JP2724745B2 - Valve train for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Industrial Application Field The present invention relates to an engine valve having a valve body provided at the tip of a valve shaft, which is elastically biased in a valve closing direction. The present invention relates to a valve operating device for an internal combustion engine in which a driving member for driving the engine valve in a valve opening direction is interlocked and connected to a rear end of a valve shaft portion while being openably and closably supported by an engine body.

(2) Prior Art Conventionally, such an apparatus is well known, for example, from JP-A-64-36906.

(3) Problems to be Solved by the Invention By the way, in the above conventional device, the engine valve is urged in the valve closing direction by the valve spring, and the engine member is driven in the valve opening direction by the driving member against the spring urging force. I am trying to do it. However, in the case of using such a spring force, it is sometimes difficult to operate an engine valve corresponding to a high engine speed because the natural frequency of the valve spring is limited.

Therefore, a prior art in which an engine valve is biased in a valve closing direction using an air spring as shown in FIG. 5 has also been realized. In this prior art, a bottomed cylindrical lifter 12 driven by a cam 8 as a driving member is slidably fitted in a guide hole 35 provided in the engine body 1 while a valve shaft in the intake valve 5 or the exhaust valve is provided. A piston 16 abutting on the rear end of the portion 5a and fixed in the middle of the valve shaft portion 5a is slidably fitted to the sleeve 10 with its front surface facing the pneumatic chamber 13.

According to such a configuration of the prior art, the intake valve 5 or the exhaust valve is urged in the valve closing direction by the air pressure of the pneumatic chamber 13, and it is not necessary to consider the resonance limit due to the natural frequency. It becomes possible to drive with. However, at the position above the sleeve 10 in the engine body 1,
A portion for guiding the valve shaft 5a of the intake valve 5 or the exhaust valve must be provided, and the overall height is increased accordingly.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a valve train for an internal combustion engine that is compactly configured to enable high engine speed.

B. Configuration of the Invention (1) Means for Solving the Problems According to a first feature of the present invention, a guide for allowing a valve shaft to pass through an airtight and movably through a sleeve fixed to an engine body. A bottomed sliding hole having a hole at the bottom is provided, and a bottomed cylindrical lifter slidably fitted in the sliding hole is interposed between the driving member and the rear end of the valve stem, and A piston inserted into the lifter is fixed to a position near the rear end of the valve shaft portion while being fitted into the sliding hole via a seal member while forming an air pressure chamber with the bottom of the moving hole.

According to the second feature of the present invention, in addition to the configuration of the first feature, a communication groove that can communicate between the lifter and the piston on the lifter side with respect to the seal member is provided on the inner surface of the slide hole. Drilled open to the outside.

(2) Operation According to the configuration of the first feature, the engine valve is driven in the valve opening direction while the volume of the pneumatic chamber is contracted by the piston in response to the lifter being pressed by the driving member. The air pressure generated in the air pressure chamber urges the engine valve in the valve closing direction. Moreover, since the lifter into which a part of the piston is inserted is slidably fitted in the sliding hole of the sleeve, it is not necessary to provide a portion for guiding the lifter above the engine valve.

Further, according to the configuration of the second feature, the vacant space generated between the lifter and the piston can be communicated with the outside by the communication groove, and the pressurization and decompression of the vacant space can be avoided.

(3) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, in FIG. 1, an engine main body 1 communicates with an intake valve port 3 provided facing a ceiling surface of a combustion chamber 2. An intake port 4 is provided, and an intake valve 5 serving as an engine valve is vertically movably guided by a guide cylinder 6 provided in the engine body 1 to open and close the intake valve port 3. That is, the intake valve 5
Is provided with a valve body 5b capable of opening and closing the intake valve port 3 at the tip of a valve shaft 5a slidably communicated within the guide cylinder 6, and the valve shaft 5a is driven up and down. .

At the position above the valve shaft 5a in the intake valve 5, the valve shaft 5
A valve camshaft 7 having an axis perpendicular to 5a is rotatably disposed, and the valve camshaft 7 is driven to rotate by a crankshaft (not shown). Moreover, the valve operating camshaft 7 has
A cam 8 as a drive member having a base circle portion 8a corresponding to the closing timing of the intake valve 5 and a high-order portion 8b corresponding to the opening timing of the intake valve 5 is provided integrally.

On the other hand, a sleeve 10 is fixed to an upper portion of the engine body 1 at a position corresponding to the intake valve 5. The sleeve 10 has a bottomed sliding hole 11 which is opened upward and is coaxial with the valve stem 5a. The bottom of the sliding hole 11 has a guide cylinder 6 for the valve stem 5a.
A guide hole 9 is formed to movably penetrate a portion protruding upward from the hole. Further, a lifter 12 formed in a cylindrical shape with a bottom is slidably fitted in the sliding hole 11 with its closed end at an upper position. The outer surface of the closed end of the lifter 12 is in sliding contact with the cam 8, and the inner surface of the closed end of the lifter 12 is connected to the intake valve 5.
At the rear end, that is, the upper end, of the valve stem 5a. Therefore, the lifter 12 is interposed between the cam 8 and the valve shaft 5a.

A portion near the rear end of the valve shaft portion 5a is fitted into the sliding hole 11 via a sealing member 14 made of an elastic material while forming an air pressure chamber 13 with the bottom of the sliding hole 11. At the same time, a piston 16 inserted into the lifter 12 is fixed while forming an empty space 15 with the lifter 12 closed end. This piston 16
An outer cylindrical portion having an annular groove 17 on the outer surface for fitting the seal member 14
16a, an inner cylindrical portion 16b arranged coaxially with the outer cylindrical portion 16a,
It is formed in a bottomed double cylindrical shape comprising a flat connecting plate portion 16c connecting one end of the outer tubular portion 16a and one end of the inner tubular portion 16b, and the connecting plate portion 16c is formed in the sliding hole 11 with the lifter 12 side. Mated.
Moreover, the outer diameter of the portion of the outer cylindrical portion 16a inserted into the lifter 12 is set to such an extent that an annular minute gap is formed between the outer cylindrical portion 16a and the inner surface of the lifter 12.

An annular engagement groove 18 is provided in a portion near the rear end of the valve shaft portion 5a, and a split cotter 19 that engages with the engagement groove 18 is provided.
The piston 16 is fixed to the portion near the rear end of the valve stem 5a via the shaft. That is, the inner cylindrical portion 16b of the piston 16 is provided with a through hole 20 formed in a tapered shape having a smaller diameter toward the pneumatic chamber 13 side, and the outer surface of the cotter 19 also has a smaller diameter toward the pneumatic chamber 13 side. It is formed in a tapered shape. Thus, the cotter 19 engaged with the engagement groove 18 is press-fitted into the through hole 20 from the empty chamber 15 side, so that the piston 16
Coaxially fixed to 5a.

By the way, in order to prevent the air in the pneumatic chamber 13 from leaking between the guide hole 9 and the valve shaft portion 5a and between the joint surfaces of the engine body 1 and the sleeve 10, between the joint surfaces of the engine body 1 and the sleeve 10 Is provided with an O-ring 21 surrounding the guide cylinder 6. The air in the pneumatic chamber 13 is
A valve shaft seal member 22 is attached to the inner end of the inner cylindrical portion 16b of the piston 16 in order to prevent leakage from the space between the outer surface of the valve shaft 5a and the inner surface of the through hole 20 into the empty chamber 15. As shown in FIG. 2, the seal member 22 has a radially outward portion formed at the end of the cylindrical portion 22a, which is formed in a substantially cylindrical shape, so as to penetrate the valve shaft portion 5a in close contact with the outer surface thereof. Flange portion 22b is provided integrally,
It is formed by an elastic member. Moreover, the outer surface of the cylindrical portion 22a is formed in a tapered shape corresponding to the through hole 20 and having a smaller diameter toward the flange portion 22b.

In FIG. 3, a seal member 14 fitted in an annular groove 17 provided on the outer surface of an outer cylindrical portion 16a of the piston 16 is provided with a support portion 14a having a substantially L-shaped cross section fitted in the annular groove 17.
A small-diameter end of a lip portion 14b formed so as to have a larger diameter as it goes downward so that the outermost periphery slides on the inner surface of the sliding hole 11 under the pressure in the pneumatic chamber 13 is provided continuously. It is formed in a substantially U-shaped cross section opened toward the pneumatic chamber 13.

In FIG. 4, a communication groove 23 extending in the axial direction is formed in the inner surface of the sliding hole 11 of the sleeve 10 so that the upper end communicates with the outside. Moreover, the lower end position of the communication groove 23 is
When the lifter 12 is in sliding contact with the base circular portion 8a of the cam 8 and the intake valve 5 is closed, that is, when the piston 16 is at the uppermost position, the lifter 12
And it is set so as to communicate with the vacant chamber 15 through the space between the piston 16 and the piston 16.

A pressurized air supply 27 is connected to the sleeve 10 via a pipe 26 having a check valve 25. This check valve 25
Corresponds to the pressure of the pressurized air supply 27 as the air pressure in the pneumatic chamber 13 becomes lower than the air pressure of the pressurized air supply 27 by a certain pressure or more.
From the pressurized air supply source 27.
g / cm ² of pressurized air is supplied, and the check valve 25 is
(3) The valve opens when the internal pressure becomes 4 kg / cm ² or less.

A relief valve 29 is connected to the pneumatic chamber 13 via a relief passage 28 formed in the sleeve 10. The relief valve 29 is set to open at a valve opening pressure (for example, 16 kg / cm ²⁾ corresponding to the maximum pressure in the pneumatic chamber 13 when a predetermined amount of lubricating oil is accumulated in the pneumatic chamber 13. The relief passage 28 is formed in the sleeve 10 so as to communicate with the air pressure chamber 13 at a position below the oil level 1 of the lubricating oil accumulated in the air pressure chamber 13 by the predetermined amount and above the guide hole 9.

The relief valve 29 is disposed in the sleeve 10 so as to be interposed between a passage 30 opened to the outer surface and formed in the sleeve 10 and the relief passage 28.
A spherical valve element 31 communicating between 28 and the passage 30 and capable of being shut off,
A spring 32 for urging the valve element 31 in the valve closing direction.

Incidentally, a concave portion 33 is provided at the center of the bottom of the sleeve 10 so as to surround the valve shaft portion 5a penetrating through the guide hole 9 and protruding into the pneumatic chamber 13.

Next, the operation of this embodiment will be described. When the valve operating camshaft 7 is driven to rotate by the crankshaft, the lifter 12
Is driven downward in accordance with the sliding contact of the cam 8 with the high-order portion 8b, whereby the valve shaft 5a of the intake valve 5 is driven downward and the intake valve 5 is opened.

At this time, the piston 16 fixed to the portion near the rear end of the valve shaft 5a is also pressed downward while reducing the volume of the pneumatic chamber 13, so that air pressure is generated in the pneumatic chamber 13. As a result, the intake valve 5 is urged upward, that is, in the valve closing direction, by the air pressure, and the cam 8 opens the intake valve 5 against the urging force in the valve closing direction due to the air pressure.
Therefore, when the cam 8 rotates to a position where the base circle portion 8a slides on the lifter 12, the lifter 12 rises by the air pressure of the air pressure chamber 13 so as to slide on the base circle portion 8a, and the intake valve 5 is closed.

According to the structure in which the intake valve 5 is urged in the valve closing direction by the air pressure, it is not necessary to consider the resonance limit due to the natural frequency as compared with the structure in which the valve is urged to close by using a valve spring. Can be operated at a higher rotation speed.

In addition, according to the valve train, the lifter 12 is slidably fitted in the sliding hole 11 of the sleeve 10 in which the piston 16 is fitted, so that the lifter 12 is guided to a position above the sleeve 10. As compared with the configuration provided with the above, the overall size can be reduced, and the length of the valve shaft portion 5a can be reduced to cope with higher rotation.

Further, when the intake valve 5 is in the closed state, the vacant chamber 15 communicates with the outside through the gap between the lifter 12 and the piston 16 and the communication groove 23, so that the pressure in the vacant chamber 15 abnormally increases. However, it is possible to prevent dance and noise from occurring due to the lift of the lifter 12. Further, it is also possible to bleed air from the empty space 15 when the lifter 12 is assembled, and it is also possible to avoid that the pressure of the empty room 15 increases during the assembly and the piston 16 is detached from the valve shaft portion 5a. Vacancy 15 when removing
The vacuum chamber 15 can be prevented from being depressurized by the introduction of air into the interior, and the removal operation can be facilitated.

Further, the valve shaft seal member 22 is provided with the through hole 20 of the piston 16.
A cylindrical portion formed in a substantially cylindrical shape corresponding to the through hole 20
22a is elastically fitted from the pneumatic chamber 13 side and is mounted on the inner end of the inner cylindrical portion 16b of the piston 16, so that it is easy to attach and detach and it is necessary to provide a specially shaped mounting portion on the piston 16 side. Therefore, the structure can be simplified, and the weight and the number of processing steps can be reduced. Moreover, the valve shaft seal member 22 exerts a resilient force when mounted on the piston 16, and can hold the piston 16 on the valve shaft portion 5a.
The operation of press-fitting into the through hole 20 is facilitated. Moreover, the valve shaft seal member 22 is moved by the air pressure in the air pressure chamber 13 into the inner cylindrical portion 16.
A flange portion 22b is closely attached to the inner end of b, and exhibits a sufficient sealing action.

The communication groove 23 introduces a part of the lubricating oil supplied toward the sliding surfaces of the cam 8 and the lifter 12 into the sliding hole 11 as the lubricating oil between the inner surface of the sliding hole 11 and the piston 16. It also performs a function. The seal member 14 fitted to the outer surface of the piston 16 is formed in a substantially U-shaped cross section opened toward the pneumatic chamber 13, and the outermost periphery of the lip portion 14 b slides on the inner surface of the slide hole 11. When the piston 16 descends, that is, when the intake valve 5 opens, the lip portion 14b scrapes the lubricating oil introduced from the communication groove 23 downward, and when the piston 16 rises. That is, when the intake valve 5 is closed, the lip portion 14b operates so as to get over the oil film adhered to the inner surface of the sliding hole 11. Therefore, lubricating oil is smoothly supplied into the sliding hole 11, and lubrication between the piston 16 and the inner surface of the sliding hole 11 is improved.

When the lubricating oil supplied in this way accumulates in the pneumatic chamber 13, the pneumatic chamber at the time of the maximum opening of the intake valve 5 is opened.
The maximum pressure in 13 also rises. When a predetermined amount or more of lubricating oil accumulates in the pneumatic chamber 13 and the maximum pressure in the pneumatic chamber 13 exceeds the opening pressure of the relief valve 29, the relief valve 29
Opens. When the relief valve 29 is opened, the relief passage 28 communicates with the air pressure chamber 13 at a position lower than the predetermined amount of the lubricating oil level 1, so that the lubricating oil mainly passes through the relief passage 28, the relief valve 29, and the passage. Since the air in the pneumatic chamber 13 is discharged to the outside via the air, it is possible to prevent the air in the pneumatic chamber 13 from being discharged without darkness.

In addition, the relief passage 28 communicates with the inside of the pneumatic chamber 13 at a position above the guide hole 9, and a recess 33 is provided at the bottom of the slide hole 11 at a position above the guide hole 9, so that the valve shaft Department
The lubricating oil necessary for lubrication between 5a and the inner surface of the guide hole 9 is
Therefore, lubrication between the valve stem 5a and the sleeve 10 can be sufficiently achieved.

Further, when the air in the pneumatic chamber 13 decreases due to leakage or the like, the pressurized air is supplied from the pressurized air supply source 27 into the pneumatic chamber 13 through the check valve 25, so that the minimum pressure in the pneumatic chamber 13 is maintained. Therefore, it is possible to secure an urging force enough to surely close the intake valve 5.

In the above embodiment, the lifter 12 is slidably fitted into the slide hole 11, but a portion for guiding the lifter 12 may be provided above the sleeve 10. At this time, the valve shaft seal member 22 may be arranged at the lowest position of the piston 16, but in such a case, when the cotter 19 is pressed into the through hole 20 from above, the valve shaft seal member 22 can resiliently contact the bottom of the sliding hole 11 to perform a buffering action.

In the above embodiments, the intake valve 5 as the engine valve has been described, but the present invention is also applicable to a valve train for an exhaust valve. Also, the present invention is applicable to a valve train in which power from the cam is applied to the lifter via a rocker arm as a driving member instead of directly sliding the cam on the lifter.

C. Effects of the Invention As described above, according to the first feature of the present invention, the sleeve fixed to the engine main body has a guide hole at the bottom portion that allows the valve shaft to penetrate airtightly and movably. A bottomed sliding hole is provided, and a bottomed cylindrical lifter slidably fitted in the sliding hole is interposed between the driving member and the rear end of the valve shaft portion, and is provided between the bottom end of the sliding hole. The piston inserted into the lifter is fixed to the rear end of the valve shaft portion near the rear end of the valve shaft portion while the air pressure chamber is formed in the sliding hole and the sealing member is inserted through the seal member, thereby guiding the valve shaft portion of the engine valve. It is not necessary to provide a portion to be provided above the sleeve, so that the overall height can be reduced, and the length of the valve stem can be shortened to cope with higher rotation.

Further, according to the second feature of the present invention, a communication groove that can communicate between the lifter and the piston on the lifter side with respect to the seal member is formed on the inner surface of the sliding hole so as to be opened to the outside. And avoiding pressurization and decompression of the vacant space generated between the lifters, facilitating the operation of attaching and detaching the lifters to and from the sliding holes, and preventing dance and noise caused by lifting of the lifters. Lubricating oil can also be supplied into the sliding hole.

[Brief description of the drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is an overall vertical sectional side view, FIG. 2 is an enlarged vertical sectional view of a valve shaft sealing member, and FIG. FIG. 4 is an enlarged view of a part III in FIG. 4, FIG. 4 is a view taken along line IV-IV in FIG. 1, and FIG. 5 is a longitudinal sectional side view of the prior art. 1 ... engine body, 5 ... intake valve as engine valve, 5a ...
Valve stem portion, 5b ... valve body portion, 8 ... cam as drive member,
9 Guide hole, 10 Sleeve, 11 Sliding hole, 12
Lifter, 13… Pneumatic chamber, 14… Seal member, 16… Piston, 23… Communication groove

Claims (2)

(57) [Claims] An engine valve having a valve body provided at a tip end of a valve shaft portion is supported by an engine body so as to be openable and closable while being resiliently urged in a valve closing direction. In a valve operating device of an internal combustion engine in which a driving member for driving the engine valve in the valve opening direction is interlocked and connected, a sleeve fixed to the engine body penetrates a valve shaft portion airtightly and movably. A bottomed slide hole having a guide hole at the bottom is provided, and a bottomed cylindrical lifter slidably fitted in the slide hole is interposed between the driving member and the rear end of the valve shaft portion, The piston inserted into the lifter and fixed to the rear end of the valve shaft is fixed near the rear end of the slide hole while forming a pneumatic chamber between the slide hole bottom and the slide hole. A valve train for an internal combustion engine, characterized by: 2. A sliding groove which is formed on the inner surface of the sliding hole so as to be open to the outside on the inner side surface of the sliding hole so as to communicate between the lifter and the piston on the lifter side with respect to the seal member. Item 9. A valve operating device for an internal combustion engine according to claim 7.