Method for testing a valve train device

Abstract

Method for testing a valve train device with a carrier shaft (11) and with a first cam element (12) mounted on the carrier shaft (11) in a rotationally fixed but axially displaceable manner and with a second cam element (13) mounted on the carrier shaft (11) in a rotationally fixed but axially displaceable manner for an internal combustion engine, in which a backlash of a splined connection between the carrier shaft (11) and the cam elements (12, 13) penetrated by the carrier shaft (11) is determined by rotating the carrier shaft (11) relative to the first cam element (12) with a predetermined torque, measuring an angle of rotation and determining the backlash from the angle of rotation, and rotating the carrier shaft (11) relative to the second cam element (13) with a predetermined torque.a rotation angle is measured and the torsional clearance is determined from the rotation angle, a tolerance range for the torsional clearance is defined for the evaluation of the valve train device, and the torsional clearance is determined for all cam elements (12, 13) connected to the carrier shaft (11).

Description

[0001] The invention relates to a method for testing a valve train device for an internal combustion engine.

[0002] From DE 10 2011 116 653 A1, a valve train device for an internal combustion engine of a motor vehicle, with at least one rotatably and axially displaceably mounted cam element, which is provided for actuating at least one gas exchange valve, is already known.

[0003] DE 10 2009 048 621 A1 discloses a valve train device for an internal combustion engine of a motor vehicle, with at least one axially displaceable cam element, which is provided for actuating at least one gas exchange valve.

[0004] WO 00 / 76 689 A1 discloses a method and a device for machining a shaft-hub connection with splined teeth.

[0005] DE 198 58 722 A1 discloses a device and a method for investigating a phase angle deviation of a camshaft.

[0006] The invention is based in particular on the objective of limiting noise generation by a valve train device and increasing the functional reliability of the valve train device. This is achieved by a method according to the invention as defined in claim 1. A further development of the invention is described in the dependent claim.

[0007] The invention relates to a valve train device with a carrier shaft and with at least one first cam element and a second cam element mounted on the carrier shaft in a rotationally fixed but axially displaceable manner, in particular for an internal combustion engine.

[0008] A method for testing such a valve train device is proposed, in which the torsional clearance of a splined connection between the carrier shaft and the cam elements penetrated by the carrier shaft is determined by rotating the carrier shaft relative to the cam elements with a predetermined torque, measuring the angle of rotation, and calculating the torsional clearance from this angle. This allows for end-of-line testing with 100% accuracy, thereby limiting noise generation from the splined connection and ensuring the sliding function of the cam elements. "Torsional clearance" is defined, in particular, as the angular range through which two components can be rotated relative to each other when a torque of a defined magnitude acts between them, first in a first direction and then in a direction opposite to the first.In this context, "interlocking gear" refers in particular to a longitudinal gear that connects the cam elements and the carrier shaft in a rotationally fixed manner. "Rotationally fixed connection" refers in particular to a connection that transmits a torque, averaged over a complete revolution, with an unchanged direction of rotation and / or an unchanged rotational speed. "Cam element" refers in particular to an element of a valve train device for actuating at least one gas exchange valve of an internal combustion engine. Preferably, the valve train device is designed for valve lift switching, and the cam elements are mounted axially displaceably on the carrier shaft and have at least one cam with at least two immediately adjacent partial cams that correspond to different valve lift curves.

[0009] To evaluate the valve train, a tolerance range for the torsional clearance is defined. By specifying an upper limit for this tolerance, noise generation during operation of the valve train can be limited, ensuring acceptable acoustic quality. Specifying a lower limit ensures that the cam elements on the carrier shaft remain axially movable and thus functional for valve lift switching. The torsional clearance provides a design parameter for both functional and acoustic component evaluation. A "tolerance range" is understood to be, in particular, a range of values ​​for the torsional clearance within which the tested components are deemed suitable.

[0010] The torsional clearance is determined for all cam elements connected to the carrier shaft. This allows manufacturing defects to be detected and increases the reliability of the supplied valve train devices. A manufacturing defect is considered to have occurred if a functional limit for minimum torsional clearance is exceeded or if an acoustic limit for maximum torsional clearance is exceeded.

[0011] It is further proposed that the cam elements be fixed for measurement. This allows the test to be carried out particularly efficiently. In this context, "fixed" means, in particular, that the cam elements cannot be rotated relative to a test fixture provided for the test. Preferably, the carrier shaft is rotated relative to the test fixture and the cam elements with a predetermined torque, and the angle of rotation is measured. It is also conceivable, in principle, that the carrier shaft is fixed in the test fixture and the cam elements are rotated relative to the test fixture and the carrier shaft. Furthermore, it is conceivable that the cam elements are aligned coaxially to the carrier shaft in the test fixture via bearing areas present on the cam elements, or that they are arranged cantilevered on the carrier shaft by means of the splined connections.

[0012] A test device for testing a valve train assembly with a carrier shaft and at least one cam element mounted on the carrier shaft in a rotationally fixed manner by means of a splined connection comprises at least one bearing point for axially and radially fixing the carrier shaft, at least one clamping unit for fixing the cam element, and a lever arm designed to rotate the carrier shaft relative to the cam element with a predetermined torque. It also includes a protractor designed to detect the angular position of the lever arm. This enables the method for determining the angle of rotation to be carried out. The test device includes a holding device designed to fix the cam element without play relative to the test device.The carrier shaft can be rotated relative to the cam element and the test fixture with a predetermined torque, and the test fixture includes a measuring unit for measuring the torque and a measuring unit for measuring the angle of rotation. If the valve assembly has several cam elements on a carrier shaft, the test fixture has several holding devices designed to fix the cam elements individually and independently of one another.

[0013] Further advantages arise from the following character description. In the Fig. 1 and Fig. Figure 2 shows an embodiment of the invention. The figures, the figure description, and the claims contain numerous features in combination. It is advantageous for a person skilled in the art to also consider the features individually and combine them into meaningful further combinations.

[0014] This shows: Fig. 1 a longitudinal section through a test device with a carrier shaft and Fig. 2 a perspective view of the test device with the carrier shaft.

[0015] The Fig. 1 and Fig. Figure 2 shows a test device 10 for testing a valve train device for an internal combustion engine, with a base 25, a holding device 26 and a measuring device 27.

[0016] The valve train assembly comprises a carrier shaft 11, a first cam element 12, and a second cam element 13. Each cam element 12, 13 comprises a cam element 14, 15, two bearing sections 16, 17, 18, 19, and four cams 20. The cams 20 are designed to be in contact with a cam follower and to actuate gas exchange valves of the internal combustion engine (not shown) by means of the cam followers. The cams 20 are designed analogously to each other and each has two axially adjacent partial cams 21, 22 with different valve lift curves. The cam elements 14, 15 are designed to interact with a pin of an actuator (not shown) for valve lift switching, thereby displacing the corresponding cam element 12, 13 in the axial direction.The cam followers assigned to the cams 20 of the cam element 12, 13 consequently switch from one partial cam 21 to the adjacent partial cam 22 or vice versa, and the valve lift of the corresponding gas exchange valve is changed.

[0017] The cam elements 12 and 13 are each formed in the form of a hollow circular cylinder. They are identical in design and have an inner surface with internal teeth. The internal teeth are formed by axially extending ribs as longitudinal teeth. A cross-section of the internal teeth is oriented perpendicular to an axis of rotation of the respective cam element 12 or 13. The carrier shaft 11 penetrates the cam elements 12 and 13 and has external teeth in the area of ​​the cam elements 12 and 13. The external teeth are formed by axially extending ribs as longitudinal teeth. A cross-section of the external teeth is oriented perpendicular to an axis of rotation of the carrier shaft 11. The external teeth of the carrier shaft 11 and the internal teeth of the cam elements 12 and 13 form a splined connection. The cam elements 12 and 13 are mounted axially movable on the carrier shaft 11.In an operating state of the valve train device, the carrier shaft 11 rotates and transmits a torque to the cam elements 12, 13. The carrier shaft 11 has a bearing area 23, 24 at each end.

[0018] The holding device 26 and the measuring device 27 of the test device 10 are arranged adjacent to each other on the base 25. The holding device 26 and the measuring device 27 are arranged one behind the other with respect to a main extension direction of the test device 10.

[0019] The holding device 26 comprises a base element 28 and a cover element 29 and is designed to accommodate the carrier shaft 11 and the cam elements 12, 13. The holding device 26 has four locking devices 30, 31, 32, 33 for connecting the cover element 29 to the base element 28. The base element 28 and the cover element 29 each have six bearing shells. Each bearing shell of the base element 28 corresponds to one bearing shell of the cover element 29 and together they form a bearing point. The peripheral bearing points of the holding device 26 are designed to interact with the corresponding bearing area 23, 24 of the carrier shaft 11 and each form a plain bearing. The remaining bearing points are designed to interact with the corresponding bearing area 16, 17, 18, 19 of the cam elements 12, 13 and each form a plain bearing.

[0020] The holding device 26 has two clamping units 34, 35 for fixing the cam elements 12, 13 relative to the test device 10. A first clamping unit 34 is assigned to the first cam element 12, a second clamping unit 35 is assigned to the second cam element 13. The clamping units 34, 35 are designed to fix the cam elements 12, 13 independently of each other without play relative to the test device 10.

[0021] The measuring device 27 comprises a coupling 36, a torque meter 37, a lever arm 38, and an angle meter 39. The measuring device 27 has three bearing plates 40, 41, 42. Two of the bearing plates 40, 41 are arranged axially on both sides directly adjacent to the lever arm 38. A third bearing plate 42 is arranged directly adjacent to the angle meter 39, between the lever arm 38 and the angle meter 39. The coupling 36 is designed to transmit a rotary movement of the lever arm 38 to the support shaft 11 without backlash. The torque meter 37 is operatively arranged between the lever arm 38 and the coupling 36.

[0022] To test the spline engagement between the carrier shaft 11 and the two cam elements 12, 13, the carrier shaft 11 with the cam elements 12, 13 is inserted into the base element 28 of the holding device 26, thereby bringing the bearing areas 23, 24 of the carrier shaft 11 and the bearing areas 16, 17, 18, 19 of the cam elements 12, 13 into contact with the bearing shells of the base element 28. The cover element 29 is placed on the base element 28 and connected to the base element 28 by the locking devices 30, 31, 32, 33, thereby bringing the bearing shells of the cover element 29 into contact with the bearing areas 23, 24 of the carrier shaft 11 and the bearing areas 16, 17, 18, 19 of the cam elements 12, 13. The cam elements 12, 13 and the carrier shaft 11 are thereby fixed in the radial and axial directions. The lever arm 38 is connected to the carrier shaft 11 in a rotationally fixed and backlash-free manner by means of the coupling 36.

[0023] The first cam element 12 is fixed to the test fixture 10 in a rotationally fixed and backlash-free manner by means of the associated clamping unit 34. The lever arm 38 is deflected in a first direction with a predetermined torque. The coupling 36 transmits the rotational movement to the carrier shaft 11. The ribs of the external teeth of the carrier shaft 11 come into contact on one side with the ribs of the internal teeth of the cam element 12 and limit the deflection of the lever arm 38. A first angular position of the lever arm 38 is recorded. The lever arm 38 is then pivoted in the opposite direction to the first with the same torque. The ribs of the external teeth come into contact on the other side with the ribs of the internal teeth of the cam element 12 and limit the deflection of the lever arm 38. A second angular position of the lever arm 38 is recorded.A difference in the angular positions yields a value for the backlash of the splined connection between the first cam element 12 and the carrier shaft 11.

[0024] To check the spline fit between the carrier shaft 11 and the second cam element 13, the clamping unit 34 of the first cam element 12 is loosened and the second cam element 13 is fixed using its associated clamping unit 35. A value for the backlash of the spline fit between the second cam element 13 and the carrier shaft 11 is determined analogously to the procedure for the first cam element 12.

[0025] This means that the torsional clearance for all cam elements 12, 13 arranged on the carrier shaft 11 is known and can be compared with a defined tolerance range. If any of the torsional clearance values ​​are less than a defined lower limit, a functional limit for the displacement of the respective cam element 12, 13 is exceeded and the valve train assembly is classified as defective. If any of the torsional clearance values ​​are greater than a defined upper limit, an acoustic limit for acceptable acoustic quality is exceeded and the valve train assembly is also classified as defective. Reference symbol list 10 Test device 11 Carrier shaft 12 cam element 13 Cam element 14 scenery elements 15 scenery elements 16 Storage area 17 Storage area 18 Storage area 19 Storage area 20 cams 21 partial cams 22 partial cams 23 Storage area 24 storage area 25 sockets 26 Holding device 27 Measuring device 28 floor elements 29 Cover element 30 Locking device 31 Locking device 32 Locking device 33 Locking device 34 clamping unit 35 clamping unit 36 Clutch 37 torque meters 38 Lever arm 39 protractors 40 bearing lamella 41 bearing lamella 42 bearing lamella

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