Shift control device for a stepped transmission

Abstract

To perform a power-on downshift accompanying traveling on an uphill road without deteriorating a gear shock and gear responsiveness.SOLUTION: When an on / down-shift for switching a gear change stage to a lower-speed side gear change stage at a requirement of an increase of a required drive force is determined (Step S1), a gear change control device of a stepped transmission determines that a vehicle is traveling on an uphill road (Steps S3 to S6). When the determination that the vehicle is traveling on the uphill road is established, the gear change control device sets a command value of the release hydraulic pressure of an engagement mechanism which is released by an on / down-shift to a command value based on an increase correction value of torque which is applied to the engagement mechanism that is a command value which is larger than a command value at the on / down-shift for switching the gear change stage to a lower speed side when the vehicle is traveling on a flat road in a state that there is no increase requirement of the required drive force (Step S7), and elongates a time of an inertia phase of the on / down-shift longer than a time of an inertia phase at the on / down-shift on the flat road (Step 8).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a device for controlling a stepped transmission (automatic transmission) that sets a plurality of shift stages according to the engaged and released states of an engagement mechanism such as a clutch or a brake, and more particularly to a device for controlling downshifts.

Background Art

[0002] In a vehicle automatic transmission, in order to maintain the engine speed at a fuel-efficient speed and output the required driving force, the shift stage is determined according to the accelerator opening, vehicle speed, etc. As the accelerator opening, vehicle speed, etc. change, an upshift that reduces the gear ratio or a downshift that increases the gear ratio is executed. Since shifting is a change in the operating state that causes a change in the rotational speed of the rotating members in the drive system including the engine, a shock may occur due to inertial torque or the like. Patent Document 1 describes a device configured to execute a power-on downshift that increases the gear ratio while maintaining the engine in a driving state without worsening the shock.

[0003] The device described in Patent Document 1 is configured to control downshifting when the vehicle decelerates gradually and stops while traveling on an uphill road. When going uphill, in order to overcome the gravitational acceleration and move forward, the accelerator pedal is depressed even slightly, and the engine outputs a driving force so that the vehicle does not reverse. On the other hand, the vehicle speed is gradually decreasing so as to stop at a predetermined position ahead. Therefore, when the vehicle speed changes so as to cross the downshift line stored in advance as a map, the determination of downshifting is established and downshifting is executed. The downshifting assumed by the device described in Patent Document 1 is a so-called clutch-to-clutch shift that releases the engagement mechanism engaged in the high-speed gear stage and engages the engagement mechanism for setting the low-speed gear stage. In the case of power-on downshifting in clutch-to-clutch shifting, if the torque capacity of the release-side engagement mechanism decreases (releases) quickly, a surge occurs in which the engine speed suddenly increases due to power-on, which may cause a shock. Therefore, in the invention described in Patent Document 1, the release time of the engagement mechanism is lengthened to slowly release the engagement mechanism. That is, the rate of decrease in the sweep-down instruction hydraulic pressure of the engagement mechanism is reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As in the apparatus of Patent Document 1, if the hydraulic pressure of the engagement mechanism released during power-on downshift is swept down, the torque received (or supported torque, shared torque) by the engagement mechanism gradually decreases, so that shift shock can be suppressed. On the other hand, since the progress of shifting becomes slow, there is room for improvement in terms of shift responsiveness. Therefore, it is conceivable to set the hydraulic pressure (release pressure) of the engagement mechanism to be released low and improve the deterioration of shift responsiveness caused by sweeping down the hydraulic pressure. In this way, when performing a power-on downshift on a flat road or when the accelerator pedal is depressed during a coast-down shift resulting in a power-on downshift, the time required for releasing the engagement mechanism is shortened, and the shift delay caused by the sweep-down of the release hydraulic pressure can be improved. However, when downshifting as the vehicle speed gradually decreases while driving on an uphill road, the accelerator pedal is already depressed to a certain extent and is in a power-on state in order to climb the slope or prevent the vehicle from reversing on the uphill road. In such a state, if the release pressure is set low to improve the shift responsiveness associated with the sweep-down of the release pressure, the change in the rotational speed becomes abrupt due to the power-on associated with the uphill road, and the shift shock may deteriorate.

[0006] This invention has been made paying attention to the above technical problems, and an object thereof is to provide a shift control device capable of performing a power-on downshift associated with driving on an uphill road without deteriorating shift shock and shift responsiveness.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention provides a shift control device for a stepped transmission that sets a gear stage by a plurality of engagement mechanisms whose engagement and release are hydraulically controlled, and selects a gear stage to be set based on at least two data of a required driving force and an output rotational speed. When it is determined that a downshift to a lower-speed gear stage is to be performed under an increasing demand for the required driving force, it is determined whether the vehicle is traveling on an uphill road. When it is determined that the vehicle is traveling on an uphill road, the command value of the release hydraulic pressure of the engagement mechanism released by the downshift is set to be larger than the command value during a downshift to the lower-speed gear stage when traveling on a flat road without an increasing demand for the required driving force, and is a command value based on an increase correction value of the torque applied to the engagement mechanism. Also, the inertia phase The target time during is set to be long and before according to the difference in the input rotation speed before and after the downshift, and the release hydraulic pressure is controlled so that the inertia phase ends at the target time the downshift is configured to be longer than the time of the inertia phase of the downshift on the flat road described above. [Fig. 1] This is the gist of the present invention.

Advantages of the Invention

[0008] According to the shift control device of the present invention, when performing an up-down shift while driving on an uphill road, the command value of the release hydraulic pressure of the engagement mechanism to be released is made larger than the command value during a so-called normal up-down shift on a flat road. In addition, the time of the inertia phase is made longer than in the case of a normal up-down shift. Therefore, even if the input rotation speed is about to increase in accordance with an increase in the required driving force, since the release hydraulic pressure is higher than that in the case of a normal up-down shift, an abrupt increase in the input rotation speed is avoided or suppressed. As a result, even if the downshift line in the shift map for determining the gear stage is set on the low vehicle speed side, shift shock caused by an up-down shift can be avoided or suppressed. Also, even if the time of the inertia phase is made longer, the shift time does not become longer compared to the case where the release hydraulic pressure command value is not increased and corrected as described above, and the shift responsiveness does not deteriorate particularly. Rather, since the downshift line can be set on the low vehicle speed side, the shift responsiveness of the power-on downshift on a flat road based on the downshift line and the power-on downshift during a coast downshift can be improved.

Brief Description of the Drawings

[0009] [Fig. 2] It is a skeleton diagram showing an example of the gear train of a stepped transmission in an embodiment of the present invention. [Fig. 3] It is a flowchart for explaining an example of the control executed by the shift control device of the present invention. ​ It is a time chart schematically showing an example of the change in the release instruction hydraulic pressure when the control is executed.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0011] First, an example of a stepped automatic transmission that is a control target in an embodiment of the present invention will be described. FIG. 1 is a skeleton diagram schematically showing a gear train in an automatic transmission configured to be able to set 10 forward speeds and 1 reverse speed, and is mainly composed of a Ravigneaux type planetary gear mechanism 1, two sets of single pinion type planetary gear mechanisms 2 and 3, and a plurality of engagement mechanisms. The Ravigneaux type planetary gear mechanism (hereinafter, temporarily referred to as the first planetary gear mechanism) 1 includes a first sun gear S1, a second sun gear S2, a long pinion gear P1 meshing with the first sun gear S1, a short pinion gear P2 meshing with the long pinion gear P1 and the second sun gear S2, a carrier C1 holding the long pinion gear P1 and the short pinion gear P2, and a ring gear R1 disposed concentrically with each of the sun gears S1 and S2 and meshing with the long pinion gear P1. The carrier C1 serves as an input element and is connected to the input shaft 4.

[0012] Note that the input shaft 4 is connected to an engine (not shown in each case) via a torque converter. The rotational speed of the input shaft 4 is the input rotational speed, and the torque transmitted from the input shaft 4 is the input torque. The first sun gear S1 is connected to a predetermined fixed portion 5 such as a casing via a first brake B-1, and when the first brake B-1 engages, the first sun gear S1 is fixed and a reaction torque acts on the first sun gear S1.

[0013] Each of the single pinion type planetary gear mechanisms 2 and 3 is disposed on the same axis as the above-described input shaft 4 and the first planetary gear mechanism 1. One of the single pinion type planetary gear mechanisms (hereinafter, temporarily referred to as the second planetary gear mechanism) 2 includes a sun gear S20, a ring gear R20 disposed concentrically with the sun gear S20, and a carrier C20 holding a pinion gear P20 meshing with the sun gear S20 and the ring gear R20. The carrier C20 serves as an output element and is connected to the output shaft 6.

[0014] The output shaft 6 is configured to output driving torque to the driving wheels via a propeller shaft and a differential gear (not shown). Similarly, the other single pinion type planetary gear mechanism (hereinafter temporarily referred to as the third planetary gear mechanism) 3 has a sun gear S30, a ring gear R30 arranged concentrically with the sun gear S30, and a carrier C30 that holds a pinion gear P30 meshing with the sun gear S30 and the ring gear R30. The sun gear S30 is configured to rotate integrally with the sun gear S20 in the second planetary gear mechanism 2. The carrier C30 is connected to the input shaft 4 described above and serves as an input element.

[0015] As an engagement mechanism for connecting the above-described rotating elements, in addition to the first brake B-1, the following four clutches C-1, C-2, C-3, C-4 and the second brake B-2 are provided. That is, the first clutch C-1 is configured to selectively connect the ring gear R1 in the first planetary gear mechanism 1, the sun gear S20 in the second planetary gear mechanism 2, and the sun gear S30 in the third planetary gear mechanism 3. The second clutch C-2 is configured to selectively connect the second sun gear S2 in the first planetary gear mechanism 1, the sun gear S20 in the second planetary gear mechanism 2, and the sun gear S30 in the third planetary gear mechanism 3.

[0016] The third clutch C-3 is configured to selectively connect the ring gear R1 in the first planetary gear mechanism 1 and the ring gear R20 in the second planetary gear mechanism 2. Further, the fourth clutch C-4 is configured to selectively connect the carrier C20 or the output shaft 6 in the second planetary gear mechanism 2 and the ring gear R30 in the third planetary gear mechanism 3. The second brake B-2 is provided between the ring gear R20 in the second planetary gear mechanism 2 and a predetermined fixed portion 5 and is configured to selectively fix the ring gear R20.

[0017] These clutches C-1, C-2, C-3, C-4 and brakes B-1, B-2 may be engagement mechanisms of an appropriate type such as friction type or meshing type. However, in the gear train shown in FIG. 1, at least the first clutch C-1 and the first brake B-1 are constituted by a friction type engagement mechanism capable of controlling the torque capacity by hydraulic pressure. Then, by engaging and releasing these engagement mechanisms as shown in the engagement operation table of Table 1, it is possible to set ten forward speeds and one reverse speed. In Table 1, the "○" mark indicates engagement, and the blank space indicates release and non-transmission of torque. Also, "OD" indicates an overdrive gear where the gear ratio is less than "1".

Table 1

[0018] An electronic control unit (ECU) 7 is provided for performing so-called shift control to set a predetermined shift stage by engaging and releasing each of the above engagement mechanisms. The ECU 7 is a so-called microcomputer mainly composed of a CPU and various memories, and performs calculations based on data obtained by various sensors (not shown) and data stored in advance, and is configured to output the result of the calculation as a control command signal.

[0019] Examples of the input data include the input rotational speed represented by the rotational speed of the input shaft 4, the output rotational speed such as the vehicle speed represented by the rotational speed of the output shaft 6, the required driving force represented by the accelerator opening which is the depression amount of the accelerator pedal (not shown), the oil temperature which is the temperature of the oil for controlling the engagement mechanism, and the longitudinal and lateral accelerations of the vehicle equipped with the above gear train.

[0020] Also, as an example of data stored in advance, a shift diagram that defines the regions of each gear stage by upshift lines and downshift lines using the output rotational speed (vehicle speed) and the required driving force (accelerator opening) as parameters, thresholds for gear stages for determining an uphill road, as well as thresholds for output rotational speed, throttle opening, and longitudinal and lateral accelerations, correction time for the inertia phase, correction values for hydraulic pressure command values of engagement mechanisms to be released when performing a predetermined shift, and the like.

[0021] The shift control device according to an embodiment of the present invention is configured to execute a downshift (on downshift) when the vehicle speed is gradually decreasing and a stop is assumed while the required driving force is increasing from a predetermined state such as idling, on an uphill road, with a control different from that of a power-on downshift on a flat road. FIG. 2 is a flowchart for explaining an example of such control, which is executed by the aforementioned ECU7, and thus the ECU7 serves as a controller for shift control.

[0022] The control shown in FIG. 2 is executed, for example, when the vehicle is running. First, when there is an on downshift determination (step S1), corrections based on the oil temperature and the re-rotational speed for the torque (shared torque) applied to the release clutch are reflected in the control command value (step S2).

[0023] Here, an on downshift is a shift that increases the gear ratio in a state where a driving force greater than the idling state is required, such as when an accelerator pedal (not shown) is depressed (i.e., under a request for an increase in the required driving force). Specifically, when the accelerator opening or throttle opening increases and the driving state determined by the vehicle speed and the required driving force changes across the downshift line in the shift diagram, or when the vehicle speed decreases and the driving state changes across the downshift line in the shift diagram, the determination of an on downshift is established.

[0024] The release clutch, which is the object of correction in step S2, is a clutch that is released by executing the shift for which the determination was made in step S1. In particular, when the shift determined in step S1 is a so-called clutch-to-clutch shift, it is the clutch on the release side. While the release clutch regulates the progress of the shift, the torque capacity according to the shared torque is affected by the temperature of the oil supplied to or discharged from the release clutch, and also requires correction according to the rotational speed associated with the correction of the release pressure. Therefore, in step S2, correction is performed based on the input (or detected) data.

[0025] Next, it is determined whether it is an uphill road. Upshift or downshift on an uphill road, similar to the downshift on a flat road, may be a downshift assuming or aiming for a stop, and in that case, different control will be performed compared to the downshift on a flat road, so it is determined whether it is an uphill road. Therefore, this determination is, in other words, a determination based on the downshift on a flat road as to whether correction of the control content is necessary.

[0026] In the determination of an uphill road, first, it is determined whether the current gear position is on the lower speed side (gear position with a larger gear ratio) than a predetermined gear position A (step S3). As an example, the predetermined gear position A serving as this determination criterion may be the third or fourth gear position in the case of the above-described 10-speed forward transmission. Also, it is determined whether the output rotational speed (output rpm) No such as the rotational speed of the output shaft 6 is lower than a predetermined reference rotational speed B (rpm) (step S4). This determination may be replaced with a determination regarding the vehicle speed. Essentially, it is a determination as to whether the vehicle is traveling assuming or planning to stop. Therefore, as an example, the reference rotational speed B may be the rotational speed of the output shaft 6 when the vehicle speed is 20 to 30 km / h.

[0027] Furthermore, it is determined whether or not the throttle opening Tap is smaller than a predetermined reference opening C (%) (step S5). This throttle opening Tap does not necessarily have to be an actual value obtained by actually detecting the opening of a throttle valve (not shown) with a sensor, and may be an opening for shift stage determination obtained by subjecting the opening detected by the sensor to some processing or correction. Since the throttle opening Tap is adopted as a determination item for determining an uphill road, the reference opening C may be a value corresponding to the throttle opening degree when the vehicle travels slowly without particularly accelerating on an uphill road with a large gradient among the uphill roads on which the vehicle normally travels.

[0028] Moreover, it is determined whether or not the average value Gav of the longitudinal acceleration during a predetermined time period before the current time is equal to or greater than a determination reference value D (step S6). Since this step S6 determines the magnitude of the longitudinal acceleration as one item for determining an uphill road, the determination reference value D is a small value determined by experiments or the like. Also, since the longitudinal acceleration changes in relation to the throttle opening Tap, the determination reference value D may be a variable that changes in relation to the throttle opening Tap.

[0029] When the results in these four determination steps from step S3 to step S6 are affirmative, the determination that it is an uphill road is established. Note that the order of determination in steps S3 to S6 is not limited to the order shown in FIG. 2, and may be an appropriate order, or the determination may be made simultaneously and in parallel.

[0030] When the determination of the uphill road is established, that is, when it is affirmatively determined in step S6 in the example shown in FIG. 2, the slope correction is reflected in the torque shared by the release clutch (step S7). The embodiment described here is based on the control of upshift and downshift on a normal flat road, and is corrected so as to be suitable for upshift and downshift on an uphill road. Therefore, during upshift and downshift, since the required driving force is generated and the torque applied to the release clutch is greater than that in the case of upshift and downshift on a flat road, the value of the shared torque for obtaining the release pressure, which is the hydraulic pressure for controlling the release of the release clutch, is increased and corrected.

[0031] Since the correction is performed when the conditions of steps S3 to S6 described above are satisfied, the increased correction value can be experimentally obtained and prepared in advance as a map. For example, the longitudinal and lateral accelerations and the shared torque (which can be obtained from the gear ratio and the input torque) are used as variables, and a two-dimensional map is prepared in which the correction torque is determined to have a larger value as the longitudinal and lateral accelerations increase and as the shared torque increases, and the increased correction value can be obtained using this map.

[0032] Also, it is changed to the target shift time during uphill travel (step S8). That is, even in the upshift and downshift on a flat road that is the base, the target shift time is determined in advance, and in particular, the time of the inertia phase is determined, and the release pressure or the engagement pressure, which is the hydraulic pressure of the friction engagement mechanism on the engagement side, is controlled so as to change to the synchronous rotation speed within that time. In step S8, the target shift time with a longer inertia phase time is adopted. If the shift time is short, the change rate of the rotation speed of a predetermined rotating member (more specifically, the input rotation speed) increases, and the possibility of shock generation increases. On the contrary, if the shift time is long, the change rate of the rotation speed of a predetermined rotating member decreases, and shock is less likely to occur, but the shift responsiveness deteriorates.

[0033] Therefore, the target shift time may be experimentally determined in consideration of these shocks and shift responsiveness. For example, the larger the change amount of the input rotation speed (the rotation speed difference before and after shifting), the longer the shift time. During the shift time thus determined, the release pressure is feedback-controlled so that the input rotation speed smoothly changes toward the synchronous rotation speed, which is the rotation speed after shifting. Note that such feedback control of the release pressure is a control known as a control during shifting in the past.

[0034] Then, start the downshift for which the determination in step S1 described above holds (step S9). An example thereof will be described later. If the result in any one of the determination steps from step S3 to step S6 described above is negative, immediately proceed to step S9 to start the downshift. In that case, the shift control is based on the shared torque and target shift time without correcting for the uphill road. That is, it is a conventionally known downshift control.

[0035] An example of the change in the release instruction hydraulic pressure by the downshift control with correction on the uphill road described above and the accompanying changes in the rotational speed and shift progress are schematically shown in FIG. 3. The example shown here is an example of downshifting from the third gear to the first gear in a transmission capable of setting ten forward gears described above. Therefore, the first brake B-1 is the release-side engagement mechanism, and the first clutch C-1 is the engagement-side engagement mechanism. In FIG. 3, the solid line shows the control example of this invention, and the dashed line shows the control example at the time of normal downshift on a flat road or the like.

[0036] When the determination for downshifting to the first gear is made at a predetermined time point t1 while traveling in the third gear, the release instruction hydraulic pressure is temporarily greatly reduced at the time point t2 immediately after that. This is the control of the hydraulic pressure opposite to the so-called first fill at the time of engagement, and is the control for eliminating contact (engagement) due to crimping or elasticity. Then, it returns to an instruction hydraulic pressure slightly lower than the instruction hydraulic pressure at the time of full engagement and gradually decreases at a predetermined gradient. Since the instruction hydraulic pressure returned after being temporarily decreased in this way and the instruction hydraulic pressure decreased thereafter correspond to the shared torque corrected due to the uphill road described above, it becomes an instruction hydraulic pressure higher than the instruction hydraulic pressure in the case of normal downshift on a normal flat road or the like.

[0037] When the torque capacity of the first brake B-1, which is the engagement mechanism on the release side, decreases to a certain extent, slippage begins to occur in the first brake B-1 and the input rotation speed and the like begin to change (at time t3). That is, the inertia phase starts. Since the time until the input rotation speed reaches the synchronous rotation speed, which is the rotation speed after shifting, is set as the target shift time, the change gradient of the input rotation speed is determined from the difference from the synchronous rotation speed and the target shift time. On the other hand, since the input rotation speed or the rotation speed of a predetermined rotating member in the transmission is determined by the release hydraulic pressure of the first brake B-1, which is the engagement mechanism on the release side, that is, the degree of slippage, the release command hydraulic pressure is feedback-controlled so that the input rotation speed changes toward the synchronous rotation speed at a predetermined gradient.

[0038] The inertia phase ends when the input rotation speed synchronizes with the rotation speed after shifting (at time t4). At that time, the release command hydraulic pressure is temporarily maintained, waiting for the complete engagement of the first clutch C-1, which is the engagement mechanism on the engagement side, and then the release command hydraulic pressure is decreased toward release.

[0039] On the other hand, in the case of a normal downshift on a flat road or the like, the shift progress, the rotation speed, and the release command hydraulic pressure change as shown by the chain line in FIG. 3. Therefore, the inertia phase ends at time t31, which is earlier than the above-mentioned time t4. When the control of this invention is performed, the inertia phase ends at time t4, and the inertia phase or the shift time becomes longer than in the case of a normal downshift, but the extension is suppressed by the amount by which the release command hydraulic pressure (release pressure) is increased. Also, when downshifting while climbing a slope with the accelerator pedal slightly depressed, if the engagement command hydraulic pressure is set as the hydraulic pressure of a normal downshift shown by the chain line in FIG. 3, the change in the rotation speed becomes too abrupt and a shift shock occurs or deteriorates.

[0040] Therefore, in the shift control device according to the embodiment of the present invention, in the case of an up-down shift on an uphill road, the time of the inertia phase during which the rotational speed of a rotating member such as the engine rotational speed changes toward the rotational speed after shifting is made longer than the time of the inertia phase in the case of a normal up-down shift on a flat road or the like. In addition to this, the shared torque used for the release pressure control is increased and corrected so that the release pressure is controlled higher than the release pressure in the case of a normal up-down shift on a flat road or the like. Therefore, for example, when the downshift line is set to the low vehicle speed side so that a downshift from the third speed to the first speed is performed at a low vehicle speed, even if such a downshift is performed on an uphill road and in a power-on state, a rotational speed change toward the synchronous rotational speed can be quickly generated, and a shift without shock can be achieved.

[0041] Further, even if the time of the inertia phase is lengthened and the overall shift time becomes longer, since the command value of the release hydraulic pressure is increased along with the increase and correction of the shared torque, an extension of the shift time (the time of the inertia phase) can be suppressed. By setting the downshift line to the low vehicle speed side as described above, the occurrence of a re-acceleration request during a normal up-down shift on a flat road or the like is reduced, and the driver does not feel a deterioration in the responsiveness of re-acceleration, or the frequency thereof becomes low, and a transmission or a vehicle without a sense of discomfort can be achieved.

[0042] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments. The target stepped transmission may have a configuration other than the gear train shown in FIG. 1. Therefore, the number of shift stages that can be set may be 10 or more or less forward gears. Further, the determination of the uphill road in the present invention may use, in addition to or instead of the determination according to steps S3 to S6 described above, the road information of the current position of the host vehicle based on the map information provided in the navigation system.

Explanation of Signs

[0043] 1 Ravigneaux type planetary gear mechanism 2, 3 Single pinion type planetary gear mechanism 4 Input shaft 5 Fixed part 6 Output shaft 7 Electronic control unit (ECU) B-1, B-2 Brake C-1, C-2, C-3, C-4 Clutch C1, C20, C30 Carrier R1, R20, R30 Ring gear S1, S2, S20, S30 Sun gear

Claims

【Claim 1】 A shift control device for a stepped transmission that sets a gear stage by a plurality of engagement mechanisms whose engagement and release are hydraulically controlled, and selects a gear stage to be set based on at least two data of a required driving force and an output rotational speed, when it is determined that an upshift-downshift to switch to a lower-speed gear stage is required under an increase requirement of the required driving force, it is determined whether the vehicle is traveling on an uphill road, when the determination that the vehicle is traveling on an uphill road is established, the command value of the release hydraulic pressure of the engagement mechanism released by the upshift-downshift is set to a command value larger than the command value at the time of an upshift-downshift to switch to the lower-speed gear stage when traveling on a flat road without an increase requirement of the required driving force, and is a command value based on an increase correction value of the torque applied to the engagement mechanism, the target time of the inertia phase of the upshift-downshift is set longer according to the difference in the input rotational speed before and after the upshift-downshift and longer than the time of the inertia phase of the upshift-downshift on the flat road, and the release hydraulic pressure is controlled so that the inertia phase ends at the target time A shift control device for a stepped transmission, characterized in that it is configured as described above.

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