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Cooling housing Disclosure Number: IPCOM000009461D
Original Publication Date: 2002-Sep-25
Included in the Prior Art Database: 2002-Sep-25

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Introduction: This paper explains the application of a new cooling device for electrical driven pumps. This simple de-vice shows significant advantages over existing systems as shown below. Electrical driven hydraulic pump consists of three main parts, these are:  Electronic for motor control,  Motor to produce mechanical power in form of speed [rpm] and torque [Nm], and  Hydraulic pump which transforms speed and torque into oil pressure [bar] and oil flow [l/mn]. Automotive appliances must be designed to withstand environment temperature from -40°C to +125°C. This wide temperature range demands high performance from all involved parts. Particularly high tem-peratures are crucial for electronic and motor designs. Especially for often-applied Brushless Direct Current Motors (BLDC), high environment temperature has great impact on cost and performance. The hydraulic oil plays an important role in any hydraulic systems, which serves as a carrier for pressure and flow, produced by pump. Oil is guided trough tubes and racks to its destination and back to the pump. On this way it is constantly cooled so that it never passes the maximum temperature of 80°C. Description of known solutions: A System: In this system a reservoir is filled with hydraulic oil. Motor and electronic are placed in reservoir and are covered by oil for cooling purposes. Most significant drawback of this system arise from free floating oil. High demands on tightness for mo-tor and electronic are required. This leads in increased costs for manufacturing and testing. Neverthe-less this system creates exellent cooling conditions. B System: In this system most critical parts (power transistors) of electronic are mounted adjacent to pump body. In this way these critical electronic parts are cooled by contact with pump body but does not contact oil. Motor is not cooled by oil as well as the rest of electronic components. Environment temperature may reach + 125 ° C. Therefore components (either for motor or for rest of electronic parts) must withstand these high temperatures, thereby increasing costs. This B system is nevertheless easy to manufacture and easy to test. Description of the invention: The aim of the invention is to present a solution that embraces the advantages of A and B systems but which is simple and cheap to manufacture, due to reduced temperature requirements. The idea is to build a heat sink around motor and electronic that limits maximum temperature to 80°C. Since hydraulic oil does not pass 80°C it is used as cooling medium. In difference with A and B systems oil should not have any direct contact to both electronic and motor but cools the entire system. In order to reach these conditions a special cooling device should be applied. This cooling device is hereafter referred as „housing“ and is considered to be the main part of invention. The housing (10) (see figures 1 and 2) has two tubes (11, 12) with different diameters joined together. Small bridges (13) fix the tubes to each other. Empty spaces (14) between interior and exterior walls of housing serve as a tube that guides hydraulic oil. Housing material can be any synthetic material re-sisting mechanical requirements. Housing must be mounted tightly to motor and electronic in order to minimize thermal resistance. A low thermal resistance promotes heat transportation to oil and sustains therefore an effective cooling. This kind of cooling is applicable where hydraulic pumps are driven by electric motors. Compared to the above explained B system, this housing gives also room for further possibilities to join electronic, motor, and pump together. As shown in figure 2 this housing gives opportunity to attach electronic to motor and motor to pump. This assembly has several electrical and mechanical advan-tages over B system. Hydraulic systems have also been equipped with a reservoir for oil. As housing incorporates a certain volume of oil the reservoir can be integrated into housing. This helps saving as-sembly time and material costs of the system. Benefits of housing according to invention: Benefits over A system:  Compact, small and robust system  Oil has no direct contact to electronic and motor  Less manufacturing and development costs  Low demands on tightness for electronic and motor  No friction oil/rotor and therefore low stand by current Benefits over B system:  15% less total material costs of electronic and motor  Low demand on mechanical resistance for electronic and motor  Less noise emission  Less EMI emission  Possibility to integrate the oil reservoir into housing  Performance is less dependant on temperature fluctuation caused either by fluctuating environment temperature or motor losses  Increased lifetime of insulation and bearings  Prevent injuries caused by touching hot surfaces  Opens new possibilities to arrange electronic, motor and pump. Suggested E-M-P  Rotor is over a very short shaft attached to the pump  Better solutions for the interface between motor and electronic  More possibilities to place components on the PCB  System is applicable to all arrangements where electric drives hydraulic pump