JP2004225623A - Control device and method for starting engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exactly detect the top dead center of a piston in starting an engine. <P>SOLUTION: This detection method for top dead center includes a step (S120) for calculating an angular speed of a time change in the displacement angle of a resolver provided on a motor generator cranking the engine; a step (S140) for calculating an angular acceleration of a time change of an angular speed; and a step (S190) for determining a position of an inflection point as the top dead center of the piston when a variance in the angular acceleration is larger than its threshold value A (Yes in S180). The inflection point (a minimum point) of the angular acceleration is determined as the compression top dead center in which the direction of a force applied onto the piston changes from a negative (compression) to a positive (expansion). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology for detecting a position of a piston of an engine, and particularly to a technology for detecting that a piston is at a compression top dead center.
[0002]
[Prior art]
A vehicle equipped with a power train called a hybrid system in which an engine (for example, a known engine such as a gasoline engine or a diesel engine may be used) and an electric motor has been developed and put into practical use. In such a vehicle, the operation by the engine and the operation by the electric motor are automatically switched irrespective of the accelerator operation amount of the driver, and are controlled so that the efficiency is maximized. For example, when the engine is operated in a steady state to operate a generator that charges the secondary battery, or when the engine is operated intermittently during traveling according to the charge amount of the secondary battery, and the like. Repeatedly starts and stops the engine irrespective of the accelerator operation amount by the driver. That is, by operating the engine and the electric motor independently or in cooperation with each other, it is possible to improve fuel consumption and significantly suppress exhaust gas.
[0003]
As described above, the engine of the hybrid vehicle is intermittently driven even during traveling, and the stop control is frequently performed. When performing engine stop control, if the rotation of the engine is rapidly reduced, vibration or noise may be caused. Japanese Patent Laying-Open No. 2001-207885 (Patent Literature 1) discloses an engine stop control for a hybrid vehicle in which the fluctuation of friction at the time of engine stop control is reduced to suppress vibration and stop the engine smoothly and quickly. An apparatus is disclosed. The control device disclosed in Patent Document 1 includes an engine and a motor generator, and controls the stop of the engine of a hybrid vehicle in which the operating state of the engine can be controlled by the motor generator. The control device switches a state detection circuit that detects an operation state of the engine after an instruction to stop the engine and a suppression control amount for suppressing engine operation by the motor generator according to the operation state of the engine. And a control switching circuit for canceling the friction fluctuation. The state detection circuit detects passage of the engine piston at top dead center, and the control switching circuit controls the motor generator suppression control amount to decrease immediately before passing the top dead center, and immediately after passing the top dead center, Is controlled to increase. Further, the state detection circuit detects the passage of the engine top dead center by detecting the crank angle of the engine.
[0004]
According to the control device disclosed in Patent Document 1, the control amount of the motor generator can be selected to an optimum value according to the operating state of the engine after the stop instruction to the engine. The operation of the engine is suppressed by applying the torque, and the fluctuation of the friction can be suppressed. The state detection circuit, for example, detects the crank angle accurately and quickly based on a signal from a resolver or the like provided in the motor generator, and before and after passing the top dead center, that is, the change in friction due to compression and expansion is largest. At this time, the control amount for suppressing the engine operation by the motor generator is increased or decreased. For this reason, it is possible to suppress a change in friction between the state passing through the top dead center and another state. As a result, vibration of the engine can be suppressed.
[0005]
[Patent Document 1]
JP 2001-207885 A
[0006]
[Problems to be solved by the invention]
However, the control device disclosed in Patent Document 1 merely detects whether or not the piston is located near the top dead center by detecting the crank angle based on a signal from the resolver when the engine is stopped. Therefore, the top dead center position cannot be accurately determined until the next engine start (during cranking). That is, when the engine is started, the cranking speed is low, so that even if the top dead center is detected based on the detected crank angle, the accuracy is not good. Similarly, even if a top dead center sensor is provided in the engine to detect the top dead center, the cranking speed is low when the engine is started. Also, providing a top dead center sensor for each cylinder of the engine leads to an increase in cost.
[0007]
Further, when the engine is stopped, since the engine has been rotating so far, the crank angle can be accurately detected by integrating the displacement angle of the resolver from the piston top dead center signal detected last. On the other hand, when the engine is started, since the engine has not yet been rotated, an accurate crank angle cannot be detected until the first piston top dead center signal comes. In particular, in a hybrid system, when the engine and the motor generator are connected via the clutch, the positional relationship between the engine and the motor generator changes every time the clutch is released, and it has been known until then. Even if the displacement angle of the resolver is integrated based on the positional relationship, the crank angle cannot be calculated.
[0008]
The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an engine start control device and an engine start control method capable of accurately detecting a top dead center of a piston at the time of engine start. To provide.
[0009]
[Means for Solving the Problems]
A control device according to a first invention is an engine start control device for determining a piston top dead center when starting an engine with a motor. The control device includes a detecting unit for detecting a rotational angular velocity of the crankshaft during cranking, and a determining unit for determining a top dead center based on a detection result of the rotational angular speed.
[0010]
According to the first aspect, the detecting means detects the rotational angular velocity of the crankshaft connected to the piston, and the determining means uses the detection result of the rotational angular velocity to obtain a rotational angular acceleration which is a time change of the rotational angular velocity. Is calculated. At the inflection point (minimum point) of the rotational angular acceleration, the direction of the force applied to the piston changes from negative (compression) to positive (expansion). judge. As a result, it is possible to provide an engine start control device capable of accurately detecting the top dead center of the piston when starting the engine.
[0011]
In the engine start control device according to the second invention, in addition to the configuration of the first invention, the detection means includes means for detecting a rotational angular velocity of the motor during cranking.
[0012]
According to the second aspect, the rotational angular velocity of the motor during cranking is detected and processed as the rotational angular velocity of the crankshaft, whereby the top dead center of the piston at the time of starting the engine can be accurately detected.
[0013]
In the engine start control device according to the third invention, in addition to the configuration of the second invention, the detection means detects the rotation angular velocity based on a signal output from a rotation resolver provided in the motor. Including means.
[0014]
According to the third invention, the rotational angular velocity of the motor during cranking is detected using a signal output from a resolver provided in the motor, and is processed as the rotational angular velocity of the crankshaft. Can be detected more accurately.
[0015]
In the engine start control device according to the fourth invention, in addition to the configuration of any one of the first to third inventions, the determining means detects an inflection point of the rotational angular acceleration from the rotational angular velocity, and Means for determining the top dead center based on
[0016]
According to the fourth invention, the determination means determines that the direction of the force applied to the piston changes from negative (compression) to positive (expansion) at the inflection point (minimum point) of the rotational angular acceleration, so that the top death occurs. Since the point is determined, the top dead center of the piston at the time of starting the engine can be accurately detected.
[0017]
A control method according to a fifth invention is an engine start control method for determining a piston top dead center when starting an engine with a motor. This control method includes a detecting step of detecting a rotational angular velocity of a crankshaft during cranking, and a determining step of determining a top dead center based on a detection result of the rotational angular velocity.
[0018]
According to the fifth aspect, in the detecting step, the rotational angular velocity of the crankshaft connected to the piston is detected, and in the determining step, the rotational angular velocity, which is a time change of the rotational angular velocity, is used by using the detection result of the rotational angular velocity. Calculate the angular acceleration. In the determination step, at the inflection point (minimum point) of the rotational angular acceleration, the direction of the force applied to the piston changes from negative (compression) to positive (expansion). Is determined. As a result, it is possible to provide an engine start control method capable of accurately detecting the top dead center of the piston when starting the engine.
[0019]
In the engine start control device according to the sixth aspect, in addition to the configuration of the fifth aspect, the detecting step includes a step of detecting a rotational angular velocity of the motor during cranking.
[0020]
According to the sixth aspect, the rotational angular velocity of the motor during cranking is detected and processed as the rotational angular velocity of the crankshaft, whereby the top dead center of the piston at the time of starting the engine can be accurately detected.
[0021]
In the engine start control device according to the seventh invention, in addition to the configuration of the sixth invention, the detecting step includes a step of detecting a rotational angular velocity based on a signal output from a rotary resolver provided in the motor. Including.
[0022]
According to the seventh aspect, the rotational angular velocity of the motor during cranking is detected using a signal output from a resolver provided in the motor, and is processed as the rotational angular velocity of the crankshaft. Can be detected more accurately.
[0023]
In the engine start control device according to the eighth aspect, in addition to the configuration of any one of the fifth to seventh aspects, the determining step detects an inflection point of the rotational angular acceleration from the rotational angular velocity, and Determining the top dead center based on
[0024]
According to the eighth aspect, the determination means determines that the direction of the force applied to the piston changes from negative (compression) to positive (expansion) at the inflection point (minimum point) of the rotational angular acceleration. Since the point is determined, the top dead center of the piston at the time of starting the engine can be accurately detected.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are the same. Therefore, detailed description thereof will not be repeated.
[0026]
A control block diagram of a hybrid vehicle according to an embodiment of the present invention will be described with reference to FIG. The present invention is not limited to the hybrid vehicle shown in FIG. A hybrid vehicle having another aspect may be used.
[0027]
The hybrid vehicle includes, as drive sources, an internal combustion engine (hereinafter simply referred to as an engine) 120 such as a gasoline engine or a diesel engine, and a motor generator (MG) 140. In FIG. 1, motor generator 140 is expressed as motor 140A and generator 140B (or motor generator 140B) for convenience of description, but motor 140A functions as a generator depending on the running state of the hybrid vehicle, The generator 140B functions as a motor.
[0028]
The hybrid vehicle also includes a speed reducer 180 that transmits power generated by the engine 120 and the motor generator 140 to the drive wheels 160 and that transmits the drive of the drive wheels 160 to the engine 120 and the motor generator 140. Power distribution mechanism (for example, a planetary gear mechanism) 200 for distributing the generated power to two paths of drive wheel 160 and generator 140B, battery 220 for charging electric power for driving motor generator 140, and battery 220 Inverter 240 that performs current control while converting direct current and alternating current of motor 140A and generator 140B, and a battery control unit (hereinafter, referred to as a battery ECU (Electronic Control Unit)) 26 that manages and controls the charge / discharge state of battery 220. And an engine ECU 280 that controls the operating state of the engine 120, an MG_ECU 300 that controls the motor generator 140, the battery ECU 260, the inverter 240, and the like according to the state of the hybrid vehicle, and a mutual management control of the battery ECU 260, the engine ECU 280, the MG_ECU 300, and the like. And the HV_ECU 320 that controls the entire hybrid system so that the hybrid vehicle can operate most efficiently. In FIG. 1, each ECU is separately configured, but may be configured as an integrated ECU of two or more ECUs.
[0029]
Power split device 200 uses a planetary gear mechanism (planetary gear) to distribute the power of engine 120 to both drive wheels 160 and motor generator 140B. By controlling the rotation speed of motor generator 140B, power split device 200 also functions as a continuously variable transmission. As shown in the nomographic chart of FIG. 2, the rotational force of the engine 120 is input to the planetary carrier (C), which is supplied to the motor generator 140B by the sun gear (S), and the motor and the output shaft (drive) by the ring gear (R). (Wheel 160 side). When the rotation of the engine 120 is started, the friction torque acts in the negative direction because the engine 120 is stopped. Motor generator 140B generates a positive torque with respect to this negative friction torque, and engine 120 is started (cranked) by motor generator 140.
[0030]
In a hybrid vehicle equipped with the hybrid system as shown in FIG. 1, when the efficiency of the engine 120 is low, such as when starting or running at low speed, the hybrid vehicle is driven only by the motor 140A of the motor generator 140. During normal traveling, for example, the power of the engine 120 is divided into two paths by the power split device 200, and the drive wheels 160 are directly driven, and the generator 140B is driven to generate power. At this time, the generated electric power drives the motor 140A to assist the driving of the driving wheels 160. In addition, during high-speed running, the electric power from the battery 220 is further supplied to the motor 140A to increase the output of the motor 140A to add driving force to the driving wheels 160. On the other hand, at the time of deceleration, motor 140 </ b> A driven by drive wheel 160 functions as a generator to perform regenerative power generation, and stores the recovered power in battery 220. If the charge amount of battery 220 decreases and charging is particularly necessary, the output of engine 120 is increased to increase the amount of power generated by generator 140B, thereby increasing the charge amount for battery 220. Of course, control is performed to increase the drive amount of engine 120 as needed even during low-speed running. For example, as described above, the case where the battery 220 needs to be charged, the case where an auxiliary machine such as an air conditioner is driven, the case where the temperature of the cooling water of the engine 120 is raised to a predetermined temperature, and the like.
[0031]
A technical feature of the present embodiment is that the top dead center of the piston of engine 120 is determined using motor generator 140B immediately after engine 120 is started. In order to detect the operation state of the engine 120, for example, the piston top dead center sensor 340 for detecting the rotational position of a gear attached to the crankshaft of the engine 120 and substantially directly connected to the crankshaft of the engine 120 A rotation sensor (resolver) 360 (only generator 140B is shown in FIG. 1 but also present in motor 140A) provided in motor generator 140 is provided.
[0032]
A piston top dead center signal output from piston top dead center sensor 340 is input to engine ECU 280 and further to HV_ECU 320. A resolver angle signal output from resolver 360 of motor generator 140 is input to MG_ECU 300 and further to HV_ECU 320. HV_ECU 320 determines the piston top dead center at the time of engine start of engine 120 based on the value of the input signal.
[0033]
Immediately after the engine 120 is started, the fluctuation of the engine friction is greatest when the piston of the cylinder of the engine 120 passes through the top dead center, that is, where the transition from compression to expansion occurs. As shown in FIGS. 3 and 4, immediately before the top dead center (FIGS. 3A and 4A), the engine friction becomes a large negative value, but immediately after the top dead center (FIG. 3B 4) and FIG. 4B), the engine friction has a large positive value. This can be understood from the fact that the vector F shown in FIG. 4A is in the opposite direction to the rotation direction of the crankshaft, and the vector F ′ shown in FIG. 4B is in the same direction as the rotation direction of the crankshaft.
[0034]
The engine friction torque rapidly changes from a large negative value to a large positive value before and after the top dead center, and the angular acceleration of motor generator 140B also changes abruptly accordingly. In the present embodiment, this is detected to determine the top dead center.
[0035]
The equation of motion of the vehicle when the vehicle is stopped is
I ′ (dωg / dt) = − Te × {ρ / (1-ρ)} + Tg
Is represented by here,
I ′ = Ig + {ρ / (1 + ρ)} ² × Ie
It is. However,
ρ: planetary gear ratio
Ig: Moment of inertia of motor generator 140B
Ie: Moment of inertia of engine 120
ωg: angular velocity of motor generator 140B
Te: friction torque of engine 120
Tg: cranking torque of motor generator 140B
If cranking torque Tg of motor generator 140B is constant, variation in friction torque Te of engine 120 appears in angular acceleration (dωg / dt) of motor generator 140B. This means that, as described above, the engine friction torque rapidly changes from a large negative value to a large positive value before and after the top dead center, and the angular acceleration of the motor generator 140B also changes abruptly accordingly. It is shown that determining the inflection point of the angular acceleration determines the piston top dead center.
[0036]
Referring to FIG. 5, the control structure of the piston top dead center determination process executed by HV_ECU 320 will be described. In FIG. 5, motor generator 140B is described as MG (1).
[0037]
In step (hereinafter, step is abbreviated as S) 100, HV_ECU 320 determines whether or not start control of engine 120 is being performed. This determination is made based on various signals input to HV_ECU 320. If start control of engine 120 is being performed (YES in S100), the process proceeds to S110. If not (NO in S100), this process ends.
[0038]
At S110, displacement angle θ of motor generator 140B is detected. In this process, displacement angle θ of motor generator 140B is detected based on a resolver angle signal input from resolver 360 to HV_ECU 320 via MG_ECU 300. At S120, HV_ECU 320 calculates angular velocity ω of motor generator 140B. In this process, the angular velocity ω of motor generator 140B is calculated by subtracting displacement angle θ one sampling time earlier from displacement angle θ detected in S110, and dividing the subtracted value by the sampling time. In S130, displacement angle θ of motor generator 140B detected in S110 is overwritten with displacement angle θ one sampling time before, and stored.
[0039]
At S140, HV_ECU 320 calculates the angular acceleration (dωg / dt) of motor generator 140B. In this process, the angular velocity (dωg / dt) of motor generator 140B is calculated by subtracting the angular velocity ω one sampling time earlier from the angular velocity ω calculated in S120 and dividing the subtracted value by the sampling time. Is done. In S150, the angular velocity ω of motor generator 140B calculated in S120 is overwritten and stored over the angular velocity ω one sampling time earlier.
[0040]
In S160, HV_ECU 320 calculates the amount of change in angular acceleration (dωg / dt) of motor generator 140B. In this process, the angular acceleration (dωg / dt) of the motor generator 140B is changed by subtracting the angular acceleration (dωg / dt) one sampling time earlier from the angular acceleration (dωg / dt) calculated in S140. Is calculated. At S170, the angular acceleration (dωg / dt) of motor generator 140B calculated at S140 is overwritten and stored over the angular acceleration (dωg / dt) one sampling time earlier.
[0041]
In S180, HV_ECU 320 determines whether the amount of change in angular acceleration (dωg / dt) calculated in S160 is larger than threshold value A and whether angular velocity ω calculated in S120 is smaller than threshold value B. Judge. The threshold value A is a positive value, and the threshold value B is a negative value. If the amount of change in angular acceleration (dωg / dt) is larger than threshold value A and angular velocity ω is smaller than threshold value B (YES in S180), the process proceeds to S190. If not (NO in S180), this process ends. In S190, HV_ECU 320 performs a top dead center determination. Specifically, a top dead center determination flag in a reset state is set.
[0042]
The operation of HV_ECU 320 according to the present embodiment based on the above structure and flowchart will be described.
[0043]
When the driver of the hybrid vehicle sets the ignition key to the engine start position and instructs to start the engine (YES in S100), displacement angle θ of resolver 360 provided in motor generator 140B provided to HV_ECU 320 via MG_ECU 300 is input. Is detected (S110). The difference between the displacement angle θ and the displacement angle θ one sampling time earlier is divided by the sampling time to calculate the angular velocity ω of the motor generator 140B (S120). The angular acceleration (dωg / dt) of motor generator 140B is calculated by dividing the difference between this angular velocity ω and the angular velocity ω one sampling time earlier by the sampling time (S140). By calculating the difference between the angular acceleration (dωg / dt) and the angular acceleration (dωg / dt) one sampling time before, the amount of change in the angular acceleration (dωg / dt) of the motor generator 140B is calculated (S160).
[0044]
If the amount of change in angular acceleration (dωg / dt) is larger than threshold value A and angular velocity ω is smaller than threshold value B (YES in S180), the reset state top dead center determination flag is set. . If the change amount of the angular acceleration (dωg / dt) is equal to or smaller than the threshold value A or the angular velocity ω is equal to or larger than the threshold value B (NO in S180), the state of the reset state of the top dead center determination flag remains unchanged. Will be maintained.
[0045]
FIG. 6 is a timing chart showing this operation. 6 (A) is a command torque value to motor generator 140B, FIG. 6 (B) is rotation speed of motor generator 140B, FIG. 6 (C) is angular acceleration (dωg / dt) of motor generator 140B, FIG. 6 (D). Is a top dead center detected by a piston top dead center sensor 340 provided in the engine 120, and FIG. 6E is a timing chart showing an actual top dead center. Since the engine 120 is a four-cylinder engine, the timing charts of FIGS. 6D and 6E also show the top dead center for the four cylinders.
[0046]
The inflection point (minimum point) of the angular acceleration (dωg / dt) in the timing chart of FIG. As shown in FIG. 6E, the top dead center can be detected from the second and subsequent top dead centers. That is, it can be detected from the second top dead center excluding the first top dead center immediately after the start of cranking. The first top dead center is that the position of the piston at which the piston stopped varies depending on the stop state, and when cranking from the state where the piston stopped during the compression process, the engine friction due to compression This is because the inflection point of the angular acceleration (dωg / dt) in the timing chart of FIG. 6C does not appear because the torque does not become a large negative value.
[0047]
For comparison, FIG. 6D shows a detection result of the top dead center by the piston top dead center sensor 340 provided in the engine 120. As shown in FIG. 6D, three top dead points immediately after cranking have not been detected. This is because the cranking speed is low.
[0048]
Further, based on the top dead center of the piston detected based on the inflection point of the angular acceleration (dωg / dt), an abnormality of the piston top dead center sensor 340 is detected, and the crank angle is determined based on the top dead center determination. The angle can be estimated, and the cranking torque can be adjusted based on the estimated crank angle to suppress vibration at the time of starting the engine.
[0049]
As described above, according to the HV_ECU of the hybrid vehicle according to the present embodiment, the resolver is provided in the motor generator for cranking the engine, the angular velocity which is the temporal change of the displacement angle is calculated, and the angular velocity is further changed. Is calculated. An inflection point of the rotational angular acceleration is obtained, and this inflection point is determined as a top dead center. At the inflection point (minimum point) of the rotational angular acceleration, it is determined that the direction of the force applied to the piston changes from negative (compression) to positive (expansion) at compression top dead center. Points can be accurately detected.
[0050]
The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[Brief description of the drawings]
FIG. 1 is a control block diagram of a hybrid vehicle according to an embodiment of the present invention.
FIG. 2 is an alignment chart of a power split device.
FIG. 3 is a diagram illustrating a relationship between a crank angle and an engine friction torque.
FIG. 4 is a diagram showing engine friction torque near the top dead center of the piston of the engine.
FIG. 5 is a flowchart illustrating a control structure of a top dead center determination process executed by the HV_ECU.
FIG. 6 is a timing chart of a top dead center determination process.
[Explanation of symbols]
120 engine, 140 motor generator, 140A motor, 140B generator, 160 drive wheels, 180 reduction gear, 200 power split mechanism, 220 battery, 240 inverter, 260 battery ECU, 280 engine ECU, 300 MG_ECU, 320 HV_ECU, 340 piston dead Point sensor, 360 resolver.

Claims (8)

An engine start control device for determining a piston top dead center when starting an engine with a motor,
Detecting means for detecting the rotational angular velocity of the crankshaft during cranking,
An engine start control device including: a determination unit configured to determine the top dead center based on the detection result of the rotational angular velocity. 2. The engine start control device according to claim 1, wherein said detection means includes means for detecting a rotational angular velocity of the motor during cranking. 3. The engine start control device according to claim 2, wherein the detection unit includes a unit for detecting the rotational angular velocity based on a signal output from a rotary resolver provided in the motor. The determination means includes a means for detecting an inflection point of the rotational angular acceleration from the rotational angular velocity and determining the top dead center based on the inflection point. Engine start control device. An engine start control method for determining a piston top dead center when starting an engine with a motor,
A detecting step of detecting a rotational angular velocity of the crankshaft during cranking;
A determining step of determining the top dead center based on the detection result of the rotational angular velocity. The engine start control method according to claim 5, wherein the detecting step includes a step of detecting a rotational angular velocity of the motor during cranking. The engine start control method according to claim 6, wherein the detecting step includes a step of detecting the rotational angular velocity based on a signal output from a rotary resolver provided in the motor. The engine according to any one of claims 5 to 7, wherein the determining step includes a step of detecting an inflection point of the rotational angular acceleration from the rotational angular velocity and determining the top dead center based on the inflection point. Start control method.

Images