JP5178602B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control device, and more particularly to a shift control device in an idle stop vehicle equipped with a belt type continuously variable transmission.

  2. Description of the Related Art Conventionally, there has been known a vehicle that performs an idle stop control that automatically stops an engine when a predetermined condition is satisfied, and suppresses useless fuel consumption and emission of gas while the vehicle is stopped. Engine stop conditions in such idle stop control include vehicle stop and brake ON, and engine restart conditions include brake OFF and accelerator pedal depression.

  2. Description of the Related Art A vehicle equipped with an engine that performs idle stop control as described above and a belt-type continuously variable transmission is known. Generally, a continuously variable transmission is provided with a primary pulley and a secondary pulley over which a belt is laid, and by controlling the oil pressure of these pulleys, a shift control and a belt clamping pressure control are performed. When the continuously variable transmission is at the maximum gear ratio (lowest), the movable sheave of the primary pulley stops against the stopper, so the thrust on the primary pulley (belt clamping pressure) Thus, the thrust force from the secondary pulley acts as an assisting force on the primary pulley side via the belt tension due to the stopper reaction force. For this reason, even if the primary hydraulic pressure is drained, the belt transmission torque can be estimated by the amount of assist.

  However, in the case of an idle stop vehicle, an idle stop state may occur while the primary pulley does not return to the maximum gear ratio position due to a sudden stop of the vehicle or the like. In that case, when the engine is restarted next time, since there is no reaction force of the stopper, the belt transmission torque for the assist cannot be expected, and the belt cannot slip and the vehicle cannot start.

  In the case of an idle stop vehicle having only an oil pump driven by an engine as a hydraulic pressure source of the pulley, the oil pump is also stopped in the idle stop state, so that no hydraulic pressure is supplied to the pulley. Therefore, if the continuously variable transmission does not return to the maximum gear ratio due to a sudden stop of the vehicle or the like, the pulley cannot be returned to the maximum gear ratio during idle stop.

  In addition to an oil pump driven by an engine, an idle stop vehicle having an electric pump driven at an idle stop has been proposed. In this case, since the hydraulic pressure can be supplied to the pulley even during idle stop, the pulley can be returned to the maximum gear ratio, and the vehicle can start simultaneously with the restart of the engine. However, there is a problem that the cost is increased due to the electric pump.

  Patent Document 1 discloses a speed change control device for a continuously variable transmission that can obtain the maximum speed ratio prior to re-starting even when the maximum speed ratio cannot be fully restored due to a sudden stop of the vehicle or the like. . That is, when it is determined that the transmission ratio of the continuously variable transmission is not the maximum transmission ratio and it is determined that the rotation element of the continuously variable transmission is stopped, the shift lever has been switched to the P or N position. As a condition, the gear ratio of the continuously variable transmission is forcibly changed to the maximum gear ratio side.

  However, this control device forcibly shifts to the maximum gear ratio side while the vehicle is stopped, and the engine continues to rotate and the hydraulic pressure is generated while the continuously variable transmission is stopped. It is assumed. When the engine is stopped and no hydraulic pressure is generated as in the idling stop, the speed cannot be changed to the maximum gear ratio.

JP 2002-181180 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle control device that can reliably return a continuously variable transmission to a maximum gear ratio even when there is a sudden vehicle stop or the like before transition to an idle stop state, and can start when the engine is restarted. Is to provide.

  In order to achieve the above object, the present invention is a vehicle equipped with an engine and a belt-type continuously variable transmission, and is provided in an oil pump driven by the engine, the continuously variable transmission, and during forward traveling. The forward clutch to be engaged, the clutch hydraulic pressure control means for controlling the hydraulic pressure of the forward clutch based on the hydraulic pressure using the oil pump as a hydraulic source, the hydraulic pressure of the primary pulley and the secondary pulley of the continuously variable transmission, Pulley hydraulic control means for controlling based on hydraulic pressure using an oil pump as a hydraulic source, a stopper with which the movable sheave of the primary pulley comes into contact when the continuously variable transmission reaches a maximum gear ratio, and the continuously variable transmission Maximum speed ratio detecting means for detecting that the speed ratio is the maximum speed ratio, and an idling for stopping the engine when a predetermined condition is satisfied An idle stop determination means for performing a stop determination; and when the idle stop determination is performed and the speed ratio of the continuously variable transmission is not the maximum speed ratio, the forward travel is performed between the idle stop determination and the engine stop. There is provided a control device for a vehicle, characterized by comprising a control means for draining the hydraulic pressure of the primary pulley while bringing the clutch into a released state.

  The present invention is intended for an idle stop vehicle having only an oil pump driven by an engine as a hydraulic source for forward clutches and pulleys, and does not have a special hydraulic source such as an electric pump. Hydraulic pressure cannot be supplied to the forward clutch or pulley. Therefore, if the engine is stopped before the gear ratio returns to the maximum gear ratio (lowest) due to a sudden stop of the vehicle or the like, the next time the engine is restarted, the belt slips and cannot start quickly. Therefore, in the present invention, when the idle stop determination is made and the speed ratio of the continuously variable transmission is not the maximum speed ratio, the forward clutch is released from the idle stop determination to the engine stop, and the primary pulley is The hydraulic pressure is drained to ensure that the maximum speed ratio is restored before the engine stops. If the primary pulley hydraulic pressure is drained without releasing the forward clutch, belt slip occurs, so the forward clutch is first released to the neutral state, and then the primary pulley hydraulic pressure is drained. Therefore, even when the belt is stopped (as long as the engine is rotating), the movable sheave can be moved and can be reliably returned to the maximum gear ratio. Next, when the idle stop is released and the engine restarts and starts, the movable sheave of the primary pulley comes into contact with the stopper. It acts as an assist force on the pulley, and the belt transmission torque can be estimated by the assist amount. Therefore, even if the hydraulic pressure supply to the primary pulley is delayed, the belt transmission torque can be obtained by the thrust of the secondary pulley, and the vehicle can be started quickly.

  The maximum gear ratio detection means detects whether or not the gear ratio of the continuously variable transmission is the maximum gear ratio. As a specific detection method, for example, the rotation speed ratio between the primary pulley and the secondary pulley is used as a reference value. And a method for determining whether or not the movable sheave of the primary pulley is in contact with the stopper. In the former case, it is possible to easily determine whether the speed ratio is the maximum without requiring a special sensor. On the other hand, in the latter case, a sensor is provided on one of the stopper and the movable sheave, and it can be detected from the output signal of this sensor whether or not the movable sheave has come into contact with the stopper. The contact can be detected directly.

  In general, in the case of an idle stop vehicle, there is a time lag of about 1 to 2 seconds from the idle stop determination until the engine actually stops. In the present invention, the forward clutch is released using this time lag, and the primary pulley hydraulic pressure is drained to return to the maximum gear ratio. In addition, by providing a waiting time of a certain degree (for example, about 1 second) between the idle stop determination and the engine rotation starts to decrease, even if there is a variation in the release time of the forward clutch and the drain time of the primary pulley hydraulic pressure. The maximum gear ratio may be reliably restored before the engine stops.

  As described above, according to the control device of the present invention, when the idle stop determination is made when the movable sheave of the primary pulley is not in contact with the stopper (not the maximum gear ratio), the engine is stopped from the idle stop determination. In the meantime, since the forward clutch is disengaged and the hydraulic pressure of the primary pulley is drained, it is possible to quickly return to the maximum gear ratio. Therefore, when the engine restarts and starts, the primary pulley can secure a predetermined belt transmission torque and can start the vehicle quickly.

It is a figure showing the whole system of vehicles concerning the present invention. It is a skeleton figure which shows the structure of a continuously variable transmission. It is the schematic of the hydraulic control circuit for controlling a primary pulley, a secondary pulley, and a forward clutch. It is a time chart figure of an example of control at the time of idle stop. It is a flowchart figure of an example of the control method which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to examples.

  FIG. 1 shows an example of a vehicle system equipped with a continuously variable transmission which is an example of an automatic transmission according to the present invention. The output shaft 1 a of the engine 1 is connected to the drive shaft 32 via the continuously variable transmission 2. The continuously variable transmission 2 is provided with a torque converter 3, a transmission mechanism 4, a hydraulic control device 5, an oil pump 6 driven by the engine 1, and the like.

  The engine 1 and the continuously variable transmission 2 are controlled by the electronic control unit 100. Signals are input from the various sensors 101 to 107 to the electronic control device 100. Input signals include engine speed, vehicle speed (or secondary pulley speed), throttle opening (or accelerator opening), shift position, primary pulley speed (or turbine speed), brake signal, oil temperature, etc. . In addition, an idle signal, a start signal, an engine water temperature, an intake air amount, an air conditioner signal, an ignition signal, and the like may be input. The gear ratio of the continuously variable transmission 2 can be detected from the primary pulley rotation speed and the vehicle speed. For the sake of simplicity, FIG. 1 shows an example in which both the engine 1 and the continuously variable transmission 2 are controlled by a single electronic control unit 100. However, the engine 1 and the continuously variable transmission 2 are actually used. Are controlled by individual electronic control units, and both electronic control units are linked to each other via a communication bus.

  The electronic control unit 100 has an idle stop function of stopping the engine 1 (idle stop) when a predetermined condition is satisfied and restarting the engine when the predetermined condition is not satisfied. Conditions for permitting idle stop include, for example, when the vehicle speed is less than a certain value, the throttle opening is fully closed, and the vehicle deceleration is less than a predetermined value, or when the vehicle is stopped and the brake is on (depressing the brake pedal). It is. However, idling stop is not permitted when the engine water temperature is low, the electric load is large, or the accelerator pedal is depressed. On the other hand, idle stop release (engine restart) conditions include, for example, brake OFF, accelerator pedal depression, and input of a vehicle speed signal.

  The electronic control device 100 also performs control of the continuously variable transmission 2 in addition to engine control. That is, the continuously variable transmission is determined by determining the target primary rotational speed according to a preset shift map according to the vehicle speed and the throttle opening, and controlling the solenoid valves 5a to 5c built in the hydraulic control device 5. 2 is controlled to the target value. The hydraulic control device 5 also has a function of controlling the hydraulic pressure supplied to the direct coupling clutch 86 and the reverse brake 85 built in the continuously variable transmission 2 described later. This control includes release control of the reverse brake (forward clutch) at the time of idling stop, which will be described later. In this embodiment, an example in which the hydraulic control device 5 has three solenoid valves 5a to 5c has been shown, but in addition to this, for controlling the lock-up clutch 3a built in the torque converter 3, for line pressure control, etc. Another solenoid valve may be provided. Note that the hydraulic pressure source of the hydraulic control device 5 is only the oil pump 6 driven by the engine 1 described above, and no special oil pump such as an electric pump is provided.

  FIG. 2 shows an example of the internal structure of the continuously variable transmission 2. The continuously variable transmission 2 includes a torque converter 3 and a continuously variable transmission mechanism 4. The turbine shaft 7 of the torque converter 3 is connected to the primary shaft 10 via a forward / reverse switching device 8. The forward / reverse switching device 8 transmits the rotation of the turbine shaft 7 to the primary shaft 10 by switching between forward and reverse. The continuously variable transmission mechanism 4 further includes a primary pulley 11, a secondary pulley 21, a V belt 15 wound between both pulleys, a secondary shaft 20, a differential device 30 that transmits power of the secondary shaft 20 to a drive shaft 32, and the like. ing. The turbine shaft 7 and the primary shaft 10 are arranged on the same axis, and the secondary shaft 20 and the drive shaft 32 are arranged parallel to the turbine shaft 7 and non-coaxially. Therefore, the continuously variable transmission 2 has a three-axis configuration as a whole. The V belt 15 used here is a known metal belt composed of a pair of endless tension bands and a number of blocks supported by these tension bands, for example.

  The forward / reverse switching device 8 includes a planetary gear mechanism 80, a reverse brake 85, and a direct coupling clutch 86, and the reverse brake 85 corresponds to the forward clutch in the present invention. The reverse brake 85 and the direct coupling clutch 86 are wet multi-plate brakes and clutches, respectively. A sun gear 81 of the planetary gear mechanism 80 is connected to the turbine shaft 7 as an input member, and a ring gear 82 is connected to the primary shaft 10 as an output member. The planetary gear mechanism 80 is a single pinion system, the reverse brake 85 is provided between the carrier 84 supporting the pinion gear 83 and the transmission case, and the direct coupling clutch 86 is provided between the carrier 84 and the sun gear 81. When the direct coupling clutch 86 is released and the reverse brake 85 is engaged, the rotation of the turbine shaft 7 is reversed, decelerated, and transmitted to the primary shaft 10. Then, the drive shaft 32 rotates in the same direction as the engine rotation direction via the secondary shaft 20, so that the vehicle travels forward. Conversely, when the reverse brake 85 is released and the direct coupling clutch 86 is engaged, the carrier 84 and the sun gear 81 rotate together, so that the turbine shaft 7 and the primary shaft 10 are directly coupled. Then, since the drive shaft 32 rotates in the direction opposite to the engine rotation direction via the secondary shaft 20, a reverse traveling state is set.

The primary pulley 11 includes a fixed sheave 11a that is integrally fixed on the primary shaft 10, and a movable sheave 11b that is supported on the primary shaft 10 so as to be axially movable and integrally rotatable. A cylinder 12 fixed to the primary shaft 10 is provided behind the movable sheave 11 b, and a hydraulic chamber 13 is formed between the movable sheave 11 b and the cylinder 12. Shift control is performed by controlling the flow rate of hydraulic oil to the hydraulic chamber 13. When draining the hydraulic oil in the hydraulic chamber 13, the movable sheave 11b is retracted, the ends 11b ₁ of the movable sheave 11b is that abuts against the inner wall of the cylinder 12 (the stopper 12a), maximum gear ratio (highest Low) is configured The Therefore, since the movable sheave 11b is in contact with the stopper 12a at the maximum gear ratio, the thrust of the primary pulley 11 includes the thrust of the secondary pulley 21 as the belt tension as the assist force on the primary side in addition to the thrust due to the primary hydraulic pressure. Works. For this reason, even if the primary hydraulic pressure decreases, the belt transmission torque for the assist can be expected.

  The secondary pulley 21 includes a fixed sheave 21a that is integrally fixed on the secondary shaft 20, and a movable sheave 21b that is supported on the secondary shaft 20 so as to be axially movable and integrally rotatable. A piston 22 fixed to the secondary shaft 20 is provided behind the movable sheave 21 b, and a hydraulic chamber 23 is formed between the movable sheave 21 b and the piston 22. By controlling the hydraulic pressure in the hydraulic chamber 23, a clamping pressure necessary for torque transmission is applied. A bias spring 24 that generates an initial clamping pressure is disposed in the hydraulic chamber 23.

  One end portion of the secondary shaft 20 extends toward the engine side, and the output gear 27 is fixed to this end portion. The output gear 27 meshes with the ring gear 31 of the differential device 30, and power is transmitted from the differential device 30 to the drive shaft 32 extending left and right to drive the wheels.

  FIG. 3 schematically shows a hydraulic control circuit for controlling the primary pulley 11, the secondary pulley 21, and the forward clutch 85 of the continuously variable transmission 2 in the hydraulic control device 5. In FIG. 3, the hydraulic pressure discharged by the oil pump 6 is adjusted to a predetermined line pressure by the regulator valve 51, and then hydraulic oil is supplied to the primary pulley 11 via the transmission control valve 52, and the clamping pressure control valve Hydraulic oil is supplied to the secondary pulley 21 via 53. The transmission control valve 52 is a flow control valve, and the clamping pressure control valve 53 is a pressure control valve. Further, the line pressure is supplied to the forward clutch 85 via the clutch pressure control valve 54, and the clutch pressure is controlled. The shift control valve 52, the clamping pressure control valve 53, and the clutch pressure control valve 54 are equipped with solenoids 52a, 53a, 54a, respectively. The clutch pressure of the forward clutch 85 is controlled. In FIG. 3, valves that are not directly related to the control of the present invention, such as manual valves and garage shift valves, are omitted. Since the speed change control valve 52 that is a flow rate control valve needs to be closed in order to maintain at a predetermined speed ratio, the supply and discharge of the hydraulic oil to and from the primary pulley 11 takes longer time than the secondary pulley 21. For this reason, when the vehicle suddenly decelerates, the maximum gear ratio may not be completely restored until the vehicle stops, that is, the movable sheave 11b may not contact the stopper 12a. In particular, if the maximum gear ratio cannot be restored during the transition to the idle stop state, belt slip occurs when the next idle stop is restored. In the present invention, in order to solve such a problem, control as described later is performed.

  Next, a control method according to the present invention when idle stop is permitted by idle stop determination will be described with reference to FIG. FIG. 4 shows engine stop determination, idle stop execution determination, engine speed, forward clutch signal, forward clutch pressure, primary pulley drain request flag, primary pulley pressure, and change in gear ratio over time. Represents the present invention.

  When a predetermined idle stop condition is satisfied at time t1, an idle stop permission flag is set, and a gear ratio is obtained at time t2 after a minute time. If the gear ratio is the maximum gear ratio at this time, engine stop control is performed, and the following control is not performed. On the other hand, when the gear ratio is not the maximum gear ratio at time t2, the forward clutch signal is switched from the D position to the N position in parallel with the start of the engine stop control. That is, by outputting a forward clutch disengagement signal to the clutch pressure control valve 54, the clutch pressure rapidly decreases and becomes a neutral state. At time t3 when the clutch pressure becomes substantially zero, the drain request flag of the primary pulley is turned ON, and the shift control valve 52 drains the primary pressure. Therefore, the gear ratio of the continuously variable transmission 2 rapidly changes to the maximum gear ratio (Low), and the movable sheave 11b of the primary pulley 11 contacts the stopper 12a (time t4). Each time interval from time t1 to t2 to t3 is determined in advance, and the time from time t1 to t4 is set within the time from engine stop control until the engine is stopped for engine stop control. The time from time t1 to t4 is set to about 1 second or less although it depends on the CVT oil temperature. If it is determined after time t4 that engine rotation has stopped at time t5, the forward clutch signal is returned to the D position, and the drain request flag for the primary pulley is turned OFF. Therefore, even when the idle stop is subsequently released and the engine restarts and starts, the movable sheave 11b of the primary pulley 11 is in contact with the stopper 12a. Due to the reaction force, the thrust by the secondary pulley 21 acts on the primary pulley 11 as an assisting force, and the belt transmission torque can be secured. Therefore, the vehicle can be started quickly without causing belt slip.

  In FIG. 4, the engine stop is started almost simultaneously with the idling stop flag being set. However, the engine stopping is started for a predetermined time after the idling stop flag is set, as indicated by a one-dot chain line in FIG. It may be after T. This is because the release of the forward clutch and the drain of the primary pressure can be reliably terminated before the engine stops. Further, although the primary pressure drain is started after the forward clutch is released, both may be started simultaneously.

FIG. 5 shows the flow of the control method according to the present invention. When starting, it is first determined whether or not an idle stop condition is satisfied (step S1). As an idle stop condition, for example, the vehicle speed is less than a predetermined value (for example, 5 km / h), the throttle opening is fully closed, and the vehicle deceleration is less than a predetermined value (for example, 1 m / s ² ), or the vehicle is completely stopped. For example, when the brake is ON. When the idle stop condition is satisfied, that is, when the idle stop is permitted, the gear ratio of the continuously variable transmission is subsequently compared with a predetermined value α (step S2). The predetermined value α is a value near the maximum gear ratio. If the gear ratio is larger than α, it means that the continuously variable transmission has already reached the maximum gear ratio, in other words, the movable sheave 11b of the primary pulley 11 is in contact with the stopper 12a. Then, the engine stop control is started without performing any special control (step S3), and is finished. On the other hand, if the speed ratio is less than or equal to α, the maximum speed ratio has not yet been reached, so the forward clutch 85 is first released to the neutral state (step S4), and then the primary hydraulic pressure drain is started. (Step S5). Then, it is determined whether or not a predetermined time has elapsed from the idle stop permission (step S6). If the predetermined time has elapsed, the engine stop control is started (step S3). The predetermined time is a time required for releasing the forward clutch 85 and draining the primary hydraulic pressure, and is about 1 second, for example. By the above control, the release of the forward clutch 85 and the drain of the primary hydraulic pressure can be terminated before the engine is stopped, and it can be reliably returned to the maximum gear ratio before the engine is stopped.

  After the engine stops, the forward clutch signal is returned to the D state and the primary hydraulic signal is returned to the non-drain state in preparation for the next start. However, even if the forward clutch signal is returned to the D state and the primary hydraulic pressure signal is returned to the non-drain state, the engine is stopped and the oil pump is also stopped, so that the hydraulic pressure is not actually supplied to the forward clutch and the primary pulley.

  In the control of FIG. 4, the engine stop control is started after the idling stop is permitted, and at the same time, the forward clutch is released and the primary hydraulic pressure is drained. The engine may stop before the ratio returns to the maximum gear ratio. In this case, as shown in FIG. 5, it is preferable to wait for a predetermined time (step S6) so that the release of the forward clutch and the drain of the primary hydraulic pressure are surely completed before the engine stops. This predetermined time may be about 1 second, for example, and does not degrade the idle stop performance.

  In the above embodiment, since the single pinion type planetary gear mechanism is used as the forward / reverse switching device, the reverse brake corresponds to the forward clutch, but when the double pinion type planetary gear mechanism is used, it is directly connected. The clutch corresponds to the forward clutch. FIG. 3 shows an example in which the shift control valve 52, the clamping pressure control valve 53, and the clutch pressure control valve 54 themselves are solenoid valves. However, this is only an example. For example, a combination of a control valve and a solenoid valve is used. Other configurations may be used. The solenoid valve may be either a linear solenoid valve or a duty solenoid valve.

DESCRIPTION OF SYMBOLS 1 Engine output shaft 2 Continuously variable transmission 3 Torque converter 4 Transmission mechanism 5 Planetary gear apparatus 6 Oil pump 8 Forward / reverse switching apparatus 11 Primary pulley 11b Movable sheave 11b ₁ end part 12a Stopper 15 Belt 21 Secondary pulley 52 Shift control valve (pulley Hydraulic control means)
53 Nipping pressure control valve (pulley hydraulic pressure control means)
54 Clutch pressure control valve (clutch hydraulic pressure control means)
80 Planetary gear mechanism 85 Reverse brake (forward clutch)
86 Direct coupling clutch 100 Electronic control device 101 Engine speed sensor 102 Vehicle speed sensor 103 Throttle opening sensor 104 Shift position sensor 105 Primary pulley speed sensor 106 Brake sensor 107 Oil temperature sensor

Claims (1)

A vehicle equipped with an engine and a belt-type continuously variable transmission,
An oil pump driven by the engine;
A forward clutch provided in the continuously variable transmission and fastened during forward travel;
Clutch hydraulic control means for controlling the hydraulic pressure of the forward clutch based on the hydraulic pressure using the oil pump as a hydraulic source;
Pulley hydraulic control means for controlling the hydraulic pressure of the primary pulley and the secondary pulley of the continuously variable transmission based on the hydraulic pressure using the oil pump as a hydraulic source;
A stopper with which the movable sheave of the primary pulley abuts when the continuously variable transmission reaches a maximum gear ratio;
Maximum speed ratio detecting means for detecting that the speed ratio of the continuously variable transmission is the maximum speed ratio;
Idle stop determination means for performing an idle stop determination for stopping the engine when a predetermined condition is satisfied;
When the idle stop determination is made and the gear ratio of the continuously variable transmission is not the maximum gear ratio, the forward clutch is released and the primary clutch is released between the idle stop determination and the engine stop. And a control means for draining the hydraulic pressure of the pulley.

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