JP2012218580A - Engine starter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption when starting an engine in a hybrid vehicle.SOLUTION: An engine starter (100) is loaded on a hybrid vehicle (1) including an engine (11) having a variable valve operating mechanism (116), a rotating electric machine (12) connected to the engine, and a control means (20) for controlling the rotating electric machine to crank the engine when starting the engine and further controlling the rotating electric machine so as to continue cranking of the engine even after the engine has completely exploded. The engine starter includes a torque reduction means (20) for reducing cranking torque related to the rotating electric machine corresponding to an advance angle amount of an intake valve of the engine due to the variable valve operating mechanism when the control means controls the variable valve operating mechanism so as to change the intake air amount of the engine while starting the engine.

Description

  The present invention relates to a technical field of an engine starter that starts an engine mounted on a vehicle such as a hybrid vehicle.

  As this type of device, for example, a device for determining an advance amount for advancing the closing timing of the intake valve from the most retarded position toward the bottom dead center when starting cranking of the engine has been proposed. Here, in particular, (i) correcting the cranking torque of the motor at the time of cranking according to the determined advance amount, and (ii) the amount of correction of the cranking torque as the temperature is lower in a low temperature environment. Is made larger. (See Patent Document 1).

JP 2009-167920 A

  Here, in a low temperature environment, since the friction related to the engine increases, the cranking of the engine is often continued even after the complete explosion determination is made. Then, in the technique described in Patent Document 1, there is a technical problem that the amount of power consumed when starting the engine may be relatively large.

  The present invention has been made in view of the above-described problems, for example, and an object of the present invention is to propose an engine starter capable of reducing the power consumption when starting the engine.

  In order to solve the above problems, an engine starter according to the present invention cranks the engine when starting the engine, an engine having a variable valve mechanism, a rotating electrical machine connected to the engine, and the engine. And a control means for controlling the rotating electrical machine so as to continue cranking of the engine even after the engine is completely detonated. When the control means controls the variable valve mechanism so as to change the intake air amount of the engine, according to the advance amount of the intake valve of the engine caused by the variable valve mechanism, Torque reduction means for reducing the cranking torque associated with the rotating electrical machine is provided.

  According to the engine starter of the present invention, the engine starter rotates so as to crank the engine when starting the engine, an engine having a variable valve mechanism, a rotating electrical machine connected to the engine, and the engine. It is mounted on a hybrid vehicle that includes a control unit that controls the electric machine and further controls the rotating electric machine so that cranking of the engine is continued even after the engine is completely detonated.

  The rotating electrical machine is, for example, various motors / generators capable of powering and power generation (that is, power regeneration). The variable valve mechanism may be a hydraulic drive type or an electric type. It should be noted that various known modes can be applied to determine whether or not the engine has completely detonated, and the details thereof are omitted here. Here, “completely exploded” means “the engine has reached a state where it can rotate independently”.

  According to the research of the present inventor, the following matters have been found. That is, the hybrid vehicle employs a high expansion ratio in order to improve the fuel consumption efficiency of the engine, and the in-cylinder pressure is lower than that of a normal engine due to its engine characteristics. In particular, when starting an engine where it is difficult to operate the variable valve mechanism, the in-cylinder pressure is low even when ignited, resulting in a low explosive force. For example, in a cryogenic environment such as -30 degrees Celsius, even if it is determined that the engine has completely exploded, in addition to an increase in engine mechanical friction (for example, piston friction), lubricating oil As a result, the viscosity of the engine may increase extremely, and the friction of the entire engine may be increased, leading to unexpected engine stall. Therefore, it is desirable that the cranking of the engine is continued to some extent by the rotating electric motor in order to prevent engine stall even after it is determined that the engine has completely exploded. However, if the cranking of the engine is simply continued, the amount of power consumed in the rotating electrical machine may increase. In addition, in order to supply the amount of power, a battery having a relatively large capacity must be mounted on the hybrid vehicle, and the manufacturing cost of the hybrid vehicle may be relatively high.

  Therefore, in the present invention, when the control means controls the variable valve mechanism so that the intake air amount of the engine is changed (for example, increased) by the torque reducing means during engine startup, the engine caused by the variable valve mechanism The cranking torque related to the rotating electrical machine is reduced according to the advance amount of the intake valve. Here, since the torque generated by the engine increases when the advance amount of the intake valve is increased by the variable valve mechanism, the engine speed does not decrease even if the cranking torque is decreased. This has been found by the inventors' research.

  For this reason, according to the engine starting device of the present invention, it is possible to prevent engine stall while reducing power consumption at the time of starting the engine. In addition, since the battery capacity can be suppressed, manufacturing costs and the like can be suppressed, which is very advantageous in practice.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a block diagram which shows the structure of the vehicle by which the engine starting apparatus which concerns on embodiment of this invention is mounted. It is a flowchart which shows the engine starting control process which the engine starting apparatus which concerns on embodiment of this invention performs. It is a characteristic view showing an example of the relationship between the advance amount of the intake valve and the correction coefficient. It is a time chart which shows an example of each time fluctuation | variation of the torque which concerns on a motor generator, an engine speed, and the advance amount of an intake valve.

  An embodiment of an engine start control device of the present invention will be described based on the drawings.

(Vehicle configuration)
A configuration of a vehicle on which an engine starter according to an embodiment of the present invention is mounted will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a vehicle on which an engine starter according to this embodiment is mounted. In FIG. 1, for convenience of explanation, only members directly related to the present embodiment are shown, and other members are not shown.

  In FIG. 1, a vehicle 1 includes an engine 11, a motor / generator (MG1) 12, a motor / generator (MG2) 13, a power distribution mechanism 14, a battery 15, a power control unit (Power Control Unit: PCU) 16, and an ECU (Electronic). Control Unit) 20 is provided.

  The engine 11 includes a crankshaft 111, an intake valve 112, an exhaust valve 113, a spark plug 114, a piston 115, and a variable valve mechanism (VVT) 116.

  The variable valve mechanism 116 changes the opening / closing timing of the intake valve 112 opened and closed by the intake camshaft by changing the rotation phase of the intake camshaft (not shown) with respect to the rotation phase of the crankshaft 111. The variable valve mechanism 116 may be a hydraulic drive type or an electric type.

  The power distribution mechanism 14 includes a planetary gear mechanism that includes a sun gear, a pinion gear, a carrier that supports the pinion gear so as to rotate and revolve, and a ring gear.

  The carrier shaft 141 of the power distribution mechanism 14 is connected to the crankshaft 111 of the engine 11. The sun gear shaft 142 of the power distribution mechanism 14 is connected to the rotation shaft of the motor / generator 12. A ring gear shaft (that is, a drive shaft) 143 of the power distribution mechanism 14 is connected to the speed reduction mechanism 17 connected to the drive wheels 18 and the motor / generator 13. The carrier shaft 141, the sun gear shaft 142, and the ring gear shaft 143 are actually arranged on the same axis, but here, for convenience of explanation, the extending directions of the shafts are different from each other.

  The battery 15 is electrically connected to each of the motor / generators 12 and 13 via a power control unit 16 capable of appropriately controlling a direct current and an alternating current. The battery 15 is configured to be able to supply electric power to each of the motor generators 12 and 13 and to be charged by regenerative electric power of each of the motor generators 12 and 13.

  The “motor / generator 12” and “ECU 20” according to the present embodiment are examples of the “rotary electric machine” and the “control unit” according to the present invention, respectively.

  In the vehicle 1 configured as described above, when the engine 11 is started, the ECU 20 first controls the motor / generator 12 to crank the engine 11. After starting the cranking, the ECU 20 controls the fuel injection valve (not shown) to supply fuel such as gasoline and ignites it on condition that the rotational speed of the engine 11 reaches a predetermined value. The spark plug 114 is controlled.

  Subsequently, the ECU 20 determines whether or not the rotational speed of the engine 11 is greater than a predetermined threshold value. When it is determined that the rotational speed of the engine 11 is greater than the predetermined threshold, the ECU 20 determines that the engine 11 has completely exploded. On the other hand, when it is determined that the rotational speed of the engine 11 is smaller than the predetermined threshold, the ECU 20 determines that the engine 11 has not completely exploded. In addition, what is necessary is just to include in either case when the rotation speed of the engine 11 and a predetermined threshold value are "equal".

  Here, the “predetermined threshold value” is a value that determines whether or not the engine 11 has completely detonated, and is set in advance as a fixed value or as a variable value according to some physical quantity or parameter. Such a predetermined threshold value is predicted by, for example, a relationship between the engine speed and the probability that the engine will be completely exploded by experiments or simulations, and the engine is surely completely exploded based on the obtained relationship. It may be set as the engine speed.

  Particularly in the present embodiment, the ECU 20 performs a predetermined period of time after determining that the engine has completely exploded in order to prevent an unexpected engine stall in an extremely low temperature environment such as −30 degrees Celsius. The motor / generator 12 is controlled to continue the cranking. Further, when starting the engine, the ECU 20 changes the opening / closing timing of the intake valve 112 (that is, changes the advance amount or retard amount of the intake valve 112), and is the amount of air taken into the engine 11. The variable valve mechanism 116 is controlled so as to change the intake air amount. In addition, what is necessary is just to set suitably how much the opening-and-closing timing of the intake valve 112 is changed according to the characteristic of the engine 11, etc., for example.

(Engine starter)
When the ECU 20 controls the variable valve mechanism 116 so as to change the intake air amount of the engine 11 during the start of the engine 11, the engine starter 100 causes the intake valve of the engine 11 caused by the variable valve mechanism 116. The ECU 20 is configured as an example of the “torque reducing means” according to the present invention that reduces the cranking torque related to the motor / generator 12 in accordance with the advance amount of 112. In the present embodiment, a part of the ECU 20 for various electronic controls of the vehicle 1 is used as a part of the engine starter 100.

(Engine start control process)
Next, an engine start control process executed by the ECU 20 as a part of the engine start device 100 configured as described above will be described with reference to a flowchart of FIG.

  In FIG. 2, first, the ECU 20 determines whether or not the start control of the engine 11 has been started (that is, the engine 11 is cranked by the motor / generator 12) (step S101). When it is determined that the start control of the engine 11 has not been started or the start control has been completed (step S101: No), the processing is once ended.

  If it is determined that the start control of the engine 11 has been started (step S101: Yes), the ECU 20 determines whether it is within Amsec (milliseconds) from the start of the start control (step S102). The predetermined time “A” is set as a time for the motor / generator 12 to output a relatively large cranking torque in order to increase the rotational speed of the stopped engine 11 relatively quickly. If comprised in this way, the time for the rotation speed of the engine 11 to pass through the resonance band which concerns on the vehicle 1 can be shortened, for example.

  When it is determined that it is within A msec from the start of the start control (step S102: Yes), the ECU 20 outputs the initial torque that is a relatively large torque (see times t1 to t2 in FIG. 4). Control the generator 12 and the like (step S109). Thereafter, the ECU 20 executes a process of step S107 described later.

  When it is determined that A msec has been exceeded from the start of the start control (step S102: No), the ECU 20 determines that the rotation speed Ne of the engine 11 is C rpm (rotation per) as a specific example of the “predetermined threshold value”. It is determined whether it is equal to or greater than (minute) (that is, whether or not the engine 11 has completely exploded) is determined (step S103).

  When it is determined that the rotational speed Ne of the engine 11 is less than C rpm (step S103: No), the ECU 20 determines whether the rotational speed Ne of the engine 11 is equal to or higher than B rpm (step S104). When it is determined that the rotational speed Ne of the engine 11 is less than B rpm (step S104: No), the ECU 20 executes the process of step S109 described later after executing the process of step S109 described above.

  When it is determined in the process of step S104 that the rotational speed Ne of the engine 11 is equal to or higher than B rpm (step S104: Yes), the ECU 20 calculates the second start torque and the calculated second start torque. Is output (see times t2 to t5 in FIG. 4), the motor / generator 12 and the like are controlled (step S105).

  The predetermined rotation speed “B” is a value that determines whether or not to calculate the second starting torque, and is set in advance as a fixed value or a variable value according to some physical quantity or parameter. Such a predetermined rotational speed “B” is obtained by empirically or by experiment or simulation, for example, by determining the relationship between the rotational speed of the engine and the inertial force caused by the engine flywheel or the like. Based on the relationship, the engine speed may be set so that the engine speed does not decrease even if the cranking torque is reduced to some extent, and the engine speed is higher than the resonance speed. Note that, from the viewpoint of suppressing the amount of electric power consumed when starting the engine 11, the predetermined rotational speed “B” is desirably relatively small.

  The “second starting torque” is set as a cranking torque that can increase the rotational speed of the engine 11 from a predetermined rotational speed “B” to a rotational speed at which the engine 11 can complete explosion within a predetermined period.

  Here, after the rotation speed Ne of the engine 11 reaches B rpm, the fuel injection execution flag is turned “ON” as shown in FIG. As a result, the ECU 20 controls the fuel injection valve to inject fuel and controls the spark plug 114 to ignite.

  Next, the ECU 20 changes the opening / closing timing of the intake valve 112 at the timing after passing through the resonance band (that is, after the rotational speed of the engine 11 reaches the predetermined rotational speed “B”) (here, the advance angle). Thus, the variable valve mechanism 116 is controlled (see time t3 in FIG. 4), and the second starting torque output from the motor / generator 12 is subtracted and corrected according to the advance amount of the intake valve 112. (Step S106).

  Specifically, for example, the ECU 20 detects the advance amount of the intake valve 112, and the relationship between the detected advance amount and the advance amount of the intake valve 112 and the correction coefficient stored in the ECU 20 in advance. And a cranking torque is corrected by determining a correction coefficient based on the map (see FIG. 3) and multiplying the second starting torque by the determined correction coefficient (see times t3 to t5 in FIG. 4). ).

  Subsequently, the ECU 20 performs a predetermined smoothing process on the torque set in step S106, step S108, which will be described later, or step S109, and outputs the torque subjected to the predetermined smoothing process. Thus, the motor / generator 12 is controlled (step S107). If comprised in this way, generation | occurrence | production of a rapid torque level | step difference can be suppressed. For this reason, for example, it is possible to prevent the driver of the vehicle 1 from feeling uncomfortable due to the torque level difference, or it is possible to prevent the members constituting the power transmission system from being damaged.

  If it is determined in step S103 that the rotational speed Ne of the engine 11 is equal to or higher than C rpm (step S103: Yes), the ECU 20 clears the starting torque (step S108) and executes the process of step S107. To do. Here, in the process of step S107, since the predetermined smoothing process is performed as described above, even if the starting torque is cleared, the cranking torque related to the motor / generator 12 does not immediately become zero, During the predetermined period, cranking torque is output from the motor / generator 12 (see the vicinity of time t4 in FIG. 4).

  As a result of the above, according to the engine starting device 100 according to the present embodiment, the power consumption can be suppressed as compared with the case where the cranking torque is not corrected (see the broken line at the top of FIG. 4). Specifically, it is possible to suppress only the amount of power corresponding to the region a in FIG.

  FIG. 3 is a characteristic diagram showing an example of the relationship between the amount of advancement of the intake valve and the correction coefficient, and FIG. 4 shows the time of each of the torque relating to the motor / generator, the engine speed and the advancement amount of the intake valve. It is a time chart which shows an example of a change.

  The present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the scope or spirit of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 11 ... Engine, 12, 13 ... Motor generator, 14 ... Power distribution mechanism, 15 ... Battery, 16 ... Power control unit, 20 ... ECU, 100 ... Start-up control device, 112 ... Intake valve, 113 ... Exhaust Valve 116: Variable valve mechanism

Claims (1)

An engine having a variable valve mechanism, a rotating electrical machine connected to the engine, and the rotating electrical machine are controlled so as to crank the engine when the engine is started. And a control means for controlling the rotating electrical machine so as to continue cranking of the engine afterwards,
When the control means controls the variable valve mechanism so as to change the intake air amount of the engine during the start of the engine, the control valve controls the advance amount of the intake valve of the engine caused by the variable valve mechanism. In response, the engine starter further comprises torque reducing means for reducing the cranking torque related to the rotating electrical machine.

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