JP2009063001A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device for controlling automatic stop and restart of an engine of a vehicle for reducing fuel consumption which provides an excellent driving feeling and avoids wasteful fuel consumption by suppressing frequent repetition of stop and restart of the engine wastefully. <P>SOLUTION: When the vehicle is in a decelerating state, fuel cut is executed to avoid wasting fuel while the rotation of the engine 1 is maintained by coupling a crankshaft 2 with an axle 11 by a lockup clutch 16 and the like. When a brake stepping amount thereafter is equal to or larger than a first predetermined value S1, it is estimated that the driver intends to stop the vehicle and a quick stop process of the engine rotation is executed except for the case of heavy braking. When the brake stepping amount during this process or after rotation stop decreases to equal to or smaller than a second predetermined value S2, it is estimated that the driver has intention for reacceleration of the vehicle, and fuel supply is resumed, a starter 7 is actuated and the engine 1 is rotated equal to or faster than a predetermined engine speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine (engine) for a vehicle, and particularly can automatically stop an operating engine when it is not necessary to drive the engine. The present invention relates to a vehicle engine control device that can be restarted.

  In a vehicle using an engine as a driving power source, a lock-up clutch provided in the torque converter of the automatic transmission is engaged during deceleration when the vehicle speed is gradually decreasing because the driver does not step on the accelerator pedal. For example, Japanese Patent Application Laid-Open No. 58-166165 discloses a technique for directly connecting the crankshaft of the engine and the transmission of the automatic transmission device and saving fuel consumption by stopping the supply of fuel to the engine. As described in the publication, it is conventionally known. In the conventional system, when the engine speed is reduced to a predetermined value higher than the idle speed in such a fuel cut state, the lock-up clutch is released and the fuel is released to prevent engine stall. It is customary to actuate the supply again.

  In order to further reduce the fuel consumption as compared with the prior art, the resumption of fuel supply is prohibited unless the driver re-accelerates, and the engine is restarted by the automatic starter during the re-acceleration. The idle rotation that consumes fuel may be avoided as much as possible. As an approach close to this idea, in the engine stop control device described in JP-A-11-257115, the brake operation by the driver is performed after the fuel supply is stopped when the vehicle is decelerated. In the meantime, the fuel supply is saved by prohibiting resumption of fuel supply.

  However, when such a method is taken, the engine will stop even if the brakes are stepped lightly, for example, to take a safe inter-vehicle distance from other vehicles ahead at low vehicle speeds. When the accelerator pedal is depressed again to start steady running, the starting device operates to start the stopped engine. In this way, every time the accelerator pedal is depressed after lightly depressing the brake, useless engine stop and restart by the starter are repeated against the driver's intention, which is extremely troublesome for the vehicle occupants including the driver. As a result, not only does the ride feel worse, but the vibration and noise generated at the time of restart and the power consumption of the starter motor cannot be ignored.

  The present invention addresses the above-mentioned problems in the prior art, and does not stop the engine when the brake is lightly depressed, and suppresses frequent repeated engine stop and restart, An object of the present invention is to provide an engine control device that can provide an excellent driving feeling but can avoid waste of fuel.

  The present invention provides an engine control apparatus according to claim 1 as means for solving the above-mentioned problems.

  In the engine control apparatus of the present invention, the engine automatic stop / restart control means is operated when a predetermined condition is satisfied, and the traveling engine mounted on the vehicle is automatically stopped. The predetermined condition here basically means that the deceleration state of the vehicle is detected by the deceleration state detection means, and the brake depression amount by the brake depression amount determination means is larger than the first predetermined value. It is judged that. When these two conditions are met at the same time, the driver (including the autopilot) is expected to stop the vehicle, so the engine is automatically stopped before the actual operation is performed. Let On the contrary, before the engine speed decreases to zero, the brake depression amount is determined by the brake depression amount determination means so that the brake depression amount is equal to or smaller than the first predetermined value. If it is determined that the value is less than the value, the engine is restarted.

  This significantly reduces the number of times the engine is automatically stopped and restarted while avoiding waste of fuel, thus improving the driving feeling and, as in the prior art described above, the driver can re-accelerate before reacceleration. In addition to solving problems such as the engine stopping when the brake is tapped lightly, or the trouble that the engine stop and restart are frequently repeated is troublesome, it is after the engine rotation stop processing is performed. In this case, the driver's intention to stop the vehicle may change and the vehicle may be accelerated again.

  In the engine control device according to the present invention, before the engine speed decreases to zero, the brake depression amount is determined by the brake depression amount determination means so that the brake depression amount is equal to or less than the first predetermined value. If it is determined that the engine speed is equal to or lower than the second predetermined value, the fuel supply is resumed without driving the starter and the engine speed is equal to or lower than the predetermined value when the engine speed is equal to or higher than the predetermined value. If it descends, the starter is driven to restart the engine.

  FIG. 1 shows, as a first embodiment of the present invention, a drive apparatus and a system configuration of the control apparatus of a vehicle equipped with an engine control apparatus. The system configuration shown in FIG. 1 can be applied almost as it is to the second embodiment described later. In FIG. 1, 1 is an engine body, 2 is a crankshaft of the engine 1, 3 is a crank pulley attached to one end of the crankshaft 2, 4 is a generator such as an alternator driven by the crankshaft 2, and 5 is power generation. A battery charged by the electric power generated by the machine 4, a compressor for an air conditioner driven by the engine 1, and a starter motor (starter) 7 provided as a part of the automatic starter of the engine 1. .

  In the case of the first embodiment shown in FIGS. 1 to 7, a crank pulley 3 that is directly connected to the crankshaft 2 and serves as a driving side, and a generator 4 that is shown as a representative of auxiliary devices that are driven and In addition to the pulley of the air conditioner compressor 6, the pulleys attached to the drive shaft of the starter 7 are all interlocked by a single belt 8, and the plurality of pulleys and the single belt 8 are A power transmission mechanism 9 that is always engaged and has some flexibility is configured. The belt 8 of the power transmission mechanism 9 can be replaced with a chain or the like that is a functionally equivalent transmission component. In addition, the starter 7 in this case may be used as a generator.

  Reference numeral 10 denotes left and right drive wheels of the vehicle, 11 denotes left and right axles connected to them, and 12 denotes an automatic transmission device provided in a main power transmission system from the crankshaft 2 to the drive wheels 10 of the engine 1. ing. The structure of the automatic transmission 12 is well known, and a hydraulic torque converter 13 in which a pump and a turbine are opposed to a portion for receiving power from the crankshaft 2 of the engine 1, and Subsequently, a transmission 14 including a plurality of gear trains, hydraulic clutches, and the like, and in this case, a final reduction gear 15 including a differential gear train is provided.

  The automatic transmission device 12 is a lock that is a direct transmission means that directly mechanically transmits power by short-circuiting the torque converter 13 so that the power loss due to the fluid of the torque converter 13 is reduced in a high-speed steady running state or the like. An up clutch 16 is provided in parallel with the torque converter 13. The transmission 14 can be arbitrarily controlled to a neutral state by a transmission device control means described later.

  The automatic transmission 12 in the present invention is not limited to the one provided with the fluid torque converter 13 as illustrated in FIG. 1, but the transmission state between the crankshaft of the engine and the drive wheels is electronic. Any automatic transmission device configured to be able to control at least two states, that is, a direct connection state and a state in which torque transmitted from the drive wheel in the direction of the crankshaft is interrupted by a typical control means. . Therefore, for example, in the automatic transmission 12 having a built-in transmission that is always engaged, a control clutch such as an electromagnetic clutch that can be controlled by electronic control means is provided after the one corresponding to the transmission 14 or after. It is connected in series before, and the transmission state between the crankshaft 2 of the engine and the drive wheel 10 is controlled to be directly connected or disconnected by this clutch.

  Reference numeral 17 shown in FIG. 1 is an electronic control unit (ECU) for automatic engine stop / restart that transmits a command for automatically stopping or restarting the engine 1, and this control unit 17 is also similar to a normal ECU. Further, it comprises at least one microprocessor, memories such as ROM and RAM connected thereto, a clock device, and an input / output port. A command for causing a function specific to the present invention is formed by a calculation performed based on a signal input to the control device 17 from a detection unit such as a sensor or a switch, a map set in the ROM, and the like. . For this purpose, the control device 17 receives signals indicating the operating states of the engine 1 and the vehicle from several detection means provided in each part of the vehicle and the engine 1, and a large number of calculation result commands (control signals) are related. It is output toward the control means which is an individual driving device of the device.

  In the system illustrated in FIG. 1, reference numeral 18 denotes control means for the automatic transmission 12 as one of control means for driving a target device in response to a command from the control device 17. The control means 18 controls the automatic transmission 12 by issuing a command to the hydraulic control mechanism 35. In the same way as a normal one, the gear train of the transmission 14 is switched by operating a hydraulic clutch or the like inside the transmission device 12, and a command from the control device 17 is accepted at any time to lock the direct transmission mechanism. The up-clutch 16 can be controlled intermittently and has a built-in control means for the direct transmission means. This control means is a means for intermittently connecting the above-described series-connected control clutch. Reference numeral 19 denotes a normal engine ECU and control means (E / G-ECU) of the engine main body 1 such as a drive device that operates according to its command. Reference numeral 20 denotes a control means for a starter motor (starter) 7. When the power of the battery 5 is supplied to the starter 7 by its operation, the starter 7 is an engine even if the engine 1 is not completely stopped. One crankshaft 2 can be driven to perform a restart operation. The starter control means 20 constitutes an automatic starter together with a starter motor (starter) 7.

  A block 21 in FIG. 1 represents a control means for controlling the amount of power generated by the generator 4. Thus, when the power generation amount of the power generator 4 is controlled to increase the power generation amount, the power generator 4 becomes a brake and can suppress the rotation of the crankshaft 2 via the belt 8. Moreover, since the compressor 6 for an air conditioner can be used as a direct brake for the crankshaft 2, the compressor 6 is temporarily operated even when the air conditioner is not required. Control means 22 for increasing the mechanical load and increasing the power consumption of the compressor 6 is provided. By these control means, the load acting on the crankshaft 2 of the engine 1 can be temporarily increased.

  FIG. 1 also illustrates several detection means for detecting and inputting signals indicating the operating states of the engine 1 and the vehicle necessary for the control device 17 to perform such control to the control device 17. ing. First, reference numeral 23 denotes acceleration / deceleration detecting means for detecting the acceleration and deceleration of the vehicle, but it is not necessary to provide a dedicated sensor or the like, and a normal vehicle speed sensor for measuring the rotation speed (rotational speed) of the axle 11 or the like. Since the acceleration or deceleration of the vehicle can be obtained by calculating the signal in the control device 17, a part of the vehicle speed sensor and the control device 17 serves as the acceleration / deceleration detecting means 23.

  Reference numeral 24 denotes brake depression amount detection means for detecting the depression amount of a brake pedal (not shown) operated by a vehicle driver (brake stroke or brake depression angle, and in some cases, the magnitude of the depression force of the brake). It may be something like a potentiometer (variable resistor) attached to the rotating shaft of the brake pedal. Further, the brake depression speed can be calculated by differentiating the signal with respect to time in the control device 17. Reference numeral 25 denotes a means for detecting the amount of depression of the accelerator pedal (accelerator opening) by the driver. In the first embodiment, it is not necessary to accurately detect the amount of depression of the accelerator pedal, and it is sufficient to detect whether or not the amount of depression of the accelerator pedal exceeds a predetermined value. Therefore, the detecting means 25 is a switch linked to the accelerator pedal. That is, it can be an accelerator switch.

  Reference numeral 26 denotes a steering angle detecting means for detecting the steering angle of a steering wheel (not shown) that is operated and rotated by the driver, but it is not necessary to accurately detect the steering angle, either one of left and right Since it is sufficient to generate a signal when the steering angle of the direction exceeds a predetermined value, a switch that is turned on when the steering shaft rotates by a predetermined angle is provided in the steering column, and this is applied. be able to. Reference numeral 27 denotes a means for detecting the operation of the direction indicator, which can use a pair of left and right turn signal switches operated by the driver to blink the direction indicator. That is, it is only necessary to connect so that an electrical signal is input to the control device 17 when any of the left and right turn signal switches 27 is turned on.

  Reference numeral 28 denotes road surface inclination angle detecting means 28 for detecting the inclination angle of the road surface on which the vehicle travels. For example, a switch that is turned on when the inclination angle of the pendulum that can be freely rotated exceeds a predetermined value is turned on. It can be used for this purpose by setting it in place. Reference numeral 29 denotes a forward vehicle detecting means, which is preferably capable of not only detecting that there is another vehicle ahead but also measuring the distance between them. For this purpose, for example, a distance measuring device that operates automatically may be attached to the front of the vehicle. A relative speed is calculated by calculating a signal indicating the distance to another vehicle in the control device 17.

  Further, as a detecting means mounted on a normal vehicle and usable for the purpose of the present invention, reference numeral 30 denotes a detecting means for detecting the operating state of the parking brake. Since this may be a switch that is turned on when the parking brake is in the engaged state, this type of switch provided in a normal vehicle may be directly connected to the control device 17 as a sensor. Similarly, 31 is a detecting means 31 for detecting the number of revolutions of the engine 1. For example, if the engine 1 is a spark ignition engine such as a gasoline engine, the number of pulses of the ignition signal generated within a unit time is controlled by the control device. If the count is performed at 17, the rotational speed of the engine 1 is obtained, and the device related to this is the engine rotational speed detection means 31. An electric negative pressure pump 32 communicates with the brake system 34. In order to ensure a negative pressure necessary for operating the brake system 34 while the engine 1 is stopped, the control device 17 performs control. It is driven by the battery 5 below. An electric hydraulic pump 33 communicates with the hydraulic control mechanism 35 and is driven by the battery 5 under the control of the control device 17 in order to ensure the operating hydraulic pressure of the hydraulic control mechanism 35 while the engine 1 is stopped. Is done. When the engine 1 is rotating, the brake system 34 is operated by the intake negative pressure of the engine. The hydraulic pressure of the hydraulic control mechanism 35 is covered by a hydraulic pump (not shown) attached to the crankshaft 2 of the engine 1.

  Although not shown in FIG. 1, even if an event that can be indirectly detected by the above detection means is used as a detection means for directly detecting the event, for example, a lock-up clutch 16 is used. A sensor or the like for directly detecting the intermittent state can be provided as necessary. In the control device of the present invention, control means for intermittently controlling the fuel supply to the engine 1, control means for ON / OFF control of the ignition device, and the like are also required. However, control such as fuel supply cut and fuel supply return performed by these control means is performed by the electronic control unit 17 controlling the normal engine control means 19, so these control means are usually Is included in a part of the engine control means 19.

  Since the engine control apparatus of the first embodiment shown in FIG. 1 has the above-described configuration, the operation of this apparatus will be described below with reference to the main routine control program shown in the flowchart of FIG. This will be described in detail with reference to a time chart showing the state over time. 5 and 6 show a subroutine control program that branches from the main routine program of FIG. 2 that is repeatedly executed every predetermined short time. FIG. 4 shows the case of FIG. Time charts in different operating states are shown. These will also be explained sequentially.

  While the vehicle equipped with the control device of the first embodiment is traveling, the accelerator pedal depression amount (accelerator opening) by the driver becomes 0, and the vehicle enters a deceleration state in which the vehicle speed decreases, and acceleration / deceleration detection means When the detection signal 23 becomes equal to or less than a predetermined negative value, the electronic control unit 17 detects the deceleration state of the vehicle in step 201 based on the signal. Further, in step 202, when it is detected that the accelerator switch 25, which is a means for detecting the depression amount of the accelerator pedal, is OFF and it is confirmed that the accelerator pedal is not depressed, the routine proceeds to step 203. The control device 17 controls the engine control means 19 to instruct the engine body 1 to cut fuel and prohibit fuel return.

  At the same time, the control device 17 controls the transmission control means 18 to turn on the lockup clutch 16 (or the control clutch corresponding thereto as described above, etc.) of the automatic transmission 12 so that the fuel is supplied. The crankshaft 2 of the engine 1 whose supply is cut and no longer generates torque is driven reversely by the drive wheels 10 and the axle 11 to continue to rotate. When the deceleration state is not detected at step 201 or when the accelerator pedal is depressed at step 202, the process returns to step 201 and repeats the determination.

  In step 204, it is determined whether or not the brake depression speed calculated in the control device 17 is equal to or less than a predetermined value based on the detection signal of the brake depression amount detection means 24. If NO (the brake depression speed is equal to or greater than a predetermined value), the brake state is sudden and the process proceeds to a subroutine program (FIG. 5) to be described later. After confirming again that the accelerator switch 25 is OFF (acceleration operation has not been performed), the routine proceeds to step 206 where the rotational speed of the crankshaft 2 detected by the engine rotational speed detection means 31 is a predetermined rotational speed Nlimit. It is determined whether or not it is equal to or greater than the value of. When the accelerator switch 25 is ON in step 205, the process proceeds to step 210, and the lockup clutch 16 is turned OFF (released state). Thereafter, if the engine speed is equal to or greater than Nlimit in the determination at step 211 (YES), the routine proceeds to step 213, where fuel supply is resumed, and the engine is restarted only by that. When the engine speed is equal to or lower than Nlimit (NO) at step 211, the routine proceeds to step 212, where after the starter 7 is driven, the fuel supply is resumed and the engine 1 is restarted. Then, when the engine speed becomes equal to or higher than the predetermined value in step 214, the process proceeds to step 215, and the drive of the starter 7 is stopped.

  Here, Nlimit is a predetermined value having the following meaning. In general, a reciprocating engine passes through a rotational speed region called a resonance region (see FIG. 3) by the time the rotational speed decreases and stops. Large vibrations that are uncomfortable for passengers occur. Nlimit is the number of rotations obtained by adding the maximum number of rotations in this resonance region and the amount of decrease in the engine number of rotation that is expected during the time delay from when the engine stop condition is satisfied until engine stop control is actually started. That's it. When the number of rotations decreases and reaches Nlimit, the vibrations generated in the resonance region can be reduced by performing the control peculiar to the present invention as will be described later to quickly pass the following resonance region.

  If it is determined as YES in step 206 (the rotational speed of the crankshaft 2 has not dropped to Nlimit), the process returns to step 204 and repeats the determination. Deceleration proceeds in the fuel cut state and the rotation speed of the crankshaft 2 also decreases. If NO is determined in step 206 (the rotation speed has passed Nlimit and approaches the resonance range), the driver can If deceleration is continued to stop the vehicle, the linkage between the crankshaft 2 and the axle 11 is cut off, and the engine 1 is stopped quickly to prevent generation of unpleasant vibration due to resonance.

  However, although the vehicle has temporarily decelerated, if the driver is going to continue driving the vehicle, the fuel supply is resumed to increase the engine speed, thereby avoiding vibrations. It is desirable to be prepared to be ready for re-acceleration. Therefore, in the control device 17 of the first embodiment, it is predicted based on the amount of depression of the brake whether the driver intends to stop the vehicle or keeps traveling. It is characterized in that it is set to perform subsequent control according to the prediction.

  That is, in step 207, it is determined whether or not the brake depression amount is equal to or greater than a first predetermined value (in this case, the engine rotation stop threshold S1). The first predetermined value is a value expected to be depressed when the driver stops the vehicle. For example, the first predetermined value is a value capable of braking the creep torque generated when the accelerator pedal is not depressed. Is set. If YES (predetermined value or more), it is predicted that the driver is going to stop the vehicle and the process proceeds to step 208. By that time, by another subroutine program (FIG. 6) described later, Reference is made to an engine rotation stop permission flag FNStop set by making a determination on a predetermined item in advance. If the permission flag is 1, there is no problem even if the engine is stopped in this state and the vehicle is further stopped. This is also a subroutine program for engine rotation stop processing described later (FIG. 7). To stop the engine 1 quickly. The engine rotation stop process corresponds to the engine automatic stop according to the present invention.

  In step 209 after the rotation stop process of the engine 1 is performed, it is determined whether or not the brake depression amount is equal to or less than a second predetermined value (in this case, the engine restart threshold S1). The second predetermined value S2 is set as a value that is the same as or smaller than the first predetermined value S1. If the determination is NO (the brake depression amount is equal to or greater than the second predetermined value S2), the driver has not changed his / her intention to stop even after the engine 1 has been stopped. Returning to 208, the determination and the engine rotation stop process are intermittently performed to stop the engine 1 completely or to maintain the stopped state. Such an operation is indicated by a solid line in the time chart of FIG. Here, for example, when the control device 17 confirms the parking state by the operation state detecting means 30 of the parking brake, the control device 17 performs control such as automatic fuel return and restart even if the brake depression amount decreases thereafter. Do not do.

  Unlike this, of course, the accelerator switch 25 is ON in step 205, that is, the driver is stepping on the accelerator pedal. However, in the determination of step 207, the brake depression amount is the first predetermined value. When S1 or less (NO), it is considered that the driver's intention has shifted from the stop of the vehicle to the continuation of travel or re-acceleration. Even if the determination in step 209 after performing the engine rotation stop processing is YES (the brake depression amount is equal to or less than the second predetermined value S2), the driver's intention to stop the vehicle changes, It is thought that it accelerated again. Therefore, in the control shown in FIG. 2 of the control device 17 of the first embodiment, in any case where re-acceleration is predicted, fuel is supplied again to the engine 1 and restarted to increase the rotational speed. Then proceed to steps A to B. If the determination in step 209 is YES and the process proceeds to step 210 before the engine speed decreases to zero, the load on the auxiliary machine is reduced as described later by the engine rotation stop process performed prior to that. Remains large, so the load on the auxiliary machine is returned to the normal state in step 216.

  In step 210, the control device 17 immediately turns off the lockup clutch 16 (or an alternative means) via the transmission control means 18, stops the rotation of the crankshaft 2 by the axle 11, and the crankshaft 2 is turned on. Be able to rotate freely. At the same time, the control of the transmission 14 of the automatic transmission 12 by the transmission control means 18 is also returned to the normal control mode. In step 211, it is determined whether or not the engine speed at that time is larger than a predetermined value Nlimit. When it is not large (NO), the control device 17 activates the starter 7 by the starter control means 20 in step 212 and rotationally drives the crankshaft 2 via the belt 8, and supplies the fuel by the engine control means 19 in step 213. Is restarted to restart the engine 1. Such an operation is also indicated by a solid line in FIG. If the engine speed is equal to or higher than Nlimit (YES) in step 211, the engine 1 is restarted only by restarting the fuel supply without driving the starter 7. This operation is the same as that shown in the time chart of FIG.

  The operation indicated by the broken line in FIG. 3 shows a case where the driver's intention is changed to re-acceleration as described above when the engine speed falls below the predetermined value Nlimit before the engine speed reaches zero. . The intention of reacceleration is predicted by the control device 17 when the brake depression amount is reduced before the driver actually depresses the accelerator pedal. By starting preparation for reacceleration at that time, reacceleration can be executed quickly and in a highly responsive state.

  In the control device 17 of the first embodiment, the starter 7 is driven when reacceleration is predicted, not only when the rotation speed of the crankshaft 2 becomes zero, but also when the rotation speed of the crankshaft 2 is Nlimit or less. And restart control. There is a slight time delay from the time when the control device 17 starts the restart control until the starter 7 actually starts to rotate, but Nlimit is slightly larger than the maximum rotational speed in the resonance region. When the rotation speed of the crankshaft 2 falls to the resonance range, the rotation speed starts to increase again by the starter 7, so that unpleasant vibration due to resonance can be avoided. Thus, in order to start the restart before the engine 1 is completely stopped, the rotation shaft of the starter 7 is connected to the crankshaft 2 through the power transmission mechanism 9 so as to be always driven.

  The re-acceleration of the vehicle in the above description is a case where the control device 17 predicts that the driver is about to stop the vehicle when the brake depression amount is equal to or greater than the first predetermined value S1, and The accelerator pedal is operated by the driver after the rotation speed of the crankshaft 2 of the engine 1 becomes completely zero, or when the driver's intention changes to reacceleration while the rotation speed is decreasing below Nlimit. The engine 1 is restarted when reacceleration is predicted from the brake depression amount before the engine is depressed, and the rotation speed of the crankshaft 2 is increased to respond quickly to the reacceleration operation. According to the control performed by the control device 17 of the first embodiment when the brake depression amount of the driver is equal to or less than the first predetermined value S1. Each part of the operating state is shown in the time chart of FIG.

  As shown in FIG. 4, even when the vehicle is decelerating, if the amount of brake depression by the driver is equal to or less than the first predetermined value S1, the control device 17 does not intend the driver to stop the vehicle. It is predicted that re-acceleration will be performed. In this case as well, the vehicle deceleration state is detected by the signal from the vehicle acceleration / deceleration detecting means 23 in step 201 of the flowchart shown in FIG. 2, and the accelerator switch 25 is turned off in step 202 (accelerator pedal). When it is detected that the accelerator opening, which is the amount of depression of the vehicle, is 0), the fuel cut and the lockup clutch 16 are engaged, whereby the vehicle speed and the engine speed are gradually decreasing. When the control device 17 detects from the signal of the brake depression amount detection means 24 that the brake depression amount is smaller than the first predetermined value S1, the lock-up clutch 16 is turned on when the engine speed decreases to Nlimit. Is turned off (released) and the fuel supply is resumed.

  Thus, when reacceleration is predicted by the amount of brake depression, the lockup clutch 16 is released and the fuel is returned before the engine speed decreases so as to enter the resonance range, and the engine speed is increased. Is maintained at at least Nlimit, for example, at idling speed. Thereby, while avoiding waste of fuel, generation of unpleasant vibrations can be prevented, and further, when the reacceleration operation is performed, the engine speed can be immediately increased in response quickly. In this case, since the engine speed has not decreased so much, the restart operation by the starter 7 in step 212 is unnecessary.

  Here, there are three matters postponed in the description of the flowchart of FIG. 2 showing the control routine program of the control device 17 of the first embodiment, that is, the engine stall that shifts when YES is determined in step 204. The details of the prevention processing, the setting of the engine rotation stop permission flag FNStop referred to in the determination in step 208, and the details of the engine rotation stop processing executed when it is 1 will be described in order.

  First, a case where a determination of NO (the brake depression speed is equal to or greater than a predetermined value) is made in step 204 of FIG. 2, that is, a case where the driver suddenly applied the brake will be described. As described above, the control device 17 of the first embodiment makes the fuel cut in the deceleration state of the vehicle and engages the lockup clutch 16 to interlock the crankshaft 2 and the drive wheel 10. When sudden braking is applied in this state, the rotational speed of the crankshaft 2 together with the drive wheels 10 is rapidly reduced, and engine stall is likely to occur. Therefore, in this case, the process proceeds to a subroutine program as shown in FIG. 5, and the control device 17 performs special control.

  That is, since the brake depression speed is high, when the control device 17 of the first embodiment shifts to the engine stall prevention process shown in FIG. 5, first, the vehicle deceleration detected from the signal of the acceleration / deceleration detecting means 23 in step 501. It is determined whether the absolute value of is greater than a predetermined value. When the deceleration is larger than the predetermined value (YES), the routine proceeds to step 502 where the lockup clutch 16 is released and the fuel supply is restarted by the engine control means 19. Further, the routine proceeds to step 503, where the starter control means 20 drives the starter 7, rotates the crankshaft 2, and performs a restarting operation. Accordingly, it is determined in step 504 whether or not the rotational speed of the engine 1 has recovered to a predetermined value or more. If the rotational speed has not recovered (NO), the determination is repeated. When the engine speed has recovered to a predetermined value or higher (YES), the routine proceeds to step 505, the drive of the starter 7 is stopped, and the routine returns to the main routine program of FIG. However, the starter 7 does not perform substantial work when the engine speed is still sufficiently high when such control is performed and the determination in step 504 is YES from the beginning. Since the control device 17 of the first embodiment performs such control, it is possible to reliably prevent engine stall even in a sudden braking state.

  Next, a subroutine program for setting the engine rotation stop permission flag FNStop referred to in step 208 of the flowchart shown in FIG. 2 will be described with reference to FIG. The program shown in FIG. 6 is executed by the control device 17 by interrupting at a predetermined short time interval before step 208 of the main routine program. When this program is executed, the control device 17 first determines in step 601 whether or not any of the left and right turn signal switches 27 serving as detection means for the operation of the direction indicator is ON. When it is not ON, the routine proceeds to step 602, where it is determined whether or not the driver is operating the steering wheel depending on whether or not the signal of the steering angle detection means 26 exists.

  If this is also NO (not operated), the routine proceeds to step 603, where it is determined whether or not the vehicle is on an uphill with reference to the signal from the road surface inclination angle detecting means 28. If this is also NO (inclination angle is equal to or less than a predetermined value), the process proceeds to step 604 to determine whether or not there is another vehicle within a predetermined distance ahead by the signal from the forward vehicle detection means 29. . When this is also NO (does not exist), the routine proceeds to step 605, where the permission flag FNeStop is set to 1. In other words, when the vehicle is changing its direction of travel, or when it is approaching a large uphill, the vehicle needs to leave sufficient freedom of maneuvering. This is because there is a risk of danger. Also, even if it is done automatically, it can be annoying to the driver if the engine is repeatedly stopped and restarted frequently in a traffic jam, so the engine rotation only occurs when there is no problem of concern. The stop permission flag FNeStop is set to 1.

  Therefore, even if the condition that the vehicle is decelerating and the accelerator opening is zero is satisfied, if the determination result in any one of steps 601 to 603 is YES, that is, the vehicle is traveling. If the direction is being changed or if it is approaching a large uphill, the process proceeds to step 607 in FIG. 6 for safety, and the permission flag FNeStop is set to 0 to prohibit the engine rotation from stopping. If the determination in step 604 is YES, there is another vehicle near the front, but in this case, the control device 17 performs the determination in step 606 without uniformly setting the permission flag FNStop to 0. The relative speed with the other vehicle is calculated based on the distance between the other vehicle in front and the own traveling speed, etc., and the relative speed is higher than the predetermined speed, and the vehicle is accelerated following the preceding vehicle. If it is predicted (YES), the process proceeds to step 607 and exceptionally the permission flag FNStop is set to 0. Therefore, in this case, only when the relative speed is lower than the predetermined speed (NO), such as the other vehicle in front is stopped due to a red signal, this vehicle also stops following the preceding vehicle. In anticipation of this, the process proceeds to step 605 to set the permission flag FNeStop to 1. In this way, unnecessary engine stops are reduced to reduce driver discomfort.

  Further, in the determination of step 208 shown in FIG. 2, when the engine rotation stop permission flag FNStop is 1 (YES), the engine rotation is stopped. Therefore, the rotation stop of the engine 1 is executed in the following steps. However, the engine rotation stopping process is also shown in detail as one subroutine program in FIG. When the control device 17 enters the rotation stop control of the engine 1, first, at step 701, it is determined whether or not the rotation speed of the engine 1 is currently zero. Since the determination is NO while the engine 1 is rotating even a little, the process proceeds to the next step 702 where the engaged lock-up clutch 16 is disengaged (OFF) and the transmission 14 is in the neutral state. As a result, the linkage between the crankshaft 2 and the axle 11 is cut off.

  Next, the routine proceeds to step 703, where the load on the auxiliary machine is set as large as possible. This is because the crankshaft 2 is stopped quickly by increasing the load of the engine 1 as much as possible, thereby allowing the above-described resonance region to pass within a short time and suppressing the occurrence of unpleasant vibrations. As a representative of the auxiliary machine, FIG. 1 shows a compressor 6 for an air conditioner. Therefore, in this case, even when it is not necessary to use the air conditioner, the control device 17 temporarily operates the compressor 6 by the compressor load control means 22 and increases the mechanical load to cause the compressor 6 to move to the crankshaft 2. Brake. For the same purpose, the generator load control means 21 is operated, for example, the power generation amount of the generator 4 is increased, and the mechanical load is temporarily increased, thereby causing the generator 4 to brake the crankshaft 2. Use as

  In step 703, any means that are useful for stopping the engine rotation are activated in addition to the means that are already running. For example, a special braking device may be provided on the crankshaft 2 of the engine 1 and may be operated for a short time by the control device 17 at this time. In this way, the engine rotation stop process is executed, so that the crankshaft 2 is quickly stopped, and unpleasant vibrations are suppressed during that time. If it is determined in step 701 that the engine 1 has stopped (YES), the process proceeds to step 704, where the temporarily increased load on the auxiliary machine is removed, and the normal control state is restored, and then the process returns to the main routine program. . Further, in this embodiment, the electric negative pressure pump 32 and the electric hydraulic pump 33 are driven by the battery 5 in accordance with a command from the control device 17 during the automatic stop of the engine 1, and the size required for the operation of the brake system. The negative pressure and the hydraulic pressure required for the operation of the hydraulic control mechanism 35 can be ensured. Thereby, each can be appropriately operated even when the engine 1 is stopped.

  As described above, the automatic stop / restart control device of the present invention basically performs fuel cut in the deceleration state of the vehicle to avoid wasting fuel and connects the crankshaft and axle of the engine to The engine rotation is maintained by rotating the axle until shortly before it completely stops. In this case, in the automatic stop / restart control device of the first embodiment described above, except when the brake is depressed suddenly with a high brake depression speed when the brake depression amount by the driver is equal to or greater than the first predetermined value S1, It is predicted that the driver will stop the vehicle, and the engine rotation is quickly stopped. In the process, or when the amount of brake depression decreases after the rotation stops and becomes less than or equal to the second predetermined value S2, the fuel supply is resumed assuming that the driver will re-accelerate the vehicle, The restraint of the crankshaft by the axle is released, the starter is operated, and the engine is rotated at a predetermined rotational speed or more. Even if the fuel cut is performed at the time of deceleration, it is predicted that re-acceleration will be performed if the amount of brake depression from the beginning is equal to or less than the first predetermined value S1, and the engine speed reaches the resonance range. The fuel supply is resumed before the descent, and the crankshaft is restrained by the axle. Do not operate the starter at this time.

  Next, a second embodiment of the automatic stop / restart control system for an engine according to the present invention will be described with reference to FIGS. The control device of the second embodiment is characterized in that the control procedure is partially different from that of the first embodiment. In the main routine program of the first embodiment shown in FIG. 2, the same processing is executed by the control device 17 in the second embodiment for the processing from step 201 to step 210. The entire system configuration shown in FIG. 1 can also be used as it is. In order to show the characteristic features of the control of the second embodiment, FIG. 8 shows a process of the second embodiment that replaces the process between the portions A and B of the flowchart shown in FIG. Step 810 itself is the same as step 210 in FIG. 2, and steps 813 and 814 are also the same as steps 212 and 213 in FIG. 2, respectively.

  In step 209 shown in FIG. 2, it is determined whether or not the brake depression amount is equal to or less than a second predetermined value S2, and if YES (the brake depression amount is equal to or less than the second predetermined value S2), the control is performed. The device 17 predicts that the driver's intention to stop the vehicle will change and re-accelerate. Then, the process proceeds from step A to step B, the lockup clutch 16 is released in step 210, and the transmission 14 of the automatic transmission 12 is returned to the normal control. This point is also in step 810 in the second embodiment. Similar processing is performed. Thereafter, fuel is supplied again to the engine 1 to increase the rotational speed of the crankshaft 2. At this time, in the first embodiment, the starter 7 is operated if the rotational speed of the engine is equal to or less than a predetermined value Nlimit.

  On the other hand, in the control device 17 of the second embodiment, first, in step 811, a predetermined value Ncrank is set. Ncrank is a threshold value for determining whether or not to operate the starter 7 based on the engine speed when re-acceleration is predicted and fuel supply is resumed. Ncrank is mapped in advance as shown in the diagram of FIG. 9 using parameters such as the engine speed reduction speed and the cooling water temperature as parameters, and is built in the ROM in the control device 17. Therefore, in the case of FIG. 9, the Ncrank value is determined by giving the speed of decrease of the engine speed and the cooling water temperature at that time. When returning the engine from the fuel supply stop state to the operating state, depending on the load state and warm-up state of the engine, even if the starter is not used, the supply of the fuel is resumed, and the engine is caused by the rotational inertia force of the crankshaft. Often it can be started. Therefore, Ncrank indicates the maximum speed at which the engine can be started without using a starter under each load condition or warm-up condition. In step 812 of FIG. 8, it is determined whether or not the engine speed at that time is larger than the selected value of Ncrank. When it is not large (NO), the starter 7 is operated in step 813, but when it is large (YES), the starter 7 is not operated. Thereby, the frequency | count of operating the starter 7 can be reduced. Thereafter, in either case, the process proceeds to step 814 to restart the fuel supply.

  A time chart of control by the control device 17 of the second embodiment is shown in FIG. In the second embodiment, the fuel cut and the lock-up clutch 16 are engaged when the accelerator opening is zero and the vehicle is decelerated, as in the first embodiment. Without the driver operating the brake at all, the vehicle speed naturally decreases and the engine speed also decreases, and when the driver approaches the Nlimit before entering the resonance range, the driver depresses the accelerator pedal. Whether or not to use the starter 7 by comparing the current rotation speed of the engine 1 with a predetermined value Ncrank when restarting the engine 1 in response to a clear intention to re-accelerate It is characterized in that it is determined.

  That is, if the speed of the engine 1 when the driver depresses the accelerator pedal and the accelerator opening is larger than Ncrank, the fuel supply is simply resumed and the lockup clutch 16 is disengaged. However, as shown by the broken line diagram in FIG. 10, when the rotational speed of the engine 1 has decreased to N crank or less, the starter 7 is operated to restart and reaccelerate. There is a feature. Needless to say, in order to perform such an operation, it is assumed that the starter 7 can always drive the crankshaft 2 and can be restarted while the crankshaft 2 is rotating. become. Note that the determination is not limited to the example of the time chart shown in FIG. 10, and the same determination is made when the fuel supply is stopped from the stopped state.

1 is a system configuration diagram illustrating an automatic stop / restart control apparatus according to an embodiment of the present invention. It is a flowchart of the main routine program which shows the control action of the control apparatus of 1st Example. It is a time chart which illustrates one control mode of the 1st example. It is a time chart which illustrates other control modes of the 1st example. It is a flowchart which shows the subroutine program for the engine stall prevention process branched from the main routine program of FIG. It is a flowchart which shows the subroutine program for setting the flag in the main routine program of FIG. It is a flowchart which shows the subroutine program for the engine rotation stop process in the main routine program of FIG. It is a flowchart which shows the control program of the control apparatus of 2nd Example. It is a diagram which illustrates the content of the map used when setting the predetermined value for determining whether the motor for starting is used in 2nd Example. It is a time chart which illustrates one control mode of the 2nd example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine body 2 ... Crankshaft 4 ... Generator 5 ... Battery 6 ... Air-conditioner compressor 7 ... Motor for starter (starter)
DESCRIPTION OF SYMBOLS 8 ... Belt 9 ... Power transmission mechanism 10 ... Driving wheel 11 ... Axle 12 ... Automatic transmission 13: Torque converter 14 ... Transmission 16 ... Lock-up clutch 17 ... Electronic control unit 18 ... Transmission control means 19 ... Engine control Means 20: Starter control means 21 ... Generator load control means 22 ... Compressor load control means 23 ... Acceleration / deceleration detection means 24 ... Brake depression amount detection means 25 ... Accelerator pedal depression amount detection means (accelerator switch)
26 ... Steering angle detection means 27 ... Detection means for operation of direction indicator (blinker switch)
DESCRIPTION OF SYMBOLS 28 ... Road surface inclination angle detection means 29 ... Forward vehicle detection means 30 ... Parking brake operation state detection means 31 ... Engine speed detection means 32 ... Electric negative pressure pump 33 ... Electric hydraulic pump 34 ... Brake system 35 ... Automatic transmission transmission Hydraulic control mechanism of equipment

Claims (3)

An engine automatic stop / restart control means for automatically stopping a traveling engine mounted on a vehicle when a predetermined condition is satisfied;
Brake depression amount detection means for detecting the depression amount of a brake provided in the vehicle;
Brake depression amount determining means for determining whether or not the detected brake depression amount is greater than a first predetermined value;
A deceleration state detecting means for detecting a deceleration state of the vehicle,
The engine automatic stop / restart control is performed when the deceleration state of the vehicle is detected by the deceleration state detection unit and when the brake depression amount is determined by the brake depression amount determination unit to be greater than or equal to the first predetermined value. Means automatically stop the engine,
Before the engine speed decreases to zero, the brake depression amount determining means causes the brake depression amount to be equal to or less than a second predetermined value that is equal to or smaller than the first predetermined value. An engine control device that restarts the engine when it is determined that the engine is present.   2. The engine control device according to claim 1, wherein the brake depression amount is equal to or more than the first predetermined value by the brake depression amount determination unit before the engine speed decreases to zero. If it is determined that the engine speed is less than or equal to the second predetermined value, which is a small value, the fuel supply is resumed without driving the starter if the engine speed is greater than or equal to the predetermined value, and the speed is predetermined. An engine control device characterized by restarting the engine by driving a starter when it falls below the value.   The engine control device according to claim 2, wherein the predetermined value of the engine speed is the maximum engine speed in a resonance region and until the engine stop control is actually started after the engine stop condition is satisfied. An engine control device characterized in that the engine speed is a sum of a decrease amount of the engine speed expected during the time delay.

Images