JP2017178016A - Hybrid vehicle and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid vehicle and a control method therefor, which reliably suppress a vibration due to resonance between an engine and an engine mount when the engine is stopped.SOLUTION: A vehicle includes a crank angle sensor 61 and a control apparatus 70. Further, the control apparatus 70 performs so that: in a period at least including a resonance period Δt within a period where an engine revolution speed Ne becomes zero after starting a stop operation of the engine 10, a resonance frequency fb is calculated on the basis of a coefficient of elasticity E of an engine mount 54; positive-negative signs of torque Tm of a motor-generator 21 are switched synchronously with the resonance frequency fb so that, based on angular velocity α, the torque Tm of the motor-generator 21 turns to negative in the case of the angular velocity α being positive whereas the torque of the motor-generator 21 turns to positive in the case of the angular velocity α being negative.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hybrid vehicle and a control method thereof, and more particularly to a hybrid vehicle that suppresses vibration when the engine is stopped and a control method thereof.

  In recent years, a hybrid vehicle (hereinafter referred to as “HEV”) including a hybrid system having an engine and a motor generator that are controlled in combination according to the driving state of the vehicle has attracted attention from the viewpoint of improving fuel efficiency and environmental measures. Yes. In this HEV, driving force is assisted by a motor generator when the vehicle is accelerated or started, while regenerative power generation is performed by the motor generator during inertial traveling or deceleration.

  With regard to such a hybrid vehicle, a device that switches between positive and negative torque of a motor generator when the engine is stopped has been proposed (see, for example, Patent Document 1). In this device, the torque of the motor generator is switched between positive and negative by the control device based on roll vibration caused by resonance between the engine and the engine mount that supports the engine on the vehicle body. And the roll vibration resulting from resonance is suppressed by switching the positive / negative of the torque.

JP 2007-127097 A

  However, in the above apparatus, the positive / negative of the torque of the motor generator is switched based on the roll angular acceleration caused by roll vibration. That is, in this apparatus, after the resonance between the engine and the engine mount occurs, control for suppressing roll vibration due to the resonance is started. In other words, since the start of the control is delayed with respect to the occurrence of the resonance, there is a problem that the vibration due to the resonance that occurs before the start of the control cannot be prevented due to the response delay.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hybrid vehicle and a control method therefor that can reliably suppress vibration due to resonance between the engine and the engine mount when the engine is stopped.

A hybrid vehicle of the present invention that achieves the above object includes an engine, an engine mount that supports the engine on a vehicle body, and a motor generator connected to an output shaft that transmits the power of the engine to drive wheels. The hybrid vehicle includes: an angular acceleration acquisition device that acquires angular acceleration of rotation on the output shaft; and a control device that is connected to the angular acceleration acquisition device and controls the engine and the motor generator. Thus, the rotation direction of one of the output shafts is a positive direction, the rotation direction opposite to the positive direction is a negative direction, the torque acting in the positive direction of the output shaft is a positive torque, and the negative direction of the output shaft is The period from when the engine stop operation is started to when the engine rotation speed becomes zero, assuming that the torque acting on the engine is negative torque A resonance frequency between the engine and the engine mount is calculated based on an elastic coefficient of the engine mount in a period including at least a resonance period in which the engine and the engine mount resonate, and the torque of the motor generator is calculated. Is switched in synchronization with the resonance frequency, and based on the angular acceleration acquired by the angular acceleration acquisition device, the torque of the motor generator becomes negative when the angular acceleration is positive, while the angular acceleration is In the negative case, the motor generator has a positive torque.

  In addition, the hybrid vehicle control method of the present invention that achieves the above-described object provides a motor generator connected to an output shaft that transmits engine driving force to driving wheels when the engine supported by the vehicle body by the engine mount is stopped. In the hybrid vehicle control method for controlling the torque, the rotation direction of one of the output shafts is a positive direction, the rotation direction opposite to the positive direction is a negative direction, and the torque acting in the positive direction of the output shaft is a positive direction. The torque acting in the negative direction of the output shaft is a negative torque, and the vibration of the engine and the engine mount in the period from when the engine stop operation is started until the engine rotation speed becomes zero. Based on an elastic coefficient of the engine mount, the engine and the air are at least including a resonance period in which vibration resonates. The resonance frequency with the gin mount is acquired, the angular acceleration of rotation on the output shaft is acquired, the torque of the motor generator is negative when the angular acceleration is positive, and the angular acceleration is synchronized with the resonance frequency. Is a method in which the torque of the motor generator is switched to a positive value when is negative.

  According to the hybrid vehicle and the control method thereof of the present invention, when the engine is stopped, the switching between positive and negative of the torque of the motor generator is synchronized with the resonance frequency according to the elastic coefficient of the engine mount, and the torque is output to the angular acceleration of the output shaft. Generate in a direction that counteracts the change. That is, since the timing of switching the torque of the motor generator according to the resonance frequency is planned, the change in angular acceleration of the output shaft during the resonance period can be suppressed without actually measuring the resonance between the engine and the engine mount. Therefore, a delay in control response to resonance can be avoided, and vibration caused by resonance between the engine and the engine mount when the engine is stopped can be reliably suppressed.

It is a block diagram of the hybrid vehicle which consists of embodiment of this invention. It is a correlation diagram which illustrates the relationship between a frequency ratio and a vibration transmissibility. It is a correlation diagram which illustrates the relationship between time at the time of an engine stop, and engine speed. It is a flowchart which illustrates the control method of the hybrid vehicle of this invention. It is a figure which illustrates the relationship between the temperature around an engine mount, and an elastic coefficient. It is a figure which illustrates the relationship between the temperature around an engine mount, the resonance frequency, and the vibration level of resonance. FIG. 5 is a flowchart illustrating details of a step of calculating a resonance frequency in FIG. 4.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hybrid vehicle according to an embodiment of the present invention. In the following description, the rotation direction of the crankshaft 13 is a positive direction x, and the opposite direction of the rotation direction is a negative direction y.

  This hybrid vehicle (hereinafter referred to as “HEV”) is a normal passenger car or a large vehicle such as a bus or a truck, and is a hybrid that controls the vehicle in combination with the engine 10, the motor generator 21, the transmission 30, and the driving state. System 20 is mainly provided.

In the engine 10, the crankshaft 13 is rotationally driven by thermal energy generated by the combustion of fuel in a plurality (four in this example) of cylinders 12 formed in the engine body 11. The engine 10 is a diesel engine or a gasoline engine. One end of the crankshaft 13 is connected to one end of a rotating shaft 22 of the motor generator 21 via an engine clutch 14 (for example, a wet multi-plate clutch).

  The motor generator 21 is a permanent magnet AC synchronous motor capable of generating operation. The other end of the rotating shaft 22 of the motor generator 21 is connected to an input shaft 31 of the transmission 30 through a transmission clutch 15 (for example, a wet multi-plate clutch).

  The transmission 30 uses an AMT or an AT that automatically shifts to a target gear determined based on the HEV operating state and preset map data. The transmission 30 is not limited to an automatic transmission type such as AMT, and may be a manual type in which a driver manually changes gears.

  The rotational power changed by the transmission 30 is transmitted to the differential 34 through the propeller shaft 33 connected to the output shaft 32, and is distributed as a driving force to the pair of driving wheels 35 as rear wheels.

  The hybrid system 20 includes a motor generator 21, an inverter 23 electrically connected to the motor generator 21, a high voltage battery 24, a DC / DC converter 25, and a low voltage battery 26.

  Preferred examples of the high voltage battery 24 include a lithium ion battery and a nickel metal hydride battery. The low voltage battery 26 is a lead battery.

  The DC / DC converter 25 has a function of controlling the charge / discharge direction and the output voltage between the high voltage battery 24 and the low voltage battery 26. The low voltage battery 26 supplies power to various vehicle electrical components 27.

  Various parameters in the hybrid system 20 such as a current value, a voltage value, and an SOC are detected by the BMS 28.

  The engine 10 and the hybrid system 20 are controlled by the control device 70. Specifically, when the HEV starts or accelerates, the hybrid system 20 assists at least a part of the driving force by the motor generator 21 supplied with power from the high voltage battery 24. On the other hand, during inertial running or braking, regenerative power generation is performed by the motor generator 21, and surplus kinetic energy generated in the propeller shaft 33 or the like is converted into electric power to charge the high voltage battery 24. Further, this HEV can perform so-called motor independent travel using only the motor generator 21 as a drive source by disengaging the engine clutch 14 and engaging the transmission clutch 15.

  The output shaft that transmits the driving force of the engine 10 connected to the motor generator 21 to the driving wheels 35 is exemplified by the crankshaft 13, the shafts of the transmission 30, and the propeller shaft 33. As a connection mechanism between the motor generator 21 and their output shafts, an endless belt-like member is provided between the first pulley attached to the rotary shaft 22 and the second pulley attached to these output shafts. Examples include a hung mechanism, a speed reduction mechanism such as a gear box, and a power take-out mechanism such as a PTO.

  The HEV also includes a plurality of engine mounts 54 that support the engine 10 on a vehicle body (not shown). The engine mount 54 is interposed between the lower end of the engine body 11 and the upper end of the vehicle body, and is configured to be elastically deformable in the vertical direction. The engine mount 54 is exemplified by a configuration having an elastic body such as rubber interposed between the lower end of the engine body 11 and the upper end of the vehicle body. Moreover, you may have the chamber in which the liquid was enclosed instead of the elastic body.

  In an HEV equipped with this type of engine mount 54, for example, when the HEV is stopped and the condition for stopping the engine 10 is satisfied (a so-called idle stop state), the control device 70 determines that the engine 10 is to be stopped. A stop command for the engine 10 is issued by the device 70. Next, the stop operation of the engine 10 is started in response to the stop command. As a specific stop operation, stop of fuel injection of an injector (not shown) of the engine body 11 is exemplified. Then, the engine speed Ne of the engine 10 becomes zero, and the engine 10 stops.

  FIG. 2 illustrates the relationship between the frequency ratio (fa / fb) and the vibration transmissibility. Note that fa represents the frequency of vibration in the engine 10, and fb represents the resonance frequency between the engine 10 and the engine mount 54.

  The main component of the vibration frequency fa in the engine 10 is determined by the arrangement of the cylinders 12. For example, in the case of an in-line four cylinder as in this embodiment, the secondary component of rotation is the main component. That is, the frequency fa here indicates the frequency of the secondary component in the case where the engine rotation speed Ne of the engine 10 is the normal rotation speed set to be equal to or higher than the idling rotation speed.

  The resonance frequency fb between the engine 10 and the engine mount 54 is set so that the vibration transmissibility at the normal rotation speed is smaller than 1 based on the frequency fa. That is, when the engine rotational speed Ne is the normal rotational speed, the frequency ratio fa / fb is in a range larger than “1”. Therefore, in the process of stopping the engine 10, the resonance point where the frequency ratio fa / fb is “1”. Will pass. Remarkable resonance occurs when passing through this resonance point.

  FIG. 3 illustrates the relationship between the passage of time and the engine rotation speed when the engine 10 is stopped. In the figure, the solid line indicates the rotational fluctuation of the crankshaft 13 of the engine 10. At time t1, the control device 70 issues a stop command for the engine 10 and starts the stop operation of the engine 10. When the engine rotation speed Ne decreases due to this stop operation, the angular acceleration α of the crankshaft 13 increases in the positive direction x or increases in the negative direction y according to the frequency fa. Since the frequency fa coincides with the resonance frequency fb in the resonance period Δt from the time t2 to the time t3, resonance between the engine 10 and the engine mount 54 occurs. In particular, at time t4, significant resonance occurs when passing through the resonance point.

  Therefore, in the HEV described above, an angular acceleration acquisition device (hereinafter referred to as a crank angle sensor) 61 that acquires an angular acceleration α of rotation on the output shaft, and the engine 10 and the motor generator 21 are controlled by being connected to the crank angle sensor 61. And a control device 70. The HEV is calculated for a predetermined period until the engine 10 is stopped based on the elastic coefficient E of the engine mount 54 by the control device 70 and the resonance frequency fb between the engine 10 and the engine mount 54 is calculated. In this configuration, the sign of the torque Tm of the motor generator 21 is switched in synchronization with the resonance frequency fb. At this time, based on the angular acceleration α, the control device 70 causes the torque of the motor generator 21 to be negative when the angular acceleration α is positive, while the motor generator 21 detects that the angular acceleration α is negative. In this configuration, the torque becomes positive.

  Here, the torque acting in the positive direction x of the crankshaft 13 is defined as positive torque, and the torque acting in the negative direction y of the crankshaft 13 is defined as negative torque. That is, the positive torque of the motor generator 21 means that a driving force is applied from the motor generator 21 to the crankshaft 13. On the other hand, the fact that the torque of the motor generator 21 becomes negative means that the motor generator 21 generates power by the driving force transmitted from the crankshaft 13.

  The HEV also includes a temperature acquisition device (hereinafter referred to as a temperature sensor) 65 that acquires the temperature Ta around the engine mount 54, and the resonance frequency fb is calculated by the control device 70 based on the temperature Ta. It is.

  The crank angle sensor 61 is a sensor that detects the crank angle of the crankshaft 13. The crank angle sensor 61 detects the crank angle from a pulse signal. Therefore, the angular acceleration α of the crankshaft 13 is acquired by measuring the time between the pulse signals by the control device 70. As the angular acceleration acquisition device, the crankshaft 13 is exemplified as the output shaft in this embodiment, and therefore, the crank angle sensor 61 that detects the angular acceleration α of the rotation in the crankshaft 13 is exemplified. As this angular acceleration acquisition device, in addition to the crank angle sensor 61, a rotational speed sensor capable of acquiring the angular acceleration α of the rotation of the crankshaft 13 is exemplified.

  In this embodiment, the temperature sensor 65 is a sensor that measures the temperature of the cooling water of the engine 10. The controller 70 estimates the temperature Ta around the engine mount 54 from the temperature in the engine room based on the cooling water temperature of the engine 10 acquired via the temperature sensor 65.

  The temperature acquisition device may be any device that can acquire the temperature Ta around the engine mount 54. In addition to the temperature sensor 65, the temperature acquisition device is arranged around the engine mount 54 to obtain the ambient temperature Ta. Examples are sensors that detect and sensors that detect outside air temperature. Since the elastic coefficient E of the engine mount 54 changes with respect to the temperature Ta around the engine mount 54, a temperature sensor 65 arranged around the engine mount 54 is preferably exemplified as the temperature acquisition device. Moreover, the sensor which is arrange | positioned at the engine mount 54 and detects the temperature of the engine mount 54 directly is illustrated.

  The control device 70 includes a CPU that performs various processes, an internal storage device that can read and write programs and processing results used to perform the various processes, and various interfaces. The control device 70 is connected to each of the crank angle sensor 61 and the temperature sensor 65 via a signal line (indicated by a one-dot chain line). The control device 70 is connected to each of the inverters 23 that control the torque of the engine body 11 and the motor generator 21 via signal lines.

  Examples of the execution program stored in the internal storage device of the control device 70 include an output control program for the motor generator 21 that is executed when the engine 10 is stopped.

The output control program is a program that is executed based on a stop command for the engine 10. The output control program is a period including at least a resonance period Δt of a period from when the engine 10 stop command is issued until the engine rotational speed Ne of the engine 10 becomes zero. This program switches between positive and negative. Note that the control device 70 may include hardware having the functional elements instead of the output control program.

  The resonance period Δt includes a resonance point where the vibration frequency fa of the engine 10 and the resonance frequency fb of the engine mount 54 coincide, that is, a resonance point where the frequency ratio fa / fb is “1” and before and after the resonance point. It is. In FIG. 3, the time t4 is the resonance point, and the time period t2 to the time t3 including the interval before and after that is the resonance period Δt.

  However, it is difficult to measure the resonance period Δt with high accuracy, and if the start time is measured, a control response delay occurs. Therefore, the first angle between time t1 and t2 is the period from when the engine 10 stop command is issued and the engine 10 is stopped (time t1) until the engine speed Ne becomes zero. It is preferable to detect the acceleration peak P1 and switch between positive and negative of the torque Tm of the motor generator 21 from that point. Controlling the motor generator 21 in this way is advantageous in avoiding a delay in control response to resonance.

  This HEV control method will be described below as a function of the control device 70 with reference to FIG. As described above, this control method is started when the control device 70 issues a stop command for the engine 10.

  First, when a command to stop the engine 10 is issued, the control device 70 calculates a resonance frequency fb corresponding to the elastic coefficient E of the engine mount 54 (S10). The elastic coefficient E of the engine mount 54 is set as a reference value depending on the configuration of the engine mount 54. The resonance frequency fb has a positive correlation with the elastic coefficient E. Therefore, in this step, it is preferable to obtain the elastic coefficient E of the engine mount 54 in advance by experiments or tests and store the resonance frequency fb corresponding to the elastic coefficient E in the internal storage device.

  On the other hand, this elastic coefficient E is a value that varies depending on the temperature Ta around the engine mount 54. That is, it is desirable to calculate the resonance frequency fb based on the temperature Ta around the engine mount 54. Details of the method of calculating the resonance frequency fb will be described later.

  Next, the control device 70 acquires the detection value of the crank angle sensor 61 via the signal line, and acquires the angular acceleration α of the crankshaft 13 (S20). More specifically, the sign of the angular acceleration α is acquired in this step.

  Here, the angular acceleration α is positive when the angular acceleration α is in the positive direction x, and the angular acceleration α is negative when the angular acceleration α is in the negative direction y.

  Next, the control device 70 synchronizes with the calculated resonance frequency fb and switches the torque Tm of the motor generator 21 to negative when the acquired angular acceleration α is positive. On the other hand, when the angular acceleration α is negative, the torque Tm of the motor generator 21 is switched to positive (S30). More specifically, after the stop command for the engine 10 is generated, the sign of the torque Tm of the motor generator 21 is switched from the peak P1 of the first angular acceleration α as a starting point.

  That is, when the angular acceleration α is positive, the motor generator 21 is caused to generate electric power by the driving force from the crankshaft 13 to cancel the angular velocity change in the positive direction x. Further, when the angular acceleration α is negative, the motor generator 21 applies a driving force to the crankshaft 13 to cancel the angular velocity change in the negative direction y.

Next, the control device 70 acquires the detection value of the crank angle sensor 61 via the signal line, and determines whether or not the engine rotational speed Ne has become zero (S40). In this step, if it is determined that the engine rotational speed Ne has become zero, the process proceeds to the next step. On the other hand, if it is determined that the engine rotational speed Ne has not become zero, the positive / negative switching of the torque Tm of the motor generator 21 is continued.

  Next, the control device 70 stops the motor generator 21, and this control method is completed.

  By performing such control, the timing for switching the torque Tm of the motor generator 21 according to the resonance frequency fb can be achieved. That is, the change in the angular velocity of the crankshaft 13 during the resonance period Δt can be suppressed without actually measuring the resonance between the engine 10 and the engine mount 54. Therefore, vibration caused by resonance between the engine 10 and the engine mount 54 when the engine 10 is stopped can be reliably suppressed.

  5 illustrates the relationship between the temperature Ta and the elastic coefficient E of the engine mount 54, and FIG. 6 illustrates the relationship between the resonance (resonance frequency and vibration level) of the engine 10 and the temperature Ta. . T1, T2, and T3 each indicate a temperature Ta, and are higher in the order of temperature T3, temperature T2, and temperature T1. Further, f1, f2, and f3 respectively indicate the resonance frequency fb, and are higher in order of the resonance frequency f1, the resonance frequency f2, and the resonance frequency f3.

  As shown in FIG. 5, the elastic coefficient E of the engine mount 54 has a substantially inversely proportional relationship with the temperature Ta around the engine mount 54. As described above, the vibration between the engine 10 and the engine mount 54 has a positive relationship with the elastic coefficient E of the engine mount 54. Therefore, as shown in FIG. 6, the resonance frequency fb of the vibration has a negative relationship with the temperature Ta.

  Therefore, in the step of calculating the resonance frequency fb, it is desirable that the control device 70 calculates the resonance frequency fb based on the temperature Ta. More specifically, map data M1 as shown in FIG. 6 is stored in the internal storage device in advance, and the temperature Ta detected by the temperature sensor 65 is compared with the map data M1 to determine the resonance frequency fb. The method of calculating is illustrated.

  The map data M1 referred to here is set with the relationship between the resonance frequency fb and the temperature Ta as shown in FIG. The map data M1 is not limited to that shown in FIG. 6 as long as at least the correlation between the resonance frequency fb and the temperature Ta is set.

  Hereinafter, the control method in this step will be described as a function of the control device 70 with reference to the flowchart of FIG.

  First, the control device 70 obtains the temperature Ta around the engine mount 54 by estimating from the detection value of the temperature sensor 65 via the signal line (S12). Next, the control device 70 refers to the map data M1 stored in advance in the internal storage device (S14). Next, the control device 70 compares the temperature Ta with the map data M1 and calculates the resonance frequency fb (S16).

  The resonance frequency fb calculated in this way becomes lower when the temperature Ta becomes higher and becomes higher when the temperature Ta becomes lower. For example, the resonance frequency f1 at the resonance point at the temperature T1 is lower than the resonance frequency f3 at the resonance point at the temperature T3.

  As shown in FIG. 6, the resonance frequency fb gradually decreases in the process in which the engine rotation speed Ne goes to zero. Therefore, the timing for switching between positive and negative of the torque Tm of the motor generator 21 should be gradually delayed by synchronizing with the resonance frequency fb.

  Thus, by calculating the resonance frequency fb based on the temperature Ta around the engine mount 54, it is possible to control the timing for switching the torque Tm of the motor generator with high accuracy corresponding to the resonance frequency fb that changes from the temperature Ta. become. Therefore, it is advantageous for suppressing resonance between the engine 10 and the engine mount 54.

10 Engine 13 Crankshaft 21 Motor generator 54 Engine mount 61 Crank angle sensor 65 Temperature sensor 70 Controller E Elastic coefficient Ne Engine rotation speed Tm Torque fb Resonance frequency Δt Resonance period α Angular acceleration

Claims (4)

In a hybrid vehicle comprising an engine, an engine mount that supports the engine on a vehicle body, and a motor generator connected to an output shaft that transmits the power of the engine to driving wheels,
An angular acceleration acquisition device that acquires angular acceleration of rotation on the output shaft, and a control device that is connected to the angular acceleration acquisition device and controls the engine and the motor generator,
With this control device,
One direction of rotation of the output shaft is defined as the positive direction, the direction of rotation opposite to the positive direction is defined as the negative direction, the torque acting in the positive direction of the output shaft is defined as the positive torque, and the rotational direction is exerted in the negative direction of the output shaft As a negative torque,
In a period including at least a resonance period in which the engine and the engine mount resonate in a period from when the engine stop operation is started to when the engine rotation speed becomes zero,
Based on the elastic coefficient of the engine mount, the resonance frequency of the engine and the engine mount is calculated, and the positive / negative of the torque of the motor generator is switched in synchronization with the resonance frequency,
Based on the angular acceleration acquired by the angular acceleration acquisition device, the torque of the motor generator becomes negative when the angular acceleration is positive, while the torque of the motor generator becomes positive when the angular acceleration is negative. A hybrid vehicle characterized by having the following structure. A temperature acquisition device for acquiring the temperature around the engine mount;
The hybrid vehicle according to claim 1, wherein the resonance frequency is calculated by the control device based on a temperature acquired by the temperature acquisition device.   Based on the first peak of the angular acceleration acquired by the angular acceleration acquisition device after the engine stop operation is started, the control device switches the positive / negative of the torque of the motor generator starting from the peak. The hybrid vehicle according to claim 1 or 2. In the control method of the hybrid vehicle that controls the torque of the motor generator connected to the output shaft that transmits the driving force of the engine to the drive wheels when the engine supported by the vehicle body by the engine mount is stopped.
One direction of rotation of the output shaft is defined as the positive direction, the direction of rotation opposite to the positive direction is defined as the negative direction, the torque acting in the positive direction of the output shaft is defined as the positive torque, and the rotational direction is exerted in the negative direction of the output shaft As a negative torque,
In a period including at least a resonance period in which the vibration of the engine and the vibration of the engine mount resonate in a period from when the engine stop operation is started to when the engine rotation speed becomes zero,
Based on the elastic coefficient of the engine mount, obtain a resonance frequency between the engine and the engine mount,
Obtaining the angular acceleration of rotation on the output shaft;
Synchronously with the resonance frequency, the hybrid vehicle switches the torque of the motor generator negative when the angular acceleration is positive, and switches the torque of the motor generator positive when the angular acceleration is negative. Control method.