JP7003742B2 - Flow control device for electric oil pump - Google Patents

Description

The present invention relates to a flow control device for an electric oil pump that supplies cooling oil to a vehicle motor.

In recent years, some vehicles such as automobiles use a motor, but in order to prevent accidents such as ignition due to heat generation of the motor, cooling oil is supplied to the motor by an electric oil pump.

Japanese Unexamined Patent Publication No. 2015-016894

The cooling oil has a viscosity, but as the oil temperature rises, the viscosity decreases and the flow rate also increases, so that the heat transfer coefficient of the cooling oil is improved and the cooling capacity is increased.

However, when the predetermined flow rate (minimum saturation flow value) is exceeded, the heat transfer coefficient (cooling capacity) of the cooling oil is saturated, and then even if the oil temperature of the cooling oil rises and the flow rate increases, the heat transfer coefficient No longer improves.

Nevertheless, if excessive cooling oil is continuously supplied to the rotor of the motor, the stirring resistance of the cooling oil by the rotor increases, and on the contrary, there is a problem that the power loss of the motor is increased and the driving capacity is impaired. ..

The present invention relates to a flow control device for an electric oil pump capable of supplying cooling oil to a motor at an optimum thermal conductivity and an optimum flow rate even when the cooling oil becomes hot.

The flow control device for an electric oil pump according to the present invention controls the flow rate of cooling oil discharged from a cooling pipe to a motor for an electric oil pump that pumps cooling oil for cooling a motor used in a vehicle into a cooling pipe. , The flow control device of the electric oil pump, the oil temperature detector that detects the oil temperature of the cooling oil, the relationship between the oil temperature and the pressure loss of the cooling oil, and the pressure loss for each on / off duty ratio of the electric oil pump. The pressure loss was derived and derived from the oil temperature detected by the storage unit that stores the relationship between the flow rate and the flow rate and the heat conductivity, and the oil temperature detected by the oil temperature detection unit using the relationship between the oil temperature and the pressure loss. By deriving the flow rate from the pressure loss using the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump, and by deriving the thermal conductivity using the relationship between the flow rate and the thermal conductivity using the derived flow rate. , The flow rate is saturated when the determination unit determines whether or not the flow rate exceeds the saturated minimum flow rate at which the increase in thermal conductivity is saturated, and when the determination unit determines whether the flow rate exceeds the saturated minimum flow rate. It is characterized by being provided with a control unit that adjusts the on / off duty ratio of the electric oil pump so that the minimum flow rate is maintained.

The flow control device for the electric oil pump according to the present invention is configured as described above, so that the determination unit cools based on the oil temperature of the cooling oil detected by the oil temperature detection unit and the table stored in the storage unit. When it is determined (estimated) that the oil flow rate exceeds the minimum saturated flow rate, the control unit adjusts (lowers) the on / off duty ratio of the oil pump so that the cooling oil flow rate can exert the maximum cooling capacity. Since the minimum saturated flow rate is maintained, it is possible to prevent the excessive cooling oil from being supplied to the motor while allowing the cooling oil to exert the maximum cooling capacity.

It is a figure which shows the structure of the motor cooling system which used the flow rate control device of the electric oil pump which concerns on this invention. It is a control block diagram of the flow rate control device of the electric oil pump which concerns on 1st Embodiment of this invention. It is explanatory drawing of the map stored in the storage part which comprises the flow rate control device of the electric oil pump which concerns on 1st Embodiment of this invention. It is a flowchart explaining the control flow by the flow rate control device of the electric oil pump which concerns on 1st Embodiment of this invention.

(Overall configuration of motor cooling system)
Hereinafter, the overall configuration of the motor cooling system using the flow control device for the electric oil pump according to the present invention will be described with reference to the drawings. In the following, as an example of a vehicle, a hybrid vehicle equipped with an internal combustion engine, two rotary electric motors (motors), a mechanical oil pump, an electric oil pump, and the like will be described.

FIG. 1 is a diagram showing a configuration of a motor cooling system using a flow control device for an electric oil pump according to the present invention, and shows a configuration of a motor cooling system 10 for a hybrid vehicle. The motor cooling system 10 includes a power unit 12 mounted on a hybrid vehicle.

The power unit 12 includes an engine (not shown) which is an internal combustion engine and a rotary electric machine 14 shown as a motor.

The rotary electric machine 14 is a motor generator (MG) mounted on a vehicle, and is a three-phase synchronous type that functions as a motor when power is supplied and as a generator when braking or being driven by an engine. It is a rotary electric machine. Here, it is assumed that the rotary electric machine 14 is mainly used as a drive motor for traveling a vehicle.

The case body 16 is a housing including a rotary electric machine 14 inside, and is also called a transaxle. In the internal space of the case body 16, cooling oil for lubricating the moving parts of the rotary electric machine 14 and cooling the rotary electric machine 14 is stored.

The motor cooling system 10 has a supply path 20 including an electric oil pump 18 as a cooling circuit for circulating and supplying cooling oil used for cooling the rotary electric machine 14 to be cooled. The electric oil pump 18 circulates and supplies cooling oil as a refrigerant to the internal space of the case body 16.

The electric oil pump 18 is configured to suck cooling oil from an oil pan (not shown) in which cooling oil is stored via a strainer 22. Specifically, the refrigerant intake path 24 is connected to the strainer 22 provided on the lower side of the case body 16, and the refrigerant intake path 24 is connected to the electric oil pump 18 on the downstream side of the strainer 22.

The supply path 20 includes an electric oil pump 18, a water-cooled cooler 26, a check valve 28, and a cooling pipe 30.

A temperature detection unit (not shown) is provided on the cooling oil circulation path until the cooling oil supplied from the electric oil pump 18 is discharged to the rotary electric machine 14 and returns to the electric oil pump 18 again. The installation location is suitable for the location where the oil temperature of the cooling oil is the highest on the cooling oil circulation path.

The electric oil pump 18 is an electric refrigerant pump driven by an electric motor 32 and driven and controlled by a control device 34. The control device 34 drives and controls the electric oil pump 18 by controlling the electric motor 32. The control device 34 can be configured with a computer suitable for mounting on a hybrid vehicle. The control device 34 may be a part of another control device mounted on the hybrid vehicle, for example, a control device that controls each element of the motor cooling system 10, or an integrated control device that controls the entire vehicle. ..

The water-cooled cooler 26 is a heat exchanger that exchanges heat between the cooling oil and the cooling water.

The check valve 28 is provided between the water-cooled cooler 26 and the cooling pipe 30, and has a function of preventing backflow of cooling oil on the outlet side of the electric oil pump 18. The cooling oil delivered by the electric oil pump 18 passes through the water-cooled cooler 26 and the check valve 28, and is pressure-fed to the cooling pipe 30.

The cooling pipe 30 is a flow path provided inside the case body 16 and is provided above the rotary electric machine 14 to be cooled, and discharges cooling oil to the rotary electric machine 14. As a result, the cooling oil cooled by the water-cooled cooler 26 is supplied to the rotary electric machine 14.

(First Embodiment)
(Overview of flow control of the flow control device of the electric oil pump)
Hereinafter, the flow rate control of the flow rate control device of the electric oil pump according to the first embodiment of the present invention will be described.

FIG. 2 is a control block diagram of a flow rate control device for an electric oil pump according to the first embodiment of the present invention.

The flow rate control device for the electric oil pump according to the first embodiment is composed of a combination of the control device 34 described with reference to FIG. 1 and the oil temperature sensor 36 described later.

The flow control device for the electric oil pump is a cooling oil discharged from the supply path 20 to the rotary electric machine 14 for the electric oil pump 18 that pumps the cooling oil for cooling the rotary electric machine 14 used in the vehicle into the supply path 20. Control the flow rate.

The oil temperature sensor 36 is an oil temperature detecting unit that detects the oil temperature of the cooling oil and outputs the oil temperature information. As described in FIG. 1, the cooling oil supplied from the electric oil pump 18 is the rotary electric machine 14. It is provided on the circulation path of the cooling oil until it is discharged to the electric oil pump 18 and returned to the electric oil pump 18, and the installation location is, for example, on the path of the supply path 20 from the discharge hole of the cooling pipe 30 to the rotary electric machine. Examples include the flight path of the cooling oil leading to 14, the inside of the rotary electric machine 14, the flow path of the cooling oil after the heat absorption by the rotary electric machine 14 is completed, the return path to the strainer 22, and the like.

The control device 34 includes a memory 40, a determination unit 38, and a control unit 42. However, the memory 40 or the determination unit 38 does not necessarily have to be a component of the control device 34, and may be configured to be externally connected to the control device 34.

The memory 40 has a map 1 showing the relationship between the oil temperature and the pressure loss, which will be described later in FIG. 3, and the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump (the electric motor 32 that drives the electric oil pump). It is a storage unit which stores the map 2 showing the above and the map 3 showing the relationship between the flow rate and the thermal conductivity.

Here, the on-off duty ratio is defined as "High" in the pulse period of the applied voltage applied to the electric motor 32 in the PWM (Pulse Width Modulation) control used for the motor control of the electric motor 32 that drives the electric oil pump 18. "The percentage of the state period. When the on / off duty ratio is increased, the rotation speed of the electric motor 32 increases, and the flow rate of the cooling oil pressure-fed from the electric oil pump 18 increases. On the contrary, when the on / off duty ratio is reduced, the rotation speed of the electric motor 32 is reduced, and the flow rate of the cooling oil pumped from the electric oil pump 18 is reduced.

When the determination unit 38 obtains the oil temperature information of the cooling oil from the oil temperature sensor 36, it accesses the memory 40, reads out the map 1, the map 2, and the map 3 described later in FIG. 3, and oils from the oil temperature information. The pressure loss is derived using the map 1 showing the relationship between the temperature and the pressure loss, and the flow rate is derived from the derived pressure loss using the map 2 showing the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump 18. Is derived, and the thermal conductivity is derived from the derived flow rate using the map 3 showing the relationship between the flow rate and the thermal conductivity. As a result, it is determined (estimated) whether or not the flow rate exceeds the saturated minimum flow rate value at which the increase in thermal conductivity is saturated, and the determination information is output. The minimum saturation flow rate value will be described later.

When the determination unit 38 determines that the flow rate of the cooling oil is estimated to exceed the saturated minimum flow rate value, the control unit 42 sets the cooling oil flow rate to the saturated minimum flow rate value based on the determination information. The on / off duty ratio of the electric motor 32 that drives the electric oil pump 18 is adjusted so as to be maintained.

(Explanation of the map held by the memory 40)
Next, the map stored in the memory 40 will be described.

FIG. 3 is an explanatory diagram of a map stored in a storage unit constituting a flow rate control device for an electric oil pump according to the first embodiment of the present invention.

FIG. 3A is a map 1 showing the relationship between the oil temperature of the cooling oil and the pressure loss. As shown in FIG. 3A, when the oil temperature of the cooling oil rises from T2 to T1, the pressure loss is in a relationship of decreasing from p2 to p1. The pressure loss of the cooling oil corresponds to the viscosity of the cooling oil, that is, as the oil temperature of the cooling oil rises, the viscosity of the cooling oil decreases.

FIG. 3B is a map 2 showing the relationship between the pressure loss of the cooling oil and the flow rate. FIG. 3B shows the relationship between the pressure loss of the cooling oil and the flow rate for each on / off duty ratio of the electric motor 32 that drives the electric oil pump 18.

In FIG. 3B, for example, when the on / off duty ratio is set to Y%, the flow rate when the pressure loss of the cooling oil is p2 becomes Q2, and when the pressure loss of the cooling oil decreases to p1, the flow rate becomes p1. It increases to Q1.

FIG. 3C is a table showing the relationship between the flow rate of cooling oil and the heat transfer coefficient. As shown in FIG. 3C, the heat transfer coefficient of the cooling oil increases as the flow rate increases until the flow rate of the cooling oil increases from 0 to Q2. Here, the heat transfer coefficient can be rephrased as the cooling capacity of the cooling oil, that is, until the flow rate of the cooling oil rises from 0 to Q2, the cooling capacity of the cooling oil increases as the flow rate increases. Rise.

However, in FIG. 3C, when the flow rate exceeds Q2, as shown by the dotted ellipse, the cooling capacity of the cooling oil does not increase even if the flow rate increases further, and the cooling oil enters the “saturation region”. When the cooling oil is continuously supplied to the rotary electric machine 14 at the flow rate entering the saturation region, excess cooling oil is supplied to the rotor (not shown) of the rotary electric machine 14, and the stirring resistance of the cooling oil by the rotor increases. On the contrary, it increases the power loss of the motor and damages the driving ability.

That is, when the flow rate of the cooling oil is Q2, the heat transfer coefficient of the cooling oil shows the highest value, the cooling capacity is the highest, and the minimum flow rate with the least burden on the rotary electric machine 14 in the saturation region. Therefore, this flow rate Q2 is referred to as a "saturation minimum flow rate value".

Therefore, in FIG. 3 (c), in order to reduce the flow rate of the cooling oil from Q1 to the saturated minimum flow rate value Q2, as shown in FIG. 3 (b), the on / off duty of the electric motor 32 for driving the electric oil pump 18 When the ratio is controlled to be lowered from Y% to X% (Y%> X%), it is estimated that the pressure loss of the cooling oil rises from p1 to p3, and the flow rate of the cooling oil changes from Q1 to Q2. It is estimated that it is decreasing.

(Details of flow control of the flow control device of the electric oil pump)
Next, the details of the flow rate control by the flow rate control device of the electric oil pump according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 4 is a flowchart illustrating a control flow by the flow rate control device of the electric oil pump according to the first embodiment of the present invention.

In FIG. 4, the oil temperature sensor 36 detects the oil temperature of the cooling oil and outputs the oil temperature information (S10).

When the determination unit 38 obtains the oil temperature information of the cooling oil from the oil temperature sensor 36, the determination unit 38 accesses the memory 40, and has the map 1 showing the relationship between the oil temperature stored in the memory 40 and the pressure loss described in FIG. , The map 2 showing the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump 18 and the map 3 showing the relationship between the flow rate and the thermal conductivity are read.

The determination unit 38 derives the pressure loss from the acquired oil temperature information using the map 1 showing the relationship between the oil temperature and the pressure loss (S12). For example, in the map 1 of FIG. 3A, when the acquired oil temperature information is the oil temperature T1, it is derived that the pressure loss is p1.

The determination unit 38 derives the flow rate from the pressure loss derived in S12 using the map 2 showing the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump 18 (S14). For example, in Map 2 of FIG. 3B, when the current on / off duty ratio of the electric oil pump 18 is Y%, if the pressure loss is p1, the flow rate is estimated to be Q1.

The determination unit 38 estimates the thermal conductivity from the flow rate estimated in S14 using the map 3 showing the relationship between the flow rate and the thermal conductivity, so that the flow rate Q1 is the saturated minimum flow rate at which the increase in the thermal conductivity is saturated. It is determined whether or not the value exceeds Q2 and is in the saturation region, and the determination information is output (S16).

In S16, according to the map 3 of FIG. 3C, it is estimated that the flow rate of the cooling oil is Q1, and when the determination unit 38 determines that the saturation minimum flow rate value Q2 is exceeded and outputs the determination information ( YES), the control unit 42 reduces the on / off duty ratio to X% (X% <Y%) in order to reduce the flow rate from the determined flow rate Q1 to the saturated minimum flow rate value Q2 based on the determination information. I presume it is necessary.

Then, the control unit 42 adjusts the on / off duty ratio of the electric motor 32 for driving the electric oil pump 18 to the estimated on / off duty ratio X% (S18), and the electric oil pump has the adjusted estimated on / off duty ratio X%. It drives the electric motor 32 of 18.

In S16, when the determination unit 38 determines that the flow rate of the cooling oil does not exceed the saturated minimum flow rate value Q2 and outputs the determination information (NO), the system returns to S10 and the cooling oil flow rate sets the saturated minimum flow rate value Q2. The steps S10 to S16 are repeated until the determination unit 38 determines that the value has been exceeded and outputs the determination information.

In S18, when the control unit 42 sets the on / off duty ratio to the estimated on / off duty ratio X% and drives the electric motor 32 of the electric oil pump 18, the flow rate is the saturated minimum flow rate value in FIG. 3 (b). If it is reduced and maintained in Q2, the pressure loss should have risen to p3, and from FIG. 3A, when the pressure loss is p3, the oil temperature should have risen to T3. Is.

Therefore, the control flow returns to S10, and the oil temperature sensor 36 continuously detects the oil temperature of the cooling oil. If the detected oil temperature is not T3 (higher than T3), it is presumed that the flow rate of the cooling oil is not maintained at the saturated minimum flow rate value Q2. The determination unit 38 processes the steps of S12, S14, and S16, and the control unit 42 sets the on / off duty ratio until the oil temperature detected by the oil temperature sensor 36 reaches the oil temperature corresponding to the saturated minimum flow rate value Q2. Adjust repeatedly.

As described above, the flow control device for the electric oil pump according to the present invention is the electric oil pump 18 that pumps the cooling oil for cooling the rotary electric machine 14 used in the vehicle into the supply path 20 from the supply path 20. It is a flow control device of an electric oil pump that controls the flow rate of the cooling oil discharged to 14, and shows the relationship between the oil temperature and the pressure loss of the oil temperature sensor 36 that detects the oil temperature of the cooling oil and the cooling oil. A memory that stores the map 1, the map 2 showing the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump (the electric motor 32 that drives the electric oil pump), and the map 3 showing the relationship between the flow rate and the thermal conductivity. From the oil temperature information detected by the oil temperature sensor 36 and 40, the pressure loss is derived using the map 1 showing the relationship between the oil temperature and the pressure loss, and the on / off duty ratio of the electric oil pump 18 is derived from the derived pressure loss. The flow rate is derived by deriving the flow rate using the map 2 showing the relationship between the pressure loss and the flow rate for each, and deriving the thermal conductivity from the derived flow rate using the map 3 showing the relationship between the flow rate and the thermal conductivity. , Judgment unit 38 that determines (estimates) whether or not the increase in thermal conductivity exceeds the saturated minimum flow rate value Q2 and outputs the determination information, and the cooling oil flow rate exceeds the saturated minimum flow rate value Q2. When the determination unit 38 determines that it is presumed to be, the electric motor that drives the electric oil pump 18 so that the flow rate of the cooling oil is maintained at the saturated minimum flow rate value Q2 based on the determination information. It is characterized by including a control unit 42 for adjusting the on / off duty ratio of 32.

10 motor cooling system, 12 power unit, 14 rotary electric machine (motor), 16 case body, 18 electric oil pump, 20 supply path (cooling pipe), 22 strainer, 24 refrigerant intake path, 26 water-cooled oil cooler (water-cooled cooler) ), 28 Check valve, 30 Cooling pipe, 32 Electric motor, 34 Control device, 36 Oil temperature sensor (oil temperature detection unit), 38 Judgment unit, 40 Memory (storage unit), 42 Control unit.

Claims (1)

Regarding an electric oil pump that pumps cooling oil for cooling a motor used in a vehicle into a cooling pipe, it is a flow control device for the electric oil pump that controls the flow rate of the cooling oil discharged from the cooling pipe to the motor. hand,
An oil temperature detection unit that detects the oil temperature of the cooling oil, and
A storage unit that stores the relationship between the oil temperature and the pressure loss, the relationship between the pressure loss and the flow rate for each on / off duty ratio of the electric oil pump, and the relationship between the flow rate and the thermal conductivity of the cooling oil. ,
The pressure loss is derived from the oil temperature detected by the oil temperature detecting unit using the relationship between the oil temperature stored in the storage unit and the pressure loss, and the derived pressure loss is used in the storage unit. The flow rate is derived using the relationship between the pressure loss and the flow rate for each on / off duty ratio of the stored electric oil pump, and the flow rate stored in the storage unit and the thermal conductivity are derived from the derived flow rate. By deriving the thermal conductivity using the relationship of the above, a determination unit for determining whether or not the flow rate exceeds the saturated minimum flow rate at which the increase in the thermal conductivity is saturated.
When the determination unit determines that the flow rate exceeds the saturation minimum flow rate, the control unit adjusts the on / off duty ratio of the electric oil pump so that the flow rate is maintained at the saturation minimum flow rate. ,
A flow control device for an electric oil pump, characterized by being equipped with.

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