JP2008014238A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit drop of braking performance when engine speed is high such as a case of execution of fast idling. <P>SOLUTION: ECU 100 executes an idling speed establishing process on a vehicle 10. In the idling speed establishing process, target idling speed is dropped from an original target value Ne1 relating to fast idling control to Ne0 when fast idling conditions discriminated based on engine cooling water temperature, outside air temperature and the like are satisfied and idling speed drop conditions provided by vehicle speed, shift range of ECT11B, and operation conditions of an accelerator pedal 20 and a brake pedal 22, to inhibit deterioration of braking performance due to increase of driving force during braking by fast idling control. Idling speed is gradually changed to the target value Ne1 to accelerate warming-up of an engine 200 when predetermined time passes after vehicle stop. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a technical field of a control device for an internal combustion engine capable of suppressing deterioration in braking performance of a vehicle.

  As a technique having this type of effect, a technique for shortening the braking distance has been proposed (see, for example, Patent Document 1). According to the anti-skid control device disclosed in Patent Document 1 (hereinafter referred to as “conventional technology”), when the engine speed is higher than usual and the vehicle is traveling on a low μ road, anti-skid control is performed. It is said that the braking distance can be shortened by prohibiting and performing normal braking.

  In addition, a technique has been proposed in which, when sudden braking is performed in a vehicle equipped with ABS, the engine braking effect is maximized by downshifting and the braking distance is shortened (see, for example, Patent Document 2).

JP-A-6-40320 JP 9-166214 A

  For example, when a vehicle is braked, the required braking force differs between the driving wheel and the non-driving wheel, so that if the driving wheel is stopped, the non-driving wheel tends to fall into a locked state. When it is necessary to continue to apply braking force to the driving wheels even when the non-driving wheels are locked, for example, in an FR (Frontengine Reardrive) vehicle, the vehicle is pushed forward. The braking performance at is likely to be lowered. Such a problem becomes more prominent as the engine speed is higher.

  On the other hand, at the time of braking of the vehicle, the engine speed can be reduced with the idle speed as a lower limit, but such a problem occurs in the same way even during anti-skid control or during normal braking. When the idling speed is set to be relatively high, there is a possibility that the braking distance is extended and the safety is lowered when the braking mode is changed as in the prior art. That is, the conventional technique has a technical problem that it is difficult to suppress deterioration of the braking performance of the vehicle in some cases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can suppress deterioration in braking performance when the engine speed of the internal combustion engine is high.

  In order to solve the above-described problem, an internal combustion engine control apparatus according to the present invention is an idle rotation speed variable capable of changing an idle rotation speed by changing an intake air amount related to air sucked into a cylinder. A control device for an internal combustion engine for controlling the internal combustion engine in a vehicle including the internal combustion engine having a means, wherein the target value of the idle speed is a provisional value less than a reference value in at least a part of the braking period of the vehicle. And setting means for setting the reference value in a period excluding at least a part of the braking period, and controlling the idle speed changing means so that the idle speed becomes the set target value. And a control means.

  The “internal combustion engine” in the present invention has, for example, a plurality of cylinders, and the explosive force generated when various fuels such as gasoline, light oil or alcohol burn in each combustion chamber, for example, pistons, connecting parts, etc. It is a concept that encompasses an engine that can be extracted as power through a rod, a crankshaft, and the like as appropriate, and refers to, for example, a two-cycle or four-cycle reciprocating engine for an automobile.

  In particular, the internal combustion engine according to the present invention can change the idle speed by changing the intake air amount related to the air sucked into the cylinder, for example, an electronically controlled throttle valve or an ISC (Idle Speed). Control) Idle speed variable means such as a valve is provided.

  Here, the “idle speed” according to the present invention refers to an engine speed that can be taken by the internal combustion engine in a no-load state such as a state where the accelerator pedal is not operated by the driver and the vehicle is stopped. It is. Such an idle rotational speed inevitably increases or decreases as the intake air amount is controlled to increase or decrease by the idle rotational speed variable means.

  According to the control apparatus for an internal combustion engine according to the present invention, during its operation, setting means configured as various processing units such as an ECU (Electronic Control Unit), various controllers or various computer systems such as a microcomputer device, etc. As a result, the target value of the idle speed is set.

  When the target value of the idling engine speed is set, the idling engine speed of the internal combustion engine is set by control means configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, for example. The idling speed variable means is controlled, for example, physically, electrically, mechanically or mechanically so as to reach the target value. At this time, for example, the throttle valve opening (hereinafter referred to as “throttle opening” as appropriate), the ISC valve opening, and the like are feedback-controlled so that the idle speed follows the target value. The number is maintained at the target value.

  The engine speed of the internal combustion engine basically does not decrease below the idling speed unless there is an abnormality in the combustion state such as misfire, and except for the fluctuation of the engine speed during the feedback control as described above. . Accordingly, the engine speed is maintained at an idle speed or a value equivalent to the engine speed, for example, immediately before stopping the vehicle, for example, during braking or deceleration.

  Here, in particular, the driving force of the drive wheels at the time of braking of the vehicle increases as the engine speed increases, so that the higher the idle speed, the more braking force is required. On the other hand, since the non-driving wheels are more likely to have a braking force than the driving wheels, in most cases, the non-driving wheels are likely to be locked before the driving wheels. Therefore, the higher the idling speed, the longer the braking time while the non-driving wheels are in the locked state, and depending on the road surface condition, for example, the braking performance may be deteriorated, for example, the vehicle is pushed forward. Such a problem is remarkable when the drive mode of the vehicle is FR. Therefore, in the control apparatus for an internal combustion engine according to the present invention, the deterioration of the braking performance is suitably suppressed by the following action of the setting means.

  That is, the setting means sets the target value of the idle speed to a provisional value that is less than the reference value in at least a part of the braking period of the vehicle, and sets the target value to the reference value in other periods excluding at least a part of the braking period. Set.

  Here, the “reference value” means various states or various performances such as the warm-up state of the internal combustion engine, environmental performance such as fuel consumption rate, combustion performance, or comfort performance such as NV (Noise and Vibration). Alternatively, it refers to a reference idle speed determined in consideration of various index values representing them, and may be a variable value or a fixed value depending on these various performances, states, index values, etc. Any value may be used. In the case of a variable value, for example, it may be changed continuously within a predetermined range, or may be changed stepwise or discretely between a plurality of types of values.

  For example, such a reference value may be set as low as possible in consideration of environmental performance within a range in which deterioration of combustion performance and NV are not practically manifested, and based on such values. When the internal combustion engine is not warmed up, it may be set higher for the purpose of promoting warm-up. Such a setting mode of the reference value may be determined in advance so that the above-described various states and various indexes can be balanced in a high dimension experimentally, empirically, or based on simulation or the like.

  On the other hand, the provisional value is a value less than the reference value (of course, if the reference value is variable in accordance with the driving condition of the vehicle or the operating condition of the internal combustion engine, the reference value at that time). Is a temporary target value for ensuring the braking performance of the vehicle. Therefore, the provisional value is set at least part of the braking period, for example, immediately before the vehicle stops, for example, in an extremely low vehicle speed range of about 0 to 5 km / h as the vehicle speed. However, the provisional value setting period is not limited to this, and may be free within the range of the braking period.

  When the target value is set to such a provisional value, the idling speed decreases even if temporarily compared with the case where no such provisional value is taken. Accordingly, the driving force applied to the driving wheel is considerably reduced. As the driving force decreases, the braking force required to stop the vehicle decreases, for example, the sense of discomfort given to the driver is reduced, and the braking distance increases due to the driving wheels not being able to stop. Is prevented. Alternatively, the time for further increasing the braking force applied to the driving wheel in a state where the non-driving wheel is locked is shortened. That is, the braking performance of the vehicle is relatively improved.

  On the other hand, the reference value described above is set as the target value during the period excluding the period during which the provisional value is set (at least a part of the braking period). As described above, the reference value is a value that can be determined in consideration of the above-described various states, index values, and the like, and at least a period during which it is not necessary to prioritize the guarantee of braking performance over other requirements (for example, when stopped And the initial stage of braking) are values that can be optimal target values. Therefore, the braking performance of the vehicle is effectively ensured by the action of such setting means. Note that the target value does not necessarily have to be set as the reference value in the entire period excluding the period in which the provisional value is set.

  As described above, according to the control device for an internal combustion engine according to the present invention, the braking performance deterioration that may occur in at least a part of the braking period due to the idle rotation speed (that is, the target value) to be maintained, It is possible to effectively suppress the target value by setting the target value to a provisional value.

  In one aspect of the control device for an internal combustion engine according to the present invention, the reference value includes a first reference value and a second reference value higher than the first reference, and specifies the warm-up state of the internal combustion engine And a determining means for determining whether or not the internal combustion engine is in a cold state based on the specified warm-up state, and the setting means is configured so that the internal combustion engine is in the cold state. When the target value in a period excluding at least a part of the braking period is set to the second reference value, and the target value is set to the second reference value, at least the braking period The target value in a part is set to the provisional value.

  According to this aspect, the warm-up state of the internal combustion engine is specified by the specifying means configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device.

  Here, “specific” in the present invention refers to, for example, detecting directly or indirectly as a physical numerical value or an electrical signal corresponding to the physical numerical value via some detection means, appropriate storage means, etc. Select or estimate the corresponding numerical value from the map etc. stored in, and derive from the detected physical numerical value or electrical signal or the selected or estimated numerical value according to a preset algorithm or calculation formula, etc. Alternatively, it is a broad concept encompassing simply obtaining values, etc. detected, selected, estimated or derived in this way as electrical signals or the like.

  The “warm-up state” specified by the specifying means is, for example, binary or stepwise such as whether the internal combustion engine is sufficiently warmed up or the degree of warm-up. Further, it may be a qualitative state or a physical quantity such as a cooling water temperature or a lubricating oil temperature that can quantitatively define the warm-up state. Further, the qualitative state described above may be specified based on various index values that can quantitatively define such a warm-up state.

  When the warming-up state is specified by the specifying means, for example, whether or not the internal combustion engine is in a cold state by the determining means configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, etc. Is determined.

  On the other hand, according to this aspect, the reference value related to the target value of the idle speed includes the first reference value and the second reference value higher than the first reference value, and the setting means sets the target value of the idle speed as the reference value. When the internal combustion engine is in a cold state, the target value is set to the second reference value. That is, when the internal combustion engine is in a cold state, for example, during cold start, warm-up promotion control called so-called fast idle is performed, and warm-up is promoted by setting the target value higher. .

  When the target value is set to the second reference value (preferably the same as when it is determined that the internal combustion engine is in a cold state), the setting means sets the target value for at least a part of the braking period as a provisional value. Set to. More specifically, in this mode, for example, only when the internal combustion engine is in a state where fast idling should be executed, the idling speed is reduced to a provisional value during braking.

  The target value is set to the second reference value as a result of giving priority to the warm-up performance, and the influence on the deterioration of the braking performance may inevitably increase, but conversely, the first reference value includes at least the warm-up performance. Since there is no circumstance in which performance should be prioritized over other factors, for example, the first reference value can be set in advance to such a value that deterioration in braking performance is not practically manifested. In such a case, regarding the period in which the reference value is set to the first reference value, the necessity of setting the target value to the provisional value at the time of braking can be reduced to such an extent that it can be substantially ignored. In addition, the deterioration of braking performance can be suppressed, which is advantageous in practice.

  In this aspect, the specifying unit specifies at least one of the engine temperature and the outside air temperature of the internal combustion engine as at least a part of the warm-up state.

  The engine temperature and the outside air temperature are indicators that can suitably define the warm-up state of the internal combustion engine. When at least one of these is specified by the specifying means, the warm-up state of the internal combustion engine is relatively high. It is preferable to be specified by accuracy.

  The engine temperature is a concept encompassing the temperature of the internal combustion engine. For example, the temperature of the cooling water circulating in the cooling system for cooling the internal combustion engine and the mechanical operation of the internal combustion engine are lubricated. Therefore, it is intended to include various indicators such as the temperature of the lubricating oil supplied for circulation.

  In another aspect of the control device for an internal combustion engine according to the present invention, the vehicle controls the braking means for braking the vehicle, and controls the braking means so that the wheels are not locked when the vehicle is braked. And at least a part of the braking period includes at least a part of a period during which the braking unit is controlled so that the locking is not generated by the braking control unit.

  According to this aspect, the vehicle includes, for example, various braking members provided in each wheel, a plurality of wheel cylinders provided in each wheel, and a brake actuator that transmits hydraulic pressure related to brake fluid to each wheel cylinder. A braking means comprising a system and the like and a braking control means for controlling these braking means are provided, and a function for preventing wheel locking, for example, called ABS (Antilock Braking System) or the like, is realized.

  Here, when the braking means is controlled by the braking control means so that the wheels are not locked, the vehicle is often in an urgent state requiring more safety and braking performance. When such a period is included as at least a part of the set braking period, the effect according to the present invention can be remarkably exerted, which is preferable.

  In another aspect of the control apparatus for an internal combustion engine according to the present invention, the setting means sets the target value to the reference value when the vehicle stops with the target value set to the provisional value. To do.

  When the vehicle stops, for example, the driver usually operates the brake pedal under unconsciousness in accordance with the behavior of the vehicle. Therefore, in such a vehicle stop period, usually, the behavior of the vehicle exceeding the driver's prediction range hardly occurs, and the braking performance is hardly deteriorated.

  According to this aspect, when the vehicle stops with the target value set to the provisional value, the target value is returned to the reference value, so that environmental performance such as fuel consumption rate, combustion performance, or comfort performance such as NV Etc. can be optimized, which is beneficial. Note that “when stopped” is not necessarily limited to the time point when the stop of the vehicle is confirmed, and may be the time point when a predetermined time has passed since the stop point of the vehicle. The timing for returning the target value to the reference value is such that, for example, experimentally, empirically, or based on simulation in advance, the NV deterioration due to continuing setting of the idle rotation speed to the provisional value does not become obvious. Alternatively, it may be set so as not to give the driver a sense of incompatibility when the idle speed is returned to the reference value.

  In this aspect, the setting means may set the target value to the reference value by gradually changing the target value from the provisional value to the reference value.

  Although the vehicle is stopped, the possibility that the driver feels uncomfortable cannot be ignored if the target value is abruptly changed from the provisional value to the reference value. Thus, when the target value is gradually changed from the provisional value to the reference value, it is preferable because the driver does not feel uncomfortable.

  Note that “gradual change” means a change rate that is suppressed to such an extent that problems such as the above-mentioned uncomfortable feeling and deterioration of braking performance, which are caused by a large change rate, do not become apparent in practice. This is a comprehensive concept, and as long as such a concept is secured, the aspect of the change may be stepwise or continuous (regardless of whether it is linear or non-linear).

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<Configuration of Embodiment>
First, the configuration of a vehicle according to an embodiment of the present invention will be described with reference to FIG. Here, FIG. 1 is a schematic view of the vehicle 10.

  In FIG. 1, a vehicle 10 includes an ECU 100 and an engine 200.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the entire operation of the vehicle 10. It is an example of “apparatus”. The ECU 100 is configured to be able to execute an idle speed setting process described later according to a control program stored in the ROM.

  The vehicle 10 includes an accelerator pedal 20 and a brake pedal 22 that are configured to be operated by a driver. An accelerator position sensor 21 configured to detect an operation amount of the accelerator pedal 20 (hereinafter referred to as “accelerator opening” as appropriate) is disposed in the vicinity of the accelerator pedal 20. The accelerator position sensor 21 is electrically connected to the ECU 100, and the detected accelerator opening is always grasped by the ECU 100. On the other hand, a brake position sensor 23 configured to be able to detect an operation amount of the brake pedal 22 is disposed in the vicinity of the brake pedal 22. The brake position sensor 23 is electrically connected to the ECU 100, and the detected operation amount of the brake pedal 22 is always grasped by the ECU 100.

  The engine 200 is a gasoline engine that functions as a power source of the vehicle 10, and is an example of the “internal combustion engine” according to the present invention. Here, the detailed configuration of the engine 200 will be described with reference to FIG. Here, FIG. 2 is a schematic diagram of the engine 200. In the figure, the same reference numerals are given to the same portions as those in FIG. 1, and the description thereof will be omitted as appropriate.

  In FIG. 2, the engine 200 causes the air-fuel mixture to explode by an ignition operation of an ignition device 202 in which a part of a spark plug that is a part of the cylinder 201 is exposed, and the piston 203 reciprocates in response to the explosive force. The movement can be converted into the rotational movement of the crankshaft 205 via the connection rod 204. A crank position sensor 206 that detects the rotational position of the crankshaft 205 is installed in the vicinity of the crankshaft 205. The crank position sensor 206 is electrically connected to the ECU 100, and the ECU 100 is configured to control the ignition timing and the like of the ignition device 202 based on the rotational position of the crankshaft 205 detected by the crank position sensor 206. Has been. Further, the ECU 100 is configured to be able to calculate the engine speed Ne of the engine 200 based on the rotational position of the crankshaft 205. Below, the principal part structure of the engine 200 is demonstrated with a part of the operation | movement.

  When the fuel in the cylinder 201 is burned, the air sucked from the outside passes through the intake pipe 207 and is mixed with the fuel injected from the injector 214 at the intake port 213 to become the above-mentioned air-fuel mixture. The fuel is stored in the fuel tank 215 and is pumped and supplied to the injector 214 via the delivery pipe 216 by the action of the low pressure pump 217. The injector 214 is electrically connected to the ECU 100, and is configured to be able to inject the supplied fuel into the intake port 213 according to the control of the ECU 100.

  The communication state between the inside of the cylinder 201 and the intake pipe 207 is controlled by opening and closing the intake valve 218. The air-fuel mixture combusted in the cylinder 201 becomes exhaust gas and is guided to the exhaust pipe 221 via the exhaust port 220 when the exhaust valve 219 that opens and closes in conjunction with opening and closing of the intake valve 218 is opened.

  A cleaner 208 is disposed on the intake pipe 207 to purify air sucked from the outside. An air flow meter 209 is disposed on the downstream side (cylinder side) of the cleaner 208. The air flow meter 209 has a form called a hot wire type, and is configured to be able to directly detect the mass flow rate of the sucked air. The air flow meter 209 is electrically connected to the ECU 100, and the detected mass flow rate of the intake air is constantly grasped by the ECU 100.

  On the downstream side of the air flow meter 209 in the intake pipe 207, there is a throttle valve 210 that adjusts the amount of intake air related to the air sucked into the cylinder 201 (that is, an example of the “idle rotation speed varying means” according to the present invention). It is arranged. A throttle position sensor 212 is electrically connected to the throttle valve 210, and is configured to be able to detect the throttle opening that is the opening.

  On the other hand, the ECU 100 controls the drive state of the throttle valve motor 211 based on the accelerator opening detected by the accelerator position sensor 21 described above. The throttle valve 210 is configured to be driven by the driving force of the throttle valve motor 211. The throttle valve 210 is an electronically controlled throttle valve that is driven by the driving force of the throttle valve motor 211 controlled by the ECU 100. The throttle opening is determined by the ECU 100 according to the driver's intention (that is, the accelerator opening). ) Can be controlled independently. For example, the throttle opening is controlled so as to maintain the target value of the idle speed regardless of the accelerator opening in the idle control described later.

  A three-way catalyst 223 is installed in the exhaust pipe 221. The three-way catalyst 223 is a catalyst capable of purifying CO (carbon monoxide), HC (hydrocarbon), and NOx (nitrogen oxide) discharged from the engine 200, respectively. An air-fuel ratio sensor 222 is disposed upstream of the three-way catalyst 223 in the exhaust pipe 221. The air-fuel ratio sensor 222 is configured to detect the air-fuel ratio of the engine 200 from the exhaust gas discharged through the exhaust port 220. The air-fuel ratio sensor 224 is electrically connected to the ECU 100, and the detected air-fuel ratio is constantly grasped by the ECU 100.

  In addition, a temperature jacket 224 for detecting the temperature of cooling water for cooling the engine 200 (hereinafter, referred to as “engine cooling water temperature” as appropriate) is provided in a water jacket installed in the cylinder block that houses the cylinder 201. It is arranged. The temperature sensor 224 is electrically connected to the ECU 100, and the detected engine coolant temperature is constantly grasped by the ECU 100.

  Returning to FIG. 1, the vehicle 10 includes, as wheels, a left front wheel FL and a right front wheel FR that are non-driving wheels, and a left rear wheel RL and a right rear wheel RR that are driving wheels. This is an FR vehicle in which driving wheels are driven.

  The rotational power of the engine 200 via the crankshaft 205 is input to a transmission system 11 including a torque converter 11A and an ECT (Electronic Controlled Transmission) 11B.

  The torque converter 11A includes an input shaft connected to the crankshaft 205 of the engine 200 and an output shaft (both not shown) connected to the ECT 11B, and the rotational power of a pump impeller (not shown) connected to the input shaft. A torque is amplified by an ATF (Automatic Transmission Fluid) or by a stator (not shown) and transmitted to a turbine runner (not shown) connected to the output shaft as rotational power. That is, the power of the engine 200 is transmitted to the ECT 11B via the torque converter 11A. The rotational speed of the turbine runner in the torque converter 11A (hereinafter referred to as “turbine rotational speed” as appropriate) is detected by a rotation sensor (not shown) and is constantly grasped by the ECU 100 electrically connected to the rotation sensor. It has a configuration.

  The ECT 11B is a transmission that includes a plurality of friction engagement devices (not shown) including a plurality of clutch elements, a brake element, a one-way clutch element, and the like. The ECT 11B is electrically connected to the ECU 100, and a plurality of different ECTs 11B are obtained by changing the engagement state between these friction engagement devices through drive control of various solenoids (not shown) by the ECU 100. The gear ratio can be obtained.

  Note that the ECT 11B (or the transmission system 11 including the torque converter 11A) has the same configuration as a known electronically controlled automatic transmission, and although detailed illustration thereof is omitted, in the present embodiment, the vehicle 10 As the gear range corresponding to the forward direction, there are five gear ranges of “1st”, “2nd”, “3rd”, “4th” and “5th” in descending order of the gear ratio. The structure is such that a large gear ratio is obtained in descending order. When the vehicle 10 moves forward, the ECU 100 selects one of the above-described shift ranges by controlling the engagement state of each friction engagement device in the ECT 11B, and a value corresponding to the selected shift range of the ECT 11B. Can be set.

  The output shaft of the ECT 11 </ b> B is connected to a propeller shaft 12 that is a transmission force transmission shaft in the vehicle 10. The propeller shaft 12 is configured to be able to rotate with the rotation of the output shaft of the ECT 11B.

  The propeller shaft 12 is further connected to a differential 13. The differential 13 is configured to be able to convert the rotation of the propeller shaft 12 into the rotation of the drive shafts 14L and 14R corresponding to each drive wheel. As described above, in the vehicle 10, the rotational power of the engine 200 is transmitted to the drive wheels sequentially through the torque converter 11A, ECT 11B, the propeller shaft 12, the differential 13, and the drive shafts 14L and 14R, and each drive wheel rotates. It has become.

  On the other hand, the non-driving wheels FL and FR are configured to be able to rotate independently of each other, and the steering device for controlling the traveling direction of the vehicle 10 via the steering shafts 18L and 18R, respectively. 17 is connected. The steering device 17 is connected to a steering wheel (not shown) via a steering shaft (not shown), and is configured to be able to control the steering angle of each non-driven wheel reflecting the operation of the steering wheel by the driver. Has been.

  The driving wheels RL and RR and the non-driving wheels FL and FR are provided with braking devices 15RL, 15RR, 15FL and 15FR having the same configuration. Each brake device has a configuration of a so-called disc brake device, and is configured to be able to apply a braking force to each drive wheel and each non-drive wheel.

  The braking force related to each braking device is controlled according to the driving state of a wheel cylinder (that is, 16RL, 16RR, 16FL, and 15FR shown in the figure) provided in each braking device. Each wheel cylinder is configured to be able to apply a driving force according to a predetermined hydraulic pressure of the brake fluid to each braking device, and as the driving force increases, each braking device increases the braking force on each wheel. It is configured to be able to apply power.

  The brake fluid pressure supplied to each wheel cylinder is controlled by a brake actuator 19. The brake actuator 19 includes a reservoir tank, an electric pump, a delivery pipe, a plurality of electromagnetic valves, a holding valve, and the like, and transmits brake fluid determined according to the driving state of the electromagnetic valve, the holding valve, etc. by the action of the electric pump. The brake fluid is appropriately supplied through the path, and finally the hydraulic pressure of the brake fluid is applied to each wheel cylinder.

  Although not shown, each wheel is provided with a wheel speed sensor that is electrically connected to the ECU 100 and can detect the wheel speed of each wheel. The detected wheel speed is always detected by the ECU 100. It is a configuration that can be grasped. The ECU 100 is configured to be able to individually control the braking force of each wheel based on the detected wheel speed. For example, when any wheel is locked, the braking force of the corresponding wheel is configured. It is possible to execute so-called antilock control that temporarily reduces the lock state and cancels the locked state. That is, the braking system provided in the vehicle 10 including a braking device, a wheel cylinder, and the like has a configuration equivalent to a so-called ABS.

  The brake actuator 19 is electrically connected to the ECU 100, and its operation is controlled by the ECU 100 to the upper level. At this time, the ECU 100 controls the brake actuator 19 so that a braking force corresponding to the operation amount of the brake pedal detected by the brake pedal sensor is obtained.

<Operation of Embodiment>
<Idle control>
In the vehicle 10, idle control is executed during a period of time when the vehicle is stopped or when braking is decelerated, and the engine speed of the engine 200 is controlled to a set target value of the engine speed. The target value of the idle speed is basically set to Nebase (that is, an example of the “first reference value” according to the present invention) by the ECU 100. Nebase is a value of about 500 to 600 rpm.

  On the other hand, when the engine 200 is in a cold state, for example, during a cold start, the ECU 100 executes fast idle control in order to promote warm-up of the engine 200. When the fast idle control is executed, the ECU 100 sets the idle speed to Ne1 (Ne1> Nbase, where Ne1 is an example of the “second reference value” according to the present invention). The value of Ne1 is about 1000 rpm, and these values of Nebase and Ne1 are stored in the ROM in advance.

  When the idle control is executed, the ECU 100 feedback-controls the throttle opening degree via the drive control of the throttle valve motor 211 so that the engine speed Ne converges to the set target value of the idle speed. .

  Here, the driving force Fd acting on the vehicle 10 during braking of the vehicle 10 is expressed by the following equation (1). Similarly, the braking force Fb acting on each wheel to brake the vehicle 10 during braking of the vehicle 10 is expressed by the following equation (2). In the equation (1), Fc is a creep force acting on the drive wheels RL and RR via the transmission system 11 and the like, and αW is an inertial force of the vehicle 10. In the equation (2), Ff is a braking force acting on the non-driving wheels FL and FR, and Fr is a braking force acting on the driving wheels RL and RR. When the braking force Fb becomes equal to or greater than the driving force Fd, the vehicle 10 stops.

Fd = Fc + αW (1)
Fb = Ff + Fr (2)
Here, in particular, the creep force Fc changes according to the engine speed Ne of the engine 200. For example, if the shift range of the ECT 11B in the transmission system 11 is fixed, the creep force Fc becomes a larger value as the engine speed Ne is higher. In order to stop the vehicle 10, it is necessary to apply a braking force Fr that can cancel the creep force Fc to the drive wheels. However, the braking force Ff necessary for stopping the non-driving wheels should be smaller than the braking force Fr, and when a braking force Fr large enough to cancel the creep force Fc is applied to the driving wheels, Non-driving wheels tend to fall into a locked state.

  At this time, the wheel speed of each wheel is detected by controlling the brake actuator 19 even if different hydraulic pressures are transmitted to the respective wheel cylinders corresponding to the rear wheel as the driving wheel and the front wheel as the non-driving wheel. A wheel speed sensor (not shown) is difficult to realize because an error increases in an extremely low vehicle speed region immediately before the vehicle stops.

  The idle speed Nebase is a low value that does not cause a substantial deterioration in braking performance even if the non-driving wheels are locked as described above, or a low value that does not cause the non-driving wheels to be locked. However, the deterioration of braking performance is unlikely to appear under normal driving conditions, but during fast idle control giving priority to warm-up of the engine 200, the driver feels normal operation as the idle speed increases. Thus, even if the brake pedal 22 is operated, the vehicle 10 does not stop, or the front wheel that is a non-driving wheel is locked and the time during which the braking force is continuously applied to the rear wheel that is a driving wheel becomes longer, resulting in a longer braking distance. Easy to be. That is, the braking performance of the vehicle is likely to deteriorate. In particular, when the traveling road surface of the vehicle 10 is a low μ road such as an ice board, such a problem is likely to appear remarkably.

  Therefore, in the present embodiment, the ECU 100 executes the idle rotation speed setting process, thereby suppressing the deterioration in braking performance during the fast idle control.

<Details of idle speed setting process>
Here, with reference to FIG. 3, the details of the idle speed setting process will be described. FIG. 3 is a flowchart of the idle speed setting process.

  In FIG. 3, the ECU 100 determines whether or not the fast idle condition is satisfied (step A10). Here, in the present embodiment, the ECU 100 determines that the fast idle condition is satisfied when the engine coolant temperature Tw is less than the reference value or the outside air temperature is less than the reference value. For example, the reference value of the engine coolant temperature Tw is set to a value of about 65 ° C., and the reference value of the outside air temperature is set to a value of about 20 ° C. below the freezing point.

  When the fast idle condition is not satisfied (step A10: NO), the ECU 100 sets the target value of the idle speed to the above-mentioned Nebase (step A12), and returns the process to step A10. When the idle speed target value is set in the idle speed setting process, the ECU 100 determines the throttle opening degree control already described so that the engine speed becomes the set target value at the appropriate idle control timing. Execute.

  On the other hand, when the fast idle condition is satisfied (step A10: YES), the ECU 100 further determines whether or not the idle rotational speed reduction condition is satisfied (step A11). Here, the idle speed reduction condition is a condition defined as the above-described deterioration of the braking performance should be eliminated. In this embodiment, the accelerator opening is zero and the shift range of the ECT 11B is “1st”. When the vehicle speed is 9 km / h or less and the brake pedal 22 is operated, it is determined that the condition for decreasing the idling engine speed is satisfied.

  When the idle speed reduction condition is not satisfied (step A11: NO), the ECU 100 sets the target value of the idle speed to Ne1 described above (step A14), and returns the process to step A10.

  When the idle speed reduction condition is satisfied (step A11: YES), the ECU 100 sets the target value of the idle speed to Ne0 (Nebase <N0 <Ne1, where Ne0 is an example of the “provisional value” according to the present invention. ) (Step A13). In this embodiment, Ne0 is set to a value of about 800 rpm.

  The case where the condition for reducing the idling speed is satisfied, that is, the case where the vehicle 10 can be considered to stop soon, is considered that the braking performance of the vehicle 10 is likely to be deteriorated due to the excessive braking force of the driving wheel described above. . Therefore, in such a case, the ECU 100 causes the target value of the idle speed to be lower than Ne1, which is the original target value, and the braking performance of the vehicle 10 is improved.

  When the target value of the idle speed is set to Ne0, ECU 100 determines whether vehicle 10 has stopped (step A15). Here, the turbine rotational speed of the torque converter 11A is referred to for determining whether or not the vehicle 10 has stopped. The ECU 100 determines that the vehicle 10 has stopped when the turbine rotation speed becomes zero.

  If the vehicle 10 has not stopped (step A15: NO), the ECU 100 may have shifted to a state where the above-described idle rotational speed reduction condition is not satisfied, such as when the vehicle 10 starts accelerating. Return to A11 and repeat the series of processing. When the idle speed reduction condition is satisfied without change, the process related to step A15 is executed without changing the target value of the idle speed to Ne0.

  When the vehicle 10 stops (step A15: YES), the ECU 100 activates a built-in timer to count the elapsed time from the vehicle stop time (step A16), and whether or not the elapsed time exceeds a predetermined value. It discriminate | determines (step A17).

  When the elapsed time is equal to or less than the predetermined value (step A17: NO), the ECU 100 controls the process to the standby state, and when the elapsed time exceeds the predetermined value (step A17: YES), the target value for the idle speed is set. Is gradually changed from the temporary target value Ne0 to the original target value Ne1 (step A18). At this time, the ECU 100 increases the target value at an increase speed set in advance so as not to give the driver a sense of incongruity, and finally returns the idle speed to Ne1. The idle speed setting process is performed in this way, for example.

  Here, with reference to FIG. 4, the idle speed setting process will be further described. FIG. 4 is a schematic diagram showing the state of the vehicle 10 and the state of various signals in the process of executing the idle speed setting process. In FIG. 4, it is assumed that the above-described fast idle condition is satisfied in advance.

  In FIG. 4, the horizontal axis is common in time, and the accelerator opening, the brake signal, the vehicle speed, the control execution flag, and the engine speed are shown in the vertical axis series in order from the top.

  It is assumed that the accelerator opening is reduced from Acc1 (Acc1> 0) to zero at time T0, that is, the driver stops the operation of the accelerator pedal 20. At the same time, the brake signal (which is different from the amount of brake operation and takes a binary value indicating whether or not the brake pedal 22 is operated) is changed from L (i.e., indicating that the brake pedal 22 is not operated) to H (i.e. It represents the state being operated).

  As the pedals are operated, the vehicle speed of the vehicle 10 starts to decrease from the vehicle speed V1 (9 km / h> V1> 0) that has been maintained until then. Further, as the vehicle speed decreases, the ECU 100 changes the shift range of the ECT 11B (different from the operation position of the shift lever) to “1st” described above at time T1. That is, at time T1, coasting down from “2nd” to “1st” is executed. At this time, the operation lever (shift knob, etc.) of the ECT 11B operated by the driver may remain set in the D range, for example, and the gear ratio in the ECT 11B is changed so that it gradually increases as the vehicle speed decreases. Be controlled.

  On the other hand, in the present embodiment, the vehicle speed V0 at the coast down point is 9 km / h or less, and the above-described idle rotational speed reduction condition is satisfied at time T1. Therefore, at time T1, the control execution flag for executing the control related to the decrease in the idle speed (that is, the control for setting the target value of the idle speed to Ne0) represents “L” indicating that the control is not executed. To “H” indicating that the control should be executed.

  Thus, since the target value of the idle speed is set to Ne0 at time T1, the engine speed Ne that continues to decrease as the vehicle speed decreases reaches and is maintained at the idle speed Ne0 corresponding to the lower limit at time T2. The

  On the other hand, the vehicle speed of the vehicle 10 becomes zero at time T3. Accordingly, the timer starts counting from time T3, and at time T4 when time ΔT has elapsed from time T3, the control execution flag becomes “L” again, the target value of the idle speed is set to Ne1 again, and the engine speed is increased. The number is gradually changed to the idle speed Ne1. As a result of following the progress of such gradual change, at time T5, the engine speed Ne of the engine 200 reaches the idle speed Ne1, and thereafter, the idle speed Ne1 is maintained.

  Next, the effect of the idle speed setting process according to the present embodiment will be described with reference to FIG. Here, FIG. 5 is a schematic diagram showing the time passage of the force acting on the vehicle 10.

  In FIG. 5, the horizontal axis represents time, and the vertical axis represents the force acting on the vehicle 10. Near the center of the vertical axis is zero, and at this position, the sum of the driving force and the braking force acting on the vehicle 10 is zero, that is, the balance between the driving force and the braking force is maintained. In other words, the vertical axis indicates that the driving force increases toward the upper side and the braking force increases toward the lower side with respect to zero, and the region below the zero (that is, the braking force is superior). In the region), the vehicle 10 is stopped.

  Here, when the target value of the idle speed of the engine 200 is set to the target value Ne1 during fast idle control, the characteristic of the driving force Fd during braking is shown as PrfFd1 (thin broken line). .

  On the other hand, the characteristic of the braking force Fb is shown in the figure PrfFb (thick solid line), which is the characteristic of the braking force PrfFf applied to the non-driving wheel (dashed line) and the characteristic of the braking force PrfFr applied to the driving wheel (two-dot chain line). Is the sum of As shown in the drawing, the non-driving wheels are locked at time T6, and the braking force Ff applied to the non-driving wheels takes a constant value regardless of the actual driving state of the braking device after time T6.

  When the driving force Fd and the braking force Fb are expressed as described above, the time characteristic of the force actually acting on the vehicle is the sum of the characteristic PrfFd1 and the characteristic PrfFb, and changes as shown in the characteristic PrfF1 (thick broken line). That is, the vehicle 10 stops at time T8.

  On the other hand, when the target value of the idle speed is set to the temporary value Ne0 by the idle speed setting process according to the present embodiment, the driving force characteristic is an amount corresponding to the difference between Ne1 and Ne0 with respect to the characteristic PrfFd1. The negative characteristic offset is given, and the characteristic PrfFd0 (thin solid line) is obtained.

  Therefore, the time characteristic of the force acting on the vehicle 10 becomes the illustrated characteristic PrfF0 (thick solid line), and the vehicle 10 stops at time T7.

  As described above, when the idle speed setting process according to the present embodiment is performed, the time required for actually stopping the vehicle is compared with the case where the fast idle is normally performed without performing the idle speed setting process. , The time corresponding to “T8-T7” is shortened, and the braking distance is greatly shortened. That is, it is possible to suppress the deterioration of the braking performance of the vehicle 10 by reducing the target value of the idle speed during braking of the vehicle during the period in which the fast idle control is to be performed.

  It should be noted that the above-described effect of relatively improving by reducing the idling speed is, for example, when anti-lock control is being executed in any of the braking devices of the vehicle 10, that is, more generally in the vehicle. In the case where the anti-lock brake system is operated, the effect is similarly effective. In view of the fact that the anti-lock control is remarkably activated in an emergency, the effect of improving the safety of the vehicle 10 is remarkable.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and the control of the internal combustion engine accompanying such a change. The apparatus is also included in the technical scope of the present invention.

1 is a block diagram of a vehicle according to an embodiment of the present invention. It is a schematic diagram of the engine in the vehicle of FIG. 2 is a flowchart of idle speed setting processing executed by an ECU in the vehicle of FIG. 1. It is a schematic diagram showing the state of a vehicle and each signal in an idle speed setting process. It is a schematic diagram showing the time course of the force which acts on the effect of this embodiment and acts on a vehicle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 11B ... ECT, 20 ... Accelerator pedal, 22 ... Brake pedal, 100 ... ECU, 200 ... Engine, 210 ... Throttle valve, FL, FR, RL, RR ... Wheel.

Claims (6)

An internal combustion engine for controlling an internal combustion engine in a vehicle having an internal combustion engine having an idle rotation speed variable means capable of changing an idle rotation speed by changing an intake air amount related to air sucked into the cylinder. A control device,
Setting means for setting the target value of the idle speed to a provisional value less than a reference value in at least a part of the braking period of the vehicle and to set the reference value in a period excluding at least a part of the braking period; ,
And a control means for controlling the idle speed variable means so that the idle speed becomes the set target value. The reference value includes a first reference value and a second reference value higher than the first reference,
Specifying means for specifying a warm-up state of the internal combustion engine;
And a discriminating means for discriminating whether or not the internal combustion engine is in a cold state based on the specified warm-up state,
The setting means sets the target value in a period excluding at least a part of the braking period to the second reference value when the internal combustion engine is in the cold state, and the target value is set to the second reference value. 2. The control device for an internal combustion engine according to claim 1, wherein when the value is set to a value, the target value in at least a part of the braking period is set to the provisional value. The control device for an internal combustion engine according to claim 2, wherein the specifying means specifies at least one of an engine temperature and an outside air temperature of the internal combustion engine as at least a part of the warm-up state. The vehicle further includes braking means for braking the vehicle, and braking control means for controlling the braking means so that the wheels are not locked when the vehicle is braked,
4. At least a part of the braking period includes at least a part of a period during which the braking unit is controlled so that the lock is not generated by the braking control unit. The control apparatus of the internal combustion engine described in 1. The setting means sets the target value to the reference value when the vehicle stops in a state where the target value is set to the provisional value. The control apparatus for an internal combustion engine according to the item. The control device for an internal combustion engine according to claim 5, wherein the setting means sets the target value to the reference value by gradually changing the target value from the provisional value to the reference value.

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