JP7732226B2 - Relay welding detection device - Google Patents

Description

The present invention relates to a relay welding determination device.

Patent Document 1 discloses a hybrid vehicle that does not have a boost converter.

JP 2016-163529 A

In vehicles that do not have a boost converter like the one disclosed in Patent Document 1, for example, it is not possible to use a boost converter to boost and fluctuate the voltage from the battery to charge a capacitor, and then use the potential difference between the capacitor voltage and the battery voltage to determine whether a relay connected to the battery has welded.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a relay welding determination device that can determine whether a relay is welded without using a boost converter.

In order to solve the above-mentioned problems and achieve the objectives, the relay welding determination device of the present invention is mounted on a vehicle equipped with an internal combustion engine, a rotating electric machine capable of generating electricity using power from the internal combustion engine, an inverter that drives the rotating electric machine, a chargeable and dischargeable power storage device, a relay that can connect and disconnect the inverter and the power storage device, a capacitor connected in parallel between the inverter and the relay, and voltage detection means that detects the voltage of the capacitor. The device generates electricity using power from the internal combustion engine at the rotating electric machine, performs power control to fluctuate the voltage of the capacitor, and determines whether the relay is welded.

This allows the rotating electrical machine to generate power using power from the internal combustion engine without using a boost converter, and the capacitor voltage can be varied to determine whether the relay is welded.

Furthermore, in the above, after the connection is released by the relay, power from the internal combustion engine is used to generate electricity at the rotating electric machine, and power control is performed to vary the capacitor voltage in two stages. If the absolute value of the difference between the capacitor voltage in the first stage of variation and the capacitor voltage in the second stage of variation is larger than a preset threshold, it is determined that the relay is not welded, and if it is smaller than the threshold, it is determined that the relay is welded.

This means that even if the final value of the varied capacitor voltage is the same potential as the voltage of the power storage device, the capacitor voltage can be varied to determine whether the relay is welded.

The relay welding determination device according to the present invention has the advantage of being able to determine whether a relay is welded by using power from an internal combustion engine to generate electricity using a rotating electric machine and fluctuating the capacitor voltage, without using a boost converter.

FIG. 1 is a block diagram showing a schematic overall configuration of a hybrid vehicle equipped with a relay welding determination device according to an embodiment. FIG. 2 is a circuit block diagram for explaining the configuration of the vehicle's electrical system. FIG. 3 is a diagram showing an example of how to vary system voltage VH in determining whether a relay is welded. FIG. 4 is a flowchart showing an example of control of relay welding determination performed by the ECU in this embodiment.

The following describes an embodiment of a relay welding determination device according to the present invention. However, the present invention is not limited to this embodiment. The relay welding determination device according to the present invention is mounted, for example, on a hybrid vehicle in which a rotating electric machine generates electricity using driving force from an internal combustion engine.

1 is a block diagram showing the overall configuration of a hybrid vehicle 1 equipped with a relay welding determination device according to an embodiment. The hybrid vehicle 1 includes an engine 100, a first motor-generator 10 (hereinafter sometimes referred to as MG1) which is a first rotating electric machine, a second motor-generator 20 (hereinafter sometimes referred to as MG2) which is a second rotating electric machine, a planetary gear mechanism 30, drive wheels 50, an output shaft 60 connected to the drive wheels 50, a wheel speed sensor 73, a battery 150, an SMR (System Main Relay) 160, a charging relay 170, a charging device 172, an inlet 174, a PCU (Power Control Unit) 200, and an ECU (Electronic Control Unit) 300. In this embodiment, the ECU 300 functions as a relay welding determination device mounted on the hybrid vehicle 1 to determine whether the SMR 160 is welded.

The hybrid vehicle 1 runs using the power of at least one of the engine 100 and the second motor generator 20. During normal running, the hybrid vehicle 1 can switch between electric vehicle running (hereinafter referred to as "EV running"), in which the hybrid vehicle 1 runs (electrically runs) using the power of the second motor generator 20 without using the power of the engine 100 (i.e., with the engine 100 stopped), and hybrid vehicle running (hereinafter referred to as "VH running"), in which the hybrid vehicle runs using the power of both the engine 100 and the second motor generator 20.

Engine 100 is an internal combustion engine such as a gasoline engine or a diesel engine. Engine 100 generates power for driving hybrid vehicle 1 in response to control signals from ECU 300. The power generated by engine 100 is output to planetary gear mechanism 30.

Engine 100 is provided with an engine rotation speed sensor 410. Engine rotation speed sensor 410 detects the rotation speed (engine rotation speed) Ne of engine 100's crankshaft 110 and outputs a signal indicating the detection result to ECU 300.

The first motor generator 10 and the second motor generator 20 are each a three-phase AC permanent magnet synchronous motor. When starting the engine 100, the first motor generator 10 uses power from the battery 150 to rotate the crankshaft 110 of the engine 100. The first motor generator 10 can also generate electricity using power from the engine 100. The AC power generated by the first motor generator 10 is converted to DC power by the PCU 200 and charged into the battery 150. The AC power generated by the first motor generator 10 may also be supplied to the second motor generator 20.

The rotor of the second motor generator 20 is connected to the output shaft 60. The second motor generator 20 rotates the output shaft 60 using power supplied from at least one of the battery 150 and the first motor generator 10. The second motor generator 20 is also capable of generating power through regenerative braking. The AC power generated by the second motor generator 20 is converted to DC power by the PCU 200 and charged into the battery 150.

The output shaft 60 is connected to the left and right drive wheels 50 via a differential gear. The drive wheels 50 are provided with wheel speed sensors 73. The wheel speed sensors 73 detect the rotational speed of the drive wheels 50 as wheel speed VS and output a signal indicating the detection result to the ECU 300. The wheel speed sensors 73 can detect the magnitude (absolute value) of the rotational speed of the drive wheels 50, but cannot detect the rotational direction of the drive wheels 50. In other words, the ECU 300 can determine the magnitude (absolute value) of the rotational speed of the drive wheels 50 from the output value of the wheel speed sensor 73, but cannot determine the rotational direction of the drive wheels 50. Note that while one wheel speed sensor 73 is shown in FIG. 1, the number of wheel speed sensors 73 is not limited to one. For example, a wheel speed sensor 73 may be provided for each of the four wheels of the hybrid vehicle 1 (the left and right drive wheels 50 and the left and right driven wheels (not shown)).

The planetary gear mechanism 30 mechanically connects the engine 100, the first motor generator 10, and the output shaft 60, and is configured to transmit torque between the engine 100, the first motor generator 10, and the output shaft 60. Specifically, the planetary gear mechanism 30 includes, as rotating elements, a sun gear S connected to the rotor of the first motor generator 10, a ring gear R connected to the output shaft 60, a carrier CA connected to the crankshaft 110 of the engine 100, and a pinion gear P meshing with the sun gear S and the ring gear R. The carrier CA holds the pinion gear P so that the pinion gear P can rotate and revolve around its axis.

By configuring the planetary gear mechanism 30 as described above, the rotational speed of the sun gear S (= MG1 rotational speed Nm1), the rotational speed of the carrier CA (= engine rotational speed Ne), and the rotational speed of the ring gear R (= MG2 rotational speed Nm2) are connected by a straight line on a nomographic diagram (a relationship in which the rotational speed of the remaining one is determined once any two of the rotational speeds are determined; hereinafter also referred to as the "nomographic diagram relationship"). Furthermore, because the ring gear R is connected to the drive wheels 50 via the output shaft 60, the magnitude (absolute value) of the rotational speed of the ring gear R (= MG2 rotational speed Nm2) is proportional to the magnitude (absolute value) of the wheel speed VS.

Battery 150 is a rechargeable lithium-ion secondary battery. However, battery 150 may also be another secondary battery, such as a nickel-metal hydride secondary battery.

The SMR 160 is connected in series to the power line between the battery 150 and the PCU 200. The SMR 160 switches between a conductive state and a cut-off state between the battery 150 and the PCU 200 in response to a control signal from the ECU 300.

The PCU 200 converts the DC power stored in the battery 150 into AC voltage and supplies it to the first motor generator 10 and the second motor generator 20. The PCU 200 also converts the AC power generated by the first motor generator 10 and the second motor generator 20 into DC power and supplies it to the battery 150.

The ECU 300 includes a CPU (Central Processing Unit), memory, input/output buffers, and other components, none of which are shown. Based on signals from various sensors and devices, as well as maps and programs stored in memory, the ECU 300 controls the output (fuel injection, ignition timing, valve timing, etc.) of the engine 100 and the output (amount of current) of the first motor-generator 10 and the second motor-generator 20 so that the hybrid vehicle 1 operates in the desired driving state. Note that the various controls are not limited to software processing, and can also be performed using dedicated hardware (electronic circuits).

Figure 2 is a circuit block diagram illustrating the configuration of the electrical system of the hybrid vehicle 1. The electrical system of the hybrid vehicle 1 includes a battery 150, an SMR 160, a PCU 200, a first motor generator 10, a second motor generator 20, and an ECU 300. The PCU 200 includes a capacitor C1, a first inverter 221, a second inverter 222, and a voltage sensor 230.

The battery 150 is provided with a monitoring unit 440. The monitoring unit 440 detects the voltage (battery voltage) VB of the battery 150, the current (battery current) IB supplied to the battery 150, and the temperature (battery temperature) TB of the battery 150, and outputs signals indicating these detection results to the ECU 300.

Capacitor C1 is connected in parallel between the first inverter 211 and the second inverter 222 and the SMR 160, and smooths the battery voltage VB before supplying it to the first inverter 211 and the second inverter 222.

The voltage sensor 230 detects the system voltage VH, which is the voltage across the capacitor C1, and outputs a signal indicating the detection result to the ECU 300.

When the first inverter 221 receives the system voltage VH, it converts the DC voltage to AC voltage in response to a control signal from the ECU 300 to drive the first motor generator 10. The first inverter 221 includes a U-phase arm 1U, a V-phase arm 1V, and a W-phase arm 1W. The phase arms are connected in parallel between the power lines PL and NL. The U-phase arm 1U has switching elements Q3 and Q4 connected in series. The V-phase arm 1V has switching elements Q5 and Q6 connected in series. The W-phase arm 1W has switching elements Q7 and Q8 connected in series. Diodes D3 to D8 are connected in anti-parallel between the collector and emitter of each of the switching elements Q3 to Q8.

When the second inverter 222 receives the system voltage VH, it converts the DC voltage into AC voltage in response to a control signal from the ECU 300 to drive the second motor generator 20. The second inverter 222 includes phase arms 2U-2W, switching elements Q9-Q14, and diodes D9-D14. The configuration of the second inverter 222 is basically the same as that of the first inverter 221, so a detailed description thereof will be omitted.

The first motor generator 10 is provided with a resolver 421. The resolver 421 detects the rotational speed of the first motor generator 10 (MG1 rotational speed Nm1) and outputs a signal indicating the detection result to the ECU 300. The resolver 421 is capable of detecting the magnitude (absolute value) and direction of rotation of the rotational speed. In other words, the ECU 300 can determine not only the magnitude (absolute value) of the rotational speed of the first motor generator 10 but also the direction of rotation from the output value of the resolver 421.

The second motor generator 20 is provided with a resolver 422. The resolver 422 detects the rotational speed of the second motor generator 20 (MG2 rotational speed Nm2) and outputs a signal indicating the detection result to the ECU 300. Like the resolver 421, the resolver 422 is capable of detecting the magnitude (absolute value) and direction of rotation of the rotational speed. In other words, the ECU 300 can determine not only the magnitude (absolute value) of the rotational speed of the second motor generator 20 but also the direction of rotation from the output value of the resolver 422.

Furthermore, the first motor generator 10 and the second motor generator 20 are provided with current sensors 241, 242, respectively. Current sensor 241 detects motor current IM1, which is the current flowing through the first motor generator 10. Current sensor 242 detects motor current IM2, which is the current flowing through the second motor generator 20. These sensors each output signals indicating their detection results to ECU 300.

The ECU 300 controls the PCU 200 (first inverter 221 and second inverter 222) based on information from each sensor, etc., so that the outputs of the first motor generator 10 and the second motor generator 20 become the desired outputs. Note that in the example shown in Figure 2, the ECU 300 is configured as a single unit, but the ECU 300 may also be divided into multiple units.

Next, an example of relay welding determination performed in the hybrid vehicle 1 according to the embodiment will be described. In this embodiment, when determining whether the SMR 160 is welded, the first motor-generator 10 is driven to generate electricity using power from the engine 100, and the system voltage VH is varied to determine whether the SMR 160 is welded. For example, when a battery failure requires shutting off the SMR 160, the SMR is checked for shutoff by controlling the power generated by the engine 100 to drive the first motor-generator 10 and generate electricity, thereby varying the system voltage VH (the input voltage of the second inverter 222) and creating a potential difference with the battery voltage VB. During this time, to prevent the second motor-generator 20 from affecting the system voltage VH, the gate of the second inverter 222 is shut off when no back electromotive force (MG2 back electromotive force) is generated in the second motor-generator 20 at low vehicle speeds, thereby reducing power consumption. On the other hand, if counter electromotive force (MG2 counter electromotive voltage) is generated in the second motor generator 20 at high vehicle speeds, a torque of 0 [Nm] is commanded (power is consumed on the d-axis where no torque is generated on the d- and q-axes). In this way, disturbances caused by the second motor generator 20 to the system voltage VH when determining whether the SMR 160 is welded are suppressed.

Figure 3 shows an example of how system voltage VH is varied when determining whether a relay is welded. The initial value VH1 of system voltage VH shown in Figure 3 varies depending on the remaining charge of battery 150 because, when first motor-generator 10 is not generating electricity and SMR 160 is in a conductive state, capacitor C1 is charged with power from battery 150, and battery voltage VB and system voltage VH are at the same potential. Furthermore, by using power from engine 100 to drive first motor-generator 10 to generate electricity, capacitor C1 is also charged with power according to the amount of electricity generated. This makes it possible to vary system voltage VH depending on the power from battery 150 and the power generated by first motor-generator 10.

When varying the system voltage VH, the final value of the varied system voltage VH is set to the median of the inverter operation guaranteed voltage range as the target value V1 to prevent control failure. If the target value V1 and the battery voltage VB were at the same potential, the system voltage VH could not be varied. Therefore, in the relay welding determination performed in this embodiment, the system voltage VH is varied in two stages depending on the elapsed time since the SMR was disconnected, and the target value V1 is set in the second stage of the variation. When varying the system voltage VH in two stages, the target value of the system voltage VH in the first stage is selected as the efficient target value V2 or V3, which does not cause excessive voltage fluctuation, depending on the magnitude relationship between the initial value VH1 of the system voltage VH and the target value V1. In other words, if the initial value VH1 of the system voltage VH is equal to or greater than the target value V1, the target value of the system voltage VH in the first stage is selected as the target value V2, which is higher in potential than the target value V1. On the other hand, if the initial value VH1 of the system voltage VH is less than the target value V1, the target value of the system voltage VH in the first stage is selected to be a target value V3, which is lower in potential than the target value V1.

Then, when the SMR shutoff elapsed time is in the range of 0 to time A, power control is performed by generating power from the first motor generator 10 so that the target system voltage VH* becomes the target value V2 or target value V3 in the first stage of fluctuation, and the actual system voltage VH2 detected by the voltage sensor 230 is latched. After that, when the SMR shutoff elapsed time is in the range of time A to time B, power control is performed by generating power from the first motor generator 10 so that the target system voltage VH* becomes the target value V1 in the second stage of fluctuation, and the actual system voltage VH3 detected by the voltage sensor 230 is latched. Then, when the SMR shutoff elapsed time is equal to or greater than time B, the presence or absence of welding of the SMR 160 is determined from the absolute value of the difference (potential difference) between the actual system voltage VH3 and the actual system voltage VH2.

Specifically, when the initial value VH1 of the system voltage VH is equal to or greater than the target value V1, the difference (potential difference) between the target value V2 and the target value V1 is set as a threshold value VC, and a determination is made as to whether the absolute value of the difference (potential difference) between the actual system voltage VH3 and the actual system voltage VH2 is equal to or greater than the threshold value VC. If it is determined that the absolute value is equal to or greater than the threshold value VC, it is determined that the SMR 160 is not welded. On the other hand, if it is determined that the absolute value is less than the threshold value VC, it is determined that the SMR 160 is welded.

Furthermore, if the initial value VH1 of the system voltage VH is less than the target value V1, the difference (potential difference) between the target value V1 and the target value V3 is set as a threshold value VC, and it is determined whether the absolute value of the difference (potential difference) between the actual system voltage VH3 and the actual system voltage VH2 is equal to or greater than the threshold value VC. If it is determined that the absolute value is equal to or greater than the threshold value VC, it is determined that the SMR 160 is not welded. On the other hand, if it is determined that the absolute value is less than the threshold value VC, it is determined that the SMR 160 is welded.

Figure 4 is a flowchart showing an example of relay welding determination control performed by ECU 300 in this embodiment. First, in step S1, ECU 300 prepares to shut off the SMR. For example, engine 100 is started so that power can be generated by first motor generator 10 at any timing, thereby allowing system voltage VH to fluctuate. Next, in step S2, ECU 300 determines whether the relationship MG2 back EMF ≥ battery voltage VB is satisfied. If ECU 300 determines that the relationship MG2 back EMF ≥ battery voltage VB is satisfied (Yes in step S2), in step S3, ECU 300 enables the gate of second inverter 222, outputs a 0 [Nm] command, and proceeds to step S5. On the other hand, if ECU 300 determines that the relationship MG2 back EMF ≥ battery voltage VB is not satisfied (No in step S2), in step S4, ECU 300 shuts off the gate of second inverter 222 and proceeds to step S5.

Next, in step S5, ECU 300 detects and latches the initial value VH1 of system voltage VH before SMR shutoff using voltage sensor 230. Next, in step S6, ECU 300 performs SMR shutoff processing. Next, in step S7, ECU 300 determines whether the relationship of initial value VH1 of system voltage VH ≧ target value V1 is satisfied. If ECU 300 determines that the relationship of initial value VH1 ≧ target value V1 of system voltage VH is satisfied (Yes in step S7), in step S8, ECU 300 adjusts the amount of power generated by first motor generator 10 to vary system voltage VH so that target system voltage VH* = target value V2, and proceeds to step S10. On the other hand, if the ECU 300 determines that the relationship of initial value VH1 ≧ target value V1 of the system voltage VH is not satisfied (No in step S7), in step S9, the ECU 300 adjusts the amount of power generated by the first motor generator 10 using power from the engine 100 to vary the system voltage VH so that the target system voltage VH* = target value V3, and then proceeds to step S10.

Next, in step S10, ECU 300 detects and latches actual system voltage VH2 when SMR shutdown elapsed time < time A using voltage sensor 230. Next, in step S11, ECU 300 determines whether the relationship time A ≦ SMR shutdown elapsed time < time B is satisfied. If ECU 300 determines that time A ≦ SMR shutdown elapsed time < time B is not satisfied (No in step S11), it repeats the processing of step S11 until the relationship time A ≦ SMR shutdown elapsed time < time B is satisfied. On the other hand, if ECU 300 determines that the relationship time A ≦ SMR shutdown elapsed time < time B is satisfied (Yes in step S11), in step S12, it adjusts the amount of power generated by first motor generator 10 using power from engine 100 to vary system voltage VH so that target system voltage VH* = target value V1. Next, in step S13, ECU 300 detects and latches actual system voltage VH3 at time A≦SMR shutoff elapsed time<time B using voltage sensor 230.

Next, in step S14, ECU 300 determines whether the relationship SMR shutdown elapsed time ≧ time B is satisfied. If ECU 300 determines that the relationship SMR shutdown elapsed time ≧ time B is not satisfied (No in step S14), it repeats the processing of step S14 until the relationship SMR shutdown elapsed time ≧ time B is satisfied. On the other hand, if ECU 300 determines that the relationship SMR shutdown elapsed time ≧ time B is satisfied (Yes in step S14), it determines in step S15 whether the relationship | actual system voltage VH3 - actual system voltage VH2 | ≧ threshold VC is satisfied. If ECU 300 determines that the relationship | actual system voltage VH3 - actual system voltage VH2 | ≧ threshold VC is satisfied (Yes in step S15), it determines in step S16 that SMR 160 is not welded, and ends the series of control operations. On the other hand, if ECU 300 determines that the relationship |actual system voltage VH3 - actual system voltage VH2| ≥ threshold value VC is not satisfied (No in step S15), it determines in step S17 that SMR 160 is welded, and ends the series of control operations.

As described above, the relay welding determination device according to this embodiment does not require a boost converter to boost the battery voltage VB; instead, it uses power from the engine 100 to generate electricity with the first motor generator 10, fluctuating the system voltage VH to determine whether the SMR 160 is welded.

REFERENCE SIGNS LIST 1 Hybrid vehicle 10 First motor generator 20 Second motor generator 30 Planetary gear mechanism 50 Drive wheels 60 Output shaft 73 Wheel speed sensor 100 Engine 110 Crankshaft 150 Battery 160 SMR
200 PCU
221 First inverter 222 Second inverter 230 Voltage sensors 241, 242 Current sensor 300 ECU
410 Engine rotation speed sensor 421, 422 Resolver 440 Monitoring unit

Claims (1)

an internal combustion engine;
a rotating electric machine capable of generating electricity using power from the internal combustion engine;
an inverter that drives the rotating electric machine;
a chargeable and dischargeable electricity storage device;
a relay capable of connecting and disconnecting the inverter and the power storage device;
a capacitor connected in parallel between the inverter and the relay;
a voltage detection means for detecting a system voltage, which is a voltage across the capacitor;
It is installed in a vehicle equipped with
a relay welding determination device that, after the connection is released by the relay, generates power in the rotating electric machine using power from the internal combustion engine , performs power control to vary the system voltage in two stages , and determines that the relay is not welded if an absolute value of a difference between the system voltage in the first stage of variation and the system voltage in the second stage of variation is larger than a preset threshold value, and determines that the relay is welded if the absolute value is smaller than the threshold value,
If the initial value of the system voltage is less than a first target value, a second target value lower in potential than the first target value is set as the target value of the system voltage in the first stage, and the capacitor is charged with power corresponding to the amount of power generated by the rotating electric machine; and the first target value is set as the target value of the system voltage in the second stage, and the capacitor is charged with power corresponding to the amount of power generated by the rotating electric machine.
A relay welding determination device characterized by :