JP2553332B2 - Automatic shifting method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission method, and more particularly to an automatic transmission method for a vehicle equipped with a transmission having a plurality of transmission clutches for selecting each speed stage.

[Conventional technology]

Generally, a load change becomes large at the time of automatic gear shifting or at the time of starting, so that a torque converter is required to smoothly transmit the output torque of the engine to the traveling system.

On the other hand, recently, a method has been developed in which an electronically controlled actuator is attached to a manual transmission (synchromesh) and a main clutch without using a torque converter to perform automatic shifting.

However, this method cannot be used for construction machines with large running torque, and the torque converter can be abolished by using the hydraulic clutch instead of the synchromesh only for manual transmissions that can maintain a half-clutch state when starting. . Therefore, current automatic transmissions for construction machines are equipped with a torque converter.

[Problems to be solved by the invention]

In any case, the torque converter was indispensable for the automatic transmission of the current construction machinery.

An object of the present invention is to provide an automatic shifting method capable of performing automatic shifting without using a torque converter.

[Means for solving problems]

The present invention uses a transmission having a plurality of speed change clutches for selecting a speed stage, an input shaft of the transmission is directly connected to an output shaft of an engine, and a clutch of a speed change clutch related to a speed stage to be selected. An automatic gear shifting method of controlling pressure for starting and shifting, wherein a build-up ratio of the clutch pressure suitable for them is set based on a vehicle body weight, an engine output torque, and the speed stage to be selected. Including step A and step B for determining whether to start or shift, and at the time of starting, increasing the clutch pressure of the shift clutch related to the speed stage to be selected according to the build-up rate; the speed N _e of the engine, compared with the first low-speed rotation speed N ₁ and second low-speed rotation speed N ₂ (> N _{1), e} <N ₁
When the clutch pressure is zero, N _e ≧ N ₁ and N
Step b in which the clutch pressure is maintained at the current value when _e <N ₂ and the disk relative rotational speed n _r of the shift clutch related to the speed stage to be selected are compared with the preset rotational speed n _1. Then n _r
When ≧ n ₁ , step A and steps a and b are executed again, and when n _r <n ₁ , step c for holding the clutch pressure at the current level and the engine speed N _e First low speed revolution N ₁
In comparison with N _e <N ₁ , the clutch pressure is made zero, and when N _e ≧ N ₁ , the disk relative rotational speed n
_{When r} reaches zero or almost zero, step d which raises the clutch pressure to a prescribed pressure is executed, while at the time of the shift, the clutch pressure of the shift clutch of the other gear is set to zero, and
Step a'in which the clutch pressure of the shift clutch related to the speed stage to be selected is increased according to the build-up rate, and the disk relative rotational speed n _r is compared with the preset rotational speed n ₁ to obtain n. _{a step} of maintaining the clutch pressure at the present value when _r <n ₁ and increasing the clutch pressure to a specified pressure when the disk relative rotation speed n _r reaches zero or almost zero. It is characterized by executing b'and.

[Action]

That is, by electronically controlling the clutch engagement at the time of starting or gear shifting as described above, smooth torque transmission is enabled and the torque converter can be eliminated.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an apparatus to which an automatic shift control method according to the present invention is applied. In the figure, an output torque of an engine 10 is transmitted to a tire 16 via a transmission 12, a final reduction gear, and a differential gear 14. Here, between the output shaft of the engine 10 and the input shaft of the transmission 12, both shafts are directly connected without providing a torque converter, a main clutch, or the like.

The rotation sensors 18 and 20 detect the number of rotations of the input shaft and the output shaft of the transmission 12, respectively.
A T / M input shaft rotation speed signal and a T / M output shaft rotation speed signal indicating these rotation speeds are output to the controller 30.

The throttle amount detector 24 detects the depression amount of the throttle pedal 22, outputs a throttle signal indicating the depression amount to the controller 30, the payload meter 25 detects the loaded weight, and the load signal indicating the weight is transmitted to the controller 30. In addition, the shift selector 28 outputs a position signal indicating the shift position (R, N, D, 2, 1) selected by the shift lever 26 to the controller 30.

The controller 30 determines the speed range to be automatically shifted by the shift position signal input from the shift selector 28, and based on the T / M input shaft speed signal and the throttle signal input from the rotation sensor 18 and the throttle amount detection 24, A transmission (12) is controlled via a clutch hydraulic pressure supply device (32) so as to enter an optimum speed stage in a speed range in which automatic gear shifting is possible. The details of this control will be described later.

By the way, the determination of the speed stage at the time of starting is determined as the starting speed stage in the lowermost stage of the speed stage range in which the automatic shift can be selected by the shift selector 28, and the determination of the optimum speed stage during traveling is, for example, as follows. Like this.

Now, when the shift position D is selected by the shift lever 26, if automatic conversion is possible in the speed range from the first forward speed to the third forward speed, it is possible to shift up or down the speed range in this speed range during traveling. The shift down is performed in the pattern shown in FIG. 2 according to the T / M input shaft speed and the throttle signal. That is, when the throttle signal is S ₂ (see FIG. 3), when the T / M input shaft rotation speed becomes R ₄ or more, the gear shifts up by one step, and when it becomes r ₂ or less, it shifts down by one step.

The transmission 12 has, for example, four speed change clutches (hot hydraulic clutches), and a clutch hydraulic pressure supply device.
The hydraulic signal from 32 selectively engages an appropriate clutch corresponding to the speed stage of the clutch, thereby shifting the gear to a desired speed stage.

The details of the clutch hydraulic pressure supply device 32 will be described below.
This will be described with reference to the drawings.

This clutch hydraulic pressure supply device 32 includes different electronically controlled pressure control valves 33a, 33b, 33c, 33d and a pump 34 for applying hydraulic pressure to the clutch pressure generating portions 13a, 13b, 13c, 13d of the four shift clutches. , A relief valve 35 and the like, and means for supplying a predetermined hydraulic pressure to each of the pressure control valves.

FIG. 6 shows a configuration example of the pressure control valves 33a to 33d. This pressure control valve is a spool having a first piston portion 301, a second piston portion 302 and a third piston portion 303.
It has a 304, and the left end of this spool 304 is a proportional solenoid 30.
5 to the plunger 306, and the right end of the spool is a spring 307.
Are respectively abutted against the retainers 308 biased to the left.

The first piston part 301 and the second piston part 302 are
9, the second piston portion 302 and the third piston portion 303 define an oil chamber 310. And oil chamber 309 and oil chamber 310
, An input port 311 and a tank port 312 are respectively opened.

The oil chamber 313 in which the spring 307 and the retainer 308 are disposed,
It communicates with the output port 315 through the passage 314. The second end of the output port 315 on the spool 304 side is
The piston 302 is located, and the opening end is closed by the second piston 302 in the state shown in the figure.

The proportional solenoid 305 is provided as an actuator for moving the spool 304, and the plunger 306 is in contact with the left end surface of the spool 304. As is well known, this proportional solenoid has a characteristic that the thrust F of the plunger 306 is proportional to the input current i.

The oil discharged from the pump 34 is supplied to the input ports 311 of the hydraulic control valves 33a to 33d having such a structure as shown in FIG. The oil pressure of this oil is
It is kept constant (for example, 35 kg / cm ² ) by the action of 35.

Now, when the proportional solenoid 305 is operated and the spool 304 moves to the right, the oil supplied to the input port 311 flows into the output port 315, and at this time, a part of the oil passing through the output port 315 passes through the passage 314. And flows into the oil chamber 313.

Therefore, assuming that the pressure receiving area of the third piston portion 303 is A and the hydraulic pressure at the output port 315, that is, the hydraulic pressure in the oil chamber 313 is P _a , the force A · P _a acts in the direction to move the spool 304 to the left, As a result, the spool 304 moves leftward as the hydraulic pressure in the oil chamber 313 rises. Then, when the spool 304 is moved to the left, the inflow of oil to the output port 315 is cut off, and oil is drained from the output port 315 side to the tank port 312 side.

Thus, the spool 304 operates so that the thrust 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) Although the spring 307 acts to urge the spool 304 to the left, a spring having a small spring constant is used as the spring 307 in the above description. Ignoring the action of the spring.

As described above, the thrust F of the plunger 306 and the drive current i of the solenoid are F = K · i (2) However, there is a relationship of K; proportional constant, and therefore, equations (1) and (2) are used. Then, the relationship K · i = A · P _a (3) is obtained, and from this, the hydraulic pressure P _{a of the} output port 315 is obtained.
Is expressed as P _a = K · (i / A) (4). As is clear from the equation (4), the hydraulic pressure Pa of the output port is proportional to the drive current i of the solenoid, and this relationship is shown in FIG.

Therefore, the controller 30 outputs the drive current i to the pressure control valve of the shift clutch corresponding to the speed stage to control the clutch pressure to shift to the desired speed stage. Is not used, the following special clutch engagement control is performed.

7 and 8 are flowcharts showing an example of the operation of the controller 30 at the time of starting or shifting.

First, the controller 30 receives the T / M from the rotation sensors 18 and 20, the throttle amount detector 24, and the shift selector 28, respectively.
Input the input shaft speed signal, T / M output shaft speed signal, throttle signal and position signal (step 100),
From these input signals, the timing at which the start or the above-mentioned shift is disclosed and the speed stage at which the shift is to be performed are determined (step 101). The start is judged when the T / M output shaft rotation speed (this rotation speed corresponds to the vehicle speed) is zero and the shift lever 26 is placed in a position other than neutral.

Then, when starting or shifting, the vehicle body weight is detected based on the load signal from the payload meter 25 (step 102), and the engine output torque is obtained from the throttle amount (step 103). , The buildup rate of the hydraulic pressure supplied to the clutch at the speed stage to be changed is read from the ROM based on the engine output torque and the speed stage to be changed (step 10).
Four).

Here, the hydraulic build-up rate is the rate of change over time of the hydraulic pressure P and is defined by dp / dt. On the other hand, when a vehicle body shift shock or the like occurs, the jerk value J
(= Dα / dt), the jerk value J and the time change rate (dT / dt) of the transmission torque T to the traveling system are in a proportional relationship. Further, the torque change rate and the buildup rate are , As long as the friction coefficient of the clutch is constant, there is a proportional relationship.

That is, jerk value J and build-up rate (dp / dt)
And is Is represented by However, K is a conversion coefficient, and G is a speed step coefficient, which is different for each speed step (reduction ratio, number of clutches, etc.). Further, I is the total inertial mass, which is obtained by converting the vehicle body weight and the inertia of each part into the output shaft inertial.

Therefore, in order to reduce the shift shock of the vehicle body, it can be achieved by increasing the jerk value to a certain constant value, that is, increasing the clutch pressure at an appropriate buildup rate. Reducing this shift shock leads to smooth transmission of the engine output torque to the traveling system.

Further, when the output torque of the engine is large, the engine stall can be avoided even if the buildup rate is large. Therefore, in the present invention, when determining the desired buildup rate, the gear shift related to the speed stage coefficient G should be performed. In addition to the vehicle body weight related to the speed stage and the total inertial mass I, the engine output torque is also used as a parameter. The controller 30
The optimum buildup rate according to the above three parameters is obtained in advance by simulation or the like, and this is input to the ROM. The buildup rate may be calculated each time from the above three parameters.

Next, in step 105, it is determined whether or not the vehicle is starting, and when the vehicle is starting, the processing proceeds to step 106, and when the vehicle is shifting, the processing shown in FIG. 8 is performed.

In step 106, an electric command that gradually increases from the electric command value indicating zero hydraulic pressure is output so that the clutch pressure at the speed stage to be shifted (started) becomes the hydraulic pressure buildup rate obtained in step 104.

Then, it is determined whether the engine speed (= T / M input shaft speed) Ne is equal to or higher than a certain low speed N ₁ (for example, idle speed), and when Ne ≧ N ₁ , the process proceeds to step 108.
When Ne <N ₁ , the electric command is set to zero the clutch pressure to prevent engine stalling (step 109), and then the process returns to step 100 (step 107). In step 108, it is again determined whether or not the engine speed Ne is a low speed certain speed N ₂ (> N ₁ ) or more. When Ne ≧ N ₂ , the process proceeds to step 111, and when Ne <N ₂ , the electric command is issued. To the current command value,
That is, after setting the hydraulic buildup rate to zero (step
110) and proceeds to step 111. The reason why the hydraulic buildup rate is set to zero in step 110 is to prevent the engine speed from decreasing, that is, the engine stall.

In step 111, the clutch disk relative rotational speed nr is calculated from the T / M input shaft rotational speed, the T / M output shaft rotational speed, and the speed reduction ratio at the speed stage to be changed. Here, the relationship between the clutch disk relative rotational speed nr and the clutch friction coefficient μ is
It becomes as shown in the graph of the figure. That is, the relative speed nr
When the rotational speed is n ₁ or more, the clutch friction coefficient μ is substantially constant, but when the rotational speed is n ₁ or less, it gradually increases.

In step 112, the clutch disk relative rotation speed nr is compared with the rotation speed n _1, and when nr ≧ n ₁ , step
Return to 103. Since the throttle amount changes from moment to moment when starting, it is necessary to set the build-up rate corresponding to this change. For example, if the build-up rate is initially set low and then the throttle amount is increased, set the build-up rate higher than the initial build-up rate,
It is necessary to prevent the engagement delay of the clutch.

The determination result of n _r ≧ n ₁ in step 112 suggests that the engagement of the clutch may be delayed, but in this embodiment, the procedure returns to step 103 when n _r ≧ n _1. Then, the built-up rate is set again, so that the built-up rate corresponding to the change in the throttle amount can be set to realize the quick engagement of the clutch. On the other hand, when nr <n ₁ , the clutch friction coefficient increases, so that the electric command is held at the current command value and the hydraulic pressure build-up rate is set to zero as in step 110 (step 110).
113).

Subsequently, similarly to step 107, it is determined whether or not the engine speed Ne is the number of revolutions N ₁ or more. When Ne ≧ N ₁ , the process proceeds to step 115, and when Ne <N ₁ , the process proceeds to step 109 to prevent engine stall. Return to the beginning through (step 114). In step 115, the clutch disk relative rotational speed nr is calculated in the same manner as in step 111, and when it is confirmed that this relative rotational speed nr has become zero (step 116), an electric command is issued to prevent the clutch from easily disengaging. Is increased to the command value for generating the clutch pressure of the specified pressure (step 117).

Next, a case will be described in which it is determined in step 105 that the shift is in progress.

In this case, an electric command is output to reduce the clutch pressure of the other currently connected speed stage from the specified pressure to the necessary minimum pressure at which the clutch does not disengage (step 120). At the same time, an electric command for supplying pressure oil to the clutch of the speed stage to be changed is output (step 121). The purpose of this step is to fill the clutch pack of the clutch to be shifted with hydraulic oil, so that the electric command corresponds to a clutch pressure close to zero.

Then, when it is confirmed that the time (filling time) required to fill the clutch pack with hydraulic oil has ended (step 122), the clutch pressure at the speed stage to be changed is the hydraulic build obtained in step 104. While outputting an electric command that gradually increases from the electric command value so that the up ratio is obtained (step 123), the electric command for the other-stage clutch lowered to the required minimum pressure is a command corresponding to zero clutch pressure. The value is set (step 124).

Next, the clutch disk relative rotational speed nr is calculated, and the clutch pressure is increased at the hydraulic buildup rate until the relative rotational speed nr becomes nr <n ₁ (steps 125, 12).
6). It should be noted that the hydraulic build-up rate was calculated every moment when the vehicle started, but it is not necessary for shifting during running, and the hydraulic build-up rate is calculated only once.

When the clutch disk relative speed nr becomes nr <n ₁ ,
The electric command is held at the current command value and the hydraulic pressure buildup rate is set to zero (step 127). Meanwhile, in step 128, the clutch disk relative rotation speed nr is calculated, and this relative rotation speed is calculated.
When it is confirmed that nr has become zero (step 129),
Proceeding to step 117 (FIG. 7), the electric command is increased to the command value for generating the clutch pressure of the specified pressure.

In the present embodiment, the hydraulic pressure build-up rate is obtained only once during the shift during traveling, but it may be obtained momentarily as in the case of starting. When the engine speed drops below a certain value when starting,
Although the clutch pressure is set to zero in order to prevent stalling, the clutch pressure may be controlled so as to maintain the half-clutch state.

In addition, when shifting during running, the clutch pressure of the gear that should be shifted after the filling time is increased and the clutch pressure of the speed that was connected to that time is made zero, so that torque can be transmitted at all times. However, the present invention is not limited to this, and also includes a mode in which after the clutch pressure is reduced to zero, pressure oil is supplied to the clutch at the speed stage to be changed.

〔The invention's effect〕

When the torque converter is not used, engine stall may occur due to engagement of the shift clutch at the time of starting, but in the present invention, control of the clutch pressure corresponding to the engine speed N _e is executed. Therefore, stalling can be prevented.

That is, since the clutch pressure is set to zero when the engine speed N _e is N _e <N ₁ , if the engine speed N ₁ is set to, for example, an idle speed (for example, 800 rpm), the engine speed N It is possible to avoid a situation where the engine stalls due to the _e lowering than the idling speed.

Further, when N _e ≧ N ₁ and N _e <N ₂ , the clutch pressure is kept at the present value, so that N ₂ is set to be slightly higher than the idle speed (for example, 1000 rpm). If this is done, it is possible to prevent the engine stall by holding the current clutch pressure to the extent that engine stall does not occur.

On the other hand, since the throttle amount changes every moment when the vehicle starts moving, it is necessary to set the build-up rate of the clutch pressure corresponding to this change. That is, for example, if the initial build-up rate is set low and then the throttle amount is increased, a higher build-up rate than the initial build-up rate should be set to promptly engage the clutch. .

In the present invention, the disc relative rotational speed n _r of the shift clutch relating to the speed stage to be selected is compared with the preset rotational speed n _1, and the built-up rate is reset when n _r ≧ n _1. Therefore, if the preset rotational speed n ₁ is set to, for example, the rotational speed at which the friction coefficient of the speed change clutch starts to increase, a built-up rate corresponding to a change in the throttle amount is set to quickly change the clutch. Engagement can be achieved.

Since the present invention does not use the torque converter, the effect of improving the power transmission efficiency and reducing fuel consumption can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a device to which the method of the present invention is applied, FIGS. 2 and 3 are diagrams used to explain the timing of automatic shifting, and FIG. 4 is a clutch shown in FIG. FIG. 5 is a hydraulic circuit diagram showing details of a hydraulic supply device, FIG. 5 is a graph showing a relationship between a control current and an output pressure of the pressure control valve shown in FIG. 4,
6 is a sectional view showing the details of the pressure control valve shown in FIG. 4, FIGS. 7 and 8 are flow charts used for explaining the operation of the controller shown in FIG. 1, and FIG. 9 is 5 is a graph showing the relationship between the clutch disc relative rotation speed and the clutch friction coefficient. 10 …… Engine, 12 …… Transmission, 18,20…
… Rotation sensor, 22 …… Throttle pedal, 25 …… Payload meter, 26 …… Shift lever, 30 …… Controller, 32 …… Clutch hydraulic pressure supply device, 33a-33d …… Pressure control valve.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area F16H 59:52

Claims (1)

(57) [Claims] 1. A transmission having a plurality of shifting clutches for selecting a speed stage, wherein an input shaft of the transmission is directly connected to an output shaft of an engine, and a shifting clutch related to a speed stage to be selected is used. An automatic shifting method for controlling the clutch pressure to start and shift, and sets a build-up ratio of the clutch pressure suitable for them based on the vehicle body weight, the engine output torque, and the speed stage to be selected. And a step B of determining whether the vehicle is starting or shifting, wherein at the time of starting, the clutch pressure of the shifting clutch related to the speed stage to be selected is increased according to the buildup rate. , the rotational speed N _e of the engine, compared with the first low-speed rotation speed N ₁ and second low-speed rotation speed N ₂ (> N ₁₎ N _e <zero the clutch pressure at the time of N _1, also N _e ≧ N ₁ a and N _e
Step b, in which the clutch pressure is maintained at the current value when <N ₂ , and the disk relative rotational speed n _r of the shift clutch related to the speed stage to be selected are compared with the preset rotational speed n _1. , N _r ≧
When n ₁ is satisfied, step A and steps a and b are executed again, and when n _r <n ₁ , step c is performed to maintain the clutch pressure at the current level, and the engine speed N _{e is set} to the first value. When the clutch pressure is zero when N _e <N ₁ , and when the disk relative speed n _r is zero or almost zero when N _e ≧ N ₁ , as compared with the low speed rotation speed N _{1 of 1.} And step d for increasing the clutch pressure to the specified pressure are performed, while the clutch pressure of the shift clutch of the other gear is set to zero during the gear shift, and the gear shift clutch related to the speed stage to be selected. a step a 'to the clutch pressure is increased in accordance with the build-up rate, the disc relative rotational speed n _r as compared with the preset rotational speed n _1, the clutch pressure as they become n _r <n ₁ Together is held to the magnitude of the current, automatic transmission, characterized in that said disc relative rotational speed n _r is to be executed zero or a step b 'of raising the clutch pressure upon reaching approximately zero to a specified pressure Method.