Control device

Abstract

Control device comprising: a PWM generation unit that outputs a PWM drive signal to an inverter; and a torque limiting unit that outputs a torque command after limitation to the PWM generation unit based on a torque command from a higher-level control unit and a motor temperature, characterized in that the torque limiting unit a torque limiting factor calculation unit that calculates a torque limiting factor based on the engine temperature, and a post-limit torque calculation unit that outputs the post-limit torque command to the PWM generation unit based on the torque command from the higher-level control unit and the torque limit factor output from the torque limit factor calculation unit, wherein the torque limiting factor calculation unit limits an output torque of a motor based on the motor temperature in a case where the motor temperature is higher than a predetermined temperature, and limits a torque to cause the torque to change more slowly in a case where a time rate of change of the motor temperature is greater than a predetermined value, compared to a case where the time rate of change of the motor temperature is equal to or less than the predetermined value.

Description

Technical FieldThe present invention relates to a control device.Background ArtConventionally, in an electric vehicle such as an electric car or a hybrid vehicle, when an overload state of an engine continues due to high-speed running for a long time, climbing a mountain road, or the like, the temperature of the engine rises and becomes an overheated state, which may cause a failure. Therefore, there is a need for techniques for limiting an output torque according to a state of the temperature of the engine.As a technical background of the present invention, the following patent literature is known. PTL 1 discloses a technique that can more effectively suppress heat generation of a motor during regenerative control by setting a temperature at which motor output is started to be limited lower than a temperature of power operation control in regenerative control. Further, PTL 2 discloses a technique that can achieve temperature protection and power development of an engine simultaneously by changing the temperature limit of the engine according to a predetermined standard of a change rate of an engine temperature.List of ReferencesPatent LiteraturePTL 1: JP 2000-32 602 APTL 2: JP 2003-304 604 APTL 3: DE 11 2018 000 652 T5SUMMARY OF THE INVENTIONTechnical ProblemIn the technique of PTL 1, when an engine temperature at which the torque limitation is started is lowered to suppress a lag due to a deceleration generated in the process of temperature detection, an output of the engine is likely to be limited, so that there is a problem that a high output time at the time of acceleration is shortened. However, PTL 1 lacks at least the characteristic of the present claim, which is as follows: a control device includes a torque limiting unit, the torque limiting unit includes a torque limiting factor calculating unit that calculates a torque limiting factor based on the motor temperature, and a post-limiting torque calculating unit that outputs the post-limiting torque command to the PWM generating unit based on the torque command from the master control unit and the torque limiting factor output from the torque limiting factor calculating unit, wherein the torque limiting factor calculating unit limits an output torque of a motor based on the motor temperature in a case where the motor temperature is higher than a predetermined temperature and limits a torque to be compared with a case where the motor temperature is higher than a predetermined temperature, in which the time change rate of the engine temperature is equal to or less than the predetermined value, in a case where a time change rate of the engine temperature is greater than a predetermined value, the torque is caused to change more slowly.Further, in the technique of PTL 2, a method of changing a rise of the torque limit map according to a temperature change is used, but a balance point between the engine temperature and a limiting torque changes depending on a temperature rise before the start of the torque limit, a torque that can be continuously output decreases, so that there is a problem that it is difficult to sufficiently develop the output of the engine.Further, the PTL 3 shows a control device including a PWM generation unit that outputs a PWM drive signal to an inverter, and a torque limitation unit that outputs a torque command to the PWM generation unit after limitation based on a torque command from a master control unit and a motor temperature. However, at least the characterizing part of the present patent claim is not shown here either.Solution of the ProblemA control device according to the present invention includes: a PWM generation unit that outputs a PWM drive signal to an inverter; and a torque limitation unit that outputs a torque command after limitation to the PWM generation unit based on a torque command from a master control unit and a motor temperature. The torque limiting unit includes a torque limiting factor calculating unit that calculates a torque limiting factor based on the motor temperature, and a post-limiting torque calculating unit that outputs the post-limiting torque command based on the torque command from the master control unit and the torque limiting factor output from the torque limiting factor calculating unit to the PWM generating unit. The torque limiting factor calculation unit limits an output torque of an engine based on the engine temperature in a case where the engine temperature is higher than a predetermined temperature, and limits a torque to make the torque change more moderate as compared to a case where the time change rate of the engine temperature is equal to or less than the predetermined value in a case where a time change rate of the engine temperature is greater than a predetermined value.Advantageous Effects of the InventionAccording to the present invention, the output of the engine decreases no more than necessary.Brief Description of the DrawingsFIG. 1 is a diagram illustrating a configuration of a control device according to a first embodiment of the present invention. FIG. 2 is an example of a flowchart of the control device according to the first embodiment of the present invention. FIG. 3 is a schematic diagram of a torque limiting factor map. FIG. 4 is a schematic view of torque limiting using an engine temperature of a conventional method. FIG. 5 is a schematic view of torque limiting using an engine temperature according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating a configuration of a control device according to a second embodiment of the present invention. FIG. 7 is a graph illustrating a torque limiting factor map of a control device according to a third embodiment of the present invention.DESCRIPTION OF THE EMBODIMENTSHereinafter, embodiments of the present invention will be described with reference to the drawings.(Configuration of Control Device and First Embodiment)A control device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 6. FIG. 1 is a diagram illustrating a configuration of a control device 60 according to the first embodiment of the present invention.In a system method of the control device 60, a voltage of a DC power supply 10 is output to an inverter 40 via a contactor 20 to convert a DC voltage into an AC voltage, the converted AC voltage being supplied to an AC motor 30 (IPMSM, hereinafter, the motor 30) to control the motor 30. In a case where the DC power supply 10 is used for a drive system of a hybrid vehicle or the like, for example, a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery is used. At this time, it is assumed that a voltage is several hundred volts, and it is assumed that an output shaft of the motor 30 is connected to one axis.Further, in the inverter 40, elements that perform switching at a high speed, such as IGBTs, for three phases are arranged on each of a positive electrode side and a negative electrode side of the DC power supply 10. A pulse width modulation method or the like is adopted in which a pulse width of a voltage generated by the inverter 40 is changed by switching the total of six switching elements 41 to apply a predetermined voltage to the motor 30.The control device 60 includes a torque limiting unit and a PWM generating unit 63. the torque limiting unit includes a torque limiting factor calculating unit 61 and a torque after limiting calculating unit 62.The torque limiting factor calculation unit 61 calculates a torque limiting factor Lmt in the post-limiting torque calculation unit 62 based on a motor temperature value Tm detected by a motor temperature sensor 50 (hereinafter, the sensor 50) that detects a temperature (motor temperature) of the motor 30.A specific calculation method of the torque limiting factor Lmt will be described later with reference to FIG. 2.The post-limiting torque calculation unit 62 multiplies a torque command Trq from a higher-order controller (a higher-order control unit) by the torque limiting factor Lmt acquired by the torque limiting factor calculation unit 61, and outputs a post-limiting torque command Trq* to the PWM generation unit 63.The PWM generation unit 63 generates a PWM drive signal based on the post-limiting torque command Trq* detected by the post-limiting torque calculation unit 62 so that a torque close to an actual value is output. The generated PWM drive signal is output to the inverter 40.FIG. 2 is an example of a flowchart of the control device 60 according to the first embodiment of the present invention. It is noted that Figs. 3 to 5 are used in a detailed description of each step.In step S 10, at the start of the torque limiting processing, the torque limiting factor calculation unit 61 acquires the motor temperature value Tm from the sensor 50 that detects the motor temperature.In step S 20, it is determined whether the engine temperature value Tm acquired by step S 10 exceeds 0° C. The processing proceeds to step S 40 when the engine temperature value Tm exceeds 0° C., and proceeds to step S 30 when the engine temperature value Tm is equal to or less than 0° C.In step S 30, it is determined that the torque limitation is unnecessary, the torque limitation factor is calculated as 100%, and the processing proceeds to step S 90.In step S 40, an engine temperature change rate ΔTm is calculated from a deviation between a previous engine temperature value Tmz and the engine temperature value Tm.In step S 50, it is determined whether the engine temperature change rate ΔTm calculated in step S 40 exceeds a predetermined value. The processing proceeds to step S 70 when the engine temperature change rate ΔTm exceeds the predetermined value, while proceeds to step S 60 when the engine temperature change rate ΔTm is equal to or less than the predetermined value.In step S 60, the torque limiting factor Lmt is calculated from a torque command factor map of an initial value, and the processing proceeds to step S 90.In step S 70, an increase in the torque limiting factor map from the engine temperature change rate ΔTm is newly generated.Fig. 3 will be described according to step S70. FIG. 3 is the torque limiting factor map. It is noted that FIG. 3(a) is a conventional torque limiting factor map, while FIG. 3(b) is the torque limiting factor map of the present invention.In step S 50, when the engine temperature change rate ΔTm exceeds the predetermined value, the increase of the torque limiting factor map in a portion between the engine temperatures T 1 and T 2 that are certain constant values is changed based on the engine temperature change rate ΔTm, as illustrated in FIG. 3( b). Specifically, the torque limiting factor map is inclined with a torque limiting factor at T 3, which is an intermediate temperature between the engine temperatures T 1 and T 2, as a fulcrum in the horizontal direction, so that the torque limiting values at T 1 and T 2 come close to each other as ΔTm increases.In step S80, the torque limiting factor Lmt corresponding to the engine temperature value Tm is calculated from the torque limiting factor map after the increase change calculated in step S70.In step S 90, the post-limiting torque command Trq* is calculated by multiplying the torque limiting factor Lmt calculated in step S 30, step S 60, or step S 80 by the torque command Trq acquired from the master controller, and this flowchart is ended.As in the above flowchart, when the engine temperature value Tm is higher than a predetermined temperature, the torque limiting unit calculates a torque command limited based on the engine temperature and limits an output torque of the engine.Next, FIGS. 4 and 5 related to step S 90 will be described. FIG. 4 is a view illustrating the content of torque limitation at the time of engine warming in a conventional method, and FIG. 5 is a view illustrating the transition of the increase of the torque limitation factor map according to the present invention.First, the conventional method in FIG. 4 will be described. When a torque command corresponding to Trq*1 is output from the master controller, the motor temperature Tm gradually increases. A torque limiting factor in FIG. 4 starts from a state of 100%, and the torque limiting is started at the time of reaching the engine temperature T 1 in FIG. 4.Although the torque limitation from the first limitation temperature T 1 (the time point t 1 on the horizontal axis) is applied in FIG. 4, a response of the controller 60 with respect to the motor temperature value Tm is delayed due to a delay in conversion from a current to heat generation or a delay in detection of the motor temperature value Tm. Consequently, at time t 2, a phenomenon in which torque temporarily decreases to Trq*2 after the limitation occurs as illustrated in FIG. 4. Thereafter, at a time point t 3 in FIG. 4, during the coasting, a point (continuous rated value) is generated at which a limiting torque and the motor temperature value Tm are equalized at a predetermined torque value after the limiting, so that a graph converges. The continuous rated value changes depending on an operating condition such as an engine speed, an ambient temperature, a state of a cooling device, and the like.Next, a function of the control device 60 of the present invention will be described with reference to FIG. 5. An upper graph in FIG. 5 is a graph of the engine temperature value Tm similar to FIG. 4. The lower graphs in FIG. 5 are a graph representing a time rate of change (hereinafter, a temperature rate of change ΔTCm) of the engine temperature and a graph representing the increase of the torque limiting factor map with time t on the horizontal axis, respectively.A variable portion of the increase of the torque limiting factor map according to the embodiment of the present invention is determined based on the engine temperature change rate ΔTCm. Here, a first temperature change rate is defined as ΔTCm1.Normally, the temperature change rate ΔTCm at the time t 1 at which the torque limitation is started is in a high state when a torque command of a certain level or more is continuously applied, as illustrated in the middle graph in FIG. 5. At this time, the temperature change rate ΔTCm is significantly larger than the first temperature change rate ΔTCm 1, and thus the increase of the torque limiting factor map (in the horizontal direction) is decreased. This corresponds to a change in the increase of the torque limiting factor map in FIG. 3 in the horizontal direction.As illustrated in the lower graph in FIG. 5, the increase of the torque limiting factor map may be changed within a range from a first increase S 1 to a second increase S 2 to limit a variable angle. As a result, the increase of the torque limiting factor map is variable within a variable range R of FIG. 3(b).At time t 1, the increase of the torque limiting factor map is a lower limit S 1 because the temperature change rate ΔTCm is large. After the start time t1 of the limit, the torque limit is started, and the increase in the engine temperature becomes moderate, so that the temperature change rate ΔTCm decreases.At time t 2, the temperature change rate ΔTCm becomes zero when the engine temperature value Tm reaches the highest point. Thereafter, the motor temperature value Tm turns to fall, and thus the temperature change rate ΔTCm increases again and the operation is executed again in a direction of decreasing the increase of the torque limiting factor map when the temperature change rate ΔTCm exceeds the first temperature change rate ΔTCm 1.Thereafter, each time the temperature change rate ΔTCm exceeds or falls below the first temperature change rate ΔTCm1, the increase of the torque limiting factor map is increased or decreased, the motor temperature value Tm and a torque limiting value are equalized at the time t3, and the limiting torque is saturated. In this process, when the temperature change rate ΔTCm converges within ΔTCm 1, the increase of the torque limiting factor map is set to S 2, that is, it becomes a limiting increase of the torque limiting factor map in the initial state.It is stated that the increase of the torque limiting factor map in FIG. 5 is obtained by multiplying a deviation between the first temperature change rate ΔTCm 1 and the motor temperature value Tm by a predetermined gain and adding a temporary delay filter to suppress an excessive change of the increase.Consequently, in the case where the change rate of the engine temperature is greater than the predetermined value as described in FIG. 3, the torque limiting unit limits the torque so that the torque more moderately changes as compared to a case where the change rate of the engine temperature with time is equal to or less than the predetermined value. Further, the torque limiting amount is made variable by changing the increase of the torque limiting factor map, which is a relational expression between the engine temperature and a torque limiting rate. Further, when the rate of change of the engine temperature is large, the increase of the relational expression between the engine temperature and the torque limiting rate can be decreased while limiting the current flowing through the engine so that the torque moderately changes with respect to the change of the engine temperature.According to the above-described first embodiment of the present invention, the following operational effects are obtained.(1) In the control device 60, the control device 60 includes: the PWM generation unit 63 that outputs the PWM drive signal to the inverter 40; and the torque limitation unit that outputs the torque command after limitation to the PWM generation unit 63 based on the torque command from the master controller and the motor temperature. The torque limiting unit includes: the torque limiting factor calculating unit 61 that calculates the torque limiting factor based on the motor temperature; and the post-limiting torque calculating unit 62 that outputs the post-limiting torque command based on the torque command from the master control unit and the torque limiting factor output from the torque limiting factor calculating unit 61 to the PWM generating unit 63. The torque limiting factor calculation unit 61 limits the output torque of the engine 30 based on the engine temperature in a case where the engine temperature is higher than a predetermined temperature, and limits a torque to cause the torque to more moderately change as compared to a case where the time change rate of the engine temperature is equal to or less than the predetermined value in a case where a time change rate of the engine temperature is greater than a predetermined value. With this configuration, the output of the motor decreases no more than necessary, and the motor can be protected.(2) The torque limiting factor calculation unit 61 of the control device 60 changes the increase of the relational expression between the motor temperature and the torque limiting rate to make the torque limiting amount variable. Consequently, the hunting according to the rate of change of the engine temperature can be suppressed.(3) The torque limiting factor calculation unit 61 of the control device 60 decreases the increase in the relational expression between the engine temperature and the torque limiting rate as the rate of change in the engine temperature increases. With this configuration, the follow-up can be rapidly increased even in a transient state in which the engine temperature starts to increase without excessive torque limitation being suppressed.(4) The torque limiting unit of the control device 60 limits the current flowing through the motor 30, so that the torque moderately changes with respect to the change in the motor temperature. In this way, an output of a vehicle does not change, and the performance does not deteriorate.(Second Embodiment)Referring to Fig. 6, a second embodiment of the present invention will be described. FIG. 6 is a diagram illustrating a configuration of a control device 60A according to a second embodiment of the present invention.The control device 60A includes, in addition to the control device 60 described with reference to FIG. 1, an engine temperature correction unit 64. in the first embodiment, the engine temperature value Tm is input by the torque limiting factor calculation unit 61, but an engine temperature estimation value TmA obtained by correcting a detection delay or error of the engine temperature value Tm is generated and input by the engine temperature correction unit 64, as illustrated in FIG. 6.In a case where torque limitation is performed using the torque limitation factor map illustrated in FIG. 4 described in the first embodiment, a considerable delay component is included even when an engine temperature correction value is input, so that torque hunting is likely to occur. Therefore, the torque lag can be further reduced by applying a configuration in which the motor temperature correction is performed on the temperature detected by the sensor 50 to approach an actual motor temperature in a stage before the torque limiting factor calculation unit 61 as illustrated in FIG. 6.According to the second embodiment of the present invention described above, the following operational effects are achieved.(5) The engine temperature detected by the controller 60 is a temperature obtained by correcting the temperature detected by the sensor 50 to approach the actual engine temperature. With this configuration, the follow-up at the time of torque limitation can be further reduced.(Third Embodiment)Referring to Fig. 7, a third embodiment of the present invention will be described. FIG. 7 is a torque limiting factor map of a control device 60B illustrating a third embodiment of the present invention.In the torque limiting factor map of FIG. 7, an intersection point T 3 between T 1 and T 2 is changed from the torque limiting factor map of FIG. 3, which is the first embodiment, depending on an operation condition, a cooling condition, and the like. That is, a fulcrum for changing an increase of a relational expression between an engine temperature and a torque limiting rate is variable.An example of FIG. 7 will be described. For example, when an ambient temperature of the control device is high, there is a case where a saturation point of a limiting torque is assumed to be a point that is closer to T 2 than to T 3 as illustrated in FIG. 3. In this case, if the increase of the torque limiting factor map is set in the horizontal direction in a state where the engine temperature value Tm is higher than T 3, a torque limiting time increases in a range A of FIG. 7, and thus there is a possibility that a torque larger than expected is temporarily output. Here, the torque lag can be reduced by setting the intersection point T 3 to the point closer to T 2 than to T 1 as in T 3B while suppressing a temperature rise larger than expected.According to the third embodiment of the present invention described above, the following operational effects are achieved.(6) The torque limiting factor calculation unit 61 of the control device 60 varies the fulcrum used at the time of changing the increase of the relational expression between the engine temperature and the torque limiting rate. With this configuration, it is possible to reduce the torque drag while suppressing a temperature rise caused by an environmental condition that is larger than expected.As described above, the present invention has been described with respect to a case where the above-described embodiments are applied to the system in which the three-phase AC motor is mounted as a load, but the present invention is not limited thereto and can also be applied to a system including a rotary machine.Further, in the present invention, a torque limiting function of the motor control device related to the motor temperature has been described, but the present invention is also applicable to output limiting at a temperature for other heat generating sites. For example, in a case where an inverter of a motor drive device includes a temperature detection circuit and the inverter is protected by limiting an output having a detected temperature as an input, a delay occurs in conversion from a current to heat, and thus there is a possibility that torque hunting can be suppressed by applying the configuration of the present invention.The above-described respective embodiments and various modifications are merely examples, and the present invention is not limited to these contents except when the features of the invention are impaired. In addition, the various embodiments and modifications have been described above, but the present invention is not limited to these contents. Other aspects that can be considered to be within the scope of the technical ideas of the present invention are also included in the scope of the present invention.List of Reference Numerals10 DC power supply 20 contactor 30 AC motor 40 inverter 41 switching element 50 motor temperature sensor 60 control device 61 torque limiting factor calculation unit 62 post-limiting torque calculation unit 63 PWM generation unit 64 motor temperature correction unit

Claims

A control device comprising: a PWM generation unit that outputs a PWM drive signal to an inverter; and a torque limitation unit that outputs, based on a torque command from a master control unit and a motor temperature, a torque command after limitation to the PWM generation unit, characterized in that the torque limitation unit includes a torque limitation factor calculation unit that calculates a torque limitation factor based on the motor temperature, and an after-limitation torque calculation unit that outputs the torque command after limitation to the PWM generation unit based on the torque command from the master control unit and the torque limitation factor output from the torque limitation factor calculation unit, wherein the torque limitation factor calculation unit limits an output torque of a motor based on the motor temperature in a case, in which the engine temperature is higher than a predetermined temperature, and limits torque to cause the torque to change more slowly compared to a case where the time change rate of the engine temperature is equal to or less than the predetermined value in a case where a time change rate of the engine temperature is greater than a predetermined value.The control device according to claim 1, wherein the torque limiting factor calculation unit changes an increase of a relational expression between the engine temperature and a torque limiting rate to vary a torque limiting amount of the torque command after the limiting.The control device according to claim 2, wherein the torque limiting factor calculation unit decreases the increase of the relational expression between the engine temperature and the torque limiting rate as a change rate of the engine temperature increases.The control device according to claim 1, wherein the engine temperature is a temperature obtained by correcting a temperature detected by a sensor to approach an actual engine temperature.The control device according to claim 2, wherein the torque limiting factor calculation unit varies a fulcrum for changing the increase of the relational expression between the engine temperature and the torque limiting rate.The control device according to claim 1, wherein the torque limiting unit limits a current flowing through the motor to cause the torque to moderately change with respect to a change in the motor temperature.

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