Vehicle transmission control device

Abstract

To provide a shift control device for a vehicle for executing clutch-to-clutch transmission in the state of slip-controlling a lock-up clutch without causing tie-up or racing.SOLUTION: A shift control device for the vehicle starts to increase a hydraulic pressure P9 of a second clutch in the state of transmitting torque while keeping a first clutch at a predetermined release side standby pressure, gradually reduces a hydraulic pressure P8 of the first clutch, and reduces the hydraulic pressure of the first clutch down to a predetermined release pressure in the state of maintaining the engagement pressure of the second clutch increased up to a predetermined engagement side standby pressure. When executing shift to release the first clutch and engage the second clutch in the state that a lock-up clutch is engaged with sliding, the shift control device for the vehicle corrects the release side standby pressure of the first clutch to be increased without correcting the hydraulic pressure of the second clutch to be increased before starting to increase it, and corrects the engagement side standby pressure of the second clutch to be increased without correcting the release pressure of the first clutch to be increased.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a device for controlling gear shifting in a vehicle equipped with a fluid coupling with a lock-up clutch capable of slip control, and more particularly to a gear shift control device that performs gear shifting by releasing one of the clutches and engaging another of the clutches. [Background technology]

[0002] A transmission equipped with a gear mechanism changes the torque transmission path by engaging or disengaging a friction-type engagement mechanism, thereby changing the gear ratio, which is the ratio between input and output rotational speeds. In other words, it performs gear changes. The engagement mechanism typically employs a clutch or brake (hereinafter collectively referred to as "clutch") that is configured to continuously change torque capacity using hydraulic pressure. Vehicle transmissions that perform gear changes by engaging or disengaging a clutch are not limited to stepped transmissions primarily composed of gear mechanisms. Transmissions with a belt-type continuously variable transmission and a gear transmission mechanism arranged in parallel are also known. In these types of transmissions, when a large gear ratio is required, such as when starting, torque is transmitted by the gear transmission mechanism, and once the vehicle speed has increased to a certain level, torque is transmitted by the continuously variable transmission mechanism. Therefore, when changing the form of torque transmission, one clutch is disengaged and another clutch is engaged.

[0003] Furthermore, vehicles equipped with an engine as a driving force source are provided with a torque converter that increases the engine's output torque, enables creep torque output, and suppresses engine vibration. Torque converters typically include a lock-up clutch to improve power transmission efficiency. Lock-up clutches are hydraulically engaged to transmit torque, allowing for continuous change in torque capacity. However, sudden engagement can cause shocks or deterioration of drivability. Patent Document 1 describes a device configured to control the hydraulic pressure of a lock-up clutch to prevent such deterioration of drivability.

[0004] The device described in Patent Document 1 is a transmission that can select and execute a gear change that changes the gear ratio continuously (steplessly) or a gear change that changes the gear ratio in steps, and is configured to control the lock-up clutch to a slip state when the vehicle starts to transfer torque via a fluid and via the lock-up clutch, and to control the engagement pressure of the lock-up clutch so that the engagement pressure of the lock-up clutch at this time tracks a target rotation speed in advance. Note that the transmission described in Patent Document 1 performs gear changes that change the gear ratio in steps between a continuously variable state and a so-called fixed stage that mechanically maintains a constant gear ratio by engaging and disengaging a clutch controlled by hydraulic pressure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 169396 Summary of the Invention [Problem to be solved by the invention]

[0006] The device described in Patent Document 1 controls the hydraulic pressure of a lock-up clutch that is controlled to a slip state when the vehicle starts, and controls the torque capacity, i.e., engagement pressure, of the lock-up clutch so that the input rotational speed, such as the engine speed, changes in accordance with a predetermined target rotational speed. This controls the torque capacity of a single friction engagement mechanism, but if the hydraulic pressure supplied to the two clutches described above during a gear change in which one of the clutches is released and the other is engaged is controlled uniformly as described in Patent Document 1, shock due to tie-up or a temporary and sudden increase in the rotational speed of the driving power source during a power-on gear change, known as "revving up," can occur, which can result in a deterioration in drivability.

[0007] This invention has been made with an eye on the above-mentioned technical problems, and aims to provide a gear change control device that can prevent or suppress tie-up and revving up of the driving force source when changing gears by controlling the lock-up clutch to a slip state immediately after the vehicle starts, while releasing one clutch and engaging another, so-called clutch change. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a third transmission for transmitting torque input from a fluid coupling with a lock-up clutch. 1. Friction engagement mechanism No. 2 friction engagement mechanism and 1 Friction engagement mechanism While the predetermined release side standby pressure is maintained and torque is transmitted, 2. Friction engagement mechanism The hydraulic pressure starts to increase and 1. Friction engagement mechanism The hydraulic pressure is gradually reduced and increased to a predetermined engagement side standby pressure. 2. Friction engagement mechanism While the engagement pressure is maintained, 1. Friction engagement mechanism A vehicle shift control device that reduces hydraulic pressure to a predetermined release pressure, wherein the lock-up clutch is engaged with slippage and the 1 Friction engagement mechanism Release and 2 friction engagement mechanism When performing a gear shift to engage the 1. Friction engagement mechanism Release side standby the hydraulic pressure to a level higher than the hydraulic pressure when the shift is performed to release the first friction engagement mechanism and engage the second friction engagement mechanism while the lock-up clutch is released, and to a level corresponding to the torque capacity of the lock-up clutch.Large correction and 2. Friction engagement mechanism Before hydraulic pressure increase begins The increase No major correction is made, and 2. Friction engagement mechanism Engagement side standby pressure The increase Large correction is made, and 1. Friction engagement mechanism Release pressure The increase It is characterized in that it is configured not to perform large corrections. [Effects of the Invention]

[0009] According to this invention, the lock-up clutch is maintained in a slip state to start the vehicle, and 1 Friction engagement mechanism Release and 2 friction engagement mechanism When the lock-up clutch is engaged to perform a gear change, even if the torque output from the fluid coupling is increased by slip control of the lock-up clutch, Each friction engagement mechanism Since the oil pressure is not increased uniformly but is increased and corrected according to the progress of the shift, tie-up and the shock that accompanies it, or the so-called revving up of the driving force source can be avoided or suppressed, thereby improving drivability. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a basic configuration of an example of a vehicle equipped with a stepped automatic transmission; [Figure 2] 3 is a flowchart illustrating an example of control executed in the embodiment of the present invention. [Figure 3] 5 is a time chart that schematically shows changes in command oil pressure of a release-side clutch and an engagement-side clutch, and changes in turbine rotation speed. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0012] A vehicle according to an embodiment of the present invention includes a fluid coupling with a lock-up clutch, and is configured to perform gear changes by disengaging one of two clutches or brakes (collectively referred to as "clutches"), which are friction engagement mechanisms whose torque capacity is controlled by hydraulic pressure, and engaging the other. This type of vehicle or transmission may be the vehicle or transmission described in International Publication No. 2017 / 169396 in which a belt-type continuously variable transmission mechanism and a gear transmission mechanism are provided in parallel on the output side of a torque converter with a lock-up clutch, or the vehicle or transmission described in Japanese Patent Application Laid-Open No. 2019-15327 in which creep torque can be output by a motor instead of a torque converter and a stepped gear transmission mechanism is provided downstream of the motor.

[0013] Figure 1 shows a schematic diagram of the basic configuration of an example of a vehicle equipped with a stepped automatic transmission. A driving force source 1 is composed of an internal combustion engine or a motor, and a fluid coupling (e.g., a torque converter) 3 having a lock-up clutch 2 is connected to the output side of the driving force source 1. The torque converter 3 and lock-up clutch 2 have the same configuration as conventionally known ones, and are configured to transmit torque via fluid between a pump impeller 4, which is an input member, and a turbine runner 5, which is an output member, and to mechanically connect the pump impeller 4 and the turbine runner 5 by the lock-up clutch 2. The stator in the torque converter 3 is omitted from the illustration.

[0014] Lockup clutch 2 is a friction clutch that is engaged by hydraulic pressure and whose torque capacity changes continuously according to the engagement pressure, and is equipped with a damper 6. Therefore, by controlling the torque capacity to be smaller than the input torque, lockup clutch 2 can transmit torque while allowing for a difference in rotation speed between the input-side member and the output-side member, i.e., while engaging with slippage.

[0015] A stepped gear transmission mechanism 7 is connected to the output side of the torque converter 3. This gear transmission mechanism 7 is, for example, a transmission mechanism having the configuration described in JP 2019-15327 A, and is configured to set a predetermined gear by engaging one of the clutches 8, and to set another gear by engaging another clutch 9 instead. Therefore, when shifting between these gears, the first clutch 8 is released and the second clutch 9 is engaged, or conversely, the first clutch 8 is engaged and the second clutch 9 is released, thereby performing a so-called clutch-to-clutch operation. An output shaft 10 of the gear transmission mechanism 7 is connected to a differential gear 11, which serves as a final reduction gear, and is configured to transmit drive torque from the differential gear 11 to left and right drive wheels 12.

[0016] The torque capacity control, including the engagement and disengagement of the lockup clutch 2, and the gear change (shift) control are configured to be performed electrically, and an electronic control unit (ECU) 13 is provided for this purpose. The electronic control unit 13 is primarily configured using a microcomputer including arithmetic elements and memory elements, and is configured to perform calculations using input data and pre-stored data, and to output the results of the calculations as control command signals. Examples of input data include the accelerator pedal position Acc, which is an example of a drive demand, the input rotation speed Ni and output rotation speed No of the gear transmission mechanism 7, the output rotation speed Ne of the drive power source 1, and the vehicle speed V. Examples of pre-stored data include a shift map that defines the gear position to be set according to the accelerator pedal position Acc and the vehicle speed V, and a lockup map that defines the engagement and disengagement of the lockup clutch 2 and the engagement state, including the slip state.

[0017] Each of the clutches 8, 9 in the gear transmission mechanism 7 is controlled to a torque capacity that adequately transmits the input torque. Therefore, when the input torque is large, the hydraulic pressure is increased compared to when the input torque is small. Meanwhile, in the torque converter 3, torque is increased according to the speed ratio, which is the ratio between the rotational speeds of its input and output sides. Furthermore, when the lock-up clutch 2 is controlled to be in a slip state, the output torque is greater than when it is released. Therefore, during gear shifting, the hydraulic pressure of each of the clutches 8, 9 is controlled according to the engagement state of the lock-up clutch 2, specifically, whether or not torque is being transmitted in a slip state. The gear shift control device in this embodiment of the present invention is configured to perform different correction controls for the hydraulic pressure of the release-side clutch and the engagement-side clutch during clutch-to-clutch gear shifting. This control is described below.

[0018] FIG. 2 is a flowchart illustrating an example of this control, which is executed by the electronic control unit 13 described above. In the control example shown in FIG. 2, first, it is determined whether or not gear change control is in progress (step S1). In the vehicle or transmission shown in FIG. 1, when the accelerator opening Acc or vehicle speed V changes so as to cross an upshift line or a downshift line in the gear change map, a gear change determination of an upshift or downshift is made, and the gear change is executed. That is, a command signal is output to release or engage one of the clutches. In step S1, it is determined whether or not such a gear change determination is made and the gear change is being executed. This determination can be made based on the operating state of the electronic control unit 13 itself.

[0019] If the answer to step S1 is NO, the routine shown in Fig. 2 is terminated without any particular control being performed. Conversely, if the answer to step S1 is YES, a determination is made as to whether or not the start-up flex lockup is in progress (step S2). That is, a determination is made as to whether or not the accelerator pedal (not shown) is depressed, causing the driving force source 1 to increase output torque, and whether or not the lockup clutch 2 is being controlled to a slip state. This determination can be made based on the accelerator opening Acc and the lockup map described above.

[0020] If the answer to the question in step S2 is affirmative, the torque capacity TL of the lock-up clutch 2 is calculated (step S3). TL=Te-C·Ne 2 -Top-inertia torque where Te is the torque of the engine which is the driving force source, C is the capacity coefficient of the torque converter 3, Ne is the engine speed, Top is the torque of the oil pump which is driven by the engine which is the driving force source, and the inertia torque is the inertia torque due to the lock-up clutch 2.

[0021] A clutch correction oil pressure is calculated according to the torque capacity TL of the lock-up clutch 2 calculated in this manner (Step S4). Because the lock-up clutch 2 has a torque capacity (torque) TL, the torque input to the gear transmission mechanism 7 increases compared to when the lock-up clutch 2 is disengaged. Therefore, a correction oil pressure is calculated to increase and correct the oil pressure of each clutch 8, 9 so that the increased torque can be reliably transmitted by each clutch 8, 9. Because the torque capacity of each clutch 8, 9 is approximately proportional to the oil pressure, a hydraulic pressure according to the torque capacity TL of the lock-up clutch 2 can be calculated as the correction oil pressure. If the answer to the above step S2 is negative, the process immediately proceeds to step S4. In that case, because the lock-up clutch 2 is disengaged and its torque capacity is zero, the clutch correction oil pressure is also zero, and no increase correction is made to the oil pressure of each clutch 8, 9.

[0022] Then, the hydraulic pressure of each of the clutches 8, 9 involved in the shift is increased by the clutch correction hydraulic pressure calculated in step S4 (step S5). This increase correction is performed on the standby pressure for the clutch on the release side at the beginning of the shift and the standby pressure for the clutch on the release side at the end of the shift. The details of this correction will be explained with reference to FIG. 3.

[0023] Figure 3 is a diagram that schematically shows the changes in the command oil pressure of the release clutch (assumed to be first clutch 8) and the engagement clutch (assumed to be second clutch 9) that perform a clutch-to-clutch shift, along with the turbine speed of the torque converter 3. In Figure 3, before the start of the shift, the first clutch 8 is engaged and its oil pressure P8 is as high as the line pressure, which is the source pressure of the hydraulic control device (not shown). The second clutch 9 is disengaged and its oil pressure P9 is almost zero.

[0024] When a shift decision is made and a shift is initiated (time t1), the hydraulic pressure of the first clutch 8 on the release side is first reduced to the release standby pressure. When the lock-up clutch 2 is under slip control, the release standby pressure is the increased corrected pressure described above, and is the pressure shown by the solid line in Figure 3. In contrast, if the lock-up clutch 2 does not have a torque capacity, no increase correction is made, and the release standby pressure is the pressure shown by the dashed line in Figure 3. The release standby pressure is a hydraulic pressure that results in a torque capacity that is approximately equal to the torque applied to the clutch 8, and is a pressure at which the clutch 8 will immediately begin to slip if the hydraulic pressure of the clutch 8 is slightly reduced from the release standby pressure.

[0025] Meanwhile, the oil pressure P9 of the second clutch 9 on the engaging side is temporarily increased to close the gap between the friction plates (so-called packing). This is a temporary increase in oil pressure control known as first fill. After that, torque is not transmitted, but if the oil pressure increases even slightly, it is set to an oil pressure sufficient to transmit torque. This oil pressure P9 is a certain level, as shown by the solid line in Figure 3, and is the same oil pressure as when the lock-up clutch 2 is controlled to a slip state without any increase correction, i.e., the same oil pressure as when the lock-up clutch 2 is disengaged.

[0026] Therefore, in the early stages of shifting, the release-side standby pressure of first clutch 8, which should be released, is increased, so first clutch 8 takes on and transmits the input torque, and no slip occurs in first clutch 8, preventing situations such as an increase in the engine speed, which is driving force source 1. Also, the torque capacity of second clutch 9, which should be engaged, is not increased in accordance with the torque capacity of lock-up clutch 2, so a so-called tie-up, in which both clutches 8, 9 have a certain degree of torque capacity, does not occur, and shock does not worsen.

[0027] After waiting for the oil pressure P9 of the on-coming second clutch 9 to stabilize at a predetermined low pressure, the oil pressure P9 of the second clutch 9 is gradually increased (at time t2). The target oil pressure is the on-coming standby pressure that has been increased and corrected in accordance with the torque capacity of the lock-up clutch 2. The increase gradient in the process of gradually increasing the oil pressure P9 of the second clutch 9 is a gradient that is predetermined, for example, in design. This change is shown by the solid line in Figure 3, and the oil pressure is higher than the oil pressure when the on-coming standby pressure is not increased and corrected (shown by the dashed line in Figure 3).

[0028] Also, immediately after starting to increase the oil pressure of second clutch 9, the oil pressure P8 of first clutch 8 on the release side is gradually reduced. The target oil pressure is the oil pressure set when shifting with lock-up clutch 2 released, i.e., the release clutch pressure without any increase correction. Also, oil pressure P8 of first clutch 8 is controlled so that the turbine rotation speed changes in accordance with a predetermined target rotation speed. Therefore, because the release standby pressure is the oil pressure that has been increased as described above, the oil pressure of second clutch 8 is higher than the oil pressure when the release standby pressure has not been increased (shown by the dashed line in Figure 3).

[0029] When the hydraulic pressure P9 of the on-coming second clutch 9 reaches the on-coming standby pressure that has been increased and corrected (at time t3), it is maintained at that on-coming standby pressure. In this state, the hydraulic pressure P8 of the disengaging first clutch 8 is reduced to a release clutch pressure (release pressure) that has no torque capacity. Therefore, at this point, the second clutch 9 will handle the torque. However, because the on-coming standby pressure (i.e., hydraulic pressure P9) is a hydraulic pressure that has been increased and corrected in response to controlling the lock-up clutch 2 to a slip state, slippage of the second clutch 9 and an increase in the engine speed (i.e., the driving force source 1) will not occur. Furthermore, even if the lock-up clutch 2 has the torque capacity TL described above, the hydraulic pressure P8 of the disengaging first clutch 8 is reduced to the release clutch pressure when the lock-up clutch 2 is disengaged. This prevents both clutches 8 and 9 from having a certain torque capacity, which is known as a "tie-up," and thus prevents the shock from worsening.

[0030] Then, at time t4 when the oil pressure P8 of the first clutch 8 has stabilized at the release clutch pressure, the oil pressure P9 of the second clutch 9 is increased to the engagement clutch pressure, which is approximately line pressure, and the gear shift is completed. Note that the change in turbine rotation speed shown in Figure 3 is the change in rotation speed when an upshift is performed, and begins to decrease as the first clutch 8, which is the release side, begins to slip. Then, the oil pressure P9 of the second clutch 9, which is the engagement side, increases and the second clutch 9 is almost completely engaged, so that the rotation speed reaches a value determined by the gear ratio after the gear shift, and then increases as the vehicle speed increases. [Explanation of symbols]

[0031] 1. Driving force source 2 Lock-up clutch 3 Torque converter 4 pump impeller 5 Turbine runner 6 Damper 7 Gear transmission mechanism 8,9 Clutch 10 Output shaft 11 Differential gear 12 drive wheels 13 Electronic control device

Claims

[Claim 1] A vehicle shift control device having a first friction engagement mechanism and a second friction engagement mechanism for transmitting torque input from a fluid coupling with a lock-up clutch, the device starting to increase oil pressure of the second friction engagement mechanism while maintaining the first friction engagement mechanism at a predetermined release side standby pressure to transmit torque, and gradually reducing the oil pressure of the first friction engagement mechanism, and reducing the oil pressure of the first friction engagement mechanism to a predetermined release pressure while maintaining the engagement pressure of the second friction engagement mechanism increased to the predetermined engagement side standby pressure, When a gear shift is performed in which the first friction engagement mechanism is disengaged and the second friction engagement mechanism is engaged while the lock-up clutch is engaged with slippage, an increasing correction is performed to increase the release-side standby pressure of the first friction engagement mechanism to a hydraulic pressure that is higher than the hydraulic pressure when the shift is performed in which the first friction engagement mechanism is released and the second friction engagement mechanism is engaged while the lock-up clutch is released and that corresponds to the torque capacity of the lock-up clutch, and the increasing correction is not performed before the increase in the hydraulic pressure of the second friction engagement mechanism starts; The increase correction is performed on the engagement side standby pressure of the second friction engagement mechanism, and the increase correction is not performed on the release pressure of the first friction engagement mechanism. A vehicle speed change control device characterized by being configured as follows.

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