JPH0460101A - Valve timing control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain control with high accuracy and smoothness, simplify a structure, improve manufacturing efficiency and cost performance by relatively rotating a rotational body an a cam shaft with relative pressurizing control of each hydraulic lock mechanism to the rotational body. CONSTITUTION:When an engine is under a high load area, for example, an ON signal is output to a solenoid actuator 44 of a switch means 41 to move a spool valve 42 in a right direction against a coil spring 43 and carry out switching of a hydraulic circuit 14. That is, a first through-hole 36 is opened by a valve body 42, while a second through-hole 37 is closed. A second plunger 20 of a second hydraulic lock mechanism 16 proceeds with synthetic force of high hydraulic pressure in a second high pressure chamber 22 and a compression spring and pressurizes a second inclined face 9a at its pressurizing portion. On the other hand, a first plunger 19 of a first hydraulic lock mechanism 15 pressurizes a first inclined face 8a with a small force of the compression spring alone. As a result, a cam shaft is rotated in a normal direction until projections 12, 13 abut against a stopper, and kept at a position where an earlier closing timing is obtained in respect to an intake valve.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a valve timing control device that variably controls the opening and closing timing of intake and exhaust valves of an internal combustion engine in accordance with operating conditions.

2. Description of the Related Art Various conventional valve timing control devices of this type have been provided, such as U.S. Pat. No. 4,535.
, No. 731 is known.

Briefly, a camshaft that controls the opening and closing of intake and exhaust valves has external teeth formed on the outer periphery of its front end.

On the other hand, the outer cylinder, which is placed and supported on the outside of the front end of the camshaft, is equipped with a sprocket on its outer periphery through which the rotational force of the engine is transmitted via a timing chain, and internal teeth are formed on its inner periphery. . A cylindrical gear in which at least one of the teeth on the inner and outer peripheries is helical is meshed between the inner teeth and the outer teeth of the camshaft. By moving the cam 7 shaft in the axial direction using the hydraulic pressure of the hydraulic circuit and the spring force of the compression spring depending on the engine operating condition, the camshaft is rotated relative to the sprocket and the opening/closing timing of the intake and exhaust valves is determined. It is meant to be controlled.

Problems to be Solved by the Invention However, in the conventional valve timing control device, the sprocket and the camshaft are connected by using helical teeth formed on at least one of the inner and outer circumferences of the cylindrical gear. They are designed to rotate relative to each other, and therefore, these helical teeth require highly accurate machining to ensure good meshing accuracy with the internal teeth of the sprocket or the external teeth of the camshaft. As a result, the machining operation of the helical teeth becomes complicated, resulting in a decrease in machining efficiency and a rise in machining cost.

In addition, since the cylindrical gear is moved in the axial direction of the camshaft, the length of the entire device inevitably becomes long, which necessitates an increase in size.

Means for Solving the Problems The present invention was devised in view of the above-mentioned conventional situation, and
In particular, a pair of hydraulic lock mechanisms are provided at the end of the cam 7 shaft facing inside the rotating body to regulate the relative rotational position of the rotating body and the camshaft, and hydraulic pressure is supplied relatively to each hydraulic lock mechanism. The engine is characterized by comprising a hydraulic circuit for discharging water, and a switching means for switching the flow path of the hydraulic circuit depending on the engine operating state.

Function: For example, in a low engine load range, the switching means switches the hydraulic circuit to supply hydraulic pressure to the first hydraulic lock mechanism and at the same time drain the oil in the second hydraulic lock mechanism. Therefore, while the first hydraulic locking mechanism advances toward the rotating body and presses the rotating body, the second hydraulic locking mechanism is not pressed against the rotating body. At this point, when positive rotational torque is applied to the camshaft by the driving force of the engine, the first hydraulic lock mechanism is activated via the rotating body.
The hydraulic lock mechanism of the camshaft is strongly pressed against the force that tries to push it back in the backward direction, thereby restricting the forward rotation of the camshaft. This restricts relative rotation between the rotating body and the camshaft, and holds the camshaft in a rotational position that delays the closing timing of the intake valve, for example.

On the other hand, when the engine shifts to a high load range, the switching means switches the hydraulic circuit in the opposite direction to the above, supplying hydraulic pressure only to the second hydraulic lock mechanism, and draining the hydraulic pressure in the first hydraulic lock mechanism. let Therefore, while the second hydraulic lock mechanism presses the rotating body, the first hydraulic lock mechanism is not pressed against the rotating body. Therefore, when the camshaft is allowed to rotate in the positive direction and receives a negative rotational torque when it reaches the maximum rotational position in the positive direction,
This time, the second hydraulic lock mechanism strongly presses the rotating body using hydraulic pressure to restrict rotation of the camshaft in the negative direction. This holds the camshaft in a rotational position that advances the closing timing of the intake valve.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Figures 1 and 2 show an embodiment of the present invention applied to a DOHC internal combustion engine for an automobile, in which 1 is a camshaft supported by a cam bearing 2 at the top of the cylinder head to open and close the intake valve; A driven sprocket, which is a rotating body, is disposed on one end la side of the camshaft 1 and transmits rotational force via a timing chain from a drive sprocket attached to a crankshaft (not shown); 4 is the inside of the driven sprocket 3; The body 4 has a stepped through hole 4a drilled in the solid axial direction and a bolt hole 1b drilled in the axial direction at one end la of the camshaft 1. and the mounting port 5 inserted respectively.
is fixed to one end 1a of the camshaft.

The driven sprocket 3 includes a main body 6 in the shape of a covered cylinder;
A cylinder formed in the center of the other end wall 6a of the main body 6, consisting of two sets of gears 7a integrally provided on the outer peripheral surface of the main body 6, and a circular end plate 7b that closes an opening at one end of the main body 6. Part 6b
It is rotatably supported on the camshaft 1 via the camshaft 1.

Further, a third
As shown in the figure, a pair of substantially wedge-shaped protrusions 8 and 9 extend along the circumferential direction. The upper surfaces of the protrusions 8 and 9 are provided with first inclines curved in opposite directions along the circumferential direction.
．． Second inclined surfaces 8a and 9a are formed. That is,
The first inclined surface 8a on the upper side and the second inclined surface 9a on the lower side in FIG.
are inclined at a predetermined angle so as to become gradually lower from the right to the left in the figure. In addition, the main body 6
On the other end wall 6a, as shown in FIG.
...is installed protrudingly.

The body 4 has a cylindrical convex portion 12.13 extending along the diameter direction on the outer periphery corresponding to each of the inclined surfaces 8a, 9a, and a pair of storage portions in each of the image portions 12.13. Holes 12a and 13a are bored along the axial direction. Moreover, each storage hole 12a.

A hydraulic lock mechanism 15, 16 operated by the hydraulic pressure of the hydraulic circuit 14 is arranged at 13a.

As shown in FIG. 4, this hydraulic locking mechanism 1.5.16 includes a substantially cylindrical retainer 1.7.18 press-fitted into the bottom of the storage holes 12a and 13a, and a retainer 17.18.
The first . Second inclined surface 8
a, the first one that moves forward and backward with respect to 9a. Second plunger1.
9.20, the plunger 19.20 and the retainer 17,
18 upper surface. Second hyperbaric chamber 21.
22. The retainers 17, 18 are formed with communicating passages 23 and 24 that communicate the later-described supply passage 35 of the hydraulic circuit 14 and the high pressure chambers 21, 22 in the internal axial direction. Said 1st. The second plunger 19, 20 has a cylindrical shape with a lid, and has spherical pressing portions 19a, 20a formed at its tip to appropriately press the respective inclined surfaces 8a, 9a, and has high pressure chambers 21, 22 and an outer periphery formed on the peripheral wall. Small holes 27.28 are drilled along the radial direction to communicate with the discharge grooves 25.26 in the walls, and small spring forces of compression springs 29.30 elastically loaded in the high pressure chambers 21, 22 are used. is biased in the advancing direction (in the direction of each inclined surface 8a, 9a). Further, in the high pressure chambers 21 and 22, the communication passage 23.
Check valves 3] and 32 are provided to allow the hydraulic pressure in 24 to flow only into the high pressure chambers 2], 22.

As shown in FIGS. 1 and 2, the hydraulic circuit 14 branches from an oil main gear rally (not shown) and is formed to penetrate the cam bearing 2 and the camshaft 1 in the radial direction, and receives pressure from the upstream oil pump 33. A main passage 34 through which oil is pumped is formed between the bolt hole 1b of the camshaft 1 and the mounting port 5, -1J is connected to the main passage 34, and the other end is connected to the communication path 23.2.
An annular supply passage 35 connected to the body 4 and the body 4 respectively.
The first and second holes are bent in an abbreviated shape inside the body, and one end is formed in each of the discharge grooves 25 and 26, and the other end is formed in the front and rear positions on the head 5a side of the mounting port 5 along the radial direction. Through hole 36
．． 37 and a discharge passage 38, 39 formed in the internal axial direction of the head 5a and connected to the first. Each downstream end of the second through hole 36,37 is provided with an open control hole 40. The control hole 40 has an enlarged opening end 40 a that communicates with the outside through the inside of the driven sprocket 3 . Further, the hydraulic circuit 14 is configured such that the flow path on the discharge side is appropriately switched and controlled by the switching means 41.

The switching means 41 includes a spool valve 42 that is slidably housed in the control hole 40 in the axial direction, and an electromagnetic actuator that moves the spool valve 42 to the right in the figure against the spring force of a coil spring 43. It consists of 44.

The spool valve 42 is connected to the control hole 4 depending on the sliding position.
0 and the first through hole 36 or the second through hole 37. 1st
It is provided with a substantially T-shaped communication hole 42b that communicates with the communication hole 36 or the second communication hole 37 as appropriate.

Further, the electromagnetic actuator 44 is connected to the rocker cover 4.
5, the tip of the drive rod 44a presses or separates the tip of the valve body 42a of the spool valve 42, and is activated by an ON-OFF signal from a controller equipped with a microcomputer (not shown). is controlled.

This controller detects the current engine operating state based on the engine rotational speed signal from the crank angle sensor, the intake air amount signal from the air flow meter, etc., and outputs a control signal to the electromagnetic actuator 44.

The operation of this embodiment will be explained below. First, for example, in a low engine load range, an OFF signal is output to the electromagnetic actuator 44, so that the spool valve 42 is held at the left position shown in FIG. 1 by the spring force of the coil spring 43.
At the same time as the valve body 42a opens the second passage hole 37, it closes the first passage hole 36, that is, communicates the second high pressure chamber 22 with the outside, and blocks communication between the second high pressure chamber 21 and the outside. do.

Therefore, the oil pump 33 moves the main passage 34 to the supply passage 35. Each communication path 23, 24. cheek valve 3
1.32 to both the first and second high pressure chambers 21.22 remains only in the first high pressure chamber 21. That is, the pressure oil that has flowed into the second high pressure chamber 22 flows through the small hole 28.
．． Discharge groove 26° discharge passage 39. Second through hole 37. control hole 4
0. Since it is discharged to the outside through the communication hole 42b, the second
In the plunger 20, the pressing part 20a presses the second inclined surface 9a only by the small spring force of the compression spring 30, while the first plunger 19 presses the second inclined surface 9a by the combined force of the compression spring 29 and the high oil pressure in the first high pressure chamber 21. The pressing part 19a advances from the storage hole 12a and presses the lower part of the first inclined surface 8a. Therefore, at this point, when a clockwise rotational force (positive rotational torque) in FIG. 3 acts on the camshaft 1, the first plunger 19 receives a force in the backward direction from the first inclined surface 8a. The resultant force strongly presses the first inclined surface 8a to prevent further rotation of the camshaft 1 in the forward direction (forward rotation). Meanwhile, at the same time, each convex portion 12.13 of the body 4 corresponds to the stopper 1. It hits Lll and prevents negative rotation (reverse rotation). Therefore, the relative rotational position between the camshaft 11 and the sprocket 3 is reliably regulated to the position shown in FIG. 3, and the camshaft 1 is held at a rotational position where the closing timing of the intake valve is delayed.

On the other hand, when the engine shifts to a high load range, an ON signal is output to the electromagnetic actuator 44, and therefore it moves to the right against the spring force of the spool valve 42 or coil spring 43 to switch the hydraulic circuit 14. . That is, the first through hole 36 is opened by the valve body 42a, and the second through hole 37 is closed at the same time. Therefore, the second plunger 20 advances with the combined force of the high oil pressure in the second high pressure chamber 22 and the compression spring 30 and presses the second inclined surface 9a with the suppressing part 20a, while the first plunger 19 The inclined surface 8a is pressed only by the small spring force of the compression spring 29. Therefore, if a positive rotational torque is generated on the cam shirt l-] at this point, the camshaft 1 rotates in the positive direction until the convex portion 12.13 abuts against the stoppers 10, 10 (Fig. 3 - dotted chain line position) . In this state, even if the camshaft 1 receives a negative rotational torque in the counterclockwise direction in FIG. 3 due to the reaction force of the valve spring after the cam lifts the intake valve to the maximum, the second plunger 2
0 strongly presses the lower part of the second inclined surface 9a with the resultant force to prevent the camshaft 1 from rotating in the negative direction (reverse rotation). On the other hand, at the same time, the stopper 10.10 prevents the camshaft 1 from rotating in the forward direction. Therefore, the relative rotational position between the camshaft 1 and the sprocket 3 is reliably regulated to the position indicated by the dashed-dotted line in FIG. 3, and the camshaft 1 is held at the rotational position where the closing timing of the intake valve is early.

In addition, when the engine shifts from a high load area to a low load area, the effect will be in the low load area as described above, and after the camshaft l rotates to the maximum in the negative direction, which is regulated by the stopper 11.11,
] The pressing force of the plunger 19 reliably prevents rotation in the forward direction.

The present invention is not limited to the embodiment described above, and, for example, the switching mechanism can be configured differently. Further, in this embodiment, an example in which the present device is applied to the intake valve side has been described, but it is also possible to apply the present device to the exhaust valve side.

Effects of the Invention As is clear from the explanation below, according to the present invention, the relative rotation between the rotating body and the camshaft is controlled not by the conventional cylindrical gear, but by the relative rotation of each hydraulic lock mechanism with respect to the rotating body. Since this is done through pressure control, not only high precision and smooth control can be obtained, but also the structure is simplified as no helical teeth are required, improving manufacturing efficiency and reducing costs. I can figure it out.

Furthermore, since the cylindrical gear that moves in the axial direction is eliminated, the length of the entire device can be shortened, and the device can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a valve timing control device according to the present invention, FIG. 2 is a cross-sectional view of the device showing the operation of this embodiment, and FIG.
The figure is a sectional view taken along line I-] in FIG. 1, and FIG. 4 is an enlarged view of section A in FIG. 3. 1... Camshaft, 3... Driven sprocket (rotating body), 4... Body, 14... Hydraulic circuit, 1
516...1st. Second hydraulic lock mechanism, 41... switching means. Figure 3 Figure 4

Claims (1)

[Claims] (1) Control the opening/closing timing of intake and exhaust valves by relatively rotating the internal hollow rotary body to which engine drive is transmitted and the camshaft using positive and negative rotational torque fluctuations of the camshaft. The valve timing control device includes a pair of hydraulic lock mechanisms provided at an end of the camshaft facing inside the rotating body to regulate the relative rotational position of the rotating body and the camshaft, and a pair of hydraulic lock mechanisms for each of the hydraulic lock mechanisms. 1. A valve timing control device for an internal combustion engine, comprising: a hydraulic circuit that relatively supplies and discharges hydraulic pressure; and switching means that switches a flow path of the hydraulic circuit according to engine operating conditions.