CN112491180A

CN112491180A - Cooling device, electric motor and machine tool

Info

Publication number: CN112491180A
Application number: CN202010770620.9A
Authority: CN
Inventors: B·克兰克; J·梅茨; I·塞拉伊马
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 2019-09-11
Filing date: 2020-08-04
Publication date: 2021-03-12
Also published as: DE102019124328A1

Abstract

The invention relates to a cooling device for cooling a rotating shaft (20), comprising the rotating shaft (20), a coolant channel (16) formed at least by a wall (26) of the shaft (20), a coolant inlet (12) which is fluidically connected to the coolant channel (16), and a coolant outlet (14) which is fluidically connected to the coolant channel (16), characterized in that the coolant inlet (12) and the coolant outlet (14) are directly fluidically connected to one another by means of a bypass (18).

Description

Cooling device, electric motor and machine tool

Technical Field

The invention relates to a cooling device for cooling a rotating shaft, comprising a rotating shaft, a coolant channel formed at least by a wall of the shaft, a coolant inlet connected in flow terms with the coolant channel, and a coolant outlet connected in flow terms with the coolant channel. The invention also relates to an electric motor with a cooling device and to a machine tool with a cooling device.

Background

The task of cooling devices of the same type is to cool the rotating shaft and the components connected to it or arranged in the vicinity of it, in order to prevent them from overheating.

Coolant, such as oil, water-glycol mixtures, etc., is introduced into the rotating shaft here via a stationary system of interest (bezugssys) (coolant inlet). After the coolant enters the rotary shaft, it strikes against the already rotating coolant or the rotating wall of the shaft, whereby the coolant is accelerated radially and in the circumferential direction and absorbs kinetic energy there. Where a vortex is generated. Such turbulence can lead to positive pressure losses in the coolant channels that reduce the flow. When the coolant returns to the stationary system concerned (coolant outlet), the kinetic energy can generate negative pressure losses (pressure increase) in the stationary system concerned, which lead to undesired pumping effects and thus to an increased flow rate.

In both cases, the flow rate of the coolant is varied in accordance with the rotation speed of the rotary shaft. Thereby requiring increased expense in coolant flow control to ensure reliable cooling.

Disclosure of Invention

The object of the invention is to provide a cooling device in which the negative effects of positive or negative pressure losses, such as occur in the same type of cooling device, are reduced or avoided.

The object is achieved according to the invention in a cooling device of the same type in that: the coolant inlet and the coolant outlet are in direct flow connection with each other through a bypass. The flow-technical connection of the coolant inlet and the coolant outlet reduces the pressure difference between the coolant inlet and the coolant channel and the pressure difference between the coolant channel and the coolant outlet. In this way, the volume flow of the coolant can be stabilized and decoupled from the rotational speed of the shaft in terms of the action technology (wirkungstechnisch). This simplifies the volume flow control of the coolant.

In particular, at least one section of the shaft is flowed around by the coolant or the coolant flows at least in sections within the shaft. In both variants, the coolant channel is formed by at least one wall of the shaft, so that a direct contact between the shaft and the coolant is ensured, whereby the shaft is effectively cooled by the coolant.

One embodiment provides that a cooling lance is provided, which extends into the shaft. The cooling lance can introduce the coolant deeper into the shaft, so that a larger inner region of the shaft can be wetted with the coolant and a uniform flow direction can be achieved. This ensures more efficient cooling. Correspondingly, the outlet of the cooling lance is arranged in the shaft.

In particular the coolant channel is formed by at least one wall of the cooling lance in addition to the at least one wall of the shaft. The shaft and the cooling lance thus form at least part of the coolant passage.

The cooling lance is configured to be rotatable with the shaft or stationary.

The shaft may be configured as a hollow shaft and/or the cooling lance may be configured as a hollow tube. Thus, coolant may flow into the shaft through the cooling lance.

Preferably, the coolant inlet is assigned to the cooling lance and/or the coolant outlet is assigned to the shaft. Thereby ensuring that coolant is supplied to or discharged from the cooling device.

In particular the cooling lances are part of the coolant inlet. The cooling lance thus forms an extension of the coolant inlet, which extends from there into the shaft.

According to one aspect, the coolant inlet, the cooling lance, the shaft and the coolant outlet are connected in series in the listed order in terms of flow. In this way, a volumetric flow of coolant can be passed from the coolant inlet via the cooling lance into the shaft and subsequently to the coolant outlet, ensuring cooling of the shaft.

The bypass is preferably connected in flow-technical parallel to the shaft, in particular also to the cooling lance. The coolant can thus bypass the shaft and in particular the cooling lance at least partially. Accordingly, when the coolant in the coolant inlet region is excessive (positive pressure loss), the coolant may flow from the coolant inlet to the coolant outlet through the bypass. Similarly, when there is excess coolant in the coolant outlet area (negative pressure loss), coolant may bypass from the coolant outlet to the coolant inlet.

The object is also achieved according to the invention by an electric motor, in particular of a vehicle, having a cooling device of the type described above.

The shaft is designed here as a rotor shaft of an electric motor, for example. The cooling device can cool the rotor shaft and components connected to the rotor shaft or arranged in the vicinity of the rotor shaft, which components are heated, for example, on the basis of the waste heat of the magnetization losses.

The object is also achieved according to the invention by a machine tool having a cooling device of the type described above.

The shaft is designed as a spindle of a machine tool, for example.

The advantages and features of the cooling device according to the invention described apply equally to the electric motor according to the invention and to the machine tool according to the invention.

Drawings

Other advantages and features of the present invention are given by the following description and the referenced drawings. The attached drawings are as follows:

fig. 1 shows a schematic cross-sectional view of a first embodiment of a cooling device according to the invention.

Detailed Description

The cooling device 10 shown in fig. 1 includes a coolant inlet 12, a coolant outlet 14, a coolant passage 16, and a bypass 18. Furthermore, the cooling device 10 comprises a shaft 20 and a cooling lance 22.

The shaft 20 is configured as a hollow shaft open to one side. The cooling lance 22 is shaped as a hollow tube and has an outlet 24 on one end side.

Coolant inlet 12 is assigned to cooling lance 22 and merges into cooling lance 22 or, in other words, cooling lance 22 is connected to coolant inlet 12 at an opening opposite outlet 24.

The cooling lance 22 here forms an extension of the coolant inlet 12 and is therefore part of the coolant inlet 12.

The cooling lance 22 extends into the shaft 20 through the open side of the shaft 20, and the outlet 24 is disposed deep within the shaft 20.

The coolant channel 16 is directly connected to the outlet 24. Here, the coolant channel 16 is formed by an inner wall 26 of the shaft 20 and an outer wall 28 of the cooling lance 22.

The coolant outlet 14 is assigned to a shaft 20 or, in other words, the shaft 20 is connected with an open side to the coolant outlet 14.

Via the coolant inlet 12 and the cooling lance 22, the coolant can be conducted into the shaft 20 and the coolant channel 16, where the coolant extracts heat from the shaft 20 and components connected to or arranged near the shaft and transfers the heat via the coolant outlet 14 to, for example, a heat exchanger.

The coolant inlet 12, the cooling lance 22, the shaft 20 and the coolant outlet 14 are therefore connected in flow-technical series.

The coolant inlet 12 and the coolant outlet 14 are connected in terms of flow by a bypass 18. In other words, the coolant inlet 12 and the coolant outlet 14 are directly flow-connected to each other through the bypass 18.

The bypass 18 is therefore connected in flow-technical parallel to the cooling lance 22 and the shaft 20.

Thus, in the event of a pressure difference between the coolant inlet 12 and the coolant outlet 14, the coolant inlet 12 and the coolant outlet 14 can be in flow-technical direct communication with one another.

More specifically, in the event of a positive pressure loss, a portion of the coolant may flow directly from the coolant inlet 12 to the coolant outlet 14 through the bypass 18, while in the event of a negative pressure loss, a portion of the coolant may flow directly from the coolant outlet 14 back to the coolant inlet 12 through the bypass 18.

The positive pressure loss is generated based on the swirling of the coolant in the region of the outlet 24, so that the flow at the outlet 24 is reduced. So that an overpressure is produced in the cooling lance 22 and thus in the coolant inlet 12 and an underpressure is produced in the coolant channel 16 and thus in the coolant outlet 14.

When a pumping action is generated based on the rotating coolant at the transition between the rotating shaft 20 and the coolant outlet 14, a negative pressure loss occurs, whereby the flow rate at the transition increases. Thereby creating an overpressure in the coolant outlet 14 and a negative pressure in the coolant channel 16, the cooling lances 22 and the coolant inlet 12.

The pressure loss depends here on the rotational speed and the diameter of the shaft 20.

A valve 30 may be provided in the bypass 18 for volume flow regulation.

The valve 30 is, for example, a mechanical pressure reducing valve.

Alternatively, the valve 30 may be connected to a pressure sensor and electronically controlled.

The coolant inlet 12, the coolant outlet 14, and/or the bypass 18 may form a portion of the coolant channel 16.

Claims

1. A cooling device for cooling a rotating shaft (20), comprising:

a rotating shaft (20),

A coolant channel (16) formed at least by a wall (26) of the shaft (20),

A coolant inlet (12) which is connected to the coolant channel (16) in a flow-technical manner, and

a coolant outlet (14) which is connected to the coolant channel (16) in a flow-technical manner,

characterized in that the coolant inlet (12) and the coolant outlet (14) are in direct flow connection with each other by means of a bypass (18).

2. A cooling arrangement according to claim 1, characterised in that a cooling lance (22) is provided which extends into the shaft (20).

3. A cooling arrangement according to claim 2 or 3, characterized in that the coolant inlet (12), the cooling lance (22), the shaft (20) and the coolant outlet (14) are flow-technically connected in series in the listed order.

4. The cooling arrangement as claimed in one of the preceding claims, characterized in that the bypass (18) is connected in flow-technical parallel with the shaft (20).

5. Electric motor having a cooling device (10) according to any one of the preceding claims.

6. Machine tool with a cooling device (10) according to one of the preceding claims.