JP3956810B2 - Engine start control device for idle stop vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine start control device for an idle stop vehicle, and more particularly to a technique for improving responsiveness at the time of automatic engine restart.
[0002]
[Prior art]
In recent years, in order to purify exhaust gas and improve fuel efficiency, the engine is automatically stopped while the vehicle is temporarily stopped, such as waiting for an intersection. An idle stop vehicle that performs a restart is attracting attention. Patent Document 1 discloses a technique for automatically restarting the engine when it is determined that the preceding vehicle ahead of the host vehicle has started while the engine is automatically stopped.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-73808
[Problems to be solved by the invention]
In such an idle stop vehicle, it is necessary to automatically restart the engine appropriately in accordance with the driving conditions in order to start the vehicle quickly from the engine automatic stop state. In the above-mentioned Patent Document 1, a technique for automatically restarting the engine when it is determined that the preceding vehicle has started is disclosed. However, the automatic engine restart is essentially a reduction in brake pedal force. It should be determined based on the driver's intention to start, and further improvements are desired. In addition, when a three-phase AC type induction motor is used as a motor for driving the engine at the time of automatic restart of the engine, more time is required for exciting the induction motor, and this time is automatically restarted of the engine. This contributes to a decrease in responsiveness.
[0005]
The present invention has been made in view of such problems, and effectively improves the responsiveness when the engine is automatically restarted from when the engine is automatically stopped, so that the natural starting operation close to the driver's operating feeling is achieved. The main purpose is to get a feeling.
[0006]
[Means for Solving the Problems]
An engine start control device for an idle stop vehicle according to the present invention includes a braking request value detecting means for detecting or estimating a braking request value corresponding to a brake pedal force by a driver, the vehicle is stopped, and the braking request value is at least An engine automatic stop means for automatically stopping the engine when an idle stop condition including being higher than a start threshold is satisfied, the engine being automatically stopped, and the braking request value being the start threshold An engine automatic restarting means for automatically restarting the engine by driving the engine with a motor when a starting condition including lower than the value is satisfied.
[0007]
The first aspect of the invention relates to a preceding vehicle detecting means for detecting or estimating at least one of a relative distance or a relative speed with respect to a preceding vehicle and a relative distance or relative speed between the preceding vehicle and the engine during automatic stop . Correction means for correcting the starting threshold value to the increase side based on at least one of the above.
[0008]
According to a second aspect of the present invention, when the motor is an induction motor, the engine is automatically stopped, and an excitation condition including that the braking request value is lower than an excitation threshold is satisfied, the induction motor Excitation means for starting excitation is provided, and the excitation threshold value is higher than the starting threshold value.
[0009]
【The invention's effect】
According to the first invention, the timing at which the braking request value becomes lower than the starting threshold value can be appropriately advanced based on at least one of the relative distance and the relative speed with the preceding vehicle. Accordingly, the responsiveness of the start timing of the engine automatic restart based on the above can be appropriately improved according to the start operation of the preceding vehicle.
[0010]
According to the second invention, when the engine is automatically restarted from the engine automatic stop state, the excitation of the induction motor is started before the engine is actually restarted. The time required can be shortened or omitted, and the responsiveness of the automatic engine restart can be improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to illustrated embodiments. FIG. 1 is a system configuration diagram schematically showing an idle stop vehicle to which an engine start control device according to the present invention is applied. This vehicle uses both the engine 10 and the motor generator 12 as a vehicle driving source. In this embodiment, the motor generator 12 is directly connected to the crankshaft of the engine 10, and more specifically, the crankshaft of the engine 10 and the rotor of the motor generator 12 are disposed coaxially and are substantially integrated. Rotate. A clutch may be interposed between the crankshaft of engine 10 and the rotor of motor generator 12. Moreover, the structure which connects the crankshaft of the engine 10 and the rotor of the motor generator 12 via a suitable transmission belt may be sufficient. The motor generator 12 is a three-phase AC type induction motor capable of both a power running operation and a regenerative operation, and stores and discharges the battery 16 via an inverter (not shown) and the power control unit 14.
[0012]
The rotor, that is, the output shaft of the motor generator 12 is connected to an axle 22 having driving wheels 20 via a torque converter 19 and an automatic transmission 18. The automatic transmission 18 may be a known stepped transmission having a plurality of planetary gear mechanisms, or may be a toroidal or belt type continuously variable transmission.
[0013]
The brake device 23 includes a brake disc 24 provided on the axle 22, a brake caliper 26 that sandwiches the brake disc 24 and applies brake torque, and a hydraulic braking force control actuator 28 that drives the brake caliper 26. And a braking force control unit 30 for controlling the braking force control actuator 28. The brake device 23 includes a master cylinder 52 that converts the depression force of the brake pedal 50 into the pressure of the brake fluid, that is, the brake fluid pressure. The master cylinder 52 corresponds to the depression force of the brake pedal 50 by the driver. A hydraulic pressure sensor (braking required value detection means) 54 for detecting the brake hydraulic pressure as the braking required value is provided.
[0014]
The start control unit 32 detects the brake switch 34 that detects ON / OFF of the brake pedal 50, the accelerator opening sensor 36 that detects the opening including the ON / OFF of the accelerator pedal, and the rotational speed of the engine 10. A rotation sensor 38, a water temperature sensor 40 that detects a water temperature as an engine temperature, a negative pressure sensor 42 that detects an intake negative pressure of the engine, a radar that detects a relative distance, that is, an inter-vehicle distance, of a preceding vehicle ahead of the host vehicle On the basis of detection signals from various sensors such as an inter-vehicle sensor (preceding vehicle detection means) 44, the brake hydraulic pressure sensor 54, and the like, signals are input / output to / from the power control unit 14 and the braking force control unit 30. The engine automatic restart control described later is performed. These control units 14, 30, and 32 are well-known microcomputer systems having a CPU, a RAM, a ROM, and an input / output interface, and have functions for storing and executing various control processes.
[0015]
FIG. 2 is a flowchart showing a control flow that is a main part of the present embodiment, and is repeatedly executed by the start control unit 32 every predetermined period (for example, every 10 ms). FIG. 3 is a time chart showing the automatic restart operation from the idle stop, where (a) is corrected by the preceding vehicle, and (b) is not corrected by the preceding vehicle. It corresponds to.
[0016]
First, with reference to FIG. 2 and FIG. 3A, an operation when the engine is automatically restarted without correction by the preceding vehicle will be described.
[0017]
In this vehicle, when a predetermined idle stop condition is satisfied, the engine is automatically stopped, that is, idle stop is performed by stopping the fuel injection of the engine 10 (engine automatic stop means). The idle stop condition described above is that the vehicle speed is almost zero, that is, the vehicle is stopped, the brake switch 34 is ON, that is, the brake pedal 50 is depressed, and the depression force (braking) (Required value) is sufficiently high (specifically, the brake fluid pressure is at least higher than a starting threshold value Pmc_strt and an excitation threshold value Pmc_stml, which will be described later), and the charged amount (SOC) of the battery 16 is a predetermined allowable value. It is above the value.
[0018]
In S (step) 1, it is determined whether an idle stop is being performed. If a predetermined excitation condition is satisfied during the idle stop, the process proceeds to S10 and the motor generator 12 is excited (excitation means). This excitation condition includes that the brake fluid pressure detected by the brake fluid pressure sensor 54 in S7 is lower than the excitation threshold (threshold value) Pmc_stml (S9). This excitation threshold value Pmc_stml is fixed to a preset excitation reference value Pbsmc_stml unless correction by a preceding vehicle, which will be described later, is made.
[0019]
Thereafter, when a predetermined start condition is satisfied during idling stop, the process proceeds to S13, and the engine is automatically restarted (engine automatic restarting means). Specifically, the engine 10 is driven by the motor generator 12 to crank the engine 10, and when the engine speed reaches a predetermined idle speed, fuel injection is resumed. The start condition includes not only idling stop (S1), brake fluid pressure lower than start threshold value Pmc_strt (S8), and excitation completed (S12). The starting threshold value Pmc_strt is fixed to a preset starting reference value Pbsmc_strt unless correction based on the inter-vehicle distance and relative speed with the preceding vehicle described later is performed. The starting reference value Pbsmc_str is A value lower than the excitation reference value Pbsmc_stml is set. The determination of excitation in S12 can be made based on the value of a timer that measures the excitation duration, for example. This timer value is updated in S11 every time excitation is performed in S10, and is reset in preparation for the next automatic engine restart when the engine automatic restart in S13 is completed, for example, when a complete explosion determination is made. (S14).
[0020]
Since the excitation threshold value Pmc_stml is higher than the start threshold value Pmc_strt, when the driver returns the brake pedal during idle stop to restart the brake, the brake fluid pressure is set to the start threshold value Pmc_strt. First, the excitation threshold value is lower than the excitation threshold Pmc_stml, and excitation is started prior to engine start. That is, since the excitation of the motor generator 12 is started before the automatic restart of the engine is started, the time required until the motor generator 12 is excited when the engine is automatically restarted thereafter is shortened or omitted. And the responsiveness of this automatic restart is improved. In the example of FIG. 3A, the time ΔT2 required only for excitation is shortened by the time ΔT1 when the brake fluid pressure decreases from the excitation threshold value Pmc_stml to the start threshold value Pmc_strt.
[0021]
FIG. 2 is a flowchart showing a control flow that is a main part of the present embodiment, and is repeatedly executed by the start control unit 32 every predetermined period (for example, every 10 ms). FIG. 3 is a time chart showing the automatic restart operation from the idle stop, where ( b ) is corrected by the preceding vehicle, and ( a ) is not corrected by the preceding vehicle. It corresponds to.
[0022]
The excitation threshold value Pmc_stml and the start threshold value Pmc_strt are corrected to the increase side based on the inter-vehicle distance and relative speed with the preceding vehicle. Specifically, in S4, based on the detection signal of the inter-vehicle sensor 44, the inter-vehicle distance and relative speed with respect to the preceding vehicle are detected. In subsequent S5, the preceding vehicle correction term Pmc_dst is calculated based on the inter-vehicle distance and the relative speed. For example, referring to a map as shown in FIG. 4, a distance correction term Pmc_dst_x based on the inter-vehicle distance and a speed correction term Pmc_dst_dx based on the relative speed are obtained separately, and the preceding vehicle correction term Pmc_dst is calculated by adding both. To do.
[0023]
[Expression 1]
Pmc_dst = Pmc_dst_x + Pmc_dst_dx
As shown in FIG. 4A, the distance correction term Pmc_dst_x is 0 when the inter-vehicle distance is smaller than the predetermined lower limit value x1, and is the maximum value when the inter-vehicle distance is larger than the predetermined upper limit value x2. In the range between the lower limit value x1 and the upper limit value x2, the correction amount is set to increase as the inter-vehicle distance increases. Similarly, as shown in FIG. 4B, the speed correction term Pmc_dst_dx is 0 when the relative speed is lower than the predetermined lower limit value dx1, and when the relative speed is higher than the predetermined upper limit value dx2. Is fixed at the maximum value, and between the lower limit value dx1 and the upper limit value dx2, the correction amount is set to increase as the relative speed increases.
[0024]
In S6, the preceding vehicle correction term Pmc_dst is added to the excitation reference value Pbsmc_stml and the start reference value Pbsmc_strt, respectively, so that the excitation threshold value Pmc_stml and the start threshold value Pmc_strt are respectively corrected and updated to the increasing side.
[0025]
[Expression 2]
Pmc_stml = Pmc_dst + Pbsmc_stml
Pmc_strt = Pmc_dst + Pbmc_strt
As described above, the excitation threshold value Pmc_stml and the start threshold value Pmc_strt are corrected to increase based on the inter-vehicle distance and relative speed with the preceding vehicle. Is appropriately advanced (ΔT3, ΔT4), and the vehicle can be quickly restarted following the preceding vehicle.
[0026]
Further, in order to suppress wasteful power consumption due to only the excitation being performed for a long time, the excitation continuation time is measured, and when this excitation continuation time exceeds a predetermined value, the excitation of the motor generator 12 is appropriately released. In addition, the correction by the preceding vehicle is cancelled. Specifically, when the value of the timer for measuring the excitation duration exceeds a predetermined value, the process proceeds from S3 to S15, and the preceding vehicle correction term Pmc_dst is reset to 0, that is, canceled. Similarly, if no preceding vehicle is detected, the process proceeds from S2 to S15, and the preceding vehicle correction term Pmc_dst is immediately reset to 0.
[0027]
As described above, the present invention has been described based on specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, in the above embodiment, both the excitation threshold value Pmc_stml and the start threshold value Pmc_strt are corrected using the preceding vehicle correction term Pmc_dst having the same value to simplify the control. You may make it correct | amend using the preceding vehicle correction | amendment term of a different value with threshold value Pmc_stml and starting threshold value Pmc_strt.
[0028]
In the above embodiment, the correction is performed based on both the relative distance and the relative speed with the preceding vehicle. However, the correction may be performed based on either one. However, considering that the relative distance from the preceding vehicle is different in the stopped state, a large relative distance from the preceding vehicle does not strictly mean that the preceding vehicle has started. However, in many cases of signal-waiting stops, the vehicle is initially stopped with a close distance between the vehicles, so that an effect can be obtained even if correction is performed based only on the relative distance from the preceding vehicle.
[0029]
Further, in the above embodiment, the braking request value by the driver is estimated from the brake fluid pressure detected by the brake fluid pressure sensor 54. However, the present invention is not limited to this, for example, based on the brake stroke detected by the brake stroke sensor. The braking request value may be estimated.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an idle stop vehicle to which an engine start control device according to an embodiment of the present invention is applied.
FIG. 2 is a flowchart showing a flow of control for automatic engine restart according to the present embodiment.
FIG. 3 is a time chart showing the operation at the time of automatic engine restart, where (a) is not corrected by a preceding vehicle, and (b) is corrected by a preceding vehicle.
4A is a control map showing the relationship between the inter-vehicle distance from the preceding vehicle and its correction term, and FIG. 4B is a control map showing the relationship between the relative speed with the preceding vehicle and its correction term.
[Explanation of symbols]
10 ... Engine 12 ... Motor generator (motor, induction motor)
44. Vehicle distance sensor (preceding vehicle detection means)
54 ... Brake hydraulic pressure sensor (braking request value detecting means)

Claims (13)

Braking request value detection means for detecting or estimating a braking request value corresponding to the brake pedal force by the driver;
An engine automatic stop means for automatically stopping the engine when the vehicle is stopped and an idle stop condition including that the braking request value is at least higher than a start threshold value is satisfied;
When the engine is automatically stopped and the start condition including that the required braking value is lower than the start threshold is satisfied, the engine is automatically restarted by driving the engine with a motor. Restart means;
A preceding vehicle detection means for detecting or estimating at least one of a relative distance or a relative speed with the preceding vehicle;
Correction means for correcting the starting threshold value to the increasing side based on at least one of a relative distance or a relative speed with respect to the preceding vehicle during the automatic stop of the engine ;
An engine start control device for an idle stop vehicle having   The engine start control device for an idle stop vehicle according to claim 1, wherein the correction means increases the increase amount of the start threshold value as the relative distance from the preceding vehicle increases.   The engine start control device for an idle stop vehicle according to claim 1, wherein the correction means increases the increase amount of the start threshold value as the relative speed with the preceding vehicle increases. The motor is an induction motor;
Further, it has excitation means for exciting the induction motor when the engine is automatically stopped and an excitation condition including that the required braking value is lower than an excitation threshold is satisfied. The value is higher than the starting threshold value,
The idle stop vehicle according to any one of claims 1 to 3, further comprising excitation correction means for correcting the excitation threshold to an increase side based on at least one of a relative distance or a relative speed with respect to the preceding vehicle. Engine start control device. Means for measuring the excitation duration of the induction motor by the excitation means;
Means for canceling the correction by the correction means and the excitation correction means when the excitation duration exceeds a predetermined value;
The engine start control device for an idle stop vehicle according to claim 4, comprising:   The engine start control device for an idle stop vehicle according to any one of claims 1 to 5, wherein the braking request value detection means estimates the braking request value from a brake fluid pressure or a brake stroke. Braking request value detection means for detecting or estimating a braking request value corresponding to the brake pedal force by the driver;
An engine automatic stop means for automatically stopping the engine when the vehicle is stopped and an idle stop condition including that the braking request value is at least higher than a start threshold value is satisfied;
An engine that automatically restarts the engine by driving the engine with an induction motor when the engine is automatically stopped and a start condition including that the required braking value is lower than the start threshold value is satisfied Automatic restart means;
Excitation means for starting excitation of the induction motor when the engine is automatically stopped and the excitation condition including that the required braking value is lower than the excitation threshold is satisfied. An engine start control device for an idle stop vehicle, wherein the threshold value is higher than the start threshold value. A preceding vehicle detection means for detecting or estimating at least one of a relative distance or a relative speed with the preceding vehicle;
Correction means for correcting the starting threshold value to the increasing side based on at least one of a relative distance or a relative speed with respect to the preceding vehicle during the automatic stop of the engine;
The engine start control device for an idle stop vehicle according to claim 7. 9. The engine start control device for an idle stop vehicle according to claim 8, wherein the correction means increases the increase amount of the start threshold value as the relative distance from the preceding vehicle increases. 9. The engine start control device for an idle stop vehicle according to claim 8, wherein the correction means increases the increase amount of the start threshold value as the relative speed with the preceding vehicle increases. The engine start of the idle stop vehicle according to any one of claims 7 to 10, further comprising excitation correction means for correcting the excitation threshold value to an increase side based on at least one of a relative distance or a relative speed with the preceding vehicle. Control device. Means for measuring the excitation duration of the induction motor by the excitation means;
Means for canceling the correction by the excitation correction means when the excitation duration exceeds a predetermined value;
The engine start control device for an idle stop vehicle according to claim 11. The engine start control device for an idle stop vehicle according to any one of claims 7 to 12, wherein the braking request value detection means estimates the braking request value from a brake fluid pressure or a brake stroke.

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