JPH0816442B2 - Hydraulic oil supply mechanism for internal combustion engine with hydraulic lifter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic oil supply passage of an internal combustion engine equipped with a hydraulic lifter, and more specifically, to ensure normal operation of the hydraulic lifter when the engine is started. The hydraulic oil supply mechanism.

(Prior Art) In order to save the trouble of valve clearance adjustment and reduce noise during valve operation, an increasing number of internal combustion engines are equipped with a hydraulic lifter that automatically adjusts the valve clearance based on hydraulic pressure in a valve mechanism. .

FIG. 3 shows an example thereof, in which lubricating oil from an oil pump (not shown) driven by the engine is sent to the cylinder head 2 through the passage 7 of the cylinder block 1 and the orifice 13 for adjusting the flow rate. Further, it is supplied to the cam bearing portion 12 via the passages 8 and 9 of the head 2 and the distribution passage 10.

The hydraulic lifter 5 is the intake valve 14 in this DOHC engine example.
(Or the exhaust valve 15) and its drive cam shaft 4 are slidably interposed, and the clearance between the cam 4A and the valve 14 is automatically adjusted by using the lubricating oil from the distribution passage 10 as operating oil. It has a function of transmitting the cam lift to the valve 14 while making zero adjustment.

Specifically, the structure of the hydraulic lifter 5 is as illustrated in FIG. 4, and a cylindrical main body 5A having a tappet surface whose top contacts the cam, and a piston inside the main body 5A that contacts the intake / exhaust valve. 5B and 5B are fitted so that they can move relative to each other in the axial direction, and a cylindrical guide is installed inside piston 5B.
5C is slidably fitted. Guide 5C has a through hole in the center
Oil chambers A and B are defined between the main body 5A and the piston 5B through a seat portion 5E having 5D, and the piston 5B is urged in the oil chamber B in the extending direction with respect to the guide 5C. A spring 5F that opens and a check valve 5G that opens and closes the through hole 5D are interposed.

The hydraulic oil enters the main body 5A from the distribution passage 10 through the through hole 5H opened on the side surface of the main body 5A, and further enters the oil chamber A through the groove 5I. The hydraulic oil in the oil chamber A enters the oil chamber B by opening the check valve 5G based on the pressure drop in the oil chamber B when the piston 5B is about to expand. Therefore, if the valve gap is attempted to expand while the intake / exhaust valve drive cam is in the base circle region, the piston 5B extends from the main body 5A, and thus the valve gap is always adjusted to zero.

Also, during the cam lift, the reaction force from the intake / exhaust valve acts on the piston 5B and the hydraulic pressure rises, so the check valve 5G closes and the oil chamber B enters the oil lock state, so the piston 5B keeps its initial position. The cam lift is effectively transmitted to the intake and exhaust valves. (See JP-A-57-159905, etc.) (Problems to be Solved by the Invention) By the way, in such a conventional engine with a hydraulic lifter,
When the engine is stopped, a part of the lubricating oil of the cylinder head 2 falls into the oil pan due to gravity, so that the oil amount of the cylinder head 2 tends to be insufficient at the time of starting, and the hydraulic lifter 5 also functions as the hydraulic lifter 5. Since it is not possible to sufficiently exhibit the above, a phenomenon similar to that in which the valve clearance is increased may occur and abnormal noise may be generated.

Further, when the lubricating oil returns to the oil pan, air invades from each part of the passage and mixes with the lubricating oil, and the lubricating oil with the air still mixed is supplied to the hydraulic lifter 5 at the time of start-up. Since the oil lock in (1) is insufficient and play occurs and the cam lift acts as an impact load, the hydraulic lifter 5 may be significantly damaged.

The present invention has been made in view of these problems, and an object thereof is to ensure stable operation of the hydraulic lifter even when the engine is started.

(Means for Solving Problems) In order to achieve the above object, according to the present invention, in an internal combustion engine including a hydraulic lifter that automatically adjusts a valve clearance based on engine oil pressure, hydraulic oil is supplied to the hydraulic lifter. A check valve that is biased by an elastic force to close the valve when the hydraulic pressure of the engine is actuated is opened in the middle of the passage that opens. With a section,
A back pressure chamber is defined by a side surface of the check valve opposite to the engine hydraulic pressure side surface, and the back pressure chamber is provided only in a passage downstream of the first throttle portion via a second throttle portion. We decided to communicate.

(Operation) When the engine stops, the oil pressure on the upstream side of the check valve decreases rapidly as the operation of the oil pump stops. On the other hand, the hydraulic oil on the downstream side tries to flow backward in the passage due to gravity, and the oil flows to the check valve. Since the pressure is exerted, the check valve is reliably closed based on the pressure difference between the upstream and downstream.

As a result, a certain amount of hydraulic oil on the hydraulic lifter side can be secured even after the engine has stopped, and air can be prevented from entering due to the hydraulic oil falling.Therefore, the hydraulic lifter has its original function from the beginning of engine startup. Demonstrate without.

On the other hand, when the engine is operating, the check valve is opened based on the engine oil pressure acting from the upstream side, so that the working oil (lubricating oil) flows to the downstream side and is supplied to the hydraulic lifter.

At this time, since the hydraulic pressure on the downstream side of the passage is depressurized and introduced into the back pressure chamber of the check valve through the second throttle portion, fluctuations in the hydraulic pressure on the downstream side due to other reasons such as the operation of the hydraulic lifter may occur. Since this back pressure is always lower than the upstream pressure from the oil pump due to the action of the first throttle part, the engine rotation speed is low and the discharge flow rate of the oil pump is low. At this time, or even when the oil pressure changes on the oil pump side, the check valve does not cause hunting, so that the introduction of the hydraulic oil to the hydraulic lifter side is performed reliably and stably.

Next, an embodiment of the present invention will be described with reference to the drawings. Note that the substantially same parts as those in FIG. 4 are designated by the same reference numerals.

(Embodiment) In FIG. 1, reference numeral 17 designates a substantially cylindrical check valve housing which is fitted into a hydraulic oil supply passage 7 opened in an upper deck portion 1A of a cylinder block 1 from the opening (see FIG. 2). , The orifice as the first and second throttle parts inside
A hollow screw 19 having 19A, 19B and a hydraulic oil outlet portion 19C and a piston-shaped check valve 18 are housed and integrated.

The screw 19 is screwed from the upper end side of the housing 17, and defines a back pressure chamber 18A that communicates with the outlet portion 19C via the orifice 19B between the flange portion 19D on the tip end side and the check valve 18. Further, the flange portion 19D supports the reaction force of the spring 20 interposed between the flange portion 19D and the check valve 18 to urge the check valve 18 to close.

The check valve 18 is seated on the seat portion 18B facing the hydraulic oil inlet portion 17A opened at the lower end of the housing 17, and lifts when the engine oil pressure acting from the inlet portion 17A overcomes the tension of the spring 20. The hydraulic oil flow is passed to the through hole 17B opened on the side surface.

This hydraulic oil passes through the gap 21 between the small diameter portion on the outer periphery of the housing 17 and the inner surface of the passage 7, and flows to the outlet portion 19C via the passage opening 17C and the orifice 19A opened on the rear surface side of the screw flange portion 19D. . At this time, the orifice 19A adjusts the flow rate of the working oil to the cylinder head 2 side, that is, the hydraulic lifter 5 (FIG. 2).

When the check valve 18 is open, the orifice 19
Due to the pressure loss at A, there is always a pressure difference between upstream and downstream, that is, the hydraulic pressure acting on the back pressure chamber 18A via the orifice 19B is always smaller than the pressure on the oil pump side. Hunting is reliably prevented. Further, since the hydraulic pressure on the downstream side of the orifice 19A, that is, on the hydraulic lifter side is reduced via the orifice 18B and acts on the back pressure chamber 18A, the check valve is affected by the pressure fluctuation from the hydraulic lifter side.
Eighteen will be eased. This ensures the stable operability of the check valve 18.

Further, the housing 17 and the check valve 18 are provided on the hydraulic tappet 5.
Needless to say, it may be provided anywhere in the hydraulic oil supply passage of the cylinder block 1 as described above.
If it is provided on the upper deck 1A (or the bottom of the cylinder head), the check valve mounting work in the engine assembling process becomes easier. Further, in this embodiment, the preload adjustment of the spring 20 is adjusted according to the tightening amount of the screw 19. Therefore, the adjustment workability is also improved.

(Effect of the Invention) According to the present invention, the amount of hydraulic oil in the hydraulic lifter is secured by suppressing the drop of lubricating oil from the cylinder head after the engine is stopped via the check valve, and air is mixed into the hydraulic oil. The function of the hydraulic lifter can be reliably exerted at the time of starting the engine, so that the noise of the valve operating system does not increase at the time of starting, and further the damage of the hydraulic lifter is prevented. be able to.

Further, since the pressure on the downstream side of the check valve is set to be lower than the pressure on the oil pump side via the first throttle portion, hunting of the check valve can be prevented, and in addition, in the back pressure chamber of the check valve, By applying pressure on the hydraulic lifter side via the second throttle, the check valve can be stably maintained in the open state regardless of pressure fluctuations associated with the operation of the hydraulic lifter, etc. The effect that hydraulic oil can be supplied is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a schematic sectional view of an internal combustion engine for showing the mounting positions of its check valve and the like. FIG. 3 is a schematic sectional view of a conventional internal combustion engine with a hydraulic lifter, and FIG. 4 is a sectional view of an example of the hydraulic lifter. 1 ... Cylinder block, 2 ... Cylinder head, 5 ...
… Hydraulic lifter, 7,8,9 …… Operating oil passage, 17 …… Check valve housing, 18 …… Check valve, 18A …… Back pressure chamber, 19A, 19B ……
Orifice.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Microfilm (JP, U) of the specifications and drawings attached to the application for Japanese Patent Application No. 57-176504 (No. ) Micro-film (JP, U) Practical application Sho 58-78700 (Actual development) which photographed the contents and drawings attached to the application for practical application Sho 49-14056 Micro film (JP, U) of the contents and drawings attached to the application of Sho 59-182603)

Claims (2)

[Claims] 1. In an internal combustion engine equipped with a hydraulic lifter that automatically adjusts a valve clearance based on engine oil pressure, the engine hydraulic pressure is biased by elastic force in the middle of a passage for supplying hydraulic oil to the hydraulic lifter. A non-return valve that opens elastically when actuated is interposed, and a first throttle portion is provided on the downstream side of the non-return valve, and a side surface of the non-return valve on the engine hydraulic pressure side. A back pressure chamber is defined by the opposite side surface of the hydraulic pressure lifter mechanism, and the back pressure chamber is communicated only with a passage downstream of the first throttle portion via the second throttle portion. Hydraulic oil supply mechanism for internal combustion engines. 2. A check valve, a throttle portion, and a back pressure chamber are integrated via a housing, and the housing is fitted to an upper deck portion of an engine cylinder block or a hydraulic oil passage opening opening to the bottom of a cylinder head. The hydraulic oil supply mechanism for an internal combustion engine with a hydraulic lifter according to claim 1, wherein