Hybrid vehicle control method and hybrid vehicle control device

Abstract

A vehicle (1) has: an internal combustion engine (10) that can be motored by a drive motor (5); and an electric heating catalyst (23) disposed in an exhaust passage (21). During deceleration while the internal combustion engine (10) is in stoppage, the vehicle (2) calculates a required deceleration force on the basis of a deceleration request, calculates EHC consumable power that can be used to energize the electric heating catalyst (23), and calculates the engine speed of the internal combustion engine (10) in motoring performed to absorb regenerative energy in accordance with the required deceleration force and the EHC consumable power.

Description

Control Method for Hybrid Vehicle and Hybrid Vehicle Control Device

[0001] The present invention relates to a control method for a hybrid vehicle and a hybrid vehicle control device.

[0002] For example, Patent Document 1 discloses a technique for raising the temperature of an exhaust gas purification catalyst by a warming device that uses generated electric power during regenerative braking when, during deceleration, the vehicle is set to a shift range in which a greater deceleration force is generated by regenerative braking from a motor while the internal combustion engine is stopped.

[0003] However, Patent Document 1 only raises the temperature of the catalyst using the generated electric power during deceleration.

[0004] That is, in a hybrid vehicle during deceleration, the engine speed of the internal combustion engine during motoring and the catalyst warm-up using regenerative energy during motoring are not controlled according to the deceleration state, and there is room for further improvement in this regard.

[0005] International Publication No. 2012 / 111103

[0006] The hybrid vehicle of the present invention has an internal combustion engine capable of motoring by an electric motor and an electrically heated catalyst disposed in an exhaust passage. During deceleration when the internal combustion engine is stopped, required deceleration energy is calculated based on a deceleration request, and energizable power that can energize the electrically heated catalyst is calculated. The engine speed of the internal combustion engine in the motoring performed to absorb regenerative energy is calculated according to the required deceleration energy and the energizable power.

[0007] According to the present invention, since the target engine speed of the internal combustion engine during motoring in the hybrid vehicle is calculated according to the required deceleration energy and the energizable power of the electrically heated catalyst, a desired deceleration can be obtained during deceleration even when the battery SOC is high.

[0008] A schematic diagram illustrating the general outline of the drive system of the hybrid vehicle according to the present invention. A schematic diagram illustrating the general outline of the system configuration of the internal combustion engine. A diagram illustrating the correlation between the power consumption of the electric heating catalyst, the engine speed during motoring, and the required deceleration force during vehicle deceleration. A flowchart showing an example of the control flow of the hybrid vehicle according to the present invention. A flowchart showing a subroutine that calculates the engine speed based on the energy consumption target. A flowchart showing a subroutine that calculates the available power for EHC consumption. A flowchart showing a subroutine that calculates the engine speed based on the regeneration request for the exhaust particulate filter.

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a schematic diagram illustrating the drive system of a hybrid vehicle 1 (hereinafter simply referred to as "vehicle") according to the present invention. The vehicle 1 includes a drive unit 3 that drives the drive wheels 2 and a power generation unit 4 that generates electricity to drive the drive wheels 2.

[0010] The drive unit 3 includes a drive motor 5, which acts as an electric motor to rotate the drive wheels 2, and a first gear train 6 and a differential gear 7 that transmit the driving force of the drive motor 5 to the drive wheels 2. Power is supplied to the drive motor 5 from a battery 8 that is charged with electricity generated by the power generation unit 4.

[0011] The power generation unit 4 includes a generator 9 that generates electricity to be supplied to the drive motor 5, an internal combustion engine 10 capable of driving the generator 9, and a second gear train 11 that transmits the rotation of the internal combustion engine 10 to the generator 9.

[0012] Vehicle 1 is a series hybrid vehicle that does not use the internal combustion engine 10 as its primary power source. In other words, the internal combustion engine 10 is mounted on the vehicle for power generation. For example, when the battery level of battery 8 becomes low, vehicle 1 drives the internal combustion engine 10 to charge battery 8 and generate electricity with the generator 9. The control unit 12 also drives the internal combustion engine 10 to start generating electricity with the generator 9 when there is a predetermined power generation request. Various controls for the internal combustion engine 10 are performed by the control unit 12, which acts as the control unit.

[0013] Figure 2 is a schematic diagram illustrating the general system configuration of the internal combustion engine 10.

[0014] The internal combustion engine 10 is, for example, a spark-ignition internal combustion engine that uses gasoline as fuel. In the exhaust passage 21 of the internal combustion engine 10, a three-way catalytic converter 22, an electrically heated catalytic converter (EHC) 23, and an exhaust particulate filter 24 are arranged from the upstream side in the direction of exhaust flow. The three-way catalytic converter 22 and the electrically heated catalytic converter 23 constitute, for example, a manifold catalytic converter installed near the outlet of the exhaust manifold in the exhaust passage 21.

[0015] The three-way catalytic converter 22 can simultaneously purify NOx, HC, and CO in the exhaust gas with maximum conversion efficiency when the air-fuel ratio is within the so-called window centered around the stoichiometric air-fuel ratio.

[0016] The electrically heated catalyst 23 is a catalyst that generates heat when an electric current is passed through it. For example, it has a structure in which a ceramic heating element that generates heat when an electric current is passed through it is used as a catalyst support, and an appropriate catalytic metal that serves as a ternary catalyst or oxidation catalyst is coated onto its surface in a slurry.

[0017] The exhaust particulate filter 24 is a Gasoline Particulate Filter (GPF) that collects exhaust particulate matter (particulate matter) such as soot in the exhaust gas, and can be regenerated by burning off the collected soot under predetermined conditions.

[0018] Here, the energization of the electrically heated catalyst 23 is controlled by the control unit 12, which acts as the control unit. In other words, the catalyst temperature of the electrically heated catalyst 23 can be controlled by the control unit 12.

[0019] The control unit 12 is a well-known digital computer equipped with a CPU, ROM, RAM, and an input / output interface.

[0020] The control unit 12 receives output signals from various sensors, including a vehicle speed sensor 25 for detecting the vehicle speed of the vehicle 1, a crank angle sensor 26 for detecting the crank angle of the crankshaft, and an accelerator position sensor 27, which acts as an accelerator position detection unit for detecting the amount the accelerator pedal is depressed (accelerator opening). The control unit 12 calculates the engine speed of the internal combustion engine 10 from the detection signal of the crank angle sensor 14. The control unit 12 is also capable of detecting the State of Charge (SOC), which is the ratio of the remaining charge to the charge capacity of the battery 8.

[0021] Furthermore, the control unit 12 can calculate the amount of exhaust particulate matter (PM) collected by the exhaust particulate filter 24 from the operating history of the internal combustion engine 10.

[0022] In vehicle 1, when the internal combustion engine 10 is stopped and decelerating, if the battery state of charge (SOC) is high, motoring is performed to prevent the battery 8 from becoming overcharged.

[0023] Figure 3 is an explanatory diagram showing the correlation between the power consumption of the electric heating catalyst 23, the engine speed during motoring, and the required deceleration force during vehicle deceleration. In Figure 3, the vertical axis represents the required deceleration force during vehicle deceleration, and the horizontal axis represents the engine speed of the internal combustion engine 10 during motoring.

[0024] The required deceleration force is the required deceleration energy calculated based on the deceleration request. The required deceleration energy is calculated based on the target vehicle deceleration corresponding to the accelerator opening, which is the deceleration request.

[0025] The thick solid line Q1 in Figure 3 represents the EHC consuming power, which is the power that can be energized. The solid line Q2 in Figure 3 represents the maximum EHC consuming power. The dashed line Q3 in Figure 3 represents the EHC power consumption when the electric heating catalyst 23 is set to a predetermined constant temperature. The double dashed line Q4 in Figure 3 represents the motoring power consumption that can be consumed by motoring.

[0026] Here, the amount of power that can be supplied to the electrically heated catalyst 23 varies depending on the temperature gradient and maximum temperature within the electrically heated catalyst. Therefore, the engine speed of the internal combustion engine 10 during motoring, which is necessary to maintain the required deceleration force, will be a different value depending on the required deceleration force.

[0027] In other words, the characteristic curve Q1, which represents the EHC's scalable power, the characteristic curve Q2, which represents the maximum EHC scalable power, and the characteristic curve Q3, which represents the EHC power consumption when the electric heating catalyst 23 is at a predetermined constant temperature, will each have different values ​​for the required engine speed depending on the required deceleration force.

[0028] The available EHC power is calculated based on the maximum available EHC power and the EHC power consumption. At the same engine speed, the available EHC power is the smaller of the maximum available EHC power and the EHC power consumption.

[0029] The maximum power that the EHC can consume is determined by the performance of the electric heating catalyst 23. In other words, the maximum power that the EHC can consume is the maximum power input that protects the function of the electric heating catalyst 23. Note that the maximum power that the EHC can consume decreases as the engine speed and the target temperature of the electric heating catalyst 23 decrease.

[0030] EHC power consumption is the power required when the electric heating catalyst 23 is controlled to a predetermined constant temperature (for example, the catalyst activation temperature). In other words, EHC power consumption is the power required to maintain the electric heating catalyst 23 at a predetermined target temperature.

[0031] Motoring power consumption is the power consumed by motorizing the internal combustion engine 10.

[0032] For example, if the required deceleration force is P1, and the goal is to consume regenerative energy during deceleration so that the required deceleration force is achieved solely through motoring, the engine speed during motoring must be R2. In this case, the operating point determined by the required deceleration force and engine speed is point T1 in Figure 3.

[0033] On the other hand, even when the required deceleration force is P1, if the electric heating catalyst 23 is energized during motoring, the engine speed during motoring can be reduced to R1, which is smaller than R2. In this case, the operating point determined by the required deceleration force and engine speed is point T2 in Figure 3.

[0034] Furthermore, for example, if the required deceleration force is P2, and the goal is to consume regenerative energy during deceleration so that the required deceleration force is achieved solely through motoring, the engine speed during motoring must be R4. In this case, the operating point determined by the required deceleration force and engine speed is point U1 in Figure 3.

[0035] On the other hand, even when the required deceleration force is P2, if the electric heating catalyst 23 is energized during motoring, the engine speed during motoring can be reduced to R3, which is smaller than R4. In this case, the operating point determined by the required deceleration force and engine speed is point U2 in Figure 3.

[0036] Therefore, the control unit 12 calculates the engine speed (target speed) of the internal combustion engine 10 during deceleration while the internal combustion engine 10 is stopped, in accordance with the required deceleration force and the available EHC power, in order to absorb regenerative energy, and controls the motoring to achieve this calculated engine speed.

[0037] In other words, as shown in Figure 3, the control unit 12 motors the engine so that, for example, when the required deceleration force is P1, the engine speed R1 corresponds to the operating point T2 on the characteristic curve Q1, and when the required deceleration force is P2, the engine speed R3 corresponds to the operating point U2 on the characteristic curve Q1.

[0038] Figure 4 is a flowchart showing an example of the control flow of vehicle 1 in this embodiment.

[0039] In step S1, it is determined whether or not vehicle 1 is decelerating. If it is determined in step S1 that vehicle 1 is decelerating, the process proceeds to step S2. If it is determined in step S1 that vehicle 1 is not decelerating, the process proceeds to step S7.

[0040] In step S2, the required deceleration force is calculated. The required deceleration force is calculated according to the accelerator opening, and the smaller the accelerator opening, the greater the required deceleration force. In step S3, it is determined whether or not energy consumption is necessary. In other words, in step S3, it is determined whether or not regenerative energy can be recovered (charged) into the battery 8. Specifically, if the current battery SOC of the battery 8 is greater than a predetermined SOC threshold, it is determined that energy consumption is necessary and the process proceeds to step S4. If the current battery SOC of the battery 8 is less than or equal to the above SOC threshold, it is determined that energy consumption is not necessary and the process proceeds to step S7. The above SOC threshold is a value set to protect the battery 8 and is set to determine whether or not the battery SOC is in a high state.

[0041] In step S4, it is determined whether or not there is a request for regeneration of the exhaust particulate filter 24. If it is determined in step S4 that there is no request for regeneration of the exhaust particulate filter 24, the process proceeds to step S5. If it is determined in step S4 that there is a request for regeneration of the exhaust particulate filter 24, the process proceeds to step S6.

[0042] Specifically, if the amount of exhaust particles collected in the exhaust particulate filter 24 (collection amount) is less than or equal to a preset accumulation threshold, the process proceeds to step S5. Also, if the amount of exhaust particles collected in the exhaust particulate filter 24 is less than or equal to the above accumulation threshold, the process proceeds to step S6.

[0043] In step S5, the engine speed is calculated based on the energy consumption target. Specifically, in step S5, the engine speed of the internal combustion engine 10 during motoring, which is necessary to consume the regenerative energy during deceleration, is calculated. The engine speed calculated in step S5 (target engine speed) is the engine speed of the internal combustion engine 10 during motoring, which is performed to absorb regenerative energy in accordance with the required deceleration force and the available EHC power, while the internal combustion engine 10 is stopped and decelerating. The specific calculation procedure in step S5 will be described later with reference to Figures 5 and 6.

[0044] Step S6 calculates the engine speed due to the regeneration request of the exhaust particulate filter 24 (GPF). That is, in step S6, while considering the regeneration of the exhaust particulate filter 24, the engine speed of the internal combustion engine 10 during motoring required to consume the regeneration energy during deceleration is calculated. The specific calculation procedure in step S6 will be described later using FIG. 7.

[0045] In step S7, the engine speed due to the energy management request, which is the drive request of the internal combustion engine 10 according to the battery SOC of the battery 8, is set. That is, it is set to the engine speed due to the drive request of the internal combustion engine 10 due to the decrease in the battery SOC of the battery 8, or the engine speed due to the drive request of the internal combustion engine 10 due to a high-load operation with high power consumption. The engine speed during the drive request due to the decrease in the battery SOC is, for example, the engine speed at the best fuel consumption point of the internal combustion engine 10. The engine speed during the drive request due to a high-load operation with high power consumption is, for example, the engine speed at an operating point on the high-speed and high-load side higher than the best fuel consumption point. The best fuel consumption point is a combination of the engine speed and load (torque) at which the fuel consumption of the internal combustion engine 10 including the power generation efficiency of the generator 9 is the best.

[0046] FIG. 5 is a flowchart showing a subroutine for calculating the engine speed according to the energy consumption target.

[0047] In step S51, the EHC consumable power is calculated. The specific calculation procedure in step S51 will be described later using FIG. 6.

[0048] In step S52, the engine speed (target engine speed) of the internal combustion engine 10 in motoring performed to absorb the regeneration energy is set (calculated) according to the required deceleration force and the EHC consumable power.

[0049] FIG. 6 is a flowchart showing a subroutine for calculating the EHC consumable power.

[0050] In step S511, the target temperature of the electric heating catalyst 23 due to energization is calculated. The target temperature is, for example, the activation temperature of the electric heating catalyst 23. Note that the target temperature may be a predetermined temperature set in advance other than the activation temperature of the electric heating catalyst 23.

[0051] In step S512, the current temperature of the electric heating catalyst 23 is detected. The temperature of the electric heating catalyst 23 may be detected, for example, by a temperature sensor, or it may be estimated from the resistance value (electrical resistance value) of the electric heating catalyst 23.

[0052] In step S513, the EHC power consumption is calculated. The EHC power consumption is the power required to raise the catalyst temperature of the electric heating catalyst 23 to a predetermined target temperature, and is calculated using the target temperature of the electric heating catalyst 23 and the detected current temperature of the electric heating catalyst 23.

[0053] In step S514, the available EHC power is calculated. The available EHC power is the smaller of the EHC power consumption and the maximum available EHC power (select row).

[0054] Figure 7 is a flowchart showing a subroutine that calculates the engine speed in response to a regeneration request for the exhaust particulate filter 24 (GPF).

[0055] In step S61, the target temperature of the electrically heated catalyst 23 is calculated by applying power. The target temperature in step S61 is set according to the amount of exhaust particulate matter deposited on the exhaust particulate matter filter 24 (collection amount). Specifically, the target temperature in step S61 is set to decrease as the amount of exhaust particulate matter deposited on the exhaust particulate matter filter 24 increases.

[0056] In step S62, the current temperature of the electric heating catalyst 23 is detected. The temperature of the electric heating catalyst 23 may be detected, for example, by a temperature sensor, or it may be estimated from the resistance value (electrical resistance value) of the electric heating catalyst 23.

[0057] In step S63, the EHC power consumption is calculated. The EHC power consumption is the power required to raise the catalyst temperature of the electric heating catalyst 23 to a predetermined target temperature, and is calculated using the target temperature of the electric heating catalyst 23 and the detected current temperature of the electric heating catalyst 23.

[0058] In step S64, the available EHC power is calculated. The available EHC power is the smaller of the EHC power consumption and the maximum available EHC power (select row).

[0059] In step S65, the engine speed (target engine speed) of the internal combustion engine 10 in motoring, which is performed to absorb regenerative energy in accordance with the required deceleration force and the available power for EHC, is set (calculated).

[0060] In the above-described embodiment, the vehicle 1 calculates the target rotational speed of the internal combustion engine 10 during motoring according to the required deceleration force and the EHC-consumable power of the electric heating catalyst 23. Therefore, even when the battery SOC is high, the desired deceleration can be obtained during deceleration.

[0061] Vehicle 1 can reduce the amount of power consumed during motoring by energizing the electrically heated catalyst 23 during motoring, thereby lowering the engine speed during motoring and reducing vibration.

[0062] Furthermore, by energizing the electric heating catalyst 23 during motoring, which is performed to consume regenerative energy, vehicle 1 can suppress the cooling of the electric heating catalyst 23, and the heat retention effect due to the heating of the electric heating catalyst 23 can improve the exhaust performance when combustion of the internal combustion engine 10 is restarted.

[0063] Since the available power consumption of the EHC changes depending on the temperature gradient and maximum temperature within the electric heating catalyst 23, the engine speed required during motoring to maintain the desired deceleration (target engine speed) will vary accordingly.

[0064] Therefore, by controlling the engine speed during motoring using the EHC-available power, vehicle 1 can achieve both energy (electricity) consumption through regeneration and securing the required deceleration force.

[0065] The EHC's available power is the lower of the maximum available EHC power and the EHC's power consumption. Therefore, compared to when regenerative energy is consumed solely by motoring, vehicle 1 can balance deceleration and regenerative energy consumption at lower rotational speeds.

[0066] Although specific embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0067] For example, the vehicle 1 may change at least one of the EHC consuming power and the engine speed of the internal combustion engine 10 during motoring based on the required deceleration force.

[0068] For example, if the system diagnosis (fault diagnosis) of the electric heating catalyst 23 is determined to be abnormal, the vehicle 1 may calculate the (target) engine speed of the internal combustion engine 10 during motoring, which is performed to absorb regenerative energy, by setting the available EHC power consumption to zero. This allows the vehicle 1 to ensure drivability and battery protection regardless of the condition of the electric heating catalyst 23. The system diagnosis (fault diagnosis) of the electric heating catalyst 23 determines, for example, whether there is a break in the circuit including the electric heating catalyst 23 and the battery 8, or whether there is an abnormality in the resistance value of the electric heating catalyst 23 due to a crack in the electric heating catalyst 23.

[0069] For example, when the exhaust particulate filter 24 is being regenerated, the target temperature of the exhaust particulate filter 24 may be set so that it can be regenerated and maintained within a temperature range that prevents it from overheating. This way, when a request for regeneration of the exhaust particulate filter 24 is made, the power supplied to the electric heating catalyst 23 and the engine speed of the internal combustion engine 10 during motoring are set so that the exhaust particulate filter 24 does not overheat and can be regenerated. Here, the upper limit of the temperature range in which the exhaust particulate filter 24 does not overheat is set, for example, according to the amount of exhaust particulate matter accumulated (collection amount) in the exhaust particulate filter 24, and the value becomes lower as the amount of accumulated exhaust particulate matter increases.

[0070] The above-described embodiment relates to a control method for a hybrid vehicle and a control device for a hybrid vehicle.

Claims

1. A control method for a hybrid vehicle having an internal combustion engine capable of motorization by an electric motor and an electrically heated catalyst arranged in the exhaust passage, wherein, when the internal combustion engine is decelerating while stopped, the method calculates the required deceleration energy based on the deceleration request, calculates the available power that can be supplied to the electrically heated catalyst, and calculates the engine speed of the internal combustion engine in the motorization performed to absorb regenerative energy according to the required deceleration energy and the available power.

2. A control method for a hybrid vehicle according to claim 1, wherein at least one of the energizable power and the engine speed of the internal combustion engine in the motoring is changed based on the required deceleration energy.

3. The control method for a hybrid vehicle according to claim 1, wherein the available power for determining the engine speed of the internal combustion engine in the motoring described above is the lower of the power required to maintain the electric heating catalyst at a predetermined target temperature and the maximum power required to protect the function of the electric heating catalyst.

4. If the system diagnostic result of the electric heating catalyst is determined to be abnormal, the method for controlling a hybrid vehicle according to claim 1, wherein the available power is set to zero and the engine speed of the internal combustion engine in the motoring performed to absorb regenerative energy is calculated.

5. A control method for a hybrid vehicle according to claim 3, wherein the exhaust passage downstream of the electric heating catalyst has an exhaust particulate filter for collecting exhaust particulate matter in the exhaust, and when the exhaust particulate filter is regenerated, the target temperature of the exhaust particulate filter is set so that the exhaust particulate filter can be regenerated and the exhaust particulate filter does not become overheated.

6. The control method for a hybrid vehicle according to claim 5, wherein the upper limit of the above temperature range is set according to the amount of exhaust particulate matter collected by the exhaust particulate filter.

7. A control device for a hybrid vehicle, comprising: an internal combustion engine capable of motorization by an electric motor; an electrically heated catalyst arranged in the exhaust passage; and a control unit that, when the internal combustion engine is decelerating while stopped, calculates the required deceleration energy based on the deceleration request, calculates the available power that can be supplied to the electrically heated catalyst, and calculates the engine speed of the internal combustion engine during motorization to absorb regenerative energy according to the required deceleration energy and the available power.

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