JP2004058689A - Controlling device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make emission gas good and miniaturize another power source by enabling low temperature combustion of an internal combustion engine of a hybrid vehicle as much as possible. <P>SOLUTION: This controlling device for a hybrid vehicle provided with a speed controlling mechanism changing speed of an internal combustion engine is provided with a low temperature determination means (step S1) determining existence of low temperature combustion request, an output determination means (Step S2, S5) determining if output of the internal combustion engine is in a low temperature combustion zone when low temperature combustion is requested, am output changing means (Step S9, S11, S12) driving another power source and changing output of the internal combustion engine for entering into the low temperature combustion zone when it is determined that output of the internal combustion engine is not in the low temperature combustion zone, and a speed controlling means (Step S7, S10) changing speed of the internal combustion engine to make an operation point of the internal combustion engine at changed output within the low temperature combustion zone. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a hybrid vehicle having an internal combustion engine and another power source, and more particularly to a device for controlling the output of an internal combustion engine.
[0002]
[Prior art]
Conventionally, a hybrid vehicle using an internal combustion engine and a motor or a motor / generator as power sources has been known. This type of vehicle is a vehicle developed mainly for the purpose of reducing exhaust gas and improving fuel efficiency by the internal combustion engine, and operates the internal combustion engine as efficiently as possible to reduce the surplus of the internal combustion engine. While the power of the internal combustion engine is stored as electric energy while the energy regenerated during braking and the like is stored as electric energy, when the power of the internal combustion engine is insufficient, the motor is driven by the stored electric energy to compensate for the lack of driving torque. In addition, at the time of starting, the motor is driven in place of the internal combustion engine to avoid inefficient operation of the internal combustion engine. Therefore, conventional hybrid vehicles basically compensate for the lack of output of the internal combustion engine with the output of another power source such as a motor, and use another power source such as a motor as an alternative to the internal combustion engine depending on the situation. It is configured to use the internal combustion engine as efficiently as possible.
[0003]
On the other hand, in order to reduce soot and NOx emitted from the internal combustion engine, a low-temperature combustion operation of the internal combustion engine has been conventionally performed. This is a control in which, when the load of the internal combustion engine is relatively low, the internal combustion engine is operated by, for example, increasing the amount of exhaust gas recirculation to lower the combustion temperature of the internal combustion engine. When this low-temperature combustion is performed, the amount of intake air is reduced, so that the output of the internal combustion engine is reduced and the driving torque may be insufficient.
[0004]
Therefore, for example, in the invention described in Japanese Patent Application Laid-Open No. 2000-110601, the speed of the internal combustion engine is increased by controlling the transmission connected to the internal combustion engine to a lower speed gear ratio. By lowering the output torque of the internal combustion engine while maintaining the above-mentioned conditions, low-temperature combustion is enabled. By controlling the gear ratio or the output of the internal combustion engine in this manner, the shortage of driving torque and the restriction of low-temperature combustion associated therewith are eliminated or alleviated, so that the operating range in which low-temperature combustion can be performed is expanded, and soot and NOx are reduced. Can be further suppressed.
[0005]
[Problems to be solved by the invention]
As described above, the low-temperature combustion operation is, for example, an operation state of the internal combustion engine in which the combustion temperature is reduced by increasing the exhaust gas recirculation amount, so that the amount of NOx generated in the internal combustion engine itself can be reduced. On the other hand, conventional vehicles are equipped with an exhaust gas purifying catalyst capable of removing pollutants such as NOx, so that NOx generated in the internal combustion engine is not directly discharged into the atmosphere, but depends on the operating state of the internal combustion engine. Therefore, even if a certain amount of NOx is generated, the NOx emission of the vehicle as a whole does not increase. Therefore, when a catalyst having a gradually increasing NOx storage amount, such as a storage reduction catalyst, is used, after the NOx storage amount reaches a predetermined amount, the NOx storage amount in the catalyst is reduced. Until the temperature is reduced, it is necessary to suppress the amount of NOx generated in the internal combustion engine itself, and the operation of the internal combustion engine in low-temperature combustion is effective in such a case.
[0006]
However, the operating range of the internal combustion engine capable of performing low-temperature combustion is limited to a relatively low torque range. Therefore, as described in the above-mentioned publication, it is possible to maintain the output of the internal combustion engine by increasing the rotation speed of the internal combustion engine during low-temperature combustion because the operating point at the high rotation speed and low torque on the iso-output line at that time. Is in the low temperature combustible region. In other words, because the required output at that time is large, even if the torque is reduced by increasing the rotational speed of the internal combustion engine on the equal output line, if the resulting operating point does not enter the low temperature combustion region, Cannot operate with low-temperature combustion.
[0007]
Conventionally, in a hybrid vehicle, another power source such as a motor is operated to assist the output of the internal combustion engine, and the output of the internal combustion engine is actively reduced while the vehicle is running at the output of the internal combustion engine. It is not configured to use another power source, such as a motor, to drive the motor. Furthermore, no preferable control mode has been known in relation to the internal combustion engine that performs the above-described low-temperature combustion, and new technology has to be developed in this regard.
[0008]
The present invention has been made in view of the above technical problem, and by controlling other power sources mounted in conjunction with an internal combustion engine so as to enable low-temperature combustion as much as possible. It is another object of the present invention to provide a control device capable of preventing deterioration of exhaust gas.
[0009]
Means for Solving the Problems and Their Functions
According to the present invention, in order to achieve the above object, when there is a request for low temperature combustion of an internal combustion engine, an output of another power source is increased so that an output of the internal combustion engine enters a predetermined low temperature combustion region. The output of the internal combustion engine is reduced so that the operating point of the internal combustion engine is controlled so that the operating point of the internal combustion engine becomes the operating point in the low-temperature combustion region without changing the output. It is characterized by having done. More specifically, the invention of claim 1 provides an internal combustion engine capable of low-temperature combustion that inhales more inert gas than an inert gas intake amount at which the amount of generated soot is maximum, another power source, A control device for a hybrid vehicle having a rotation speed control mechanism coupled to an output side of the internal combustion engine and for changing the rotation speed of the internal combustion engine, wherein a low-temperature combustion determining means for determining whether the low-temperature combustion is required; Output determination means for determining whether the output of the internal combustion engine is in the low-temperature combustion region when the request is issued, and when it is determined that the output of the internal combustion engine is not in the low-temperature combustion region Output changing means for driving the other power source and changing the output of the internal combustion engine so as to enter the low-temperature combustion area, and the operating point of the internal combustion engine at the changed output falls within the low-temperature combustion area. It will be the driving point A control apparatus characterized by and a rotational speed control means for changing the rotational speed of the internal combustion engine by the speed control mechanism.
[0010]
Further, the output changing means according to claim 1 drives the other power source such that the output of the internal combustion engine is a maximum output or an output close to the maximum output in an output entering the low temperature combustion region. The output of the internal combustion engine may be changed.
[0011]
Therefore, in the invention of claim 1 or the invention of claim 2, when there is a request to cause the internal combustion engine mounted together with another power source to perform low-temperature combustion, the output of the internal combustion engine at that time is set to a predetermined low temperature. If not, the other power source is driven and the output of the internal combustion engine is changed to enter the low temperature combustion region. That is, the driving of the other power source is performed to allow a decrease in the output of the internal combustion engine, or the other driving source is operated due to putting the output of the internal combustion engine into the low-temperature combustion region. Then, while maintaining the changed output, the rotation speed of the internal combustion engine is changed, and the operating point is set to an operating point in the low-temperature combustion region. As a result, the amount of NOx and soot generated in the internal combustion engine is reduced, and deterioration of exhaust gas of the vehicle as a whole is prevented.
[0012]
In particular, in the second aspect of the invention, the changed output of the internal combustion engine is set to the maximum output that enters the low-temperature combustion region or an output close thereto. As a result, the output of another power source required to maintain the output of the entire vehicle before and after changing the output of the internal combustion engine is reduced.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described based on specific examples. First, a hybrid vehicle according to the present invention will be described. FIG. 3 includes an internal combustion engine (E / G) 1 and a motor (M) 2 as power sources, and a generator ( G) shows a hybrid vehicle equipped with 3; The internal combustion engine 1 is a power unit that outputs power by burning fuel such as a gasoline engine or a diesel engine. An exhaust gas purification catalyst (not shown) such as an occlusion reduction type three-way catalyst is provided in an exhaust system. The internal combustion engine 1 is configured to perform low-temperature combustion. This low-temperature combustion is a combustion mode in which the combustion temperature is reduced by supplying an inert gas to the fuel by an exhaust gas recirculation device (EGR) or the like. This is a combustion mode in which an inert gas is supplied (or sucked) in an amount larger than the amount of the active gas. As a result, the generation of soot is suppressed, and at the same time, the generation amount of NOx is reduced due to the low combustion temperature.
[0014]
A clutch 4 having a damper is connected to an output side of the internal combustion engine 1, and a combining mechanism that combines engine torque output by engaging the clutch 4 with torque of the motor 2 and the generator 3. 5 are provided. In the example shown in FIG. 3, the synthesizing mechanism 5 is mainly configured by a single pinion type planetary gear mechanism, and the sun gear 6 is connected to the rotor of the generator 3. The rotor of the motor 2 is connected to a ring gear 7 which is an internal gear arranged concentrically with the sun gear 6. The clutch 4 is connected to a carrier 8 holding a pinion gear disposed between the sun gear 6 and the ring gear 7. Further, the ring gear 7 is connected to a drive sprocket 9 which is an output member.
[0015]
A chain 10 wound around the drive sprocket 9 is wound around a driven sprocket 12 attached to an intermediate shaft 11, and torque is output from the ring gear 7 to the intermediate shaft 11. A final shaft 13 is arranged parallel to the intermediate shaft 11, and the intermediate shaft 11 and the final shaft 13 are connected by a counter gear pair 14. Further, the final shaft 13 and the differential gear 15 are connected by a final gear pair 16 so as to output the torque transmitted to the differential gear 15 to the left and right drive shafts 17.
[0016]
It is configured such that parameters such as the output of the internal combustion engine 1 such as the intake air amount, the fuel supply amount (fuel injection amount), and the exhaust gas recirculation amount (EGR amount), which determine the output or operating state, can be electrically controlled. An electronic control unit (E-ECU) 18 for performing control is provided. Further, an electronic control unit (HV-ECU) 19 for controlling the number of revolutions, torque, power generation, and the like of the motor 2 and the generator 3 is provided. Each of these electronic control devices 18 and 19 is mainly composed of a microcomputer, and performs necessary control command signals by performing calculations based on programs and data stored in advance and input data. Is configured to be output.
[0017]
FIG. 4 is an alignment chart of the planetary gear mechanism constituting the synthesizing mechanism 5 described above. Since the internal combustion engine 1 is connected to the carrier (C) 8, a torque acts on the carrier 8 in a direction to increase the rotation speed. Torque acts on the sun gear 6 and the ring gear 7 on both sides of the carrier 8 in a direction to reduce the rotation speed. Note that the output torque of the motor 2 acts in a direction to increase the rotation speed of the ring gear 7.
[0018]
Therefore, when the rotation speed of the generator 3 is reduced in the operation state shown by the solid line in FIG. 4, the rotation speed of the carrier 8 and the internal combustion engine 1 connected thereto is changed as shown by the broken line in FIG. Depressed. On the other hand, when the rotation speed of the generator 3 is increased, the rotation speeds of the carrier 8 and the internal combustion engine 1 are increased as shown by a chain line in FIG. Therefore, in the configuration shown in FIG. 3, the generator 3 is a rotation speed control mechanism that changes the rotation speed of the internal combustion engine 1.
[0019]
The control device of the present invention for the above-described hybrid vehicle executes control for low-temperature combustion of the internal combustion engine 1 as described below. FIG. 1 is a flowchart for explaining a control example for that purpose. First, it is determined whether there is a request for low-temperature combustion (step S1). The point is to determine whether it is necessary to reduce the amount of NOx generated in the internal combustion engine 1 itself. For example, the amount of NOx stored in the catalyst increases to a predetermined value or more, and the rich spikes and In a state where the reduction of the stored nitrate nitrogen cannot be performed due to the temporary increase of the air-fuel ratio, a request for low-temperature combustion is satisfied.
[0020]
Therefore, when the NOx storage amount of the catalyst is still sufficiently lower than the predetermined value, or when the NOx storage amount can be reduced by rich spike or the like, a negative determination is made in step S1, and in that case, control is particularly performed. Return without. Conversely, if it is determined in step S1 that the NOx generation amount in the internal combustion engine 1 needs to be reduced, the determination is made as to whether or not the operating point at that time can perform low-temperature combustion. Is performed (step S2).
[0021]
Low-temperature combustion is an operation state of the internal combustion engine 1 in which the supply temperature (intake amount) of an inert gas such as EGR gas is increased to lower the combustion temperature, and the amount of the inert gas is such that the generation amount of soot is maximized. It is increased more than a certain amount. Therefore, low-temperature combustion is possible when the load of the internal combustion engine 1 is low or light, and is executed, for example, in an operation state indicated by a region A in the output diagram of FIG. Therefore, for example, when the operating point is at the operating point indicated by the point P1 in FIG. 2, the operating point is within the low-temperature combustion area A, and low-temperature combustion is possible, and the determination in step S2 is affirmative.
[0022]
If a positive determination is made in step S2, low-temperature combustion is immediately performed (step S3). Then, it is determined whether the output of the motor 2 is necessary (step S4). In this case, since the output torque of the internal combustion engine 1 sufficiently satisfies the output request and the determination is affirmative in step S2, the output of the motor 2 is not necessary. Therefore, a negative determination is made in step S4, and the process returns. The series of controls in steps S1 to S4 is a normal control when performing low-temperature combustion.
[0023]
On the other hand, if the current operating point is outside the low-temperature combustion area A shown in FIG. 2, a negative determination is made in step S2. In this case, it is determined whether or not the output of the internal combustion engine 1 at that time is in the low-temperature combustion area A (step S5). This is a judgment as to whether or not an equal output line corresponding to the output at that time is in the low-temperature combustion region A, in accordance with the output diagram shown in FIG.
[0024]
Therefore, for example, in the operation state indicated by the point P2 in FIG. 2, since the equal output line passing through the operation point P2 is in the low-temperature combustion area A, the determination is affirmative in step S5. If a positive determination is made in step S5, it is necessary to move the operating point into the low-temperature combustion area A in order to perform low-temperature combustion. It is determined to be a point (step S6). Specifically, the rotation speed of the internal combustion engine 1 is determined to be on the high rotation speed side so that the operating point moves on the equal output line to the high rotation speed side and enters the low temperature combustion region A. The determination of the number of rotations can be performed using, for example, a map prepared in advance.
[0025]
A shift operation is performed so as to achieve the rotation speed determined in this way (step S7). This is a control for changing the rotation speed of the internal combustion engine 1. In the hybrid vehicle shown in FIG. 3, by controlling the rotation speed of the generator 3 as described with reference to FIG. This is executed by changing the rotation speed of the internal combustion engine 1.
[0026]
Next, the process proceeds to step S3, in which low-temperature combustion is performed by, for example, increasing the amount of exhaust gas recirculation. In this case as well, there is no need to drive the motor 2 in particular, so a negative determination is made in step S4 and the process returns.
[0027]
On the other hand, if the current operating state of the internal combustion engine 1 is at the operating point indicated by the point P3 in FIG. 2, a negative determination is made in step S5. This is because the equal output line passing through the point P3 does not enter the low-temperature combustion area A described above. Therefore, in such a state, the operating point does not enter the low-temperature combustion area A regardless of how the rotational speed of the internal combustion engine 1 is changed while maintaining the output.
[0028]
Therefore, when the output of the internal combustion engine 1 is reduced by the amount of the motor output by driving the motor 2, it is determined whether or not the reduced output is in the low temperature combustion region A (step S8). In FIG. 1, this is described as "can low-temperature combustion be possible with the engine + motor?" In the state shown by the point P3 in FIG. 2, when the output of the internal combustion engine 1 is reduced by the amount of the output possible by the motor 2, the operating point moves to the point P3 '. Since the equal output line passing through the operating point P3 'is in the low-temperature combustion area A, or has the maximum output in the low-temperature combustion area A or an output close thereto, in this case, the determination is affirmative in step S8. You.
[0029]
If a positive determination is made in step S8, the output of the internal combustion engine 1 that can minimize the motor output is obtained (step S9). That is, the maximum output of the internal combustion engine 1 in the low-temperature combustion area A or an output close thereto is obtained. This can be determined from the map.
[0030]
Next, the rotation speed of the operating point entering the low temperature combustion area A is determined by the changed output (step S10). In the output diagram shown in FIG. 2, this is a control in which the rotational speed is increased on an iso-output line passing through the point P3 'to change to an operating point that enters the low-temperature combustion area A, and may be determined based on a map. it can.
[0031]
Then, in order to compensate for the shortage caused by lowering the output of the internal combustion engine 1 with the motor 2, the motor output is calculated (step S11). The motor output is the difference between the output at point P3 and the output at point P3 'in the example shown in FIG.
[0032]
Thereafter, the process proceeds to step S7, and the speed change operation is performed so that the rotation speed is determined at step S10. This is executed by controlling the rotation speed of the generator 3 in the example of the hybrid vehicle shown in FIG. Further, the process proceeds to step S3, where low-temperature combustion of the internal combustion engine 1 is performed. In this case, since it is necessary to drive the motor 2, an affirmative determination is made in step S4, and the output of the motor 2 is controlled so as to be the output calculated in step S11 (step S12).
[0033]
That is, in this case, the motor 2 as another power source is driven so as to substitute a part of the output of the internal combustion engine 1, and as a result, the operating state of the internal combustion engine 1 is changed to a state where low-temperature combustion can be performed. Be changed. Thereafter, the rotation speed is controlled so as to be an operating point at which low-temperature combustion is possible, and low-temperature combustion is performed. Therefore, low-temperature combustion, which cannot be performed by controlling the internal combustion engine 1 alone, is enabled by using other power sources together, and the amount of air pollutants such as NOx generated in the internal combustion engine 1 is suppressed. The exhaust gas as a whole can be made favorable, and at least deterioration of the exhaust gas can be prevented or suppressed.
[0034]
If the output of the internal combustion engine 1 cannot be reduced to such a degree as to enter the low-temperature combustion area A even when the motor 2 is driven due to a large output request amount for the hybrid vehicle, the above-mentioned step S8 is negative. Is determined. In this case, the routine immediately returns without performing any control.
[0035]
Here, the relationship between the above specific example and the present invention will be briefly described. The functional means of step S1 shown in FIG. 1 corresponds to the low-temperature combustion determining means of the present invention, and the functional means of steps S2 and S5. Corresponds to the output determining means of the present invention, the functional means of steps S9, S11 and S12 correspond to the output changing means of the present invention, and the functional means of steps S10 and S7 correspond to the present invention. Corresponds to the rotation speed control means.
[0036]
Note that the present invention is not limited to the specific examples described above. Therefore, the hybrid vehicle targeted by the present invention may have, for example, the configuration shown in FIG. 5 in addition to the configuration shown in FIG. In the hybrid vehicle shown in FIG. 5, a continuously variable transmission 21 is connected to an output side of the internal combustion engine 1 via a torque converter 20, and a motor / motor as another power source is connected to an input side of the continuously variable transmission 21. A generator 22 is connected, and output is provided from the continuously variable transmission 21 through a counter gear pair 14, a final shaft 13, and a final gear pair 16. Other configurations are the same as those in FIG. 3 and are denoted by the same reference numerals as in FIG. Therefore, in the hybrid vehicle having the configuration shown in FIG. 5, the control of the rotation speed for performing the low-temperature combustion operation of the internal combustion engine 1 is executed by the continuously variable transmission 21, which corresponds to the rotation speed control mechanism of the present invention. Become.
[0037]
【The invention's effect】
As described above, according to the present invention, when there is a request to perform low-temperature combustion on an internal combustion engine mounted in combination with another power source, the output of the internal combustion engine at that time is determined in a predetermined low-temperature combustion range. If not, the other power source is driven and the output of the internal combustion engine is changed so as to enter the low-temperature combustion region, and then, while maintaining the changed output, the rotation speed of the internal combustion engine is reduced. Since the operating point is changed and the operating point is set to the operating point in the low-temperature combustion region, the amount of NOx and soot generated in the internal combustion engine is reduced, and deterioration of exhaust gas as a whole of the vehicle can be prevented. . Further, since low-temperature combustion that cannot be achieved by controlling the internal combustion engine alone can be achieved, purification of exhaust gas can be promoted also in that respect.
[0038]
In particular, according to the second aspect of the present invention, the changed output of the internal combustion engine is set to the maximum output that enters the low-temperature combustion region or an output close thereto, so that the entire vehicle before and after changing the output of the internal combustion engine is changed. The output of other power sources required to maintain the output as power may be small, so other power sources such as motors are downsized, and the accompanying accessories such as power storage devices are downsized, Can be improved.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining a control example by a control device of the present invention.
FIG. 2 is a diagram schematically showing an output diagram of the internal combustion engine.
FIG. 3 is a schematic diagram showing an example of a drive system of a hybrid vehicle targeted by the present invention.
FIG. 4 is an alignment chart of a planetary gear mechanism constituting the synthesizing mechanism.
FIG. 5 is a schematic diagram showing another example of the drive system of the hybrid vehicle targeted by the present invention.
[Explanation of symbols]
1: Internal combustion engine, 2: Motor, 3: Generator, 18, 19: Electronic control unit,
21: continuously variable transmission, 22: motor generator.

Claims (2)

An internal combustion engine capable of performing low-temperature combustion that inhales more inert gas than an inert gas intake amount at which the generation amount of soot is maximized; another power source; and a rotation of the internal combustion engine that is connected to an output side of the internal combustion engine. A control device for a hybrid vehicle having a rotation speed control mechanism for changing the number of rotations.
Low-temperature combustion determining means for determining whether there is a request for low-temperature combustion,
Output determining means for determining whether or not the output of the internal combustion engine when there is a request for low-temperature combustion is in the low-temperature combustion region;
When it is determined that the output of the internal combustion engine has not entered the low-temperature combustion region, output changing means for driving the other power source and changing the output of the internal combustion engine so as to enter the low-temperature combustion region. ,
Rotation speed control means for changing the rotation speed of the internal combustion engine by the rotation speed control mechanism such that the operating point of the internal combustion engine at the changed output becomes the operating point in the low temperature combustion region. Hybrid vehicle control device. The output changing means drives the other power source so that the output of the internal combustion engine becomes a maximum output or an output close to the maximum output in an output that enters the low-temperature combustion region, and changes an output of the internal combustion engine. The hybrid vehicle control device according to claim 1, wherein the control device is configured to change.

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