JP3344491B2 - Automatic transmission control device for wheel loader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic speed change control device for a wheel loader, which can smoothly perform a speed change process during a wheel loader operation.

[0002]

2. Description of the Related Art Conventionally, as an automatic transmission control device of a wheel loader, a method of detecting a rotation speed of an output shaft portion of a transmission and switching a speed stage on the basis of a vehicle speed, and correcting the speed ratio based on a rotation speed of a prime mover and the like. In addition, a type in which a speed stage is switched has been used.

[0003]

One of the typical operations of the wheel loader is V-shape loading as shown in FIG. This operation is performed when the wheel loader 30 loads the earth and sand 31 and the like onto the truck 32 by the arrow I.
(Running), II (excavation), III (transport), IV (loading), V
(Running) is performed continuously. When a conventional wheel loader equipped with an automatic transmission control device is used for such an operation, the following problems occur.

(1) In order to frequently switch between forward and backward traveling of a vehicle, and to shorten the cycle time during work,
In general, a forward / reverse switching operation is performed from a running state by using a vehicle inertia absorbing action at the time of forward / reverse switching by a fluid coupling such as a torque converter. Therefore, for example, when the forward / reverse switching operation is performed during traveling at the third speed, the vehicle speed sharply decreases and shifts down from the third speed to the second speed to the first speed within a short time,
1st gear → 2nd gear → according to the change of direction and acceleration
The shift up is performed to the third speed, but the connection and disconnection of the hydraulic clutch is performed every time the gear is shifted, and each time the torque is lost and the torque rises repeatedly, the riding comfort is poor.

(2) In the IV (loading) operation in FIG.
As shown in (5), the vehicle 34 is moved forward while approaching the target position while raising the boom 33, and the vehicle 34 is stopped at a predetermined position to discharge the cargo 36 in the bucket 35 to the truck 32. In order to stop the vehicle 34 at the correct position, the operator closes the prime mover throttle by returning the accelerator pedal when approaching the position for discharging the load 36 to reduce the vehicle speed. Thus, for example, a situation occurs in which a downshift is performed from the second speed to the first speed. At this time, the wheel loader 30 raises the boom 33 in a state where the load 36 is fully loaded in the bucket 35, and the center of gravity of the entire wheel loader 30 moves upward and becomes unstable. May cause the vehicle 34 to lean forward and spill, or the vehicle 34 may fall down depending on the condition of the road surface.

The present invention solves such a problem in a wheel loader, and improves the riding comfort by preventing the torque from being repeatedly disconnected and disconnected due to the connection and disconnection of the hydraulic pressure clutch when switching between forward and reverse. In addition, an object of the present invention is to provide an automatic transmission control device for a wheel loader that suppresses a braking effect at the time of downshifting during loading operation and improves vehicle stability.

[0007]

SUMMARY OF THE INVENTION An automatic transmission control device according to the present invention detects a transmission that switches to a plurality of speed stages by connecting and disconnecting a hydraulic clutch, and a rotational speed of an output shaft of the transmission. A transmission output shaft rotation speed detector and a solenoid valve controlled to open and close based on a detection value of the transmission output shaft rotation speed detector to disconnect and connect the hydraulic clutch, thereby preliminarily determining the running performance of the vehicle. A forward / backward switching lever that outputs a forward / backward switching signal for the vehicle, and a boom that exceeds a holding height. Boom position detector, and a forward / backward switching signal by a forward / reverse switching lever during running of the vehicle , or forward running of the vehicle.
The above object is attained by providing control means for holding the transmission at a set speed stage for a predetermined time based on a holding height excess detection signal from a boom position detector in a row .

[0008]

When the vehicle is switched between forward and reverse while the vehicle is traveling, the control means controls the transmission based on the forward / backward switching signal output from the forward / backward switching lever to set the transmission to a set speed stage with good acceleration and small braking action. When the vehicle is accelerated to a speed that automatically shifts up to this set speed stage, the hold of the set speed stage is released. Repetition is prevented and riding comfort is improved.

When the boom exceeds the holding height determined in consideration of the stability of the vehicle while the vehicle is traveling forward in the loading operation, the control means controls the boom position detector based on a holding height excess detection signal from the boom position detector. To shift the vehicle to reverse, or to release the set speed stage when the boom drops below the holding height. Thus, the braking action is suppressed, and the stability of the vehicle is improved.

[0010]

FIG. 1 is a block diagram showing the configuration of a control section of an automatic transmission control apparatus according to one embodiment of the present invention, and FIG. 2 is an explanatory view showing the arrangement on a wheel loader. Here, the controller 2 supplied with power from the vehicle-mounted battery 1
NPUT-I / F21, CPU22, ROM23, RA
M24, OUTPUT-I / F 25, and the controller 2 is provided with the rotation speed information detected by the transmission output shaft rotation speed detector 3 provided in the transmission output shaft rotation detector 11, and the motor rotation detection. The rotation speed information detected by the motor rotation speed detector 4 provided in the section 12 is input, and a forward / reverse switching signal of the vehicle 34 is input from the forward / reverse switching lever 5 by an operator's operation. From the boom position detector 6 provided at the end, when the boom exceeds the holding height, a holding height excess detection signal is input. From the controller 2, a first speed solenoid valve 7, a second speed solenoid valve 8, 3 for operating the connection and disconnection of a hydraulic clutch (not shown) of the transmission to switch the speed stage.
Control signals are sent to the quick-closing solenoid valve 9 and the fourth-speed closing solenoid valve 10. These input and output information
The data is written in the RAM 24 and is sequentially updated according to a change in the situation.

FIG. 3 shows a state in which the wheel loader shifts up.
FIG. 4 is a graph showing an example of the shifting performance of the wheel loader when downshifting. During operation, the controller 2 normally includes the input transmission output shaft rotation speed detector 3
From the rotational speed information from the motor, the rotational speed information from the prime mover rotational speed detector 4, the operation position information such as forward, neutral, and reverse from the forward / reverse switching lever, and speed stage selection area data stored in the ROM 23 in advance. The speed stages to be entered are selected, such as upshifting, downshifting, and maintaining the current speed stage. For example, in FIG. 3, when the vehicle speed V1 → 2 on the boundary between the speed range selection regions where the vehicle shifts up from the first speed to the second speed, the first speed setting solenoid valve 7 is turned on.
The control signal is output so that the second-speed setting solenoid valve 8 is turned ON by setting it to FF. In FIG. 4, the vehicle moves from the second speed to the first speed.
When the vehicle speed V2 → 1 on the boundary between the speed gear selection regions for downshifting to the high speed is reached, a control signal is issued so that the second speed setting solenoid valve 8 is turned off and the first speed setting solenoid valve 7 is turned on. Output.

The controller 2 of this embodiment further performs the following control. When the vehicle is switched between forward and reverse while the vehicle 34 is traveling, regardless of the speed stage selected at that time, the second or third speed with good acceleration and a small braking action is set for forward and backward switching. Speed stage selection area when the vehicle 34 accelerates and shifts up from the adjacent low speed stage to the set speed stage by automatic shifting after the vehicle 34 is switched in the traveling direction, When the speed reaches, the holding of the speed stage is released. Since the vehicle 34 is not always accelerated after the forward / backward switching, if a predetermined time elapses after the forward / backward switching, the speed stage can be automatically shifted to the set speed stage even if the speed stage selection region is not reached. Release the hold.

FIG. 5 is a flow chart showing an example of control when switching between forward and reverse. Here, the speed gear holding flag is a data area in the RAM 24 for displaying whether or not the gear is in the gear holding state, and indicates ON (speed gear holding) or OFF (speed gear holding release) by rewriting the data. The timer increments the data every predetermined time Tr on the program to indicate the elapsed time, and is reset by rewriting the data to zero. The time Tr set in the timer depends on the vehicle performance, but is usually about 5 seconds. The hold release speed Vr is the vehicle speed on the boundary between the adjacent low speed stage and the preset speed stage in the speed stage selection area at the time of upshifting.

When the operator operates the forward / reverse switching lever 5 to switch between forward and backward, the controller 2
It is confirmed whether or not the vehicle 2 is traveling based on the rotation speed information from the transmission output shaft rotation speed detector 3. If the vehicle is stopped, the process proceeds to the normal automatic shift control, and the first speed is input from the OUTPUT-I / F 25. Send a control signal. If the vehicle is traveling, the speed stage holding flag is turned on, a display for entering the speed stage holding state is displayed, and the data of the timer for knowing the lapse of time after the forward / reverse switching is reset to zero. Subsequently, it is determined whether or not the vehicle 34 is decelerating by comparing the current vehicle speed data with the vehicle speed data before a predetermined time. To end.

At the time of program execution after the next cycle,
Since the speed stage holding flag is ON, it is repeatedly checked whether or not the vehicle has entered the deceleration state. Once in the deceleration state, turn on the deceleration flag that indicates that the vehicle has once decelerated
Then, it is checked whether the traveling direction has been switched and the vehicle has shifted to the speed increasing state. Thereafter, since the deceleration flag is ON, it is repeatedly checked whether or not the vehicle speed V has reached the holding release speed Vr, and after the vehicle speed V reaches the holding release speed Vr, or after switching between forward and backward, the timer Setting time Tr
Has elapsed, the speed stage holding flag and the deceleration flag are set to O.
The speed stage holding state is released as FF, and the process proceeds to normal automatic shift control.

As described above, when the controller 2 is accelerated to the speed at which the vehicle 34 automatically shifts up to the set speed stage based on the forward / reverse switching signal output from the forward / reverse switching lever 5, In order to cancel the holding of the set speed stage, a smooth shift change is performed, and a torque loss due to the connection / disconnection of the hydraulic clutch and a repetition of the rise of the torque are prevented, so that the riding comfort is improved.

If the boom 33 exceeds the holding height determined in consideration of the stability of the vehicle 34 during the forward running of the vehicle 34 in the loading operation, the boom position detector 6 detects the excess holding height. Based on the signal, the vehicle is put into the second speed generally used during the loading operation or the set speed stage of the current speed stage appropriate for the loading operation being loaded at that time, and is held for a predetermined time to advance the vehicle 34. Is switched to reverse, or when the boom 33 falls below the holding height, the holding of the set speed stage is canceled. In order to prevent a so-called hunting phenomenon from occurring when the boom 33 moves up and down near the holding height, in order to cancel the holding of the set speed stage, the boom 33 needs to be at or below the holding height for a predetermined time. . Usually this time is between 0.5 seconds and 1
Seconds are sufficient. The holding of the set speed stage when the traveling of the vehicle 34 is switched to reverse is released because the vehicle 34 returns to a stable state by discharging the load.

FIG. 6 is a flowchart showing an example of control when the boom 33 exceeds the holding height. Here, the boom raising flag is a data area in the RAM 24 that indicates whether or not the boom 33 is at a position where the holding height has been exceeded, and is turned ON (over the holding height) by rewriting the data, or OFF (not exceeding the holding height). The timer increments the data every predetermined time Tb on the program to indicate the elapsed time, and is reset by rewriting the data to 0.

If the boom 33 rises beyond the holding height during the forward running of the vehicle 34 in the loading operation, the boom lift flag is turned on and a display for entering the set speed stage is displayed, and hunting is prevented. The data of the timer for setting the predetermined time is reset to 0, and the timer is set to the current speed stage or the second speed stage, and the current program cycle is completed. The same flow is repeated when the program is executed in the next cycle and thereafter, and the traveling direction of the vehicle 34 is switched from forward to reverse, or the boom 33 falls below the holding height and this state continues for a predetermined time Tb. Then, the boom raising flag is turned off, and the process proceeds to the normal automatic shift control.

[0020]

As described above, the automatic shift control device for a wheel loader according to the present invention improves the stability of the vehicle by preventing spillage and overturning caused by downshifting during loading operation, and improving the stability of the vehicle. Even when the vehicle is switched between forward and reverse, automatic speed change control with little torque fluctuation and good riding comfort can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a control unit of an automatic transmission control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of an automatic transmission control device on a wheel loader.

FIG. 3 is a graph showing an example of a shift performance of a wheel loader when shifting up.

FIG. 4 is a graph showing an example of a shift performance of a wheel loader at the time of downshifting.

FIG. 5 is a flowchart illustrating an example of control when switching between forward and reverse.

FIG. 6 is a flowchart illustrating an example of control when the boom exceeds a holding height.

FIG. 7 is an explanatory diagram of V-shape loading.

FIG. 8 is an explanatory diagram of an operation of loading the vehicle by raising the boom and moving the vehicle forward.

[Explanation of symbols]

 2 Controller 3 Transmission output shaft rotation speed detector 5 Forward / reverse switching lever 6 Boom position detector 7 1st speed solenoid valve 8 2nd speed solenoid valve 9 3rd speed solenoid valve 10 4th speed solenoid valve 30 wheel loader 33 boom 34 vehicle

Claims (1)

(57) [Claims] A transmission that switches to a plurality of speed stages by connecting and disconnecting a hydraulic clutch, a transmission output shaft rotation speed detector that detects a rotation speed of an output shaft of the transmission, The solenoid valve is controlled to open and close based on the detection value of the engine output shaft rotation speed detector to disconnect and connect the hydraulic clutch, so that the transmission of the transmission can be shifted in accordance with a speed gear selection region predetermined according to the running performance of the vehicle. A forward / backward switching lever that outputs a forward / backward switching signal of the vehicle, a boom position detector that detects that the boom has exceeded a holding height , of <br/> forward-reverse switching signal according to the forward-reverse switching lever, or the vehicle travels forward
An automatic transmission control device for a wheel loader, further comprising control means for maintaining the transmission at a set speed stage for a predetermined time based on a detection signal of an excessive holding height detected by a traveling boom position detector.