JP2020125828A - Continuously variable transmission - Google Patents

Abstract

To provide a continuously variable transmission capable of reducing discomfort that may be felt by a driver.SOLUTION: A continuously variable transmission (CVT) 1 is provided between an engine 5 and a drive wheel, and determines a pulley ratio so that a vehicle speed becomes a target vehicle speed by referring to a road load shift line in which a target engine speed depending on the target vehicle speed is set in an auto cruise mode of keeping the vehicle speed at the target vehicle speed. When a driver updates the target vehicle speed, the CVT switches a shift characteristic referred to upon determining the pulley ratio to a shift line (shift characteristic for target vehicle speed update) having a characteristic that the target engine speed with respect to the same target vehicle speed becomes higher than the road load shift line.SELECTED DRAWING: Figure 1

Description

The present invention relates to a continuously variable transmission.

Patent Document 1 discloses a continuously variable transmission that controls a gear ratio according to a difference between a target vehicle speed set by a driver and an actual vehicle speed during cruise control operation, and performs feedback control so that the actual vehicle speed converges to the target vehicle speed. Is disclosed.

JP 2011-202565 JP

However, in the above-mentioned conventional continuously variable transmission, when the actual vehicle speed converges to the target vehicle speed at the time of updating the target vehicle speed by the driver, there is a risk of giving an uncomfortable feeling due to the delay in the acceleration/deceleration response of the vehicle.
One of the objects of the present invention is to provide a continuously variable transmission that can reduce a feeling of strangeness given to a driver.

The present invention refers to a shift characteristic for constant speed traveling in which a target engine rotation speed corresponding to the target vehicle speed is set during constant speed traveling, which is provided between the engine and driving wheels and maintains the vehicle speed at the target vehicle speed. Is a continuously variable transmission that determines the gear ratio so that the target vehicle speed is
When the driver updates the target vehicle speed, the target gear having a characteristic that the target engine rotation speed for the same target vehicle speed is higher than the constant speed traveling gear changing characteristic is referred to when determining the gear ratio. Switch to the shift characteristics for updating vehicle speed.

Therefore, in the present invention, when the vehicle speed is converged to the target vehicle speed when the driver updates the target vehicle speed, the target engine rotation speed becomes higher than the constant speed traveling speed change characteristic, so that the acceleration/deceleration feeling of the vehicle at the time of updating. Therefore, it is possible to reduce the uncomfortable feeling given to the driver due to the response delay.

1 is a schematic configuration diagram of a continuously variable transmission 1 of Embodiment 1. FIG. 3 is an example of a shift map for normal traveling mode according to the first embodiment. 3 is an example of a shift map for automatic cruise according to the first embodiment. 4 is an example of a target vehicle speed update shift map (during acceleration) according to the first embodiment. 3 is an example of a target vehicle speed update shift map (during deceleration) according to the first embodiment. 3 is a flowchart showing a flow of shift map switching processing according to the first embodiment. 6 is a time chart when accelerating when updating a target vehicle speed in CVT1 of the first embodiment. 7 is a time chart when decelerating at the time of updating the target vehicle speed in the CVT 1 of the first embodiment.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a continuously variable transmission (hereinafter referred to as “CVT”) 1 according to the first embodiment. The CVT 1 is provided between the engine 5 and drive wheels (not shown) in a vehicle that uses the engine 5 as a power source. The CVT 1 has a primary pulley 2 and a secondary pulley 3. Both pulleys 2 and 3 are arranged so that their grooves are aligned. A belt 4 is wound around the grooves of both pulleys 2 and 3. An engine 5 is arranged coaxially with the primary pulley 2, and a torque converter 6 and a forward/reverse switching mechanism 7 are provided between the engine 5 and the primary pulley 2 in this order from the engine 5 side.
The torque converter 6 includes a pump impeller 6a connected to the output shaft of the engine 5, a turbine runner 6b connected to the input shaft of the forward/reverse switching mechanism 7, a stator 6c, and a lockup clutch 6d.

The forward/reverse switching mechanism 7 has a double pinion planetary gear set 7a as a main component, a sun gear thereof is coupled to the turbine runner 6b of the torque converter 6, and a carrier thereof is coupled to the primary pulley 2. The forward/reverse switching mechanism 7 further includes a starting clutch 7b that directly connects the sun gear and the carrier of the double pinion planetary gear set 7a, and a reverse brake 7c that fixes the ring gear. When the start clutch 7b is engaged, the input rotation from the engine 5 via the torque converter 6 is transmitted to the primary pulley 2 as it is, and when the reverse brake 7c is engaged, the input rotation from the engine 5 via the torque converter 6 is reversed. , To the primary pulley 2.

The rotation of the primary pulley 2 is transmitted to the secondary pulley 3 via the belt 4, and the rotation of the secondary pulley 3 is transmitted to the drive wheels via the output shaft 8, the gear set 9 and the differential gear device 10. In order to change the pulley ratio (gear ratio) between the primary pulley 2 and the secondary pulley 3 during the above power transmission, one of the conical plates forming the groove of the primary pulley 2 and the secondary pulley 3 is fixed. 2a and 3a, and the other conical plates 2b and 3b are movable conical plates that can be displaced in the axial direction. These movable conical plates 2b, 3b are urged toward the fixed conical plates 2a, 3a by supplying the primary pressure and the secondary pressure created by using the line pressure as the source pressure to the primary pulley chamber 2c and the secondary pulley chamber 3c, As a result, the belt 4 is frictionally engaged with the conical plate to transmit power between the primary pulley 2 and the secondary pulley 3.

The gear shift of the CVT 1 is performed by changing the groove widths of the pulleys 2 and 3 by the pressure difference between the primary pressure and the secondary pressure, and continuously changing the diameter of the winding arc of the belt 4 around the pulleys 2 and 3. The primary pressure and the secondary pressure are controlled by the shift control hydraulic circuit 11 together with the hydraulic pressure supplied to the starting clutch 7b that is engaged when the forward travel range is selected and the reverse brake 7c that is engaged when the reverse travel range is selected. The shift control hydraulic circuit 11 performs control in response to a signal from the transmission controller 12.

The transmission controller 12 includes a signal from the primary rotation speed sensor 13 that detects the primary rotation speed of the primary pulley 2 of the CVT 1 and a secondary rotation speed of the secondary pulley 3 of the CVT 1 (note that the secondary rotation speed includes the final reduction ratio and the tire (The vehicle speed can be calculated using specifications such as diameter) A signal from the secondary rotation speed sensor 14 that detects the primary pressure, a signal from the primary pressure sensor 15p that detects the primary pressure, and a secondary pressure sensor 15s that detects the secondary pressure. Signal, a signal from the accelerator opening sensor 16 that detects the accelerator opening, a selection range signal from the inhibitor switch 17 that detects the select lever position, and a signal from the brake switch 18 that detects whether or not the brake pedal is depressed. And a signal relating to the operating state of the engine 5 (engine rotation speed, engine torque, fuel injection time, cooling water temperature, etc.) from the engine controller 19 that controls the engine 5.

The transmission controller 12 sets the target input rotation speed according to the vehicle speed (secondary rotation speed) and the accelerator opening by referring to the shift map for the normal traveling mode as shown in FIG. 2, and the primary rotation speed is the target input rotation speed. Control to follow the speed. Note that setting the target input rotation speed is synonymous with setting the target pulley ratio (target gear ratio). This is because the pulley ratio is a value obtained by dividing the secondary rotation speed by the primary rotation speed, and the secondary rotation speed is a value uniquely determined by the vehicle speed. Also, when controlling the pulley ratio, set the target primary pressure and target secondary pressure so that the pulley pressing force required to transmit the input torque of CVT1 determined by the engine torque and the torque converter torque ratio is obtained. The feedback control is performed so that the actual primary pressure and the actual secondary pressure follow the target pressure. Further, when a predetermined condition indicating an abnormality is satisfied, a lighting command is output to the lamp 20 capable of notifying the driver of the abnormality.

The vehicle according to the first embodiment has an auto cruise (constant speed travel) function for automatically traveling the vehicle at a target vehicle speed as a partially automatic driving function (level 2). When the driver performs the auto cruise operation, after turning on the main switch 21 for selecting the auto cruise mode, visually confirming that the desired speed is reached with the speedometer, and manually operating (turning on) the set switch 22. .. As a result, the vehicle speed when the set switch 22 is turned on is set as the target vehicle speed in the auto cruise mode. When the target vehicle speed is set in the auto cruise mode, the transmission controller 12 sets the target input rotation speed according to the target vehicle speed by referring to the shift map for auto cruise of FIG. 3, and the actual input rotation speed is the target. Change the pulley ratio of both pulleys 2 and 3 so that the input rotation speed is achieved. In the auto cruise mode, the engine controller 19 controls the output of the engine 5 according to the target input rotation speed set by the transmission controller 12.

In the shift map of FIG. 3, a road load shift line (constant speed running shift characteristic) for determining a target engine rotation speed according to a target vehicle speed is set. The road load shift line is set to a target engine rotation speed for maintaining a balance between the vehicle load and the driving force with respect to the target vehicle speed. That is, the road load shift line is a shift line when the driving force necessary for traveling at a constant vehicle speed at a constant accelerator opening is output. The road load shift line has a characteristic that the target input rotation speed with respect to the same target vehicle speed becomes higher as the slope of the uphill road becomes larger.

When the driver depresses the accelerator pedal or the brake pedal or turns off the main switch 21 during the auto cruise mode, the auto cruise mode is released and the mode shifts to the normal traveling mode. The transmission controller 12 switches the shift map referred to when determining the target input rotation speed from the automatic cruise shift map to the normal travel mode shift map.
When the driver presses the up switch 23 or the down switch 24 during the auto cruise mode, the transmission controller 12 updates the target vehicle speed. For example, each time the up switch 23 or the down switch 24 is pressed, the target vehicle speed is switched from the current target vehicle speed to a value higher or lower by a certain range. The amount of change from the target vehicle speed may be increased in proportion to the time that the up switch 23 or the down switch 24 is continuously pressed.

In the first embodiment, when the driver updates the target vehicle speed, the transmission controller 12 aims to reduce the discomfort given to the driver when changing the pulley ratio so that the vehicle speed becomes the target vehicle speed. When the target vehicle speed is updated by the driver, the shift map referred to when determining the target input rotation speed is switched from the automatic cruise shift map to the target vehicle speed update shift map as shown in FIG. 4 or 5. .. FIG. 4 is an acceleration shift map for acceleration, that is, when the updated target vehicle speed is higher than the actual vehicle speed, and FIG. 5 is for deceleration, that is, deceleration when the updated target vehicle speed is lower than the actual vehicle speed. It is a gear shift map.

In the target vehicle speed update time shift map, a shift line (target vehicle speed update time shift characteristic) for determining a target engine rotation speed according to the target vehicle speed is set. The shift line has a characteristic that when the target vehicle speed is updated, the larger the absolute value of the speed difference obtained by subtracting the actual vehicle speed from the updated target vehicle speed, the higher the target input rotation speed for the same target vehicle speed. Further, the shift line has a characteristic that the target input rotation speed for the same target vehicle speed becomes higher than the road load shift line in the automatic cruise shift map shown in FIG. Further, the shift line for acceleration has a characteristic that the target input rotation speed for the same target vehicle speed is higher than that of the shift line for deceleration. The target input rotation speed on the shift line for acceleration is set to a value that gives an engine rotation speed that gives the driver a feeling of acceleration and does not make the driver feel noise. The target input rotation speed in the shift line for deceleration is set to a value at which the driver can obtain an engine rotation speed that gives the driver a feeling of engine braking that suppresses the engine from rising.
The transmission controller 12 switches the shift map referred to when determining the target input rotation speed from the shift map for auto cruise to the shift map for updating the target vehicle speed, and then the absolute value of the speed difference is a predetermined value close to zero. When the target input rotation speed is decreased, the shift map referred to when determining the target input rotation speed is returned to the automatic cruise shift map. The predetermined value to be returned to the automatic cruise shift map is set to a value at which an overshoot of the input rotation speed is unlikely to occur even if the target input rotation speed changes stepwise by switching the shift map. The higher the target input rotation speed, the larger the predetermined value may be. Further, the larger the absolute value of the speed difference obtained by subtracting the actual vehicle speed from the target vehicle speed updated by the driver, the larger the predetermined value may be.

FIG. 6 is a flowchart showing the flow of the shift map switching process of the first embodiment. This process is repeatedly executed by the transmission controller 12 at a predetermined calculation cycle.
In step S1, it is determined whether or not the main switch 21 for selecting the auto cruise mode is on. If YES, the process proceeds to step S2, and if NO, the process proceeds to step S8.
In step S2, the shift map for automatic cruise is selected as the shift map to be referred to when determining the target input rotation speed.
In step S3, it is determined whether or not the target vehicle speed has been updated by the driver. If YES, the process proceeds to step S4, and if NO, the process returns to step S1.

In step S4, it is determined whether the speed difference is a positive value. If YES, the process proceeds to step S5, and if NO, the process proceeds to step S6.
In step S5, the target vehicle speed update shift map for acceleration is selected as the shift map to be referred to when determining the target input rotation speed.
In step S6, the target vehicle speed update shift map for deceleration is selected as the shift map to be referred to when determining the target input rotation speed.
In step S7, it is determined whether the absolute value of the speed difference is less than or equal to a predetermined value. If YES, the process returns to step S2, and if NO, the process returns to step S4.
In step S8, the normal travel mode shift map is selected as the shift map to be referred to when determining the target input rotation speed.

Next, the function and effect of the first embodiment will be described.
In the conventional continuously variable transmission, the pulley ratio is feedback-controlled so that the actual vehicle speed converges to the target vehicle speed during the auto cruise mode. Specifically, the required torque is calculated from the speed difference between the target vehicle speed and the actual vehicle speed, the virtual accelerator opening is generated based on the required torque and the engine rotation speed, and the target input according to the virtual accelerator opening and the actual vehicle speed is input. The pulley ratio is controlled so that the rotation speed is achieved. For this reason, when the actual vehicle speed converges to the target vehicle speed when the target vehicle speed is updated, the pulley ratio becomes large in the initial stage where the speed difference is large, and the engine blows up. After that, as the speed difference converges, the pulley ratio decreases, so that the vehicle acceleration gradually decreases. In other words, in the above-mentioned conventional technology, since the pulley ratio is constantly changed according to the speed difference, the engine does not have a feeling of acceleration for the engine to blow up, and it takes time for the actual vehicle speed to reach the target vehicle speed. It feels strange to the driver.

On the other hand, in the CVT 1 according to the first embodiment, when the driver updates the target vehicle speed during the auto cruise mode, the shift map referred to when determining the target input rotation speed is changed from the auto cruise shift map when the target vehicle speed is updated. The above problem was solved by switching to the shift map for use.
FIG. 7 is a time chart when accelerating when updating the target vehicle speed in the CVT 1 of the first embodiment.
At time t1, the target vehicle speed is updated by the driver, so the shift map referred to when determining the target input rotation speed is switched from the automatic cruise shift map to the target vehicle speed update shift map for acceleration. As a result, the target input rotation speed is stepwise switched from the value on the load/road shift line to the value on the shift line in the target vehicle speed update shift map for acceleration.

In the section from the time t1 to the time t2, the target input rotation speed is increased stepwise, so that the downshift is started and the engine rotation speed rises rapidly. As a result, the responsiveness of the vehicle in the initial stage of acceleration can be improved, and a feeling of acceleration can be produced. Further, the driver can be notified of the start of acceleration due to a downshift by the engine sound or a change in acceleration. Furthermore, since the engine rotation speed is kept constant after the actual input rotation speed reaches the target input rotation speed, the acceleration of the vehicle is stabilized and the actual vehicle speed can be quickly increased to the target vehicle speed.

Here, in Japanese Patent Laid-Open No. 2-216328, when the absolute value of the updated speed difference between the target vehicle speed and the actual vehicle speed is larger than a threshold value, the gear stage of the stepped transmission is changed from the first gear stage. A technique for switching to a second speed that obtains a lower vehicle speed is disclosed. However, while the driver expects a larger acceleration as the updated target vehicle speed is higher, in the above-described conventional technique, the speed is always switched to a constant gear regardless of the speed difference, so that the acceleration that meets the driver's request is increased. Is not obtained, and the driver feels uncomfortable. On the other hand, in the target vehicle speed update shift map of the first embodiment, the larger the absolute value of the speed difference obtained by subtracting the actual vehicle speed from the updated target vehicle speed, the higher the target input rotation speed for the same target vehicle speed is set. Since a different shift line is selected, it is possible to realize an acceleration that matches the driver's request and reduce a feeling of strangeness given to the driver.
At time t3, since the absolute value of the speed difference has decreased to a predetermined value close to zero, the shift map to be referred to when determining the target input rotation speed is changed from the shift map for updating the target vehicle speed for acceleration to the shift map for auto cruise. Return to. As a result, the target input rotation speed changes stepwise from the value on the shift line in the target vehicle speed update shift map to the value on the road load shift line. As a result, the driver can be notified of the end of acceleration by the engine sound or the change in acceleration.
At time t4, the actual vehicle speed reaches the target vehicle speed.

FIG. 8 is a time chart when decelerating when updating the target vehicle speed in the CVT 1 of the first embodiment.
At time t1, the target vehicle speed is updated by the driver, so the shift map referred to when determining the target input rotation speed is switched from the automatic cruise shift map to the target vehicle speed update shift map for deceleration. As a result, the target input rotation speed is stepwise switched from the value on the load/load shift line to the value on the shift line in the target vehicle speed update shift map for deceleration.
In the section from time t1 to time t2, the target input rotation speed increases stepwise, so that the downshift is started and the engine rotation speed rises rapidly.

Here, if the target input rotation speed is determined based on the load/load shift line without switching the shift map, the engine brake is small, so the driver feels a delay in the deceleration response, and the actual vehicle speed is the target vehicle speed. Takes longer to reach. On the other hand, in the first embodiment, since sufficient engine braking can be obtained, the responsiveness of the vehicle at the initial stage of deceleration can be improved and a deceleration feeling can be produced. Further, the driver can be notified of the start of deceleration due to the downshift by the engine sound or the change in deceleration. Furthermore, after the actual input rotation speed reaches the target input rotation speed, the engine rotation speed is kept constant, so that the deceleration of the vehicle becomes stable and the actual vehicle speed can be reduced to the target vehicle speed early.

In the shift line of the target vehicle speed update shift map, the target input rotation speed is set to a higher value as the target vehicle speed is lower, so the driver expects a larger deceleration as the updated target vehicle speed is lower. On the other hand, it is possible to realize deceleration that matches the driver's request.
At time t3, since the absolute value of the speed difference has decreased to a predetermined value close to zero, the shift map referred to when determining the target input rotation speed is changed from the shift map for updating the target vehicle speed for deceleration to the shift map for auto cruise. Return to. As a result, the target input rotation speed changes stepwise from the value on the shift line in the target vehicle speed update shift map to the value on the road load shift line. As a result, the driver can be notified of the deceleration end by the engine sound or the change in acceleration.
At time t4, the actual vehicle speed reaches the target vehicle speed.

As described above, in the first embodiment, the effects listed below are exhibited.
(1) In the auto cruise mode, which is provided between the engine 5 and the drive wheels to keep the vehicle speed at the target vehicle speed, refer to the road load shift line in which the target engine speed is set according to the target vehicle speed, CVT1 that determines the pulley ratio so that when the driver updates the target vehicle speed, the transmission controller 12 refers to the shift characteristic that is referred to when determining the pulley ratio as the target engine speed for the same target vehicle speed. However, the shift line is changed to a shift line having a characteristic higher than the road load shift line (shift characteristic for updating the target vehicle speed). As a result, when the vehicle speed converges to the target vehicle speed when the driver updates the target vehicle speed, the pulley ratio is maintained constant regardless of the change in the difference between the target vehicle speed and the actual vehicle speed, so that the driver's discomfort can be reduced. ..

(2) The target vehicle speed updating gear shift characteristic has a characteristic that the larger the difference between the updated target vehicle speed and the actual vehicle speed, the higher the target engine rotation speed for the same target vehicle speed than the road load shift line. As a result, acceleration/deceleration that matches the driver's request can be realized.

(3) The target vehicle speed update gear shifting characteristics are the acceleration shift line that is referred to when the speed difference obtained by subtracting the actual vehicle speed from the updated target vehicle speed is a positive value, and the negative speed difference value. The deceleration shift line referred to in this case has a characteristic that the target engine rotation speed for the same target vehicle speed is higher than the deceleration shift line. In addition to the braking force of the engine brake at the time of deceleration, the braking force by the brake system of the vehicle can be applied, while at the time of acceleration, it is necessary to generate the driving force only by the output of the engine 5. Therefore, by increasing the target engine rotation speed for the same target vehicle speed during acceleration than during deceleration, the actual vehicle speed can be increased to the target vehicle speed earlier during acceleration.

(4) When the actual vehicle speed reaches the target vehicle speed and the speed difference becomes equal to or less than a predetermined value before the actual vehicle speed reaches the target vehicle speed, the transmission controller 12 uses the speed change characteristic referred to when determining the pulley ratio as the load/load speed change line. return. As a result, fluctuations in vehicle speed due to overshoot of the input rotation speed can be suppressed.

(5) Road The road speed change line is set to a target engine speed for maintaining a balance between the vehicle load and the driving force with respect to the target vehicle speed. As a result, quiet and smooth acceleration/deceleration can be realized in the auto cruise mode.

1 CVT (continuously variable transmission)
5 engine
12 Transmission controller

Claims (5)

When the vehicle is traveling at a constant speed that is provided between the engine and the drive wheels and maintains the vehicle speed at the target vehicle speed, the target engine speed is set according to the target vehicle speed. A continuously variable transmission that determines the gear ratio so that
When the driver updates the target vehicle speed, the target gear having a characteristic that the target engine rotation speed for the same target vehicle speed is higher than the constant speed traveling gear changing characteristic is referred to when determining the gear ratio. A continuously variable transmission that switches to the shifting characteristics for updating vehicle speed. The continuously variable transmission according to claim 1,
The target vehicle speed update shift characteristic has a characteristic that the target engine rotation speed with respect to the same target vehicle speed becomes higher than the constant speed travel shift characteristic as the difference between the updated target vehicle speed and the actual vehicle speed increases. Gearbox. The continuously variable transmission according to claim 1,
The target vehicle speed update speed change characteristic is referred to when the speed difference obtained by subtracting the actual vehicle speed from the updated target vehicle speed has a positive value, and the acceleration speed change characteristic referred to when the speed difference has a negative value. And a speed change characteristic for deceleration,
The continuously variable transmission having the acceleration shift characteristic having a target engine rotation speed higher than the deceleration shift characteristic for the same target vehicle speed. The continuously variable transmission according to any one of claims 1 to 3,
A continuously variable transmission that restores the speed change characteristic referred to when determining the speed change ratio to the constant speed traveling speed change characteristic before the actual vehicle speed reaches the target vehicle speed. The continuously variable transmission according to any one of claims 1 to 4,
The continuously variable transmission in which the target engine rotation speed for maintaining the balance between the load and the driving force of the vehicle is set with respect to the target vehicle speed as the shift characteristic for constant speed traveling.

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