Transmission with oil cooling

A transmission includes a transmission housing with an oil reservoir and a transmission housing cover to close an opening of the transmission housing. A transmission shaft receives a toothed wheel and which can be driven by way of a motor. A cooler is arranged on the outside of the transmission housing, with a fan arranged on the outside of the transmission housing feeding cooling air to the cooler. An oil delivery pump pumps oil through oil delivery lines from the oil reservoir to the cooler, with an oil return line routing oil from the cooler back to the transmission housing. A separate drive motor drives the fan and the oil delivery pump independently of the transmission shaft, with the drive motor, the fan, the cooler and the oil delivery pump being fastened to the transmission housing cover.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of European Patent Application, Serial No. 17192038.2, filed Sep. 20, 2017, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a transmission.

Transmissions are known in a variety of designs from the prior art. During operation, they can heat up significantly due to incurring power loss, which may result in the permissible mechanical rating being limited. As a counter measure, transmissions are frequently cooled in order to be able to release the full mechanical power as far as possible. There are various approached for cooling a transmission.

One approach involves a cooling of transmission oil across a transmission housing surface. The achievable cooling power is however significantly restricted by the available transmission housing surface. While it is conceivable to enlarge the surface through provision of ribs or the like, this is cost-intensive however.

Another approach involves the use of external cooling units for cooling transmissions. An oil delivery pump delivers hereby oil from the transmission housing to an externally installed cooling unit, which is normally embodied in the form of a cooling fin as an oil-air cooler. The problem here however is that the installation space required for the overall system is enlarged and the cooling unit represents a further separate module which is frequently not desired.

It would therefore be desirable and advantageous to provide an improved transmission to obviate prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a transmission includes a transmission housing having an oil reservoir, a transmission housing cover configured to close an opening of the transmission housing, a motor-driven transmission shaft, a toothed wheel mounted on the transmission shaft, a cooler arranged on an outside of the transmission housing, a fan arranged on the outside of the transmission housing and configured to feed cooling air to the cooler, an oil delivery pump configured to pump oil through an oil delivery line from the oil reservoir to the cooler, an oil return line configured to route oil from the cooler back to the transmission housing, and a drive motor configured to drive the fan and the oil delivery pump independently of the transmission shaft, wherein the drive motor, the fan, the cooler and the oil delivery pump are fastened to the transmission housing cover.

The present invention resolves prior art problems by providing, i.a., a separate drive motor to drive the fan and the oil delivery pump independently of the transmission shaft and by fastening the drive motor, the fan, the cooler and the oil delivery pump to the transmission housing cover. The transmission housing cover, the drive motor, the fan, the cooler and the oil delivery pump thus form a cooling unit which is fastened by way of the transmission housing cover to the transmission housing and is embodied in a very compact manner. This is advantageous when carrying out maintenance and repair works since all components are easy to access and can be assembled and disassembled without difficulty. Furthermore, such a unit can be arranged on almost any position of the transmission housing, and thus affords a designer significant freedom when designing the transmission. As the drive motor is provided as a separate motor, i.e. in addition to a motor driving the transmission shaft or transmission shafts of the transmission, the oil volume flow fed to the cooler as well as the cooling air volume flow generated by the fan can also be adjusted irrespective of the mode of operation of the transmission by suitably selecting the speed of the separate drive motor. A further advantage associated with the use of a separate drive motor for driving the oil delivery pump and the fan resides in the fact that there is no need to configure the oil delivery pump and the fan independently of the direction of rotation. Accordingly, these components can be configured optimally, thereby lowering energy consumption and reducing sound emission of the fan.

According to another advantageous feature of the present invention, the drive motor can be an electric motor. In this way, a simple design is realized.

According to another advantageous feature of the present invention, the cooler can be an annular radial cooler which surrounds the fan and to which cooling air is fed radially by the fan. The use of such a radial cooler results in a very compact and efficient design.

According to another advantageous feature of the present invention, the oil delivery pump can be fastened to an inside of the transmission housing cover. The oil delivery pump is therefore protected from external influences by the transmission housing cover or the transmission housing itself.

According to another advantageous feature of the present invention, a hood can be provided to cover the drive motor and the fan and can have an air intake opening, with a filter being disposed in the air intake opening. In this way contamination of the fan and of the cooler can be reduced.

According to another advantageous feature of the present invention, provision can be made for a sensor to detect a current oil temperature in the transmission housing, and for a drive motor controller to regulate a speed of the drive motor as a function of a signal detected by the sensor on the basis of a target oil temperature.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The depicted embodiment is to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the FIGURE may not necessarily be to scale. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the FIGURE, there is shown a schematic illustration of a transmission according to the present invention, generally designated by reference numeral1. The transmission1includes a transmission housing2with an oil reservoir3that is embodied as an oil sump, and a transmission housing cover4closing an opening of the transmission housing2. The transmission shafts6driven by way of a motor5and the toothed wheels7held thereupon are received within the transmission housing2. For the purpose of cooling the oil, the transmission1also includes a cooling unit with a drive motor8, a drive shaft9driven by the drive motor8, a fan10, a cooler11and an oil delivery pump12. The drive motor8is held on the outside of the transmission housing cover4and is currently embodied as an electric motor. The fan10and the cooler11are also mounted on the outside of the transmission housing cover4, with the cooler11being configured as an annular radial cooler which surrounds the fan10. The oil delivery pump12pumps oil through oil delivery lines13from the oil reservoir3to the cooler11, which in turn is connected via an oil return line14to the oil reservoir3. The oil delivery pump12is mounted to the inside of the transmission housing cover4. Both the fan10and the oil delivery pump12are coupled kinematically with the drive shaft9which extends through the transmission housing cover4, so that the fan10and the oil delivery pump12can thus be driven by way of the drive motor8. A hood15which covers the drive motor8and the fan10is also fastened detachably to the transmission housing cover4. The hood15having an air intake opening provided with a filter16. A sensor17detecting the current oil temperature is positioned within the transmission housing2. The sensor17is immersed in the oil reservoir3and transmits a detected signal to a drive motor controller18. The drive motor controller18is configured to regulate the speed of the drive motor8as a function of the signal detected by the sensor17on the basis of a target oil temperature.

During operation of the transmission1, the motor5drives the transmission shafts6and the toothed wheels7held thereon. Oil available inside the transmission housing2is heated by the incurring power loss. For cooling purposes, the oil is pumped through the oil delivery lines13to the cooler11by the oil delivery pump12which is powered by the drive motor8, and the oil is routed from there via the oil recovery line14back to the oil reservoir3. An air flow generated by the fan10which is also driven by the drive motor8passes radially through the cooler11, as indicated by arrows19. The air flow removes heat from the oil and thereby cools the oil. The fan10is fed with ambient air filtered by way of the filter16, as indicated by arrows20. The sensor17detects the current oil temperature, which is compared in the drive motor controller18with a previously adjustable target temperature. When the detected actual temperature deviates upward from the target temperature, the speed of the drive motor8is regulated accordingly in order to achieve the desired cooling power.

One significant advantage of the transmission1resides in the fact that the transmission housing cover4, the drive motor8, the fan10, the cooler11and the oil delivery pump12define a cooling unit which is fastened via the transmission housing cover4to the transmission housing2and very compact. This cooling unit is easily accessible and can easily be assembled and disassembled, thereby significantly facilitating maintenance and repair works of the cooling unit or its components. Furthermore, such a cooling unit can be arranged at almost any opening of a transmission housing2, which is closed with a transmission housing cover4. This affords a designer significant freedom when designing the transmission. Due to the fact that the drive motor8is provided as a separate motor, i.e. in addition to the motor5that drives the transmission shafts2of the transmission.1, the oil volume flow fed to the cooler11as well as the cooling air volume flow generated by the fan10can also be adjusted by suitably selecting the speed of the separate drive motor8irrespective of the mode of operation of the transmission1. A further advantage associated with the use of a separate drive motor8for driving the oil delivery pump12and the fan10resides in the fact that there is no need for the oil delivery pump12and the fan10to be configured in a manner independent of the direction of rotation. Accordingly, these components can be configured optimally, thereby lowering energy consumption and reducing sound emission of the fan10.