Switchable finger follower for a valve train of an internal combustion engine

Abstract

The present invention relates to a switchable finger follower (1) for a valve train of an internal combustion engine, the finger follower having an outer rod (4) and an inner rod (3), at a first longitudinal end (5), the outer rod and the inner rod pivotally relative to each other via respective holes (6, 7) on the same cylindrical shaft (8). At this longitudinal end (5), the finger follower (1) has a gas exchange valve contact surface (12) on its lower side (9). At another longitudinal end (11), the outer rod (4) has a pivot support (10) on its lower side (9), and at least the inner rod (3) has a cam running surface (14) on its upper side (13) of the finger follower (1). For coupling, the inner rod (3) and the outer rod (4) can be connected to each other via at least one connecting slide (16) spanning a gap region (15) between the rods. The outer rod (4) and the inner rod (3) are supported relative to each other by a cam return spring device (17), and the shaft (8) is connected to the hole (6) of the outer rod (4) by means of an interference fit. In order to enable the inner rod (3) to be rotatably mounted with no radial clearance relative to the shaft (8), the hole (7) of the inner rod (3) includes a pointed arch (19) formed by two arcs as contact devices (18) in the semi-circular section of its upward-facing side (13).

Description

Technical Field

[0001] The present invention relates to a switchable finger follower for a valve train of an internal combustion engine, the finger follower having an outer rod and an inner rod, wherein at a first longitudinal end, the inner rod and the outer rod are pivotally operable relative to each other via respective holes on the same cylindrical shaft, and at this longitudinal end, the finger follower has a gas exchange valve contact surface on its lower side, wherein at another longitudinal end, the outer rod has a pivot support on its lower side, and at least the inner rod has a cam running surface on its upper side, wherein, for coupling, the inner rod and the outer rod can be connected to each other via at least one connecting slide spanning a gap region between the rods, wherein the inner rod and the outer rod are supported relative to each other via a cam return spring device, and the shaft is connected to the hole of the outer rod by means of interference fit (preamble of claim 1) or the shaft is connected to the hole of the inner rod by means of interference fit (preamble of claim 2). Background Technology

[0002] DE 10 2016 204 456 A1、 Figure 1 A switchable type of general-purpose finger follower is shown. At one longitudinal end, an outer rod and an inner rod run together on their shaft. The shaft is seated in the bore of the outer rod or the inner rod by means of a press fit via an interference fit. On the other hand, another rod (inner rod / outer rod) runs on the shaft with radial clearance (clearance fit) relative to its bore. A piston is provided as a coupling slider at the other end of the finger follower, which runs above a pivot support in the outer rod and can be partially displaced below the drive surface on the free pivoting end of the pawl-shaped inner rod for coupling.

[0003] Another switchable finger follower of the same design is described in DE 10 2018 110 573 A1. Figure 1 The information is disclosed in the literature. At one end on the valve side, the inner rod and the outer rod run on the same axis. The axis is then pressed against the outer rod or the inner rod. The corresponding other rod (inner rod or outer rod) runs through a radial clearance (clearance fit) relative to the hole of that rod. Summary of the Invention

[0004] The aim is to design a switchable finger follower in which the possibility of displacement due to radial clearance of the inner or outer rod that is not securely connected to the shaft is avoided using a simple device.

[0005] According to the invention, this objective is achieved by a feature of the feature portion of claim 1, according to which the hole of the inner rod includes a pointed arch portion in its upper-facing semi-circular section, which is composed of two arcs that serve as contact devices, so that the inner rod can be rotatably mounted with no radial clearance relative to the axis.

[0006] Alternatively, this objective is achieved by a feature of the characterizing portion of independent claim 2, according to which the hole of the outer rod includes a pointed arch in its downward-facing semicircular section, consisting of two arcs that serve as contact devices, so that the outer rod can be rotatably mounted with no radial play relative to the axis.

[0007] By means of these simple measures—namely, the secure “support” of the inner or outer rod by clearly defined line contact on the two arcs of the corresponding pointed arches, which can also be described as Gothic in profile—radial clearance from the respective swivel rings is safely eliminated, making it possible for the inner or outer rod to rotate relative to the shaft. Thus, only one of the hole-fitting portions has a perfectly circular profile.

[0008] The above applies only to cases where the cam return spring is supported via the inner and outer rods. However, this is particularly applicable and important for full cam operating contact. In summary, a switchable finger follower is provided for safe engagement and disengagement.

[0009] By eliminating radial clearance in the corresponding bore portion, a safe and aligned position of the inner rod and its actuator surface relative to the outer rod's connecting slide is always provided. Undesirable switching errors, such as those that might occur when the connecting piston moves only slightly and insufficiently into the relative profile (edge ​​contact) with the cam approaching lateral contact, no longer result in the risk of damage / "jamming" to the contact: the risk of disruption of the connecting piston and / or the risk of sudden pivoting of the inner rod relative to the outer rod due to the possibility of displacement caused by the radial clearance of the inner or outer rod. In this worst-case scenario, the inner rod can be aligned with the outer rod, but it can also be at a small angle to the outer rod, such that the connecting slide does not initially enter its entire width into its relative profile.

[0010] According to the present invention, the "finger follower" includes any type of switchable cam follower finger, which includes a shaft-mounted cam follower, a cam follower assembly, or a rocker arm or rocker arm assembly. Where necessary, the pointed arch profile can also be formed by more than two arched portions (multiples of two). It is also possible to allow the shaft to "fly" completely, i.e., without any pressing or other contact with the two hole mating portions.

[0011] As an alternative, and equally important as the measures on the corresponding holes, the shaft can only be provided with a Gothic profile in the corresponding enclosure section. However, in this case, the shaft must be installed in the correct orientation.

[0012] When the contact point of the pointed arch is closed at an angle of approximately 45°, the elimination of radial clearance can be particularly well controlled, as described in an advantageous development of the invention.

[0013] Finally, the other dependent claims relate to an advantageous design of the connecting region. The primary connecting element is, for example, a piston that can be longitudinally displaced in or below the drive surface of the inner rod. This piston can be directly actuated, for example, via a hydraulic or electromagnetic device. However, it is also conceivable and provided that the connecting slider is in the form of a slider assembly, which can also be laterally actuated on the outer side. Attached Figure Description

[0014] · Figure 1 A three-dimensional view of the switchable finger follower, viewed from above at a certain angle, is shown;

[0015] · Figure 2 A side view showing a partially sectioned section along the outer wall of the inner rod of the finger follower in the coupling region is shown; and

[0016] · Figure 3 The hole area of ​​the inner rod is shown in detail. Detailed Implementation

[0017] Figure 1 A switchable finger follower 1 is disclosed based on the basic structure of a finger follower. The finger follower 1 includes a box-shaped outer rod 4, which is partially located on the side of the arm 2 of the inner rod 3. At the first longitudinal end 5 of the finger follower 1, the outer rod 4 and the inner rod 3 pivotally move relative to each other on the same axis 8 via their respective holes 6, 7. As can be seen, the inner rod 3 is designed in a fork shape and rests on the outer side of the attachment 24 of the outer rod 4.

[0018] At the aforementioned longitudinal end 5 (shown here on the right), the outer rod 4 has a gas exchange valve contact surface 12 on its lower side 9. At the other longitudinal end 11 (see the left-hand side of the figure), the outer rod 4 has a pivot support 10 on its lower side 9, which is provided as a spherical cap for mounting on a support element fixed to the cylinder head (see also...). Figure 2 The commonly used retaining clip 27 is also drawn in this area. The inner rod 3 also has a cam running surface 14, which is designed as a roller located on the upper side 13 of the finger follower 1, and the cam running surface is framed by the arm 2 of the inner rod. The outer rod 4 is not in contact with the lifting cam.

[0019] Above the pivot support 10, a longitudinally extending connecting slide 16 is mounted. Upstream of the connecting slide is a link with deflection (see also...) Figure 2 The piston assembly 26 (not explained in more detail) has an outer piston 25 that runs transversely to the longitudinal extension of the rod and can act on the outer end face in the retraction direction via, for example, an electromagnetic servo device.

[0020] For the connection between the inner rod 3 and the outer rod 4 (cam base circuit channel) (as shown), the piston-shaped connecting slide 16 is partially displaced below the driver surface 21 of the transverse rod, which is designed to be located at the free end face 22 of the inner rod 3, within the gap region 15 between the outer rod 4 and the inner rod 3.

[0021] Finally, it should be noted that the outer rod 4 and the inner rod 3 are supported relative to each other via cam return spring devices 17. These cam return spring devices are provided in the form of two torsion springs applicable to the other longitudinal end 11, and are also referred to as "free-running springs".

[0022] The shaft 8 and the hole 6 of the outer rod 4 are pressed together. It is emphasized here that a contact device 18 is applied between the shaft 8 and the hole 7 of the inner rod 3, via which the inner rod 3 can rotate relative to the shaft 8 without radial backlash. For this purpose, the hole 7 of the inner rod 3 has a pointed arch 19 (Gothic profile) in its semi-circular section facing upwards 13. The shaft 8, surrounded by this profile, is cylindrical.

[0023] exist Figure 2 and Figure 3 In the middle, the permanent contact point 20 of shaft 8 is located on two separately prepared arcs of the pointed arch portion 19. Due to this line contact, any radial backlash is eliminated from this bore area. In the undesirable case where the connecting slide 16 only partially "protrudes" into the drive surface 21 at the end face 33 of the inner rod 3 as the cam begins to approach the side, this contact is no longer interrupted due to the radial movement of the inner rod 3 relative to shaft 8 at a longitudinal end 5, regardless of whether the inner rod 3 is in an inclined position. In short, the inner rod 3 can remain in contact without leaving this initial contact by performing a retraction movement.

[0024] like Figure 3 As shown, the contact points 20 "generated" on the two arcs of the upper semicircular section are enclosed at an angle of approximately 45° by the pointed arch 19. For the purpose of improving clarity, the entire area of ​​the hole 7 in the inner rod 3 is shown as thickened.

[0025] List of reference numerals

[0026] 1) Finger-shaped follower

[0027] 2) Arm

[0028] 3) Inner rod

[0029] 4) Outer rod

[0030] 5) Longitudinal end

[0031] 6) Outer rod hole

[0032] 7) Inner rod hole

[0033] 8) Shaft

[0034] 9) Lower side

[0035] 10) Pivot support

[0036] 11) Longitudinal end

[0037] 12) Gas exchange valve contact surface

[0038] 13) Upper side

[0039] 14) Cam running surface

[0040] 15) Interval area

[0041] 16) Connecting sliding parts

[0042] 17) Cam return spring device

[0043] 18) Contact device

[0044] 19) Pointed arch section

[0045] 20) Contact point

[0046] 21) Driver surface

[0047] 22) End face

[0048] 23) Contact point height stop

[0049] 24) Accessories

[0050] 25) External piston

[0051] 26) Piston assembly

[0052] 27) Keep clamp

Claims

1. A switchable finger follower (1) for a valve train of an internal combustion engine, the finger follower having an outer rod (4) and an inner rod (3), wherein at a first longitudinal end (5), the outer rod and the inner rod pivotally relative to each other via respective holes (6, 7) on the same cylindrical shaft (8), and at this longitudinal end (5), the finger follower (1) has a gas exchange valve contact surface (12) on its lower side (9), wherein, At another longitudinal end (11), the outer rod (4) has a pivot support (10) on the lower side (9), and at least the inner rod (3) has a cam running surface (14) on the upper side (13) of the finger follower (1), wherein, for connection, the inner rod (3) and the outer rod (4) can be connected to each other via at least one connecting slide (16) spanning the gap area (15) between the rods, wherein the outer rod (4) and the inner rod (3) are supported relative to each other via a cam return spring device (17), and the shaft (8) is connected to the hole (6) of the outer rod (4) by means of interference fit, characterized in that, in order to enable the inner rod (3) to be rotatably mounted with no radial clearance relative to the shaft (8), the hole (7) of the inner rod (3) includes a pointed arch (19) in its semi-circular section facing the upper side (13) consisting of two arcs as contact devices (18).

2. The switchable finger follower according to claim 1, characterized in that, The contact points (20) "generated" on the two arcs of the semicircular section enclose an angle of approximately 45°.

3. The switchable finger follower according to claim 1, characterized in that, The corresponding interference fit of the shaft (8) is achieved by means of press fit.

4. The switchable finger follower according to claim 1, Its features are, The inner rod (3) is in the form of a pawl, wherein the connecting slide (16) operates above the pivot support (10) in the outer rod (4) and is provided as a piston, the connecting slide being displaceable in the longitudinal direction of the finger follower (1) and being partially displaced below or in the actuator surface (21), the actuator surface being in the form of a crossbar located at the free end face (22) of the inner rod (3).

5. A switchable finger follower (1) for a valve train of an internal combustion engine, the finger follower having an outer rod (4) and an inner rod (3), wherein at a first longitudinal end (5), the outer rod and the inner rod pivotally relative to each other via respective holes (6, 7) on the same cylindrical shaft (8), and at this longitudinal end (5), the finger follower (1) has a gas exchange valve contact surface (12) on its lower side (9), wherein, At another longitudinal end (11), the outer rod (4) has a pivot support (10) on the lower side (9), and at least the inner rod (3) has a cam running surface (14) on the upper side (13) of the finger follower (1), wherein, for connection, the inner rod (3) and the outer rod (4) can be connected to each other via at least one connecting slide (16) spanning the gap area (15) between the rods, wherein the outer rod (4) and the inner rod (3) are supported relative to each other via a cam return spring device (17), and the shaft (8) is connected to the hole (6) of the inner rod (3) by means of interference fit, characterized in that, in order to enable the outer rod (4) to be rotatably mounted with no radial clearance relative to the shaft (8), the hole (6) of the outer rod (4) includes a pointed arch (19) in its semi-circular section facing the lower side (9) consisting of two arcs as contact devices (18).

6. The switchable finger follower according to claim 5, characterized in that, The contact points (20) "generated" on the two arcs of the semicircular section enclose an angle of approximately 45°.

7. The switchable finger follower according to claim 5, characterized in that, The corresponding interference fit of the shaft (8) is achieved by means of press fit.

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