high head,
Even when driven by the first cam 3 having a wide angle, the amount of lift is smaller than that of the other valves 1a and 1b, and since it is the most distant from the exhaust valve, there is less substantial overlap. Therefore, even when driven with a single cam profile, different operating conditions can be obtained with adjacent valves, which can be intended to enhance the turbulence effect of the air-fuel mixture entering the combustion chamber. In particular, in order to further improve the high-speed performance of an internal combustion engine, it is effective to increase the number of valves per cylinder.
It is well known that three intake valves are provided per cylinder, but in reality, it cannot be overlooked that when emphasis is placed on high-speed performance, low-speed performance must be sacrificed to some extent. However, according to the valve train of the present invention, in the low speed range, by setting the cam profile of the second cam 4 and the lever ratio of the two arms 10a and 10b provided on the second rocker arm 7, One of the two intake valves 10a and 10b 1
0a is driven in a valve operating state suitable for the low speed range, and the other 10b is driven with an extremely small lift, and in the high speed range, the combined valve timing drive is such that the operating states of the plurality of valves are different from each other. This can be done by using a cam profile of the first cam 3 that is suitable for the high speed range. More preferably, the third cam 5 and the third cam of the cam profile corresponding to the extremely low speed range are preferably
By adding the intake valve 1c, there is no need to reduce the air-fuel mixture filling efficiency in the low speed range, so it is possible to achieve an even wider range of output characteristics. In the above embodiment, the hydraulic pressure is set in two stages, but it is also possible to subdivide the hydraulic oil supply passage into a plurality of systems and appropriately select the piston to be operated. Furthermore, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made by combining cam profiles. <Effects of the invention> As described above, according to the invention, two or more valves are simultaneously driven using a cam follower (rotsuka arm) having a plurality of arms with different lever ratios. A valve operating mechanism driven by composite valve timing in which the operating states of the valves are made different from each other can be easily realized without unnecessarily increasing the number of cams and cam followers. Therefore, it is possible to improve the intake air filling efficiency in the medium and low speed rotation range,
This has a great effect on flattening the engine's output characteristics over a wider rotational speed range.

[Brief explanation of the drawing]

FIG. 1 is a top view of a valve train based on the present invention. FIG. 2 is a sectional view taken along the - line in FIG. 1. FIG. 3 is a view taken along the arrows in FIG. FIG. 4 is a sectional view taken along the - line in FIG. 3. FIG. 5 is a hydraulic circuit diagram. 1a to 1c...Intake valve, 2...Camshaft, 3...
1st cam, 4...2nd cam, 5...3rd cam, 6
...First rocker arm, 7... Second rocker arm, 8... Third rocker arm, 9... Rocker shaft, 10a, 10b... Arm, 11a, 11
b... Tappet screw, 12a, 12b... Lock nut, 13... Cylinder head, 14... Guide hole, 15... Lifter, 16... Coil spring, 1
7...First coupling device, 18...Second coupling device, 1
9...Retainer, 20...Valve spring, 2
1...First guide hole, 22...Second guide hole, 2
3... Small diameter part, 24... Step part, 25... Piston,
26...Stopper, 27...Hydraulic chamber, 28...Coil spring, 29...Hydraulic oil supply passage, 30...Oil passage, 31...Communication hole, 40...Lubricating oil pump, 4
1... Pressure regulator, 42... First solenoid valve, 44
... relief valve, 45 ... discharge passage, 46 ... relief passage, 47 ... orifice, 48 ... back pressure passage, 49 ... second solenoid valve.

Claims (1)

[Claims for Utility Model Registration] Compatible with a plurality of cams with different contours formed on a camshaft that is installed at the intake or exhaust port of each combustion chamber of an internal combustion engine and rotates in synchronization with the crankshaft, and the plurality of cams. In a valve mechanism having a plurality of valves, two or more valves, which are driven to open by a plurality of cam followers, and a switching means for selecting connection and non-connection between mutually adjacent ones of the plurality of cam followers, At least some of the plurality of cam followers have a plurality of valve contact portions provided at portions having different lever ratios, and simultaneously drive valves in contact with each of the valve contact portions. A valve train for an internal combustion engine characterized by: