JP2003004138A - Power plant - Google Patents

Abstract

(57) [Summary] [Problem] In a power unit for temporarily stopping an engine,
Reduces shock when restarting the engine. When it is determined that an engine restart condition is satisfied while the engine is stopped (S100), the characteristic is changed so that the capacity coefficient of the torque converter decreases (S104). When the capacity coefficient decreases, the torque converter input side torque decreases, and the generated torque at the time of starting the engine decreases, thereby reducing the shock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power plant including an engine and a fluid transmission mechanism such as a torque converter, and more particularly to control related to engine startup.

[0002]

2. Description of the Related Art In a power unit having an engine, the driving torque may fluctuate when the engine is started, and a shock may occur in the power unit itself or in a vehicle equipped with the power unit. In a conventional power unit mounted on a vehicle, in a series of vehicle operations, the engine is usually started once once and not thereafter. Moreover, this starting is done by the driver himself, and even if a shock occurs, it is within the expected range, and it is not as uncomfortable as a shock that occurs unexpectedly.

[0003]

However, in recent years, in order to reduce fuel consumption, the engine may be stopped while the vehicle is stopped and restarted when the vehicle starts. In addition, in a vehicle having two prime movers such as an electric motor in addition to the engine, the operation of the engine is controlled under predetermined conditions, stopped when not needed, and stopped when it is determined to be necessary. The start is performed. The former restart is frequently repeated depending on the operating conditions of the vehicle, which may give an uncomfortable feeling to the passenger. In addition, the latter restart is performed even while the vehicle is running, and since it is not directed by the driver, when a shock occurs, it becomes an accident for passengers, especially for the driver, You may feel uncomfortable.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to reduce the shock generated at the time of starting the engine.

Regarding the technique for reducing the shock at the time of starting the engine, JP-A-8-193531, JP-A-11-351001 and JP-A-2000-11 are available.
It is described in Japanese Patent No. 8266.

[0006]

In order to solve the above-mentioned problems, a power plant according to the present invention includes a fluid transmission mechanism capable of transmitting an output torque of an engine to a wake and changing its characteristics. The characteristics of the fluid transmission mechanism are changed to reduce the shock at engine start. The characteristics to be changed can be, for example, a capacity coefficient and a torque ratio. Further, the change of the characteristic can be executed at the time of starting the engine, or when the engine is stopped, in preparation for the next starting.

The change of the capacity coefficient characteristic is performed so as to lower the capacity coefficient. As a result, the input torque of the fluid transmission mechanism is reduced, and the output torque of the engine is also reduced. Therefore, the reaction force due to the fluctuation of the torque is also reduced, and the shock is reduced.

The torque ratio characteristic is changed so as to reduce the torque ratio. As a result, the torque sent to the wake of the fluid transmission mechanism is reduced, the reaction force is also reduced, and the shock is reduced.

A control device for a power plant, which is another aspect of the present invention, is a device for transmitting the output torque of an engine to a wake and controlling the power plant including a fluid transmission mechanism capable of changing its characteristics. Then, a command to change the characteristics of the fluid transmission mechanism is issued to reduce the shock at the engine start.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. Figure 1
A schematic configuration of a vehicle power unit 10 according to the present embodiment is shown. The power plant 10 has two prime movers, an engine 12 and a rotating electric machine 14. The engine 12 is a reciprocating gasoline engine. Further, the rotating electrical machine 14 receives supply of electric power from a running battery (not shown) via an inverter (not shown), functions as an electric motor, and drives the vehicle. Further, the rotary electric machine 14 is driven by the wheels of the vehicle and functions as a generator during deceleration, converts kinetic energy of the vehicle into electrical energy, and stores the electrical energy in the running battery. In addition, when the amount of electricity stored in the battery for running decreases,
The rotating electric machine 14 is driven by the engine 12 to charge the traveling battery. The outputs of these prime movers are sent to the automatic transmission 16. The automatic transmission 16 includes a fluid transmission mechanism, a transmission mechanism, and a control mechanism. In this embodiment,
The fluid transmission mechanism is a torque converter 18, the transmission mechanism is a gear transmission unit 20 including a plurality of planetary gear mechanisms, and the gear transmission unit 20 also restrains the movement of each element of each planetary gear mechanism. Including clutch and brake. These clutches and brakes are controlled by the selective supply of the working fluid from the fluid pressure controller 22 as a control mechanism. The output of the gear transmission unit 20 is transmitted to the drive wheels by the propulsion shaft.

An auxiliary rotating electric machine 26 is further connected to the output shaft of the engine 12 via a transmission mechanism 24. The transmission mechanism 24 may be a mechanism using an endless flexible member such as a belt or a chain, or a gear train. The auxiliary electric rotating machine 26 functions as a generator when the engine 12 is in operation, charges an auxiliary battery (not shown) that supplies electric power to the engine auxiliary equipment and electric components of the vehicle, and also the electric components. Power directly to. In addition, the auxiliary rotary electric machine 2
When starting the engine 12, 6 receives electric power from the auxiliary battery and functions as an electric motor.

The control of the engine 12, the rotary electric machine 14, the automatic transmission 16 and the like is performed by the control device 28 based on the operating conditions of the vehicle such as the traveling speed, the states of the engine and the automatic transmission, and the driver's request. The selection of the operating state of the transmission, which is requested by the driver, is performed by the shift lever 30 provided in the vehicle compartment. The shift lever 30 is
It has several shift positions corresponding to the operating state of the transmission, the position sensor 30a detects the shift position, and sends a signal corresponding to this to the control unit 28. The driver can select the shift position by moving the shift lever 30. Examples of the shift position are mainly used during parking, and are in a P position for mechanically locking the transmission 16 to prevent the vehicle from moving, an R position for allowing the vehicle to travel backward, and a neutral state for the transmission 16. That is, there are an N position where the drive torque of the prime mover is not transmitted to the drive wheels, a D position where the vehicle can travel forward, and the like. At the D position, the control unit 28 selects an appropriate gear stage according to the vehicle speed, the driver's acceleration request, and the like, and the fluid pressure control unit 22 operates to perform the gear shifting operation. In addition to the D position, there are positions that limit the gears to be shifted, such as the L position and the 2 position.

An engine rotation speed sensor 34 for detecting the rotation speed is provided on the crankshaft of the engine 12, and its output is sent to the control unit 28.
Further, the driver's acceleration request is recognized by the control device 28 based on the operation amount of the accelerator pedal 31 provided in the vehicle compartment detected by the accelerator sensor 31a. In addition, the braking request of the driver is recognized by the control device 28 based on the operation amount of the brake pedal 32 provided in the vehicle compartment detected by the brake sensor 32a.

FIG. 2 shows the outline of the transmission mechanism of the automatic transmission 16. This automatic transmission 16 has an auxiliary transmission O
It has a fifth speed configuration in which D and a main transmission M, which is composed of a simple connection, three planetary gear trains, and has four forward speeds and one reverse speed are combined.
The torque converter 18 is also shown in FIG. 2 and includes a direct coupling clutch LC as shown. The sub transmission OD includes a sun gear S0, a carrier C0, and a ring gear R0.
In connection with this, there is provided a first one-way clutch F-0, a multi-plate clutch C-0 arranged in parallel with the first one-way clutch F-0, and a multi-plate brake B-0 connected in series therewith. On the other hand, the main transmission M includes the sun gears S1 to S3, the carriers C1 to C3, and the ring gear R1.
~ R3 is a simple connection 3 which is directly connected to each transmission element.
A set of gear units P1, P2, P3 is provided, and multi-plate clutches C-1, C- are associated with the transmission elements of each gear unit
2, band brake B-1, multi-plate brake B-2 to B-
4, a one-way clutch F-1 and a second one-way clutch F-2 are provided. Although not shown, each clutch and brake is provided with servo means having a piston for engaging and disengaging the friction material by controlling the servo fluid pressure.

Further, in order to detect the input rotation speed of the automatic transmission 16, an input rotation sensor 36 is provided on the sun gear S0 of the auxiliary transmission OD. The rotation sensor includes a gear-shaped disc and a pickup that is installed on the periphery of the disc and outputs an ON signal and an OFF signal depending on the presence or absence of gear teeth. From the 1st speed to the 4th speed, the sun gear S0
Rotates with the turbine of the torque converter 12, so the input rotation speed of the transmission 16 can be detected. A clutch rotation sensor 38 for detecting the rotation speed of the clutch C-1 or C-2 is provided on the drum of the clutch C-1 or C-2.
Further, in order to detect the output rotation speed of the automatic transmission 14, an output rotation sensor 40 is provided on the propeller shaft or a shaft that rotates integrally with the propeller shaft. The structure of these sensors 38, 40 is similar to that of the input rotation sensor 36.

FIG. 3 is a diagram showing the operating state of each engagement element when a certain gear is selected in the transmission shown in FIG. In the figure, “◯” indicates that the engagement element is engaged and the one-way clutch is locked. “Δ” indicates that the engagement element is engaged, but has nothing to do with power transmission. It should be noted that the range of selected shift speeds is limited in accordance with the position of the shift lever.

As shown in FIG. 3, when the shift state is in the neutral state (P, N positions), the clutch C-1,
Both C-2 are in the released state. In contrast,
When the driving force from the D position, the R position, etc. can be transmitted and the vehicle is ready to travel, the clutch C-1
(For forward movement), the clutch C-2 (for backward movement) is in the engaged state. The engagement operation of the clutch C-1 or the clutch C-2 is executed by operating the shift lever 30,
The actual engagement is completed after a shift period has elapsed after the shift lever 30 was operated. This is because the fluid pressure is supplied to the clutch C-1 or C-2, and it takes time for the friction plates of the clutch to come into complete contact.

The torque converter 18 of this embodiment has a function of changing the characteristics of the capacity coefficient or the torque ratio. This change is performed by changing the cross-sectional area of the circulation flow path in the torque converter 18 using a shield plate or the like, or changing the orientation, shape, etc. of the stator blades. Figure 4
It is a figure which shows the characteristic of a capacity coefficient. The capacity coefficient changes with the speed ratio as shown. Torque converter 18
Has a characteristic shown by a solid line in the figure in a normal use state. In the present embodiment, when the engine is started, the characteristic shown by the broken line in the drawing, that is, the characteristic in which the coefficient is lower than in the normal state in the region where the speed ratio is low is changed.

FIG. 5 is a diagram showing a control flow at the time of starting the engine of this embodiment. First, it is determined whether the engine is stopped (S100). The engine stop in this case is intended for the case where the engine is stopped while a predetermined condition is satisfied while the vehicle is operating. That is, engine start by operating the ignition switch when the shift lever is in the P (parking) or N (neutral) position is not targeted. Engine stop control during vehicle operation is
For example, the rotating electric machine 14 when the vehicle is stopped or running at a constant speed
It is executed when the vehicle is traveling with only the driving force of.

While the engine is stopped, it is determined whether the engine restart condition is satisfied (S102). Specifically, the vehicle speed increases and the engine 12 and the rotating electric machine 1
When it becomes a condition to run by both driving force of 4,
For example, when the accelerator pedal 36 is depressed and it is determined that a larger acceleration is required, the amount of electricity stored in the traveling battery is reduced, and it becomes necessary to perform charging. When the engine restart condition is satisfied, control is performed so as to reduce the capacity coefficient characteristic of the torque converter 18 (S10).
4). Specifically, a control command is sent to the fluid pressure control unit 22, and the control valve for displacement control is drive-controlled. The capacity control mechanism in the torque converter is driven by the fluid pressure, the change control of the capacity coefficient characteristic is executed, and the characteristic shown by the broken line in FIG. 4 is obtained in the low speed ratio region. The engine start control is executed with the capacity coefficient lowered (S106).
When the engine starts, the capacity coefficient characteristic is returned to the normal characteristic.

FIG. 6 is a diagram showing another example of the control flow when the engine is started. The same steps as those in the control flow of FIG. After it is determined in step S102 that the restart condition is satisfied, it is determined whether the accelerator pedal is depressed (accelerator is on) (S11).
0). If the accelerator is on, after starting the engine,
The torque generated by the engine increases and the rotating electric machine 14
It is conceivable that the combined torque will change significantly.
Therefore, it is expected that the shock will increase. In consideration of this, when the accelerator is in the on state, as shown in FIG.
As in step S104 of the control flow of 1., the characteristic that lowers the capacity coefficient is selected. Further, when the accelerator is not in the on state, the characteristic that the capacitance coefficient becomes high is selected (S112). After the selection and change of the capacity coefficient characteristic are completed, the engine is controlled to start, and when the start is confirmed, the capacity coefficient characteristic is controlled to a normal value (S10).
6).

FIG. 7 is a diagram showing another example of the control flow for starting the engine. The individual steps are similar to the previously described steps with the same reference numerals. In this control, when it is determined that the engine is stopped (S10
0), the characteristic change of the capacity coefficient of the torque converter 18 is executed (S104). This prepares for the next engine start. When the engine start is commanded, the engine start control is executed, and after the start, the capacity coefficient characteristic is changed to a normal characteristic (S106).

As described above, when the characteristics are selected so that the capacity coefficient is lowered at the time of starting the engine, the torque on the input side of the torque converter 18, that is, the output torque of the engine is reduced. Therefore, the torque fluctuation caused by the addition of the engine torque is also reduced, and the shock generated as the reaction force of this torque fluctuation is also reduced.

FIG. 8 is a diagram showing still another example of the control flow for starting the engine. This control flow is shown in FIG.
It is characterized in that the torque coefficient is changed, while the capacity coefficient is reduced in the control flow shown in FIG. That is, in the case of the control flow of FIG. 5, when the restart determination is made while the engine is stopped, the characteristic is selected so as to reduce the capacity coefficient, whereas in the present control flow, the torque ratio is reduced. First, the characteristics of the torque converter are selected (S124).

FIG. 9 is a diagram showing still another example of the control flow for starting the engine. This control flow is shown in FIG.
In the control flow shown in (1), the capacity coefficient is decreased and increased, whereas the torque ratio is decreased and increased. That is, in the case of the control flow of FIG. 6, the restart determination is made while the engine is stopped, and the control is performed so that the capacity coefficient is decreased when the accelerator is in the ON state and is increased when the accelerator is in the OFF state. . On the other hand, in the present control flow, when the accelerator is in the on state, the torque ratio is reduced (S124), and when it is in the off state, the torque ratio is increased (S132). Make a choice.

FIG. 10 is a diagram showing still another example of the control flow for starting the engine. This control flow is characterized in that the capacity coefficient is reduced in the control flow shown in FIG. 7, while the torque ratio is changed.
That is, in the control flow of FIG. 7, the characteristic is selected so as to reduce the capacity coefficient while the engine is stopped, whereas in the control flow, the characteristic of the torque converter is selected so as to reduce the torque ratio. Is performed (S124).

By reducing the torque ratio, the torque transmitted to the drive wheels is reduced. Therefore, the torque fluctuation caused by the addition of the engine torque is also reduced, and the shock generated as the reaction force of this torque fluctuation is also reduced.

FIG. 11 is a diagram showing still another example of the control flow for starting the engine. First, it is determined whether or not the vehicle is stopped (S200), and then it is determined whether or not the shift position is a drive position, that is, a position in which the vehicle can travel (S202). The drive position is, for example, a D position or an R position. If it is in the drive position, it is determined whether the engine is operating (S204). The engine is stopped when it is determined that the engine can be stopped, such as when the running battery has a sufficient power storage amount or when the engine cooling water temperature is room temperature and warming up is not required. When the engine is stopped, the characteristic that the capacity coefficient of the torque converter becomes low is selected (S206). As a result, when the engine is started next time, the load on the engine is reduced and it becomes easier to start the engine.

When it is determined in step S204 that the engine is operating, it is then determined whether the brake pedal 32 is depressed or a predetermined amount or more is depressed (S208). The fact that the brake pedal 32 is stepped on means that the driver is requesting that the vehicle be stationary, and therefore the creep force is considered unnecessary. For this reason,
When the brake pedal is depressed, the characteristic that the capacity coefficient is low is selected (S210). As a result, the idle speed of the engine can be reduced,
Fuel consumption can be suppressed.

In step S208, the brake pedal 32
When it is determined that is not stepped on or is slightly stepped on, the control is performed so as to exhibit the same behavior as that of the vehicle of the conventional automatic transmission. That is, control is performed so that creep occurs. For this purpose, a characteristic is selected such that the capacity coefficient is high (S212). As a result, drive torque capable of creeping is generated. When it is determined in step S202 that the shift position is not the drive position, a characteristic that reduces the capacity coefficient is selected (S214). As a result, the idle speed of the engine can be reduced, and fuel consumption at this time can be suppressed.

In the above, control in a hybrid vehicle equipped with a power unit having two types of prime movers, that is, the engine 12 and the rotary electric machine 14, has been described, but the present invention can also be applied to a hybrid vehicle equipped with only an engine. Specifically, due to the signal waiting and other reasons,
The present invention can also be applied to engine start of a vehicle that performs so-called economy traveling in which the engine is stopped and controlled when the vehicle is continuously stopped for a predetermined time or longer.

The above control is executed by the computer provided in the control device 28 operating according to a predetermined program. The control device 28 commands the operation of the fluid pressure control valve of the fluid pressure control unit 22 of the automatic transmission 16,
By this valve operation, a mechanism for changing the characteristic of the capacity coefficient or the torque ratio characteristic in the torque converter 18 operates.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a power plant of the present embodiment.

FIG. 2 is a diagram showing a configuration of a transmission 16.

FIG. 3 is a diagram showing gear selection of the transmission shown in FIG.

FIG. 4 is a diagram showing a capacity coefficient characteristic.

FIG. 5 is a chart showing a control flow of this embodiment.

FIG. 6 is a chart showing another example of the control flow of the present embodiment.

FIG. 7 is a chart showing still another example of the control flow of the present embodiment.

FIG. 8 is a chart showing still another example of the control flow of the present embodiment.

FIG. 9 is a chart showing still another example of the control flow of the present embodiment.

FIG. 10 is a chart showing still another example of the control flow of this embodiment.

FIG. 11 is a chart showing still another example of the control flow of this embodiment.

[Explanation of symbols]

10 vehicle power unit, 12 engine, 14 rotary electric machine, 16 automatic transmission, 22 fluid pressure control section, 26 auxiliary machine rotary electric machine, 28 control section, 30 shift lever, 30
a Position sensor, 31 Accelerator pedal, 31a
Accelerator sensor, 32 brake pedal, 32a brake pedal sensor.

Claims (8)

[Claims] 1. A power plant having an engine and a fluid transmission mechanism for transmitting an output torque of the engine to a wake via a fluid, wherein the fluid transmission mechanism has a function of changing a capacity coefficient characteristic. A power plant that has the characteristics thereof and is changed so that the capacity coefficient becomes low when the engine is started. 2. A power plant having an engine and a fluid transmission mechanism for transmitting output torque of the engine to a wake via a fluid, the fluid transmission mechanism having a function of changing a capacity coefficient characteristic. And a characteristic of the engine, the characteristic of which is changed so that the capacity coefficient becomes low in preparation for restart when the engine is stopped. 3. A power plant having an engine and a fluid transmission mechanism for transmitting the output torque of the engine to a wake via a fluid, wherein the fluid transmission mechanism changes the torque ratio characteristic. A power plant that has a function and whose characteristics are changed so that the torque ratio becomes small when the engine is started. 4. A power plant having an engine and a fluid transmission mechanism for transmitting the output torque of the engine to a wake via a fluid, the fluid transmission mechanism having a function of changing a torque ratio characteristic. And a characteristic of the engine, the characteristics of which are changed so that the torque ratio is reduced in preparation for restarting when the engine is stopped. 5. A control device for controlling a power plant, comprising: an engine; and a fluid transmission mechanism having a function of transmitting an output torque of the engine to a wake via a fluid and changing a capacity coefficient characteristic thereof. A control device that issues a characteristic change command to the fluid transmission mechanism so that the capacity coefficient becomes low when it is determined from the operating condition of the power plant that the engine start condition is satisfied. 6. A control device for controlling a power plant, comprising: an engine; and a fluid transmission mechanism having a function of transmitting an output torque of the engine to a wake via a fluid and changing a capacity coefficient characteristic thereof. In preparation for restart when the engine is stopped,
A controller that issues a characteristic change command to the fluid transmission mechanism so that the capacity coefficient becomes low. 7. A control device for controlling a power plant, comprising: an engine; and a fluid transmission mechanism having a function of transmitting an output torque of the engine to a downstream flow through a fluid and changing a torque ratio characteristic thereof. A control device that issues a characteristic change command to the fluid transmission mechanism such that the torque ratio becomes small when it is determined from the operating condition of the power plant that the engine start condition is satisfied. 8. A control device for controlling a power plant, comprising: an engine; and a fluid transmission mechanism having a function of transmitting an output torque of the engine to a wake via a fluid and changing a capacity coefficient characteristic thereof. In preparation for restart when the engine is stopped,
A controller that issues a characteristic change command to the fluid transmission mechanism so that the torque ratio becomes smaller.