Variable valve timing mechanism of an internal combustion engine

Abstract

To provide a variable valve train that can improve changeover responsiveness of a changeover pin and includes a novel drive mechanism using an electromagnetic solenoid.SOLUTION: A variable valve train for an internal combustion engine includes: an input arm 3 swinging by being pressed by a cam 1; an output arm 4 for swinging to press a valve; a changeover pin 5 provided to the output arm 4 so as to be displaceable; and a drive device 6 for displacing the changeover pin 5 to a connection position overlapping on a swing locus of the input arm 3 so that the input arm 3 and the output arm 4 are connected and swing integrally. The drive device 6 is configured to includes: an electromagnetic solenoid 30 located on an outside of the output arm 4; a moving piece 31 driven by the electromagnetic solenoid 30 and moving toward a swing center of the output arm 4; and a connection member 32 for connecting a tip part of the moving piece 31 to a rear end of the changeover pin 5 so as to prevent them from dislodging.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a variable valve mechanism for an internal combustion engine.

Background Art

[0002] As one of the switching type variable valve mechanisms for internal combustion engines, as described in Patent Documents 1 and 2, an input arm that is pressed by a cam and swings, an output arm that swings and presses a valve, a switching pin that is displaceably provided on the output arm, a drive device that displaces the switching pin to a connection position on the swing locus of the input arm, a return spring that displaces the switching pin to a non-connection position not on the swing locus of the input arm, and a lost motion spring that brakes the free swing of the input arm when the switching pin is in the unlock position.

[0003] As a drive device for the switching pin, a hydraulic drive device is common. For example, the hydraulic drive device described in Patent Document 1 has an oil passage formed in the cylinder head, and a hydraulic lash adjuster is mounted so as to communicate with the oil passage. The output arm is swingably supported by the hydraulic lash adjuster, and oil is supplied from the hydraulic lash adjuster to an oil pressure chamber in the output arm so that the switching pin is displaced. Such a hydraulic drive device has a problem that it is difficult to improve the switching responsiveness.

[0004] The electromechanical actuator drive device described in Patent Document 2 is configured such that the rear end of the switching pin protrudes outward from the output arm, the electromechanical actuator is mounted outside the output arm, and the rear end of the switching pin is pressed and displaced by a cap provided at the tip of the plunger of the electromechanical actuator. This electromechanical actuator drive device is thought to easily improve switching responsiveness. The cap is provided with a concave surface centered on the pivot axis, so that the rear end of the switching pin does not come off the concave surface when the output arm swings. However, the rear end of the switching pin and the concave surface of the cap slide against each other when swinging. Also, the electromagnetic solenoid moves not only the plunger but also the cap, so the movement speed is slower. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-61287 [Patent Document 2] European Patent Application Publication No. 2050933 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a variable valve timing mechanism including a novel drive mechanism (different from Patent Document 2) using an electromagnetic solenoid, which can improve the switching response of the switching pin. [Means for solving the problem]

[0007] [1] A variable valve timing mechanism for an internal combustion engine, comprising: an input arm (3) that is pressed and oscillated by a cam (1); an output arm (4) that oscillates and presses a valve; a switching pin (5) displaceably provided on the output arm (4); and a drive device (6) that displaces the switching pin (5) to a connecting position on the oscillation trajectory of the input arm (3) so that the input arm (3) and the output arm (4) are connected and oscillate together, The variable valve timing mechanism for an internal combustion engine is characterized in that the drive unit (6) includes an electromagnetic solenoid (30) located outside the output arm (4), a movable element (31) driven by the electromagnetic solenoid (30) to move toward the pivot center of the output arm (4), and a connecting member (32) that connects the tip of the movable element (31) and the rear end of the switching pin (5) to prevent them from coming apart.

[0008] [2] A variable valve timing mechanism for an internal combustion engine, comprising: an input arm (3) that is pressed and oscillated by a cam (1); an output arm (4) that oscillates and presses a valve; a switching pin (5) displaceably provided on the output arm (4); and a drive device (6) that displaces the switching pin (5) to a connecting position on the oscillation trajectory of the input arm (3) so that the input arm (3) and the output arm (4) are connected and oscillate together, The variable valve timing mechanism for an internal combustion engine is characterized in that the drive unit (6) includes an electromagnetic solenoid (30) located outside the output arm (4) and a movable element (31) that is driven by the electromagnetic solenoid (30) to move and press against the rear end of the switching pin (5), and the rear end of the switching pin (5) is made into an arc pad (36) having an arc surface centered on the pivot point of the output arm (4), so that the contact between the movable element (31) and the rear end of the switching pin (5) does not come off when the output arm (4) swings.

[0009] [Effect] These methods improve switching responsiveness because the switching pin is displaced by an electromagnetic solenoid. Also, even if the output arm swings, the switching pin is pressed without coming off. Furthermore, with method [1], the tip of the moving element and the rear end of the switching pin do not slide against each other when the output arm swings, so no wear occurs on them. In addition, with method [2], there is no cap on the electromagnetic solenoid side as in Patent Document 2, so the movement speed is faster, there is no need for a cap to prevent rotation, and the electromagnetic solenoid side is simpler and cheaper, among other advantages. [Effects of the Invention]

[0010] According to the present invention, a variable valve timing mechanism including a novel drive mechanism using an electromagnetic solenoid can be provided, which can improve the switching responsiveness of the switching pin. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows the variable valve timing mechanism of Example 1, where (a) is a perspective view from above and (b) is a perspective view from above after a vertical cross-section. [Figure 2] Figure 2 is a perspective view of the mechanism from below. [Figure 3] Figure 3 shows the operation of the mechanism during coupling, with (a) being a cross-sectional view at the base circle position and (b) being a cross-sectional view at the nose position. [Figure 4] Figure 4 shows the operation of the mechanism when it is not coupled, with (a) being a cross-sectional view when it is in the base circle and (b) being a cross-sectional view when it is in the nose. [Figure 5] Figure 5 shows the variable valve timing mechanism of Example 2, where (a) is a perspective view from above and (b) is a perspective view from below. [Figure 6] Figure 6 shows the operation of the mechanism during coupling, with (a) being a cross-sectional view at the base circle position and (b) being a cross-sectional view at the nose position. [Figure 7] Figure 7 shows the operation of the mechanism when it is not coupled, with (a) being a cross-sectional view when it is in the base circle and (b) being a cross-sectional view when it is in the nose. [Modes for carrying out the invention]

[0012] 1. Input arm The cam contact portion of the input arm may be a slipper or a roller.

[0013] 2. Output arm The pivot point of the output arm is preferably located at the rear end of the output arm for ease of mounting the input arm, but it may also be located in the center of the output arm.

[0014] 3. Connecting member The connecting members may be made of links or springs.

Embodiment

[0015] An embodiment of a variable valve mechanism for an internal combustion engine will be described with reference to the drawings. However, the structure, shape, quantity, etc. of each part to be described are examples, and can be appropriately changed without departing from the gist of the invention. The valve V of the internal combustion engine may be for intake or exhaust. A valve spring S that biases the valve V in the closing direction is attached to the valve V.

[0016] [Embodiment 1] The variable valve mechanism of Embodiment 1 shown in FIGS. 1 to 4 includes a first cam 1 and a second cam 2, an input arm 3 that is pressed by the first cam 1 and swings, an output arm 4 that swings and presses the valve V, a switching pin 5 provided displaceably on the output arm 4, and a drive device 6 that displaces the switching pin 5 to a connection position on the swing locus of the input arm 3 so that the input arm 3 and the output arm 4 are connected and swing integrally, a return spring 7 that displaces the switching pin 5 to a non-connection position not on the swing locus of the input arm 3, a lost motion spring 8 that brakes the free swing of the input arm 3 when the switching pin 5 is in the non-connection position, and an input roller 9 that is pressed by the second cam 2.

[0017] Both the first cam 1 and the second cam 2 are provided on a camshaft 10, and each consists of a base circle and a nose. The nose of the second cam 2 has a lower protrusion height than the nose of the first cam 1.

[0018] The output arm 4 is an outer arm and comprises two side walls 13 that extend in the front-rear direction and are spaced apart from each other in the width direction, a base 14 connecting the rear ends of the two side walls 13, and an action part 15 connecting the lower ends of the tip portions of the two side walls 13, all integrally formed from steel. There is a space between the intermediate portions of the two side walls 13. A hemispherical recess 16 is recessed in the lower surface of the base 14, and the hemispherical recess 16 is slidably fitted into the hemispherical portion of a hydraulic lash adjuster 17 mounted on the cylinder head, thereby supporting the output arm 4 so as to be able to swing around a pivot center C located within the hemispherical portion. The lower surface of the action part 15 is a valve pressing surface.

[0019] The input arm 3 is an inner arm and comprises a plate-shaped arm body 11 disposed between the two side walls 13 of the output arm 4 (in the space), and a slipper 12 provided on the arm body 11. These are integrally formed from steel. The front part of the arm body 11 is pivotably attached to a support part 18 erected on the output arm 4 by a pivot shaft 19, thereby pivotably attaching the input arm 3 to the output arm 4. A recess 21 is formed in the rear part of the arm body 11 into which the tip of the switching pin 5 enters. The upper surface of the slipper 12 is the surface into which the first cam 1 slides.

[0020] The switching pin 5 consists of a large-diameter portion at the front end and a small-diameter portion at the rear end, and each diameter portion is inserted into the large-diameter hole and the small-diameter hole of a pin hole 20 that extends in the forward-backward direction and is provided through the base portion 14 of the output arm 4. The tip of the switching pin 5 can exit the pin hole 20, engage with the swing trajectory of the input arm 3, and enter the recess 21. When the tip of the switching pin 5 retracts into the pin hole 20, the step portion between the large-diameter portion and the small-diameter portion engages with the step portion between the large-diameter hole and the small-diameter hole.

[0021] The drive unit 6 includes an electromagnetic solenoid 30 located outside the output arm 4, a movable element 31 driven by the electromagnetic solenoid 30 to move toward the pivot center C of the output arm 4, and a connecting member 32 that connects the tip of the movable element 31 and the rear end of the switching pin 5 in a manner that prevents them from coming apart. The connecting member 32 consists of a first link 33 fixed to the tip of the movable element 31, which separates to the left and right and extends toward the left and right of the pivot center C, and a second link 34 that is securely connected to the rear end of the switching pin 5, which separates to the left and right and extends toward the extended end of the first link 33, and is pivotally attached to the extended end.

[0022] The return spring 7 is a coil spring that is loosely inserted around the small diameter portion of the switching pin 5 and mounted in a compressed state between the rear end surface of the base 14 and the retainer 22 at the rear end of the switching pin 5.

[0023] The lost motion spring 8 is a coil spring that is mounted in a compressed state between the upper holding portion of the middle section of the input arm 3 and the lower holding portion of the middle section of the output arm 4.

[0024] The input rollers 9 are arranged on the outside of the two side walls 13 of the output arm 4 and are rotatably mounted on a roller shaft 23 that passes through the middle part of the side wall 13 via needle bearings or double roller bearings (not shown).

[0025] The variable valve timing mechanism of Embodiment 1, configured as described above, switches the drive of valve V between high lift and low lift, as will be explained next.

[0026] As shown in Figure 3, when the electromagnetic solenoid 30 of the drive unit 6 is activated, the movable element 31 is moved toward the pivot center C, and the switching pin 5 is pressed via the first link 33 and second link 34 of the connecting member 32, displacing the switching pin 5 to the connected position where it enters the recess 21, the input arm 3 and the output arm 4 are connected and operate as an integrated rocker arm. That is, the first cam 1 presses the input arm 3, causing the input arm 3 and the output arm 4 to swing together and drive the valve V with high lift.

[0027] The electromagnetic solenoid 30 displaces the switching pin 5, improving the switching response. Furthermore, the movable element 31, which moves toward the pivot center C, and the connecting member 32 ensure that the switching pin 5 is pressed without coming loose even when the output arm 4 swings. In addition, since the tip of the movable element 31 and the rear end of the switching pin 5 do not slide against each other when the output arm 4 swings, wear on them does not occur.

[0028] As shown in Figure 4, when the electromagnetic solenoid 30 is stopped and the return spring 7 displaces the switching pin 5 to an unconnected position where it does not interfere with the swing trajectory of the input arm 3, only the output arm 4 operates as a rocker arm. That is, the first cam 1 presses the input arm 3, causing it to swing freely, and the second cam 2 presses the input roller 9, causing the output arm 4 to swing, driving the valve V at a low lift. At this time, the lost motion spring 8 brakes the free swing of the input arm 3.

[0029] [Example 2] The variable valve timing mechanism of Embodiment 2, shown in Figures 5 to 7, differs from Embodiment 1 only in a part of the drive unit 6; otherwise, it is the same as Embodiment 1. The drive unit 6 is the same as Embodiment 1 in that it includes an electromagnetic solenoid 30 and a movable element 31, but the rear end of the switching pin 5 is made of an arc pad 36 having an arc surface centered on the pivot center of the output arm 4, so that the contact between the movable element 31 and the rear end of the switching pin 5 does not come off when the output arm 4 swings. The arc surface may be a partially cylindrical surface or a partially spherical surface, but a partially cylindrical surface is preferable because it makes line contact with the movable element 31, resulting in lower surface pressure and less wear. Note that the movable element 31 does not necessarily have to move toward the pivot center C.

[0030] The variable valve timing mechanism of Embodiment 2, configured as described above, also switches the drive of valve V between high lift and low lift, as will be explained next.

[0031] As shown in Figure 6, when the electromagnetic solenoid 30 of the drive unit 6 is activated, the movable element 31 is moved, and the arc pad 36 is pressed, displacing the switching pin 5 into the recess 21 and into the connecting position, the input arm 3 and the output arm 4 connect and operate as a single rocker arm. That is, the first cam 1 presses the input arm 3, causing the input arm 3 and the output arm 4 to swing together and drive the valve V with high lift.

[0032] The electromagnetic solenoid 30 displaces the switching pin 5, improving the switching response. Furthermore, by making the rear end of the switching pin 5 an arc pad 36 having an arc surface centered on the pivot point of the output arm 4, the switching pin 5 can be pressed without coming off even when the output arm 4 swings.

[0033] As shown in Figure 7, when the electromagnetic solenoid 30 is stopped and the return spring 7 displaces the switching pin 5 to an unconnected position where it does not interfere with the swing trajectory of the input arm 3, only the output arm 4 operates as a rocker arm. That is, the first cam 1 presses the input arm 3, causing it to swing freely, and the second cam 2 presses the input roller 9, causing the output arm 4 to swing, driving the valve V at a low lift. At this time, the lost motion spring 8 brakes the free swing of the input arm 3.

[0034] It should be noted that the present invention is not limited to the embodiments described above, and can be appropriately modified and implemented without departing from the spirit of the invention. (1) Instead of the hydraulic lash adjuster 17, a pivot without a lash adjuster function may be used. (2) The second cam 2 and input roller 9 can be omitted, and the switching pin 5 can be displaced to an unconnected position that does not interfere with the swing trajectory of the input arm 3, so that the output arm 4 does not swing and the valve V does not lift (i.e., remains stationary). (3) In a variable valve timing mechanism for a multi-cylinder internal combustion engine, one electromagnetic solenoid may be shared by multiple cylinders, and the movable elements of each of the multiple cylinders may be driven collectively by the one electromagnetic solenoid. (4) The connecting member 32 in Example 1 may be replaced with a connecting member consisting of a spring whose two ends are connected to the tip of the movable element 31 and the rear end of the switching pin 5. [Explanation of Symbols]

[0035] 1 First Cam 2 Second Cam 3 Input Arms 4 output arms 5 Switching pins 6. Drive unit 11. Arm body 12 Slippers 14 Base 16 Hemispherical recess 17 Hydraulic lash adjusters 19. Oscillating axis 20 pin holes 21 recess 30 Electromagnetic solenoid 31 Mobile 32 Connecting member 33 First Link 34 Second Link 36 Arc Pads C Oscillation center S Valve Spring V-valve

Claims

1. A variable valve timing mechanism for an internal combustion engine, comprising: an input arm (3) that is pressed and oscillated by a cam (1); an output arm (4) that oscillates and presses a valve; a switching pin (5) displaceably provided on the output arm (4); and a drive device (6) that displaces the switching pin (5) to a connecting position on the oscillation trajectory of the input arm (3) so that the input arm (3) and the output arm (4) are connected and oscillate together, The variable valve timing mechanism for an internal combustion engine is characterized in that the drive unit (6) includes an electromagnetic solenoid (30) located outside the output arm (4), a movable element (31) driven by the electromagnetic solenoid (30) to move toward the pivot center of the output arm (4), and a connecting member (32) that connects the tip of the movable element (31) and the rear end of the switching pin (5) to prevent them from coming apart.

2. A variable valve timing mechanism for an internal combustion engine, comprising: an input arm (3) that is pressed and oscillated by a cam (1); an output arm (4) that oscillates and presses a valve; a switching pin (5) displaceably provided on the output arm (4); and a drive device (6) that displaces the switching pin (5) to a connecting position on the oscillation trajectory of the input arm (3) so that the input arm (3) and the output arm (4) are connected and oscillate together, The variable valve timing mechanism for an internal combustion engine is characterized in that the drive unit (6) includes an electromagnetic solenoid (30) located outside the output arm (4) and a movable element (31) that is driven by the electromagnetic solenoid (30) to move and press against the rear end of the switching pin (5), and the rear end of the switching pin (5) is made into an arc pad (36) having an arc surface centered on the pivot point of the output arm (4), so that the contact between the movable element (31) and the rear end of the switching pin (5) does not come off when the output arm (4) swings.

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