JP7413910B2 - Internal combustion engine starting torque estimation method and internal combustion engine starting torque estimation device - Google Patents

Description

The present invention relates to an internal combustion engine starting torque estimating method and an internal combustion engine starting torque estimating device.

For example, Patent Document 1 includes an internal combustion engine capable of transmitting power to an input shaft, and a first motor generator and a second motor generator each capable of transmitting power to the input shaft independently of the internal combustion engine. , a technique is disclosed for estimating the output torque of an internal combustion engine based on a first resolver angle of a first motor-generator, a second resolver angle of a second motor-generator, and a rotational state of the internal combustion engine.

Japanese Patent Application Publication No. 2010-167861

However, Patent Document 1 estimates the output torque of an internal combustion engine on the premise of a system equipped with an internal combustion engine and two motor generators, and the applicable systems are limited and lacks versatility.

That is, there is room for further improvement in estimating the starting torque of an internal combustion engine.

The internal combustion engine according to the present invention has damper characteristics of a damper that connects a rotating shaft of an electric motor and a crankshaft of an internal combustion engine, a detection signal of a resolver attached to the rotating shaft of the electric motor, and a detection signal of a resolver attached to the rotating shaft of the electric motor. The present invention is characterized in that the starting torque of the internal combustion engine is estimated by using a detection signal of a crank angle sensor and by utilizing a rotational phase difference between the crankshaft and the rotating shaft of the electric motor.

According to the present invention, it is possible to estimate the starting torque of an internal combustion engine with high accuracy by using the angular phase difference between the crankshaft and the motor rotating shaft.

1 is an explanatory diagram schematically showing a schematic configuration of a power train of a hybrid vehicle to which the present invention is applied. FIG. 3 is an explanatory diagram schematically showing the correlation between rotation angles of a crankshaft and an electric motor rotating shaft, and torque. FIG. 3 is an explanatory diagram schematically showing the relationship between outside air temperature and variations in calculated values of torque generated in an electric motor. FIG. 3 is an explanatory diagram showing the damper spring characteristics, which shows the relationship between the angle at which the rotary shaft of the damper is twisted by the electric motor or the internal combustion engine and the torque, which can be understood from the spring characteristics. FIG. 3 is an explanatory diagram schematically showing the correlation between battery output and battery SOC. An explanatory diagram showing the correlation between starting torque and outside temperature. 1 is a flowchart showing an example of a control flow of an internal combustion engine.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is an explanatory diagram schematically showing a schematic configuration of a power train of a hybrid vehicle to which the present invention is applied.

An internal combustion engine (engine) 1 is connected to an electric motor 3 via a damper 2. The internal combustion engine 1 is, for example, a power generation internal combustion engine that drives an electric motor 3 as a generator. In other words, the internal combustion engine 1 is such that the torque generated by the internal combustion engine 1 is not transmitted to drive wheels (not shown).

A crank angle sensor 5 that detects the crank angle of the crankshaft 4 is attached to the rear end of the crankshaft 4 of the internal combustion engine 1 .

A rotation shaft (motor rotation shaft) 6 of the electric motor 3 is connected to the damper 2 at a front end. A resolver 7 that detects the rotation angle of the motor rotation shaft 6 is attached to the rear end of the motor rotation shaft 6 .

Detection signals from the crank angle sensor 5 and resolver 7 are input to a control unit 8.

The control unit 8 is a well-known digital computer equipped with a CPU, ROM, RAM, and input/output interface, and controls the internal combustion engine 1 and the electric motor 3 based on detection signals from various sensors.

The electric power generated by the electric motor 3 is charged into a battery 9, for example. The electric motor 3 can also be driven by receiving power from the battery 9. The battery 9 supplies electric power to a drive motor (not shown) that drives drive wheels of the hybrid vehicle. The battery SOC, which is the ratio of the remaining charge to the charge capacity of the battery 9, can be detected by the control unit 8.

The control unit 8 is capable of calculating the rotation speed of the crankshaft 4 (engine rotation speed) based on the detection signal of the crank angle sensor 5. Furthermore, the control unit 8 is capable of calculating the rotation speed of the motor rotating shaft 6 (motor rotation speed) based on the detection signal of the resolver 7 .

The control unit 8 uses the crank angle sensor 5 and the resolver 7 to calculate the starting torque necessary to start (start) the stopped internal combustion engine 1 based on the angular phase difference between the crankshaft 4 and the motor rotating shaft 6. presume. In other words, the control unit 8 is a starting torque estimation section. Further, a detection signal from an outside air temperature sensor 10 that detects outside air temperature is input to the control unit 8.

FIG. 2 is an explanatory diagram schematically showing the correlation between the rotation angles of the crankshaft 4 and the motor rotating shaft 6, and the torque.

When applying torque (rotation) from the electric motor 3 to the crankshaft 4, the torque (rotation) is transmitted after the electric motor 3 has rotated to some extent depending on the damper characteristics of the damper 2. That is, when torque (rotation) is applied to the crankshaft 4 from the electric motor 3, the torque (rotation) is not transmitted until the torsion angle of the damper 2 is twisted by a predetermined angle according to the damper characteristics.
The starting torque of the internal combustion engine 1 is the torque when the crankshaft 4 starts to rotate, and can be estimated with high accuracy using the angular phase difference between the crankshaft 4 and the electric motor rotating shaft 6.

FIG. 3 is an explanatory diagram schematically showing the relationship between the outside temperature and the variation in the calculated value of the torque generated in the electric motor 3. As shown in FIG.

As shown in Fig. 3, the calculated value of the torque generated in the electric motor 3 is highly accurate in a predetermined normal temperature range (for example, 20°C ± 5°C), which is the outside temperature at the time of assembly, but the mechanical Accuracy decreases (variation increases) at low or high temperatures due to the influence of mechanical clearance, magnetic, and electrical characteristics.
That is, in the electric motor 3, the accuracy of the torque calculation value becomes high (variation becomes small) in a normal temperature range that is approximately equivalent to the assembled state in which there is no change in clearance due to temperature or change in the performance of the magnet or the electric motor 3.

Therefore, the spring constant in the damper characteristics of the damper 2 is learned from the relationship between the torque generated in the electric motor 3 and the torsion angle of the damper 2 when the temperature around the internal combustion engine 1 is in a predetermined normal temperature range. The learned spring constant of the damper 2 is stored in, for example, the RAM of the control unit 8.
As a result, the spring constant of the damper characteristics of the damper can be learned from the relationship between the torque of the electric motor 3 and the torsion angle of the damper 2 while the torque of the electric motor 3 is high, and the starting torque of the internal combustion engine 1 can be determined with high accuracy. It becomes possible to estimate.
In addition, by learning the relationship between the calculated value of the torque of the electric motor 3 and the spring constant of the damper characteristics of the damper 2 in a predetermined room temperature range, the torque of the electric motor 3 and the spring constant of the damper characteristics of the damper 2 can be constantly adjusted. It becomes possible to understand the relationship, and even if the components of the system deteriorate over time, the starting torque of the internal combustion engine 1 can be estimated with high accuracy.

The damper performance of the damper 2 can be numerically modeled using the spring constant and frictional resistance of the damper 2.

When the internal combustion engine 1 is stopped, the spring constant of the damper 2 is detected and learned by causing the electric motor 3 to generate torque of different values multiple times (for example, twice) below the friction of the internal combustion engine 1. can do.

When the electric motor 3 generates a torque that is less than the friction of the internal combustion engine 1 and the internal combustion engine 1 is stopped, the rotation angle of the electric motor rotating shaft 6 becomes a rotation angle according to the spring constant of the damper 2.

Therefore, as shown in FIG. 4, the spring constant of the damper 2 is detected by linear approximation from the relationship between the torque generated in the electric motor 3 and the rotation angle of the motor rotating shaft 6 when the electric motor 3 generates the torque. can do.

FIG. 4 is an explanatory diagram showing the damper spring characteristics showing the relationship between the angle at which the rotary shaft of the damper 2 is twisted by the electric motor 3 or the internal combustion engine 1 and the torque that can be understood from the spring characteristics. The rotation angle of the motor rotation shaft 6 can be detected using a detection signal from the resolver 7.

Points A and B in FIG. 4 indicate the torque generated in the electric motor 3 and the rotation angle of the electric motor rotating shaft 6 at that time. A characteristic line S in FIG. 4 is a straight line passing through points A and B, and its slope represents the spring constant of the damper 2.

If the internal combustion engine 1 is in operation, the detection signal of the resolver 7 and the detection signal of the crank angle sensor 5 will be The spring constant of the damper 2 can be detected and learned by using the phase difference and the drive torque generated in the electric motor 3 (the amount of change in the drive torque of the electric motor 3 during a transient period).

As for the frictional resistance of the damper 2, for example, a value obtained in advance through experiments or the like may be stored in the ROM of the control unit 8 and used.

Further, the accuracy of the calculated value of the torque of the electric motor 3 decreases (dispersion increases) when the environmental temperature (outside temperature) changes from the normal temperature range.

Therefore, the torque of the electric motor 3 is corrected using the spring constant in the damper characteristics of the damper 2. That is, the starting torque of the internal combustion engine 1 is calculated based on the spring constant in the damper characteristics of the damper 2.

As a result, it is possible to improve the torque accuracy of the electric motor 3, and it is possible to prevent the electric motor 3 from generating more torque than necessary when starting the internal combustion engine 1 (startup), thereby reducing power consumption. can.

The spring constant in the damper characteristics of the damper 2 may be corrected depending on the temperature. This makes it possible to estimate the starting torque of the internal combustion engine 1 with higher accuracy.

Furthermore, if the starting torque of the internal combustion engine 1 can be estimated with high accuracy, the electric power required for the electric motor 3 to generate this starting torque can be known. That is, when starting the internal combustion engine 1, the battery SOC required of the battery 9 capable of supplying electric power to the electric motor 3 can be estimated with high accuracy.
FIG. 5 is an explanatory diagram schematically showing the correlation between the output power of the battery 9 and the battery SOC.

The output of the battery 9 decreases as the battery SOC decreases, and even if the battery SOC remains the same, the output decreases as the temperature decreases.

Auxiliary lines S1 and S2 shown as broken lines in FIG. 5 schematically show the range of variation in the starting torque of the internal combustion engine 1.

For example, the lower limit value of the battery SOC is set so that the internal combustion engine 1 can be started even if the starting torque of the internal combustion engine 1 is at the lower limit of variation, taking into account the startability of the internal combustion engine 1 in an extremely low temperature environment (for example, -30°C). (see auxiliary line S1).
However, the lower limit value of the battery SOC can be set without considering variations in the starting torque of the internal combustion engine 1 if the starting torque of the internal combustion engine 1 can be estimated with high accuracy.
For example, if the starting torque of the internal combustion engine 1 is at the median of the variation range, the startability of the internal combustion engine 1 can be ensured even if the lower limit of the battery SOC of the battery 9 is set lower by that amount (see the auxiliary line S2). reference).
In other words, as shown in FIG. 5, if the starting torque of the internal combustion engine 1 can be estimated with high accuracy, the range of use of the battery 9 can be expanded while ensuring the startability of the internal combustion engine 1 in an extremely low temperature environment. Can be done.

The value of the starting torque of the internal combustion engine 1 at extremely low temperatures needs to be predicted in advance by storing the relationship between the outside air temperature and the starting torque of the internal combustion engine 1.

Therefore, the control unit 8 compares the starting torque of the internal combustion engine 1 with a reference characteristic line representing the correlation between the outside air temperature and the lower limit value of the starting torque of the internal combustion engine 1, and stores the relationship between the two. Prepare to be able to predict the starting torque of an internal combustion engine 1 at extremely low temperatures.
Specifically, the control unit 8 calculates the starting torque of the internal combustion engine 1 estimated using the rotational phase difference between the crankshaft 4 and the rotating shaft of the electric motor 3 and the starting torque of the internal combustion engine 1 found from the reference characteristic line. The comparison is made, and the smaller one is stored as the starting torque of the internal combustion engine 1 at the temperature at that time.
Furthermore, the control unit 8 stores the difference between the actual starting torque of the internal combustion engine 1 and the reference characteristic line for each outside temperature, and sets the starting torque of the internal combustion engine 1 at extremely low temperatures to the reference characteristic line. Predict how much it will deviate from the characteristic line. Then, the lower limit battery SOC of the battery 9 is set based on the predicted starting torque of the internal combustion engine 1 at extremely low temperatures.
Note that the reference characteristic line is set by accumulating, for example, the maximum values of various expected variations, and is stored in advance in the ROM of the control unit 8 or the like.

FIG. 6 is an explanatory diagram showing the correlation between starting torque and outside temperature. The solid line in FIG. 6 indicates the reference characteristic line mentioned above. The broken line in FIG. 6 is a starting torque characteristic line estimated from the starting torque of the internal combustion engine 1 estimated using the rotational phase difference between the crankshaft 4 and the rotating shaft of the electric motor 3. ● in FIG. 6 is a plot of the starting torque of the internal combustion engine 1 estimated using the rotational phase difference between the crankshaft 4 and the rotating shaft of the electric motor 3. 6 is the predicted starting torque at low temperatures estimated from the starting torque of the internal combustion engine 1 estimated using the rotational phase difference between the crankshaft 4 and the rotating shaft of the electric motor 3.

If the starting torque of the internal combustion engine 1 can be estimated with high accuracy, the battery 9 that supplies electric power to the electric motor 3 will eliminate the need to take into account the variation margin of starting torque, and the range of usable battery SOC (usable range of the battery 9) will be reduced. can be expanded. If the starting torque of the internal combustion engine 1 estimated using the rotational phase difference between the crankshaft 4 and the motor rotating shaft 6 is smaller than the starting torque determined from the reference characteristic line, the startability of the internal combustion engine 1 is ensured. , it becomes possible to expand the lower limit value of the battery SOC, and it is possible to expand the EV driving scene (extend the EV driving time).

Therefore, in a hybrid vehicle equipped with the internal combustion engine 1, as the usable range of the battery 9 expands, it becomes possible to increase the travel distance (cruising distance) by EV driving and to downsize the battery 9, thereby reducing costs. and weight can be reduced.

Furthermore, since the starting torque of the internal combustion engine 1 can be estimated with high accuracy, the amount of fuel injection and the amount of intake air at the time of starting (starting) can be optimized, and the exhaust performance is improved (the exhaust becomes cleaner). Further, in the internal combustion engine 1, by improving the exhaust performance, it is possible to reduce the cost of a catalyst provided in the exhaust passage for exhaust purification.
Furthermore, by examining the change over time in the starting torque of the internal combustion engine 1 at the same outside temperature, it is possible to estimate the degree of deterioration of the lubricating oil. Further, if the starting torque of the internal combustion engine 1 changes rapidly over time at the same outside temperature, it can be assumed that some kind of failure or malfunction has occurred.
In addition, if the reference characteristic line is set by accumulating the maximum values of various expected variations, the internal combustion engine 1 estimated by utilizing the rotational phase difference between the crankshaft 4 and the rotating shaft of the electric motor 3 If the starting torque is larger than the starting torque determined from the reference characteristic line, it can be determined that there is some kind of failure.

FIG. 7 is a flowchart showing an example of the flow of control of the internal combustion engine 1 described above.
In step S1, it is determined whether or not to start the internal combustion engine 1. If the predetermined starting conditions are satisfied and the internal combustion engine 1 is to be started, the process proceeds to step S2.

In step S2, the spring constant of the damper 2 is read. In step S3, the spring constant of the damper 2 is corrected according to the outside temperature. In step S4, the starting torque of the internal combustion engine 1 is estimated. In step S5, starting conditions for the internal combustion engine 1 are set based on the estimated starting torque for the internal combustion engine 1. The starting conditions for the internal combustion engine 1 include the torque of the electric motor 3, the intake air amount of the internal combustion engine 1, and the like.

In step S6, it is determined whether the internal combustion engine 1 has been started under the starting conditions of step S5. If the internal combustion engine 1 has started, the process advances to step S7 and the internal combustion engine 1 is operated normally. If the internal combustion engine 1 does not operate, the process advances to step S8.

In step S8, it is determined whether the number of times the internal combustion engine cannot be started has exceeded a predetermined value (a predetermined number of times, for example, three times). If the number of times the internal combustion engine cannot be started exceeds a predetermined value, the process advances to step S9. If the number of internal combustion start failures does not exceed the predetermined value, the process advances to step S10.

In step S9, it is determined that the internal combustion engine 1 cannot be started (failure detected). If a failure is detected, a warning light may be turned on to notify the driver.

In step S10, the number of times the internal combustion engine cannot be started is counted, and the previous value of the starting torque of the internal combustion engine 1 plus a predetermined value (predetermined torque correction amount) is set as a new starting torque, and step S5 Return to

1...Internal combustion engine 2...Damper 3...Electric motor 4...Crankshaft 5...Crank angle sensor 6...Electric motor rotation shaft 7...Resolver 8...Control unit

Claims (6)

damper characteristics of a damper that connects the front end of the rotating shaft of the electric motor and the rear end of the crankshaft of the internal combustion engine;
A detection signal of a resolver attached to the rotating shaft of the electric motor,
Using the detection signal of the crank angle sensor attached to the crankshaft,
When applying rotation to the crankshaft from the electric motor, the rotation phase difference between the rotation shaft of the electric motor starts to rotate and the crankshaft starts to rotate is generated depending on the damper characteristics. When the crankshaft is stopped and is rotated by the electric motor, the starting torque of the internal combustion engine, which is the torque when the crankshaft starts rotating, is determined by the rotational phase difference between the crankshaft and the rotating shaft of the electric motor. Estimate using
An internal combustion engine characterized in that a spring constant in a damper characteristic of the damper is learned from the relationship between the torque generated in the electric motor and the torsion angle of the damper when the temperature around the internal combustion engine is in a predetermined normal temperature range. starting torque estimation method. 2. The method for estimating starting torque of an internal combustion engine according to claim 1, wherein the starting torque of the internal combustion engine is calculated based on a spring constant in a damper characteristic of the damper. 3. The method for estimating starting torque of an internal combustion engine according to claim 1 , wherein a spring constant in the damper characteristic of the damper is corrected according to temperature. It has a reference characteristic line that expresses the correlation between the outside temperature and the starting torque of the internal combustion engine,
The starting torque of the internal combustion engine estimated by utilizing the rotational phase difference between the crankshaft and the rotating shaft of the electric motor is compared with the starting torque of the internal combustion engine determined from the above reference characteristic line, and the smaller one is selected based on the temperature at that time. The method for estimating starting torque of an internal combustion engine according to any one of claims 1 to 3 , wherein the starting torque is the starting torque of the internal combustion engine. 5. The method for estimating starting torque of an internal combustion engine according to claim 4 , wherein the reference characteristic line is a characteristic line representing a lower limit value of starting torque of the internal combustion engine with respect to outside temperature. an electric motor connected to a crankshaft of an internal combustion engine via a damper;
a resolver attached to the electric motor;
a crank angle sensor attached to the crankshaft;
a starting torque estimation unit that estimates the starting torque of the internal combustion engine by utilizing a rotational phase difference between the crankshaft and the rotating shaft of the electric motor ;
The starting torque estimating unit is configured to calculate a rotational phase difference between when a rotating shaft of the electric motor starts to rotate and when the crankshaft starts to rotate when applying rotation from the electric motor to the crankshaft according to a damper characteristic of the damper. When the crankshaft, which has stopped rotating, is rotated by the electric motor, the starting torque of the internal combustion engine, which is the torque when the crankshaft starts rotating, is estimated, and the internal combustion engine Starting an internal combustion engine, characterized in that a spring constant in a damper characteristic of the damper is learned from the relationship between the torque generated in the electric motor and the torsion angle of the damper when the surrounding temperature is in a predetermined normal temperature range. Torque estimation device.

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