Control device of electric vehicle

Abstract

To provide a control device of an electric vehicle that can prevent damages such as abrasion and burning-in of a tooth surface to secure reliability, even when using "low viscosity oil" whose loss can be reduced so that electricity consumption can be expected to improve.SOLUTION: A control device of an electric vehicle, which is loaded with a motor 1 as a driving force source and performs lubrication of the motor 1 and a gear wheel that transmits torque of the motor 1, with oil 7, when a temperature of oil 7 is above a predetermined temperature, restricts at least either of a torque climb gradient and a rotation speed climb gradient of the motor 1 to a predetermined gradient or less, when increasing output of the motor 1 in order to make an electric vehicle Ve accelerate and run (step S4).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for an electric vehicle that uses a motor as a driving force source and lubricates (lubricates and cools) the motor and gears with oil (lubricating oil). [Background technology]

[0002] Patent Document 1 describes a lubricating oil used to lubricate electric motors and transmissions. The lubricating oil described in Patent Document 1 is intended to lubricate both electric motors and transmissions with the same lubricating oil, and the composition and content of the lubricating oil are specified so that the lubricating oil has a good balance of properties such as electrical insulation, seizure resistance, copper corrosion prevention, and fatigue resistance. The lubricating oil described in Patent Document 1 has a kinematic viscosity of 4.0 to 20.0 mm at 40°C. 2 / s, and the kinematic viscosity of the lubricating oil at 100°C is 1.8 to 5.2 mm 2 / s.

[0003] Patent Document 2 describes a motor drive device that includes an electric motor, a reducer that reduces the rotation speed of the electric motor and transmits torque to wheels, and a lubricating oil supply mechanism that supplies lubricating oil to the reducer. The motor drive device described in Patent Document 2 is configured to limit the current of the electric motor, i.e., limit the output (maximum output) of the electric motor, when the temperature of the lubricating oil exceeds a threshold value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-172642 [Patent Document 2] Japanese Patent Application Publication No. 2017-17889 Summary of the Invention [Problem to be solved by the invention]

[0005] The lubricating oil described in Patent Document 1 is a so-called "low-viscosity oil" with a lower viscosity than the general lubricating oils used in conventional vehicles. Using such "low-viscosity oil" to lubricate the drive motor and gear transmission mechanism of an electric vehicle reduces losses due to the viscous resistance of the lubricating oil, thereby improving the electric vehicle's electrical energy efficiency, i.e., power consumption. However, as described in Patent Document 1, in an operating environment where the lubricating oil temperature exceeds 100°C, the kinematic viscosity of the lubricating oil decreases. This can cause oil film breakdown on the tooth surfaces, particularly in the lubrication of gears, leading to wear and seizure on the tooth surfaces. To address this issue, for example, the motor drive device described in Patent Document 2 limits the maximum output of the motor when the lubricating oil temperature exceeds a threshold, thereby suppressing the increase in lubricating oil temperature and the associated decrease in lubricating oil viscosity, thereby preventing the wear and seizure.

[0006] On the other hand, electric vehicles using such motors as a driving force source can take advantage of the motor's excellent characteristics, such as responsiveness and torque rise, to accelerate more nimbly than conventional general-purpose internal combustion engine vehicles. However, when accelerating an electric vehicle using such "low viscosity oil," the torque of the drive motor rises sharply due to acceleration, and the load on the gears that transmit the torque of the drive motor also increases sharply. Therefore, particularly when accelerating at high temperatures when the viscosity of the lubricating oil is reduced and the load on the gears increases sharply, the risk of wear and seizure of the tooth surfaces as described above increases.

[0007] This invention was devised with a focus on the above-mentioned technical problems, and aims to provide a control device for an electric vehicle that can prevent damage to the tooth surfaces, such as wear and seizure, and ensure reliability, even when using "low viscosity oil" that is expected to reduce losses and improve electricity efficiency. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a control device for an electric vehicle that is equipped with a motor as a driving force source, and in which the motor and gears that transmit the torque of the motor are each lubricated with oil, the control device comprising an oil temperature sensor that detects the temperature of the oil, and a control unit that controls the motor, wherein when the temperature detected by the oil temperature sensor is equal to or higher than a predetermined oil temperature, the control unit limits at least one of the torque increase gradient or rotation speed increase gradient of the motor to a predetermined gradient or less when increasing the output of the motor to accelerate the electric vehicle.

[0009] In addition, the oil temperature sensor in this invention may detect the temperature of the oil lubricating the reduction gear in the vicinity of the reduction gear that slows down the rotational speed of the motor, and the control unit in this invention may be configured to limit at least one of the torque increase gradient or the rotation speed increase gradient to below the predetermined gradient when the temperature detected in the vicinity of the reduction gear is equal to or higher than the predetermined oil temperature.

[0010] The control unit in the present invention may be configured to limit at least one of the torque increase gradient and the rotational speed increase gradient to 80% or less of the maximum increase gradient.

[0011] The oil in this invention is the same lubricating oil that is used for both the motor and the gears, and has a kinematic viscosity of 4.0 mm when the oil temperature is 100°C. 2 It may also be a low viscosity oil of 1 / s or less. [Effects of the Invention]

[0012] The electric vehicle controlled by this invention uses at least one motor as a driving force source and generates driving force by the motor's output torque. It may be an electric vehicle driven by the motor's output. Alternatively, it may be a hybrid vehicle that uses both a motor and an engine. The electric vehicle controlled by this invention uses oil to lubricate gears that transmit motor torque in, for example, a transmission or a reduction gear. The use of so-called "low-viscosity oil," which has a lower viscosity than conventional lubricating oils, for lubricating such gears or the gears and motor can improve the electric vehicle's fuel economy. However, since oil generally becomes less viscous as its temperature increases, if the load on the gears increases when the oil temperature is high, there is a risk of oil film breakdown on the tooth surfaces. In particular, electric vehicles that accelerate quickly using the motor's output torque face harsh conditions for the oil used to lubricate the gears. Therefore, in the control device for an electric vehicle of this invention, when the oil temperature is high and there is a risk of oil film breakdown, the motor torque increase rate or rotation speed increase rate is limited rather than limiting the motor output (maximum output), thereby avoiding oil film breakdown on the tooth surfaces. In other words, when the oil temperature is high, when the motor output torque is increased in response to an acceleration request from the electric vehicle, the increase in motor torque per hour or the increase in motor rotation speed per hour is limited. As a result, without limiting the maximum motor output, i.e., the maximum driving force of the electric vehicle due to the motor output, the load on the gears is reduced, easing the oil usage environment and preventing oil film breakdown on the tooth surfaces.

[0013] Therefore, according to the control device for an electric vehicle of this invention, when the oil temperature is high and the oil usage environment is severe, by limiting the rate of increase in motor torque or rotation speed, it is possible to avoid oil film breakdown on the tooth flanks and prevent damage to the tooth flanks such as wear and seizure. Furthermore, even when using "low viscosity oil" which is expected to reduce loss due to viscous resistance of the oil and improve power consumption, damage to the tooth flanks such as wear and seizure can be prevented, ensuring the reliability of the electric vehicle. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram for explaining the configuration of an electric vehicle to be controlled in the present invention, and is a diagram showing a schematic diagram of its drive system and control system. [Figure 2] FIG. 2 is a flowchart for explaining an example of control (an example of limiting the torque increase gradient of the motor) executed by the control device for an electric vehicle of the present invention. [Figure 3] FIG. 3 is a diagram showing an image of the torque increase gradient of the motor when the control shown in the flowchart of FIG. 2 is executed. [Figure 4] FIG. 4 is a flowchart for explaining another example of control (an example of limiting the rate of increase in the rotational speed of the motor) executed by the control device for an electric vehicle of the present invention. [Figure 5] FIG. 5 is a diagram showing an image of the torque increase gradient of the motor when the control shown in the flowchart of FIG. 4 is executed. [Figure 6] FIG. 6 is a flowchart for explaining another example of control (an example of sequentially limiting the torque increase gradient and the rotation speed increase gradient of the motor) executed by the control device for an electric vehicle of the present invention. [Figure 7] FIG. 7 is a flowchart for explaining another example of control executed by the control device for an electric vehicle of the present invention (an example in which the torque increase gradient and the rotation speed increase gradient of the motor are limited in parallel). DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of specific embodiments of the present invention and are not intended to limit the scope of the present invention.

[0016] An example of a drive system and control system of an electric vehicle to be controlled in an embodiment of the present invention is shown in Fig. 1. The electric vehicle (hereinafter referred to as vehicle) Ve shown in Fig. 1 is an electric vehicle equipped with a motor 1 as a driving power source (POWER). The vehicle Ve also includes a transaxle (T / A) 2, a detector 3, and a control unit (ECU) 4.

[0017] The vehicle Ve to be controlled in the embodiment of the present invention may be equipped with one or more motors (not shown) in addition to the motor 1 as a driving force source. Alternatively, the vehicle Ve may be a "hybrid vehicle" using the motor 1 and an engine (not shown) as driving force sources. Furthermore, as shown in FIG. 1 , the vehicle Ve may be a front-wheel drive vehicle in which the output torque of the motor 1 is transmitted to front wheels (drive wheels) 5 via a transaxle 2, a differential gear (not shown), or the like, to generate driving force at the front wheels 5. Alternatively, the vehicle Ve may be a rear-wheel drive vehicle (not shown) in which the output torque of the motor 1 is transmitted to rear wheels 6 via, for example, a propeller shaft (not shown), to generate driving force at the rear wheels 6. Alternatively, the vehicle Ve may be a four-wheel drive vehicle (not shown) provided with a transfer mechanism (not shown) to transmit the output torque of the motor 1 to both the front wheels 5 and the rear wheels 6, to generate driving force at both the front wheels 5 and the rear wheels 6.

[0018] The motor 1 is configured, for example, by a permanent magnet synchronous motor or an induction motor. The motor 1 at least functions as a prime mover that is driven by a supply of electric power and outputs torque. The motor 1 may also function as a generator that generates electric power when driven by external torque. That is, the motor 1 may be a so-called motor-generator that combines the functions of a prime mover and a generator. A battery (not shown) is connected to the motor 1 via an inverter (not shown). Therefore, electric power stored in the battery can be supplied to the motor 1, causing the motor 1 to function as a prime mover and output driving torque. The motor 1 can also function as a generator using torque transmitted from the drive wheels 5, and the regenerative power generated during this operation can be stored in the battery. The output speed and output torque of the motor 1 are electrically controlled by a control unit 4 (described later). For example, a required driving force is calculated from the amount of operation of an accelerator pedal (not shown) by the driver and the vehicle speed, and the output torque of the motor 1 is controlled based on the required driving torque (i.e., the control target value of the motor 1) set corresponding to the required driving force.

[0019] The transaxle 2 is a gear transmission mechanism that transmits the output torque of the motor 1 to the drive wheels 5. The transaxle 2 may be a reducer that reduces the rotational speed of the motor 1 to transmit the output torque. Alternatively, the transaxle 2 may be a transmission that changes the rotational speed of the motor 1 to transmit the output torque. Furthermore, a final reduction gear (not shown) and a differential gear of the vehicle Ve may be integrally incorporated into the transaxle 2. In either case, the transaxle 2 is a gear transmission mechanism and is equipped with "gears" (not shown) that transmit the output torque of the motor 1.

[0020] In the vehicle Ve according to an embodiment of the present invention, at least the "gears" of the transaxle 2 are lubricated (lubricated and cooled) by oil 7. For example, oil 7 having a well-balanced combination of properties such as electrical insulation, seizure resistance, copper corrosion prevention, and fatigue resistance, like the "lubricating oil" described in Patent Document 1, may be used to lubricate (lubricate and cool) the "gears" of the transaxle 2 as well as the motor 1. In other words, the same oil 7 may be used to lubricate both the motor 1 and the "gears" of the transaxle 2. Furthermore, by using a so-called "low-viscosity oil" developed to have a low kinematic viscosity as described in Patent Document 1, as the oil 7, loss due to viscous resistance of the oil 7 can be reduced, thereby improving the electric fuel efficiency of the vehicle Ve.

[0021] The detection unit 3 is a device or apparatus for acquiring various data and information required to control the vehicle Ve, and includes, for example, a power supply unit, a microcomputer, a sensor, an input / output interface, etc. The detection unit 3 in this embodiment of the present invention detects the running state and control state of the vehicle Ve, and in particular, detects the temperature of the oil 7.

[0022] Specifically, the detection unit 3 includes, for example, a wheel speed sensor 3a that detects the rotational speed of each wheel 5, 6, a motor torque sensor 3b that detects the torque of the motor 1, a motor rotation speed sensor (or resolver) 3c that detects the rotation speed of the motor 1, a motor current sensor 3d that detects the current value of the motor 1, an accelerator opening sensor 3e that detects the depression amount or depression angle of the accelerator pedal (not shown), and a timer 3f that detects the detection time and timing of each sensor or the control time of each part. The detection unit 3 also includes an oil temperature sensor 3g that detects the temperature of the oil 7 that lubricates the "gears" of the transaxle 2. The oil temperature sensor 3g may be provided at multiple locations to detect the temperature of the oil 7 generally or averagely. The oil temperature sensor 3g is particularly installed near the "gears" where the load increases during acceleration of the vehicle Ve, as described below, increasing the risk of damage such as wear and seizure. For example, oil temperature sensor 3g is installed near a "reduction gear" (not shown) that reduces the rotational speed of motor 1 to transmit torque, and detects the temperature of oil 7 that lubricates the "reduction gear." Detection unit 3 is electrically connected to control unit 4, which will be described later, and outputs electrical signals corresponding to detected or calculated values ​​of the various sensors, devices, and apparatuses described above to control unit 4 as detection data.

[0023] The control unit 4 is an electronic control device mainly composed of, for example, a microcomputer. The control unit 4 in this embodiment of the present invention controls the vehicle drive motor 1 to control the driving force of the vehicle Ve. Various data detected or calculated by the detection unit 3 described above are input to the control unit 4. The control unit 4 performs calculations using the input various data as well as pre-stored data and calculation formulas. The control unit 4 outputs the calculation results as a control command signal and is configured to control the driving force of the vehicle Ve using the output of the motor 1 as described above. In particular, the control device for an electric vehicle in this embodiment of the present invention controls the output of the motor 1 so as to limit the torque increase gradient or the rotation speed increase gradient of the motor 1 in accordance with the temperature of the oil 7 detected by the oil temperature sensor 3g, as will be described later.

[0024] Although FIG. 1 above shows an example in which one control unit 4 is provided, the control unit 4 in the embodiment of the present invention may be provided in multiple units, one for each device or equipment to be controlled, or one for each control content.

[0025] As described above, the control device for an electric vehicle according to the embodiment of the present invention is configured to prevent damage to the gears and ensure reliability, even when using low-viscosity oil to improve fuel economy. An example of the control executed by the control unit 4 for this purpose is shown in the flowchart of FIG.

[0026] The control shown in the flowchart of FIG. 2 is executed when the vehicle Ve is traveling. First, in step S1, it is determined whether the accelerator opening is equal to or greater than a predetermined value. That is, it is determined whether a large acceleration request is present and the load on the "gears" of the transaxle 2 is rapidly increasing. For example, it is determined whether the accelerator opening is 100%, that is, whether the vehicle Ve is in a WOT (Wide Open Throttle) state. Therefore, the predetermined value for determining the magnitude of the accelerator opening in step S1 is used to determine the state of the load on the "gears" of the transaxle 2, and may be 100%, which corresponds to a WOT state, as in the above example, or may be a predetermined value (e.g., 90%, 80%, etc.) calculated based on the results of experiments, simulations, etc.

[0027] If the accelerator opening is less than a predetermined value (for example, 100%) and the result of this step S1 is "No," it can be determined that a sudden increase in torque (a sudden increase in the load on the "gear") that could cause damage to the "gear" will not occur, so the routine shown in the flowchart of Figure 2 is temporarily terminated without executing any further control.

[0028] On the other hand, if the accelerator opening is greater than a predetermined value (for example, 100%) and the answer is "Yes" in step S1, it can be determined that there is a risk of damage such as wear or seizure of the "gears" due to a sudden increase in torque (a sudden increase in the load on the "gears"). In order to deal with this, control is executed in the next step S2 onwards.

[0029] In step S2, it is determined whether the oil temperature (temperature of the oil 7) is equal to or lower than a predetermined value. That is, it is determined whether there is a risk that the viscosity of the oil 7 will decrease as the temperature of the oil 7 increases, resulting in an oil film breakdown in the lubricated parts. For example, it is determined whether the temperature of the oil 7 is equal to or lower than 100°C. In this case, the predetermined value (temperature) is set in advance to a temperature (e.g., 90°C, 100°C, 120°C, etc.) at which the above-mentioned oil film breakdown of the oil 7 will not occur, based on the results of experiments, simulations, etc. Furthermore, in step S2, as described above, the determination is made based on oil temperature data detected in the vicinity of the "reduction gear" which is subjected to a particularly heavy load, thereby making it possible to reliably and appropriately grasp the risk of damage to the "gear" due to the above-mentioned oil film breakdown.

[0030] If the oil temperature is below the predetermined value and the answer to this step S2 is "Yes," it can be determined that there is no risk of damage to the "gear" due to oil film breakdown as described above, so the process proceeds to the next step S3, where normal control is carried out.

[0031] In step S3, the torque increase gradient (motor torque gradient) of the motor 1 is set to 100%. That is, the torque increase gradient of the motor 1 is set to the maximum (100%) increase gradient applied in normal control. For example, when the control unit 4 increases the output of the motor 1 in response to an acceleration request for the vehicle Ve, the control unit 4 controls the motor 1 based on a preset torque increase gradient (an increase in the output torque of the motor 1 per time). In this embodiment of the present invention, the (default) torque increase gradient set in normal times is an increase gradient of 100%, i.e., the maximum increase gradient.

[0032] In step S3, when the normal (100%) torque increase gradient is set, the routine shown in the flowchart of FIG. 2 is temporarily terminated.

[0033] On the other hand, if the oil temperature is above a predetermined value and the answer in step S2 is "No," it can be determined that there is a risk of damage to the "gear" due to the oil film running out as described above, so the process proceeds to step S4, and control is performed to avoid damage to the "gear."

[0034] In step S4, the torque increase gradient of the motor 1 (motor torque gradient) is limited to a predetermined value (gradient) or less. For example, as shown in FIG. 3, the torque increase gradient of the motor 1 (dashed line in FIG. 3) is limited to an increase gradient of 80% or less of the normal (unlimited) or maximum torque increase gradient (solid line in FIG. 3). In the control example shown in the flowchart of FIG. 2, the torque increase gradient of the motor 1 is limited to 50% to 80% of the normal (or maximum) increase gradient. The predetermined value (gradient) in this case is set in advance, for example, based on the results of experiments, simulations, etc., to an increase gradient that will not cause damage to the "gears" as described above.

[0035] In step S4, once the torque increase gradient for avoiding damage to the "gear" is set, the routine shown in the flowchart of FIG. 2 is temporarily terminated.

[0036] Other control examples executed by the control unit 4 in the embodiment of the present invention are shown in the flowcharts of Figures 4, 6 and 7. In the flowcharts of Figures 4, 6 and 7 below, control steps that have the same control content as those explained in the flowchart of Figure 2 above are assigned the same step numbers as in the flowchart of Figure 2.

[0037] In the control shown in the flowchart of Figure 4, if it is determined that there is a risk of the oil film on the "gear" running out, the rate at which the rotation speed of the motor 1 increases is limited to avoid damage to the "gear."

[0038] As with the control example shown in the flowchart of Figure 2 above, if the oil temperature is below a predetermined value and the answer to step S2 is "Yes," it can be determined that there is no risk of damage to the "gear" due to oil film breakdown as described above, so the process proceeds to the next step S13, and normal control is carried out.

[0039] In step S13, the rotation speed increase gradient of the motor 1 (motor rotation speed gradient) is set to 100%. That is, the rotation speed increase gradient of the motor 1 is set to the maximum (100%) increase gradient applied in normal control. For example, when the control unit 4 increases the output of the motor 1 in response to an acceleration request for the vehicle Ve, the control unit 4 controls the motor 1 based on a preset rotation speed increase gradient (the amount of increase in the rotation speed of the motor 1 per time). In this embodiment of the present invention, the (default) rotation speed increase gradient set in normal times is a 100% increase gradient, i.e., the maximum increase gradient.

[0040] In step S13, when the normal (100%) rotation speed increase gradient is set, the routine shown in the flowchart of FIG. 4 is temporarily ended.

[0041] On the other hand, as in the control example shown in the flowchart of Figure 2 above, if the oil temperature is above a predetermined value and the result of step S2 is "No," it can be determined that there is a risk of damage to the "gear" due to oil film breakdown as described above, so the process proceeds to step S14, and control is performed to avoid damage to the "gear."

[0042] In step S14, the rotational speed increase gradient of the motor 1 (motor rotational speed gradient) is limited to a predetermined value (gradient) or less. For example, as shown in FIG. 5, the rotational speed increase gradient of the motor 1 (dashed line in FIG. 5) is limited to an increase gradient of 80% or less of the normal (unlimited) or maximum rotational speed increase gradient (solid line in FIG. 5). In the control example shown in the flowchart of FIG. 4, the rotational speed increase gradient of the motor 1 is limited to 50% to 80% of the normal (or maximum) increase gradient. The predetermined value (gradient) in this case is set in advance, for example, based on the results of experiments, simulations, etc., to an increase gradient that will not cause damage to the "gears" as described above.

[0043] In step S14, once the rotation speed increase gradient for avoiding damage to the "gear" is set, the routine shown in the flowchart of FIG. 4 is temporarily ended.

[0044] In the control shown in the flowcharts of Figures 6 and 7, if it is determined that there is a risk of the oil film on a "gear" running out, the torque increase gradient and rotation speed increase gradient of motor 1 are both limited to avoid damage to that "gear."

[0045] The flowchart in Fig. 6 shows an example of controlling the output of the motor 1 by sequentially and continuously controlling the torque and rotation speed of the motor 1. Therefore, in the control example shown in the flowchart in Fig. 6, under normal circumstances (when it is determined that there is no risk of damage to the "gear"), the torque increase gradient of the motor 1 and the rotation speed increase gradient of the motor 1 are respectively set to the increase gradient under normal circumstances (100%) in steps S23 and S24. Note that the order of the above steps S23 and S24 may be reversed.

[0046] On the other hand, if it is determined that there is a risk of damage to the "gears," then in steps S25 and S26, the torque increase gradient of motor 1 and the rotational speed increase gradient of motor 1 are successively limited to 80% or less of the normal (or maximum) increase gradient. In the control example shown in the flowchart of FIG. 6, the torque increase gradient of motor 1 and the rotational speed increase gradient of motor 1 are each limited to an increase gradient between 50% and 80%. Note that the order of steps S25 and S26 above may be reversed.

[0047] The flowchart in Fig. 7 shows an example in which the torque and rotation speed of the motor 1 are controlled in parallel to control the output of the motor 1. Therefore, in the control example shown in the flowchart in Fig. 7, under normal circumstances (when it is determined that there is no risk of damage to the "gear"), the torque increase gradient of the motor 1 and the rotation speed increase gradient of the motor 1 are each set to the normal (100%) increase gradient in steps S33 and S34 in parallel.

[0048] On the other hand, if it is determined that there is a risk of damage to the "gears," the torque increase gradient of motor 1 and the rotational speed increase gradient of motor 1 are simultaneously limited to 80% or less of the normal (or maximum) increase gradient in steps S35 and S36. In the control example shown in the flowchart of Fig. 7, the torque increase gradient of motor 1 and the rotational speed increase gradient of motor 1 are each limited to an increase gradient between 50% and 80%.

[0049] As described above, in the electric vehicle control device according to the embodiment of the present invention, when the temperature of the oil 7 lubricating the motor 1 and the transaxle 2 is high and there is a risk of oil film breakdown, particularly in the lubricated portions of the "gears," the torque increase rate of the motor 1, the rotational speed increase rate of the motor 1, or both are limited (the maximum output of the motor 1 is not limited) to prevent oil film breakdown on the tooth surfaces of the "gears." In other words, when the temperature of the oil 7 increases and the viscosity of the oil 7 decreases, for example, when the output torque of the motor 1 is increased in response to an acceleration request for the vehicle Ve, the increase in motor torque per unit time or the increase in motor rotational speed per unit time is limited. Therefore, without limiting the maximum output of the motor 1, i.e., the maximum driving force of the vehicle Ve due to the output of the motor 1, the load on the "gears" is reduced, easing the operating environment of the oil 7 and preventing oil film breakdown on the tooth surfaces.

[0050] Therefore, according to the control device for an electric vehicle in an embodiment of the present invention, when the temperature of the oil 7 is high and the environment in which the oil 7 is used is harsh, by limiting at least one of the torque increase gradient or the rotation speed increase gradient of the motor 1, it is possible to avoid oil film breakdown on the tooth surfaces and prevent damage to the "gears" such as wear and seizure. Furthermore, even when "low viscosity oil" is used, which is expected to reduce loss due to the viscous resistance of the oil 7 and improve power efficiency, damage to the tooth surfaces such as wear and seizure can be prevented, ensuring the reliability of the electric vehicle Ve. [Explanation of symbols]

[0051] 1 Motor (driving force source: POWER, MOTOR) 2 Transaxle (gear: T / A) 3. Detection unit 3a (detection part) wheel speed sensor 3b Motor torque sensor (detection section) 3c (detection part) motor rotation speed sensor 3d Motor current sensor (detection section) 3e Accelerator opening sensor (detection section) 3f (detector) timer 3g Oil temperature sensor (detection part) 4 Control Unit (ECU) 5 Drive wheels (front wheels) 6 rear wheels 7 Oil (low viscosity oil) Vehicle (electric vehicle)

Claims

1. A control device for an electric vehicle that is equipped with a motor as a driving force source and that uses oil to lubricate the motor and gears that transmit torque of the motor, an oil temperature sensor for detecting the temperature of the oil; a control unit for controlling the motor; The control unit When the temperature detected by the oil temperature sensor is equal to or higher than a predetermined oil temperature, When increasing the output of the motor to accelerate the electric vehicle, at least one of the torque increase gradient and the rotation speed increase gradient of the motor is limited to a predetermined gradient or less. A control device for an electric vehicle.

2. The control device for an electric vehicle according to claim 1, The oil temperature sensor detecting the temperature in the vicinity of a reduction gear that reduces the rotational speed of the motor; The control unit When the temperature detected in the vicinity of the reduction gear is equal to or higher than the predetermined oil temperature, At least one of the torque increase gradient and the rotation speed increase gradient is limited to be equal to or less than the predetermined gradient. A control device for an electric vehicle.

3. The control device for an electric vehicle according to claim 2, The control unit At least one of the torque increase gradient and the rotational speed increase gradient is limited to 80% or less of the maximum increase gradient. A control device for an electric vehicle.

4. The control device for an electric vehicle according to any one of claims 1 to 3, The oil is The kinematic viscosity at an oil temperature of 100°C is 4.0 mm ２ / s or less A control device for an electric vehicle.

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