Drain screw

Abstract

An oil drain plug (1) with an outer end (2) for connection to a drain opening (17) for hydraulic medium (11) and an inner end (4) located opposite the outer end (2), comprising a drain channel (5), is characterized in that the drain channel (5) has a drain opening (7) in the outer end (2) and an inflow opening (8) in the inner end (4) and that the inflow opening (8) is located above a level (9) of a hydraulic medium (11) in a first sealed operating state of the oil drain plug (1) and is located below or at the level of the level (9) of the hydraulic medium (11) in a second open operating state of the oil drain plug (1).

Description

[0001] The present invention relates to an oil drain plug for a transmission, in particular for transmissions of motor vehicles.

[0002] In motor vehicle construction, transmissions are increasingly being used that have two areas with different oil levels, for example in transmissions specially adapted to a hybrid drive (dedicated hybrid transmissions, DHT). These have, for example, an oil pan and an underlying oil sump, whereby gears running in the oil pan are not intended to run constantly in the oil bath in order to reduce power losses.

[0003] Electric motors are also increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same driving comfort they are accustomed to.

[0004] A detailed description of an electric drive can be found in an article in the magazine ATZ, Volume 113, May 2011, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, entitled: "Highly Integrative and Flexible Electric Drive Unit for E-Vehicles." This article describes a drive unit for one axle of a vehicle. It includes an electric motor arranged concentrically and coaxially with a bevel gear differential. A switchable 2-speed planetary gear set is arranged in the power train between the electric motor and the bevel gear differential, which is also positioned coaxially with the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between climbing ability, acceleration, and energy consumption.Such drive units are also referred to as e-axles or electrically operated axle drive trains.

[0005] To ensure adequate lubrication of the gears, the oil levels in the oil sump and pan must be precisely defined. At the same time, handling, especially filling and emptying the oil pan and sump, should be as simple as possible. Furthermore, the installation space for such transmissions or electric axles may be so limited that, for example, there is insufficient space or access for a dipstick or a viewing window for checking the hydraulic fluid level. This may also be due to the arrangement of the individual components.

[0006] DE 10 2019 110 609 A1 shows an oil drain plug for a gearbox.

[0007] US 2008 / 0 128 207 A1 shows an oil drain plug with an O-ring as a seal.

[0008] DE 10 70 888 A shows an oil drain plug equipped with a magnet.

[0009] Based on this, the present invention is based on the object of proposing an oil drain plug which, on the one hand, enables a defined filling of a gearbox housing with and, on the other hand, a simple draining of hydraulic medium from the gearbox housing.

[0010] This object is achieved by the features of independent claim 1. Further advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, with further preferred embodiments of the invention being presented.

[0011] The oil drain plug according to the invention with an outer end for connection to a drain opening for hydraulic medium and an inner end opposite the outer end, comprising a drain channel, and is characterized in that the drain channel has a drain opening in the outer end and an inflow opening in the inner end and that the inflow opening is above a level of a hydraulic medium in a first sealed operating state of the oil drain plug and is below or at the level of the level of the hydraulic medium in a second open operating state of the oil drain plug.

[0012] This makes it possible to adjust the fill level of a gearbox housing. The first operating state defines a tight seal between the gearbox housing and the oil drain plug, and the second operating state defines a required or maximum fill level. In the second, open operating state, excess hydraulic fluid can be drained, for example when hydraulic fluid is being added and the level, i.e. the maximum fill level, cannot be checked using a dipstick or a viewing window. The gearbox housing is simply filled until hydraulic fluid flows out through the opening in the inner end of the oil drain plug. The gearbox housing has a drain opening through which the oil drain plug can be passed and which closes the oil drain plug accordingly. If the oil drain plug is removed, the hydraulic fluid can flow out of the gearbox housing through the drain openings.

[0013] A hydraulic medium is understood to mean, in particular, an oil, preferably a mineral oil, that can be used for cooling, lubricating, and operating a hydraulic element. The designations were generally chosen so that, when the oil drain plug is installed, the inlet opening of the drain channel is at the top and the outlet opening is at the bottom.

[0014] It is thus possible to define and adjust the fill level using the oil drain plug according to the invention.

[0015] According to the invention, in the first sealed operating state, the inner end engages in a recess of a transmission housing, and in the second open operating state, the inner end is located outside the recess. Due to the immersion of the inner end into the recess, which is adapted in terms of its dimensions to the inner end, the drain channel can be easily closed. In the second operating state, when the inner end is guided out of the recess, excess hydraulic fluid can exit the transmission housing through the drain channel.

[0016] According to an advantageous embodiment, the oil drain plug has a screw connection consisting of an internal thread in the drain opening in the transmission housing and an external thread on the outer end of the oil drain plug, by means of which the operating conditions can be adjusted. This is achieved by simply adjusting the immersion depth of the oil drain plug by turning the screw connection, whereby the inner end with the drain opening either immerses into the recess or is lowered to the desired level of the hydraulic medium. The position of the oil drain plug, which corresponds to the desired level, can be measured, for example, or read from a marking, such as a color mark or a notch, applied to the outer end of the oil drain plug.

[0017] When the oil drain plug is completely removed from the drain hole, the hydraulic fluid can be completely drained. This creates a third operating state.

[0018] According to an advantageous embodiment of the oil drain plug, a first seal is arranged below the external thread, which seal rests against an inner wall of the drain opening in the first sealed operating state and in the second open operating state. This improves the sealing of the oil drain plug in both the first and second operating states.

[0019] It may also be advantageous to provide a second seal on the inner end of the oil drain plug, which, in the first sealed operating state, rests against an inner wall of the recess in the transmission housing. This improves the seal between the inner end and the recess in the transmission housing, so that even during significant movement of the hydraulic fluid while a motor vehicle is in motion, it cannot enter the inlet opening and thus the environment through any gap that may exist between the inner wall of the recess and the inner end.

[0020] In a further advantageous embodiment of the oil drain plug, a magnet is arranged at the inner end of the oil drain plug such that the magnet is located in the area of ​​the hydraulic medium, at least in the first sealed operating state. Such a magnet can bind metallic particles from the hydraulic medium to the magnet, preventing them from causing damage to a transmission located in the transmission housing, a pump, or a hydraulic control system.

[0021] Preferably, the transmission housing has an oil drain plug as described. The transmission housing is provided with a drain opening into which the oil drain plug can be screwed, as well as a recess designed such that the inner end can be inserted into it.

[0022] Advantageously, the gearbox housing is designed in such a way that in the second open operating state, the inlet opening is at the level of a predeterminable filling volume with hydraulic medium.

[0023] Furthermore, a transmission, in particular for a motor vehicle, is proposed, comprising a transmission housing as described here.

[0024] The details and advantages disclosed for the oil drain plug according to the invention can be transferred and applied to the transmission housing and transmission according to the invention and vice versa.

[0025] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily dictate any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment.

[0026] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description and / or figures. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. The same reference numerals denote the same objects, so that explanations from other figures can be used as a supplement if necessary. They show: Fig. 1: View of an example of an oil drain plug in a first sealed operating state; Fig. 2 View of an example of an oil drain plug in a second open operating state; Fig. 3 View of an example of an oil drain plug in a third operating state for draining the hydraulic medium;

[0027] In the description of the figures, identical parts are provided with identical reference symbols. Fig. 1 to 3 show three operating states of an oil drain plug 1 with a closure end 2 for connection to a drain opening 17. The oil drain plug 1 has an inner end 4 located opposite the closure end 2, which, when installed, lies inside a gearbox housing 12. The oil drain plug 1 comprises a drain channel 5. The drain channel 5 has an outflow opening 7 in the closure end 2 and an inflow opening 8 in the inner end 4. Furthermore, the oil drain plug 1 is provided with a first seal 13 on the closure end 2, which is arranged below a screw connection 6. The first seal 3 is designed here as an O-ring, which is arranged in a groove in the outer end 2. The screw connection 6 serves to connect to the gearbox housing 12 and to adjust the position or height of the oil drain plug 1 relative to the gearbox housing 12.The screw connection 6 also consists of an internal thread 61 in the drain opening 17 and an external thread 62 at the outer end 2. A second seal 14 is located at the inner end 4, which, like the first seal 13, is designed as an O-ring and is arranged in a groove in the inner end 4. Furthermore, the oil drain plug 1 comprises a magnet 15, which is arranged such that it is energized at least in the first tight operating state (. Fig. 1) can be flowed around by the hydraulic medium 11.

[0028] The Fig. 1 shows the oil drain plug 1 in its first sealed operating state, in which it is screwed into the gearbox housing 12 as far as it will go. The drain opening 17 of the gearbox housing 12 is then sealed by means of the thread 6 and the first seal 13 at its closing end. In addition, the inlet opening 8 at the inner end 4 is sealed by the oil drain plug 1, in this first sealed operating state, being immersed with its inner end into a cylindrical recess 10 of the gearbox housing 12, adapted to the dimensions of the inner end 4, with the second seal 14 additionally resting against an inner wall 18 of the recess 10.

[0029] In Fig. 2 shows the second open operating state of the oil drain plug 1. Compared to the first sealed operating state, the oil drain plug 1 is partially unscrewed from the gearbox housing 12. The inner end 4 leaves the recess 10, so that the drain opening 7 is exposed and can flow into the hydraulic medium 11. Using a marking (not shown), the oil drain plug 1 can be unscrewed far enough that the height of the inlet opening 8 corresponds to the desired level 9 of the hydraulic medium 11 in the gearbox housing 12. In this open operating state, for example, the oil level can be checked or a desired level 9 can be set by filling with hydraulic medium 11 until it enters the drain channel 5 through the inlet opening 8 and flows out of the drain opening 7. The first seal 13 is still effective to prevent additional hydraulic medium 11 from escaping through the thread 6.When hydraulic fluid 11 exits the drain opening 7, the filling process can be completed; the desired level is set. The oil drain plug 1 is then fully screwed back in and returned to the initial, sealed operating state.

[0030] Fig. Figure 3 shows the third operating state, which serves to drain the hydraulic medium 11. For this purpose, the oil drain plug is completely unscrewed from the gear housing 12, so that the drain opening 17 is opened and the gear housing 12 is completely emptied of the hydraulic medium 11.

[0031] In a further embodiment not shown, the drain opening 7 can branch off from the drain channel 5 at a specific angle, preferably at a 90° angle. The advantage of this embodiment is that the drain opening 7 and thus the drain channel 5 are pre-closed in the first sealed operating state and are protected against the ingress of, for example, dirt. List of reference symbols 1, 1' oil drain plug 2 closure end 4 inner end 5.5' drain channel 6 screw connection 7, 7' drain opening 8 Inlet opening 9 levels 10 Recess 11 Lubricating medium 12 Gearbox housing 13, 13' first seal 14 second seal 15 Magnet 17 Drain opening 18 inner wall 61 internal thread 62 external thread

Claims

[1] Oil drain plug (1) with an outer end (2) for connection to a drain opening (17) for hydraulic medium (11) and an inner end (4) opposite the outer end (2), comprising a drain channel (5), characterized by that the drain channel (5) has a drain opening (7) in the outer end (2) and an inflow opening (8) in the inner end (4) and that the inflow opening (8) is located above a level (9) of a hydraulic medium (11) in a first sealed operating state of the oil drain screw (1) and is located below or at the level (9) of the hydraulic medium (11) in a second open operating state of the oil drain screw (1), characterized by that in the first sealed operating state the inner end (4) engages in a recess (10) of a gear housing (12) and in the second open operating state the inner end (4) is outside the recess (10). [2] Oil drain plug (1) according to claim 1, characterized bythat a screw connection (6) consisting of an internal thread (61) in a drain opening (17) in the gear housing (12) and an external thread (62) at the outer end (2) is provided, by means of which the operating states can be adjusted. [3] Oil drain plug (1) according to one of the preceding claims, characterized by that a third operating state is provided in which the oil drain plug (1) is completely removed from the drain opening (17) to drain the hydraulic medium (11). [4] Oil drain plug (1) at least according to claim 2, characterized by that a first seal (13) is arranged below the external thread (62), which seal rests against an inner wall of the discharge opening (17) in the first sealed operating state and in the second open operating state. [5] Oil drain plug (1) at least according to claim 4, characterized bythat a second seal (14) is provided at the inner end (4), which in the first sealed operating state rests against an inner wall (18) of the recess (10). [6] Oil drain plug (1) according to one of the preceding claims, characterized by that a magnet (15) is arranged at the inner end (4) in such a way that the magnet (15) is located in the region of the hydraulic medium (11) at least in the first sealed operating state. [7] Gearbox housing (12) with an oil drain plug (1) according to one of claims 1 to 6. [8] Gearbox housing (12) according to claim 7, characterized by that in the second open operating state the inflow opening (8) is at the height of a predeterminable filling volume with hydraulic medium (11). [9] Transmission, in particular for a motor vehicle, comprising a transmission housing (12) according to one of claims 7 or 8.

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