JPH06299832A - Variable valve timing mechanism - Google Patents

Abstract

(57) [Summary] [Purpose] To lubricate the sliding parts of the lost motion assembly when the rocker arm and rocker shaft of the variable valve timing mechanism are released. A lost motion assembly 25 that pushes the rocker arm against a cam 15 when the rocker arm of the variable valve timing mechanism that connects or disconnects the rocker shaft and the rocker arm 7 that swings around the rocker shaft by hydraulic pressure is released. Of the lost motion piston 27, the tip 27a of the lost motion piston 27 is pressed against the contact portion of the rocker arm from above, and an oil passage 35d for supplying oil to the mounting portion 35 of the lost motion assembly is provided. Is provided to the sliding portion between the lost motion cylinder 26 and the lost motion piston 27, and the oil that can flow down to the tip 27a of the lost motion piston is supplied to the sliding portion between the tip and the rocker arm. is there .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing mechanism, and more particularly to a lubrication structure in a sliding portion between a lost motion assembly and a rocker arm.

[0002]

2. Description of the Related Art In a variable valve timing mechanism, two types of cams for low speed and high speed, which have different profiles, are set on a camshaft. It is a mechanism that switches using a hydraulic pressure so as to drive a valve. The low speed cam is smaller than the high speed cam, and both valve overlap and lift are smaller.

By adopting a variable valve timing mechanism,
It is possible to improve the output torque of the engine in the high speed range while maintaining the low speed and high torque of the practical engine in the low speed range. Various variable valve timing mechanisms have been proposed. Thus, in the valve operating mechanism that connects or disconnects the shaft and the rocker arm that swings around the shaft by hydraulic pressure, when the rocker arm does not work with the valve, for example, the low speed cam drives the low speed rocker arm to operate the valve. When this is done, as shown in FIG. 8, a high speed rocker arm 43, in which the piston 42 is retracted from the rocker shaft 41 and is disengaged from the rocker shaft 41, is interposed between the rocker arm 43 and the cylinder head 50 as shown in FIG. The lost motion assembly 45 presses the roller bearing 44 of the high speed rocker arm 41 at all times.

In this case, the lost motion assembly 45
The sliding motion of the lost motion cylinder 46, the lost motion piston 47, the tip 47a of the lost motion piston 47, and the claw 43a of the rocker arm 43 are lubricated only by the oil in the atmosphere in the cylinder head 50. Very unforgiving. Therefore, if the lost motion assembly 45 is seized, there is a risk that the variable valve timing mechanism may not stop operating but may also stop the engine.

[0005]

As a countermeasure against this, FIG.
As shown in Fig. 5, an oil passage 50a is provided in the cylinder head 50, and the lost motion assembly 4 is installed in the oil passage 50a.
Oil is supplied by communicating the hole 46a provided in the lost motion cylinder 46 of No. 5 with the lost motion cylinder 46.
It has been proposed to lubricate the sliding portion between 46 and the lost motion piston 47 so as to prevent seizure of the lost motion assembly 45.

However, as described above, the oil passage 50a
However, it is difficult to lubricate the sliding portion between the claw 43a of the rocker arm 43 and the tip 47a of the lost motion piston 47. The present invention has been made in view of the above points, and is a variable valve timing mechanism that is configured to lubricate the sliding portions of the lost motion piston, the lost motion cylinder, and the rocker arm at the same time when the rocker arm of the variable valve timing mechanism is released. An object is to provide a valve timing mechanism.

[0007]

To achieve the above object, according to the present invention, the rocker arm of a variable valve timing mechanism for connecting or disconnecting a rocker shaft and a rocker arm swinging around the rocker shaft by hydraulic pressure is used. A lost motion assembly that presses the rocker arm against a cam when the lock motion is released, and the tip of the lost motion piston is pressed against the contact portion of the rocker arm from above, and the lost motion assembly is An oil passage for supplying oil to the mounting portion of the lost motion assembly is provided, an oil passage for supplying the oil to the sliding portion between the lost motion cylinder and the lost motion piston is provided in the lost motion assembly, and the oil flows down to the tip of the lost motion piston. The oil to It is obtained by the supply arrangement to the sliding portion between the rocker arm and.

[0008]

The oil discharged from the oil pump during engine operation is supplied to the mounting portion of the lost motion assembly through the oil passage. This oil is supplied to a sliding portion between the lost motion cylinder and the lost motion piston through an oil passage provided in the lost motion assembly to lubricate between them, and then flows down to the tip of the lost motion piston. It is supplied to the sliding surface between the tip and the rocker arm and lubricates between them.
This ensures good lubrication of the sliding portion between the rocker arm and the lost motion assembly when the rocker arm is not interlocked with the valve.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 and 2, the variable valve timing mechanism 1 includes two valves, for example, exhaust valves 2 and 3.
And a T-type rocker arm 5 integrated with the rocker shafts 4 and 4'for opening and closing these valves 2 and 3, a low-speed rocker arm 6, a high-speed rocker arm 7, and a T-type rocker arm 5 which are built in the T-type rocker arm 5. The rocker arm 5 includes pistons 8 and 9 for selectively connecting the low speed rocker arm 6 or the high speed rocker arm 7 and a low speed cam 14 and a high speed cam 15 provided on the camshaft 13.

Rocker shafts 4 and 4'at both ends of the T-shaped rocker arm 5 are rotatably supported by rocker shaft journals 12 and 12 ', and an oil passage 4'provided in the journal 12' and shaft 4 '. The hydraulic pressure P is supplied to the piston 8 through a, and the hydraulic pressure P is supplied to the piston 9 through the journal 12 and the oil passage 4a of the shaft 4. The low speed rocker arm 6 and the high speed rocker arm 7 have shaft holes 6a and 7a at the base ends thereof.
Rocker shafts on both sides of each T-shaped rocker arm 5
4'and 4 are fitted and pivotally supported, and roller bearings 10 and 11 are pivotally supported at the respective tips. These roller bearings 10 and 11 are brought into contact with the low speed cam 14 and the high speed cam 15, respectively, and roll. The low-speed rocker arm 6 and the high-speed rocker arm 7 are not interlocked with the valves 2 and 3, that is, when the connection with the T-shaped rocker arm 5 is released, the lost motion assembly 25 'disposed on each base end side. , 25 (Fig. 3) by roller bearings 10, 11
Is brought into contact with the low speed cam 14 and the high speed cam 15.

The rocker shaft 4'of the T-shaped rocker arm 5,
Piston holes 4'b and 4b are bored in the diametrical direction in the respective fitting portions for fitting the low speed rocker arm 6 and the high speed rocker arm 7 of 4, as shown in FIG.
4'b, 4b to the piston 8, via the spring 17 ', 17
9 is stored. This variable valve timing mechanism 1
Are supported by the cylinder head 33 of the cylinder head assembly 30 as shown in FIGS. A camshaft holder 34 and a cam cap 35 are placed and fixed on the cylinder head 33, and a rocker shaft cap 36 is fixed on the lower surface center of the camshaft holder 34. Camshaft journals 37, 37 are provided on the left and right sides between the camshaft holder 34 and the cam cap 35, and the rocker shaft journals 12 are provided on the left and right sides between the camshaft holder 34 and the rocker shaft cap 36. , 12 are provided.

Then, for example, the camshaft and rocker shaft of the exhaust side variable valve timing mechanism are provided on the left camshaft journal 37 and the rocker shaft journal 12, and the intake side variable valve timing mechanism is provided on the right side camshaft journal 37. The cam shaft and the rocker shaft of are supported. The camshaft journal 37
The camshaft holder 34 and the cam cap 35 are formed by journals 34a and 35a having a semicircular cross section, respectively, and are formed on one side, for example, in the center of the bottom surface of the left journal 34a along the circumferential direction. Oil passage 34 with a semicircular cross section
b is provided. Furthermore, this camshaft holder 34
An oil passage 34c having one end opened near the outer end of the bottom surface of the oil passage 34b and the other end opened on the lower surface is vertically formed.

A left side wall 33a of the cylinder head 33 is also provided.
An oil passage 33b is provided substantially horizontally on the upper part of
The oil passage 33b and the oil passage 34c of the camshaft holder 34 are provided substantially perpendicular to the side wall 33a, one end of which opens into the oil passage 33a, and the other end of which communicates with the oil passage 34c. Has been done. The oil passage 33b is connected to an oil pump (not shown).

On the other hand, in the center of each cam cap 35 (FIG. 3), holes 35a, 35 for mounting the lost motion assembly are provided.
a, 35b, 35b are drilled vertically. Incidentally, the hole 35a,
The lost motion assembly of the variable valve timing mechanism on the exhaust side is attached to 35a, and the intake side variable valve timing mechanism is attached to the holes 35b and 35b. At the center of the lower surface of the cam cap 35, crosswise oil passages 35c, 35d are provided in the left-right direction and the longitudinal direction. The oil passage 35c has one end communicating with the inner end of the oil passage 34c of the left journal 34a and the other end opening to the inner peripheral surface of the right camshaft journal 37. Further, the oil passage 35d has both ends at the respective holes 35a.
, 35a, 35b, 35b are open to the inner surface.

As shown in FIG. 6, the lost motion assembly 25 includes a lost motion cylinder 26 and a lost motion piston fitted in the cylinder 26 such that the lost motion cylinder 26 can be inserted and removed.
27 and a lost motion spring 28 compressed between the lost motion cylinder 26 and the lost motion piston 27. A large-diameter breathing hole 26a is formed in the end surface of the lost motion cylinder 26, and an annular groove 26b (Fig. 7) provided in the inner peripheral surface of the opening end is provided to prevent the lost motion piston 27 from projecting. Stopper ring 29 is fitted. And, an annular groove 26c is provided along the circumferential direction at substantially the center of the outer peripheral surface,
A hole 26d is formed in the bottom surface of the annular groove 26c.

On the other hand, the tip of the lost motion piston 27
27a has a substantially frustoconical shape, and a screw hole 27b with a bottom is provided at the center of the inner surface of the tip 27a. The screw hole 27b is for screwing a piston lifting jig. An annular groove 27c is provided in the upper portion of the outer peripheral surface of the lost motion piston 27 along the circumferential direction, and the annular groove 27c is the lost motion piston.
When 27 is pushed out by the lost motion spring 28 as shown in the figure and is locked to the stopping ring 29, it can be communicated with the hole 26d of the lost motion cylinder 26.

The lost motion assembly 25 is fitted in the hole 35a of the cam cap 35 with the lost motion piston 27 facing downward as shown in FIG. In this state, the annular groove 26c on the outer peripheral surface of the lost motion cylinder 26 is communicated with the tip of the oil passage 35d, and the tip 27a of the lost motion piston 27 is attached to the high speed rocker arm 7.
The upper surface of the claw 7d is pressed by the spring force of the spring 28.
As a result, when the high-speed rocker arm 7 is disconnected from the T-type rocker arm 5, the roller bearing 11 at the tip thereof is pressed against the high-speed cam 15.

Similarly, the lost motion assembly 25 'of the low speed rocker arm 6 has a hole 35 in the adjacent cam cap 35.
It is attached to a. Also, each lost motion assembly of the intake side variable valve timing mechanism is attached to the cam cap 35 in the same manner as each lost motion assembly 25, 25 ′ of the exhaust side variable valve timing mechanism. The operation will be described below.

In the low speed rotation range of the engine, a low pressure oil pressure is supplied to the oil passage 4'a (FIG. 2) of the rocker shaft 4 ', and the piston 8 causes the piston hole 4 by the spring force of the spring 17'. The tip 8a is pushed out from the'b and is fitted into the piston hole 6b of the low pressure rocker arm 6. As a result, the low-speed rocker arm 6 is coupled to the T-type rocker arm 5 to be integrated, and the valves 2 and 3 are driven by the low-speed cam 14 via the low-speed rocker arm 6 and the T-type rocker arm 5.

On the other hand, low-pressure hydraulic pressure is also supplied to the oil passage 4a of the high-speed rocker arm 4, and the piston 9 is retracted by the spring force of the spring 17 and drawn into the piston hole 4b as shown in FIG. ing. As a result, the high-speed rocker arm 7 is released from the connection with the T-shaped rocker arm 5 and can freely swing. At this time, the roller 11 of the high-speed rocker arm 7 has the lost motion assembly.
25 makes contact with the high speed cam 15 and rolls. When the engine enters the high speed rotation range, high pressure oil pressure is supplied to the oil passage 4a (Fig. 2) of the rocker shaft 4, and the piston 9 resists the spring force of the spring 17 from the piston hole 4b as shown in Fig. 5. It is pushed out and its tip fits into the piston hole 7b of the high speed rocker arm 7. And the rocker arm 7 for high speed is T
Type rocker arm 5 is integrated and integrated with a high speed cam
The valves 2 and 3 are driven by 15 via the high-speed rocker arm 7 and the T-shaped rocker arm 5.

By the way, when the engine is running, the oil passage 33 of the cylinder head 33 shown in FIG.
The oil supplied to b is supplied to the oil passage 34b through the oil passages 33c and 34c to lubricate the sliding surface between the left camshaft 13 and the camshaft journal 37, and
Lubricate the sliding surface between the right camshaft and the camshaft journal 37 through the oil passage 35c. Further, the oil is supplied to the oil passages 35c to 35d, and the holes 35a, 35a, 35b, 35
Supplied to b. The oil supplied to the hole 35a is the annular groove 26 on the outer peripheral surface of the lost motion cylinder 26 shown in FIG.
c, through the hole 26d, into the lost motion cylinder 26, and further through the annular groove 27 of the lost motion piston 27.
It flows into c and lubricates the sliding surface between them.

Further, the oil lubricated between the lost motion cylinder 26 and the lost motion piston 27 flows down along the outer peripheral surface of the lost motion piston 27 and slides between the tip 27a and the claw 7d of the high speed rocker arm 7. It is supplied to the moving surface and lubricates between them. This results in the lost motion piston of the lost motion assembly 25.
27, lost motion cylinder 26, rocker arm 7 claw
Each sliding part with 7d is lubricated at the same time. As a result, when the high-speed rocker arm 7 is disengaged from the T-type rocker arm 5 and does not interlock with the valve, the sliding portion between the high-speed rocker arm 7 and the lost motion assembly 25 is satisfactorily lubricated.

The low-speed rocker arm 6 (FIG. 1) of the variable valve timing mechanism 1 and the variable valve timing mechanism on the intake side (not shown) are the same as above in the lost motion piston, the lost motion cylinder, and the rocker arm. The sliding parts of are lubricated.

[0024]

As described above, according to the present invention, when the rocker arm of the variable valve timing mechanism for connecting or disconnecting the rocker shaft and the rocker arm swinging around the rocker shaft by hydraulic pressure is released. Lost motion assembly for pressing the rocker arm to the cam, is arranged above the rocker arm to press the tip of the lost motion piston from above to the contact portion of the rocker arm, and to attach oil to the mounting portion of the lost motion assembly. An oil passage for supplying the oil is provided, the lost motion assembly is provided with an oil passage for supplying the oil to a sliding portion between the lost motion cylinder and the lost motion piston, and the oil which can flow down to the tip of the lost motion piston is provided. The rocker arm By supplying to the sliding parts of, the sliding parts of the lost motion piston, the lost motion cylinder, and the rocker arm of the lost motion assembly can be lubricated at the same time, and seizure of these sliding parts can be prevented. The reliability of the variable valve timing mechanism can be improved. Further, there is an effect that the structure is simple without requiring a special part for lubrication.

[Brief description of drawings]

FIG. 1 is an assembled perspective view showing an embodiment of a variable valve timing mechanism to which the present invention is applied.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a plan view of a cylinder head incorporating the variable valve timing mechanism of FIG.

FIG. 4 is a sectional view taken along the line IV-IV in FIG.

5 is a cross-sectional view taken along the line VV of FIG.

6 is an enlarged view of the lost motion assembly of FIG.

FIG. 7 is an enlarged view of a main part of FIG.

FIG. 8 is a cross-sectional view of essential parts showing a first example of a conventional variable valve timing mechanism.

FIG. 9 is a sectional view of an essential part showing a second example of a conventional variable valve timing mechanism.

[Explanation of symbols]

 1 Variable valve timing mechanism 2, 3 Exhaust valve 4, 4'Rocker shaft 4a, 4'a Oil passage 4b, 4'b, 6b, 7b Piston hole 5 T-type rocker arm 6 Low-speed rocker arm 7 High-speed rocker arm 8, 9 Piston 10, 11 Roller bearing 13 Cam shaft 14 Low speed cam 15 High speed cam 25 Lost motion assembly 26 Lost motion cylinder 27 Lost motion piston 30 Cylinder head assembly 33 Cylinder head 34 Cam shaft holder 35 Cam cap 36 Rocker shaft cap

Claims (1)

[Claims] 1. A lost motion assembly for pressing a rocker arm against a cam when the rocker arm of a variable valve timing mechanism for connecting or disconnecting a rocker shaft and a rocker arm swinging around the rocker shaft by hydraulic pressure is released. The lost motion assembly is provided above the rocker arm so that the tip of the lost motion piston is pressed against the contact portion of the rocker arm from above, and an oil passage for supplying oil to the mounting portion of the lost motion assembly is provided. Is provided with an oil passage for supplying the oil to the sliding portion between the lost motion cylinder and the lost motion piston, and the oil that can flow down to the tip of the lost motion piston is supplied to the sliding portion between the tip and the rocker arm. Characterized by Variable valve timing mechanism.