JP2001164959A - Engine control device for hybrid car having exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device of a hybrid car having an exhaust emission control device capable of providing sufficient particulate (PM) reduction effect. SOLUTION: This engine control device comprises: a motor 2 for driving wheels 6 of a vehicle 1; a battery 3 for supplying power to the motor; an engine 4 for actuating a generator 5 for supplying the power to the battery; an exhaust emission control device 14 for oxidizing a carbon captured by a filter arranged in an exhaust passage (r) of the engine for regenerating the filter; a charge state sensing means 23 for detecting a charged state of the battery; operation condition sensing means 21, 22 for detecting operation conditions of the vehicle; and control means 10, 11 for enabling constant operation Mn of the engine 4 under exhaust temperature capable of regenerating the filter 17, and for controlling constant operation of the engine 4 at least even when the charging of the battery 3 is shorted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device for a hybrid vehicle which assists driving by an electric motor by driving an engine, and more particularly to a method for generating nitrogen dioxide by using an oxidation catalyst provided in an exhaust passage of an engine. The present invention relates to an engine control device for a hybrid vehicle equipped with an exhaust gas purification device that oxidizes carbon collected in a filter on the downstream side to regenerate the filter.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine, especially a diesel engine, contains particulates containing carbon fine particles and the like as nuclei, and the diesel particulates are collected in order to collect the particulates without releasing them into the atmosphere. 2. Description of the Related Art A particulate filter is mounted on an exhaust path of an engine. In this type of particulate filter, it is necessary to burn the collected particulates in a timely manner to regenerate the particulate filter, and regenerating means by heating with an electric heater and supplying secondary air is used. Further, in recent years, as shown in FIG. 7, a catalyst regeneration type filter device mounted on a vehicle has been developed. In the catalyst regeneration type filter device A, an oxidation catalyst carrier 110 carrying an oxidation catalyst and a particulate filter 120 are arranged in series in an exhaust passage 100.

[0003] The oxidation catalyst of the oxidation catalyst carrier 110 converts nitrogen monoxide (NO) in exhaust gas into highly active nitrogen dioxide (NO).
₂ ) oxidizes to NO ₂ by the reaction of the following formula (1).
Generate 2NO + O ₂ → 2NO ₂ (1) On the other hand, the particulate filter 120 collects particulates containing carbon particles from the exhaust gas, and flows the collected particulates down from the oxidation catalyst carrier 110 side. It is oxidized by high-activity nitrogen dioxide (NO ₂ ) (see the following formulas (2) and (3)), and the gaseous nitric oxide (NO) and carbon dioxide (CO ₂ ) generated here are discharged. By doing so, the particulate filter 130 is reproduced.

NO ₂ + C → NO + CO (2) NO ₂ + CO → NO + CO ₂ (3) In such a catalyst regeneration type filter device A, highly active nitrogen dioxide (NO ₂ ) Is used, the particulates on the particulate filter 130 that have received the supply are burned and removed by the combustion reaction represented by the above equations (2) and (3). However, the combustion reaction performed here is not stable when the exhaust gas temperature is as low as 250 ° C. or less, so that sufficient filter regeneration performance by particulate (PM) incineration cannot be obtained. For this reason,
The renewable region of the engine is limited to the high load side where the exhaust temperature is high.

[0005] Therefore, in order to increase the exhaust gas temperature, an increase in fuel injection amount, provision of intake and exhaust throttle valves, ignition timing retard, post injection (including secondary injection other than main injection), and the like are performed. Further, as shown by a two-dot chain line in FIG.
Oxidation catalyst carrier 110 and particulate filter 12
0, a branch portion is formed in the exhaust passage 100 between the first and second bypass passages, and a bypass passage 130 is formed to extend from the branch portion.
Is provided with an on-off valve 140. in this case,
When the engine low load region where the regeneration of the particulate filter 120 is not performed is frequently used, the normally closed on-off valve 14
0 is opened to prevent a pressure loss rise due to filter clogging.

[0006]

When a conventional catalyst regeneration type filter device is mounted on a vehicle, the fuel injection amount is increased and the intake / exhaust throttle valve is provided for regeneration of the filter. This leads to deterioration of fuel efficiency and the like. On the other hand, as shown in FIG. 7, when the bypass 130 is opened in the low engine load region where the exhaust gas temperature is low to prevent clogging of the filter, particulates (PM) are released to the atmosphere, and sufficient particulates (PM) are released.
No reduction effect has been obtained. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and to provide an engine control device for a hybrid vehicle including an exhaust gas purification device capable of obtaining a sufficient particulate reduction effect.

[0007]

According to the first aspect of the present invention, there is provided an electric motor for driving wheels of a vehicle, a battery for supplying electric power to the electric motor, and an electric power for at least the battery. An engine that drives a generator to supply air, and an oxidation catalyst provided in the exhaust path of the engine generates nitrogen dioxide, and the nitrogen dioxide oxidizes carbon trapped in a filter on the downstream side to produce a filter. An exhaust gas purifying device for regeneration, a charge state detection means for detecting a charge state of the battery, an operation state detection means for detecting an operation state of the vehicle, and a steady operation of the engine at an exhaust temperature at which the filter can be regenerated. And control means for controlling steady operation of the engine when at least the battery is in an insufficiently charged state. In this way, when the battery is in a state of insufficient charge, the engine can be controlled in a steady operation that can maintain the exhaust temperature at which the filter can be regenerated,
That is, when the engine is driven due to insufficient battery charge, the exhaust gas temperature is maintained in a state in which the filter can be regenerated by particulate incineration by performing steady operation while charging the battery, so that the filter does not become clogged. . Further, unlike the conventional apparatus, a bypass passage is provided in the exhaust passage, and there is no need to discharge the particulates from the bypass passage when the exhaust temperature is low, so that there is no particulate discharged to the atmosphere. Moreover,
Since there is no need to provide a bypass in the exhaust path, and there is no need to increase the amount of fuel to be injected or to use intake and exhaust throttle valves, costs can be reduced, and fuel consumption can be reduced.

According to a second aspect of the present invention, in the engine control apparatus for a hybrid vehicle provided with the exhaust purification device according to the first aspect, the engine selectively selects one or both of the generator and the driving wheels of the vehicle. When the battery is not in an insufficient charge state, the control means selects a motor drive priority mode in which the output shortage in the electric motor drive is compensated by a steady operation of the engine when the battery is not in an insufficient charge state. In this case, the engine drive priority mode in which the output shortage in the steady operation is compensated by the electric motor operation is selected. Thus, the engine selectively drives one or both of the generator and the drive wheels of the vehicle,
In the case of a so-called parallel hybrid, it is possible to select a steady operation mode in which the motor drive is prioritized when the battery is not in the insufficient charge state, and to select a steady operation mode in which the engine drive is prioritized when the battery is in the insufficient charge state. In the mode, even when the engine is operated steadily, the exhaust temperature is maintained in a state in which the filter can be regenerated by particulate incineration as in the case of the first aspect, so that the filter does not become clogged. Preferably, when an output shortage occurs in the steady operation in the engine drive priority mode, it is preferable to perform a higher output steady operation with an increased output. In this case, it is possible to cope with the load required by the vehicle and to ensure a good running feeling.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an engine control device 1 for a hybrid vehicle provided with an exhaust gas purification device according to an embodiment of the present invention. The hybrid car C shown in FIG.
An electric vehicle (EV) is a series type, and runs (EV running) with an electric motor (hereinafter simply referred to as a motor) 2. When the charge amount of the battery 3 decreases, the engine 4, which is a diesel engine, is driven, and the generator 5 is driven. Turn to charge the battery and continue driving. In this hybrid vehicle C, the driving wheels 6 are composed of a rotational force transmission system 601 and a transmission 7
The motor 2 is supplied with power from a battery 3, and the battery 3 is charged by a generator 5, and the generator 5 is connected to the engine 4 and charged when the engine is driven.

The generator 5 has a current controller 9 which functions as a converter when receiving a power generation signal Sd from a motor controller (hereinafter simply referred to as a motor controller) 10 which will be described later. Is switched to the power generation state, the power of the generator energy is converted, and the power is supplied to the battery 3. In addition, when the start signal Ss is received, a start current is supplied from the battery 3 to the generator 5, and the generator 5 can be driven as a starter. The motor 2 is an AC machine, and a coil (not shown) in the motor 2 is connected to the motor drive circuit 8, and a rotor (not shown) transmits its rotational force to the transmission 7. The transmission 7 is configured to transmit the torque of the motor 2 to a torque transmission system 601 via a reduction gear train (not shown).

The motor drive circuit 8 functions as an inverter, converts the energy of the battery 3 into AC power and supplies it to the motor 2 to drive it.
The output is adjusted according to the current control signal Si. The engine 4 is controlled by an engine control unit (hereinafter simply referred to as an engine controller 11), includes a fuel injection valve (not shown) for supplying fuel, and includes an exhaust manifold 12, an exhaust pipe 13, an exhaust gas purifying device 14 (not shown) in an exhaust system. A muffler and the like are provided, and these form an exhaust path r. The motor controller 10 and the engine controller 11 are both main components of a microcomputer, and are connected to each other by a signal line k so as to enable serial communication.

The exhaust gas purifier 14 has a casing 15
The catalyst converter 16 and the D
-Sel particulate filter (hereinafter simply referred to as filter
17) are provided in series. The catalytic converter 16 is
A platinum-based oxidation catalyst is supported on a catalyst carrier 18 of
You. The oxidation catalyst converts nitrogen monoxide (NO) in the exhaust gas into oxygen O _Two
Oxidation with high activity nitrogen dioxide (NO_Two).
The filter 17 is a carbon particulate
And filter and collect the exhaust gas (PM).
Ceramic honeycomb structure with passages stacked in parallel
It is formed as a structure.

The exhaust gas purifying apparatus 14 has an engine
When the temperature of the exhaust gas in the step 4 is low (for example, 250 ° or less)
If so, nitrogen dioxide on the catalytic converter 16
(NO _Two) Is reduced and particulates are downstream
Are sequentially collected by the filter 17 and accumulated. On the other hand,
When the exhaust gas temperature of gin 1 rises (for example, 250 °
Above), acid of nitric oxide (NO) as shown in formula (1)
Reaction is promoted, and highly active nitrogen dioxide (NO_Two) Is raw
Formed and flows downstream. At this time, it is collected by the filter 7
Particulates are highly active nitrogen dioxide (NO_Two)of
After the supply, the oxidation reaction of formulas (2) and (3)
The incineration was eliminated and the particulate filter 17 was regenerated.
It is.

The motor controller 10 is a load sensor 2 for outputting an open / close signal Sm from the main switch 20 and an accelerator pedal depression amount θa signal to an input port (not shown).
1, driving state detecting means such as a vehicle speed sensor 22 for outputting a vehicle speed _VV signal, a battery sensor 23 for outputting a charge amount Vb signal of the battery 3 as a charging state detecting means, and a brake sensor 24 for outputting a brake signal B are connected. Is done. Further, an output port (not shown) of the motor controller 10 is connected to the drive circuit 8 of the motor 2, and is configured to output a current control signal Si.

The engine controller 11 takes in each operation state detection signal k received by the motor controller 10 to its input port via a signal line. Further, the engine controller 11 controls the fuel injection amount signal S corresponding to the steady operation.
q is output to an electronic governor 25 that forms a fuel supply device of the engine 4 through an output port (not shown). Here, the motor controller 10 particularly has the following functions.

As a control means, the engine 4 is connected to the filter 1
Exhaust temperature Tg (for example, 250 ° C. or higher) at which regeneration can be performed
(See hatching in FIG. 3 (a)), steady operation Mn set as the best fuel efficiency point is possible, and at least the state of charge of the battery is insufficiently charged (charge amount: V _LOW or less). (Figure 3)
The engine 4 is controlled by the steady-state operation Mn in (b) the engine-on region). Here, the drive of the engine 4 is controlled in the steady operation Mn so that the output of the motor 2 will not be insufficient due to the shortage of the charged amount Vb. Hereinafter, the operation of the engine control device of the hybrid vehicle will be described according to each control program. The motor controller 10 and the engine controller 11 start control in response to a key-on signal Sm of the main switch 20.

In step a1 of FIG. 3, the motor controller 10 fetches the current operating state data, that is, the signals such as the accelerator pedal depression amount θa, the vehicle speed Vv, the charge amount Vb of the battery 3, the brake B, and the like, and a step a2.
Proceed to. Step a2 The uptake charge amount Vb signal of the battery 3, the value is insufficiently charged state (charge amount: V _{LO W}
It is determined whether or not the value exceeds V (see FIG. 3B).
_If the value falls below _LOW , the process proceeds to step a4. In step a4, the engine controller 11 outputs a fuel injection amount signal to the electronic governor on the assumption that the battery charge amount is insufficient, and at the same time, outputs a start signal Ss from the motor controller 10 to the current control unit 9, and the generator 5 By starting as a starter,
Start running the engine. At this time, the output of the signal output to the electronic governor is controlled so that the injection amount increases stepwise, and the signal is driven in a steady operation Mn (see FIG. 2) that can finally maintain the exhaust temperature at which the filter 17 can be regenerated. An injection amount control signal is output as much as possible. When the charge amount reaches a3 from step a4 or from step a2 assuming that the charge amount is sufficient, in step a3, the drive of the motor is controlled by a control current value output from the motor controller 10 based on information such as the accelerator opening and the vehicle speed. You. Thereafter, it is determined in step a5 whether or not the key is turned off. When the key is turned off, the vehicle is determined to be stopped, and the control is terminated. If the key is on, this control is repeated.

Therefore, in the engine control apparatus 1 for a series-type hybrid vehicle shown in FIG. 1, when the engine 4 is driven due to insufficient battery charge, the engine 4 is operated in a steady state Mn.
The exhaust temperature is maintained in a state in which the filter 17 can be regenerated by particulate incineration while the battery is charged by being driven by the, so that the particulates on the filter are favorably burned and removed.

FIG. 4 shows an engine control device 1a for a hybrid vehicle according to a second embodiment. The engine control device 1a of the hybrid vehicle here is of a parallel type,
Many of the components are the same as those of the series hybrid vehicle shown in FIG. 1. Here, the same reference numerals are given to the same parts, and the reference numerals a are added to the same reference numerals for the parts corresponding to the functions, and the repeated explanation is omitted. In this hybrid vehicle, drive wheels 6 are connected to a motor 2a via a transmission 7a, and the motor 2a is connected to a battery 3a.
Upon receiving more power supply, the battery 3a is connected to the generator 5a, and the generator 5a is connected to the engine 4a and charged when the engine is driven. An output shaft (not shown) of the engine 4a is connected to the transmission 7a via an electromagnetic clutch 20. The connection and disconnection of the clutch 20 is controlled by a clutch operation signal Sc of the engine controller 11a. The transmission 7 transmits the torque of the motor 2a to the torque transmission system 601 via a reduction gear train (not shown), and transmits the torque from the engine 4a when the clutch 20 is engaged via the reduction gear train (not shown). 601.

The motor controller 10a outputs a fuel injection amount signal Sq corresponding to an operation range set according to the operation state detection signal to an electronic governor 25a constituting a fuel supply device of the engine 4a via an output port (not shown). The control program of FIG. 5 is stored and processed in a ROM (not shown) of the motor controller 10a. The motor controller 10a particularly has the following functions.

As a control means, the engine 4a can maintain the exhaust temperature Tg (for example, 250 ° C.) at which the filter 17 can be regenerated. Mn1 is set in the same manner as Mn, but a difference may be set as the case may be.) Mn1 and high-power steady operation Mn2 capable of increasing the output by a predetermined amount from the same steady operation Mn1 can be controlled. That is, the state of charge of the battery 3a is the state of insufficient charge (charge amount: V _LOW ) in FIG.
When the engine 4a is determined to be in the engine drive priority mode, the engine 4a is steadily operated at the steady point Mn1, and if the output is insufficient, the engine 4a is steadily operated with the higher output steady operation Mn2. It is set as follows.

Note that the high output steady point Mn2 is shown in FIG.
As shown in the figure, the engine control is performed at the set torque T2 (set fuel injection amount) at the relatively high engine speed Ne2, and at the steady point Mn1, the relatively low engine speed N2 is set.
At e1, the engine is preset so that the engine control is performed at the set torque T1 (set fuel injection amount). Hereinafter, the operation of the engine control device 1a of the hybrid vehicle will be described according to each control program. Motor controller 10
a, the engine controller 11a
Control is started by the key-on signal Sm.

In step s1 of FIG. 5, the motor controller 10a fetches each signal of the operating state data, and proceeds to step s2. Here, the charge amount Vb signal of the battery 3 is fetched, and the charge amount Vb is set to the undercharge voltage: V
_{If LOW} is exceeded, go to step s3;
Proceed to. In step s3, the motor control in the motor drive priority mode is executed. In this motor operation control, the motor 2a is driven and controlled by the motor controller 10a in accordance with the control current value based on information such as the accelerator opening and the vehicle speed, as in the first embodiment. After the execution of such motor control, the process proceeds to step s4. In step s4, the motor output PS is compared with the required output PSO of the vehicle calculated from the vehicle speed Vv and the accelerator opening θa, and if the required output PSO exceeds the required output PSO, the process proceeds to step s5, where the engine is not operated. .

If it is determined in step s4 that the motor output PS is lower than the required output PSO and the output is insufficient, the process proceeds to step s6, where the motor controller 10a operates at a relatively low engine speed Ne1 and at a steady state at the set torque T1. An engine drive signal is output to the engine controller 11a to perform the operation Mn1, and the engine controller 11a outputs an injection amount signal Sq corresponding to the steady operation Mn1 to the governor 25.
and the engine is operated. At this time, the first embodiment
In the same manner as described above, the generator 5a is driven by a motor as a starter. After starting the engine operation, the process proceeds to motor control in step s7. Here, the remaining value obtained by subtracting the output Pe of the engine that is in steady operation Mn1 from the currently required required output PSO of the vehicle is calculated as the motor output PS covered by the motor.
a is a current control signal Si corresponding to the governor output of the motor 2a.
Is output to the motor drive circuit 8, and a motor drive current is supplied to the motor 2a.

On the other hand, when step s8 is reached from step s2, the engine is operated in a steady state Mn as in step s6.
Drive 1 Then, in step s9, the output Pe of the engine due to the steady operation Mn1 in the engine drive priority region.
Is compared with the current required output PSO of the vehicle calculated from the vehicle speed Vv and the accelerator opening θa. If the required output PSO exceeds the output Pe of the engine, the motor 2a is switched at step s10.
Is stopped, the process proceeds to step s13, and if it is lower, the process proceeds to step s11. The motor controller 10a increases the engine speed Ne2 to increase the engine output Pe.
Then, an engine drive signal is output to the engine controller 11a in order to perform the high output steady operation Mn2 at the set torque T2, and the engine controller 11a outputs the injection amount signal Sb corresponding to the steady operation Mn2 (see FIG. 6A) to the governor. 2
5a is output and the engine is driven in the state of steady operation Mn2.

In step s12, the remaining value obtained by subtracting the output Pe of the engine that performs the high-power steady operation Mn2 from the current required output PSO of the vehicle is basically calculated as the motor output PS, and further exceeds the value by a predetermined amount. Thus, the motor output PS is corrected and set. Then, a current control signal Si is output to the motor drive circuit 8, and the value I is supplied to the motor 2a.
Motor drive current is supplied. As a result, the motor 2a operates in a state of assisting the engine.

When step s13 is reached from steps s10 and s12, the resultant force of the current engine output Pe and the motor output PS when the motor is driven exceeds the current required output PSO. In order to continue the driving and perform the charging process of the battery 3a,
A command is issued to output a power generation signal Sd to the current controller 9 via the engine controller 11a, and a step s14 is executed.
The process returns to step s1 unless the main switch 20 is key-off, and the control is terminated by key-off.

When the engine is driven, the engine control device 1a of the parallel hybrid vehicle shown in FIG. 4 sets the engine 4a at an exhaust temperature (250 in FIG. 3A) at which the filter can be regenerated.
(° C. or more). For this reason, the exhaust gas temperature is reduced by the filter 17 due to the particulate incineration both when the engine 4a is driven due to insufficient battery charge (steps s8 and s11) and when the engine is driven for motor assist (step s6).
Since clogging is maintained in a reproducible state, clogging does not occur.

[0029]

As described above, according to the first aspect of the present invention, when the battery is in a state of insufficient charge, the engine can be controlled in a steady operation region where the exhaust gas temperature at which the filter can be regenerated can be maintained.
That is, when the engine is driven due to insufficient battery charge, the exhaust temperature is maintained in a state in which the filter can be regenerated by particulate incineration while charging, and the filter is not clogged by the steady operation of the engine. Further, a passage for bypassing the filter is provided in the exhaust passage as in the conventional device, so that it is not necessary to release the particulates from the bypass passage to the atmosphere when the engine is operating at a low exhaust temperature. Can be reduced.

According to a second aspect of the invention, in the case of a so-called parallel hybrid, the motor drive priority mode is selected when it is determined that the battery is not in an insufficient charge state, and the engine drive priority mode is selected when it is determined that the battery is in an insufficient charge state. Mode, and in both of these modes,
Since the engine is operated in a steady state, the filter can be prevented from being clogged by maintaining the exhaust gas temperature in a state in which the filter can be regenerated by particulate incineration. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an engine control device of a hybrid vehicle including an exhaust gas purification device as one embodiment of the present invention.

FIG. 2 is a characteristic diagram of a target vehicle speed calculation map used in the engine control device of FIG. 1;

FIG. 3 is a flowchart of a main routine used in the engine control device of FIG. 1;

FIG. 4 is a schematic configuration diagram of an engine control device for a hybrid vehicle as another embodiment of the present invention.

FIG. 5 is a flowchart of an engine / motor control routine used in the engine control device of FIG. 4;

6A and 6B are diagrams for explaining control characteristics of the engine control device of FIG. 4; FIG. 6A is an explanatory diagram of a steady operation region; FIG. .

FIG. 7 is a schematic configuration diagram of a conventional device.

[Explanation of symbols]

 2 motor 4 engine 10 motor controller 11 engine controller 14 exhaust gas purification device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F01N 3/24 F02D 29/02 D F02D 29/02 B60K 9/00 E (72) Inventor Satoshi Hiranuma Tokyo 5-33-8 Shiba, Minato-ku, Mitsubishi Motors Corporation (72) Inventor Shinichi Saito 5-33-8, Shiba, Minato-ku, Tokyo, Mitsubishi Motors Corporation (72) Inventor: Keiko Kato 5-33-8 Shiba, Minato-ku, Tokyo F-term in Mitsubishi Motors Corporation (Reference) 3G090 AA02 DA19 EA02 3G091 AA14 AA18 AB02 AB13 BA14 CB02 EA39 FA08 GA06 GB06W GB17X HA15 3G093 AA04 AA07 AA16 AB01 BA19 BA20 CA10 DA06 DB00 DB05 DB10 DB15 EA05 EB00 FA11 5H115 PA13 PG04 PI16 PI22 PI29 PU01 PU24 PU25 QN03 RB08 RE05 SE05 TE07 TI01 TO21 TO23

Claims (2)

[Claims] 1. An electric motor for driving wheels of a vehicle, a battery for supplying electric power to the electric motor, an engine for driving a generator for supplying electric power to at least the battery, and an exhaust passage for the engine. An exhaust gas purifying device that generates nitrogen dioxide with the oxidation catalyst, oxidizes carbon trapped in a downstream filter by the nitrogen dioxide, and regenerates the filter, and a charged state detection that detects the charged state of the battery Means, an operating state detecting means for detecting an operating state of the vehicle, and control for performing steady-state operation of the engine at an exhaust temperature at which the filter can be regenerated, and controlling steady-state operation of the engine at least when the battery is in an insufficiently charged state. And an engine control device for a hybrid vehicle equipped with an exhaust emission control device. 2. An engine control device for a hybrid vehicle equipped with an exhaust gas purification device according to claim 1, wherein said engine is formed so as to selectively drive one or both of said generator and driving wheels of the vehicle. ,
When the battery is not in the insufficiently charged state, the control means selects a motor drive priority mode in which the electric motor alone or the insufficient output of the electric motor drive is supplemented by a steady operation of the engine. An engine control device for a hybrid vehicle equipped with an exhaust gas purification device, wherein an engine drive priority mode is selected in which an output shortage in a steady operation is compensated by the electric motor operation.