JPH0726915A - Valve system for engine - Google Patents

Abstract

PURPOSE:To reduce frictional loss in engine and increase the speed of a valve system in such an arrangement that intake and exhaust valves of an engine are closed by a mechanical spring such as a coil spring and a gas spring. CONSTITUTION:A mechanical spring 13 has an urging force for a closing a valve, which is set so that a speed limit is reached at a change-over speed N1 in a low engine speed range. An intake valve 6 and the like are driven by the mechanical spring 13 in a speed range which is lower than the change- over speed range N1, but are driven by a gas spring 7 so as to increase the urging force thereof for closing the valve in proportion to an increase in the engine speed. When no air pressure is fed to the gas spring 7, the drive of the intake valve and the like is ensured by the mechanical spring 13 in a fail- safe manner, and further, the valve closing load of the mechanical spring 13 is lowered while an air pump 39 is stopped to reduce frictional loss so as to reduce the possibility of occurrence of surging in a high speed range, thereby it is possible to increase the engine speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for an engine, and more particularly to a combination of a mechanical spring such as a coil spring and a gas spring utilizing gas pressure.

[0002]

2. Description of the Related Art Generally, a valve operating system for an engine includes an on-off valve (intake valve or exhaust valve) for opening and closing an opening end of an intake port or an exhaust port communicating with a combustion chamber of the engine to the combustion chamber, A mechanical spring composed of a coil spring or the like for urging the opening / closing valve in the closing direction is provided, and the opening / closing valve urged by the mechanical spring to resist the urging force of the spring by a cam at a predetermined timing. It is well known that the valve is opened.

When this mechanical spring is used, its spring load must be set so as to accurately trace the form of the cam without surging of the on-off valve, in order to secure this requirement up to the high rotation range of the engine. The spring load has been increased. However, in the low engine speed region, the valve closing biasing force of the spring is excessive, and the friction loss of the engine increases correspondingly.

As a valve actuating device capable of solving such a problem, there has been known a device in which the mechanical spring is replaced with a gas spring, as disclosed in, for example, JP-A-2-230910. By using this gas spring, the valve closing load of the spring can be changed according to the engine speed by changing the gas pressure in the pressure chamber, and an appropriate valve closing urging force corresponding to the engine speed can be obtained. The friction loss of the engine can be reduced, and the valve train can be rotated at high speed.

[0005]

However, in the above-mentioned prior art, since the closing valve urging force of the on-off valve is obtained by the load of the gas spring, the gas pressure to the pressure chamber of the gas spring may be increased for some reason. When the supply is cut off, the on-off valve does not open and close and the engine stops. Therefore, for example, in a mass-produced engine or the like, it is desirable to use a mechanical spring together with the gas spring as a so-called fail-safe countermeasure when the gas pressure is not supplied to the pressure chamber of the gas spring.

The present invention has been made in view of the above points, and an object thereof is to limit the structure when a mechanical spring is used together as a fail-safe in a gas spring as described above. The purpose is to make good use of the structure to reduce the friction loss of the engine and increase the rotation speed of the valve train.

[0007]

To achieve the above object, in the invention of claim 1, the spring load of the mechanical spring is set low so that the limit rotation speed of the spring is in the low rotation range of the engine. Then, the on-off valve is biased by the spring force of the mechanical spring in the low engine speed range, and when the engine speed rises above the limit speed of the mechanical spring, the on-off valve is closed by the gas spring. The valve was driven.

That is, according to the present invention, the operation of the engine is provided with the opening / closing valve for opening / closing the opening end of the port communicating with the combustion chamber to the combustion chamber, and the mechanical spring for urging the opening / closing valve in the valve closing direction. The valve device is a prerequisite.

Then, the valve closing biasing force of the mechanical spring is set so that the mechanical spring reaches the rotational limit at the switching rotational speed in the low rotational speed range of the engine.

Further, a gas spring having a pressure chamber communicating with the gas supply means, for urging the on-off valve in the valve closing direction by the gas pressure supplied to the pressure chamber, and the gas pressure in the pressure chamber of the gas spring A gas pressure adjusting means, an engine speed detecting means for detecting the engine speed, and an engine speed detected by the engine speed detecting means, when the engine speed increases above the switching speed, the pressure chamber in the gas spring. And a control means for controlling the gas pressure adjusting means so that the gas pressure increases in accordance with an increase in the engine speed.

According to the second aspect of the present invention, the control means controls the gas pressure so that the gas pressure decrease characteristic of the pressure chamber in the gas spring when the engine speed decreases is different from the gas pressure increase characteristic when the engine speed increases. The pressure adjusting means is controlled.

According to the third aspect of the invention, the control means controls the gas pressure adjusting means so that the gas pressure in the pressure chamber of the gas spring increases in proportion to the increase in the engine speed.

According to a fourth aspect of the present invention, in the engine valve operating system on the same premise as the first aspect of the present invention, the mechanical spring is closed so that the mechanical spring has a rotational limit at a switching rotational speed in a low rotational speed range of the engine. Set the valve biasing force.

Further, a gas spring having a pressure chamber communicating with the gas supply means, for biasing the on-off valve in the valve closing direction by the gas pressure supplied to the pressure chamber, and the gas pressure in the pressure chamber of the gas spring Depressurizing means for depressurizing the engine, rotational speed detecting means for detecting the engine rotational speed, and when the engine rotational speed detected by this rotational speed detecting means rises above the switching rotational speed, the gas in the pressure chamber of the gas spring While the pressure increases as the engine speed increases,
When the engine speed decreases to the switching speed from a speed higher than the switching speed, the gas pressure in the pressure chamber decreases in accordance with the decrease in the engine speed, and the decrease in the gas pressure is due to the switching speed. And a control means for controlling the pressure reducing means so as to be restricted at a higher predetermined rotation speed.

In this case, according to the invention of claim 5, the control means holds the gas pressure of the pressure chamber in the gas spring at a constant pressure for a predetermined time when the engine speed decreases to a predetermined speed higher than the switching speed. After that, the pressure reducing means is controlled so as to be zero.

According to a sixth aspect of the present invention, in the first, second, third or fifth aspect of the present invention, the gas supply means is drive-connected to the engine through the clutch means and is provided with pump means for discharging the pressurized gas. The configuration. Further, the control means is configured to hold the clutch means in a disengaged state when the engine is in a rotation range lower than the switching rotation speed.

According to a seventh aspect of the invention, in the first aspect of the invention, the gas supply means is between the pump means which is drivingly connected to the engine and discharges the pressurized gas, and the pump means and the pressure chamber of the gas spring. And an accumulator that stores gas pressure.

According to an eighth aspect of the invention, in the seventh aspect of the invention, the pump means is drivingly connected to the engine through the clutch means, and the pressure detecting means for detecting the pressure in the accumulator is further provided and controlled. The means is configured to switch the clutch means to the connected state when the pressure in the accumulator drops below a predetermined pressure.

In the invention of claim 9, the pressure reducing means is a hydraulic control valve comprising a valve hole communicating with the pressure chamber of the gas spring and a valve body for opening and closing the valve hole by hydraulic pressure.

[0020]

With the above construction, in the invention of claim 1, the on-off valve is driven by the mechanical spring to close the valve when the engine is in the rotation range lower than the switching speed. The switching speed is in the low engine speed range, and the valve closing bias is set so that the mechanical spring reaches the rotation limit in this low speed range, so the valve closing load of the mechanical spring is low. Therefore, it is possible to reduce the friction loss of the valve mechanism, and by extension, the engine. Moreover, when the gas supply means has a pump means driven by the engine, the pump means does not operate up to the switching speed, so that it is possible to prevent an increase in friction loss due to the operation of the pump means. It is possible to further reduce the friction loss.

When the engine rotational speed detected by the rotational speed detecting means rises above the switching rotational speed, the control means controls the gas pressure adjusting means and the on-off valve is driven to close by the gas spring. The gas pressure in the pressure chamber of the gas spring increases as the engine speed increases. In this way, in the rotation range above the switching speed, the on-off valve is driven to close by the gas spring,
The occurrence of surging such as mechanical springs in the high engine speed range is reduced, and the valve system can be operated at high speed.

Further, as described above, in the low engine speed range, the gas spring does not operate, and only the mechanical spring drives the on-off valve, so that the gas pressure cannot be supplied to the pressure chamber of the gas spring. Even if it disappears, the opening / closing valve can be driven by the mechanical spring as long as the engine is in the rotation range lower than the switching rotation speed, and fail-safe measures can be taken to ensure the operation of the engine.

According to the second aspect of the present invention, the control means controls the gas pressure so that the gas pressure decreasing characteristic of the pressure chamber in the gas spring when the engine speed decreases becomes different from the gas pressure increasing characteristic when the engine speed increases. The means are controlled. Hysteresis is obtained by the change of the gas pressure characteristic between the time when the engine speed increases and the time when the engine speed decreases, and it is possible to prevent unnecessary repetition of the operation of the gas pressure adjusting means.

According to the third aspect of the invention, the gas pressure adjusting means is controlled by the control means so that the gas pressure in the pressure chamber of the gas spring increases in proportion to the increase in the engine speed. Therefore, the spring constant of the gas spring can be set according to the engine speed.

According to the fourth aspect of the invention, when the engine speed detected by the speed detecting means rises above the switching speed, the depressurizing means is controlled by the control means to increase the pressure of the gas spring. The on-off valve is driven to be closed by the spring, and the gas pressure in the pressure chamber of the gas spring increases as the engine speed increases. On the other hand, when the engine speed drops to the switching speed from a speed higher than the switching speed, the gas pressure in the pressure chamber of the gas spring is controlled according to the decrease in the engine speed by the control of the pressure reducing means by the control means. Although the pressure is reduced, when the engine rotational speed reaches a predetermined rotational speed higher than the switching rotational speed, the operation of the pressure reducing means is suppressed and the pressure reduction of the gas pressure in the pressure chamber is limited. Therefore, the above-mentioned claim 1
In addition to the same operational effects as the invention described above, since the operation of the pressure reducing means is restricted in the middle of the decrease of the engine speed in this way, it is possible to prevent the unnecessary repetition of the operation of the pressure reducing means.

According to the fifth aspect of the invention, when the engine speed drops to a predetermined speed higher than the switching speed, the gas pressure in the pressure chamber of the gas spring becomes 0 after being kept at a constant pressure for a predetermined time. Therefore, the friction loss of the engine can be further reduced by the amount that the gas pressure becomes zero.

According to the sixth aspect of the invention, when the engine is in the rotation range lower than the switching speed, the control means holds the clutch means in a disengaged state to stop the drive of the pump means by the engine and the pump means. The supply of the pressurized gas from the pressure chamber to the pressure chamber is stopped, and the operation of the gas spring is stopped. Therefore, the operation of the gas spring can be stopped in the engine rotation range lower than the switching speed and the valve can be driven only by the mechanical spring with a simple structure. When the engine speed increases above the switching speed, the engine is driven to supply the pressurized gas from the pump means to the pressure chamber, and the gas spring operates.

According to the seventh aspect of the invention, the pressurized gas discharged from the pump means by the drive of the engine is stored in the accumulator. Then, when the engine speed is equal to or higher than the switching speed, pressurized gas is supplied to the pressure chamber not only from the pump means but also from the accumulator, and the gas spring operates. Since the pressurized gas from the accumulator is supplied to the pressure chamber of the gas spring in this manner, the responsiveness at the start of operation of the gas spring can be improved.

According to the eighth aspect of the present invention, the pressure in the accumulator is detected by the pressure detecting means, and when the internal pressure of the accumulator falls below a predetermined pressure, even if the engine speed is lower than the switching speed, the control means causes the pressure to drop. The clutch means is engaged and the pump means is activated. As a result, the internal pressure of the accumulator can always be kept substantially constant and the responsiveness at the start of operation of the gas spring can be further enhanced.

According to the ninth aspect of the invention, the valve body of the hydraulic control valve as the pressure reducing means is hydraulically controlled, and the valve hole is opened / closed by the control of the valve body to reduce the gas pressure in the pressure chamber of the gas spring. To be done. At this time, the height of the pressure reducing means can be set lower than in the case where the valve body is biased by a spring or the like to close the valve, and the layout can be made compact.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall structure of an engine valve operating system according to an embodiment of the present invention. Reference numeral 1 denotes a cylinder head of an OHC type engine. This cylinder head 1 has a piston (not shown) reciprocally fitted therein. Mounted on the upper surface of a cylinder block 3 having the mounted cylinder 2.
A combustion chamber 4 is formed that is surrounded by the inside, the top surface of the piston, and the lower surface of the cylinder head 1.

The cylinder head 1 has an intake port 5 as a downstream end of an intake passage for supplying intake air to the combustion chamber 4.
Are formed so as to open in the combustion chamber 4, and the opening end of the intake port 5 to the combustion chamber 4 is opened and closed by an intake valve 6 which is a poppet valve as an on-off valve. On the other hand, although not shown, an exhaust port as an upstream end of the exhaust passage is formed in the cylinder head 1 so as to discharge the exhaust gas in the combustion chamber 4, and the exhaust port is opened to the combustion chamber 4. The opening end to the chamber 4 is opened and closed by a similar exhaust valve as an opening / closing valve. Incidentally, mechanical type and gas springs 7 and 13 and the gas springs 7 described below
Since the control systems have the same configuration, only the intake valve 6 will be described and the exhaust valve will be omitted.

An annular gas spring 7 (air spring) as a gas spring for urging the intake valve 6 in the valve closing direction is attached to the upper end of the valve stem 6a of the intake valve 6. The gas spring 7 is a spring lower 8 arranged around the upper portion of the valve stem 6a of the intake valve 6.
And a spring upper 9, and a spring lower 8
Has a double structure of inner and outer wall portions 8a and 8b that are concentric with each other and is opened upward, and the bottom wall portion 8c is the cylinder head 1
Is abutted on the deck's upper surface. On the other hand, the spring upper 9 similarly has inner and outer wall portions 9a and 9b having a double structure and is opened downward. The inner wall portion 9a is on the outer peripheral surface of the inner wall portion 8a of the spring lower 8 and the outer wall portion 9b is Same outer wall 8
It is slidably abutted on the inner peripheral surface of b through seals 10 and 11, respectively. That is, the spring upper 9 is arranged concentrically with respect to the spring lower 8, and the opening of the spring upper 9 is slidably fitted in the opening of the spring lower 8. A sealed pressure chamber 12 is defined in a portion surrounded by 9. Then, the valve stem 6a of the intake valve 6 is centered on the upper wall portion 9c of the spring upper 9.
The upper end is fixedly attached.

The pressure chamber 12 of the gas spring 7 is also
A mechanical spring 13 composed of a coil spring for urging the intake valve 6 in the valve closing direction is disposed in a compressed state between the bottom wall portion 8c of the spring lower 8 and the upper wall portion 9c of the spring upper 9. The mechanical spring 13 has its valve closing urging force so that the mechanical spring 13 reaches its rotation limit when the engine speed N is in the low speed range and at a switching speed N1 (for example, N1 = 2000 rpm) higher than the idle speed. Is set.

A tappet 16 is arranged above the gas spring 7 to press the upper end of the valve stem 6a by a cam 15 on a cam shaft 14 against the biasing force of the springs 7 and 13 in the valve opening direction. ing.

In the bottom wall 8c of the spring lower 8 of the gas spring 7, a plurality of air inlets 17, 17,
... and air discharge ports 18, 18, ... (Only one of which is shown in the figure) are formed therethrough, and each air introduction port 17 has a bottomed valve fitting hole 1 that opens to the upper surface of the deck of the cylinder head 1.
9 and communicates with the pressure chamber 12 inside the valve fitting hole 19.
A check valve 20 is fitted to allow only the inflow of air into the inside. This check valve 20 has a valve fitting hole 19
A valve body 22 formed of a ball valve that opens and closes a valve hole 21 that opens on the bottom surface of the valve body, and a coil spring 23 that urges the valve body 22 in the closing direction. The pressure chamber 12 in the gas spring 7 is communicated with the pressurized air from the air supply hole 24 through the check valve 20 and the air introduction port 17.
The gas spring 7 is extended and biased to drive the intake valve 6 to close.

On the other hand, the bottom wall portion 8c of the spring lower 8 is
Each of the air outlets 18 in the above is communicated with a bottomed valve fitting hole 25 opened on the upper surface of the deck of the cylinder head 1,
In the valve fitting hole 25, a pressure reducing valve 26 is mounted as a pressure reducing means for discharging the air in the pressure chamber 12 to reduce the air pressure in the pressure chamber 12. That is, the pressure reducing valve 26 also constitutes gas pressure adjusting means for adjusting the gas pressure of the pressure chamber 12 by reducing the air pressure of the pressure chamber 12 of the gas spring 7, and is composed of a hydraulic control valve. Is. The pressure reducing valve 26 also serves as an oil drain check valve for discharging the lubricating oil accumulated in the gas spring 7 to prevent liquid compression. As shown in FIG. A valve hole 2 which is immovably fitted to the upper opening side of the mounting hole 25 and communicates with the pressure chamber 12 of the gas spring 7 at the center.
7, a valve seat portion 28 having a through-hole formed therein, a cylinder portion 29 immovably fitted in the lower part of the valve fitting hole 25, and a valve hole 2
7. A valve body 30 formed of a ball valve that is seated on a valve seat 27a at the bottom of the valve 7 and opens and closes the valve hole 27, is slidably fitted in the cylinder portion 29, and embraces the valve body 30 in a movable manner. An upper air discharge chamber 3 having a piston portion 31 and the inside of the cylinder portion 29 communicating with the valve hole 27 by the piston portion 31.
2 and the lower oil chamber 33, and the air discharge chamber 32
Is communicated with the space around the gas spring 7 through a passage 34 formed around the valve seat portion 28. On the other hand, the oil chamber 33 is communicated with an oil supply hole 35 formed through the cylinder head 1, and by supplying pressurized oil to the oil 33 chamber of the pressure reducing valve 26 from the oil supply hole 35, The body 30 is seated on the valve seat 27a to close the valve hole 27, and the pressure of the pressurized oil to the oil chamber 33 is changed to make the valve opening pressure of the valve body 30 (pressure reducing valve 26) variable so that the gas spring 7 The air pressure in the pressure chamber 12 is changed.

An air supply device 37 as a gas supply means is connected to the air supply hole 24 of the cylinder head 1. The air supply device 37 includes an air pump 39 as a pump unit that is drivingly connected to the engine through an electromagnetic clutch 38, and an air passage 40 that connects the air pump 39 to the air supply hole 24. Is an upstream check valve 41 that allows discharge air from the pump 39 to flow only to the downstream side, an air accumulator 42 that stores discharge air from the pump 39, and the upstream check valve. Four
A downstream check valve 43 having the same function as 1 and an electromagnetic opening / closing valve 44 for opening / closing the air passage 40 are provided.

Further, the oil supply hole 3 of the cylinder head 1
Reference numeral 5 is connected to an oil pump 46 which is drivingly connected to the engine through an oil passage 47, and the oil passage 47 is arranged so that the oil discharged from the pump 46 is discharged to the downstream side in order from the oil pump 46 toward the pressure reducing valve 26 side. The upstream side check valve 48 that only flows, the hydraulic accumulator 49 that stores the discharge oil from the pump 46, the downstream side check valve 50 that has the same function as the upstream side check valve 48, and the opening degree of the oil passage 47 are controlled. Opening pressure of the pressure reducing valve 26,
That is, an electromagnetic control valve 51 for adjusting the pressure in the pressure chamber 12 of the gas spring 7 by the pressure reducing valve 26 is provided.

The ON / OFF control of the electromagnetic clutch 38, the opening / closing control of the electromagnetic opening / closing valve 44, the operation of the oil pump 46 and the operation of the electromagnetic control valve 51 are performed by receiving control signals from a control unit 53 as a control means. It is supposed to be. This control unit 5
3 shows at least an output signal from a rotation sensor 54 as a rotation speed detecting means for detecting the engine speed N and an output signal from a pressure sensor 55 as a pressure detecting means for detecting the internal pressure P of the air accumulator 42. It has been entered.

Basically, as shown in FIG. 3, the control unit 53 closes the electromagnetic opening / closing valve 44 when the engine speed N detected by the rotation sensor 54 is lower than the switching speed N1. Also, the electromagnetic clutch 38 is turned off to turn off the pressure chamber 1 of the gas spring 7.
2 is not supplied with pressurized air, and the air pressure in the pressure chamber 12 is set to 0.
The intake valve 6 is closed and driven only by the mechanical spring 13. On the other hand, when the engine speed N rises above the switching speed N1, the electromagnetic opening / closing valve 44 is opened and the electromagnetic clutch 38 is turned on to supply pressurized air to the pressure chamber 12 of the gas spring 7. At this time, the valve opening pressure of the pressure reducing valve 26 is controlled by the electromagnetic control valve 51, and when the engine speed N increases, the air pressure in the pressure chamber 12 increases in proportion to the increase of the engine speed N, and conversely, When the rotation speed N decreases, the air pressure in the pressure chamber 12 is reduced in accordance with the decrease in the engine rotation speed N, and the decrease in the air pressure in the pressure chamber 12 is restricted at a predetermined rotation speed N2 higher than the switching rotation speed N1. The air pressure of 12 is maintained at a constant pressure for a predetermined time, and thereafter the air pressure of the pressure chamber 12 is set to zero.

Here, the ON / O of the electromagnetic clutch 38 is turned on.
The FF switching control operation will be described in more detail with reference to FIG. 4. In step S1 after the start, the engine speed N detected by the rotation sensor 54 and the pressure sensor 5 are detected.
The internal pressure P of the accumulator 42 detected by No. 5 is read, and in step S2, the engine speed N
And the switching speed N1 are compared. This judgment is N>
When YES in N1, the process proceeds to step S5, the electromagnetic clutch 38 is turned on to operate the air pump 39, and then the process returns. When the determination is NO in the case of N ≦ N1, the process proceeds to step S3, and this time the internal pressure P of the accumulator 42 is increased.
And its lower limit value P1 are compared. Where P ≦ P1
If NO is determined, the process proceeds to step S5, and the electromagnetic clutch 38 is forcibly turned on to set the air pump 39 to the ON state even though the engine speed N is lower than the switching speed N1.
Operate. On the other hand, if it is determined that P> P1 is YES, the process proceeds to step S4, the electromagnetic clutch 38 is turned off, and the process returns.

Next, the operation of the above embodiment will be described. The engine speed N is detected by the rotation sensor 54, the internal pressure P of the air accumulator 42 is detected by the pressure sensor 55, and the control unit 53 to which the output signals of these sensors 54, 55 are input causes electromagnetic opening / closing of the air supply device 37. Valve 44, electromagnetic clutch 3
8, electromagnetic control valve 51 of oil passage 47, oil pump 4
6 are each controlled in operation.

The engine speed N is set by the spring constant of the mechanical spring 13, and the switching speed N is set.
When it is lower than 1, the electromagnetic opening / closing valve 44 is closed and the electromagnetic clutch 38 is turned off. As a result, pressurized air is not supplied to the pressure chamber 12 of the gas spring 7, and the air pressure of the pressure chamber 12 becomes 0, so that the intake valve 6
The (exhaust valve) is closed and driven only by the mechanical spring 13.

At this time, the switching speed N1 is in the low engine speed range, and the mechanical spring 13 is in that speed range.
Since the valve closing urging force is set so as to reach the rotational limit, the valve closing load of the mechanical spring 13 may be low, and the valve operating mechanism, and eventually the engine friction loss, may be reduced accordingly. be able to.

Moreover, the engine power for driving the air pump 39 is not required, and the output loss of the engine can be further reduced.

When the engine speed N rises above the switching speed N1, the electromagnetic opening / closing valve 44 is opened and the electromagnetic clutch 38 is turned on to activate the pressure chamber 12 of the gas spring 7.
Pressurized air is supplied to the gas spring 7, and the gas spring 7 operates.
That is, as the air pressure in the pressure chamber 12 rises, the spring upper 9 of the gas spring 7 is urged in a direction away from the spring lower 8, and the gas spring 7 is in an extended state, so that the intake valve 6 (which is connected to the spring upper 9). The exhaust valve) is driven in the valve closing direction. At the same time,
The opening pressure of the pressure reducing valve 26 is controlled by the electromagnetic control valve 51 to adjust the air pressure in the pressure chamber 12, and the gas spring 7
The valve closing force of is changed. That is, normally, as shown in FIG. 2A, the pressure in the oil chamber 33 of the pressure reducing valve 26 is increased, the piston portion 31 moves upward in the cylinder portion 29, and the valve body 30 closes the valve hole 27. However, during depressurization, as shown in FIG. 2B, the pressure in the oil chamber 33 of the depressurization valve 26 is lowered, the piston portion 31 moves downward in the cylinder portion 29, and the valve body 30 opens the valve hole 27. As a result, the pressure in the pressure chamber 12 of the gas spring 7 is reduced. Therefore, by changing the valve opening pressure of the pressure reducing valve 26 by the oil pressure to the oil chamber 33, the gas spring 7
The pressure in the pressure chamber 12 is adjusted.

More specifically, when the engine speed N increases from the switching speed N1, the air pressure in the pressure chamber 12 increases in proportion to the increase of the engine speed N, as shown by the solid line in FIG. To do. In this way, the gas pressure in the pressure chamber 12 increases in proportion to the increase in the engine speed N, so that the valve closing biasing force of the gas spring 7 can be set to a value corresponding to the engine speed N.

On the other hand, when the engine speed N decreases, the air pressure in the pressure chamber 12 decreases as the engine speed N decreases, as shown by the broken line in FIG. When the engine speed N drops to a predetermined speed N2 which is higher than the switching speed N1, a predetermined time period
The opening pressure of the pressure reducing valve 26 is kept constant, the decrease of the air pressure of the pressure chamber 12 is limited, the air pressure is kept constant, and after a certain period of time, the opening pressure of the pressure reducing valve 26 remains the same as before. Finally, the air pressure in the pressure chamber 12 becomes zero.

Therefore, in this embodiment, when the engine speed N is lower than the switching speed N1, the gas spring 7 does not operate as described above, and only the mechanical spring 13 operates the intake valve 6 (exhaust valve). Since it is driven, even if the air pressure is not supplied to the pressure chamber 12 of the gas spring 7 due to a malfunction of the air supply device 37 or the like, as long as the engine is in a rotation range lower than the switching rotation speed N1, it is mechanical type. The spring 13 can drive the intake valve 6 (exhaust valve), so that fail-safe measures can be taken to ensure operation of the engine. In that case, the operation of the engine may be restricted so that the engine speed N does not rise above the switching speed N1.

When the engine is in the rotation range lower than the switching rotation speed N1, the electromagnetic clutch 38 is turned off to stop the drive of the air pump 39 by the engine and the operation of the gas spring 7 to be stopped. It is possible to achieve the valve drive by the simple spring 13 with a simple structure.

On the other hand, the engine speed N is the switching speed N1.
In the above case, the gas spring 7 drives the intake valve 6 (exhaust valve) to close, so that the occurrence of surging like the mechanical spring 13 in the high rotation range of the engine is reduced, and the high speed rotation of the valve system is achieved. Can be achieved.

Further, in the operating state of the gas spring 7, the air pressure decrease characteristic of the pressure chamber 12 in the gas spring 7 when the engine speed N decreases is different from the air pressure increase characteristic when the engine speed increases, unlike the engine speed increase characteristic. When the number N reaches a predetermined rotation speed N2 which is higher than the switching rotation speed N1, the operation of the pressure reducing valve 26 is suppressed and the decrease of the air pressure in the pressure chamber 12 is limited, and the air pressure is maintained at a constant pressure for a predetermined time and then becomes 0. Becomes That is, hysteresis is obtained by the change in the gas pressure characteristic when the engine speed N increases and decreases, and the number of times the pressure reducing valve 26 is operated can be reduced, and unnecessary repetition of the operation can be prevented. Moreover, since the air pressure in the pressure chamber 12 becomes 0 after being kept at a constant pressure for a predetermined time, the friction loss of the engine can be further reduced by the amount that the air pressure becomes 0.

Further, the air passage 40 of the air supply device 37.
Since the air accumulator 42 that stores the pressurized air discharged from the air pump 39 is disposed in the air pump 3, when the engine speed N becomes the switching speed N1 or more, the air pump 3
The pressurized air is supplied to the pressure chamber 12 not only from the air accumulator 42 but also from the air accumulator 42.
The responsiveness at the time of starting the operation of can be enhanced.

Moreover, the engine speed N is the switching speed N.
When it is lower than 1, the internal pressure P of the accumulator 42 detected by the pressure sensor 55 is compared with the lower limit value P1, and when the internal pressure P becomes lower than the lower limit value P1 and becomes low pressure, the engine speed N is switched. The electromagnetic pump 38 is forcibly turned on and the air pump 39 is operated even though it is lower than the number N1. As a result, the accumulator 42
The internal pressure P can always be kept higher than the lower limit value P1, and the responsiveness at the time of starting the operation of the gas spring 7 can be further enhanced.

Further, the pressure reducing valve 26 for discharging the air in the pressure chamber 12 of the gas spring 7 to reduce the pressure thereof is a hydraulic control valve for directly driving the valve body 30 by hydraulic pressure to open and close the valve hole 27. , The valve body 3 of the pressure reducing valve 26
The height of the pressure reducing valve 26 can be set lower than that of the structure in which 0 is biased by a spring or the like to close the valve, and the layout can be made compact.

Further, since the pressure reducing valve 26 also serves as an oil drain check valve, even if lubricating oil collects in the pressure chamber 12 of the gas spring 7,
The pressure reducing valve 26 opens to open the pressure chamber 12 of the gas spring 7.
When the air inside is discharged from the valve hole 27, the lubricating oil together with the air can be smoothly discharged from the pressure chamber 12, and the liquid compression due to the oil filling of the gas spring 7 can be reliably prevented. it can.

In the above embodiment, the valve opening pressure of the pressure reducing valve 26 is variably adjusted by hydraulic pressure to change the air pressure in the pressure chamber 12 of the gas spring 7 to change the valve closing urging force of the gas spring 7. However, in addition to this, the pressure supplied into the pressure chamber 12 of the gas spring 7 may be directly variably adjusted.

Further, in the above-mentioned embodiment, the mechanical spring 13 is constituted by the coil spring, but an elastic body having other constitution can be used. Further, a gas other than air may be used for the gas spring 7.

Further, although the mechanical spring 13 is fitted in the gas spring 7 in the above embodiment, it goes without saying that it may be arranged outside the gas spring 7.

[0061]

As described above, according to the first aspect of the present invention, when the opening and closing valves such as the intake valve and the exhaust valve of the engine are closed and driven by the mechanical spring and the gas spring, the mechanical spring is the engine. The closing valve biasing force is set so that the rotation speed reaches the rotation limit at the switching speed in the low rotation speed range, and the opening / closing valve is driven by the mechanical spring in the rotation speed range lower than this switching speed, while the switching speed is higher than the switching speed. In the rotation range of, the on-off valve is driven by the gas spring while increasing the valve closing urging force according to the increase in the rotation speed, so that when the gas pressure is not supplied to the pressure chamber of the gas spring, The drive of the on-off valve can be secured by a mechanical spring to ensure fail-safe measures. Further, by utilizing this configuration, the valve closing load of the mechanical spring can be set low, and when the gas pressure is supplied by the pump means, it is not necessary to operate the pump means in the rotation range lower than the switching rotation speed. It is possible to prevent an increase in friction loss due to the operation of the pump means and reduce the friction loss in the low engine speed region. Furthermore, it is possible to reduce the occurrence of surging such as mechanical springs in a high rotation range, and to achieve high rotation of the valve train.

According to the second aspect of the present invention, the gas pressure decreasing characteristic of the pressure chamber in the gas spring when the engine speed decreases is different from the gas pressure increasing characteristic when the engine speed increases, so that the engine speed is increased. Hysteresis of the gas pressure characteristic can be obtained when the number increases and decreases, and unnecessary repetition of the operation of the gas pressure adjusting means for adjusting the gas pressure in the pressure chamber of the gas spring can be prevented.

According to the third aspect of the present invention, the gas pressure in the pressure chamber of the gas spring is increased in proportion to the increase in the engine speed, so that the spring constant of the gas spring is set to the engine speed. It can be set to the corresponding spring constant.

According to the fourth aspect of the invention, similarly to the first aspect of the invention, the opening / closing valve is driven by the gas spring in the rotation range of the engine rotation speed lower than the switching rotation speed, and at that time, the engine rotation speed is increased. When the pressure drops, the gas pressure in the pressure chamber of the gas spring is reduced by the pressure reducing means, and the operation of the pressure reducing means is restricted before the pressure decreases to the switching rotation speed. In addition to being able to play, it is possible to prevent unnecessary repetition of the operation of the pressure reducing means.

According to the fifth aspect of the invention, when the engine speed drops to a predetermined speed higher than the switching speed, the gas pressure in the pressure chamber of the gas spring is maintained at a constant pressure for a predetermined time and then becomes 0. By doing so,
The friction loss of the engine can be further reduced.

According to the sixth aspect of the present invention, the gas supply means is provided with a pump means drivingly connected to the engine through the clutch means, and when the engine is in a rotation range lower than the switching speed. By disengaging the clutch means and stopping the operation of the pump means, it is easy to stop the gas spring in the engine speed range lower than the switching speed and drive the valve only by the mechanical spring. Can be achieved with a simple configuration.

According to the seventh aspect of the present invention, the gas supply means has a pump means driven by the engine, and the accumulator is arranged between the pump means and the pressure chamber of the gas spring. When the rotation speed is equal to or higher than the switching rotation speed, pressurized gas can be supplied to the pressure chamber of the gas spring not only from the pump means but also from the accumulator, and the responsiveness at the start of operation of the gas spring can be improved.

According to the invention of claim 8, the pump means is drivingly connected to the engine through the clutch means, and the clutch means is switched to the connected state when the pressure in the accumulator drops below a predetermined pressure. As a result, when the accumulator internal pressure falls below a predetermined pressure, the pump means can be operated to keep the accumulator internal pressure almost constant even when the engine speed is lower than the switching speed, and the gas spring starts operating. It is possible to further improve the time responsiveness.

According to the invention of claim 9, the pressure reducing means is a hydraulic control valve comprising a valve hole communicating with the pressure chamber of the gas spring and a valve body for hydraulically opening and closing the valve hole. The height can be set low to make the layout compact.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a pressure reducing valve and its operating state.

FIG. 3 is a characteristic diagram showing characteristics of air pressure in a gas spring according to engine speed.

FIG. 4 is a flowchart showing a control operation of a clutch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 4 Combustion chamber 5 Intake port 6 Intake valve (open / close valve) 7 Gas spring 12 Pressure chamber 13 Mechanical spring 26 Pressure reducing valve (pressure reducing means, gas pressure adjusting means) 27 Valve hole 29 Cylinder part 30 Valve body 31 Piston part 37 air supply device (gas supply means) 38 electromagnetic clutch 39 air pump (pump means) 42 air accumulator 53 control unit (control means) 54 rotation sensor (rotation speed detection means) 55 pressure sensor (pressure detection means) N engine rotation speed N1 Switching speed P Accumulator internal pressure

Claims (9)

[Claims] 1. A valve operating system for an engine, comprising: an opening / closing valve for opening / closing an opening end of a port communicating with the combustion chamber to the combustion chamber; and a mechanical spring for urging the opening / closing valve in a valve closing direction. The mechanical spring sets a valve closing urging force of the spring so that the mechanical spring has a rotation limit at a switching rotation speed in a low rotation range of the engine, and has a pressure chamber communicating with the gas supply means, and is supplied to the pressure chamber. Gas spring for urging the on-off valve in the closing direction by the gas pressure, gas pressure adjusting means for adjusting the gas pressure in the pressure chamber of the gas spring, rotation speed detecting means for detecting the engine speed, and the rotation speed When the engine speed detected by the number detecting means rises above the switching speed, the gas pressure adjusting means for increasing the gas pressure in the pressure chamber of the gas spring in accordance with the increase in the engine speed. Valve operating system for an engine, characterized in that a control means for controlling. 2. The engine valve operating system according to claim 1, wherein the control means has a gas pressure decrease characteristic of the pressure chamber in the gas spring when the engine speed decreases, and a gas pressure increase characteristic when the engine speed increases. A valve operating device for an engine, characterized in that the gas pressure adjusting means is controlled so as to have a characteristic different from that of the characteristic. 3. The engine valve operating system according to claim 2, wherein the control means includes a gas pressure adjusting means so that the gas pressure in the pressure chamber of the gas spring increases in proportion to an increase in the engine speed. An engine valve operating device characterized by being configured to control. 4. A valve operating system for an engine, comprising: an opening / closing valve for opening / closing an opening end of a port communicating with the combustion chamber to the combustion chamber; and a mechanical spring for urging the opening / closing valve in a valve closing direction. The mechanical spring sets a valve closing urging force of the spring so that the mechanical spring has a rotation limit at a switching rotation speed in a low rotation range of the engine, and has a pressure chamber communicating with the gas supply means, and is supplied to the pressure chamber. Gas spring for urging the on-off valve in the closing direction by the gas pressure, pressure reducing means for reducing the gas pressure in the pressure chamber of the gas spring, rotation speed detecting means for detecting the engine speed, and rotation speed detection When the engine speed detected by the means rises above the switching speed, the gas pressure in the pressure chamber of the gas spring increases in accordance with the increase in the engine speed, while the engine speed increases. When the switching speed decreases from a speed higher than the switching speed, the gas pressure in the pressure chamber decreases in accordance with the decrease in the engine speed, and the decrease in the gas pressure is higher than the predetermined speed. A valve operating system for an engine, comprising: a control unit that controls the pressure reducing unit so as to be limited in number. 5. The engine valve operating system according to claim 4, wherein the control means controls the gas pressure in the pressure chamber of the gas spring to be a constant pressure when the engine speed drops to a predetermined speed higher than the switching speed. A valve operating device for an engine, characterized in that the pressure reducing means is controlled so as to be zero after being held for a predetermined time. 6. The engine valve operating system according to claim 1, 2, 3 or 5, wherein the gas supply means includes pump means drivingly connected to the engine via clutch means and discharging pressurized gas. A valve operating system for an engine, wherein the control means is configured to hold the clutch means in a disengaged state when the engine is in a rotation range lower than the switching speed. 7. A valve operating system for an engine according to claim 1, wherein the gas supply means is between the pump means drivingly connected to the engine and discharging pressurized gas, and the pump means and the pressure chamber of the gas spring. And a valve accumulator for accumulating gas pressure. 8. The engine valve operating system according to claim 7, wherein the pump means is drivingly connected to the engine through the clutch means, and pressure detection means for detecting the pressure in the accumulator is provided, and the control means is the accumulator. A valve operating system for an engine, wherein the clutch means is switched to an engaged state when the internal pressure drops below a predetermined pressure. 9. The engine valve operating system according to claim 4, wherein the pressure reducing means is a hydraulic control valve including a valve hole communicating with the pressure chamber of the gas spring and a valve body for opening and closing the valve hole by hydraulic pressure. A valve operating system for an engine, which is characterized by being present.