Hybrid vehicle control device

Abstract

To provide a hybrid vehicle control device that can effectively suppress the occurrence of rattle noise when a torque fluctuation straddling 0 Nm occurs on a drive shaft.SOLUTION: A hybrid vehicle control device includes: an engine torque detection unit that detects fluctuations in output torque of an engine; a torque fluctuation estimation unit that estimates fluctuations in rotational torque of a drive shaft; a torque change rate setting unit that sets the rate of change of the rotational torque of the drive shaft when the torque fluctuation estimation unit estimates a fluctuation in the rotational torque of the drive shaft straddling 0 Nm to a smaller value as the fluctuation value of the output torque of the engine is greater, and to a larger value as the fluctuation value of the output torque of the engine is smaller; and a torque control unit that controls the output torque of the engine and the output torque of the motor so that the rotational torque of the drive shaft changes according to the rate of change set by the torque change rate setting unit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] BACKGROUND ART A hybrid vehicle is known that includes an engine, a first motor generator, and a second motor generator that are connected to one another via a power transmission mechanism that has a planetary gear mechanism (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-251634 Summary of the Invention [Problem to be solved by the invention]

[0004] The rotation of the engine output shaft and the motor output shaft is transmitted to the power transmission mechanism. The drive shaft of a hybrid vehicle is included in the power transmission mechanism and rotates due to the output torque of the engine and motor, which are the power sources, respectively. The rotational torque of the drive shaft can alternate between positive and negative torque. When a hybrid vehicle accelerates, the torque of the drive shaft changes from negative torque, passing 0 Nm, to positive torque. When a hybrid vehicle decelerates, the torque changes from positive torque, passing 0 Nm, to negative torque. When torque fluctuations crossing 0 Nm like this occur, gear rattles can occur in various parts of the planetary gear mechanism in the power transmission mechanism. Gear rattles can be a source of discomfort to the driver.

[0005] In Patent Document 1, a limit value is set for the rate of change of engine speed. By limiting the rate of change of engine speed, the change in engine torque is limited. Therefore, it is thought that the occurrence of gear rattle noise can be suppressed by limiting the rate of change of engine speed and gradually changing the torque of the drive shaft.

[0006] However, Patent Document 1 does not mention suppressing the occurrence of gear rattle noise when torque fluctuations occur across 0 Nm.

[0007] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that can effectively suppress the occurrence of gear rattle noise when torque fluctuations across 0 Nm occur on the drive shaft. [Means for solving the problem]

[0008] The above object can be achieved by a control device for a hybrid vehicle having a drive shaft that rotates using an engine and a motor as power sources and a power transmission mechanism having a planetary gear mechanism connected to the drive shaft, the control device for a hybrid vehicle including: an engine torque detection unit that detects fluctuations in the output torque of the engine; a torque fluctuation estimation unit that estimates fluctuations in the rotational torque of the drive shaft; a torque change rate setting unit that sets the rate of change of the rotational torque of the drive shaft when the torque fluctuation estimation unit estimates that the rotational torque of the drive shaft crosses 0 Nm to a smaller value the greater the fluctuation value of the engine output torque, and to a larger value the smaller the fluctuation value of the engine output torque; and a torque control unit that controls the output torque of the engine and the output torque of the motor so that the rotational torque of the drive shaft changes in accordance with the rate of change set by the torque change rate setting unit. [Effects of the Invention]

[0009] It is possible to provide a control device for a hybrid vehicle that can effectively suppress the occurrence of gear rattle noise when torque fluctuations across 0 Nm occur on the drive shaft. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Figure 2] Fig. 2A is an example of a flowchart showing control of a hybrid vehicle, and Fig. 2B is an example of a map for setting the torque change rate based on engine torque fluctuations. [Figure 3] Figure 3A is a graph showing how the torque change rate is set when the rotational torque of the drive shaft changes from negative to positive torque across 0 Nm, and Figure 3B is a graph showing how the torque change rate is set when the rotational torque of the drive shaft changes from positive to negative torque across 0 Nm. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Hybrid vehicle configuration] FIG. 1 is a schematic diagram of a hybrid vehicle 1 according to this embodiment. The hybrid vehicle 1 includes an ECU (Electronic Control Unit) 100, an engine 10, a first motor (hereinafter referred to as a "first MG (Motor Generator)") 14, a second motor (hereinafter referred to as a "second MG") 15, a PCU (Power Control Unit) 17, a battery 18, a power transmission mechanism 50, a drive shaft 53, a differential 54, and drive wheels 55. The engine 10 may have any number of cylinders or any arrangement of cylinders. The engine 10 is a gasoline engine, but is not limited thereto and may be a diesel engine. The engine 10 is a power source for running the hybrid vehicle 1. The second MG 15, together with the engine 10, mainly serves as a power source for running the hybrid vehicle 1. The first MG 14 is mainly a power generation source.

[0012] Each of the first MG 14 and the second MG 15 functions as a motor that outputs torque when supplied with electric power, and as a generator that generates regenerative power when torque is applied to it. The first MG 14 and the second MG 15 are electrically connected to a battery 18 via a PCU 17. The PCU 17 supplies electric power from the battery 18 to the first MG 14 or the second MG 15. The PCU 17 causes the battery 18 to receive the regenerative power generated in the first MG 14 or the second MG 15.

[0013] A planetary gear mechanism is incorporated inside the power transmission mechanism 50. The power transmission mechanism 50 includes a power split mechanism and a reduction mechanism. The power transmission mechanism 50 mechanically connects the crankshaft of the engine 10, the output shaft of the first MG 14, the output shaft of the second MG 15, and a drive shaft 53 which is the output shaft of the power transmission mechanism 50. The drive shaft 53 extending from the power transmission mechanism 50 is sometimes referred to as a propeller shaft. The drive shaft 53 transmits the driving forces of the engine 10 and the second MG 15 to drive wheels 55. The rotational torque of the drive shaft 53 is a composite value of the torque of the engine 10 and the torque of the second MG 15.

[0014] When the rotational torque of the drive shaft 53 fluctuates across 0 Nm, rattle noise may occur in the planetary gear mechanism incorporated in the power transmission mechanism 50. When the rotational torque of the drive shaft 53 fluctuates across 0 Nm, the rotational torque may transition from positive torque to negative torque or from negative torque to positive torque. The gears used in the planetary gear mechanism have backlash. The gears are supported by bearings formed in a case or housing. When rotational torque is applied to the drive shaft 53, the tooth surfaces of the meshed gears are in contact with each other. However, when the rotational torque applied to the drive shaft 53 reaches 0 Nm, the tooth surfaces separate, creating play. Therefore, when the rotational torque of the drive shaft 53 fluctuates across 0 Nm, the gears that were in play once come into contact again. This may cause rattle noise. In this embodiment, control is implemented to suppress the occurrence of such rattle noise. This will be described in detail later.

[0015] The ECU 100 is an electronic control unit including a calculation processing circuit that performs various calculation processes related to the driving control of the hybrid vehicle 1, and a memory that stores control programs and data. The ECU 100 is an example of a control device for the hybrid vehicle 1. An accelerator opening sensor 101, a vehicle speed sensor 102, an air flow meter 103, and an in-cylinder pressure sensor 104 are electrically connected to the ECU 100. The accelerator opening sensor 101 detects the amount of operation of the accelerator pedal. The vehicle speed sensor 102 detects the vehicle speed of the hybrid vehicle 1. The air flow meter 103 detects the amount of intake air introduced into the engine 10. The in-cylinder pressure sensor 104 detects the pressure inside the cylinders of the engine 10.

[0016] The ECU 100 has sections that function as an engine torque detection section 100a, a torque fluctuation estimation section 100b, a torque change rate setting section 100c, and a torque control section 100d.

[0017] The engine torque detection unit 100a detects the output torque of the engine 10 based on the detection value of the in-cylinder pressure sensor 104. The engine torque detection unit 100a also acquires a fluctuation value of the detected output torque. In this embodiment, the output torque of the engine 10 is detected based on the detection value of the in-cylinder pressure sensor 104. The engine torque detection unit 100a may also acquire the output torque of the engine 10 by other conventionally known methods. For example, the output torque may be estimated based on the fuel injection amount, the ignition timing, and the ignition retard amount.

[0018] Torque fluctuation estimation unit 100b estimates fluctuations in the rotational torque of drive shaft 53 based on the detection value of accelerator opening sensor 101 and the detection value of vehicle speed sensor 102. Torque fluctuation estimation unit 100b also determines whether the estimated torque fluctuation of drive shaft 53 crosses 0 Nm.

[0019] The torque change rate setting unit 100c sets the rate of change in the rotational torque of the drive shaft 53 when the torque fluctuation estimation unit 100b estimates that the fluctuation in the rotational torque of the drive shaft 53 crosses 0 Nm. At this time, the rate of change in the rotational torque of the drive shaft 53 is set based on the output torque of the engine 10 detected by the engine torque detection unit 100a.

[0020] The output torque of the engine 10 detected by the engine torque detection unit 100a changes from moment to moment depending on the state of the engine 10 and the driving state of the hybrid vehicle 1. The torque change rate setting unit 100c sets a torque change rate that reflects the state of the engine 10 at any given time. The condition of the engine 10 differs for each hybrid vehicle 1. There are individual differences between engines 10. In other words, even with the same specifications and the same product, there may be differences in the way the output torque is generated depending on the assembly precision and the combination of parts. Furthermore, it is thought that the condition of the engine 10 changes as the driving distance of the hybrid vehicle 1 increases. Furthermore, it is thought that the output torque also differs depending on the driving environment of the hybrid vehicle 1.

[0021] The engine torque detection unit 100a detects the output torque of the engine 10 and obtains its fluctuation value, thereby making it possible to grasp the state of each individual engine 10 at any given time. Based on the output torque value and its fluctuation value thus obtained, the rate of change of the rotational torque of the drive shaft 53 is optimized. This effectively suppresses the occurrence of gear rattle noise without impairing drivability.

[0022] That is, in this embodiment, a common torque change rate is not set uniformly for each engine 10. In this embodiment, a torque change rate is set according to the condition of each individual engine 10 and the environment in which the engine 10 is placed at any given time.

[0023] Torque control section 100d controls the output torque of engine 10 and the output torque of second MG 15 so that the rotational torque of drive shaft 53 changes according to the rate of change set by torque change rate setting section 100c.

[0024] [Gear rattle noise prevention control] Next, the rattle noise prevention control will be described with reference to FIGS. 2A to 3B.

[0025] The engine 10 operates or stops depending on the state of the hybrid vehicle 1. In step S1 of the rattle noise avoidance control, the ECU 100 determines whether the engine 10 is operating. If the ECU 100 makes a positive determination (Yes determination) in step S1, it proceeds to step S2, and if the ECU 100 makes a negative determination (No determination), it proceeds to step S6.

[0026] In step S2, the engine torque detection unit 100a detects the output torque of the engine 10 and detects a torque fluctuation value from the detected output torque.

[0027] In step S3, which follows step S2, the torque change rate setting unit 100c sets the torque change rate of the drive shaft 53. The torque change rate is set, for example, based on the map shown in FIG. 2B. The horizontal axis of the map shown in FIG. 2B represents the value of the output torque fluctuation of the engine 10. The vertical axis represents the torque change rate. The torque change rate decreases as the torque fluctuation value of the engine 10 increases. The smaller the torque change rate, the longer it takes to achieve a predetermined amount of torque change. Furthermore, the larger the torque change rate, the shorter the time required to achieve a predetermined torque change. The smaller the torque change rate, the more gradual the contact between the gears, making it less likely that rattle noise will occur.

[0028] FIG. 3A shows the rate of change of torque when the rotational torque crosses 0 Nm and increases. FIG. 3B shows the rate of change of torque when the rotational torque crosses 0 Nm and decreases. Line segment L1 shown in FIGS. 3A and 3B shows an ideal rate of change of torque in response to the driver's accelerator operation. Lines showing the rate of change of torque when crossing 0 Nm are also shown in FIGS. 3A and 3B. However, although several lines are shown in FIGS. 3A and 3B for the sake of explanation, the rate of change of torque that is selected is not limited to these lines shown in FIGS. 3A and 3B. In other words, the rate of change of torque is flexibly set according to the value of the output torque fluctuation.

[0029] In step S4, which is performed following step S3, torque fluctuation estimation unit 100b estimates torque fluctuation of drive shaft 53 and determines whether the torque fluctuation crosses 0 Nm. If the ECU 100 makes a positive determination in step S4, the process proceeds to step S5. If the ECU 100 makes a negative determination in step S4, the process returns and the process from step S1 is repeated.

[0030] In step S5, torque control unit 100d controls the output torque of engine 10 and the output torque of second MG 15 so as to achieve the torque change rate set in step S3. This suppresses the occurrence of gear rattle noise. Since the torque change rate is set to an optimal value according to the output torque fluctuation value of engine 10, the effect on drivability is reduced. Thereafter, the process returns, and the process from step S1 is repeated.

[0031] In step S6, the ECU 100 determines whether the engine 10 is undergoing a start process or a stop process. The engine 10 starts or stops depending on the state of the hybrid vehicle 1. When the engine 10 starts or stops, the output torque of the engine 10 usually fluctuates. Therefore, first, in step S6, the ECU 100 determines whether the engine 10 is undergoing a start process or a stop process. If the ECU 100 determines yes in step S6, it proceeds to step S7, and if the ECU 100 determines no, it repeats the process from step S1.

[0032] In step S7, the torque change rate setting unit 100c sets the torque change rate of the drive shaft 53. However, unlike step S3, here the torque change rate is also set to the minimum value. This is because the output torque of the engine 10 usually fluctuates when the engine 10 starts and stops. This allows the gears to come into gentle contact with each other, making it less likely that rattle noise will occur.

[0033] Steps S8 and S9, which are performed following step S7, are common to steps S4 and S5, and therefore will not be described in detail here.

[0034] According to this embodiment, when a fluctuation in the rotational torque of the drive shaft 53 crossing 0 Nm is estimated, the rate of change of the rotational torque of the drive shaft 53 is set based on the output torque of the engine 10. This effectively suppresses the occurrence of gear rattle noise when torque fluctuations crossing 0 Nm occur in the drive shaft 53. Furthermore, drivability is ensured.

[0035] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0036] 1... hybrid vehicle, 10... engine, 14... first MG, 15... second MG, 50... power transmission mechanism, 53... drive shaft, 54... differential, 55... drive wheels, 100... ECU (control device), 100a... engine torque detection unit, 100b... torque fluctuation estimation unit, 100c... torque change rate setting unit, 100d... torque control unit

Claims

[Claim 1] A control device for a hybrid vehicle having a drive shaft that rotates using an engine and a motor as a power source, and a power transmission mechanism having a planetary gear mechanism connected to the drive shaft, an engine torque detection unit that detects a fluctuation value of the output torque of the engine; a torque fluctuation estimation unit that estimates fluctuations in the rotational torque of the drive shaft; a torque change rate setting unit that sets a rate of change of the rotational torque of the drive shaft when the torque fluctuation estimating unit estimates a fluctuation in the rotational torque of the drive shaft that crosses 0 Nm to a smaller value as the fluctuation value of the output torque of the engine increases, and sets a rate of change of the rotational torque of the drive shaft to a larger value as the fluctuation value of the output torque of the engine decreases; a torque control unit that controls the output torque of the engine and the output torque of the motor so that the rotational torque of the drive shaft changes according to the change rate set by the torque change rate setting unit; A control device for a hybrid vehicle comprising:

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