VARIABLE VALVE MECHANISM OF INTERNAL COMBUSTION ENGINE

Abstract

 A variable valve mechanism of an internal combustion engine includes an input arm, an output arm, a lock pin, a drive device and a return spring of the lock pin, and a lost motion spring of the input arm. The input arm has in its rear end portion a pushback surface and a stopped surface. The lock pin has in its distal end portion a pushed-back surface and a stopping surface. The drive device includes a driving source and a mover that moves to push the lock pin when driven by the driving source. A driving force of the driving source is set so as to be smaller than a force with which the pushback surface pushes back the pushed-back surface as the lost motion spring causes the input arm to freely swing upward and be larger than load with which the return spring displaces the lock pin.

Description

TECHNICAL FIELD

[0001] The present invention relates to variable valve mechanisms of internal combustion engines.

BACKGROUND ART

[0002] Variable valve mechanisms as described in Patent Document 1 and Patent Document 2 are known as one type of switchable variable valve mechanism of an internal combustion engine. Such variable valve mechanisms include: an input arm that swings when pressed by a cam; an output arm that swings to push a valve; a lock pin displaceably placed in the output arm; a drive device that displaces the lock pin to a lock position where the lock pin is located in a path of a free swinging motion of the input arm; a return spring that displaces the lock pin to an unlock position where the lock pin is not located in the path of the free swinging motion of the input arm; and a lost motion spring that brakes the freely swinging input arm when the lock pin is located in the unlock position. Controlling the switch timing has been found effective in improving switching response of such switchable variable valve mechanisms.

[0003] A hydraulic drive device is commonly used as the drive device for the lock pin. For example, in a hydraulic drive device described in Patent Document 1, an oil passage is formed in a cylinder head, and a hydraulic lash adjuster is mounted so as to communicate with the oil passage. An output arm is swingably supported by the hydraulic lash adjuster, and oil is supplied through the hydraulic lash adjuster into a hydraulic chamber in the output arm to displace the lock pin. In multi-cylinder internal combustion engines, oil passages in a cylinder head are shared by all the cylinders. It is therefore difficult to control the switch timing with such a hydraulic drive device.

[0004] As a solution to this problem, it has been proposed to mount a drive device having electromagnetic solenoids for each cylinder. For example, in a drive device using an electromagnetic solenoid, which is described in Patent Document 2, a lock pin is placed such that its one end protrudes to the outside from an output arm, and an electromagnetic solenoid is mounted outside the output arm. The lock pin is displaced when the one end of the lock pin is pushed by the electromagnetic solenoid. The drive device having electromagnetic solenoids for each cylinder is disadvantageous in terms of cost.

CITATION LIST

Patent Document

[0005] 

Patent Document 1: Japanese Patent Application Publication No. 2016-61287 (JP 2016-61287 A)

Patent Document 2: European Patent Application Publication No. 2050933 (EP 2050933 A)

SUMMARY OF INVENTION

Technical Problem

[0006] It is an object of the present invention to make it easy to control the switch timing by reliably switching valve operation in a base circle phase by using a free swinging motion of an input arm.

Solution to Problem

[0007] According to the present invention, a variable valve mechanism of an internal combustion engine including an input arm that swings when pushed by a cam, an output arm that swings to push a valve, a lock pin displaceably placed in the output arm, a drive device that displaces the lock pin to a lock position where the lock pin is located in a path of a free swinging motion of the input arm, a return spring that displaces the lock pin to an unlock position where the lock pin is not located in the path of the free swinging motion of the input arm, and a lost motion spring that brakes the freely swinging input arm when the lock pin is in the unlock position, is characterized in that the input arm has in its rear end portion a pushback surface facing upward and a stopped surface located below the pushback surface and facing downward, the lock pin has in its distal end portion a pushed-back surface facing obliquely downward and a stopping surface located above the pushed-back surface and facing upward, the drive device is located outside the output arm and includes a driving source and a mover that moves to push the lock pin when driven by the driving source, and a driving force of the driving source is set so as to be smaller than a force with which the pushback surface pushes back the pushed-back surface as the lost motion spring causes the input arm to freely swing upward and be larger than load with which the return spring displaces the lock pin.

[0008] It is preferable that the variable valve mechanism be a variable valve mechanism of a multi-cylinder internal combustion engine and drive all of movers of a plurality of cylinders by a single electromagnetic solenoid serving as the driving source.

[Functions]

[0009] When the lock pin is pushed and displaced to the lock position by the drive device in a nose phase while the valve is inactive, the input arm is swinging freely downward. The input arm and the output arm are therefore not immediately locked.

[0010] In the latter half of this nose phase, the lost motion spring causes the input arm to swing freely upward (against the driving force of the drive device) and the pushback surface pushes back the pushed-back surface of the lock pin. That is, the mover moves freely and the input arm and the output arm are ready to be locked.

[0011] When a base circle phase is started subsequently, the input arm no longer swings freely upward. The drive device therefore again pushes and displaces the lock pin to the lock position. The stopping surface thus stops the stopped surface from below and the input arm and the output arm are locked. The output arm therefore lifts the valve.

[0012] As described above, according to the present invention, the timing of switching valve operation is mechanically controlled so that the valve operation is reliably switched in the base circle phase by using the free swinging motion of the input arm.

Advantageous Effects of Invention

[0013] According to the present invention, the valve operation can be reliably switched in the base circle phase by using the free swinging motion of the input arm. The switch timing can therefore be easily controlled. The present invention is advantageous in terms of cost in the case where all of the movers for the plurality of cylinders are driven by the single electromagnetic solenoid serving as the driving source.

BRIEF DESCRIPTION OF DRAWINGS

[0014] 

FIG. 1A is a perspective view of a variable valve mechanism of an embodiment as viewed from above from the front, and FIG. 1B is a perspective view of the variable valve mechanism as viewed from below from the rear;

FIGS. 2A is a sectional view of the variable valve mechanism in an unlocked state, and FIG. 2B is a sectional view of the variable valve mechanism in a locked state;

FIGS. 3A to 3C illustrate operation of the variable valve mechanism during activation, where FIG. 3A is a sectional view in a base circle phase, FIG. 3B is a sectional view in a nose phase, and FIG. 3C is a sectional view when back in the base circle phase;

FIGS. 4A to 4C illustrate operation of the variable valve mechanism during deactivation, where FIG. 4A is a sectional view in a base circle phase, FIG. 4B is a sectional view in a nose phase, and FIG. 4C is a sectional view when back in the base circle phase;

FIGS. 5A to 5C illustrate operation of the variable valve mechanism when switched from activation to deactivation, where FIG. 5A is a sectional view in a nose phase, FIG. 5B is a sectional view in a base circle phase, and FIG. 5C is a sectional view when back in the nose phase; and

FIGS. 6A to 6C illustrate operation of the variable valve mechanism when switched from deactivation to activation, where FIG. 6A is a sectional view in a nose phase, FIG. 6B is a sectional view during transition from the nose phase to a base circle phase, and FIG. 6C is a sectional view in the base circle phase.

DESCRIPTION OF EMBODIMENTS

1. Input Arm

[0015] It is preferable that a roller rotatably placed in an input arm contact a cam. Alternatively, the input arm may have a slipper and the slipper may contact the cam.

2. Output Arm

[0016] It is preferable in terms of mountability of the input arm that the output arm be a swing arm whose swing center is located in its rear end portion. Alternatively, the output arm may be a rocker arm whose swing center is located in its middle portion.

3. Drive Source of Drive Device

[0017] The drive source is not particularly limited, but may be an electromagnetic solenoid, a hydraulic actuator, etc.

[Embodiment]

[0018] An embodiment of the present invention will be described with reference to FIGS. 1A to 6C. The structure, shape, number, etc. of parts described below are merely by way of example and may be modified without departing from the spirit and scope of the invention.

[0019] A variable valve mechanism of the present embodiment includes: an input arm 2 that swings when pressed by a cam 1; an output arm 4 that swings to push a valve 3; a lock pin 5 displaceably placed in the output arm 4; a drive device 6 that displaces the lock pin 5 to a lock position where the lock pin 5 is located in a path of a free swinging motion of the input arm 2; a return spring 7 that displaces the lock pin 5 to an unlock position where the lock pin 5 is not located in the path of the free swinging motion of the input arm 2; and a lost motion spring 8 that brakes the freely swinging input arm 2 when the lock pin 5 is located in the unlock position.

[0020] The cam 1 is formed by a base circle 11 with a circular section and a nose 12 protruding from the base circle 11.

[0021] The output arm 4 is an outer arm and includes two side walls 13, a base portion 14, and an acting portion 15. The two side walls 13 extend in the longitudinal direction and are separated from each other in the lateral direction. The base portion 14 connects the rear portions of the two side walls 13. The acting portion 15 connects the lower parts of the distal end portions of the two side walls 13. The two side walls 13, the base portion 14, and the acting portion 15 are made of a steel material and form a single-piece member. The output arm 4 has space between the intermediate portions of the two side walls 13 and between the upper parts of the distal end portions of the two side walls 13. The base portion 14 has a hemispherical recess 16 in its lower surface. A hydraulic lash adjuster 18 mounted in a cylinder head 17 has a hemispherical portion 19 at its upper end. The hemispherical recess 16 is slidably fitted on the hemispherical portion 19. The output arm 4 is thus supported so as to be swingable about the hemispherical portion 19. The lower surface of the acting portion 15 serves as a valve pushing surface.

[0022] The base portion 14 has a pin hole 20 extending therethrough in the longitudinal direction. The pin hole 20 is a round hole and is formed by a larger diameter portion located on the rear side and having a larger inside diameter, a smaller diameter portion located on the front side and having a smaller inside diameter, and a stepped portion located therebetween.

[0023] The input arm 2 is an inner arm and is disposed between the two side walls 13 (in the space) of the output arm 4. The input arm 2 includes two side plates 21 and a rear end portion 22. The two side plates 21 extend in the longitudinal direction and are separated from each other in the lateral direction. The rear end portion 22 connects the rear portions of the two side plates 21. The two side plates 21 and the rear end portion 22 are made of a steel material and form a single-piece member. The input arm 2 further includes a roller shaft 23 and a roller 25. The roller shaft 23 is passed through the intermediate portions of the two side plates 21. The roller 25 is rotatably mounted on the roller shaft 23 via a needle bearing 24. The upper end of the roller 25 is located above the upper ends of the two side plates 21 and the cam 1 contacts the upper end of the roller 25. A swing shaft 26 is inserted between near the distal ends of the two side walls 13 of the output arm 4. The two side plates 21 are pivotally mounted on the swing shaft 26 at positions near the distal ends of the two side plates 21. The input arm 2 is thus mounted on the swing shaft 26 so as to be swingable relative to the output arm 4. Each side plate 21 has a spring engaging portion 27 in the upper part of its distal end.

[0024] The upper surface of the rear end portion 22 of the input arm 2 serves as a pushback surface 28 facing upward. The lower part of the rear end face of the rear end portion 22 of the input arm 2 is cut out into a rectangular shape as viewed from the side, and the upper surface of the cutout portion serves as a stopped surface 29 located below the pushback surface 28 and facing downward.

[0025] The lock pin 5 is displaceably inserted into the pin hole 20 of the output arm 4 and is longer than the pin hole 20. The lock pin 5 is a substantially round bar and is formed by a larger diameter portion located on the rear side and having a larger outside diameter, a smaller diameter portion located on the front side and having a smaller outside diameter, and a stepped portion located therebetween. The lower part of the distal end portion of the lock pin 5 is cut out obliquely as viewed from the side, and the surface of the cutout portion serves as a pushed-back surface 31 facing obliquely downward. The upper part of the distal end portion of the lock pin 5 is cut out into a rectangular shape as viewed from the side, and the surface of the cutout portion serves as a stopping surface 32 located above the pushed-back surface 31 and facing upward.

[0026] The drive device 6 is an external drive device mounted outside and behind the output arm 4. The drive device 6 pushes the lock pin 5 protruding rearward from the output arm 4 into the output arm 4 to displace the lock pin 5 to the lock position. The drive device 6 includes an electromagnetic solenoid (not shown) serving as a driving source, and a mover 34 that moves to push the lock pin 5 into the output arm 4 when driven by the driving source. As shown in FIG. 6B, the driving force of the electromagnetic solenoid is set so as to be smaller (i.e., weaker) than the force with which the pushback surface 28 pushes back the pushed-back surface 31 as the lost motion spring 8 causes the input arm 2 to freely swing upward (the mover 34 moves freely so that the input arm 2 and the output arm 4 are ready to be locked) and be larger (i.e., stronger) than the load with which the return spring 7 displaces the lock pin 5 (after the mover 34 moves freely, the mover 34 moves in the direction toward the lock position so that the input arm 2 and the output arm 4 are locked).

[0027] The present embodiment is a variable valve mechanism of a multi-cylinder internal combustion engine. In this variable valve mechanism, a single electromagnetic solenoid is shared by the plurality of cylinders, and all of movers 34 of the plurality of cylinders are driven by the single electromagnetic solenoid. This variable valve mechanism is therefore advantageous in terms of cost. As described above, the driving force of the electromagnetic solenoid is set to be smaller than the force with which the lost motion spring 8 pushes back the pushed-back surface 31 with the pushback surface 28. It is therefore easy to share the single electromagnetic solenoid by the plurality of cylinders.

[0028]  The return spring 7 is a coil spring that is mounted around the lock pin 5 and extends and contracts between the stepped portion of the lock pin 5 and the stepped portion of the pin hole 20. The return spring 7 biases the lock pin 5 in the direction toward the unlock position.

[0029] As shown in FIG. 2A, when the drive device 6 does not push the lock pin 5, the return spring 7 extends to displace the lock pin 5 to the unlock position. Since the stopping surface 32 is disengaged from the stopped surface 29, the input arm 2 and the output arm 4 are unlocked. At this time, the distal end of the lock pin 5 is located substantially in the pin hole 20 and the rear end of the lock pin 5 protrudes rearward from the output arm 4.

[0030] In the case where the input arm 2 has swung freely upward as shown in FIG. 2B at the time the drive device 6 pushes the lock pin 5 to displace the lock pin 5 to the lock position, the stopping surface 32 immediately stops the stopped surface 29 and the input arm 2 and the output arm 4 are locked. In the case where the input arm 2 is located under the lock pin 5 as shown in FIG. 6B at the time the drive device 6 pushes the lock pin 5 to displace the lock pin 5 to the lock position, the input arm 2 and the output arm 4 are first ready to be locked as described below and are locked after the input arm 2 swings freely upward.

[0031] The lost motion spring 8 is a helical torsion spring mounted around the swing shaft 26 of the input arm 2. This helical torsion spring is a composite coil having a middle coil portion 36, a left-handed coil portion 37 located on one side of the middle coil portion 36, and a right-handed coil portion 38 located on the other side of the middle coil portion 36, and is retained with the middle coil portion 36 being in contact with the upper surface of the acting portion 15 of the input arm 2 so as not to rotate. An extended portion 39 extended from the left-handed coil portion 37 is engaged with the spring engaging portion 27 of one side plate 21, and an extended portion 39 extended from the right-handed coil portion 38 is engaged with the spring engaging portion 27 of the other side plate 21. When the input arm 2 swings downward, the left-handed coil portion 37 and the right-handed coil portion 38 are deflected, producing a biasing force that biases the input arm 2 against the cam 1.

[0032] The present embodiment configured as described above is the type of variable valve mechanism in which the input arm 2 and the output arm 4 operate as a swing arm-type roller arm and push the valve 3 when in the locked state and are inactive and do not push the valve 3 when in the unlocked state. Functions and effects of this variable valve mechanism will be described in detail below.

(1) Operation during Activation

[0033] As shown in FIG. 3A, in a base circle phase (a phase during which the base circle 11 of the cam 1 contacts the roller 25), the drive device 6 pushes the lock pin 5 into the output arm 4 to move the lock pin 5 to the lock position, the stopping surface 32 stops the stopped surface 29 from below, and the input arm 2 and the output arm 4 are locked.

[0034] As shown in FIG. 3B, in a nose phase (a phase during which the nose 12 of the cam 1 contacts the roller 25), the cam 1 pushes down the input arm 2 and also the output arm 4, and the output arm 4 swings about the hemispherical portion 19 against the load of a valve spring 9 to lift the valve 3. As soon as the valve 3 starts to lift, the lock pin 5 is subjected to load from the input arm 2 and is self-locked (the stopping surface 32 keeps stopping the stopped surface 29). The output arm 4 therefore lifts the valve 3 even if the mover 34 is separated from the lock pin 5 by the swinging of the output arm 4 (activation).

[0035] As shown in FIG. 3C, when back in the base circle phase, the lock pin 5 is released from the load from the input arm 2 and tries to unlock the input arm 2 and the output arm 4. However, since the lock pin 5 is kept pushed into the output arm 4 by the drive device 6, the input arm 2 and the output arm 4 are not unlocked.

(2) Operation during Deactivation

[0036] As shown in FIG. 4A, in a base circle phase, the mover 34 of the drive device 6 is withdrawn to such a position that the mover 34 does not contact the lock pin 5, the stopping surface 32 is disengaged from the stopped surface 29, and the input arm 2 and the output arm 4 are unlocked.

[0037] As shown in FIG. 4B, in a nose phase, since the input arm 2 and the output arm 4 are in the unlocked state, only the input arm 2 swings freely and the output arm 4 does not lift the valve 3 (deactivation).

[0038] As shown in FIG. 4C, in the base circle phase, since the mover 34 of the drive device 6 does not contact the lock pin 5, the lock pin 5 maintains the unlocked state by the return spring 7.

(3) Operation When Switching from Activation to Deactivation

[0039] As shown in FIG. 5A, in a nose phase or a base circle phase during activation, the mover 34 of the drive device 6 is withdrawn to such a position that the mover 34 does not contact the lock pin 5.

[0040] As shown in FIG. 5B, as soon as the lifting of the valve 3 is finished, the lock pin 5 is released from the load from the input arm 2 and is displaced to the unlock position by the return spring 7. The input arm 2 and the output arm 4 are thus unlocked.

[0041] As shown in FIG. 5C, in the nose phase, since the input arm 2 and the output arm 4 are in the unlocked state, only the input arm 2 swings freely and the output arm 4 does not lift the valve 3.

(4) Operation When Switching from Deactivation to Activation (Case 1)

[0042] As shown in FIG. 6A, in a nose phase during deactivation, the drive device 6 pushes the lock pin 5 into the output arm 4 to displace the lock pin 5 to the lock position. Since the input arm 2 is swinging freely downward, the input arm 2 and the output arm 4 are not immediately locked.

[0043] As shown in FIG. 6B, in the latter half of the nose phase, the lost motion spring 8 causes the input arm 2 to swing freely upward (against the driving force of the drive device 6) and the pushback surface 28 pushes back the pushed-back surface 31 of the lock pin 5. That is, the mover 34 moves freely and the input arm 2 and the output arm 4 are ready to be locked.

[0044] As shown in FIG. 6C, when a base circle phase is started, the input arm 2 no longer swings freely upward. The drive device 6 therefore again pushes the lock pin 5 into the output arm 4 to displace the lock pin 5 to the lock position. The stopping surface 32 thus stops the stopped surface 29 from below and the input arm 2 and the output arm 4 are locked. The output arm 4 therefore lifts the valve 3 as shown in FIG. 3B.

(5) Operation When Switching from Deactivation to Activation (Case 2)

[0045] As shown in FIG. 2B, in a base circle phase during deactivation, the drive device 6 pushes the lock pin 5 into the output arm 4 to displace the lock pin 5 to the lock position. The stopping surface 32 thus stops the stopped surface 29 from below and the input arm 2 and the output arm 4 are locked. The output arm 4 thus lifts the valve 3 as shown in FIG. 3B.

[0046] The present invention is not limited to the above embodiment, and various modifications can be made as appropriate without departing from the sprit and scope of the invention.

(1) A pivot that does not have a lash adjusting function may be used instead of the hydraulic lash adjuster 18.

REFERENCE SIGNS LIST

[0047] 

1

cam

2

input arm

3

valve

4

output arm

5

lock pin

6

drive device

7

return spring

8

lost motion spring

9

valve spring

11

base circle

12

nose

13

side wall

14

base portion

15

acting portion

16

hemispherical recess

17

cylinder head

18

hydraulic lash adjuster

19

hemispherical portion

20

pin hole

21

side plate

22

rear end portion

23

roller shaft

24

needle bearing

25

roller

26

swing shaft

27

spring engaging portion

28

pushback surface

29

stopped surface

31

pushed-back surface

32

stopping surface

34

mover

36

middle coil portion

37

left-handed coil portion

38

right-handed coil portion

39

extended portion

[0048] A variable valve mechanism of an internal combustion engine includes an input arm, an output arm, a lock pin, a drive device and a return spring of the lock pin, and a lost motion spring of the input arm. The input arm has in its rear end portion a pushback surface and a stopped surface. The lock pin has in its distal end portion a pushed-back surface and a stopping surface. The drive device includes a driving source and a mover that moves to push the lock pin when driven by the driving source. A driving force of the driving source is set so as to be smaller than a force with which the pushback surface pushes back the pushed-back surface as the lost motion spring causes the input arm to freely swing upward and be larger than load with which the return spring displaces the lock pin.

Claims

1. A variable valve mechanism of an internal combustion engine including an input arm (2) that swings when pushed by a cam (1), an output arm (4) that swings to push a valve (3), a lock pin (5) displaceably placed in the output arm (4), a drive device (6) that displaces the lock pin (5) to a lock position where the lock pin (5) is located in a path of a free swinging motion of the input arm (2), a return spring (7) that displaces the lock pin (5) to an unlock position where the lock pin (5) is not located in the path of the free swinging motion of the input arm (2), and a lost motion spring (8) that brakes the freely swinging input arm (2) when the lockpin (5) is in the unlock position, characterized in that
the input arm (2) has in its rear end portion a pushback surface (28) facing upward and a stopped surface (29) locatedbelow the pushback surface (28) and facing downward,
the lock pin (5) has in its distal end portion a pushed-back surface (31) facing obliquely downward and a stopping surface (32) located above the pushed-back surface (31) and facing upward,
the drive device (6) is located outside the output arm (4) and includes a driving source and a mover (34) that moves to push the lock pin when driven by the driving source, and
a driving force of the driving source is set so as to be smaller than a force with which the pushback surface (28) pushes back the pushed-back surface (31) as the lost motion spring (8) causes the input arm (2) to freely swing upward and be larger than load with which the return spring (7) displaces the lock pin (5) .

2. The variable valve mechanism of the internal combustion engine according to claim 1, wherein
the output arm (4) is a swing arm whose swing center is located in its rear end portion.

3. The variable valve mechanism of the internal combustion engine according to claim 1, wherein
the output arm (4) is an outer arm having two side walls (13) extending in a longitudinal direction and separated from each other in a lateral direction and a base portion (14) connecting rear portions of the two side walls (13) and is also a swing arm whose swing center is located in the base portion (14), and
the input arm (2) is an inner arm disposed between the two side walls (13) of the output arm (4) and is pivotally mounted on a swing shaft (26) inserted between near distal ends of the two side walls (13) of the output arm (4).

4. The variable valve mechanism of the internal combustion engine according to claim 2, wherein
a base portion (14) of the output arm (4) has a pin hole (20) extending therethrough in a longitudinal direction, and the lock pin (5) is displaceably inserted in the pin hole (20) of the output arm (4).

5. The variable valve mechanism of the internal combustion engine according to any one of claims 1 to 4, wherein
the driving source is an electromagnetic solenoid.

6. The variable valve mechanism of the internal combustion engine according to any one of claims 1 to 4, wherein
the driving source is a hydraulic actuator.

7. The variable valve mechanism of the internal combustion engine according to any one of claims 1 to 4, wherein
the variable valve mechanism is a variable valve mechanism of a multi-cylinder internal combustion engine and drives all of movers (34) of a plurality of cylinders by a single electromagnetic solenoid serving as the driving source.

Drawing