JP2011117414A - Variable valve gear of internal combustion engine - Google Patents

Abstract

The present invention relates to a variable valve operating system for an internal combustion engine that can connect a movable cam on an outer peripheral portion of an outer cam shaft and an inner cam shaft inside the outer cam shaft while suppressing friction generated by press-fitting of a pin member. I will provide a.
A variable valve apparatus according to the present invention includes a movable cam 22 on an outer peripheral portion of an outer cam shaft 17a into which a pin member 24 is press-fitted and press-fitting portions 48 and 49 of an inner cam shaft 17b inside the outer cam shaft 17a. A clearance 50 was formed in a part of them. Thereby, the resistance at the time of press-fitting the pin member 24 is reduced to suppress the press-fitting load required for press-fitting the pin member 24, and deformation and bending of the movable cam 22 and the inner cam shaft 17b accompanying the press-fitting of the pin member 24 are suppressed.
[Selection] Figure 5

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine in which the phase of a movable cam can be varied with reference to a reference cam.

In a reciprocating engine (internal combustion engine) mounted on an automobile, a variable valve gear is being mounted on a cylinder head in order to prevent engine exhaust gas and improve pumping loss.
In such a variable valve operating device, an inner cam shaft is rotatably housed in an outer cam shaft formed of a pipe member, and a shaft member driven by an engine crank output is fixed to an outer peripheral portion of the outer cam shaft. This is a pin member inserted between the movable cam and the inner cam shaft from the shaft diameter direction, between the outer cam shaft and the inner cam shaft. Adopting a connection structure that allows relative displacement of the inner camshaft, the relative displacement of the inner cam shaft output from the pin member changes the phase of the movable cam to the reference cam and changes the valve open period (split Some of them are variable (see Patent Documents 1 and 2).

  In the variable valve operating apparatus, it is required to connect the inner cam shaft and the movable cam, which are inside and outside the outer cam shaft, with an easy operation. Therefore, it has been proposed to use a press-fit pin as a pin member, press-fit the same press-fit pin from the shaft diameter direction, and connect the inner and outer movable cams to the inner cam shaft.

JP 2009-144521 A JP 2009-144522 A

By the way, when press-fitting the press-fit pin into the movable cam and the inner cam shaft, the press-fit pin is required to have a large press-fit load that allows the movable cam and the inner cam shaft to be press-fitted.
However, when the press-fit load increases, the movable cam or the inner shaft cam is easily deformed or bent. In particular, since the outer camshaft is formed of a pipe member, it is easily affected by a press-fit load. For this reason, friction between the movable cam and the outer cam shaft increases due to deformation and bending caused by press-fitting of the press-fit pin, and unnecessary friction occurs between the inner cam shaft and the outer cam shaft. Sometimes. The occurrence of the friction impairs the stability of engine performance.

  Accordingly, an object of the present invention is to provide a variable valve for an internal combustion engine that can connect a movable cam on the outer periphery of the outer cam shaft and an inner cam shaft inside the outer cam shaft while suppressing friction generated by press-fitting the pin member. To provide an apparatus.

According to the first aspect of the present invention, in order to achieve the above object, the pin member is press-fitted from the diameter direction of the shaft member, and the movable cam on the outer cam shaft outer peripheral portion and the inner cam shaft press-fitting inside the outer cam shaft Clearance was formed in some of the parts.
With this configuration, the resistance at the time of press-fitting the pin member is reduced, and the press-fit load required for press-fitting the pin member can be reduced.

In the invention according to claim 2, the clearance is obtained by forming a press-fit portion into which the pin member of the movable cam is press-fitted with a hole portion having an inner diameter dimension that cuts off the contact with the pin member so that a simple structure is required. It was decided.
In the invention according to claim 3, similarly, the clearance is obtained by forming a press-fit portion into which the pin member of the inner cam shaft is press-fitted by a hole portion having an inner diameter dimension that cuts off the contact with the pin member. .

  The invention according to claim 4 further has a structure in which the fixing member is arranged at a position away from the member driving the valve in the cam shaft direction.

  According to the first aspect of the present invention, the resistance at the time of press-fitting the pin member is reduced by forming the clearance, and the load required for press-fitting the pin member can be kept small. Shaft deformation and bending can be suppressed, and generation of friction between the movable cam and the outer cam shaft and between the inner cam shaft and the outer cam shaft due to the deformation and bending can be suppressed.

  Therefore, it is possible to connect the movable cam on the outer peripheral portion of the outer cam shaft and the inner cam shaft inside the outer cam shaft while suppressing the generation of friction while maintaining the easy press-fitting operation of the pin member. Thereby, variation in cam phase between cylinders is suppressed, and stable engine performance can be obtained. In addition, since the press-fitting load of the pin member is suppressed, there is an advantage that the variable valve operating apparatus can be easily assembled.

According to the second and third aspects of the present invention, the clearance can be secured with a simple structure in which the press-fitted portion of the movable cam or the inner cam shaft is formed by a hole having an inner diameter that cuts off the contact of the pin member.
According to the invention of claim 4, since the fixed member is disposed at a position separated from the member that contacts the movable cam and drives the valve in the cam shaft direction, for example, the fixed member protrudes to one side or comes off. In this case, it is possible to avoid the risk of meshing with a member that drives the valve, and it is possible to avoid damage to the engine due to the jumping out of the fixing member.

The top view which shows the variable valve apparatus which concerns on the 1st Embodiment of this invention with the cylinder head which mounts the apparatus. Sectional drawing of a part of variable valve apparatus which follows the II line | wire in FIG. The figure which shows the structure of the variable valve operating apparatus. The diagram which shows the variable characteristic of a variable valve apparatus. Sectional drawing which follows the II-II line | wire in FIG. The figure seen from the arrow III in FIG. Sectional drawing which shows the principal part of the 2nd Embodiment of this invention. Sectional drawing which follows the IV-IV line | wire in FIG.

Hereinafter, the present invention will be described based on a first embodiment shown in FIGS.
FIG. 1 shows a plan view of an internal combustion engine, for example, a three-cylinder (multi-cylinder) reciprocating engine (hereinafter simply referred to as an engine), and FIG. 2 shows a cross section taken along line I-I in FIG. Reference numeral 1 denotes a cylinder block of the engine, and reference numeral 2 denotes a cylinder head mounted on the head of the cylinder block 1.

Among these, the cylinder block 1 is formed with three cylinders 3 (only some of the cylinders are shown) along the longitudinal direction of the engine as shown in FIGS. 1 and 2. In each cylinder 3, pistons 4 (shown only in FIG. 2) separated from a crankshaft (not shown) via connecting rods (not shown) are housed so as to be able to reciprocate.
A combustion chamber 5 is formed on the lower surface of the cylinder head 2 corresponding to each cylinder 3. Each combustion chamber 5 has a pair of intake ports 7 (two) for performing intake and a pair of exhaust ports (not shown) for performing exhaust. Each intake port 7 is provided with a pair of intake valves 10 (two) to which tappets 9 are attached. The tappet 9 at the top faces the upper part of the cylinder head 2. Each exhaust port (not shown) is similarly provided with a pair of exhaust valves (not shown). The intake port 7 and the exhaust port (not shown) are opened and closed by the intake valve 10 and the exhaust valve (not shown). Each combustion chamber 5 is provided with a spark plug (not shown).

  Further, as shown in FIG. 1, an intake side valve operating device 6a and an exhaust side valve operating device 6b driven by the shaft output of the crankshaft are provided on the upper left and right sides of the cylinder head 2, respectively. 3, a predetermined combustion cycle (four cycles of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke) is repeatedly performed. Of these valve gears 6a and 6b, the exhaust-side valve gear 6b uses a structure using a normal camshaft 13. Specifically, a camshaft in which a pair of exhaust cams 12 are integrally formed, more specifically, a camshaft 13 formed by machining the exhaust cams 12 for three cylinders as shown in FIGS. This camshaft 13 is assembled so as to be rotatable in the direction in which the cylinders 3 are arranged, and the cam surface of each exhaust cam 12 is brought into contact with the base end portion of an exhaust valve (not shown). Thus, the cams of the exhaust cams 13 are transmitted to the exhaust valves (not shown).

Unlike the exhaust-side camshaft 13, the intake-side valve device 6a is a camshaft configured by assembling separate members as shown in FIGS. 2 and 3, a cam having a so-called assembly cam structure. A shaft 14 is used. The camshaft 14 is used to constitute a split type variable valve operating device 15 as shown in FIGS.
The variable valve operating device 15 will be described. A shaft member of the camshaft 14 is a solid member that forms a control member in an outer camshaft 17a formed of a hollow pipe member as shown in FIGS. 2 and 3, for example. It is formed by a double shaft 17 in which an inner cam shaft 17b constituted by a shaft member is rotatably housed. The double shaft 17 is also arranged along the direction in which the cylinders 3 are arranged, like the camshaft 13 on the exhaust side. One end portion (one side) of the double shaft 17, that is, one end portion of the outer cam shaft 17 a is connected to one end of the cylinder head 2 via a bracket 37 attached to the end of the outer cam shaft 17 a. It is rotatably supported by a bearing portion 18a installed at the end (one side). The intermediate portion of the outer camshaft 17a is rotatably supported by an intermediate bearing portion 18b installed between the tappets 9. Thus, both shafts 17a, 17b can be rotated about the same axis. The outer camshaft 17a and the inner camshaft 17b can be relatively displaced by a clearance.

The outer cam shaft 17a is provided with a pair (two) of intake cams 19 corresponding to the pair of intake valves 10 for each cylinder. Each of the intake cams 19 is configured by combining a reference cam 20 that determines the phase of the reference and a cam lobe 22 (corresponding to the movable cam of the present application) that serves as a movable cam.
Among these, the reference cam 20 is fixed to an outer peripheral portion corresponding to a tappet on one side of the outer cam shaft 17a, for example, the tappet 9 on the left side. The reference cam 20 is formed of a plate cam, and is fixed to the outer side of the outer cam shaft 17a by press-fitting, for example, and is fixed immediately above the left tappet 9. The cam surface of the reference cam 20 is in contact with the base end portion of the left intake valve 10 so that the cam displacement of the reference cam 20 is transmitted to the left intake valve 10.

  The cam lobe 22 has a cam nose 22a formed by a plate cam. A portion for ensuring stability, that is, a hollow boss portion 22b is combined with the cam nose portion 22a to constitute the entire cam lobe. The cam lobe 22 is fitted to the outer side of the outer cam shaft 17a so as to be rotatable in the circumferential direction, and the cam peak portion 22a is disposed immediately above the remaining right tappet 9. The cam surface of the cam crest portion 22a is in contact with the base end portion of the right intake valve 10, and the cam displacement of the cam crest portion 22a is transmitted to the right intake valve 10.

  The boss portion 22b of the cam lobe 22 and the inner cam shaft 17b are connected by press-fitting of a pin member, for example, a press-fit pin 24 (corresponding to the pin member of the present application). Specifically, the two are connected while allowing relative displacement between the outer cam shaft 17a and the inner cam shaft 17b by press-fitting the press-fit pin 24 so as to penetrate the double shaft 17 from the shaft diameter direction. It is. That is, as shown in FIGS. 3 (a) and 3 (b), in the peripheral wall portion of the outer cam shaft 17a through which the press-fit pin 24 passes, an escape hole for releasing the press-fit pin 24, for example, a long hole 26 extending in the retarding direction. When the inner camshaft 17b is relatively displaced with respect to the outer camshaft 17a, the cam phase of the cam peak portion 22a can be varied from the cam phase of the reference cam 20 as a reference to a cam phase that is retarded. I have to.

The press-fit pin 24 is disposed outside the tappet 9 (driven member) that is a member for driving the valve (at a position further away from the tappet 9 in the cam shaft direction).
A cam phase changing mechanism 25 that relatively displaces the inner and outer shafts is attached to one end of the double shaft 17, and the variable valve operating device 15 that can change the cam phase of the cam lobe 22 with reference to the reference cam 20. It is composed.

  That is, the cam phase changing mechanism 25 has a plurality of radial positions from the outer peripheral portion of the shaft portion 32 in a cylindrical housing 31 having a plurality of retarding chambers 30 along the circumferential direction as shown in FIGS. A rotating vane structure is used in which the vane portion 34 from which the vane 33 protrudes is rotatably housed and the interior of each retarded angle chamber 30 is partitioned by each vane 33. A timing sprocket 39 is provided on the outer peripheral portion of the housing 31. The sprocket 39 is connected via a timing chain 40 to a crankshaft (not shown) together with a timing sprocket 13a attached to the end of the camshaft 13 on the exhaust side. Of these, the housing 31 is connected to a bracket 37 (shown in FIG. 2) attached to the end of the outer cam shaft 17 a by a fixing bolt 36, and the shaft portion 32 of the remaining vane portion 34 is connected to the inner portion by the fixing bolt 38. The inner cam shaft 17b is displaced relative to the outer cam shaft 17a when the vane 33 is pivotally displaced in the retard chamber 30 by being connected to the shaft end of the nacam shaft 17b.

  More specifically, the cam phase of the cam lobe 22 is determined by the urging force of the return spring member 42 (shown only in FIG. 2) provided so as to pass between the housing 31 and the vane portion 34. Aligned to phase. Each retard chamber 30 is provided with an oil control valve 44 (hereinafter referred to as OCV 44) and a hydraulic pressure supply section 45 through various oil passages 43 (shown only in FIG. 2) formed in the housing 31, the bracket 37 and the bearing portion 18a. (For example, a device having an oil pump for supplying oil) is connected. That is, when oil is supplied into each retarding chamber 30, splitting is performed such that the cam lobe 22 is displaced from the reference cam 20 in the retarding direction as shown in the diagram of FIG.

  That is, the shaft output from the crankshaft (not shown) is transmitted to the outer shaft 17 a through the timing chain 40, the timing sprocket 39, the housing 31, and the bracket 37, and the reference cam 20 is driven to rotate, and the left side through the tappet 9. The intake valve 10 is opened and closed. Here, if there is no hydraulic output from the OCV 44, the cam lobe 22 rotates with the reference cam 20 while being aligned with the cam phase of the reference cam 20 as shown in the state A in FIG. 4 by the urging force of the return spring member 42. The right intake valve 10b is opened and closed while maintaining the same phase as the left reference cam 20. When the hydraulic pressure of the hydraulic pressure supply unit 45 is supplied into the retard chamber 30 through the OCV 44, the vane 33 is displaced from the initial position to the retard side in the retard chamber 30 according to the supplied hydraulic pressure. At this time, for example, when the vane 33 is displaced halfway in the retard chamber 30 by controlling the supply hydraulic pressure, the inner camshaft 17b is displaced in the retard direction to the midpoint position. The displacement of the inner cam shaft 17b at this time is transmitted to the press-fit pin 24, and the cam peak portion 22a of the cam lobe 22 is driven in the retarding direction by the output of the inner cam shaft 17b output from the pin 24. Then, due to this cam phase, as shown in the state B in FIG. 4, the opening / closing timing of the left intake valve 10 as a reference remains unchanged, and only the opening / closing timing of the right intake valve 10b changes. That is, the right intake valve 10 is opened / closed according to the cam profile of the cam peak portion 22a in the middle of the opening / closing period of the left intake valve 10. When the vane 33 is displaced to the most retarded position by controlling the supply hydraulic pressure, the opening and closing timing of the left intake valve 10 remains unchanged as shown in the state C in FIG. Opens and closes at the most retarded time from the left intake valve 10a while maintaining a state in which the left intake valve 10 is opened and closed. That is, the valve opening periods of the left and right intake valves 10 are varied within the range from the smallest valve opening period α to the largest valve opening period β (split variable) according to the state of the engine.

The variable valve operating device 15 in which the cam lobe 22 and the inner cam shaft 17 b are connected by the press-fit pin 24 has a problem specific to the device 15.
That is, when the cam lobe 22 disposed on the outer peripheral portion of the outer cam shaft 17b and the inner cam shaft 17b disposed inside the outer cam shaft 17b are connected by the press-fit pin 24, the press-fit pin 24 is simply connected to the boss portion 22b of the cam lobe 22. The press-fitting hole 48 formed in the inner camshaft 17b and the press-fitting hole 49 formed in the shaft portion of the inner camshaft 17b are simply inserted into the press-fitting hole 48 of the cam lobe 22 and the press-fitting hole 49 of the inner camshaft 17b. A large press-fit load is required. Thus, when the press-fit pin 24 is press-fitted, the cam lobe 22 and the inner camshaft cam 17b are likely to be deformed and bent, and excessive friction is generated between the cam lobe 22 and the outer camshaft 17a, and between the outer camshaft 17a and the inner camshaft 17b. And the variable performance between cylinders varies greatly, and the engine performance is impaired.

Therefore, a clearance 50 (FIGS. 5 and 6) is formed in a part of the cam lobe 22 into which the press-fit pin 24 is press-fitted and the press-fit portion of the inner cam shaft 17b to reduce the resistance when the press-fit pin 24 is press-fitted. Yes.
That is, the press-fitting portion of the press-fitting pin 24 includes a press-fitting hole 48 formed in the peripheral wall of the boss portion 22b of the cam lobe 22 shown in FIGS. 2, 3B, 5 and 6, and the shaft portion of the inner cam shaft 17b. The press-fitting hole 49 is formed in. The clearance 50 is a through hole 51 (corresponding to the hole portion of the present application) that cuts off the contact of the press-fit pin 48 with the pin surface of the press-fit pin 24. It is obtained by forming. Specifically, the through-hole 51 is formed with an inner diameter dimension slightly larger than the diameter dimension of the original press-fitting hole 49, for example, and a minute clearance 50 (see FIGS. 5 and 5) around the outer peripheral portion of the press-fit pin 24 to be inserted. 6) (the minute clearance 50 is exaggerated in the drawing for easy recognition).

  With this structure, a press-fit pin as shown in FIG. 3B is used to connect the cam lobe 22 disposed on the outer peripheral portion of the outer cam shaft 17a and the inner cam shaft 17b disposed inside the outer cam shaft 17a. When the operation of penetrating the shaft 24 from one side of the shaft is performed, the tip end portion of the press-fit pin 24 is first inserted through the through hole 51 provided on one side of the boss portion 22a. At this time, since the clearance 51 is provided between the press-fit pin 24 and the inner surface of the through hole 51, the press-fit pin 24 is inserted without applying a load that causes deformation or bending to the boss portion 22b (the pin surface is the boss portion 22b). Passing while suppressing sliding contact). Subsequently, the press-fit pin 24 is press-fitted into the press-fit hole 49 of the inner cam shaft 17b through the long hole 26 (relief hole) on one side of the outer cam shaft 17a. Further, the press-fit pin 24 penetrating the press-fit hole 49 is inserted into the through-hole 51 on the opposite side of the remaining cam lobe 22 through the long hole 26 (relief hole) on the opposite side of the remaining outer camshaft 17a. Also at this time, the press-fit pin 24 is inserted without applying a load causing deformation or bending to the boss portion 22b as described above.

At this time, since the press-fit resistance is reduced by the formation of the clearance 50, the press-fit load required for press-fitting the press-fit pin 24 can be remarkably reduced as compared with the case where both the cam lobe 22 and the inner camshaft 17b are press-fitted.
As a result, the deformation and bending of the cam lobe 22 and the inner camshaft 17b due to the press-fitting of the press-fit pin 24 are suppressed, and the cam lobe 22 and the outer camshaft 17b and the outer camshaft 17a and the inner cam caused by the deformation and bending are suppressed. Generation of excessive friction between the shafts 17b can be suppressed.

  Accordingly, the cam lobe 22 (movable cam) on the outer peripheral portion of the outer cam shaft 17b and the inner cam shaft 17b inside the outer cam shaft 17b are connected while suppressing the occurrence of friction without changing the press-fitting operation of the easy press-fit pin 24. Can be connected. Therefore, stable engine performance can be ensured. In addition, since the press-fitting load of the press-fit pin 24 is suppressed, there is an advantage that the variable valve device 15 can be easily assembled.

  Here, the fact that the press-fitting load of the press-fit pin 24 is suppressed means that the load for holding the press-fit pin 24 is low, and the press-fit pin 24 may come out due to cam drive torque fluctuation or the like. is there. That is, when the press-fit pin is arranged above the tappet 9, the press-fit pin itself drives the tappet 9 at a different timing from the cam peak portion 22a or falls and gets caught, causing interference between the valve and the piston. Although there is a possibility that it may lead to a major malfunction, the press-fit pin 24 is arranged outside the tappet 9 (driven member) that is a member that drives the valve, so that the risk of meshing with the tappet 9 is avoided. The possibility of major problems such as engine breakage due to popping out can be greatly reduced. The same effect can be obtained when the member for driving the valve is a rocker arm incorporating a roller instead of the tappet 9.

7 and 8 show a second embodiment of the present invention.
In the present embodiment, the clearance 50 is not provided in the press-fitting hole 49 of the cam lobe 22 as in the first embodiment, but the clearance 50 is provided in the press-fitting hole 48 of the inner camshaft 17b. The resistance is reduced.
Specifically, the press-fitting hole 49 formed in the shaft portion of the inner cam shaft 17b is, as in the first embodiment, a through-hole 51 that cuts off the contact with the pin surface of the press-fitting pin 24 (the original press-fitting hole 49). The inner diameter dimension is slightly larger than the diameter dimension (corresponding to the hole portion of the present application), and a minute clearance 50 is formed around the outer peripheral portion of the press-fit pin 24 to be inserted. (The minute clearance 50 is exaggerated in the drawing for easy recognition).

Even if it does in this way, there exists an effect similar to 1st Embodiment. However, in FIG. 7 and FIG. 8, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In addition, this invention is not limited to any embodiment mentioned above, You may implement variously within the range which does not deviate from the main point of this invention. In the above-described embodiment, the example in which the annular clearance 50 that is continuous so as to surround the outer peripheral portion of the press-fit pin 24 is formed using the through-hole 51 is not limited to this. The clearance may be formed using a plurality of grooves that intermittently surround the outer periphery of the press-fit pin, and the clearance is formed to reduce the resistance when the press-fit pin is pressed. I just need it. Of course, the present invention is not limited to the camshaft of the variable valve apparatus on the intake side, but can be applied to the camshaft of the variable valve apparatus on the exhaust side as long as the engine employs the variable valve apparatus on the exhaust side. May be. Moreover, it is good also as a structure used together with the conventional phase variable mechanism (mechanism which carries out phase variable simultaneously of both valves). In this case, the timing sprocket may be attached to either phase variable mechanism.

9 Tappet (driven member)
15 Variable valve operating device 17 Double shaft (shaft member)
20 Reference cam 22 Cam lobe (movable cam)
24 Press-fit pin (pin member)
48, 49 Press-fit hole (press-fit part)
50 Clearance 51 Through hole (hole)

Claims (4)

A shaft member that is configured by rotatably accommodating an inner cam shaft in an outer cam shaft formed of a pipe member, and that can be driven by a crank output of an internal combustion engine;
A reference cam provided on an outer peripheral portion of the outer cam shaft, and a movable cam provided to be rotatable around an axis of the outer cam shaft;
A pin member that connects the movable cam and the inner camshaft while allowing relative displacement between the outer camshaft and the inner camshaft;
A variable valve operating apparatus for an internal combustion engine configured such that a phase of the movable cam can be varied with reference to the reference cam by relative displacement between the outer cam shaft and the inner cam shaft,
The pin member is press-fitted into the press-fitting portion of the movable cam and the inner cam shaft from the diameter direction of the shaft member,
A variable valve operating apparatus for an internal combustion engine, wherein a clearance is formed in a part of a press-fitted portion of the movable cam and the inner cam shaft.   2. The internal combustion engine according to claim 1, wherein the clearance is formed by forming a press-fitted portion into which the pin member of the movable cam is press-fitted with a hole having an inner diameter that cuts off the contact with the pin member. Variable valve gear for engine.   2. The clearance according to claim 1, wherein the clearance is formed by forming a press-fitted portion into which the pin member of the inner cam shaft is press-fitted with a hole portion having an inner diameter that cuts off the contact with the pin member. A variable valve operating device for an internal combustion engine. 4. The variable motion of the internal combustion engine according to claim 2, wherein the pin member abuts on the movable cam and is disposed at a position separated from the member that drives the valve in the cam shaft direction. 5. Valve device.

Images