Controller of hybrid vehicle

Abstract

To provide a controller of a hybrid vehicle which can suppress a relay selectively connecting between a power storage device and a control unit to drive a motor from being solid-phase bonded.SOLUTION: A controller of a hybrid vehicle comprises: a first motor which converts power of an engine into electric power; a second motor which is driven by the electric power generated by the first motor; a step-up converter which boosts output voltage of a battery to be output to respective motors; a relay which is arranged between the battery and the step-up converter; a low voltage capacitor which is arranged close to the battery side relative to the step-up converter; and a high voltage capacitor which is arranged close to respective motor sides relative to the step-up converter. In a case that conductive state of the relay continues for a predetermined time period or more, voltage of the high voltage capacitor is kept being higher than that of the low voltage capacitor (step S3) and then the relay is switched to a cut-off state (step S6).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle equipped with an engine and a motor as driving power sources. [Background technology]

[0002] Patent Document 1 describes a control device for an electric vehicle that includes a motor as a driving force source, a battery for supplying power to the motor, a boost converter for boosting the battery's output voltage, and an inverter for generating AC voltages to be applied to each phase of the motor based on the output voltage of the boost converter. This control device is configured to stop the boost converter when a fault occurs in the boost converter and supply the battery's voltage to the inverter to drive the motor. The control device then determines whether a temperature sensor that detects the temperature of the boost converter has failed, and if the temperature sensor is not faulty, limits the battery's discharge power upper limit according to the temperature of the boost converter. If the temperature sensor is faulty, the control device sets the temperature of the boost converter as a normal operating temperature, thereby not limiting the discharge power upper limit and thereby suppressing a decrease in motor torque. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-182919 Summary of the Invention [Problem to be solved by the invention]

[0004] A hybrid vehicle configured as described in Patent Document 1 is usually provided with a relay that electrically connects a battery to a control unit such as a boost converter when the vehicle is powered on. Such a relay conducts electricity by bringing metal contacts into contact with each other, so if the relay is left connected for a long period of time, the contacts of the relay may partially solid-state weld, which may cause inconvenience such as the relay being unable to be quickly switched off when the vehicle is powered off.

[0005] The present invention has been made in light of the above-mentioned technical problems, and aims to provide a control device for a hybrid vehicle that can prevent solid-state welding of a relay that selectively connects an electricity storage device and a control unit for driving a motor. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a control device for a hybrid vehicle comprising an engine, a first motor having a function of converting at least a portion of the engine's power into electric power, a second motor that can be driven by at least a portion of the electric power generated by the first motor, a battery, a boost converter that boosts the output voltage of the battery and outputs it to the first motor and the second motor, a relay that can switch between a conductive state in which the battery and the boost converter are connected and a cut-off state in which the battery and the boost converter are cut off, a low-voltage capacitor provided on the battery side of the boost converter, and a high-voltage capacitor provided on the first motor and second motor side of the boost converter, wherein when the conductive state of the relay continues for a predetermined period of time or longer, the control device switches the relay to a cut-off state while maintaining a state in which the voltage of the high-voltage capacitor is higher than the voltage of the low-voltage capacitor. [Effects of the Invention]

[0007] According to the present invention, when the conduction state of the relay connecting the battery and the boost converter continues for a predetermined time, the voltage of the high-voltage capacitor remains higher than the voltage of the low-voltage capacitor, thereby preventing current from flowing from the battery to the first motor or the second motor, and creating a state in which no current flows through the relay. Therefore, when the relay is disconnected, the relay can be disconnected while preventing a decrease in durability of the relay, such as the flow of an overcurrent. As a result, by periodically disconnecting the contacts of the relay, partial solid-state welding of the contacts can be prevented. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a power train of a hybrid vehicle according to an embodiment of the present invention. [Figure 2] FIG. 4 is a collinear diagram illustrating the driving states of the engine, the first motor, and the second motor in an HV mode. [Figure 3] FIG. 2 is an electric circuit diagram for explaining an example of a connection state of a battery, a relay, and a power control unit. [Figure 4] 4 is a flowchart illustrating an example of control executed by a control device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention and are not intended to limit the present invention.

[0010] First, to explain the hybrid vehicle that is the subject of the present invention, Fig. 1 schematically shows an example of a hybrid vehicle 1 that is the subject of the present invention, and the hybrid vehicle 1 shown here is equipped with a so-called two-motor type powertrain 2. A power split mechanism 4 is disposed on the output side of an engine (ENG) 3, which serves as a driving force source, and an output shaft (crankshaft) of the engine 3 is connected to an input member of the power split mechanism 4. The engine 3 is, for example, a conventionally known multi-cylinder engine that uses gasoline as fuel, and is configured to electrically control the amount of fuel supplied (injection amount) and the amount of intake air.

[0011] The power split mechanism 4 is composed of a single-pinion planetary gear mechanism 5 including a sun gear S, a ring gear R, which is an internal gear arranged concentrically with the sun gear S, a plurality of pinion gears P, which are arranged between the sun gear S and the ring gear R and mesh with each other and rotate and revolve, and a carrier C that holds the pinion gears P. The engine 3 is connected to the carrier C, which serves as an input element. A first motor (MG1) 6, which has a power generating function, is connected to the sun gear S, and the sun gear S serves as a reaction element. The ring gear R is connected to an output member 7, which serves as an output element. A second motor (MG2) 8, which also has a power generating function, is connected to the output member 7 or the ring gear R. Drive torque is transmitted from the output member 7 to left and right drive wheels 10 via a differential gear 9, which serves as a final reduction gear, to run the hybrid vehicle 1.

[0012] The first motor 6 and the second motor 8 are, for example, permanent magnet synchronous motors, and are connected to a battery (BAT) 12 via a power control unit (PCU) 11 (described later). That is, the first motor 6 and the second motor 8 are supplied with power from the battery 12 to generate driving force, are forcibly rotated to generate power and charge the battery 12, and further, the power generated by one of the motors 6(8) is supplied to the other motor 8(6) to drive the other motor 8(6).

[0013] Various driving modes can be adopted by utilizing the differential action of the planetary gear mechanism 5 that constitutes the power split mechanism 4. For example, it is possible to set an HV mode in which the power output by the engine 3 is split between the first motor 6 side and the output member 7 side, and the rotation speed of the engine 3 is controlled by the first motor 6, an EV mode in which the engine 3 is stopped and the second motor 8 is driven by power from the battery 12, and the vehicle travels using the second motor 8 as a driving power source, and a regeneration mode in which energy is regenerated by the second motor 8 during deceleration.

[0014] 2 is a nomographic diagram of the planetary gear mechanism 5 that constitutes the power split mechanism 4, showing its operating state in HV mode. The nomographic diagram is a diagram in which three lines are drawn parallel to one another: a line indicating the sun gear S, a line indicating the carrier C, and a line indicating the ring gear R. The distance between the line indicating the sun gear S and the line indicating the carrier C is set to "1," and the distance between the line indicating the carrier C and the line indicating the ring gear R is set to the gear ratio of the planetary gear mechanism 5 (the ratio of the number of teeth of the sun gear S to the number of teeth of the ring gear R). The position on these three lines from a base line that intersects these three lines at right angles indicates the rotation speed of each rotating element.

[0015] In Fig. 2, diagonal line L indicates the rotational state and torque acting state of each rotating element when the hybrid vehicle 1 is running in a predetermined state (HV mode) with the engine 3 operating. The torque output by the engine 3 acts on the carrier C in the upward direction in Fig. 2, and the resistance force associated with running the hybrid vehicle 1 acts on the ring gear R in the downward direction in Fig. 2. Therefore, in order to apply the torque of the engine 3 to the ring gear R, the resistance torque from the first motor 6 is applied to the sun gear S in the downward direction in Fig. 2. In this way, a torque greater than the resistance force associated with running acts on the ring gear R in the upward direction in Fig. 2, and the hybrid vehicle 1 is powered to run.

[0016] In the HV mode shown in FIG. 2 , the first motor 6 is operated in a direction that reduces its rotational speed, which is a control state in which the first motor 6 functions as a generator. As a result, the electric power obtained by the first motor 6 is supplied to the battery 12 for charging, or is supplied to the second motor 8, causing the second motor 8 to function as a motor. That is, the power output by the engine 3 is split by the power split mechanism 4 to the output member 7 side and the first motor 6 side. The torque is converted into electric power by the first motor 6 and then converted back into mechanical torque by the second motor 8. This torque is added to the so-called direct torque transmitted from the ring gear R to the output member 7 and transmitted to the drive wheels 10. That is, this hybrid vehicle 1 is a series-parallel type hybrid vehicle 1 in which the power of the engine 3 is converted into electric power by the generator, and the electric power is supplied to the electric motor to output drive torque, and a portion of the power of the engine 3 is transmitted to the drive wheels 10.

[0017] When the first motor 6 is made to function as a generator in this way, the inertial mass of the vehicle body is significantly greater than the inertial mass of the engine 3, and therefore the rotation speed of the engine 3 changes continuously by varying the torque of the first motor 6. In other words, the engine rotation speed is controlled by the first motor 6. In other words, the power split mechanism 4 can function as a continuously variable transmission mechanism.

[0018] Fig. 3 shows an example of an electric circuit that supplies power from battery 12 to first motor 6 and second motor 8. Battery 12 shown in Fig. 3 can be configured similarly to batteries that exchange power with motors mounted on conventional electric vehicles or hybrid vehicles, and is configured by connecting multiple secondary batteries, such as lithium-ion batteries or nickel-metal hydride batteries, in series.

[0019] A PCU 11 is connected to the battery 12. That is, a positive bus 13 connected to the positive electrode of the battery 12 and a negative bus 14 connected to the negative electrode of the battery 12 are connected to the PCU 11.

[0020] The positive busbar 13 is provided with a positive side system main relay (hereinafter referred to as SMRB) 15 that can selectively cut off the connection between the positive electrode of the battery 12 and the PCU 11, and similarly, the negative busbar 14 is provided with a negative side system main relay (hereinafter referred to as SMRG) 16 that can selectively cut off the connection between the negative electrode of the battery 12 and the PCU 11.

[0021] 3, a bypass electric wire 17 is connected to the negative bus bar 14, and is connected to the battery 12 side of the SMRG 16 and the PCU 11. An electric resistance member 18 provided on the PCU 11 side and a pre-charge system main relay (hereinafter referred to as SMRP) 19 that can selectively cut off the bypass electric wire 17 are connected in series to the bypass electric wire 17.

[0022] The SMRB15, SMRG16, and SMRP19 are configured similarly to conventional relays, and are configured so that, for example, when current is applied to a solenoid (not shown), the electromagnetic force causes a movable member made of a magnetic material to move and close (establish a conductive state) a contact made of a metal material. That is, when the SMRB15 and the SMRG16 or SMRP19 are in a conductive state, the battery 12 and the PCU 11 are in a conductive state, and when the SMRB15 and the SMRG16 or SMRP19 are in an open state, the battery 12 and the PCU 11 are in a cut-off state.

[0023] The PCU 11 is composed of a smoothing capacitor 20 for suppressing fluctuations in the voltage input from the battery 12, a boost converter 21 that boosts and outputs the output voltage of the battery 12, a capacitor 22 provided on the output side of the boost converter 21 (between the first motor 6 and the second motor 8), a first inverter 23 that converts the input DC power into AC power and outputs it to the first motor 6, and also converts the AC power generated by the first motor 6 into DC power, and a second inverter 24 that converts the input DC power into AC power and also converts the AC power generated by the second motor 8 into DC power.

[0024] Capacitor 20 corresponds to the "low-voltage capacitor" in the embodiment of the present invention, and is connected to a portion of positive bus 13 between SMRB 15 and boost converter 21, and to a portion of negative bus 14 between SMRG 16 and SMRP 19 and boost converter 21. Capacitor 22 has a larger capacity than capacitor 20, and corresponds to the "high-voltage capacitor" in the embodiment of the present invention.

[0025] The boost converter 21 shown in FIG. 3 is composed of a reactor 25 for suppressing current fluctuations and two switches 26 and 27. One end of the reactor 25 is connected to the positive bus 13. The other end of the reactor 25 is connected to the midpoint of two switches 26 and 27 connected in series. These switches 26 and 27 are composed of insulated gate bipolar transistors (hereinafter referred to as IGBTs) 28 and 29 and diodes 30 and 31 that direct current flow through the IGBTs 28 and 29. The IGBTs 28 and 29 are PWM-controlled, and the voltage on the output side of the converter 21 is reduced by increasing the on-duty of the upper IGBT 28 in FIG. 3, and the voltage on the output side of the converter 21 is increased by increasing the on-duty of the lower IGBT 29 in FIG. 3. In addition, an actuator such as a DC-DC converter that changes the voltage to charge an air conditioner compressor or an auxiliary battery (not shown) is connected between the boost converter 21 and the battery 12, more specifically, between the boost converter 21 and the SMRB15, SMRG16, or SMRP19.

[0026] The first inverter 23 shown in Fig. 3 is composed of an upper arm switch 32a and a lower arm switch 33a provided between the positive electrode bus 13 and the negative electrode bus 14. The upper arm switch 32a has a collector, which is a high potential terminal, connected to the positive electrode bus 13, and an emitter, which is a low potential terminal, connected to the collector, which is a high potential terminal, of the lower arm switch 33a. The emitter, which is a low potential terminal of the lower arm switch 33a, is connected to the negative electrode bus 14. In other words, the upper arm switch 32a and the lower arm switch 33a are connected in series.

[0027] 3, the first motor 6 is a three-phase AC motor, and the upper arm switch 32a and the lower arm switch 33a each include three switches. Specifically, the upper arm switch 32a includes a first switch Q1a connected to the U-phase coil 6u, a third switch Q3a connected to the V-phase coil 6v, and a fifth switch Q5a connected to the W-phase coil 6w. The lower arm switch 33a includes a second switch Q2a connected to the U-phase coil 6u, a fourth switch Q4a connected to the V-phase coil 6v, and a sixth switch Q6a connected to the W-phase coil 6w.

[0028] These switches Q1a to Q6a are each configured by a conventionally known insulated gate bipolar transistor (IGBT), and flywheel diodes D1a to D6a are connected in antiparallel to the IGBT, respectively.

[0029] In addition, the positive bus bar 13 and the negative bus bar 14 are branched between the capacitor 22 and the first inverter 23, and the second motor 8 is connected to the branched positive bus bar 13 and the negative bus bar 14 via the second inverter 24.

[0030] Since the second inverter 24 can be configured in the same manner as the first inverter 23, the "a" in the reference characters of the members that configure the first inverter 23 will be replaced with "b" and the description thereof will be omitted.

[0031] In addition, various sensors are provided, such as a voltage sensor (not shown) that detects the voltage of the battery 12, a low-voltage sensor 34 that detects the voltage VL of the capacitor 20, a high-voltage sensor 35 that detects the voltage VH of the capacitor 22, an ammeter (not shown) that detects the current of each coil, resolvers (not shown) that detect the rotation speed (rotation angle) of the motors 6 and 8, a crank angle sensor that detects the rotation speed (crank angle) of the engine 3, an accelerator opening sensor (not shown) that detects the amount of operation of the accelerator pedal, and a vehicle speed sensor (not shown) that detects the vehicle speed. A controller 36 is provided that controls the engine 3, the inverters 23 and 24, the boost converter 21, the SMRB 15, the SMRG 16, and the SMRP 19 based on detection signals from these sensors.

[0032] This controller 36, like controllers installed in conventional vehicles, is mainly composed of a microcomputer, and is configured to determine the operating state of the hybrid vehicle 1 based on signals input from each of the above sensors, and to control the engine 3, each of the inverters 23, 24, the boost converter 21, SMRB15, SMRG16, and SMRP19 according to that operating state.

[0033] FIG. 4 is a flowchart illustrating an example of control executed by the controller 36. In the control example shown in FIG. 4, first, it is determined whether or not to perform processing to prevent solid-state bonding of the SMRB 15, SMRG 16, and SMRP 19 (step S1). Specifically, it is determined whether the SMRB 15 and the SMRG 16 or SMRP 19 have been in a continuous conduction state for a predetermined time or longer to prevent solid-state bonding. Therefore, step S1 can be determined by counting the time elapsed since the SMRB 15 and the SMRG 16 or SMRP 19 became conductive and comparing the counted time with the predetermined time. The predetermined time may be a variable value that varies depending on the current value flowing through the SMRB 15, SMRG 16, and SMRP 19, the ambient temperature, and the like. Note that the SMRB 15, SMRG 16, and SMRP 19 are generally in a conductive state in the ready-to-drive state to input or output power from the battery 12 when the vehicle is ready to drive.

[0034] If a predetermined time has not elapsed since the SMRB 15 and the SMRG 16 or the SMRP 19 became conductive, and therefore there is no need to perform the solid-state bonding prevention process, and if a negative determination is made in step S1, this routine is terminated. Conversely, if a determination is made that the SMRB 15 and the SMRG 16 or the SMRP 19 have been conductive for a predetermined time or more, and therefore it is determined that the solid-state bonding prevention process should be performed, the engine 3 is driven (step S2). This step S2 is a control for using the engine 3 to provide the energy required to drive the hybrid vehicle 1 and to maintain the voltage VH of the capacitor 22, as described below. Therefore, if the EV mode was set when this control example was executed, the engine 3 is started and switched to the HV mode, and if the HV mode was set, the engine 3 is maintained in the driven state.

[0035] Next, power balance control is executed (step S3). This power balance control is a control for stopping charging and discharging from the battery 12. Specifically, first, the voltage VH of the capacitor 22 is set to be higher than the voltage VL of the capacitor 20. Normally, when a predetermined time has elapsed since the hybrid vehicle 1 entered the ready-on state, the capacitor 22 is charged with the voltage boosted by the boost converter 21. Therefore, when step S3 is executed, the voltage VH of the capacitor 22 is higher than the voltage VL of the capacitor 20. However, when power is temporarily consumed, such as during sudden acceleration, the voltage VH of the capacitor 22 may drop. In such a case, the capacitor 22 is charged so that the voltage VH of the capacitor 22 is higher than the voltage VL of the capacitor 20.

[0036] Next, the balance between the power generated by the first motor 6 and the power consumed by the second motor 8 is balanced. Specifically, the engine 3 generates power equivalent to the running power required for the hybrid vehicle 1. In this case, the operating point of the engine 3 may be controlled to an engine speed that provides good fuel economy. Note that the power required of the engine 3 preferably takes into consideration the energy loss when the first motor 6 generates power and the energy loss when the second motor 8 is driven.

[0037] All of the power generated by the first motor 6 is then supplied to the second motor 8. By supplying the power generated by the first motor 6 to the second motor 8 in this manner, power is not exchanged between the first motor 6 or the second motor 8 and the battery 12. Note that in addition to the power generated by the first motor 6, power sufficient to maintain a state in which the voltage VH of capacitor 22 is higher than the voltage VL of capacitor 20 may be supplied from capacitor 22 to the second motor 8, or part of the power generated by the first motor 6 may be charged to capacitor 22 in order to maintain a state in which the voltage VH of capacitor 22 is higher than the voltage VL of capacitor 20.

[0038] Following step S3, the boost converter 21 is shut off, and all actuators connected to the battery 12 side of the boost converter 21 are stopped (step S4). Then, it is determined whether the current value of the battery 12 is approximately zero (step S5). If the current value of the battery 12 is approximately zero and the determination in step S5 is affirmative, the SMRB 15 and the SMRG 16 or the SMRP 19 are shut off (step S6). Conversely, if the current value of the battery 12 is not approximately zero and the determination in step S5 is negative, arc discharge may occur when the SMRB 15 and the SMRG 16 or the SMRP 19 are shut off, and therefore the process returns to step S5. Note that, as described above, since the boost converter 21 is shut off and all actuators connected to the battery 12 side of the boost converter 21 are stopped, the current value of the battery 12 is usually approximately zero, and therefore step S5 may be omitted.

[0039] As described above, after disconnecting the SMRB 15 from the SMRG 16 or SMRP 19, the SMRB 15 and the SMRG 16 or SMRP 19 are returned to a conductive state, as in the normal state. Specifically, it is determined whether the voltage VB of the battery 12 and the voltage VL of the capacitor 20 are substantially the same (step S7). This step S7 is a step for determining whether an overcurrent will flow and an arc discharge will occur when the SMRB 15 and the SMRG 16 are connected.

[0040] Therefore, if the voltage VB of the battery 12 and the voltage VL of the capacitor 20 are substantially the same and therefore the determination in step S7 is affirmative, the SMRB 15 and the SMRG 16 are connected (step S8), and this routine is temporarily terminated. Conversely, if the voltage VB of the battery 12 and the voltage VL of the capacitor 20 are not the same and there is a possibility of arc discharge occurring when the SMRB 15 and the SMRG 16 are connected and therefore the determination in step S7 is negative, the capacitor 20 is precharged (step S8), and the routine returns to step S7. That is, by connecting the SMRB 15 and the SMRP 19, the capacitor 20 is charged while preventing an overcurrent from flowing through the contacts.

[0041] As described above, by controlling the engine 3 and the motors 6 and 8 to balance the power generated by the first motor 6 and the power consumed by the second motor 8, the voltage VH of the capacitor 22 can be maintained at a high voltage. By maintaining the voltage VH of the capacitor 22 higher than that of the capacitor 20, it is possible to prevent current from flowing from the battery 12 to the first inverter 23, the second inverter 24, or the capacitor 20. Furthermore, by shutting off the boost converter 21, it is possible to prevent current from flowing from the first inverter 23, the second inverter 24, or the capacitor 20 to the battery 12. Furthermore, by shutting off all of the actuators connected to the battery 12 side of the boost converter 21, it is possible to prevent current from flowing from the battery 12 to those actuators. In other words, it is possible to prevent current from flowing through circuits on the battery 12 side of the boost converter 21. In other words, it is possible to create a state in which no current flows through the SMRB 15 and the SMRG 16 or the SMRP 19.

[0042] Therefore, when disconnecting the SMRB15 from the SMRG16 or SMRP19 while outputting the required driving force, it is possible to disconnect the SMRB15 from the SMRG16 or SMRP19 while suppressing a decrease in the durability of the SMRB15, SMRG16, and SMRP19, such as the flow of overcurrent. As a result, by periodically disconnecting the contacts of the SMRB15, SMRG16, and SMRP19, it is possible to prevent partial solid-state welding of those contacts.

[0043] The hybrid vehicle in the embodiment of the present invention may be any hybrid vehicle equipped with a generator and an electric motor, and is not limited to the series-parallel type hybrid vehicle 1 described above, but may also be a series type hybrid vehicle in which the engine 3 and the drive wheels 10 are not mechanically connected. [Explanation of symbols]

[0044] 1 Hybrid vehicle 2 Powertrain 3 Engine 6,8 Motor 11 Power Control Unit (PCU) 12 Battery 15 Positive system main relay (SMRB) 16 Negative system main relay (SMRG) 17 Bypass Wire 18 Electrical resistance materials 19 System main relay for precharge (SMRP) 20,22 Capacitor 21 Boost Converter 23,24 Inverter 34 Low pressure sensor 35 High pressure sensor 36 Controller

Claims

[Claim 1] a first motor that converts at least a portion of the power of the engine into electric power; a second motor that can be driven by at least a portion of the electric power generated by the first motor; a battery; a boost converter that boosts the output voltage of the battery and outputs the boosted voltage to the first motor and the second motor; a relay that can switch between a conductive state that connects the battery and the boost converter and a cut-off state that cuts off the battery and the boost converter; a low-voltage capacitor that is provided on the battery side of the boost converter; and a high-voltage capacitor that is provided on the first motor and second motor side of the boost converter, When the conductive state of the relay continues for a predetermined time or longer, the relay is switched to a cut-off state while maintaining a state in which the voltage of the high-voltage capacitor is higher than the voltage of the low-voltage capacitor. A control device for a hybrid vehicle.

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