In-vehicle control device

Abstract

To more stably supply power to a low-voltage system in battery-less control.SOLUTION: An automobile comprises: an engine; an electric motor coupled to a crank shaft of the engine and capable of generating power; a high-voltage battery; a system main relay provided in a high-voltage system power line connecting the high-voltage battery and the electric motor; a low-voltage battery; an accessory supplied with power through a low-voltage system power line connected to the low-voltage battery; and a DC / DC converter connected to the high-voltage system power line and the low-voltage system power line. When performing battery-less control to perform drive control while the system main relay is turned off, an on-vehicle control device controls the DC / DC converter so that a limit current which is an upper limit of an output current of the DC / DC converter is synchronized with a rotational speed of the electric motor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an in-vehicle control device. [Background technology]

[0002] A conventional vehicle control device of this type has been proposed, which is mounted on a hybrid vehicle in which an engine, a first motor, and a second motor are connected to three rotating elements of a planetary gear (see, for example, Patent Document 1). When an abnormality occurs in the high-voltage battery while the vehicle control device is executing a mode in which the high voltage of a high-voltage battery, which is a high-voltage power source, is reduced and supplied to an electric power steering system (EPS), the vehicle control device switches to a mode in which the low voltage of a low-voltage battery is increased and supplied to the EPS, then cuts off the connection between the high-voltage battery and the drive circuit, and then switches to a mode in which a voltage corresponding to power generated by a generator is reduced and supplied to the EPS. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-018183 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned on-board control device, when the high-voltage battery is cut off and the battery is operated in batteryless control, fluctuations in the motor rotation speed can cause the voltage on the low-voltage battery side to become overvoltage or undervoltage, which can result in a failure of the power supply to the low-voltage battery and low-voltage auxiliary equipment.

[0005] The main object of the in-vehicle control device of the present invention is to suppress a voltage drop in a high-voltage power line during batteryless control in which the high-voltage battery is disconnected for operation. [Means for solving the problem]

[0006] The in-vehicle control device of the present invention employs the following means to achieve the above-mentioned main object.

[0007] The in-vehicle control device of the present invention comprises: The engine and an electric motor capable of generating electricity connected to a crankshaft of the engine; A high voltage battery; a system main relay provided in a high-voltage power line connecting the high-voltage battery and the electric motor; A low voltage battery; an auxiliary device that receives power via a low-voltage power line connected to the low-voltage battery; a DC / DC converter connected to the high-voltage power line and the low-voltage power line; An in-vehicle control device mounted on an automobile comprising: When performing batteryless control in which the system main relay is turned off, the DC / DC converter is controlled so that a limited current, which is an upper limit of an output current of the DC / DC converter, is synchronized with the rotation speed of the electric motor. It is characterized by:

[0008] The on-board control device of the present invention is mounted on an automobile including an engine, an electric motor capable of generating electricity connected to the engine crankshaft, a high-voltage battery, a system main relay provided on a high-voltage power line connecting the high-voltage battery and the electric motor, a low-voltage battery, an auxiliary device supplied with power via a low-voltage power line connected to the low-voltage battery, and a DC / DC converter connected to the high-voltage power line and the low-voltage power line. When performing batteryless control in which drive control is performed with the system main relay turned off, the on-board control device of the present invention controls the DC / DC converter so that a limit current, which is an upper limit of the output current of the DC / DC converter, is synchronized with the rotation speed of the electric motor. This allows the output current of the DC / DC converter (output current to the low-voltage system) to be within the limit current range, and suppresses a voltage drop on the high-voltage power line that occurs when the generated power of the motor MG is insufficient compared to the output current of the DC / DC converter during batteryless control.

[0009] In the onboard control device of the present invention, during the batteryless control, when the voltage of the high-voltage power line falls outside a predetermined threshold range with respect to the target voltage, the limit current may be gradually reduced. That is, the output current of the DC / DC converter is gradually limited by gradually reducing the limit current each time the voltage of the high-voltage power line falls outside the predetermined threshold range with respect to the target voltage. This allows the output current of the DC / DC converter to be matched to the power generated by the motor MG, thereby suppressing a decrease in the voltage of the high-voltage power line. In this case, if the voltage of the high-voltage power line falls outside the threshold range with respect to the target voltage after the limit current has been set to a predetermined minimum current, the DC / DC converter may be stopped and the batteryless control may be terminated. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an outline of the configuration of an automobile 20 equipped with an on-board control device according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing the electrical system of an automobile 20 according to an embodiment of the present invention; [Figure 3] 10 is a flowchart showing an example of a limit current setting process executed by an MGECU 74. [Figure 4] 10 is an explanatory diagram showing an example of time-dependent changes in the counter Cfail, the rotation speed Nm of the motor MG, and the limit current Ilim. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described. Fig. 1 is a configuration diagram showing an outline of the configuration of an automobile 20 equipped with an on-board control device according to an embodiment of the present invention. Fig. 2 is a configuration diagram showing a model of the electrical system of the automobile 20 according to the embodiment.

[0012] The automobile 20 of the embodiment comprises an engine 22, an automatic transmission 30, a motor MG, an inverter 36, a high-voltage battery 40, a DC / DC converter 50, a low-voltage battery 60, an engine electronic control unit (hereinafter referred to as the "engine ECU") 70, an automatic transmission electronic control unit (hereinafter referred to as the "transmission ECU") 72, and a motor electronic control unit (hereinafter referred to as the "MGECU") 74.

[0013] The engine 22 is configured as an internal combustion engine that outputs power using gasoline, diesel, or the like as fuel. A crankshaft 23 of the engine 22 is connected to the input shaft of the automatic transmission 30. The engine 22 is drive-controlled by an engine ECU 70. The engine ECU 70 is configured as a microcomputer centered around a CPU (not shown). The engine ECU 70 controls the intake air amount, fuel injection, ignition, and the like of the engine 22 based on the rotation speed Ne from a rotation speed sensor 24 attached to the crankshaft 23 and signals from various sensors (not shown) attached to the engine 22.

[0014] The automatic transmission 30 is configured, for example, with a torque converter configured as a general fluid transmission, and an automatic transmission with, for example, six forward gears and one reverse gear, which is made up of multiple planetary gears and multiple hydraulically driven friction engagement elements (clutches, brakes). The output shaft of the automatic transmission 30 is connected to an axle 33, which is coupled to drive wheels 34a, 34b via a differential gear 32. The automatic transmission 30 is driven and controlled by a transmission ECU 72. The transmission ECU 72 is configured as a microcomputer centered around a CPU (not shown). The transmission ECU 72 applies the vehicle speed V and the torque required by the output shaft T* to a predetermined shift line to set a target gear M*, and controls the engagement and disengagement of multiple clutches and brakes so that the gear M becomes the target gear M*.

[0015] The motor MG is configured as, for example, a synchronous generator motor. The rotor of the motor MG is connected to the crankshaft 23 of the engine by a transmission mechanism 26. The transmission mechanism 26 is configured as, for example, a pulley fixed to the crankshaft 23, a pulley fixed to the rotor of the motor MG, and a belt wound around both pulleys. The inverter 30 is configured as, for example, a well-known inverter circuit having six transistors and six diodes connected in parallel to each transistor in the opposite direction. The motor MG is driven and controlled by the MGECU 74. The MGECU 74 is configured as a microcomputer centered on a CPU (not shown). The MGECU 74 drives and controls the motor MG by controlling the switching of the six transistors of the inverter 30 based on a torque command for the motor MG.

[0016] The high-voltage battery 40 may be, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery having a rated output voltage of 40-50 V. The low-voltage battery 60 may be, for example, a lead-acid battery or other secondary battery having a rated output voltage of 12 V.

[0017] As shown in FIGS. 1 and 2 , one end of the DC / DC converter 50 is connected to a high-voltage power line LH, which is connected to the high-voltage battery 40 via a system main relay 42 and an LC filter 46, and the other end is connected to a low-voltage power line LL, which is connected to a low-voltage battery 60 and auxiliary equipment 62. The DC / DC converter 50 has a first switching element 52 as an upper arm, a second switching element 54 as a lower arm, a coil (reactor) 56, and a control IC (control circuit) 58 that controls the switching of the first switching element 52 and the second switching element 54. The first switching element 52 is composed of a transistor and a diode connected in parallel to the transistor in a reverse direction. The drain of the transistor of the first switching element 52 is connected to the high-voltage power line LH. The second switching element 54 is composed of a transistor and a diode connected in parallel to the transistor in a reverse direction. The drain of the transistor of the second switching element 54 is connected to the source of the transistor of the first switching element 52, and the source of the transistor of the second switching element 54 is grounded. One end of the coil 56 is connected to the source of the transistor of the first switching element 52 and the drain of the transistor of the second switching element 54, and the other end of the coil 56 is connected to the low-voltage power line LL. The DC / DC converter 50 is driven and controlled by an MGECU 74, which controls the switching of the first switching element 52 and the second switching element 54. The MGECU 74 receives inputs such as a high-voltage system voltage VH from a voltage detection circuit 48 attached to the high-voltage system power line LH and a low-voltage system voltage VL from a voltage detection circuit 68 attached to the low-voltage power line LL. Under normal conditions, the MGECU 74 provides a voltage command value to a control IC 58 of the DC / DC converter 50 to adjust the low-voltage system voltage VL detected by the voltage detection circuit 68 to a required value. The control IC 58 then controls the switching of the first switching element 52 and the second switching element 54 based on the voltage command value from the MGECU 74. Note that the reactance 44 in FIG. 2 is a parasitic reactance of the circuit.

[0018] Next, a description will be given of the operation of the automobile 20 of the embodiment, particularly the operation of the DC / DC converter 50 when the system main relay 42 is driven with the system main relay 42 turned off. Fig. 3 is a flowchart showing an example of a limit current setting process executed by the MGECU 74 when the system main relay 42 is driven with the system main relay 42 turned off.

[0019] When the limit current setting process is executed, the MGECU 74 first determines whether the high-voltage battery 40 is in a fault state (step S100). The determination of whether the high-voltage battery 40 is in a fault state can be made by checking the value of a flag that is set based on the degree of deterioration and temperature of the high-voltage battery 40. If it is determined that the high-voltage battery 40 is not in a fault state (is normal), it determines that this process is unnecessary and terminates the process.

[0020] If it is determined in step S100 that the high-voltage battery 40 is failing, batteryless control is executed (step S110). In batteryless control, the system main relay 42 is turned off and the high-voltage battery 40 is disconnected, and the power generated by the motor MG is stepped down by the DC / DC converter 50 and supplied to the low-voltage power line LL within the range of the limited current Ilim. In the above-described normal control of the DC / DC converter 50, power is supplied from the high-voltage battery 40 when the power generated by the motor MG is insufficient. Therefore, the DC / DC converter 50 can be controlled so that the voltage VL of the low-voltage power line LL becomes a required value without considering the power generated by the motor MG. However, in batteryless control, because the high-voltage battery 40 is disconnected, if the DC / DC converter 50 is not controlled taking into consideration the power generated by the motor MG, the voltage VH of the high-voltage power line LH will drop, causing problems in the control of the motor MG. The power generated by motor MG depends on the rotation speed Nm of motor MG. However, because the rotor of motor MG is connected to crankshaft 23 of engine 22 via transmission mechanism 26, rotation speed Nm of motor MG is calculated by multiplying rotation speed Ne of engine 22 by a transmission coefficient. Since rotation speed Ne of engine 22 changes in response to accelerator operation by the driver, rotation speed Nm of motor MG also changes in response to accelerator operation by the driver. For this reason, in the batteryless control of this embodiment, in order to maintain voltage VH of high-voltage power line LH, it is necessary to control output current Iout output from DC / DC converter 50 to low-voltage power line LL in accordance with (in synchronization with) rotation speed Nm of motor MG. Power generation control by motor MG is performed so that voltage VH of high-voltage power line LH reaches a target value, as in normal operation.

[0021] In the batteryless control, the voltage VH of the high-voltage power line LH is maintained by setting the limit current Ilim for the output current Iout of the DC / DC converter 50 through the processing of the following steps S120 to S170. First, it is determined whether the counter Cfail matches the threshold Cend (step S120). The counter Cfail indicates the number of times that the batteryless control has been determined to have failed because the voltage VH of the high-voltage power line LH has deviated from the target value by exceeding the threshold, and is set in steps S160 and S170, which will be described later. The counter Cfail is initially set to 0. The threshold Cend is the final value of the number of times that the batteryless control has been determined to have failed. Considering now the state immediately after the execution of the batteryless control has been started in step S110, the counter Cfail is set to 0, and therefore a negative determination is made in step S120.

[0022] If it is determined in step S120 that the counter Cfail is not equal to the threshold Cend, a value f(Cfail) is set as an argument to the synchronization coefficient Ilimup of the limit current Ilim relative to an increase in the rotation speed Nm of the motor MG (step S130). f(Cfail) is predetermined to have the relationship f(1)>f(2)>...>f(n), and the difference f(t)-f(t+1) may be constant regardless of the variable t, or may gradually decrease as the variable t increases.

[0023] Next, the limit current Ilim that can be output from DC / DC converter 50 to low-voltage power line LL is calculated and set using the following equation (1) (step S140). That is, the limit current Ilim is calculated by multiplying the synchronization coefficient Ilimup by the increase in rotation speed ΔNm of motor MG and adding this to the minimum value Ilim0. Here, the minimum value Ilom0 is the minimum current (minimum value of vehicle load current) that can be output to low-voltage power line LL.

[0024] Ilim=Ilim0+Ilimup·ΔNm (1)

[0025] Next, it is determined whether the ignition switch has been turned off (step S150), and if it is determined that the ignition switch has not been turned off, it is determined whether the batteryless control has failed (step S160). As described above, failure of the batteryless control can be determined based on whether the voltage VH of the high-voltage power line LH has exceeded a threshold value and deviated from a target value. If it is determined that the batteryless control has not failed, the process returns to setting the limit current Ilim in step S140. Therefore, as long as the batteryless control has not failed, the processes of steps S140 to S160 are repeated until the ignition switch is turned off, the limit current Ilim is set in synchronization with the rotation speed Nm of the motor MG, and the output current Iout from the DC / DC converter 50 to the low-voltage power line LL is controlled to be within the range of the limit current Ilim.

[0026] If it is determined in step S160 that the batteryless control has failed, the counter Cfail is incremented by a value of 1 (step S170), and the process returns to step S120, where it is determined whether the counter Cfail matches the threshold Cend. When the counter Cfail is incremented by a value of 1, the synchronization coefficient Ilimup is set based on the incremented counter Cfail in step S130, and the limit current Ilim is set using the newly set synchronization coefficient Ilimup in step S140. As described above, since there is the relationship f(1)>f(2)>···>f(n), the newly set synchronization coefficient Ilimup is smaller than the previous synchronization coefficient Ilimup. Therefore, the limit current Ilim is also set to be smaller than the previous limit current Ilim. As explained above, the processes in steps S120 to S170 are processes for setting a stepwise smaller limit current Ilim using a synchronization coefficient Ilimup that is gradually reduced each time the batteryless control fails.

[0027] FIG. 4 is an explanatory diagram showing an example of the time variations of the counter Cfail, the motor MG rotation speed Nm, and the limit current Ilim. FIG. 4(a) shows the time variations of the motor MG rotation speed Nm and the limit current Ilim when the counter Cfail is 0. FIG. 4(b) shows the time variations of the motor MG rotation speed Nm and the limit current Ilim when the counter Cfail is 3. FIG. 4(c) shows the time variations of the motor MG rotation speed Nm and the limit current Ilim when the counter Cfail is Cend-1. Note that the synchronization coefficient Ilimup is set to 0 when the counter Cfail is Cend-1. Therefore, the limit current Ilim when the counter Cfail is Cend-1 is set to the minimum value Ilim0. In the diagram, the dashed line indicates the motor MG rotation speed Nm, and the solid line indicates the limit current Ilim. The left axis indicates the motor MG rotation speed [rpm], and the right axis indicates the limit current value [A]. In this embodiment, as shown in the figure, the limit current Ilim of the DC / DC converter 50 is synchronized with the rotation speed Nm of the motor MG, and decreases in stages as the counter Cfail increases.

[0028] If the ignition switch is turned off while the batteryless control is being executed, an affirmative determination is made in step S150, the batteryless control is ended (step S180), and this process is terminated.

[0029] When the batteryless control repeatedly fails and the counter Cfail reaches the threshold Cend, a positive determination is made in step S120, the batteryless control is ended (step S180), and this process is ended.

[0030] In the MGECU 74 mounted on the automobile 20 of the embodiment described above, when batteryless control is performed in which the power generated by the motor MG is stepped down by the DC / DC converter 50 and supplied to the low-voltage power line LL with the system main relay 42 turned off and the high-voltage battery 40 disconnected, the limit current Ilim of the output current Iout output from the DC / DC converter 50 to the low-voltage power line LL is synchronized with the rotation speed Nm of the motor MG. This makes it possible to suppress a drop in the voltage BH of the high-voltage power line LH caused by an excess or deficiency of the power generated by the motor MG relative to the output current Iout of the DC / DC converter 50.

[0031] In the MGECU 74 mounted on the automobile 20 of this embodiment, the limit current Ilim is set to a value that gradually decreases using a synchronization coefficient Ilimup that gradually decreases each time batteryless control fails. This allows the output current Ilim of the DC / DC converter 50 to be set to a value that matches the power generated by the motor MG, thereby suppressing a decrease in the voltage VH of the high-voltage power line LH.

[0032] In the embodiment of the automobile 20, the engine 22 and the motor MG are connected via a transmission mechanism 26 consisting of two pulleys and a belt wound around both pulleys, but they may also be connected via a chain mechanism, a gear mechanism, or a direct connection.

[0033] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problems" section will be described below. In the embodiment, the engine 22 corresponds to the "engine," the motor MG corresponds to the "electric motor," the high-voltage battery 40 corresponds to the "high-voltage battery," the system main relay 42 corresponds to the "system main relay," the low-voltage battery 60 corresponds to the "low-voltage battery," the accessories 62 correspond to the "accessories," the DC / DC converter 50 corresponds to the "DC / DC converter," and the MGECU 74 corresponds to the "on-vehicle control device."

[0034] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0035] The above describes the forms for implementing the present invention, but the present invention is not limited to these embodiments, and it goes without saying that the present invention can be implemented in various forms within the scope that does not deviate from the gist of the present invention. [Industrial Applicability]

[0036] The present invention can be used in the manufacturing industry of in-vehicle control devices, etc. [Explanation of symbols]

[0037] 20 automobile, 22 engine, 23 crankshaft, 24 rotation speed sensor, 26 transmission mechanism, 30 automatic transmission, 32 differential gear, 33 axle, 34a, 34b drive wheels, 36 inverter, 40 high-voltage battery, 42 system main relay, 44 reactor, 46 LC filter, 48 voltage detection circuit, 50 DC / DC converter, 52 first switching element, 54 second switching element, 56 coil, 58 control IC, 60 low-voltage battery, 62 auxiliary equipment, 68 voltage detection circuit, 70 engine electronic control unit (engine ECU), 72 automatic transmission electronic control unit (transmission ECU), 74 motor electronic control unit (motor ECU), LL low-voltage power line, LH high-voltage power line, MG motor.

Claims

1. The engine and an electric motor capable of generating electricity connected to a crankshaft of the engine; A high voltage battery; a system main relay provided in a high-voltage power line connecting the high-voltage battery and the electric motor; A low voltage battery; an auxiliary device that receives power via a low-voltage power line connected to the low-voltage battery; a DC / DC converter connected to the high-voltage power line and the low-voltage power line; An in-vehicle control device mounted on an automobile comprising: When performing batteryless control in which the system main relay is turned off, the DC / DC converter is controlled so that a limit current, which is an upper limit of an output current of the DC / DC converter, is synchronized with the rotation speed of the electric motor.

1. An in-vehicle control device comprising:

2. 2. The vehicle-mounted control device according to claim 1, When the voltage of the high-voltage power line falls outside a range of a predetermined threshold value with respect to a target voltage during the batteryless control, the limited current is gradually reduced. In-vehicle control device.

3. 3. The vehicle-mounted control device according to claim 2, When the voltage of the high-voltage power line falls outside the range of the threshold value with respect to the target voltage after the limit current is set to a predetermined minimum current, the DC / DC converter is stopped and the batteryless control is terminated. In-vehicle control device.

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