JP5293424B2 - Idle stop control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always give a sufficient starting feeling to an occupant of a vehicle by stabilizing behavior at starting of the vehicle regardless of a stepping-in amount when a brake pressure relative to a wheel of the vehicle is retained to the maximum value of the brake pressure by stepping-in of a brake pedal from starting of automatic stopping to the present time or a value near it during automatic stopping of an engine. <P>SOLUTION: When the brake pressure by stepping-in becomes a predetermined value or less by a release of stepping-in of the brake pedal (time t2), the brake pressure relative to the wheel is reduced to a predetermined pressure and the brake pressure relative to the wheel is released after the completion of reduction (time t3). <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention belongs to a technical field related to a vehicle idle stop control device that automatically stops a vehicle engine.

  2. Description of the Related Art Conventionally, an idle stop control device for a vehicle that automatically stops an engine when a predetermined stop condition is satisfied and restarts the engine when a predetermined restart condition is satisfied is well known ( For example, see Patent Document 1). And in patent document 1, the braking force of a vehicle is hold | maintained during an engine automatic stop, and when the engine restarts, the braking force of a vehicle is reduced according to the recovery state of the driving force of a vehicle, and, thereby, automatic It has been proposed to ensure good startability in a vehicle equipped with a transmission.

JP 2000-313253 A

  By the way, in a vehicle equipped with an automatic transmission, when the brake pedal is depressed and the vehicle stops with the shift range of the automatic transmission set to the travel range, the engine of the vehicle is automatically stopped. At the same time, when the depression of the brake pedal is released, it is conceivable that the engine is restarted on the assumption that the vehicle occupant has an intention to start. In this case, since the brake pedal is depressed while the engine is automatically stopped, the braking force of the vehicle is maintained as in the case of Patent Document 1. This braking force, that is, the brake pressure for the wheel, should be a value that depends on the amount of depression, but in order to keep it as high as possible, the brake pressure caused by the depression of the brake pedal from the start of the automatic stop to the present time It is preferable to keep the maximum value or a value in the vicinity thereof. Even when the depression of the brake pedal is released and the engine is restarted, the brake pressure is maintained as it is, for example, when the engine is completely started, the brake pressure for the wheels is released. When releasing the brake pressure, it is preferable to gradually reduce the brake pressure in order to give a good start feeling to the vehicle occupant.

  However, in such a configuration, the brake pressure immediately before the release changes depending on the amount of depression of the brake pedal, and the change characteristic of the brake pressure with respect to time at the time of release also changes depending on the magnitude of the brake pressure, and the depression of the brake pedal is released. The time from the start until the vehicle starts is unstable. As a result, even if the slope of the road surface on which the vehicle is stopped is the same, the behavior at the start of the vehicle changes according to the amount of depression of the brake pedal at that time, and a good start fee is given to the vehicle occupant. There are cases where a ring cannot be applied.

  The present invention has been made in view of such a point, and an object of the present invention is to reduce the brake pressure applied to the wheels of the vehicle during the automatic stop of the engine from the start of the automatic stop to the present time. Regardless of the amount of depression, when the brake pressure is kept at the maximum value or the value near it, the vehicle's starting behavior can be stabilized and a good starting feeling can be given to the vehicle occupant. There is in doing so.

  In order to achieve the above object, according to the first aspect of the present invention, when the brake pedal is depressed and the vehicle stops when the shift range of the automatic transmission of the vehicle is set to the travel range, the engine of the vehicle is stopped. When the brake pedal is released, the engine is restarted when the brake pedal is released. Automatic brake control means for controlling the brake pressure so as to hold the brake pressure at the maximum value of the brake pressure by the depression of the brake pedal from the start of the automatic stop to the present time or a value in the vicinity thereof, the automatic brake control means, When the brake pressure due to the depression of the brake pedal is reduced to a predetermined value or less by releasing the depression of the brake pedal. To, and shall together with reducing to a predetermined pressure to the braking pressure for the wheel, and is configured to release the braking pressure to the wheel after the completion under low.

  With the above configuration, even when the brake pedal depressing amount decreases during the automatic engine stop, the brake pressure applied to the vehicle wheels is the same as the brake pressure generated by depressing the brake pedal from the start of the automatic stop to the present time. Since it is held at the maximum value or a value in the vicinity thereof (a value in consideration of an error or the like), the vehicle can be stably stopped even on a slope. Then, when the brake pressure due to the depression of the brake pedal is reduced to a predetermined value or less (a value that can be considered that the depression of the brake pedal is released) or less by releasing the brake pedal, the brake pressure on the wheel is reduced to the predetermined pressure, Since the brake pressure for the wheel is released from the predetermined pressure, the brake pressure immediately before the release is always the predetermined pressure regardless of the amount of depression of the brake pedal at the time of automatic stop, and as a result, the amount of depression of the brake pedal at the time of automatic stop is Regardless, the behavior at the start of the vehicle can be stabilized. Therefore, it is possible to always give a good start feeling to the vehicle occupant.

  According to a second aspect, in the first aspect, the automatic brake control means is configured to gradually decrease the brake pressure when the brake pressure is released.

  As a result, the brake pressure release control can be performed smoothly, and the vehicle does not suddenly jump out or start, so that a better starting feeling can be imparted to the vehicle occupant. It becomes like this.

  According to a third invention, in the first or second invention, the start timing of the brake pressure reduction to the predetermined pressure by the automatic brake control means is later than the restart start timing of the engine. It shall be.

  As a result, the reduction of the brake pressure on the wheels can be delayed as much as possible, and the movement of the vehicle accompanying the restart of the engine can be suppressed.

  According to a fourth invention, in any one of the first to third inventions, the automatic brake control means is configured so that a predetermined period of time elapses after the completion of the reduction of the brake pressure to the predetermined pressure and after the complete explosion of the engine. In this case, the brake pressure is configured to be released.

  As a result, the brake pressure is released in a state in which a stable driving force is transmitted from the engine to the wheels, so that even better starting feeling can be imparted to the vehicle occupant.

  In a fifth invention, in any one of the first to fourth inventions, the predetermined pressure holds the vehicle stopped in a state where no driving force is applied to the wheels when the stop position of the vehicle is uphill. It is possible pressure, and it is the pressure which can hold | maintain the stop of the said vehicle in the state where the creep force is applied to the said wheel on the downhill.

  In a sixth aspect based on the fifth aspect, the predetermined pressure is set according to the degree of inclination of the road surface on which the vehicle is stopped.

  According to these inventions, when the vehicle stops on a slope, the movement of the vehicle can be suppressed even if the brake pressure on the wheels decreases to a predetermined pressure.

  As described above, according to the idle stop control device for a vehicle of the present invention, when the brake pressure caused by the depression of the brake pedal is reduced to a predetermined value or less due to the release of the depression of the brake pedal, the brake pressure for the wheel is reduced to the predetermined pressure. At the same time, the brake pressure applied to the wheels is released after the completion of the reduction, so that the behavior at the start of the vehicle can be stabilized irrespective of the depression amount of the brake pedal at the time of automatic stop. A good start feeling can always be given to the occupant.

1 is a block diagram illustrating a schematic configuration of an idle stop control device for a vehicle according to an embodiment of the present invention. It is a figure which shows the structure of the brake system of the said vehicle. It is a graph which shows the relationship between the inclination of the road surface where the vehicle has stopped, and the 1st predetermined pressure. It is a graph which shows the relationship between the inclination of the road surface where the vehicle has stopped, and the time T until the brake pressure with respect to a wheel becomes 0 from a 1st predetermined pressure. It is a graph which shows the relationship between the inclination of the road surface where the vehicle has stopped, and the 1st predetermined pressure. It is a time chart which shows an example of the change of the brake pressure by a brake control unit. An example of a change in the brake pressure by the brake control unit when the speed change range is changed from the travel range to the N range while the engine is automatically stopped in a state where there is an inclination on the road surface where the vehicle is stopped is shown. It is a time chart. It is a flowchart which shows the control action by the brake control unit in the case of an engine automatic stop.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a vehicle idle stop control device according to an embodiment of the present invention. The idle stop control device includes an engine control unit 1 that controls an engine of a vehicle equipped with an automatic transmission, and a vehicle wheel 4 (left and right front wheels and left and right rear wheels (FIG. 2)), and a brake control unit 2 as an automatic brake control means of the present invention. Both the control units 1 and 2 exchange information with each other. In the present embodiment, the engine control unit 1 and the brake control unit 2 are provided separately. However, a single control unit that plays both roles may be provided.

  The engine control unit 1 includes an engine speed sensor 11 for detecting the engine speed, a vehicle speed sensor 12 for detecting the traveling speed of the vehicle, an inhibitor switch 13 for detecting the shift range of the automatic transmission, and a vehicle position. A signal is input from a gravity sensor 14 for detecting the inclination of the road surface and other sensors (not shown) necessary for engine control. Further, the brake control unit 2 receives signals from the first and second brake pressure sensors 17 and 18.

  The engine control unit 1 determines the operating state of the engine based on the input signal during engine operation, and controls the fuel injection amount and fuel injection timing by the injector 21 according to the operating state. The ignition timing is controlled by the spark plug 22, and the engine is automatically stopped (idle stop) and restarted as described later.

  The brake control unit 2 inputs a later-described holding command signal transmitted from the engine control unit 1 and signals from the first and second brake pressure sensors 17, 18, and each later-described hydraulic pressure supply unit 3 Operation control of the solenoid valves 43 to 46 and the pump 50 is performed.

  As shown in FIG. 2, the brake pedal 31 that the passenger of the vehicle depresses operates a master cylinder 33 via a master back 32. The master cylinder 33 is connected to a wheel cylinder 36 provided on a brake caliper 35 of each wheel 4 through the hydraulic pressure supply unit 3.

  The hydraulic pressure supply unit 3 is provided with hydraulic pressure supply lines 41 for front wheels and rear wheels, and one end of each hydraulic pressure supply line 41 is connected to the master cylinder 33. A first brake pressure sensor 17 that detects a brake pressure caused by depression of the brake pedal 31 is disposed on the one end side of the hydraulic pressure supply line 41 for the front wheel or the rear wheel.

  Each hydraulic pressure supply line 41 branches into a left line 41 a that supplies brake fluid to the wheel cylinder 36 of the left wheel 4 and a right line 41 b that supplies brake fluid to the wheel cylinder 36 of the right wheel 4. A common line 41c on the master cylinder 33 side of the branch point includes a first solenoid valve 43 and a first check valve 51 that allows a brake fluid to flow from the master cylinder 33 side to the wheel cylinder 36 side. They are arranged in parallel.

  In the left and right lines 41a and 41b, a second solenoid valve 44 and a second check valve 52 that allows the flow of brake fluid from the wheel cylinder 36 side to the master cylinder 33 side are arranged in parallel, respectively. It is installed. Further, between the second solenoid valve 44 and the wheel cylinder 36 in the left and right lines 41a and 41b, a second brake pressure sensor 18 for detecting a brake pressure for the wheel 4 is disposed.

  A branch path 48 branches from a portion of the common line 41 c closer to the master cylinder 33 than the first solenoid valve 43, and this branch path 48 is connected to a reservoir tank 49. In this branch path 48, in order from the master cylinder 33 side, a third solenoid valve 45, and a third check valve 53 that allows the flow of brake fluid from the reservoir tank 49 side to the third solenoid valve 45 side, Are connected in series.

  The portion of the left line 41a closer to the branch point than the second solenoid valve 44 and the portion of the branch path 48 between the third solenoid valve 45 and the third check valve 53 cause the pump 50 to flow. Connected through. The suction side and the discharge side of the pump 50 are respectively provided with fourth and fifth check valves 54 and 55 for preventing the reverse flow of the brake fluid. By the operation of the pump 50, the brake fluid is supplied to the reservoir tank 49. To the left and right lines 41a and 41b.

  Further, a portion between the second solenoid valve 44 and the wheel cylinder 36 in the left line 41a and a portion between the third check valve 53 and the reservoir tank 49 in the branch path 48 constitute a fourth solenoid valve. 46 is connected. Similarly, a portion between the second solenoid valve 44 and the wheel cylinder 36 in the right line 41b and a portion between the third check valve 53 and the reservoir tank 49 in the branch path 48 are the fourth. The solenoid valve 46 is connected.

  The first and second solenoid valves 43 and 44 are in an open state when not energized, and can be closed when energized. These solenoid valves 43 and 44 can also change an opening degree continuously. Hereinafter, the closed state of the first and second solenoid valves 43 and 44 refers to a completely closed state. The third and fourth solenoid valves 45 and 46 are in a closed state (completely closed state) in a non-energized state, and can be opened by energization.

  The brake control unit 2 controls the opening / closing operation of the solenoid valves 43 to 46 of the hydraulic pressure supply unit 3 to open or close the solenoid valves 43 to 46 and to operate the pump 50. To control. By controlling the operation of the solenoid valves 43 to 46 and the pump 50, the brake pressure for the wheel 4 (brake pressure detected by the second brake pressure sensor 18) is controlled. Normally, all the solenoid valves 43 to 46 are in a non-energized state and the pump 50 is in a non-operating state. At this time, the brake pressure (detected by the first brake pressure sensor 17) due to depression of the brake pedal 31 is established. Brake pressure) is supplied to the wheel cylinder 36 of each wheel 4. That is, the brake pressure applied to the wheels 4 is the same as the brake pressure generated when the brake pedal 31 is depressed.

  On the other hand, when the first solenoid valve 43 is closed while the brake pedal 31 is depressed, and the other valves remain normal (non-energized state), the brake pressure applied to the wheels 4 is the first pressure. The brake pressure due to depression of the brake pedal 31 immediately before the solenoid valve 43 is closed is maintained. Even if the amount of depression of the brake pedal 31 is reduced from the immediately preceding depression state, the brake pressure on the wheel 4 does not change. On the other hand, since the brake fluid flows from the master cylinder 33 to the wheel cylinder 36 via the first check valve 51 when the depression amount of the brake pedal 31 is increased from the immediately preceding depression state, the brake pressure on the wheel 4 is reduced to the brake pressure. Although it becomes the same as the brake pressure by depressing the pedal 31, when the depressing amount becomes smaller again, the brake pressure by the depressing immediately before that is maintained. Therefore, the brake pressure for the wheel 4 is the maximum value of the brake pressure due to the depression of the brake pedal 31 from the time when the first solenoid valve 43 is closed to the present time (strictly speaking, the maximum value in consideration of errors and the like). Or a value in the vicinity thereof).

  When the first solenoid valve 43 is in the closed state, the brake control unit 2 controls the brake pressure for the wheels 4 by controlling the operation of the second and fourth solenoid valves 44 and 46 and the pump 50. That is, the operations of the second and fourth solenoid valves 44 and 46 and the pump 50 are controlled (feedback control) so that the brake pressure detected by the second brake pressure sensor 18 becomes a desired value.

  When the brake pedal 31 is depressed and the vehicle stops when the shift range of the automatic transmission of the vehicle is set to the travel range (D range or R range), the engine control unit 1 Is automatically stopped. Strictly speaking, the engine control unit 1 raises a holding command signal for instructing the brake control unit 2 to execute holding control of the brake pressure from Lo to Hi before the automatic stop of the engine. When the holding execution signal (G1 signal in FIG. 6) indicating that the holding of the brake pressure has been executed is received from the brake control unit 2, the engine automatic stop control is started.

  Specifically, the engine control unit 1 detects the brake pressure (brake control unit) detected by the first brake pressure sensor 17 in a state where the inhibitor switch 13 detects that the shift range is in the D range or the R range. 2 is input to the engine control unit 1 through 2), the vehicle pressure sensor 14 detects that the pressure is equal to or higher than a preset set pressure and that the vehicle speed is 0 (including the case where it can be considered to be 0). When the holding command signal is transmitted to the brake control unit 2 and the holding execution signal G1 is received from the brake control unit 2, the engine automatic stop control is started. The fuel injection and ignition by the spark plug 22 are stopped.

  The brake control unit 2 that has received the holding command signal that has risen to Hi executes brake pressure holding control. That is, the first solenoid valve 43 of the hydraulic pressure supply unit 3 is changed from a non-energized state to a closed state by energization. Thus, during the automatic stop of the engine, the brake pressure applied to the wheels 4 is maintained at the maximum value of the brake pressure caused by the depression of the brake pedal 31 from the start of the automatic stop to the current value or a value in the vicinity thereof. The brake control unit 2 continues to transmit the holding execution signal G1 to the engine control unit 1 when the brake pressure holding control is being executed.

  The engine control unit 1 determines that the brake pressure detected by the first brake pressure sensor 17 during the automatic stop of the engine (the shift range is maintained without changing the setting to the N range) When the value is equal to or lower than a preset value (a value that can be regarded as the depression of the brake pedal 31 being released, for example, 0.35 MPa), it is assumed that the vehicle occupant has an intention to start. Initiate restart.

  At this time, the brake control unit 2 continues to hold the brake pressure. Then, when the brake pressure detected by the first brake pressure sensor 17 becomes equal to or lower than a predetermined value lower than the set value, the brake control unit 2 detects the second and fourth solenoid valves 44, 46, and By controlling the operation of the pump 50, the brake pressure for the wheel 4 (the brake pressure detected by the second brake pressure sensor 18) is reduced to a first predetermined pressure (corresponding to the “predetermined pressure” in the present invention). The predetermined value is a value that can be regarded as the depression of the brake pedal 31 being released, similarly to the set value, but in this embodiment, a value slightly lower than the set value (for example, 0.30 MPa). To do. That is, the start timing of the decrease of the brake pressure to the first predetermined pressure is set later than the restart timing of the engine. By so doing, the brake pressure drop on the wheels 4 is delayed as much as possible, and the movement of the vehicle accompanying the restart of the engine is suppressed.

  As shown in FIG. 3, the first predetermined pressure is set in accordance with the slope of the road surface on which the vehicle is stopped, and the wheel 4 (drive wheel) when the stop position of the vehicle is uphill. Is a pressure that can hold the vehicle stopped in a state where the driving force is not applied to the vehicle (a state where the engine is stopped or a state where the shift range is in the N range even when the engine is started). This is a pressure that can hold the vehicle stopped in a state where a driving force (creep force) is applied to the wheels 4 (driving wheels) (in a state where the engine is started and the shift range is in the D range). Further, when the road surface is flat or nearly flat, the first predetermined pressure is constant, but is set to a pressure at which the vehicle does not jump out at the time of restart. Thereby, even if the brake pressure with respect to the wheels 4 is reduced to the first predetermined pressure, the vehicle does not move with the restart of the engine. In consideration of this, it is not always necessary to set the timing for starting the brake pressure to decrease to the first predetermined pressure later than the timing for starting the engine restart. However, it is preferable to do so from the viewpoint of more reliably holding the vehicle stopped.

  Here, from the above automatic stop condition (the brake pressure detected by the first brake pressure sensor 17 is equal to or higher than the set pressure), the brake pressure for the wheel 4 during the automatic stop of the engine is equal to or higher than the set pressure. . This set pressure is a pressure lower than the first predetermined pressure, but is a value close to the first predetermined pressure, and is usually a pressure that can hold the stop of the vehicle similarly to the first predetermined pressure. . For this reason, it is conceivable that the first predetermined pressure is the same as the set pressure, but the first predetermined pressure is set higher than the set pressure in order to more reliably suppress the movement of the vehicle in consideration of errors and the like. ing. Thereby, the brake pressure with respect to the wheel 4 immediately before changing to a 1st predetermined pressure may be more than the said setting pressure and below a 1st predetermined pressure. However, this set pressure is a value close to the first predetermined pressure, and normally, when the vehicle is stopped, the brake pedal 31 is normally depressed more than the depression amount corresponding to the set pressure. In some cases, the brake pressure on the wheel 4 immediately before changing to the first predetermined pressure is normally considered to be higher than the first predetermined pressure. Therefore, when the brake pressure detected by the first brake pressure sensor 17 becomes equal to or lower than a predetermined value, the brake pressure for the wheel 4 is normally reduced to the first predetermined pressure. If the brake pressure for the wheel 4 immediately before the change to the first predetermined pressure is not less than the set pressure and not more than the first predetermined pressure, the brake pressure detected by the first brake pressure sensor 17 is predetermined. The brake pressure for the wheel 4 is not changed even if the value becomes lower than the value. Even in this case, it is normally possible to hold the stop of the vehicle.

  The brake control unit 2 executes release control for releasing the brake pressure on the wheels 4 after completion of the reduction of the brake pressure to the first predetermined pressure. In the present embodiment, the release control is executed after the completion of the reduction of the brake pressure to the first predetermined pressure and when a predetermined period has elapsed from the complete explosion of the engine that has been started as described above. The complete explosion determination of the engine is performed in the engine control unit 1 based on the signal from the engine speed sensor 11, and when it is determined that the complete explosion has occurred, the complete explosion signal is sent from the engine control unit 1 to the brake control unit 2. Is sent. The predetermined period is set to a period (time) in which the engine speed is stable and a stable driving force is transmitted from the engine to the wheels 4. The brake control unit 2 holds the first predetermined pressure after completion of the reduction of the brake pressure to the first predetermined pressure and until a predetermined period elapses after the complete explosion of the engine.

  The brake control unit 2 gradually reduces the brake pressure applied to the wheels 4 when the brake pressure is released. Specifically, it is changed linearly from the first predetermined pressure to 0 at time T. As shown in FIG. 4, this time T is set in accordance with the degree of inclination of the road surface on which the vehicle is stopped, and the vehicle suddenly jumps out or has a start regardless of the inclination of the road surface. The time is set so that there is no such thing. The vehicle starts until the brake pressure becomes zero. However, if the road slope does not change, the rate of decrease in the brake pressure does not change, so the start timing of the vehicle is stabilized.

  When the brake pressure is released, the brake control unit 2 transmits a releasing signal (G2 signal in FIG. 6) to the engine control unit 1 instead of the holding execution signal G1, and when the releasing is completed, the releasing signal Instead of G2, a non-holding signal (G3 signal in FIG. 6) is transmitted to the engine control unit 1. In addition, when the release is completed, the brake control unit 2 stops energization of the first solenoid valve 43 and opens the first solenoid valve 43. When receiving the non-holding signal G3, the engine control unit 1 causes the holding command signal to fall from Hi to Lo.

  Here, when the depression of the brake pedal 31 is released during the automatic stop of the engine, it is assumed that the occupant intends to start. However, for example, the occupant may go out of the vehicle. However, normally, by the time the occupant tries to get out of the vehicle, the engine starts, the brake pressure is released, and the vehicle starts. On the other hand, if it takes time to start the engine and a complete explosion signal is not easily transmitted from the engine control unit 1 to the brake control unit 2, the occupant may be able to get out of the vehicle. Therefore, the brake control unit 2 performs a first setting period (a period until the release control is normally performed) from when the brake pressure detected by the first brake pressure sensor 17 becomes a predetermined value or less. If the release control is not executed even after a period (time) that is longer than (time) and the occupant cannot go out of the vehicle (for example, 2 s), the brake pressure for the wheels 4 is gradually released. Executes slow release control. This slow release control is the same as the release control described above, but changes linearly from the first predetermined pressure to 0 in a time longer than the time T of the release control (it may be a fixed time regardless of the road surface inclination). Let As a result, even if the occupant tries to get out of the vehicle, the vehicle starts to move slowly, and immediately notices that.

  FIG. 6 shows an example of a change in brake pressure by the brake control unit 2. The brake pressure indicated by the solid line is the brake pressure applied to the wheel 4 (the brake pressure detected by the second brake pressure sensor 18), and the brake pressure indicated by the broken line is the brake pressure (first brake) caused by the depression of the brake pedal 31. Brake pressure detected by the pressure sensor 17). As shown in FIG. 6, at time t1, the holding command signal from the engine control unit 1 rises from Lo to Hi, whereby the brake control unit 2 starts holding control of the brake pressure (first solenoid valve 43 And the holding execution signal G1 is transmitted to the engine control unit 1 (in FIG. 6, the transmission timing of the holding execution signal G1 is depicted slightly shifted from the time t1 to the rear, but the transmission timing is It can be regarded as the same as time t1). The engine control unit 1 receives this holding execution signal G1 and starts control of automatic engine stop, and eventually the engine speed becomes zero.

  From the start of the holding control to the time t2, the brake pressure on the wheel 4 is held at the maximum value of the brake pressure by the depression of the brake pedal from the start of the automatic stop to the present time or a value in the vicinity thereof. Thereby, even if the depression amount of the brake pedal 31 (brake pressure by depression of the brake pedal 31) becomes small, the brake pressure with respect to the wheel 4 does not change. On the other hand, when the brake pedal 31 is stepped on, the brake pressure for the wheel 4 also increases according to the amount of depression.

  Then, before the time t2, the release of the depression of the brake pedal 31 is started, and the brake pressure due to the depression of the brake pedal 31 rapidly decreases (the brake pressure for the wheel 4 is also the maximum value or the The brake pressure becomes equal to or less than a predetermined value at time t2. Thereby, the brake pressure with respect to the wheel 4 is reduced to the first predetermined pressure, and is maintained at the first predetermined pressure until time t3.

  Note that immediately before time t2, the brake pressure detected by the first brake pressure sensor 17 becomes equal to or lower than the set value, so the engine control unit 1 starts the engine restart control, and the engine speed increases over time. Begin to.

  After completion of the reduction of the brake pressure to the first predetermined pressure, a complete explosion signal is received from the engine control unit 1, and at a time t3 when a predetermined period has elapsed from that time, release control is started and a release signal G2 is sent to the engine. Transmit to the control unit 1. At time t4 (= t3 + T), the brake pressure for the wheel 4 becomes 0, the release control is stopped, the energization to the first solenoid valve 43 is stopped, and the non-holding signal G3 is transmitted to the engine control unit 1. . In response to this non-holding signal G3, the engine control unit 1 lowers the holding command signal from Hi to Lo (in FIG. 6, the falling timing from Hi to Lo is depicted slightly shifted from time t4 to the back). The fall timing can be regarded as the same as time t4).

  Here, the shift range is changed from the travel range to the N range while the engine is automatically stopped in a state where there is an inclination on the road surface where the vehicle is stopped (upward or downward slope is greater than 4%, for example). In this state, when the brake pressure detected by the first brake pressure sensor 17 becomes equal to or lower than the predetermined value, the brake pressure for the wheel 4 is reduced to the second predetermined pressure. As shown in FIG. 5, the second predetermined pressure is set in accordance with the degree of inclination of the road surface on which the vehicle is stopped, and can suppress the movement of the vehicle in the state where the shift range is the N range. Minimum pressure (a value lower than the first predetermined pressure and slightly lower than the set pressure). In the state in the N range, the engine is not restarted even if the brake pressure detected by the first brake pressure sensor 17 falls below the set value.

  Then, when the brake pressure detected by the first brake pressure sensor 17 becomes equal to or lower than the predetermined value, the second predetermined pressure is maintained until a predetermined second setting period elapses. Wait for the range to shift to the driving range. The second set period is a period (time) shorter than the first set time, and the passenger accidentally releases the depression of the brake pedal 31 first to try to start. In this case, the period is set to a period (time) longer than the period (time) from the release to the change of setting to the travel range. In addition, the second set period is a period (time) in which the occupant may intentionally move the vehicle to the N range on a slope, so that the brake is not noticed as much as possible. Set to Considering these, the second setting period is set to 300 ms, for example.

  If the setting is not changed to the travel range while the second predetermined pressure is maintained, the brake control unit 2 executes the same slow release control as when the travel range is maintained. As a result, the occupant can move the vehicle to the N range on the slope.

  On the other hand, if the setting is changed to the travel range while the second predetermined pressure is being maintained, the engine control unit 1 restarts the engine and the brake control unit 2 assumes that the intention to start is certain. Extends the second set period for maintaining the second predetermined pressure. In the present embodiment, the second setting period is set to the maximum period (for example, 2 s) as the first setting period. Then, when a complete explosion signal is transmitted from the engine control unit 1 to the brake control unit 2 and a predetermined period elapses after the complete explosion of the engine, the brake pressure is reduced at the same reduction rate as when the traveling range is maintained. Release control (the brake pressure at the start of release control is the second predetermined pressure) is executed. Normally, the release control start timing is reached until the maximum extension of the second set period elapses (the extension of the second set period ends at the release control start timing). When the control start timing is not reached, the slow release control is executed when the second set period extended to the maximum has elapsed.

  That is, in a vehicle that automatically stops the engine as in this embodiment, even if the shift range is immediately changed from the N range to the travel range with the brake pedal 31 depressed, the engine is automatically stopped. Unlike a normal AT vehicle that does not perform, the driving force is not transmitted to the wheel 4 immediately. Therefore, when the brake pedal 31 is released, the brake pressure on the wheel 4 is not released immediately. In this state, the vehicle is restrained from moving, and in that state, waits for the setting to be changed to the travel range. If the setting is changed to the travel range and the intention to start is certain, the second predetermined pressure is maintained. By extending the second setting period to be performed, it is possible to perform a smooth start while suppressing the movement of the vehicle as it is. On the other hand, when the setting is not changed to the travel range, the second predetermined pressure is a relatively low pressure, so that the brake pressure can be released quickly, whereby the occupant moves the vehicle to the N range intentionally on the slope. In this case, the vehicle can be moved smoothly.

  When the engine is automatically stopped in a state where there is no slope on the road surface where the vehicle is stopped (a state where the uphill or downhill slope is assumed to be flat, for example, 4% or less), the shift range is changed from the running range to the N range. In this state, when the brake pressure detected by the first brake pressure sensor 17 becomes equal to or lower than the predetermined value, the road surface is inclined without being reduced to the second predetermined pressure. The same slow release control (the brake pressure at the start of the slow release control is different from the case where there is an inclination on the road surface, but the reduction rate is the same) is executed. Even when there is no slope on the road surface, the same control as when the road surface has a slope may be performed.

  FIG. 7 shows the brake pressure applied by the brake control unit 2 when the shift range is changed from the travel range to the N range while the engine is automatically stopped in a state where there is a slope on the road surface where the vehicle is stopped. An example of the change is shown.

  At time t11, the holding command signal from the engine control unit 1 rises from Lo to Hi, whereby the brake control unit 2 starts holding control of the brake pressure (the first solenoid valve 43 is closed by energization). The holding execution signal G1 is transmitted to the engine control unit 1 (in FIG. 7, the transmission timing of the holding execution signal G1 is depicted with a slight shift from the time t11 to the rear, but the transmission timing is assumed to be the same as the time t11. Can do that). The engine control unit 1 receives this holding execution signal G1 and starts control of automatic engine stop, and eventually the engine speed becomes zero.

  From the start of the holding control to the time t12, the brake pressure for the wheel 4 is held at the maximum value of the brake pressure by the depression of the brake pedal from the start of the automatic stop to the present time or a value in the vicinity thereof. During this time, the shift range is changed from the D range to the N range.

  At time t12, release of the brake pedal 31 releases the brake pressure caused by the depression, and the brake pressure on the wheel 4 is reduced to the second predetermined pressure.

  The shift range is changed from the N range to the D range at time t13 from the time when the brake pressure due to the depression of the brake pedal 31 becomes equal to or lower than the predetermined value until the second set period (value before extension) elapses. As a result, the engine control unit 1 starts the engine restart process, and eventually the engine speed starts to increase. Further, the second set period is extended and the second predetermined pressure is maintained.

  Thereafter, upon receipt of a complete explosion signal from the engine control unit 1, release control is started and a release signal G2 is transmitted to the engine control unit 1 at time t14 when a predetermined period has passed. At time t15, the brake pressure for the wheel 4 becomes 0, the release control is stopped, the energization to the first solenoid valve 43 is stopped, and the non-holding signal G3 is transmitted to the engine control unit 1. The engine control unit 1 receives the non-holding signal G3 and lowers the holding command signal from Hi to Lo (in FIG. 7, the falling timing from Hi to Lo is slightly shifted from time t14 to the back). The fall timing can be regarded as the same as time t14).

  Here, the control operation by the brake control unit 2 during the automatic stop of the engine will be described based on the flowchart of FIG.

  In the first step S1, it is determined whether or not the brake pressure holding control is being performed, that is, whether or not the holding execution signal G1 is being transmitted to the engine control unit 1. When the determination in step S1 is NO, the process returns as it is, while when the determination is YES, the process proceeds to step S2.

  In step S2, it is determined whether or not the brake pressure detected by the first brake pressure sensor 17 is equal to or less than the predetermined value. If the determination in step S2 is NO, the process returns as it is, while if the determination is YES, the process proceeds to step S3.

  In step S3, it is determined whether or not the shift range is the N range or the P range. When the determination in step S3 is NO (when it is the travel range), the process proceeds to step S4. When the determination is YES, the process proceeds to step S10.

  In step S4, it is determined whether or not the brake pressure detected by the second brake pressure sensor 17 is higher than the first predetermined pressure. When the determination in step S4 is YES, the process proceeds to step S5 to execute a pressure reduction process for reducing the brake pressure on the wheel 4 to the first predetermined pressure, and then proceeds to step S6. On the other hand, when the determination in step S4 is NO (when the process proceeds to step S4 after passing through steps S10 to S12 described later, the second predetermined pressure is lower than the first predetermined pressure. Even if the determination is NO and the steps S10 to S12 are not performed, as described above, the brake pressure for the wheel 4 may be equal to or higher than the set pressure and equal to or lower than the first predetermined pressure. If the determination in step S4 is NO), the process proceeds directly to step S6.

  In step S6, it is determined whether or not the first set period has elapsed since the brake pressure detected by the first brake pressure sensor 17 has become a predetermined value or less. When the determination in step S6 is NO, the process proceeds to step S7 to determine whether or not a predetermined period has elapsed since the complete explosion of the engine. If the determination in step S7 is NO, the process returns as it is. On the other hand, if the determination in step S7 is YES, the process proceeds to step S8 to execute release control, and then returns. On the other hand, when the determination in step S6 is YES, the process proceeds to step S9 to execute the slow release control, and then returns.

  In step S10 that proceeds when the determination in step S3 is YES, whether or not the road surface on which the vehicle is stopped is inclined, that is, the absolute value of the gradient detected by the gravity sensor 14 is, for example, greater than 4%. Determine whether it is larger. When the determination in step S10 is YES, the process proceeds to step S11. When the determination is NO, the process proceeds to step S13.

  In step S11, a pressure reduction process for reducing the brake pressure on the wheel 4 to the second predetermined pressure is executed, and in the next step S12, the brake pressure detected by the first brake pressure sensor 17 becomes a predetermined value or less. It is determined whether or not the second set period has elapsed since then. If the determination in step S12 is NO, the process returns as it is. If the determination is YES, the process proceeds to step S13.

  In step S13, the slow release control is executed, and then the process returns.

  When the brake pressure is reduced to a predetermined value or less due to the release of the brake pedal 31 by the release of the brake pedal 31 from the start of the brake pressure holding control by the control by the brake control unit 2, the brake pressure applied to the wheels 4 is reduced. Decreases to the first predetermined pressure, and after that, when a predetermined period elapses after the complete explosion of the engine, the brake pressure for the wheels 4 is released. The brake pressure immediately before the release always becomes the first predetermined pressure regardless of the depression amount of the brake pedal 31 at the time of automatic stop, and the brake pressure for the wheels 4 gradually decreases from the first predetermined pressure. As a result, the behavior at the start of the vehicle can be stabilized regardless of the depression amount of the brake pedal 31 when the engine is automatically stopped. Therefore, it is possible to always give a good start feeling to the vehicle occupant.

  Further, during the automatic stop of the engine in a state where the vehicle is stopped and the road surface is inclined, the shift range is changed from the travel range to the N range, and in this state, the first brake pressure sensor 17 detects the shift range. When the applied brake pressure becomes equal to or lower than the predetermined value, the brake pressure for the wheel 4 is reduced to the second predetermined pressure. The second predetermined pressure is held from when the brake pressure detected by the first brake pressure sensor 17 becomes a predetermined value or less until the second set period elapses. When the shift range is changed to the travel range while the second predetermined pressure is maintained, the second setting period for maintaining the second predetermined pressure is extended (the second setting period is It is changed to the “first setting period” in step S6 (for example, 300 ms is changed to a maximum of 2 s). Normally, the release control timing is reached until the maximum second set period elapses. On the other hand, when the setting is not changed to the travel range while the second predetermined pressure is maintained (until the second set period before extension elapses), the slow release control is executed. Therefore, even if the occupant tries to start on a slope and accidentally releases the brake pedal first, if the vehicle is changed to the travel range immediately thereafter, the vehicle can start smoothly without moving. . In addition, when the occupant intentionally moves the vehicle to the N range on a slope, the vehicle can be moved smoothly.

  Further, in the above embodiment, the second brake pressure sensor 18 is provided, the first solenoid valve 43 is closed, and the brake pressure for the wheel 4 is feedback controlled. Without providing the sensor 18, the brake pressure for the wheel 4 may be estimated and controlled by feedforward control (open loop control) based on opening / closing amount (opening) control of the first solenoid valve 43.

  The present invention automatically stops the engine of the vehicle when the brake pedal is depressed and the vehicle stops when the shift range of the automatic transmission of the vehicle is set to the traveling range, and the brake pedal is depressed. This is useful for an idle stop control device for a vehicle in which the engine is restarted when the engine is released.

1 Engine control unit 2 Brake control unit (automatic brake control means)
4 Wheel 17 First brake pressure sensor 18 Second brake pressure sensor 31 Brake pedal

Claims (6)

When the brake pedal is depressed with the shift range of the automatic transmission of the vehicle set to the traveling range and the vehicle stops, the engine of the vehicle is automatically stopped and the depression of the brake pedal is released. Sometimes, an idle stop control device for a vehicle that restarts the engine,
During the automatic stop of the engine, an automatic control is performed so that the brake pressure for the wheels of the vehicle is maintained at or near the maximum value of the brake pressure due to the depression of the brake pedal from the start of the automatic stop to the present time. With brake control means,
The automatic brake control means reduces the brake pressure for the wheel to a predetermined pressure when the brake pressure due to the depression becomes equal to or less than a predetermined value by releasing the depression of the brake pedal, and for the wheel after the completion of the reduction. A vehicle idle stop control device configured to release brake pressure. In the vehicle idle stop control device according to claim 1,
The vehicle idle stop control device, wherein the automatic brake control means is configured to gradually reduce the brake pressure when the brake pressure is released. The idle stop control device for a vehicle according to claim 1 or 2,
An idle stop control device for a vehicle, characterized in that a start timing of the brake pressure to be lowered to the predetermined pressure by the automatic brake control means is later than a restart start timing of the engine. In the vehicle idle stop control device according to any one of claims 1 to 3,
The automatic brake control means is configured to release the brake pressure after completion of a decrease in the brake pressure to the predetermined pressure and when a predetermined period has elapsed since the complete explosion of the engine. A vehicle idle stop control device. In the idle stop control device for a vehicle according to any one of claims 1 to 4,
The predetermined pressure is a pressure capable of holding the vehicle stopped when the driving position is not applied to the wheels when the vehicle is stopped uphill, and a creep force is applied to the wheels when the vehicle is downhill. A vehicle idle stop control device characterized in that the pressure is sufficient to hold the vehicle stop. The idle stop control device for a vehicle according to claim 5,
The idle stop control device for a vehicle, wherein the predetermined pressure is set according to a degree of inclination of a road surface on which the vehicle is stopped.

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