Adjustment device for the valve clearance of a gas exchange valve and method for adjusting the valve clearance of a gas exchange valve

Abstract

Adjusting device (10) for the valve clearance of a gas exchange valve (20) of an internal combustion engine, comprising a rotatably mounted rocker arm (24), at one end (30) of which an actuating element (40) is arranged, by means of which a force can be transmitted to the gas exchange valve (20), wherein a force transmission element (50) is fixed to the actuating element (40), at the end (52) of which facing away from the gas exchange valve (20) a sleeve area (54) is arranged, by means of which the force transmission element (50) is supported relative to the actuating element (40), and wherein the force transmission element (50) has an inner area (56) and an outer area (60), characterized in that the inner area (56) has an internal thread (58) and the outer area (60) has an external thread (62) for supporting the force transmission element (50) relative to the actuating element (40), wherein the force transmission element (50), which is configured as Game balancing element serves,the force transmission element (50) is supported on the actuating element (40) via its internal thread (58) by means of a preload screw (68), and wherein the force transmission element (50) is supported on a thread (42) of the actuating element (40) via its external thread (62).

Description

[0001] The invention relates to an adjusting device for the valve clearance of a gas exchange valve of an internal combustion engine, comprising a rotatably mounted rocker arm at one end of which an actuating element is arranged by means of which a force can be transmitted to the gas exchange valve. Furthermore, the invention relates to a method for adjusting the valve clearance of a gas exchange valve of an internal combustion engine by means of an adjusting device comprising a rotatably mounted rocker arm at one end of which an actuating element is fixed by means of which an actuating force can be transmitted to the gas exchange valve.

[0002] Such an adjusting device for a gas exchange valve is, for example, already known from DE 10 2009 018 963 A1. The adjusting device described therein is designed as a valve clearance adjusting element and is arranged on a valve train for actuating at least one axially displaceable gas exchange valve with an actuating unit that can be tilted about an actuating axis. The actuating unit comprises a valve actuating element for coupling with the gas exchange valve, the valve clearance adjusting element for axially adjusting the valve actuating element, and a ball joint arranged between the valve actuating element and the valve clearance adjusting element. The ball joint is aligned in a defined position by means of a return element as soon as the ball joint is in an unactuated operating state. The return element comprises a spring element, which is arranged at least partially within the ball joint.The spring element there is designed as a so-called bending pin and is subjected to particularly frequent alternating stresses during engine operation, i.e., during valve actuation for the charge exchange of a combustion chamber in the internal combustion engine. Therefore, there is a risk of fatigue fracture or valve clearance adjustment due to the frequent alternating stress on the return element.

[0003] For adjusting valve clearance on rocker arm valve trains (without hydraulic lash adjusters such as hydraulic tappets), an adjusting screw or nut is typically used, which is equipped with a locking device (e.g., a nut or stud bolt) for position locking. These adjusting screws or nuts are usually tightened with a high torque after adjustment or fine-tuning, which often leads to an unintended change in the previously set clearance value. Furthermore, at least two tools are required, which need sufficient clearance on the valve train and must be engaged simultaneously.The torque applied by means of the tools for counter-locking is absorbed via the respective component bearing points and must be taken into account when designing the clearance value, i.e. the bearing clearance, due to possible component deformations caused by the torque application.

[0004] US Patent 2011 / 0005484A1 discloses a play adjuster for a rocker arm or tappet, which, through internal spring support of the cylindrical adjusting element via internal threads, ideally sets the distance of the rocker arm to the camshaft and prevents adjustment by means of the spring action. The play adjusting element can be located in the cylinder head or in the rocker arm. The adjusted position is fixed by friction, not by material friction.

[0005] Document US 2012 / 0227695A1 discloses a valve clearance adjustment device for a rocker arm. Similar to the aforementioned document, the valve clearance is optimally adjusted via a cylindrical element with internal threads and spring assistance. The spring exerts a preload torque on the internal adjusting screw, thereby adjusting the valve clearance. There is no metallurgical connection.

[0006] German patent DE 38 13 703 A1 discloses a complexly designed valve clearance adjuster with an equally complex adjustment procedure. It is screwed into a valve rocker arm and secured via a thread. The internal mechanism consists of a sliding piston, a spring-assisted mechanism, and an adjusting screw for setting the valve clearance.

[0007] The object of the present invention is to provide an adjusting device and a method for adjusting the valve clearance of a gas exchange valve of an internal combustion engine by means of an adjusting device of the type mentioned at the outset, by means of which a valve clearance can be adjusted particularly precisely with little effort and at the same time deviations from the preset valve clearance can be permanently prevented during engine operation.

[0008] This problem is solved according to the invention by an adjustment device having the features of claim 1 and by a method having the features of claim 3. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0009] To create an adjusting device of the type mentioned above, by means of which a valve clearance can be adjusted precisely and permanently using simple means, the invention provides that a force transmission element is fixed to the actuating element, and a sleeve section is arranged at the end of this force transmission element facing away from the gas exchange valve, by means of which the force transmission element is supported relative to the actuating element. Because the force transmission element is supported relative to the actuating element via its sleeve section, tilting of the force transmission element relative to the actuating element can be effectively prevented, and thus, the longer the sleeve section, the more precise the positional tolerances that can be maintained.The force transmission element acts as a clearance compensator and automatically maintains a preset position, eliminating the need for an additional assembly step to lock or counter-hold the force transmission element. This allows the technician to adjust the valve clearance of the gas exchange valve particularly easily and quickly. In particular, this prevents incorrect settings and damage to individual components of the adjustment device, as well as reducing maintenance times. Furthermore, the installation space and tool clearance required for assembly are reduced.

[0010] In the invention, the force transmission element has an inner region and an outer region. The inner region and the outer region can, for example, each have a cylindrical contour and are accordingly arranged concentrically to each other. By arranging the inner region concentrically with respect to the outer region, the inner region can, for example, first be produced in the form of a bore, with this bore then serving as a bearing point during the production or machining of the outer region. This allows the inner region and the outer region to be aligned relative to each other with particular precision and using particularly simple means, and consequently, the force transmission element can be manufactured with particularly high precision and minimal production effort.

[0011] The inner section has an internal thread and the outer section an external thread for supporting the force transmission element against the actuating element. The internal and external threads can be precisely aligned when arranged concentrically. Furthermore, both threads can have a particularly shallow pitch, which inhibits valve clearance adjustment during alternating stress caused by the actuation of the gas exchange valve (self-locking). This is because the shallow pitch of the respective threads effectively prevents relative rotation between the force transmission element and the actuating element.

[0012] The power transmission element is supported on the actuating element via its internal thread by means of a preload screw. The preload screw is screwed into the power transmission element and bears against the actuating element via a contact surface on the head of the preload screw. This creates an internal force-fit between the preload screw, the power transmission element, and the actuating element, thereby limiting any component distortions due to mutual preload to a particularly localized and therefore minimal extent.

[0013] The power transmission element is supported by its external thread on a thread of the actuating element. Threads inherently possess a certain amount of play, which is kept particularly low due to mutual preload by ensuring that both the internal and external threads are loaded. The power transmission element is therefore not only screwed to the actuating element via its external thread, but also to the preload screw via its internal thread. Consequently, both threads—the internal and external threads of the power transmission element—are engaged and subjected to opposing forces. This results in a particularly stable fixation of the power transmission element. It is clear that the torque required to rotate the power transmission element, which, for example,The force applied by tool engagement is greater the greater the clamping force between the internal thread and the external thread, since an increased clamping force is also accompanied by an increased frictional torque to be applied between the respective threads when turning.

[0014] Finally, it has proven advantageous for the internal and external threads of the power transmission element to have the same pitch. With the same pitch, the load-bearing thread flanks are subjected to a particularly even load, allowing for higher tightening torques. Applying high tightening torques ensures a particularly high level of safety against misalignment of the power transmission element under the alternating stresses caused by valve actuation during engine operation.

[0015] In the inventive method for adjusting the valve clearance of a gas exchange valve of an internal combustion engine, a force transmission element is fixed to the actuating element by means of an outer area of ​​the force transmission element, a clamping element is fixed to an inner area of ​​the force transmission element, the force transmission element is clamped to the actuating element by applying torque to the clamping element, and the clamping element is joined to the actuating element by a material bond.

[0016] In the method, the force transmission element has an inner area and an outer area, wherein the inner area has an internal thread and the outer area has an external thread for supporting the force transmission element against the actuating element, wherein the force transmission element, which serves as a backlash compensation element, is supported on the actuating element via its internal thread by means of a preload screw, and wherein the force transmission element is supported on a thread of the actuating element via its external thread.

[0017] If the preload screw is used as the clamping element, the valve clearance can be secured particularly permanently against adjustment. By bonding the clamping element to the actuating element, for example by gluing, soldering, or welding, the security against valve clearance adjustment is further increased.

[0018] The advantages and embodiments described for the adjusting device according to the invention also apply to the method according to the invention and vice versa.

[0019] Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and the drawings.

[0020] These show in: Fig. 1 a sectional view of an adjustment device known from the prior art with a lock nut, an adjusting screw and a ball socket which is mounted in a ball head of the adjusting screw; Fig. 2a a sectional view of an adjustment device according to an embodiment of the invention; and in Fig. 2b an enlarged sectional view of the adjusting device according to the Fig. 2a shown embodiment, with a force transmission element which is clamped via respective internal or external threads to an actuating element and a clamping element designed as a preload screw.

[0021] Fig. Figure 1 shows an adjustment device 10 known from the prior art for adjusting the valve clearance of a valve (not shown) of an internal combustion engine. A rocker arm 24 is actuated by means of respective cams 14 of a camshaft 12, which is coupled to a crankshaft (not shown) of the internal combustion engine. The rocker arm 24 is rotatably mounted on a pivot bearing 26, the end 28 of which is moved depending on the rotational speed of the camshaft 12 and the cam profile of the cam 14. By moving the end 28 of the rocker arm 24, an end 30 of the rocker arm 24 opposite the end 28 is raised or lowered. At end 30 the adjusting device 10, which in this case comprises a lock nut 80, an adjusting screw 82 and a ball socket 86, is arranged, wherein the ball socket 86 is pivotably mounted on a ball head 84 of the adjusting screw 82.The ball socket 86 has a flat contact surface 90 at its end facing away from the end 30 of the rocker arm 24, which in engine operation is brought into contact with the valve (not shown here) for valve actuation and exerts an actuating force on the valve by pivoting the rocker arm 24 as a result of its deflection by the rotation of the camshaft 12, whereby this valve opens against a spring force of a Fig. The valve spring (not shown) can be opened, and accordingly, depending on whether the valve is an intake or exhaust valve, fresh air or exhaust gas can flow in or out of a combustion chamber (not shown) of the internal combustion engine. The valve clearance is adjusted using this prior art adjusting device 10 by first screwing the adjusting screw 82 into an internal thread 88, which is located at the end 30 of the rocker arm 24, and then locking the adjusting screw 82 with the lock nut 80, which is located at the end of the adjusting screw 82 opposite the ball head 84. To adjust the valve clearance, the adjusting screw 82 is screwed into the internal thread 88 until the valve clearance is exactly set, and then the adjusting screw 82 is secured with the lock nut 80.To prevent the valve clearance from being adjusted, the adjusting screw is secured by tightening the locknut 80 with a high torque. This torque, required to tighten the locknut 80 and thus secure the adjusting screw 82, can lead to an unintended change in the previously set valve clearance value, as settling can occur in the internal thread 88 or in the thread of the adjusting screw 82 that engages with the internal thread 88. Furthermore, at least two tools are required, which need sufficient clearance on the valve train and must be engaged simultaneously on the adjusting device 10 to tighten the adjusting screw 82 with the locknut 80. Due to the requirement for at least two tools engaging simultaneously, sufficient clearance must be provided on the valve train to be adjusted.

[0022] The sectional views in Fig. 2a and Fig. 2b, in contrast to Fig. 1 An exemplary embodiment of an adjusting device 10 for the valve clearance of a gas exchange valve, illustrating the invention. Identical and functionally equivalent elements are provided with the same reference numerals. The actuation of the rocker arm 24 by means of the camshaft 12 has already been described using Fig. Section 1 explains why this will not be discussed further below.

[0023] At the end, 30 is, as in Fig.Figure 2a shows an exemplary embodiment of the adjusting device 10, comprising an actuating element 40 that is essentially sleeve-shaped. The actuating element 40 has a cylindrical outer surface 38, by means of which the actuating element 40 is longitudinally displaceable and rotatably mounted at its end 30 in a complementarily shaped bore 31 of the rocker arm 24. A force transmission element 50 is received in the actuating element 40. For this purpose, the force transmission element 50 has an outer surface 60. In this case, the outer surface 60 has an external thread 62, which engages with an internal thread 42 of the actuating element 40. In other words, the force transmission element 50 is supported on the internal thread 42 of the actuating element 40 via its external thread 62.In a further step, a clamping element, which in this case is designed as a preload screw 68, is fixed to an inner region 56 of the power transmission element 50. The preload screw 68 is screwed into an internal thread 58 of the power transmission element 50 located on the inner region 56 until the head 70 of the preload screw 68 is in contact with the actuating element 40. The head 70 (hexagonal screw head) of the preload screw 68 has a bearing surface 72, which is then brought into contact with the actuating element 40. In other words, the power transmission element 50 is then additionally supported on the actuating element 40 via its internal thread 58 by means of the preload screw 68.

[0024] The power transmission element 50 thus comprises a sleeve section 54 with an inner section 56 and an outer section 60, wherein the inner section 56 has an internal thread 58 and the outer section 60 has an external thread 62 for supporting the power transmission element 50 against the actuating element 40. The sleeve section 54 is arranged at an end 52 of the power transmission element 50 facing away from a gas exchange valve 20, wherein at an end of the power transmission element 50 opposite end 52, the element has a contact surface 64 which is in contact with a valve stem 22 of the gas exchange valve 20, which is only partially shown here. During operation of the internal combustion engine, a corresponding force is transmitted to the gas exchange valve 20 by pivoting the rocker arm 24 via the contact surface 64, whereby the gas exchange valve 20 can be opened against the spring force of a spring 32, which is designed as a valve spring.The contact surface 64 has a curved surface, so that when the rocker arm 24 pivots, the contact surface 64 can slide on the valve stem 22 of the gas exchange valve 20 by means of line contact.

[0025] To fix the power transmission element 50 to the actuating element 40, the power transmission element 50 has a square 48 in the area of ​​the contact surface 64, by means of which the power transmission element 50 can be screwed to the actuating element 40 under torque. By fixing the clamping element, i.e., the preload screw 68, to the inner area 56 of the power transmission element 50, the power transmission element 50 can then be fixed in the actuating element 40 particularly securely against rotation by means of the preload screw 68. In other words, when assembling the adjusting device 10, clamping the power transmission element 50 to the actuating element 40 by applying torque to the clamping element, which is designed as the preload screw 68, creates a safeguard against rotation of the power transmission element 50 relative to the actuating element 40. This also provides an adjustment lock.A safeguard against adjustment of the valve clearance has been created. It is therefore possible, on the one hand, to fix the power transmission element 50 particularly securely against adjustment by applying opposing torques to the preload screw 68 and the actuating element 40, although this would require the simultaneous application of two tools. On the other hand, it is also possible to first screw the power transmission element 50 into the actuating element 40 and then clamp the power transmission element 50 to the actuating element 40 with the preload screw 68 to prevent rotation.

[0026] The internal thread 58 and the external thread 62 of the power transmission element 50 each have the same low pitch, which generates a particularly high self-locking effect and consequently a high frictional torque due to the preload force from the preload screw 68. This preload force therefore prevents the power transmission element 50 from adjusting itself and, depending on the friction conditions and the selected preload force, enables particularly reliable and long-lasting maintenance of a preset valve clearance. The friction acts on both the external thread 62 and the internal thread 58 and is ensured throughout the service life of the internal combustion engine by appropriate surface design and coatings of the two threads 58 and 62.To adjust the valve clearance, the resulting frictional torque must be overcome. This is achieved by engaging a tool or applying torque to a hexagon 44 of the actuating element 40, which is designed as a threaded bushing. For this purpose, a flat surface 66 is provided at the end 30 of the rocker arm 24. The flat surface 66 extends at least to the square 48 of the force transmission element 50, resulting in an overlap between the square 48 and the flat surface 66. The flat surface 66 has only a small clearance relative to one side of the square 48, allowing the force transmission element 50 to bear against the flat surface 66 when adjusting the valve clearance using the hexagon 44 of the actuating element 40. During this process, the actuating element 40 rotates within the bore 31, thus requiring only a single tool engagement.Furthermore, the flattened section 66 prevents the adjusting device 10 from rotating, so that the contact surface 64 of the force transmission element 50 cannot rotate relative to the valve stem 22. In addition, the hexagon 44 simultaneously serves as a stop for the actuating element 40 in the bore 31 on the rocker arm 24.

[0027] During valve actuation, the force is applied via the force transmission element 50 and the external thread 62 already in contact with the pressure side into the corresponding internal thread 42 of the actuating element 40 and transmitted to the hexagon 44 on the rocker arm 24. The preload force of the adjusting device 10 must also be selected such that micro-movement within the threads 42, 62 caused by tilting or bending moments introduced by the valve stem 22 is prevented.

[0028] A particularly high degree of retention of the preset valve clearance is also possible by a metallurgical bond between the clamping element, i.e., the preload screw 68, and the actuating element 40. For this purpose, a weld or solder joint is created, for example, at a metallurgical bonding area 92, which corresponds to an externally accessible contact point between the head 70 of the preload screw 68 and the actuating element 40. Alternatively, the metallurgical bond in the metallurgical bonding area 92 could also be achieved, for example, by bonding the preload screw 68 to the actuating element 40.

Claims

[1] Adjusting device (10) for the valve clearance of a gas exchange valve (20) of an internal combustion engine, comprising a rotatably mounted rocker arm (24), at one end (30) of which an actuating element (40) is arranged, by means of which a force can be transmitted to the gas exchange valve (20), wherein a force transmission element (50) is fixed to the actuating element (40), at the end (52) of which facing away from the gas exchange valve (20) a sleeve area (54) is arranged, by means of which the force transmission element (50) is supported relative to the actuating element (40), and wherein the force transmission element (50) has an inner area (56) and an outer area (60), characterized by, that the inner area (56) has an internal thread (58) and the outer area (60) has an external thread (62) for supporting the force transmission element (50) against the actuating element (40), wherein the force transmission element (50), which serves as a play compensation element, is supported on the actuating element (40) via its internal thread (58) by means of a preload screw (68), and wherein the force transmission element (50) is supported on a thread (42) of the actuating element (40) via its external thread (62). [2] Adjustment device (10) according to claim 1, characterized by , that the internal thread (58) and the external thread (62) of the power transmission element (50) each have the same pitch. [3] Method for adjusting the valve clearance of a gas exchange valve (20) of an internal combustion engine by means of an adjusting device (10) comprising a rotatably mounted rocker arm (24) at one end (30) of which an actuating element (40) is fixed, by means of which an actuating force can be transmitted to the gas exchange valve (20), characterized by the steps: - Fixing a force transmission element (50) to the actuating element (40) by means of an outer area (60) of the force transmission element (50), which serves as a play compensation element, - Fixing a clamping element to an inner area (56) of the force transmission element (50), - Clamping the power transmission element (50) to the actuating element (40) by applying torque to the clamping element, and - Material-bonded connection of the clamping element to the actuating element (40), wherein the force transmission element (50) has an inner area (56) and an outer area (60), wherein the inner area (56) has an internal thread (58) and the outer area (60) has an external thread (62) for supporting the force transmission element (50) against the actuating element (40), wherein the force transmission element (50), which serves as a play compensation element, is supported on the actuating element (40) via its internal thread (58) by means of a preload screw (68), and wherein the force transmission element (50) is supported on a thread (42) of the actuating element (40) via its external thread (62).

Images