Control device for unit, control method for unit, and program

Abstract

[Problem] To enhance operation efficiency of an electric oil pump. [Solution] A control device for a unit which has a driving source for applying driving force to a driving wheel and an electric oil pump driven by a power source different from said driving source, the control device having a control unit for intermittently stopping the electric oil pump when a load on the driving source is smaller than a predetermined load.

Description

Unit control device, unit control method, and program

[0001] The present invention relates to a control device for a unit, a control method for a unit, and a program.

[0002] Patent Document 1 discloses a powertrain unit for an engine vehicle in which an electric oil pump driven by the engine supplies oil for operating a continuously variable transmission and hydraulic friction engagement elements. Patent Document 2 discloses a powertrain unit for an electric vehicle in which an electric oil pump driven by a dedicated electric motor supplies oil for lubrication and cooling.

[0003] JP 2021-116874 A International Publication No. 2023 / 277058

[0004] When the purpose is lubrication or cooling, a large hydraulic pressure (flow rate) is not required as when operating a continuously variable transmission or hydraulic engagement element, and a relatively low flow rate of oil is sufficient, so the load on the electric oil pump is low. However, electric oil pumps are inefficient under low load conditions.

[0005] The present invention has been made in view of the above problems, and has an object to improve the operating efficiency of an electric oil pump.

[0006] According to one aspect of the present invention, there is provided a control device for a unit having a drive source that applies drive force to drive wheels and an electric oil pump that is driven by a power source separate from the drive source, the control device having a control unit that intermittently stops the electric oil pump when the load on the drive source is smaller than a predetermined load.

[0007] According to the above aspect, when the load on the drive source (for example, output torque) is low, the flow rate of oil required for lubrication is low, and the oil film formed by the oil supplied to each location lasts for a certain period of time (i.e., the lubricated state continues until the oil film disappears), so the electric oil pump is stopped for intermittent periods. As a result, even when the load on the drive source is low and the efficiency of the electric oil pump is low, the energy loss of the electric oil pump is zero during the stopped periods, and the operating efficiency of the electric oil pump is improved.

[0008] FIG. 1 is a schematic diagram showing the main parts of a vehicle. FIG. 2 is a diagram showing a lubrication and cooling path of a unit. FIG. 3 is an explanatory diagram of the efficiency of an electric oil pump. FIG. 4 is a flowchart showing an example of control performed by a controller. FIG. 5 is a diagram showing an example of a timing chart corresponding to FIG. 4. FIG. 6 is an explanatory diagram of a modified example of intermittent stop control.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] 1 is a schematic diagram showing the main parts of a vehicle. Unit 1 is mounted on the vehicle and includes a motor 10 as a drive source that applies driving force to drive wheels 6, a speed reduction mechanism 20 that reduces the rotation speed from motor 10 and outputs it, a differential gear 30 that distributes the power transmitted from motor 10 via speed reduction mechanism 20 to the left and right drive wheels 6, a housing 40 that accommodates motor 10, speed reduction mechanism 20, and differential gear 30, and bearings 51 to 56 held in housing 40.

[0011] Motor 10 is a rotating electric machine and includes rotor 11, stator 12 that houses rotor 11, and rotating shaft 13 that rotates integrally with rotor 11. Stator 12 has coil ends 12a at both ends in the axial direction of motor 10, and rotating shaft 13 is supported by bearings 51 and 52 that are arranged on both sides of rotor 11 in the axial direction.

[0012] The reduction mechanism 20 is a gear mechanism and includes a first gear 21, a second gear 22, a third gear 23, and a fourth gear 24 arranged parallel to each other, and a shaft 25 on which the second gear 22 and the third gear 23 are mounted.

[0013] The first gear 21 is connected downstream (on the power output side) of the motor 10 and rotates integrally with the rotary shaft 13. The second gear 22 meshes with the first gear 21 and constitutes a first reduction gear stage together with the first gear 21. The second gear 22 rotates integrally with a shaft 25, which is supported at both ends by bearings 53 and 54.

[0014] The third gear 23 is connected downstream of the second gear 22 and rotates integrally with the shaft 25. The fourth gear 24 meshes with the third gear 23 and constitutes a second reduction gear stage together with the third gear 23. The fourth gear 24 is a final gear and is provided in the differential gear 30.

[0015] The differential gear 30 is a differential gear mechanism and has a differential case 31 that rotates integrally with the fourth gear 24. The differential case 31 is supported by bearings 55 and 56 and houses a differential portion that distributes the power input to the differential case 31 to the left and right drive wheels 6.

[0016] The housing 40 has a partition wall 41 that divides the interior of the housing 40. In the unit 1, the portion on the motor 10 side of the partition wall 41 (left side in FIG. 1 ) constitutes a motor section 1a that houses the motor 10, and the portion on the speed reduction mechanism 20 and differential gear 30 side of the partition wall 41 (right side in FIG. 1 ) constitutes a gear box section 1b that houses the speed reduction mechanism 20 and differential gear 30.

[0017] 2 is a diagram showing the lubrication and cooling paths of unit 1. Unit 1 further includes: an electric oil pump 2 having an electric motor 2a as a power source separate from motor 10 as a drive source, and an oil pump 2b driven by electric motor 2a; an inverter 3 that converts DC power from a battery into AC power and supplies it to electric motor 2a; a heat exchanger 4 that exchanges heat between coolant W and oil OL as a cooling medium; and a controller 5 that controls unit 1.

[0018] In the electric oil pump 2, an electric motor 2a receives power from an inverter 3 to drive an oil pump 2b. The electric oil pump 2 is connected to the motor section 1a and the gear box section 1b via a heat exchanger 4, draws oil OL from an oil reservoir section 42 of a housing 40 through a strainer 60, and supplies the drawn oil OL to the motor section 1a and the gear box section 1b.

[0019] In the motor section 1a, the oil OL from the electric oil pump 2 flows through the rotor 11 and the coil ends 12a in this order, and then returns to the oil reservoir 42. The rotor 11 and the coil ends 12a are cooled by the supplied oil OL.

[0020] In the gearbox section 1b, the oil OL from the electric oil pump 2 is distributed to the bearing section BRG including the bearings 51 to 56, the meshing portion E1 of the first gear 21 and the second gear 22, the meshing portion E2 of the third gear 23 and the fourth gear 24, and the differential gear 30, and after lubricating and cooling these, returns to the oil reservoir 42. The motor section 1a and the gearbox section 1b are also lubricated or cooled by the oil OL being scooped up in the oil reservoir 42 (scooped up by gears such as the fourth gear 24).

[0021] The heat exchanger 4 receives the oil OL from the electric oil pump 2 and the coolant W from the water pump 70, and the oil OL introduced into the heat exchanger 4 exchanges heat with the coolant W before being supplied to the motor section 1a and the gearbox section 1b. In the heat exchanger 4, when the temperature of the oil OL is higher than the temperature of the coolant W, the oil OL is cooled by the coolant W.

[0022] Coolant W from water pump 70 flows through inverter 80 for motor 10, stator 12, and heat exchanger 4 in this order, and then returns to water pump 70. The circulation path for coolant W may further include a battery, etc. In motor 10, oil OL supplied from electric oil pump 2 cools rotor 11 and coil ends 12a, and coolant W supplied from water pump 70, which is a pump separate from electric oil pump 2, cools stator 12.

[0023] In other words, a coolant cooling system separate from the oil OL is added to the motor 10, and the motor 10 is also cooled by the coolant W. The coolant cooling system is configured to constantly flow the amount of coolant W required for the entire vehicle when the system is operating.

[0024] The controller 5 performs control by executing a program stored in a ROM or RAM using a CPU. The program may be stored in a non-transitory storage medium such as a CD-ROM. The controller 5 is composed of one or more computers (microcomputers) equipped with a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 5 may be composed of multiple controllers.

[0025] The controller 5 receives signals from a pump rotation speed sensor 91 for detecting the pump rotation speed Nep, which is the rotation speed of the electric oil pump 2, a motor rotation speed sensor 92 for detecting the motor rotation speed Nmot, which is the rotation speed of the motor 10, an accelerator opening sensor 93 for detecting the accelerator opening APO, a vehicle speed sensor 94 for detecting the vehicle speed VSP, and the like.

[0026] The controller 5 controls the inverter 3 to control the electric motor 2a of the electric oil pump 2. The controller 5 further controls the inverter 80 to control the motor 10. The controller 5 has map data in which a torque command value for the motor 10 is set in advance according to the vehicle speed VSP and the accelerator opening APO, and controls the inverter 80 based on the torque command value read from the map data to control the motor torque Tmot, which is the output torque of the motor 10.

[0027] The motor 10 may be controlled by a controller separate from the controller 5. The water pump 70 is an electric water pump, and is controlled by a controller of a coolant cooling system separate from the controller 5.

[0028] When oil OL is supplied by the electric oil pump 2 for the purpose of lubrication or cooling, it is sufficient to supply a relatively low flow rate of oil OL, so the load on the electric oil pump 2 is low. However, the efficiency ηep of the electric oil pump 2 is poor when the load is low.

[0029] 3 is a diagram illustrating the efficiency ηep of the electric oil pump 2. In this example, the vehicle is accelerated between times T1 and T2, passes through a high-speed steady running state between times T2 and T3, is decelerated between times T3 and T4, and comes to a stop at time T4.

[0030] During acceleration between timings T1 and T2 and during deceleration between timings T3 and T4, a larger amount of oil OL is required for lubrication than during high-speed steady driving between timings T2 and T3, and therefore the discharge flow rate FLep of the electric oil pump 2 is also larger. On the other hand, before timing T1, the vehicle is running at a low speed, and a smaller amount of oil OL is required for lubrication than during acceleration, deceleration, and high-speed steady driving, so the discharge flow rate FLep of the electric oil pump 2 is small.

[0031] Therefore, during low-speed steady-state running before timing T1, the load on the electric oil pump 2 is lower than during acceleration, deceleration, and high-speed steady-state running. However, in this case, as shown in Figure 3, the efficiency ηep of the electric oil pump 2 is also lower than in these cases. In other words, when the electric oil pump 2 is in a low-load state, the efficiency ηep deteriorates.

[0032] Therefore, in this embodiment, the controller 5 performs the control described below.

[0033] 4 is a flowchart showing an example of control performed by the controller 5. By executing the process of this flowchart, the controller 5 functions as a control unit that executes the process (i.e., has a control unit that executes the process). Hereinafter, the electric oil pump 2 will also be simply referred to as the electric pump 2.

[0034] In this flowchart, the processing from steps S1 to S10 performs intermittent stop control to intermittently stop the electric oil pump 2. In step S1, it is determined whether the absolute value of the motor output Pmot, which is the output of the motor 10, is equal to or less than a predetermined value α, that is, it is determined whether the magnitude of the motor output Pmot is equal to or less than a predetermined value α as a predetermined load, thereby determining whether the load on the drive source is equal to or less than a predetermined load.

[0035] The magnitude of the motor output Pmot is an example of the load of the drive source, and can be calculated by multiplying the motor rotation speed Nmot by the motor torque Tmot. The load of the drive source may be the magnitude of the motor torque Tmot or the output torque (torque at the drive wheels 6). The output torque can be calculated by multiplying the motor torque Tmot by the gear ratio of the gearbox unit 1b. The predetermined value α is a judgment value for determining whether the electric pump 2 is in a low load state, and is set in advance. If the magnitude of the motor output Pmot is the predetermined value α, this may be included in the case of a negative judgment in step S1.

[0036] If the determination in step S1 is affirmative, it is determined that the electric pump 2 is in a low load state. In this case, the process proceeds to step S2, where it is determined whether the electric pump 2 is stopped. Whether the electric pump 2 is stopped can be determined, for example, by whether the pump rotation speed Nep is lower than a predetermined value. If the determination in step S2 is affirmative, it is determined that the electric pump 2 is stopped, and the process proceeds to step S3.

[0037] In step S3, it is determined whether the count value of the first timer TM1 is equal to or less than a predetermined value C1. The first timer TM1 is a timer for measuring the stop time of the electric pump 2, and is functionally realized by the controller 5. The predetermined value C1 is a value for setting the stop time period of the electric pump 2, and is set in advance.

[0038] If the determination in step S3 is affirmative, it is determined that the electric pump 2 is currently stopped, and the process proceeds to step S4 and then step S5. In step S4, the first timer TM1 counts, and the count value of the first timer TM1 is incremented. In step S5, the electric pump 2 continues to be stopped. After step S5, the process temporarily ends.

[0039] Thereafter, the processes of steps S1 to S5 are repeated while the count value of the first timer TM1 does not exceed the predetermined value C1. On the other hand, when the count value of the first timer TM1 exceeds the predetermined value C1, a negative determination is made in step S3, and it is determined that the stop period of the electric pump 2 has ended. In this case, the process proceeds to step S6, where the electric pump 2 is operated. After step S6, the process temporarily ends.

[0040] Thereafter, if the magnitude of the motor output Pmot is equal to or less than the predetermined value α, an affirmative determination is made in step S1, followed by a negative determination in the following step S2. In this case, the process proceeds to step S7, where it is determined whether the count value of the second timer TM2 is equal to or less than a predetermined value C2. The second timer TM2 is a timer for measuring the operating time of the electric pump 2, and is functionally realized by the controller 5. The predetermined value C2 is a value for setting the operating period of the electric pump 2, and is set in advance.

[0041] If the determination in step S7 is affirmative, it is determined that the electric pump 2 is in operation, and the process proceeds to step S8 and then step S9. In step S8, the second timer TM2 counts, and the count value of the second timer TM2 is incremented. In step S9, the operation of the electric pump 2 continues. After step S9, the process temporarily ends.

[0042] Thereafter, if the magnitude of the motor output Pmot is equal to or less than the predetermined value α and the count value of the second timer TM2 is equal to or less than the predetermined value C2, the processes of steps S1, S2, S7, S8, and S9 are repeatedly executed. On the other hand, if the count value of the second timer TM2 exceeds the predetermined value C2, a negative determination is made in step S7, and it is determined that the operation period of the electric pump 2 has ended. In this case, the process proceeds to step S10, where the electric pump 2 is stopped. After step S10, the process temporarily ends.

[0043] Thereafter, while the magnitude of the motor output Pmot is equal to or less than the predetermined value α, the electric pump 2 is alternately operated and stopped. In other words, when the magnitude of the motor output Pmot is smaller than the predetermined value α, the electric pump 2 is intermittently stopped.

[0044] On the other hand, if the magnitude of the motor output Pmot becomes greater than the predetermined value α, a negative determination is made in step S1, and it is determined that the electric pump 2 is not in a low load state. In this case, the process proceeds to step S11, where the operation of the electric pump 2 continues. In other words, when the magnitude of the motor output Pmot is greater than the predetermined value α, the electric pump 2 is continuously driven. After step S11, the process temporarily ends.

[0045] 5 is a diagram showing an example of a timing chart corresponding to FIG. 4. At timing T11, the electric pump 2 starts operating, and a discharge flow rate FLep of the electric pump 2 is generated. As a result, from timing T11, oil OL is supplied from the electric pump 2 to the gear box section 1b, and the gear temperature of the gear box section 1b decreases. Note that oil OL is also supplied to the motor section 1a, and the efficiency ηep of the electric pump 2 becomes as shown in the diagram.

[0046] Between timings T11 and T12, the vehicle is traveling at a steady low speed, and the magnitude of the motor output Pmot is smaller than the predetermined value α. Therefore, from timing T11, the second timer TM2 starts counting, and the count value of the second timer TM2 increases. In other words, this is the period during which the electric pump 2 is operating.

[0047] Thereafter, when the count value of the second timer TM2 exceeds the predetermined value C2, the operation period of the electric pump 2 ends, and the electric pump 2 is stopped. As a result, the discharge flow rate FLep and the efficiency ηep become zero. Furthermore, when the operation period of the electric pump 2 ends, the first timer TM1 starts counting, and the count value of the first timer TM1 increases. In other words, the electric pump 2 is in a stopped period.

[0048] During the stopped period, the power consumption (energy) of the electric pump 2 is reduced, and the energy loss of the electric pump 2 becomes zero. Meanwhile, during the stopped period, oil OL is no longer supplied from the electric pump 2 to the gear box portion 1b, so the gear temperature rises. Thereafter, when the count value of the first timer TM1 exceeds a predetermined value C1, the stopped period of the electric pump 2 ends and the electric pump 2 is operated. As a result, a discharge flow rate FLep is generated, and the efficiency ηep of the electric pump 2 becomes as shown in the figure.

[0049] Thereafter, while the magnitude of the motor output Pmot is equal to or less than the predetermined value α, the electric pump 2 is repeatedly activated and stopped based on the count values ​​of the first timer TM1 and the second timer TM2. In other words, the electric pump 2 is intermittently stopped. As a result, even when the magnitude of the motor output Pmot is smaller than the predetermined value α and the efficiency ηep is poor, the energy loss of the electric pump 2 becomes zero during the stopped period, and the operating efficiency of the electric pump 2 (the overall efficiency ηep of the electric pump 2) is improved.

[0050] When the electric pump 2 is stopped intermittently, the discharge flow rate FLep during the operation period is increased for cooling purposes compared to when the electric pump 2 is not stopped intermittently (see FIG. 3 ). However, compared to the case of FIG. 3 , the discharge flow rate FLep during the operation period is increased within a range that does not deteriorate the operating efficiency of the electric pump 2, so the operating efficiency of the electric pump 2 is improved compared to the case of FIG. 3 even if the discharge flow rate FLep is increased.

[0051] For example, if the motor 10 is cooled only by the oil OL supplied from the electric pump 2, the amount of oil required to cool the motor 10 often increases, and the number of opportunities to intermittently stop the electric pump 2 decreases.

[0052] Meanwhile, as mentioned above, a coolant cooling system separate from the oil OL is attached to the motor 10. Therefore, when the magnitude of the motor output Pmot is smaller than the predetermined value α and the heat generation amount of the motor 10 is small, it is possible to cool the motor 10 using only the coolant W, thereby increasing the number of opportunities to intermittently stop the electric pump 2 and improving the operating efficiency of the electric pump 2. Note that the coolant W generally flows continuously at a flow rate required for the entire vehicle when the system is operating, and there is often some surplus, so even if the coolant W is used to cool the motor 10, the efficiency of the entire vehicle will not decrease significantly.

[0053] The period between timings T12 and T13 is the period of acceleration, and the vehicle speed VSP and the motor output Pmot increase from timing T12 onwards. When the magnitude of the motor output Pmot exceeds a predetermined value α, the electric pump 2 leaves the low load state, and the efficiency ηep of the electric pump 2 increases compared to when it is in the low load state.

[0054] Therefore, even if the count value of the second timer TM2 exceeds the predetermined value C2 between timings T12 and T13, the electric pump 2 is not stopped intermittently but is driven continuously. Therefore, the first timer TM1 does not count. If the count value of the second timer TM2 exceeds the predetermined value C2 and reaches a full count while the magnitude of the motor output Pmot is greater than the predetermined value α, the second timer TM2 is left as it is.

[0055] Even when the magnitude of the motor output Pmot is greater than the predetermined value α, it is possible to perform intermittent stop control of the electric pump 2. However, when the magnitude of the motor output Pmot is greater than the predetermined value α, the amount of lubrication required in the gear box 1b increases, and the electric pump 2 can be driven efficiently.

[0056] Therefore, in this case, the electric pump 2 is not stopped intermittently, but is driven continuously, thereby ensuring the supply of oil OL when a large amount of lubrication is required, and also suppressing the rise in gear temperature.

[0057] Between times T13 and T14, the vehicle is traveling at a steady high speed, and the magnitude of the motor output Pmot is greater than the predetermined value α. Therefore, in this case as well, the required amount of lubrication is large, and the electric pump 2 can be driven efficiently, so the operation of the electric pump 2 continues.

[0058] The period between times T14 and T15 is the period during which the vehicle is decelerating, and from time T14 onwards, the motor output Pmot begins to decrease. After the motor output Pmot falls below the predetermined value α, it passes through a low-load period during which it becomes a negative value of the predetermined value α, and then falls below the negative value of the predetermined value α. In other words, during deceleration, the motor output Pmot temporarily passes through a low-load period before it falls below the negative value of the predetermined value α and becomes greater than the predetermined value α in absolute value.

[0059] 4 is temporarily stopped and the intermittent stop control is temporarily disabled until a predetermined time has elapsed from the start of deceleration. As a result, during deceleration when the motor output Pmot falls below the negative value of the predetermined value α and exceeds the predetermined value α in absolute value, the electric pump 2 can be continuously driven without being stopped by the intermittent stop control during the low load period.

[0060] From timing T15, the vehicle comes to a stop, and the motor output Pmot becomes zero. At timing T15, the electric pump 2 is stopped based on the count value of the second timer TM2, and the first timer TM1 starts counting. Thereafter, while the magnitude of the motor output Pmot is equal to or less than the predetermined value α, the electric pump 2 is repeatedly activated and stopped based on the count values ​​of the first timer TM1 and the second timer TM2, and the electric pump 2 is stopped intermittently. As a result, the operating efficiency of the electric pump 2 is improved.

[0061] The electric pump 2 may be stopped intermittently as follows.

[0062] 6 is an explanatory diagram of a modified example of intermittent stop control. In this example, the discharge flow rate FLep of the electric pump 2 is set to the sum of the required flow rate of the motor unit 1a and the required flow rate of the gearbox unit 1b. As a result, in this example, the discharge flow rate FLep of the electric pump 2 becomes zero between timings T21 and T22 and between timings T25 and T26, and the electric pump 2 is stopped intermittently.

[0063] As shown in this example, the electric pump 2 does not need to be stopped intermittently, but rather the stop period (between timings T21 and T22 and between timings T25 and T26) and the operation period (between timings T22 and T25 and between timings T26 and T27) may be constant. In addition, the discharge flow rate FLep does not need to be constant during the operation period, as shown between timings T22 and T25, and may vary during the operation period, as shown between timings T22 and T25 and between timings T26 and T27.

[0064] Next, the main effects of the controller 5 will be described.

[0065] (1) The controller 5 is a control device for a unit 1 having a motor 10 as a drive source that applies drive force to the drive wheels 6 and an electric oil pump 2 driven by an electric motor 2 a that is a power source separate from the motor 10, and the controller 5 intermittently stops the electric oil pump 2 when the magnitude of the motor output Pmot as a load on the drive source is smaller than a predetermined value α as a predetermined load.

[0066] According to this configuration, when the magnitude of the motor output Pmot is smaller than the predetermined value α, the flow rate of the oil OL required for lubrication is low, and the oil film formed by the oil OL supplied to various locations will last for a certain period of time (in other words, the lubricated state will continue until the oil film is gone), so the electric oil pump 2 is stopped intermittently. As a result, even when the magnitude of the motor output Pmot is smaller than the predetermined value α and the efficiency ηep of the electric oil pump 2 is poor, the energy loss of the electric oil pump 2 is zero during the stopped period, and the operating efficiency of the electric oil pump 2 is improved.

[0067] (2) The controller 5 continuously drives the electric oil pump 2 when the magnitude of the motor output Pmot is greater than the predetermined value α.

[0068] According to this configuration, when the magnitude of the motor output Pmot is greater than a predetermined value α, the amount of lubrication required in the gearbox section 1b increases, and the electric oil pump 2 can be driven efficiently.Therefore, by driving the electric oil pump 2 continuously without intermittently stopping the electric oil pump 2, the supply amount of oil OL can be secured when the amount of lubrication required is large.

[0069] (3) The motor 10 is configured to be cooled by the oil OL supplied from the electric oil pump 2 and the cooling water W supplied from the water pump 70 , which is a pump separate from the electric oil pump 2 .

[0070] According to this configuration, by adding a coolant cooling system separate from the oil OL to the motor 10, when the magnitude of the motor output Pmot is smaller than a predetermined value α and the heat generation amount of the motor 10 is small, it becomes possible to cool the motor 10 using only the coolant W, thereby increasing the opportunities for intermittent stopping of the electric oil pump 2 and improving the operating efficiency of the electric oil pump 2.

[0071] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0072] 1: Unit 2: Electric oil pump 2a: Electric motor (power source) 6: Drive wheel 5: Controller (unit control device, control section) 10: Motor (drive source) OL: Oil Pmot: Motor output (absolute value is the load on the drive source) W: Cooling water α: Predetermined value (predetermined load)

Claims

1. A control device for a unit having a drive source that applies drive force to drive wheels and an electric oil pump that is driven by a power source separate from the drive source, the control device having a control unit that intermittently stops the electric oil pump when the load on the drive source is smaller than a predetermined load.

2. A control device for a unit according to claim 1, wherein the control unit continuously drives the electric oil pump when the load on the drive source is greater than the predetermined load.

3. A control device for a unit according to claim 1, wherein the drive source is configured to be cooled by oil supplied from the electric oil pump and cooling water supplied from a pump separate from the electric oil pump.

4. A control method for a unit having a drive source that applies drive force to drive wheels and an electric oil pump that is driven by a power source separate from the drive source, the control method including intermittently stopping the electric oil pump when the load on the drive source is smaller than a predetermined load.

5. A program executable by a computer of a control device for a unit having a drive source that applies drive force to drive wheels and an electric oil pump that is driven by a power source separate from the drive source, the program including intermittently stopping the electric oil pump when the load on the drive source is smaller than a predetermined load.

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