JP2536845B2 - Control method of shift clutch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shift clutch control method applied to a gear type transmission including a plurality of drive side shift clutches and a plurality of load side shift clutches. .

[Conventional technology]

FIG. 9 shows a configuration example of a gear type transmission 1 used in a construction machine such as a dump truck. In this transmission,
Input shaft 2 to which the output of the engine (not shown) is added
Drive-side shift clutches 1A and 1B are provided on the side, and load-side shift clutches 1C and 1D are provided on the output shaft 3 side.

FIG. 10 shows a clutch drive hydraulic pressure supply device applied to the transmission 1. The modulation valve 4 used in this hydraulic pressure supply device has a function of generating a gradually increasing hydraulic pressure by a blunt mechanical mechanism or based on an electric signal from the controller 9, and a pump 5 is connected to its input end. Further, electromagnetic switching valves 6 for selecting the clutches 1A and 1B and electromagnetic switching valves 7 and 8 for selecting the clutches 1C and 1D are connected to the output ends thereof, respectively.

The switching valves 6, 7 and 8 are solenoids S, respectively.
Switching operation is performed by energizing OL1, SOL2 and SOL3. The solenoids SOL1, SOL2 and SOL3 are
When the solenoid 9 is urged by the output signal of the controller 9, for example, as shown in Table 1 below, the clutches 1A and 1C are engaged to select the first speed, and the solenoids SOL1 and SOL2 are activated. Clutch 1B, 1C when energized
Is engaged and the second speed is selected. When the solenoid SOL3 is energized, the clutches 1A and 1D are engaged and the third speed is selected. When the solenoids SOL1 and SOL3 are energized, the clutches 1B and 1D are engaged and the fourth speed is selected. To be selected.

[Problems to be Solved by the Invention] Here, consider a case where the speed stage of the transmission 1 is changed from the third speed to the second speed. When the speed stage is the 3rd speed, as is clear from the above table, only the solenoid SOL3 is energized and the clutch
Since 1A and 1D are in the engaged state, FIG. 11 (a)
As shown in (b) and (b), the prescribed clutch hydraulic pressure acts on these clutches.

In this state, the solenoid at time t ₁ shown in FIG. 11
When SOL3 is deenergized and solenoids SOL1 and SOL2 are energized at the same time, oil in the clutch pack of clutch 1A is drained via valve 6 and oil in the clutch pack of clutch 1D is drained via valve 8. As a result, the hydraulic pressures acting on the clutches 1A and 1D respectively drop as shown in FIGS. 9A and 9B, and the engagement of these clutches is released.

On the other hand, through the valves 6 and 7, each clutch
1B and 1C are connected to the modulation valve 4, which starts the supply of oil to their clutches. At the time point t ₁ , the clutch packs of the clutches 1B and 1C are in a zero state, and therefore, from the time point t ₁ until the clutch packs are filled with oil, that is, the time required for so-called filling (filling time). time)
The hydraulic pressures of these clutches are kept substantially zero during the end of.

As shown in FIGS. 3 (c) and 3 (d), the modulation valve 4 is operated after the filling time is completed.
The increasing hydraulic pressure modulated by the clutch 1B and
1C respectively, which causes their clutches to be engaged. The shift shock is reduced by applying the gradually increasing hydraulic pressure to the clutches 1B and 1C in this manner.

By the way, the drive side shift clutch 1B and the load side shift clutch 1C have different clutch disc relative rotation speeds and disc rotation directions before engagement, and there are variations in the clutch engagement characteristics themselves. In the conventional hydraulic pressure supply device in which the two clutches 1B and 1C are simultaneously engaged by using the modulation valve 4, the clutch 1B is engaged as shown in FIG. 11 (e) as a change in the output shaft torque of the transmission 1. Both of the shift shock A based on the engagement of the clutch 1C and the shift shock B based on the engagement of the clutch 1C appear.

In the conventional device, the above-mentioned problem also occurs when only one clutch is switched.

That is, as is apparent from the above table, when changing the speed stage from the third speed to the fourth speed, for example, the solenoid SOL1 is energized while the energized state of the solenoid SOL3 is maintained. Only the side shifting clutch will be switched from clutch 1A to clutch 1B, but at that time, due to the filling of this clutch 1B, the hydraulic pressure acting on each clutch 1D drops to near zero and the clutch 1D Is disengaged. Therefore, even in the case as described above, as a result, both the clutches 1B and 1D are engaged by the gradually increasing hydraulic pressure supplied from the valve 4.

As described above, in the conventional device, both the drive side shift clutch and the load side shift clutch are engaged even when one clutch is switched.
A shift shock with two peaks occurs.

[Means and Actions for Solving Problems]

According to a first aspect of the present invention, a plurality of power transmission paths are arranged in parallel between an input shaft and an intermediate shaft, and drive-side speed change clutches are respectively interposed between the intermediate shaft and the output shaft. A plurality of power transmission paths, each of which is provided with a load-side shift clutch interposed therebetween, and is provided in one of the drive-side shift clutches and one of the load-side shift clutches. The first and second means are applied to a gear type transmission configured to set a desired speed stage by operating the gradually increasing hydraulic pressure, and as means for generating the gradually increasing hydraulic pressure.
When only the drive-side shift clutch is switched and engaged by using the modulation valve of No. 1, the step of eliminating the hydraulic pressure acting on the engaged drive-side shift clutch, and the drive to be engaged next And a step of causing the hydraulic pressure generated by the first modulation valve to act on the side shift clutch, and when only the load side shift clutch is switch-engaged, the load side shift clutch being engaged And the step of causing the generated hydraulic pressure of the second modulation valve to act on the drive side shift clutch to be engaged next, and the drive side shift clutch. When both the load side shift clutch and the load side shift clutch are switched and engaged, the hydraulic pressures acting on the engaged drive side shift clutch and the load side shift clutch are lost. The step of applying the generated hydraulic pressure of the first modulation valve to the drive-side shift clutch to be engaged next, and the completion of the engagement of the drive-side shift clutch to be engaged next. It is characterized in that the step of detecting and the step of applying the generated hydraulic pressure of the second modulation valve to the load dynamic shift clutch to be engaged next after the completion of the engagement are detected.

The second invention uses a modulation valve individually provided for each of the drive side shift clutches and for each of the load side shift clutches as means for generating the gradually increasing hydraulic pressure. When only the shift clutch is switched and engaged, the step of eliminating the hydraulic pressure acting on the engaged drive shift clutch and the clutch for the drive shift clutch to be engaged next And the step of applying the generated hydraulic pressure of the modulation valve provided corresponding to the above, and when only the load side shift clutch is switched and engaged, it acts on the load side shift clutch being engaged. The step of eliminating the existing hydraulic pressure and the generation of the modulation valve provided corresponding to the load side shift clutch to be engaged next And a step of applying pressure, and when both the drive-side shift clutch and the load-side shift clutch are switch-engaged, they act on the engaged drive-side shift clutch and load-side shift clutch. The step of eliminating the respective hydraulic pressures, the step of applying the generated hydraulic pressure of the modulation valve provided corresponding to the clutch for the drive side shift clutch to be engaged next, and the step of A step of detecting the completion of engagement of the drive-side shift clutch to be engaged, and the step of detecting the completion of engagement of the drive-side shift clutch to be engaged next to the load-moving-side shift clutch to be engaged next. And the step of applying the generated hydraulic pressure of the modulation valve.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an automatic transmission to which the present invention is applied.

In the figure, the output of the engine 10 is the torque converter.
11, transmitted to the drive wheels 13 via the gear type transmission 1 and the final reduction gear 12. A lock-up clutch 14 that directly connects the input and output shafts of the torque converter 11 is interposed, and this clutch operates so as to release the lock-up during gear shifting.

The engine 10 has an engine rotation sensor 15 which outputs a pulse signal of a number corresponding to the number of revolutions thereof, and the transmission 1 has a number of pulses corresponding to the number of revolutions of the input shaft 2, the intermediate shaft 2a and the output shaft 3 thereof. Rotation sensors 16, 17 and 1 that output signals
8 are provided respectively.

The controller 19 is added with the output signals of the sensors 15 to 18, the range command signal output from the shift range command device 20, and the output signal of the throttle amount sensor 21a that works in conjunction with the throttle pedal 21.

The transmission 1 includes two power transmission paths arranged in parallel between the input shaft 2 and the intermediate shaft 2a, and two power transmission paths arranged in parallel between the intermediate shaft 2a and the output shaft 3. It has a route. The drive side shift clutches 1A and 1B are respectively interposed in the former power transmission paths, and the load side shift clutches 1C and 1D are respectively interposed in the latter power transmission paths. The supply hydraulic pressure of each of the clutches 1A to 1D is controlled by a clutch drive hydraulic pressure supply device 22 described later.

FIG. 2 shows the structure of the clutch drive hydraulic pressure supply device 22. In FIG. 2, the same elements as those shown in FIG. 10 are designated by the same reference numerals. This clutch drive hydraulic pressure supply device 22 is provided with two electronically controlled modulation valves 23 and 24, and FIG. 3 exemplifies the configuration of these valves.

As shown in the figure, this modulation valve 23, 24
Is the first piston portion 241, the second piston portion 242, and the third
It has a spool 244 equipped with a piston portion 243, and the left end of this spool 244 is a plunger 246 of a proportional solenoid 245,
The right end of the spool is in contact with each retainer 248 which is biased to the left by a spring 247.

The first piston portion 241 and the second piston portion 242 are the oil chamber 24.
The second piston part 242 and the third piston part 243 define the oil chamber 250. And oil chamber 249 and oil chamber 250
An input port 251 and a tank port 252 are opened in each of them.

The oil chamber 253 in which the spring 247 and the retainer 248 are arranged is
It is in communication with the output port 255 via the passage 254. Further, at the opening end of the output port 255 on the spool 244 side, the second
The piston portion 242 is located, and the open end is closed by the second piston portion 242 in the illustrated state.

The proportional solenoid 245 is provided as an actuator for moving the spool 244, and the plunger 246 is in contact with the left end surface of the spool 244. As is well known, the proportional solenoid 245 has a characteristic that the thrust F of the plunger 246 is proportional to the input current i, and FIG. 4 shows this relationship.

Modulation valves 23, 2 having such a structure
Oil discharged from the pump 5 shown in FIG. 2 is supplied to the 4th input port 251. The discharge pressure of the pump 5 is constant due to the action of the relief valve 30 (for example, 35 kg / cm ² ).
Is held.

Now, when the proportional solenoid 245 is actuated and the spool 244 moves to the right, the oil supplied to the input port 251 flows into the output port 255, and at that time, part of the oil passing through this output port 255 flows through the passage 254. Through the oil chamber 253.

Therefore, assuming that the pressure receiving area of the piston portion 243 in FIG. 3 is A and the hydraulic pressure at the output port 255, that is, the hydraulic pressure in the oil chamber 253 is P _a , the force A · P _a acts in the direction to move the spool 244 to the left, As a result, the spool 244 moves leftward as the hydraulic pressure in the oil chamber 253 rises. Then, when the spool 244 is moved to the left, the inflow of oil to the output port 255 is cut off, and oil is drained from the output port 255 side to the tank port 252 side.

Thus, the spool 244 operates so that the thrust force F of the plunger and the force A · P _a are balanced, that is, the balance relationship shown in the following formula is satisfied.

F = A · P _a (1) The spring 247 acts to urge the spool 244 to the left, but since a spring with a small spring constant is used as the spring 247, in the above description. The action of this spring is ignored.

As described above, the thrust force F of the plunger 246 and the drive current i of the solenoid 245 are F = K · i (2) However, since there is a relationship of K: proportional constant, (1), (2) From the equation, the relationship K · i = A · P _a (3) is obtained, and from this, the hydraulic pressure P _{a of the} output port 255
Is expressed as P _a = K · (i / A) (4) As is clear from the equation (4), the oil pressure P _{a of the} output port is proportional to the drive current i of the solenoid 245, and this relationship is shown in FIG.

FIG. 6 shows the processing procedure of the controller 19, and the operation of this embodiment will be described below with reference to FIG.

In the controller 19, it is determined whether or not gear shifting is performed based on the output signal of the engine rotation sensor 15, the gear shift range command signal output from the gear shift range command device 20, and the output signal of the throttle amount sensor 21a ( Step 100). Since the determination of the shift is publicly known, its explanation is omitted here.

If the determination result in step 100 is YES, it is determined whether or not the shift is such that both the drive-side shift clutch and the load-side shift clutch are switched (step 101).

If the determination result in step 101 is YES, a process of disengaging the currently engaged shift clutch and connecting the drive side shift clutch to be engaged to the modulation valve 23 is executed ( Step 102).

That is, considering the case where the speed stage is changed from the third speed (the clutches 1A and 1D are engaged at this time) to the second speed in the relationship of the above table, in this case, the switching valve 8
The solenoid SOL3 is deenergized and the solenoids SOL1 and SOL2 of the switching valves 6 and 7 are energized.

When the solenoid SOL3 is de-energized, the switching valve 8 becomes the second
Since it is returned to the position shown in the figure, the oil in the clutch 1D is drained through the valve 8. Therefore, FIG. 7 (b)
As shown in, the hydraulic pressure that has been acting on the clutch 1D drops until then, and the engagement is released.

When the solenoid SOL1 is energized, the switching valve 6 is switched from the position shown in FIG. 2 so that the oil in the clutch 1A is drained. As a result, as shown in FIG. 7 (a), the hydraulic pressure acting on the clutch 1A is reduced,
This clutch 1A is disengaged. The clutch 1B is connected to the modulation valve 23 according to the switching operation of the valve 6.

On the other hand, when the solenoid SOL2 is energized, the switching valve 7
, The clutch 1C is connected to the modulation valve 24.

Next, the controller 19 uses the modulation valve 23 to supply the filling oil to the clutches 1B and 1C.
A process for applying a filling command current to each of the clutches 24 and 24 is executed (step 103), whereby the clutch 1B,
1C filling begins. The filling hydraulic pressure based on the command current is set to a low pressure.

In the next step 104, the controller 19 determines whether or not the filling of the drive-side shift clutch 1B to be engaged is completed, and this determination is made, for example, as follows.

That is, since the time when the filling of the clutch 1B ends is predicted, it is possible to determine that the filling ends when the timer is started at the start of the filling and the timer measures the preset time required for the filling.
Also, at the end of filling, the clutch 1B
Since the inflow of oil into the oil substantially stops, a sensor that catches this phenomenon can be arranged in the hydraulic pressure supply path of the clutch to detect the end of the filling.

When it is determined in step 104 that the filling of the drive side shift clutch 1B has been completed, a command current for increasing the clutch hydraulic pressure of the clutch 1B at a large increase rate is generated by the controller.
It is added to the modulation valve 23 from 19 (step
105), which causes the hydraulic pressure of the clutch 1B to be as shown in FIG. 7 (c).
As shown in, the pressure is quickly increased to the set pressure of the relief valve 30.

At this time, since the load side shift clutches 1C and 1D are both in the disengaged state, no shift shock due to the engagement of the clutch 1B occurs at all.

The controller 19 detects the completion of the engagement of the clutch 1B in the next step 106, and the completion of the engagement is performed as follows.

That is, when the engagement of the clutch 1B is completed, the relative rotational speed of the disk of this clutch becomes zero. Therefore, the relative rotation of the disk based on the outputs of the input shaft rotation sensor 16 and the intermediate shaft rotation sensor 17 shown in FIG. The state where the number becomes zero is detected, and the completion of the engagement is judged by this.

When the completion of the engagement of the clutch 1B is determined in step 106, a command current for gradually increasing the clutch hydraulic pressure of the load side shift clutch 1C to be engaged at that time (shown by t ₂ in FIG. 7) is modulated by the controller 19. Added to valve 24. At time t _2, the filling of the clutch 1C is already finished, therefore the oil pressure of the clutch 1C by the command current is gradually increased as shown in Figure No. 7 (d) (step 107), thereby the clutch 1C is engaged Are combined.

Thus, the clutches 1A and 1D that have selected the third speed are disengaged, and the clutches 1B and 1C that select the second speed are engaged instead.

The hydraulic pressure increase patterns shown in FIGS. 7C and 7D, that is, the increase patterns of the command currents applied to the modulation valves 23 and 24 are stored in advance in a memory (not shown) built in the controller 19. There is.

According to the above-described embodiment, since the load side shift clutch is engaged after the drive side shift clutch is engaged, the load side shift clutch is changed as shown in FIG. Only the shift shock B based on the engagement of the vehicle clutch is generated.

The above has described the case where both the drive-side shift clutch and the load-side shift clutch are switched.However, when only one of the clutches is switched next, that is, the determination result in step 101 is NO. A case will be described.

In this case, similarly to the above, the process of lowering the oil pressure of the clutch to be disengaged and connecting the clutch to be engaged to the modulation valve is executed (step 10
8). That is, considering the case where the speed stage is switched from the third speed to the fourth speed, for example, as shown in Table 1, in this case, the clutch 1A of the drive side shift clutch is disengaged and the clutch 1B is released. Will be engaged, so
A process of energizing the solenoid SOL1 to switch the switching valve 6 is executed. This is because the oil in the clutch 1A is drained and the clutch 1B is connected to the modulation valve 23.

Next, the controller 19 executes a process of outputting a filling command current to the modulation valve (step 109). That is, in the above example, the command current for filling is output to the modulation valve 23,
As a result, the clutch 1B is filled.

Then, in the controller 19, whether or not the filling is completed is judged by the means such as the timer described above (step 110), and when the completion of the filling is confirmed, the modulation valve, that is, the modulation valve 23 in the above example, is used for gradually increasing the hydraulic pressure. The process of outputting the command current of is executed (step 111).

When only the shift clutch on the load side is switched, for example, when the speed stage is changed from the 1st speed to the 3rd speed in the relationship of the above Table 1, in order to engage the clutch, the above procedure is applied. The procedure is executed.

FIG. 8 shows another configuration example of the clutch drive hydraulic pressure supply device 22. In this clutch drive hydraulic pressure supply device 22, the drive side shift clutches 1A and 1B and the load side shift clutch 1 are arranged.
Individual modulation valves 25, 26, 27 and 28 are provided for C and 1D, respectively, and the switching valve 6, shown in FIG.
7 and 8 have been omitted.

The above modulation valves 25, 26, 27 and 28 are
It has the same structure and operation as the modulation valves 23 and 24 shown in FIG. 2, and their input ports (reference numeral in FIG. 3).
251) are commonly connected to the pump 5, and their output ports (shown by reference numeral 255 in FIG. 3) are respectively connected to the clutch 1.
Connected to A, 1B, 1C and 1D.

As shown in Table 2 below, among the valves 25 to 28, when the valves 25 and 27 are operated, the clutches 1A and 1C are engaged to select the first speed, and the valves 26 and 27 are operated. The second speed is selected by engaging the clutches 1B and 1C.

When the valves 25 and 28 are operated, the clutch 1A,
1D is engaged to select the third speed, and when the valves 26 and 28 are operated, the clutches 1B and 1D are engaged to select the fourth speed.

The modulation valves 25 to 28 are controlled in a manner according to the procedure shown in FIG.

That is, when both the drive-side shift clutch and the load-side shift clutch are switched, the drive-side shift clutch to be engaged is first activated, and the load-side shift clutch to be engaged after completion of the engagement of this clutch. For clutch is engaged.

In the embodiment shown in FIGS. 2 and 8, as the modulation valves 23, 24, 25 to 28, an electronically controlled pressure control valve that generates a hydraulic pressure proportional to the command current is applied. A valve as shown in Japanese Patent Application No. 60-311098, which generates a hydraulic pressure of a predetermined increasing gradient based on the above, may be applied.

In the embodiment shown in FIG. 2, it is also possible to use blunt mechanical modulation valves as the modulation valves 23 and 24.

〔The invention's effect〕

According to the present invention, when both the drive-side shift clutch and the load-side shift clutch are switched, the load-side shift clutch is engaged after completion of the engagement of the drive-side shift clutch. The shift shock can be reduced as compared with the conventional device in which the gears are simultaneously engaged.

Further, when either one of the drive side shift clutch and the load side shift clutch is switched, the influence of the clutch hydraulic pressure of the clutch to be engaged does not affect the hydraulic pressure of the engaged clutch, that is, Unlike the conventional case, the hydraulic pressure of the engaged clutch is reduced during filling of the clutch to be engaged, and as a result, the state in which those clutches are engaged at the same time does not occur. Is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing one configuration example of an automatic transmission to which the method of the present invention is applied, and FIG. 2 is a configuration of a clutch drive hydraulic pressure supply device and a connection mode between the device and a shift clutch. Fig. 3 is a cross-sectional view illustrating the configuration of a modulation valve, Fig. 4 is a graph showing current-thrust characteristics of a proportional solenoid, and Fig. 5 is solenoid current and output pressure of a pressure control valve. FIG. 6 is a flow chart showing a processing procedure of the controller shown in FIG. 1, and FIG. 7 is a shift clutch when the clutch drive hydraulic pressure supply device shown in FIG. 2 is used. FIG. 8 is a graph exemplifying a change in hydraulic pressure and a change in output torque of the transmission, FIG. 8 is a hydraulic circuit diagram showing an embodiment of the present invention employing a full-step modulation method, and FIG. 9 is a gear type equipped with a shift clutch. Conceptual diagram illustrating one configuration example of a speed machine, the
FIG. 10 is a hydraulic circuit diagram showing a configuration of a conventional clutch drive hydraulic pressure supply device, and FIG. 11 is a hydraulic pressure change of a shift clutch and an output of a transmission when the clutch drive hydraulic pressure supply device shown in FIG. 10 is used. 6 is a graph showing a change in torque. 1 ... Transmission, 1A, 1B ... Drive side shift clutch, 1C, 1D
...... Load side shift clutch, 5 …… Pump, 6,7,8 ……
Electromagnetic switching valve, 10 …… Engine, 15 …… Engine rotation sensor, 16 …… Input shaft rotation sensor, 17 …… Intermediate shaft rotation sensor, 18 …… Output shaft rotation sensor, 19 …… Controller,
20 ... Shift range commander, 21a ... Throttle amount sensor, 22 ... Clutch drive hydraulic pressure supply device, 23-28 ... Modulation valve.

Claims (2)

(57) [Claims] 1. An input shaft and an intermediate shaft are arranged in parallel,
A plurality of power transmission paths each having a drive-side speed change clutch interposed therein; and a plurality of power transmission paths arranged in parallel between the intermediate shaft and the output shaft and each having a load-side speed change clutch interposed. A desired speed stage is set by applying a gradually increasing hydraulic pressure to one of the drive-side shift clutches and one of the load-side shift clutches. It is applied to a gear type transmission, and uses first and second modulation valves as means for generating the gradually increasing hydraulic pressure, and when only the drive side shift clutch is switch-engaged, the drive side being engaged. And a step of causing the hydraulic pressure acting on the shift clutch to disappear, and a step of causing the hydraulic pressure generated by the first modulation valve to act on the drive side shift clutch to be engaged next. If only the load side shift clutch is switched and engaged, the step of eliminating the hydraulic pressure acting on the engaged load side shift clutch, and the drive side shift clutch to be engaged next And applying the generated hydraulic pressure of the second modulation valve to the drive side shift clutch and the load side shift clutch for both switching engagement. And a step of causing the hydraulic pressures acting on the shift clutch and the load side shift clutch to disappear, and a step of applying the generated hydraulic pressure of the first modulation valve to the drive side shift clutch to be engaged next. A step of detecting completion of engagement of the drive-side shift clutch to be engaged next, and a step of detecting the completion of engagement of the drive-side shift clutch to be engaged next with respect to the load-side shift clutch to be engaged next The method of the transmission clutch, which comprises carrying out the step of reacting a hydraulic pressure generated in the second modulation valve. 2. An input shaft and an intermediate shaft are arranged in parallel,
A plurality of power transmission paths each having a drive-side speed change clutch interposed therein; and a plurality of power transmission paths arranged in parallel between the intermediate shaft and the output shaft and each having a load-side speed change clutch interposed. A desired speed stage is set by applying a gradually increasing hydraulic pressure to one of the drive-side shift clutches and one of the load-side shift clutches. A modulation valve that is applied to a gear-type transmission and that is provided individually for each of the drive-side shift clutches and for each of the load-side shift clutches is used as the means for generating the gradually increasing hydraulic pressure. When only the side shift clutch is engaged by switching, the step of eliminating the hydraulic pressure acting on the engaged drive side shift clutch, and the drive side to be engaged next A step of causing generated hydraulic pressure of the modulation valve provided corresponding to the clutch to act on the speed clutch, and when only the load side shift clutch is switched and engaged, Dissipating the hydraulic pressure acting on the load side shift clutch, and applying the generated hydraulic pressure of the modulation valve provided corresponding to the clutch to the load side shift clutch to be engaged next. And when both the drive-side shift clutch and the load-side shift clutch are switched and engaged, the hydraulic pressure acting on the engaged drive-side shift clutch and load-side shift clutch is changed. Each of the steps is made to disappear, and the hydraulic pressure generated by the modulation valve provided corresponding to the clutch for the drive side speed change to be engaged next is generated. And a step of detecting completion of engagement of the drive shift clutch to be engaged next, and a step of detecting the completion of engagement of the drive shift clutch to be engaged with the load dynamic side shift clutch to be engaged next after the completion of engagement is detected. And a step of causing the generated hydraulic pressure of the modulation valve provided correspondingly to act, the control method of the shift clutch.