JP2006152880A - Engine automatic stop device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine automatic stop device of a vehicle capable of sufficiently improving fuel economy and emission by performing the automatic stop of the engine without causing any trouble even under such a condition that the temperature of a hydraulic oil in an automatic transmission is high. <P>SOLUTION: The power of the engine is transmitted to wheels through the automatic transmission, and a power transmission mechanism in the automatic transmission is operated by the hydraulic pressure of an oil pump driven by the engine. The engine automatic stop device is mounted on the vehicle and automatically stops the engine on an assumption that a vehicle speed is lowered less than a reference vehicle speed V1. The engine automatic stop device also monitors the temperature of the hydraulic oil in the automatic transmission and changes the reference vehicle speed V1 according to the temperature of the hydraulic oil. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automatic engine stop device for a vehicle that automatically stops the engine in accordance with vehicle driving conditions such as vehicle speed and brake pedal operation.

In recent years, for the purpose of reducing fuel consumption and improving exhaust emission, an automatic engine stop device has been developed that automatically stops the engine when the vehicle is in a predetermined operating condition. For example, the engine automatic stop device automatically stops the engine on the condition that the brake pedal is depressed and the vehicle speed is equal to or lower than the reference vehicle speed.
JP 2000-175304 A

  By the way, in a vehicle in which engine power is transmitted to wheels via an automatic transmission, when the engine speed decreases as the vehicle speed decreases, the oil pressure generated by an oil pump driven by the engine decreases. For this reason, if conditions such as a decrease in the viscosity of hydraulic fluid due to temperature rise overlap, the hydraulic pressure for operating the clutch and brake (power transmission mechanism) in the automatic transmission will drop below the reference value, thereby causing the clutch and brake to The fastening state becomes unstable and easy to do.

  Therefore, when the engine automatic stop device is applied to a vehicle equipped with such an automatic transmission, when the vehicle speed becomes lower than the reference vehicle speed and the engine automatically stops, the temperature in the automatic transmission is increased. When the clay of the hydraulic oil decreases, the engagement state of the clutch and brake in the automatic transmission becomes unstable, and there is a concern that a shock may occur at this time.

  However, if this engine is disliked and the automatic engine stop is stopped, the engine will continue to burn even if the vehicle speed decreases, so that it is not possible to sufficiently improve fuel efficiency and emissions.

  Therefore, the present invention provides a vehicle engine capable of sufficiently reducing fuel consumption and improving emission by enabling automatic engine stop without any trouble even in a situation where the temperature of hydraulic oil in the automatic transmission is high. It is intended to provide an automatic stop device.

In order to achieve the above-described object, the invention according to claim 1 is directed to a method in which the power of an engine (for example, the engine 1 in the embodiment) is transmitted to wheels (for example, the automatic transmission 5 in the embodiment) via an automatic transmission (for example, the automatic transmission 5 in the embodiment). An automatic engine stop of a vehicle which is mounted on a vehicle transmitted to the wheel 7) in the embodiment and automatically stops the engine on the condition that the vehicle speed is equal to or lower than the reference vehicle speed (for example, the reference vehicle speed V1 in the embodiment). The power transmission mechanism in the automatic transmission is operated by the oil pressure of an engine-driven oil pump (for example, the oil pump 22 in the embodiment), and the hydraulic oil for operating the automatic transmission is a device. The temperature was monitored, and the reference vehicle speed was changed according to the temperature of the hydraulic oil.
In this case, when the temperature of the hydraulic oil rises and the viscosity of the hydraulic oil tends to decrease, the reference vehicle speed is changed according to the temperature rise of the hydraulic oil. Thereby, contrary to the decrease in the viscosity of the hydraulic oil, the number of revolutions of the oil pump at the time of the automatic engine stop increases, and the pressure of the hydraulic oil when the automatic engine stop is started is maintained high. Therefore, a power transmission mechanism such as a clutch in the automatic transmission is less likely to become unstable when the engine is stopped.

According to a second aspect of the present invention, in the first aspect of the present invention, the change in the reference vehicle speed according to the temperature of the hydraulic oil is caused by a lock-up clutch (for example, interposed between the engine and the automatic transmission). The fact that the lock-up clutch 8) in the embodiment is in the engaged state is executed as one permission condition.
In this case, when the lockup clutch is not fastened and the shock converter is in a state where it is easy to absorb the shock, it is possible to eliminate the unnecessary change in the reference vehicle speed.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the relationship between the temperature of the hydraulic oil and a reference vehicle speed corresponding to the temperature is set according to a gear ratio or a gear position of the automatic transmission. I tried to do it.

According to the first aspect of the present invention, since the reference vehicle speed at which the engine automatic stop is started increases as the temperature of the hydraulic oil rises, the operation hydraulic pressure of the power transmission mechanism at the time of the engine automatic stop is maintained high. Shocks in the transmission are less likely to occur.
Furthermore, in this invention, since the engine automatic stop is not stopped when the temperature of the hydraulic oil rises, it is possible to reliably improve the fuel efficiency and the emission.

  According to the second aspect of the present invention, when the lock-up clutch is not engaged and the torque is easily absorbed by the torque converter or the like, an unnecessary reference vehicle speed is not changed. Can be automatically stopped.

  According to the third aspect of the present invention, the optimum reference vehicle speed can be changed in accordance with the gear ratio and the gear position of the automatic transmission. Therefore, the engine automatic stop can be executed at a lower speed at each shift stage, which is advantageous in improving fuel efficiency and emission.

Next, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is an overall configuration diagram showing a power transmission system of a vehicle according to this embodiment.
In this embodiment, an engine automatic stop device according to the present invention is applied to a hybrid vehicle having both an engine 1 and a motor 2 as drive sources. This hybrid vehicle employs a so-called parallel type vehicle in which a motor 2 that also serves as a generator is directly connected to an engine 1 to perform energy regeneration during driving assistance and braking of the engine 1.

  A drive shaft 3 from which the power of the engine 1 and the motor 2 is taken out is connected to a multistage automatic transmission 5 via a torque converter 4, and an output shaft 6 of the automatic transmission 5 is connected to left and right via a differential mechanism (not shown). Connected to the drive wheel 7. In FIG. 1, only one wheel 7 is schematically shown. The torque converter 4 includes a lockup clutch 8 for switching between torque transmission using hydraulic oil as a medium and mechanically connected torque transmission by friction engagement. The lockup clutch 8 is engaged and released by the control oil pressure supplied from the oil pressure control circuit 9 in the same manner as the speed change operation of the automatic transmission 5.

  The engine 1 is a reciprocating type multi-cylinder engine, and fuel injection and ignition in each cylinder are performed by a combustion operation unit 10 in which a spark plug and a fuel injection valve are integrated. The combustion operation unit 10 is controlled by an electronically controlled controller 11 (ECU) according to the driving situation of the vehicle. The combustion operation unit 10 optimally adjusts the combustion of the engine 1 under normal driving conditions under the control of the controller 11, but automatically stops the engine 1 when the vehicle state and the driving operation satisfy predetermined automatic stop conditions. Thereafter, the engine 1 is automatically restarted when the automatic restart condition is satisfied. In this embodiment, the combustion operation unit 10 and the controller 11 mainly constitute the engine automatic stop device according to the present invention.

  Further, a throttle (not shown) for adjusting the intake air amount of the engine 1 is constituted by an electronically controlled throttle, and the valve opening according to the depression amount of the accelerator pedal is controlled by the controller 11.

The following is connected to the input section of the controller 11 as main detection means.
(A) Brake switch 12 for detecting whether or not the brake pedal has been depressed.
(B) Accelerator pedal sensor 13 for detecting the depression amount of the accelerator pedal
(C) Crank angle sensor 14 for detecting the engine speed
(D) Input shaft rotation sensor 16 for detecting the rotational speed of the input shaft 15 of the automatic transmission 5
(E) Vehicle speed sensor 17 for detecting the vehicle speed
(F) Shift position sensor 18 for detecting the shift position of the automatic transmission 5
(G) A remaining capacity sensor (not shown) for detecting the remaining capacity of the battery 19
(H) Oil temperature sensor 20 for detecting the oil temperature of the hydraulic oil in the automatic transmission 5

  The motor 2 is connected to the battery 19 via a PDU (power drive unit) 21, and rotates the drive shaft 3 by the electric power of the battery 19 under the control of the PDU 21 by the controller 11. Further, the motor 2 functions as a generator during braking of the vehicle, and the battery 19 is charged with regenerative energy by the control of the PDU 21 by the controller 11.

  This hybrid vehicle includes a mechanical oil pump 22 and an electric oil pump 23 as a hydraulic pressure supply source for the hydraulic control circuit 9. The mechanical oil pump 22 is linked to the rotating shaft of the engine 1 and is operated by the driving force of the engine 1 or the motor 2. The electric oil pump 23 is driven by an electric motor 26 connected to a 12V auxiliary battery 25 via a pump driver 24. The electric oil pump 23 is basically stopped when the mechanical oil pump 22 is normally operated by the power of the engine 1 or the motor 2, and the mechanical oil pump 22 is reduced by a decrease in the rotational speed of the drive shaft 3. When a sufficient discharge amount cannot be obtained, it is driven by control by the controller 11.

  In addition, the hydraulic control circuit 9 is linked to a shift lever (not shown), a manual valve (not shown) for selecting and switching the basic oil path of forward, neutral and reverse, and the hydraulic oil pressure and details. A plurality of other valves (not shown) for controlling the switching of the oil passages are provided, and these valves are controlled by the controller 11 in accordance with the driving state of the vehicle, whereby clutches and brakes in the automatic transmission 5 are provided. Adjust the operating pressure. As a result, the automatic transmission 5 changes the gear position and cuts off the power. Further, the hydraulic control circuit 9 appropriately supplies the control hydraulic pressure to the lock-up clutch 8 of the torque converter 4 by the valve control by the controller 11 according to the driving state of the vehicle as described above.

Basic engine automatic stop control (hereinafter referred to as “basic automatic stop control”) in the hybrid vehicle is executed by the controller 11 when all of the following conditions (1) to (3) are satisfied.
(1) Brake switch 12 is ON
(2) Depression amount detected by the accelerator pedal sensor 13 is 0
(3) The vehicle speed once exceeds the control permission vehicle speed, and the current vehicle speed is below the reference vehicle speed V1 (see Fig. 2).
However, in this embodiment, the control-permitted vehicle speed and the reference vehicle speed V1 are set to the same value. However, the control-permitted vehicle speed and the reference vehicle speed V1 are not necessarily set to the same value, and the control-permitted vehicle speed may be set larger than the reference vehicle speed V1.

The engine restart control after the engine automatic stop control is performed is executed by the controller 11 when the following conditions (4) and (5) are simultaneously satisfied.
(4) Brake switch 12 is OFF
(5) The amount of depression by the accelerator pedal sensor 13 is greater than or equal to a predetermined value. Note that the conditions for the basic automatic stop control and the engine restart control described here are examples, and other conditions can be added.

  By the way, the engine automatic stop device of this embodiment changes the reference vehicle speed V1 permitting automatic engine stop according to the temperature of the hydraulic oil in the automatic transmission 5 based on the basic automatic stop control described above. ing. That is, a table in which the relationship between the vehicle speed and the oil temperature as shown in FIG. 3 is set for each gear position of the automatic transmission 5 is stored in the storage unit in the controller 11, and when the automatic engine stop is started. The temperature of the hydraulic oil is read by the oil temperature sensor 20, and at this time, the vehicle speed corresponding to the detected temperature is obtained by referring to the table. And the vehicle speed calculated | required here is substituted for the reference | standard vehicle speed V1, and the reference | standard vehicle speed V1 is changed into the value according to the temperature of hydraulic fluid. The relationship between the vehicle speed and the oil temperature in the normal temperature range in the table is basically set so that the vehicle speed increases approximately proportionally as the oil temperature increases.

  FIG. 4 is a flowchart showing the engine automatic stop control of this embodiment. Hereinafter, specific control will be described with reference to this flowchart.

In S101, it is determined based on signals from the brake switch 12 and the accelerator pedal sensor 13 that the brake pedal is depressed and the accelerator pedal is released (conditions (1) and (2)), and both conditions are satisfied. Sometimes the process proceeds to S102, and when not satisfied, the process is skipped and the engine 1 is not automatically stopped.
In S102, a reference vehicle speed V1 corresponding to the current gear position of the automatic transmission 5 and the temperature of the hydraulic oil is determined with reference to the vehicle speed-oil temperature table in the storage unit, and in S103, the current vehicle speed is determined in S102. It is determined whether the vehicle speed is equal to or less than the determined reference vehicle speed V1. When it is determined at 103 that the vehicle speed is not lower than the reference vehicle speed V1, the engine 1 is not automatically stopped. When it is determined that the vehicle speed is lower than the reference vehicle speed V1, the engine 1 is automatically stopped and the control is terminated.

  As described above, the engine automatic stop device according to this embodiment is changed to increase the reference vehicle speed V1 in accordance with the increase of the temperature of the hydraulic oil in the automatic transmission 5, and thus operates with the temperature increase. Even if the viscosity of the oil is lowered, the engagement pressure of the power transmission mechanism (clutch or brake) in the automatic transmission at the time of automatic engine stop can be maintained high. That is, in this automatic engine stop device, the decrease in the fastening pressure caused by the decrease in the viscosity of the hydraulic oil accompanying the temperature increase increases the engine automatic stop start speed (reference vehicle speed V1), and the mechanical oil pump when the engine is stopped. It can be offset by increasing the discharge pressure of 22. Therefore, in the vehicle using this automatic engine stop device, it is possible to eliminate the problem that the engagement of the clutch or brake in the automatic transmission 5 becomes unstable when the engine is automatically stopped. Can be prevented in advance.

  In addition, this engine automatic stop device does not stop the engine automatic stop itself only by increasing the engine automatic stop start speed (reference vehicle speed V1) even if the temperature of the hydraulic oil in the automatic transmission rises. This is advantageous for improving fuel efficiency and reducing exhaust emissions.

Next, another embodiment of the present invention will be described with reference to FIG.
The schematic configuration of the vehicle of this embodiment is the same as that of the above-described embodiment, and is the same as FIG. Therefore, here, the configuration of the vehicle will be described with reference to FIG.

FIG. 4 is a flowchart showing the control of the engine automatic stop device of this embodiment. This device is different in that another condition is added before the process of determining the reference vehicle speed according to the temperature of the hydraulic oil in the automatic transmission.
That is, the control by this device is performed in S102, in which the lock-up clutch 8 in the torque converter 4 is engaged before the reference vehicle speed V1 corresponding to the hydraulic oil temperature is determined with reference to the vehicle speed-oil temperature table. It is determined whether or not the engine is in the engaged state, and the process of S102 is performed only when it is determined that the engine is in the engaged state. When it is determined that the engine is not in the engaged state, automatic engine stop is not permitted. Whether the lock-up clutch 8 is engaged or not is determined based on detection signals from the crank angle sensor 14 on the engine 1 side and the input shaft rotation sensor 16 on the automatic transmission 5 side, for example. good.

  Therefore, according to the control by the engine automatic stop device of this embodiment, when the lockup clutch 8 is not engaged and the engine 1 and the automatic transmission 5 are connected via the hydraulic oil in the torque converter 4, the operation is performed. The reference vehicle speed V1 is not changed according to the oil temperature. That is, when the engine 1 and the automatic transmission 5 are connected via the hydraulic oil in the torque converter 4, even if a slight shock occurs in the automatic transmission when the engine is stopped, the hydraulic oil in the torque converter 4 Can absorb shocks. Therefore, in the apparatus of this embodiment, it is possible to eliminate the increase in the reference vehicle speed V1 as much as possible, and to further improve the fuel efficiency and suppress the emission.

  In addition, this invention is not limited to the said embodiment, A various design change is possible in the range which does not deviate from the summary. For example, in the above-described embodiment, the engine automatic stop device according to the present invention is applied to a hybrid vehicle including an engine and a motor. However, the engine automatic stop device may be applied to a vehicle including only an engine as a power source. In the above embodiment, a multi-stage automatic transmission is employed as a transmission for transmitting engine power to wheels. However, a continuously variable automatic transmission can also be employed. In this case, the relationship between the temperature of the hydraulic oil and the reference vehicle speed corresponding to the temperature may be obtained by, for example, calculation according to the gear ratio of the automatic transmission.

The schematic block diagram of the hybrid vehicle carrying the engine automatic stop apparatus of one Embodiment of this invention. The time chart which shows the relationship between the vehicle speed at the time of the engine stop of the embodiment, an engine speed, and a brake signal. The vehicle speed-oil temperature table for every gear stage of the automatic transmission according to the embodiment. The flowchart which shows the control at the time of the engine automatic stop of the embodiment. The flowchart which shows the control at the time of the engine automatic stop of other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 5 ... Automatic transmission 7 ... Wheel 8 ... Lock-up clutch 22 ... Oil pump V1 ... Standard vehicle speed

Claims (3)

It is mounted on a vehicle in which engine power is transmitted to wheels via an automatic transmission,
An automatic engine stop device for a vehicle that automatically stops the engine on the condition that the vehicle speed is lower than the reference vehicle speed,
The power transmission mechanism in the automatic transmission is operated by the hydraulic pressure of an oil pump driven by the engine.
An automatic engine stop device for a vehicle, which monitors the temperature of hydraulic oil for operating the automatic transmission and changes the reference vehicle speed according to the temperature of the hydraulic oil.   The change of the reference vehicle speed according to the temperature of the hydraulic oil is executed as one permission condition that a lock-up clutch interposed between the engine and the automatic transmission is in an engaged state. 2. An automatic engine stop device for a vehicle according to 1. 3. The automatic engine stop device for a vehicle according to claim 1, wherein the relationship between the temperature of the hydraulic oil and a reference vehicle speed corresponding to the temperature is set according to a gear ratio or a gear position of the automatic transmission. .

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