Computing device

An object of the present invention is to appropriately control cooling water and oil according to situations. A computing device controls a flow rate of cooling water supplied to a motor and an oil pump that supplies oil from a gear box attached to the motor to a coil of the motor. The computing device suppresses the flow rate of the cooling water supplied to the motor when a temperature of oil in the gear box is less than a first threshold, and a temperature of the coil is less than a second threshold, and operates the oil pump.

TECHNICAL FIELD

The present invention relates to a computing device.

BACKGROUND ART

The use of motors as a drive source for vehicles is widespread. Cooling is indispensable because the motor generates heat when used. It is known that not only water but also oil is used for cooling the motor. PTL 1 describes a vehicle drive device that includes an electric motor, a lubricating oil cooling means that is installed outside the electric motor and cools the lubricating oil of the electric motor with cooling water, a cooling water circulating means that circulates the cooling water via a cooling water pipe between a cooling water cooling means for cooling the cooling water, the electric motor, and the lubricating oil means, and a lubricating oil circulating means that circulates the lubricating oil via a lubricating oil pipe between the lubricating oil cooling means and the electric motor.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the invention described in PTL 1, there is room for improvement in the control of cooling water and oil.

Solution to Problem

A computing device according to a first aspect of the present invention controls a flow rate of cooling water supplied to a motor and an oil pump that supplies oil from a gear box attached to the motor to a coil of the motor. The computing device suppresses the flow rate of the cooling water supplied to the motor when a temperature of oil in the gear box is less than a first threshold, and a temperature of the coil is less than a second threshold, and operates the oil pump.

Advantageous Effects of Invention

According to the present invention, it is possible to appropriately control cooling water and oil according to situations.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment of a cooling system S will be described below with reference toFIGS.1to3.

FIG.1is an overall configuration diagram of the cooling system S. The cooling system S is mounted on a vehicle9. The cooling system S includes a motor11with a built-in coil C, a gear box12, a radiator13, a computing device14, an electric water pump WP, and an electric oil pump OP. The motor11includes a water jacket11J having a cooling water passage. InFIG.1, a thin solid line represents the movement of water, a thick solid line represents the movement of oil, and a broken line represents a signal line. In the following, “oil” and “oil” are used interchangeably, and “water” and “cooling water” are used interchangeably. Further, inFIG.1, the inverter that shares the electric power with the motor11is not shown.

The water pumped by the water pump WP absorbs heat from the motor11in the water jacket11J of the motor11and releases heat in the radiator13. That is, in this embodiment, the water pumped by the water pump WP has a role as cooling water. The oil pump OP is built in the gear box12and supplies the oil used for lubricating and cooling the transmission to the coil C of the motor11. The oil supplied to the coil C returns to the gear box12after the temperature with the coil C is homogenized.

The motor11includes a temperature sensor Sc that measures the temperature Tc of the coil C. The motor11operates with the electric power supplied from an inverter (not shown) based on an operation command of a motor control device (not shown). In this embodiment, the control method and operation of the motor11itself are not particularly limited. The temperature sensor Sc outputs information on the coil temperature Tc to the computing device14. The gear box12includes a temperature sensor Sg that measures the oil temperature Tg in the gear box12. The temperature sensor Sg outputs information on the oil temperature Tg to the computing device14.

The computing device14is a device for performing computation, built into the vehicle9, for example, an ECU (Electronic Control Unit). The computing device14outputs an operation command to the oil pump OP and the water pump WP based on the coil temperature Tc and the oil temperature Tg. The configuration of the computing device14will be described in detail with reference toFIG.2below. The rotation speeds of the water pump WP and the oil pump OP are controlled so that the flow rate can be adjusted.

(Configuration of Computing Device14)

FIG.2is a configuration diagram of the computing device14. The computing device14includes a CPU141which is a central computing device, a ROM142which is a read-only storage device, and a RAM143which is a read/write storage device. The computing device14realizes the functions described later by the CPU141expanding the program stored in the ROM142to the RAM143. The computing device14further includes a sensor receiving unit144that receives temperature information from the temperature sensor Sg and the temperature sensor Sc, and a pump command unit145that outputs an operation command to the oil pump OP and the water pump WP.

The sensor receiving unit144has a hardware configuration corresponding to the communication specifications of the temperature sensor Sg and the temperature sensor Sc. For example, if the temperature sensor Sg and the temperature sensor Sc are resistance temperature detectors, the sensor receiving unit144has hardware for measuring electrical resistance. Further, if the temperature sensor Sg and the temperature sensor Sc transmit the measured value as a digital signal, the sensor receiving unit144includes a digital signal processing circuit. The pump command unit145has a hardware configuration corresponding to the communication specifications of the oil pump OP and the water pump WP. For example, when the oil pump OP and the water pump WP can set the target rotation speed by analog signals of current and voltage, the pump command unit145includes a current generator and a voltage generator.

FIG.3is a flowchart showing the operation of the computing device14. The execution subject of each step described below is the CPU141. When the ignition key switch of the vehicle9is turned on, the computing device14performs the following operations. That is, the operation described below is executed when the vehicle9is started.

The computing device14first reads the temperature information from the temperature sensor Sg and the temperature sensor Sc (S601). Although the temperature information is continuously read after this, the description is omitted in the flowchart. Next, the computing device14determines whether the read oil temperature Tg is less than a first threshold Th1stored in the ROM142. In S602, the computing device14determines whether the oil temperature Tg is at a low temperature at which the viscosity of the oil increases and friction, that is, the problem of friction can occur. The computing device14proceeds to S603when it determines that the oil temperature Tg is less than the first threshold Th1, and proceeds to S609when it determines that the oil temperature Tg is equal to or more than the first threshold Th1.

In S603, the computing device14determines whether the read coil temperature Tc is less than a second threshold Th2stored in the ROM142. In this S603, the computing device14determines whether the coil temperature Tc is in a high temperature range where the coil C may be damaged. The computing device14proceeds to S604when it determines that the coil temperature Tc is less than the second threshold Th2, and proceeds to S609when it determines that the coil temperature Tc is equal to or more than the second threshold Th2.

In S604, the computing device14suppresses the cooling water supplied to the motor11. Specifically, the computing device14sets the output of the water pump WP to the minimum, for example, a minimum rotation speed that can be set. When the output of the water pump WP has already been set to the minimum in S604, the output is maintained to the minimum without any special change. In the following S605, the computing device14determines whether the oil temperature Tg is equal to or lower than the coil temperature Tc. The intention of establishing this S605is as follows. That is, if the oil temperature Tg is higher than the coil temperature Tc, the oil temperature drops when the oil is supplied to the coil C, which is the intention to prevent this. The computing device14proceeds to S606when it determines that the oil temperature Tg is equal to or lower than the coil temperature Tc, and proceeds to S607when it determines that the oil temperature Tg is higher than the coil temperature Tc.

In S606, the computing device14operates the oil pump OP at a predetermined rotation speed and proceeds to S608. In S607, the computing device14stops the operation of the oil pump OP, that is, sets the rotation speed of the oil pump OP to zero and returns to S604. If the output of the oil pump OP has already stopped in S607, the oil pump OP will be maintained in the stopped state without making any special changes. In S608, the computing device14determines whether the oil temperature Tg has risen to the first threshold Th1or higher, proceeds to S609when it is determined as affirmative, and returns to S603when it is determined as negative. In S609, the computing device14releases the suppression of the cooling water supplied to the motor11. Specifically, the computing device14sets the output of the water pump WP to a normal level, for example, a predetermined rotation speed, and ends the process shown inFIG.3.

According to the first embodiment, the following operational effects are obtained.

(1) The computing device14controls the flow rate of the cooling water supplied to the motor11and the oil pump OP that supplies oil from the gear box12attached to the motor11to the coil C of the motor11. When the temperature of the oil in the gearbox12is less than the first threshold Th1and the temperature of the coil C is less than the second threshold Th2(S602: YES and S603: YES inFIG.3), the computing device14suppresses the flow rate of the cooling water supplied to the motor11(S604), and operates the oil pump OP (S606). Therefore, when the friction of the gear box12is large because the oil temperature Tg is low and the viscosity is high, the oil temperature Tg can be increased to lower the friction of the gear box12. Further, when the coil temperature is equal to or higher than the second threshold Th2, the supply of cooling water is not suppressed, so that there is no risk of damaging the motor11, and the computing device14can appropriately control the cooling water and oil according to the situation.

(2) The computing device14controls the oil pump OP that supplies cooling water to the motor11. Suppressing the flow rate of the cooling water supplied to the motor11means setting the rotation speed of the water pump WP to the minimum rotation speed that can be set. Therefore, the computing device14can realize appropriate control of the cooling water according to the situation by controlling the water pump WP.

(3) When the temperature of the oil in the gear box12is less than the first threshold Th1(S602: YES), and the temperature of the coil C is less than the second threshold Th2(S603: YES), the computing device14operates the oil pump OP if the temperature of the oil in the gearbox12is equal to or less than the temperature of the coil C (S605: YES, S606), and stops the oil pump OP if the temperature of the oil in the gear box12is higher than the temperature of the coil C (S605: NO, S607). Therefore, when the temperature Tc of the coil C is lower than the oil temperature Tg, it is possible to prevent the oil temperature from dropping by supplying oil to the coil C.

Even if the computing device14may be realized by FPGA (Field Programmable Gate Array), which is a rewritable logic circuit instead of the combination of the CPU141, the ROM142, and the RAM143, or ASIC (Application Specific Integrated Circuit) which is an integrated circuit for specific applications. Further, the computing device14may be realized by a combination of different configurations, for example, a combination of the CPU141, the ROM142, the RAM143, and the FPGA, instead of the combination of the CPU141, the ROM142, and the RAM143.

If the rotation of the water pump WP can be stopped, the computing device14may stop the rotation of the water pump WP in S604ofFIG.3.

The shape and dimensions of the flow path of the cooling water in the water jacket11J are well known. Therefore, the Reynolds number can be calculated and a maximum flow rate of the cooling water (hereinafter, referred to as “limit flow rate”) in which the flow of the cooling water becomes a laminar flow can be calculated in advance in the water jacket11J. The computing device14may control the rotation speed of the water pump WP to the rotation speed of the limit flow rate or less in S604ofFIG.3.

According to the third modification, the following effects can be obtained.

(4) The water pump WP includes the water jacket11J through which the cooling water passes. Suppressing the flow rate of the cooling water in the S604means reducing the flow rate of the cooling water supplied to the motor11so that the flow of the cooling water in the water jacket11J becomes a laminar flow. Therefore, the flow of the cooling water in the water jacket11J becomes a laminar flow, so that the efficiency of heat exchange between the motor11and the cooling water is greatly reduced, and the temperature drop of the motor11is suppressed.

The cooling water pumped by the water pump WP may also be cooled by the inverter that supplies electric power to the motor11.

FIG.4is an overall configuration diagram of the cooling system S1in the fourth modification. The cooling system S1further includes an inverter15in addition to the configuration of the cooling system S in the first embodiment. The inverter15supplies electric power to the motor11based on an operation command of a motor control device (not shown). However, inFIG.4, the signal line between the inverter15and the motor control device (not shown) and the power supply line from the inverter15to the motor11are not shown. According to this modification, the inverter15can also be cooled by the cooling water.

At least one of the water pump WP and the oil pump OP may be rotated for a predetermined time before the motor11is energized. This is to discharge the air contained in the oil and the cooling water.

Second Embodiment

A second embodiment of the computing device will be described with reference toFIG.5. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. The points that are not particularly described are the same as in the first embodiment. This embodiment differs from the first embodiment mainly in that the cooling system includes a control valve.

FIG.5is an overall configuration diagram of the cooling system S2according to the second embodiment. The cooling system S2further includes a control valve16in addition to the configuration of the cooling system S in the first embodiment. The control valve16operates according to an operation command of the computing device14. The control valve16is provided on the motor11side after branching downstream of the water pump WP.

The control valve16is an adjustment valve that can be adjusted to an arbitrary valve opening degree of 0 to 100%. When the control valve16is fully closed, the total flow rate discharged by the water pump WP bypasses the motor11and flows to the radiator13, and when the control valve16is not fully closed, the cooling water also flows to the motor11. However, the control valve16does not have to be fully closed. In other words, the control valve16does not have to have a Cv value of zero when the valve opening degree is 0%.

In this embodiment, the computing device14suppresses the rotation speed of the water pump WP in S604and sets the valve opening degree of the control valve16to a minimum valve opening degree that can be set. Further, the computing device14sets the rotation speed of the water pump WP to a normal level in S609, and sets the valve opening degree of the control valve16to a predetermined value larger than 0%.

According to the second embodiment, the following operational effects are obtained.

(5) The computing device14controls the control valve16that controls the flow rate of the cooling water supplied to the motor11. Suppressing the flow rate of the cooling water supplied to the motor11means operating the valve opening degree of the control valve16so that the cooling water supplied to the motor11is reduced. Therefore, the computing device14can realize appropriate control of the cooling water according to the situation by operating the valve opening degree of the control valve16.

(First Modification of Second Embodiment)

The control valve16may be an opening/closing valve that can take only two states, fully open or fully closed, a so-called on/off valve. In this case, the computing device14sets the control valve16to be fully closed in S604and the control valve16to be fully open in S609.

(Second Modification of Second Embodiment)

The control valve16may be provided downstream of the water pump WP on the bypass side after branching, that is, on the side opposite to that inFIG.5. In this case, the computing device14sets the valve opening degree of the control valve16to a predetermined value larger than 0% in S604, and sets the valve opening degree of the control valve16to 0% in S609.

(Third Modification of Second Embodiment)

The computing device14does not have to control the water pump WP. That is, the computing device14may realize the control of the cooling water substantially the same as that of the first embodiment by controlling the valve opening degree of the control valve16. In this case, the water pump WP is always controlled to a constant rotation speed.

Third Embodiment

A third embodiment of the computing device will be described with reference toFIG.6. In the following description, the same components as those in the second embodiment are denoted by the same reference numerals, and differences will be mainly described. The points that are not particularly described are the same as in the second embodiment. This embodiment differs from the second embodiment mainly in that the cooling system includes an inverter.

FIG.6is an overall configuration diagram of the cooling system S3according to the third embodiment. The cooling system S3further includes the inverter15and the control valve16in addition to the configuration of the cooling system. S in the first embodiment. The control valve16operates according to an operation command of the computing device14. The control valve16is provided on the motor11side after branching downstream of the inverter15. The operation of the computing device14is the same as that of the second embodiment.

According to the third embodiment, the following operational effects are obtained.

(6) The cooling water also cools the inverter15that supplies electric power to the motor11. Suppressing the flow rate of the cooling water supplied to the motor11does not affect the flow rate of the cooling water supplied to the inverter15. Therefore, the computing device14can appropriately control the cooling water and the oil according to the situation while also cooling the inverter15.

(First Modification of Third Embodiment)

In the third embodiment described above, the inverter15is provided between the water pump WP and the branch. However, the inverter15may be provided immediately before the water pump WP, that is, at the position where the water pressure is the lowest. Further, the inverter15may be provided upstream of the radiator13. In this case, it is desirable for the inverter15that both the cooling water that has passed through the motor11and the cooling water that has bypassed the motor11flow into the inverter15to cool the inverter15.

(Second Modification of Third Embodiment)

The computing device14does not have to control the water pump WP. That is, the computing device14may realize the control of the cooling water substantially the same as that of the first embodiment by controlling the valve opening degree of the control valve16. In this case, the water pump WP is always controlled to a constant rotation speed.

The above-described embodiments and modifications may be combined with each other. Various embodiments and modifications have been described, but the present invention is not limited to these contents. Other aspects which are conceivable within a scope of technical ideas of the present invention may be made within the scope of the present invention.

REFERENCE SIGNS LIST