JPH11257488A - Continuously variable transmission for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax the generation of a shock during a stop when a sudden stop from a high speed state is effected and reliably stop rotation of an output shaft during a neutral state, in an HST for a working vehicle to mechanically intercouple an HST operation lever and a hydraulic pump moving swash plate. SOLUTION: A continuously variable transmission comprises an HST operation lever 7 being a set means; a moving swash plate 2a being a varying means mechanically coupled thereto; and a correction control means for forcedly controlling the moving swash plate 2a, such as a motor 6 for controlling a moving swash plate. When the HST operation lever 7 is forced into a sudden stop or sudden acceleration deceleration operation, a moving swash plate 2a is forcibly slowly moved by a correction control means from a position right followed by a purpose neutral position or a neutral vicinity position. When neutrality of the HST operation lever 7 is set, the number of revolutions and the rotation direction of the HST output shaft 2b are read, the moving swash plate 2a is moved by a correction control means such that an output shaft is rotated in the reverse direction to the rotation direction and rotation is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuously variable transmission mounted on an agricultural work vehicle or the like, and more particularly to a hydraulic continuously variable transmission that reduces shocks at the time of a sudden stop from a high speed state. In addition, the present invention relates to a configuration for surely stopping the vehicle when in neutral.

[0002]

2. Description of the Related Art Conventionally, in a hydraulic continuously variable transmission (hereinafter referred to as HST) mounted on an agricultural work vehicle or the like, setting means (shift lever) for setting a traveling direction, a shift position or a shift amount, and a traveling direction. A control device connected to a change means (a movable swash plate of an HST hydraulic pump) for changing a gear ratio or a rotation speed of an output shaft is known as disclosed in, for example, JP-A-5-168339.

[0003]

When the setting means and the changing means are connected as described above, the changing means is not required when the vehicle speed is increased or decelerated, particularly when the vehicle is suddenly decelerated or suddenly stopped on a road. The movement is suddenly performed in synchronism with the setting means, so that the shock is large. The operator operates the setting means with the other hand while operating the handle with one hand, and supports the body with one hand against this shock, so the burden is large, fatigue increases, and as a result, It also affects the work accuracy and the like.

Therefore, it is conceivable to forcibly slow down the movement of the change means in spite of the rapid operation of the setting means.
A rapid operation of the setting means for the purpose of a sudden stop becomes meaningless, and a sudden stop is particularly high when traveling on a high-speed road, so that a gentle stop is rather dangerous. Further, even when the vehicle is traveling at low speed (low idling state), such control is not necessary.

[0005] Another problem is that when the setting means and the changing means are connected by a mechanical link mechanism, the neutral area of the changing means becomes narrower. It is difficult to align with the neutral position, and the neutral position may be shifted due to oil temperature conditions or aging. Therefore, even if the neutral position is set by the setting means, the output shaft of the HST stops rotating. Otherwise, there is a problem that the vehicle does not stop normally.

[0006]

Means for Solving the Problems The present invention provides at least:
Shift position or shift amount (progress direction, shift position or shift amount)
Setting means for setting the gear ratio, changing means mechanically connected to the setting means for changing the speed ratio or the rotation speed of the output shaft (traveling direction, shift position or shift amount), and correction for forcibly controlling the changing means. A first object of the present invention is to provide a continuously variable transmission (hydraulic type) of a work vehicle having a control means and capable of avoiding a shock at the time of sudden deceleration or sudden stop. Therefore, first, when the setting means is rapidly switched from the high-speed side toward the neutral position or near neutral position, the correction control means forcibly reduces the moving speed of the changing means. I do.

Secondly, when the setting means is rapidly switched from the high-speed side to the neutral position or near neutral position, the setting means is moved from the neutral position or the position immediately before the neutral near position which is the target position of the setting means. The correction control means forcibly reduces the moving speed of the changing means up to the target position.

Thirdly, when the setting means is rapidly switched from the high speed side to the neutral position or the neutral position, the neutral position or the position immediately before the neutral position, which is the target position of the setting means, is set. Up to the target position, the moving speed of the changing means is forcibly reduced by the correction control means based on the detection of the output shaft speed of the continuously variable transmission.

Fourthly, in the continuously variable transmission for a work vehicle having the above-mentioned structure, wherein the rotation of the output shaft of the internal combustion engine is changed in combination with a subtransmission, the setting means is set to a neutral position or a neutral position from a high speed side. When the switching operation is rapidly performed toward the nearby position, the correction control unit controls to forcibly reduce the moving speed of the change unit, and the output shaft rotation speed of the internal combustion engine is controlled by the setting unit. This control is stopped when the rotational speed is equal to or less than the set rotational speed according to the above, or when the auxiliary transmission is in a predetermined set position.

A second object of the present invention is to provide a continuously variable transmission for a work vehicle in which the output shaft of the continuously variable transmission is reliably stopped when the setting means is set to a neutral or neutral position. Therefore, fifthly, when the setting device is operated to the neutral setting position and the changing device is set to the neutral position, the rotation speed of the output shaft of the continuously variable transmission is detected, and if the rotation speed is not 0, The correction control means controls the movement of the change means to the forward or reverse side to make the rotation speed substantially zero.

Sixth, when the continuously variable transmission of the work vehicle is a hydraulic continuously variable transmission, when the setting means is operated to the neutral set position and the change means is set to the neutral position, the non-continuous transmission is set to the neutral position. The rotational speed of the output shaft of the stepless transmission is detected, and the direction of rotation is detected by forward and reverse fluid pressure detecting means in the hydraulic circuit of the continuously variable transmission. The direction of rotation of the output shaft is determined based on whether the output shaft detects a speed increase or a deceleration by slightly moving the vehicle forward or backward, and the correction control unit moves the change unit forward. Alternatively, the rotation speed is set to substantially 0 by controlling the movement to the reverse side.

[0012]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a system block diagram of an HST relating to control of a continuously variable transmission of a work vehicle according to the present invention.
FIG. 3 is a block diagram showing an embodiment in which the HST control mechanism according to the present invention is applied to an agricultural work vehicle, FIG. 3 is a basic flowchart of HST control at the time of sudden stop or sudden deceleration to which shockless control is applied, and FIG. FIG. 5 is a flowchart of the HST control at the time of sudden stop or sudden deceleration in the case where the shockless control is performed immediately before the target neutral position or near the neutral position. FIG. FIG. 6 is an HST control flowchart. FIG. 6 shows an HST at the time of sudden stop or sudden deceleration including a process of avoiding shockless control during low idling work traveling.
FIG. 7 is a flowchart of the HST control at the time of sudden stop or sudden deceleration including a process of avoiding the shockless control when the gear is set to the predetermined speed in the sub-shift, and FIG. FIG. 9 is a flowchart of the HST control at the time of sudden stop or sudden deceleration in which the shockless control is avoided in any of the gear stages, and FIG. FIG. 10 is a flowchart of the HST control at the time of sudden stop or sudden deceleration to avoid shockless control. FIG. 10 is a flowchart of the HST control for surely stopping the rotation of the HST output shaft at the time of neutral operation of the HST operation lever. 11 is also HS by pressure detection of HST.
HST incorporating the process of determining the rotation direction of the T output shaft
FIG. 12 is an HST control flowchart including a process of judging the rotation direction by rotating the HST output shaft to one side at a low speed.

Assuming that the HST according to the present invention is applied to an agricultural work vehicle (agricultural tractor), the overall system structure of the HST will be described with reference to FIGS. HS
Various input means such as sensors and switches are provided in the HST main body 2, the main unit 3, and the governor 4 for the controller 1 for T control. First, these input means will be described. In the HST main body 2, a swash plate angle sensor S1 for detecting the angle of the movable swash plate 2a (HST changing means) of the hydraulic pump, and detecting the hydraulic pressure flowing to the forward side in the hydraulic circuit from the HST hydraulic pump to the hydraulic motor. A forward-side pressure sensor S2, a reverse-side pressure sensor S3 for detecting the hydraulic pressure flowing to the reverse side, and an output shaft rotation speed sensor S4 for detecting the rotation speed of the output shaft 2b of the HST.
From 2 · S3, the detected voltage value (A / D) is input to the controller 1, and the detected square wave signal is input from the output shaft speed sensor S4.

In the machine 3, H is a setting means (means for setting a traveling direction, a shift position or a shift amount) of the HST connected to the movable swash plate 2a by a mechanical link mechanism.
An ST operation lever 7 is provided, and an HST lever angle sensor S5 for detecting the rotation angle is provided. Further, an auxiliary transmission (transmission) 8 is provided between the HST and the axle, which is capable of changing the reduction ratio between the HST output shaft 2b and the axle to a plurality of speeds. A setting device (switch, lever, etc.) 9 is provided, and a sub-shift sensor S6 for detecting a set speed stage of the sub-shift setting device 9 is provided. Each detection signal of the HST lever angle sensor S5 and the sub speed sensor S6 is input to the controller 1. The machine 3 also has an automatic / manual switch SW1 for selecting whether the traveling speed is to travel automatically at a constant speed or to be in a state in which shifting can be performed manually.
Also, in addition to the one-touch lifting switch SW2 of the work machine, various switches SW, SW, such as a left brake switch, a right brake switch, a work machine lift switch, a down switch, and the like.
Are input to the controller 1 with each switching operation.

The engine 3 is equipped with an engine E,
The governor 4 for adjusting the fuel injection amount of the engine E uses an electronic governor, includes a load factor monitor M1 and an engine speed monitor M2 of an engine output shaft, and inputs respective monitor square waves to the controller 1.

As output means, there are an ascending actuator 10a and a descending actuator 10b of the work machine elevating means 10, and various display lamps 11 for displaying a mode setting, a failure, and the like.
・ OFF output is performed. Also, the battery checker 12
Are mutually communicated with the controller 1.

Normally, the movable swash plate 2a (ie, the change means) of the HST hydraulic pump which moves following the operation of the HST operation lever 7 (ie, the setting means) is provided as movable control means for compensating control. A plate control motor (D / C motor) 6 and a motor drive unit 5 for driving the movable swash plate control motor are provided. A normal output signal SG1, a reverse output signal SG2, and a drive stop output signal SG3 are output from the controller 1 to the motor drive unit 5. The forward rotation output signal SG1 and the reverse rotation output signal SG2 are ON / OFF output signals, which are alternately output, and one of SG1 and SG2 is output at the same time.
The drive stop output signal SG3 which is a PWM (pulse wave signal)
Is output, and the driving speed is determined by the duty value of the pulse wave. These output signals SG1, SG2, S
Based on G3, a drive signal SG5 is transmitted from the motor drive unit 5 to the movable swash plate control motor 6, and the movable swash plate control motor 6 is driven at a predetermined speed to the normal rotation side or the reverse rotation side, and The plate 2a is moved.

Thus, for example, the normal output signal SG1
And the drive stop output signal SG3 are output simultaneously,
When the movable swash plate 2a rotates forward (here, the forward side) of the movable swash plate control motor 6, a drive stop output signal SG is provided.
It moves at a speed based on the three pulse waves. Reverse output signal S
If G2 and the drive stop output signal S3 are output simultaneously,
The movable swash plate 2a moves to the reverse side at a predetermined speed.

The motor drive unit 5 is provided with an overload detection sensor S7. If an overload of the movable swash plate control motor 6 is detected, this detection signal (overload abnormality signal) SG4 is generated. It is input to the controller 1 and, based on this, the drive stop output signal SG3 is transmitted with the duty value of 0, and immediately stops the movable swash plate control motor 6.

On the other hand, the movable swash plate 2a is provided with limit positions in the forward and backward movement areas, and correspondingly, the movable swash plate control motor 6 also has a forward rotation limit and a reverse rotation limit. Is provided, and when the movable swash plate control motor 6 reaches each limit position, the forward rotation limit signal SG6 or the reverse rotation limit signal SG7 is input to the controller 1.

In the system configuration of the HST as described above, the present invention is controlled so as to avoid a shock at the time of sudden deceleration or sudden stop, and to surely stop at the time of the neutral setting operation of the setting means. A continuously variable transmission is provided. Hereinafter, this control will be described.

First, the former control for avoiding shock will be described. FIG. 3 is a basic flowchart of the operation. First, a lever position sensor value (LS) is read based on the detection voltage of the HST lever angle sensor S5 (St).
1) It is determined whether the lever position sensor value (LS) indicates a neutral value (St2). The output value (LS)
Is a small value on the neutral side irrespective of the forward side or the reverse side. (That is, it increases as the vehicle moves forward or backward from the neutral position.)

As long as the lever position sensor value (LS) does not indicate neutral (ie, unless the HST operating lever 7 reaches the neutral position), the position of the movable swash plate 2a of the HST hydraulic pump is determined by the swash plate angle sensor S1. (St3),
The detection signal value (SS) is input to the controller 1,
It is determined whether the movable swash plate 2a is at the neutral position (St.
4). Unless the swash plate position is neutral, the reading of the lever position sensor value (LS) is continuously performed, and the controller 1 continuously performs a comparison operation between the previous reading value and the present reading value (St5). .

Here, when the HST operation lever 7 is operated (speed-up operation and deceleration operation), the previous value and the current value of the lever position sensor value (LS) are different. In this lever operation, in the case of a deceleration operation, the previous value (LS)> the current value (LS). On the other hand, the rate of change during rapid operation of the HST operation lever 7 (current value (LS) / previous value (LS))
The reference value (SK) of the HST operation lever 7 is stored.
When the previous value (LS), which is the deceleration operation, is greater than the current value (LS), the controller 1 calculates the change rate (K) = current value (LS) / previous value (LS) (St6). A comparison operation between the calculated change rate (K) and the reference value (SK) is performed (St7). If the change rate (K) is smaller than the reference value (SK), the correction control means (movable swash plate control) is used. It is determined that the operation is a sudden stop operation or a sudden deceleration operation which is a control case of the motor 6), and the movable swash plate 2a is forcibly and slowly moved to the desired neutral position or neutral regardless of the rapid operation of the HST operation lever 7. Control to near position (shockless control)
(St8).

However, the above-mentioned shockless control is different from HS
If the operation is consistently performed from the start of the operation of the T operation lever 7 to the target neutral position or the position near the neutral position, the operation does not match the operation for the purpose of sudden stop or rapid deceleration. Therefore, the flowchart shown in FIG. 4 shows that the swash plate position sensor value (SS) indicates the position immediately before the swash plate neutral position sensor value (N) in the basic flowchart of FIG. A step of forcibly controlling the swash plate 2a is added. That is, (（N) indicates the width of the swash plate position sensor value in the shockless control range, and (N) + (▲ N) is set as the threshold value for the forced control operation of the movable swash plate 2a. Yes, a comparison operation between the swash plate position sensor value (SS) and the threshold value (N) + (▲ N) is performed (St7 +
a), the swash plate sensor value (SS) is equal to the threshold value (N) + (▲
N) When the following is obtained, the correction control means
The movable swash plate 2a is controlled slowly (St8). As described above, by performing the shockless control immediately before the target neutral position or immediately before the neutral position, a shock at the time of stopping or at the end of the deceleration operation is avoided. Until the start of the control of the correction control means, the change means (movable swash plate 2a) is rapidly moved to the neutral side via the mechanical link mechanism by the setting means (HST operation lever 7). The actual deceleration corresponds to the operation intended for rapid deceleration.

During the shockless control, the HS
If the rotational speed reduction amount of the T output shaft 2b, that is, the deceleration amount (▲ HR) can be variously set, the deceleration state by the shockless control can be changed to various conditions such as the setting stage of the sub-transmission and various operation states. It becomes possible to correspond. In this way, the deceleration amount (▲ HR) corresponding to various conditions is stored, and the deceleration amount (▲ HR) is set alternatively in response to a switch operation or the like. Then, as shown in the flowchart of FIG. 5, when the swash plate position sensor value (SS) enters the shockless control range (St7 + a), the HST output shaft rotation speed sensor S4 detects the HST output shaft 2b. The rotation speed is detected (St
9) A value obtained by subtracting the set deceleration amount (▲ HR) from the rotation speed sensor value (HR) ((HR) − (▲ HR)) is set as a target HST output shaft rotation speed sensor value (SR) ( St1
0), while continuing to detect the rotation speed of the HST output shaft 2b.
The movable swash plate 2a is forcibly and slowly moved by the correction control means until the detected value reaches the target rotational speed sensor value (SR) (St11). The movable swash plate 2a is moved to the neutral position by the HST operation lever 7 according to the intention.

Based on the flow of the movable swash plate control shown in FIG. 5, the flowcharts shown in FIGS.
A case is set for avoiding the shockless control of the movable swash plate 2a by the correction control means, and a step of determining whether or not this case is included is included. Here, the case of avoiding the shockless control means that the speed is low during work traveling, and it is inconvenient to stop slowly at this time, and the shockless control is unnecessary. During this work traveling, the load is applied and the engine is running in a low idling state, that is, the engine speed is lower than the set speed, and can be determined by reading the set speed and the engine speed and comparing and calculating. In addition, in the state where the sub-gear position is at a predetermined speed position that suggests traveling on a high-speed road, there is a high necessity for sudden stop or sudden deceleration to avoid danger, and the movable swash plate 2 in the shockless control is required.
The slow movement of a is rather dangerous.

A switch may be provided to select whether or not to perform shockless control. However, unnecessary shockless control may be performed due to forgetting to turn on / off the switch. In this regard, in the present invention, the step of determining the two cases is included in the control flowchart, so that the shockless control is automatically avoided in these cases.

The flowchart shown in FIG. 6 is for judging the low idling state to avoid the shockless control. That is, when the HST operation lever and the swash plate position are not neutral (St1 to St4), prior to the detection of the sudden stop or the rapid deceleration operation of the HST operation lever 7 (St5),
The engine speed (ER) is read by the speed monitor M2 of the governor 4 (St4 + a), and it is determined whether or not the engine speed (ER) is equal to or higher than the set speed (determined from LS) (St4 + b). If the number of rotations is equal to or more than the rotation speed, another routine (RO
UTIN).

The flowchart shown in FIG. 7 is for judging a state in which the sub-gear stage is at a predetermined speed stage (high-speed road traveling speed stage) to avoid shockless control. That is, HS
When the T operation lever and the swash plate are not in the neutral position (St1 to St4), prior to the detection of the sudden stop or the rapid deceleration operation of the HST operation lever 7 (St5), the speed stage of the subtransmission is set to the subtransmission sensor S6. To determine whether the gear is a gear for performing shockless control (St4).
+ C) If the gear is not the speed at which the shockless control is to be performed, the routine shifts to another routine for avoiding the shockless control.

The flowchart shown in FIG. 8 assumes that shockless control can be avoided when either of the cases is applicable. That is, when the HST operation lever and the swash plate are not in the neutral position, the engine speed (ER) is first read before detecting the sudden stop or the rapid deceleration operation of the HST operation lever 7 (St4).
+ A), it is determined whether or not the engine speed (ER) is greater than or equal to a set speed (determined from LS) (St4 + b)
If the rotation speed is equal to or higher than the set rotation speed, the flow shifts to another routine for stopping the shockless control. Further, the speed stage of the subtransmission is read by the subtransmission sensor S6, and it is determined whether or not the speed stage is to perform the shockless control (St4 + c).
If it is not the gear position at which the shockless control is performed, the process proceeds to another routine for avoiding the shockless control. When we determine that none of these cases apply,
A sudden stop or a sudden deceleration operation is determined by reading the lever position (LS), and shockless control is performed (St5).
~).

As described above, the shockless control is required when traveling on the road, and is not required during work traveling.
The detection can be performed by setting the automatic / manual switch SW1 in addition to detecting whether the engine speed is lower than the set speed. That is, during work traveling, the automatic / manual switch SW1 is set to the automatic mode so that the vehicle travels at a constant speed regardless of the increase or decrease in load. On the other hand, when traveling on the road, the automatic / manual switch SW1 is set to the manual mode so that the operator can arbitrarily perform a shift operation. Therefore, in the flowchart shown in FIG. 9, when the HST operation lever and the swash plate position are not neutral (St1 to St)
4) Before detecting the sudden stop or sudden deceleration operation of the HST operation lever 7 (St5), the automatic / manual switch SW1 is detected.
Is determined (St4 + d), and in the case of the automatic mode, the process proceeds to another routine for avoiding the shockless control.
In the case of manual operation, the process proceeds to a step of determining a sudden stop or a rapid deceleration operation of the HST operation lever 7 for shockless control (St5).

As means for determining whether the vehicle is traveling on the road or work, another one of the one-touch lifting and lowering switches S
There is W2. That is, if it is determined by the one-touch lifting switch SW2 that the work implement is in the ascending state, the vehicle is traveling on the road, so that the shockless control is performed. Conversely, if it is determined that the work implement is descending, the shockless control is avoided in the work traveling state.

The flowchart shown in FIG.
Step (St4 + a) of determining whether or not to perform the shockless control based on the detection of the engine speed in the illustrated flowchart.
Instead of the steps (b) to (b), the mode of the automatic / manual switch SW1 is determined (St4 + d).
As shown in the flowchart of FIG. 8, after the determination step (St4 + d) of the automatic / manual switch SW1 (after determination of the manual mode) in the flowchart of FIG. (St4 + c) may be included.

Next, a control flowchart for reliably stopping the HST output shaft at the time of neutral setting, which is the second object of the present invention, will be described with reference to FIGS. First, the basic flowchart shown in FIG. 10 will be described. It is determined whether the HST operation lever 7 is neutral based on the detection of the HST lever angle sensor S5 (St21). If the HST operation lever 7 is set to the neutral position, the movable inclination of the HST hydraulic pump is determined based on the detection of the swash plate angle sensor S1. It is determined whether the plate 2a is at the neutral position (St22). Movable swash plate 2a
If is not at the neutral position, it is corrected to the neutral position using the correction control means (St23).

When the movable swash plate 2a comes to the neutral position, the HST
The HST output shaft rotation speed (HR) is read by the output shaft sensor S4 (St24), and the HST output shaft rotation speed (H) is actually read.
R) is 0 (St2)
5). If the HST output shaft rotation speed (HR) is 0, the neutral position of the movable swash plate 2a is correctly set at least with respect to the rotation of the HST output shaft 2b, and control is returned (). However, this also includes a situation where the neutral position of the movable swash plate 2a does not match the neutral position of the HST operation lever 7, and in this case, the HST operation lever 7 as setting means and the movable swash plate as changing means are used. The correction is made by adjusting the mechanical link mechanism connecting the second link 2a and the like.

If the HST output shaft rotation speed (HR) is not 0, the rotation direction is determined (St26), and the movable swash plate 2a is moved by the correction control means in a direction to cancel the rotation. That is, if the rotation direction of the HST output shaft 2b is the reverse direction, the movable swash plate 2a is moved in the forward direction (St27),
If the rotation direction of the HST output shaft 2b is the forward direction, the movable swash plate 2a is moved in the reverse direction (St28), and the HST output shaft 2b is finally moved to the neutral position set by the HST operation lever 7. The rotation is set to 0 (this is called neutral control). In this case, the movable swash plate 2a is not at the original neutral position.

In performing the neutral control by the correction control means, there is a problem in reading the rotation direction of the HST output shaft 2b. One possibility is to use the HST output shaft rotation speed sensor S4. This can detect the rotation speed but cannot determine the rotation direction. However, if two are used so as to correspond to the forward side and the reverse side, the rotation direction can be determined.

As described above, as a method for determining the rotation direction of the HST output shaft 2b using an existing sensor without adding a sensor, a fluid pressure (hydraulic pressure) flowing through each hydraulic circuit on the forward side and the reverse side is used. ) To detect the forward pressure sensor S2 and the reverse pressure sensor S3. That is, as shown in FIG. 11, when the HST operation lever 7 is set to the neutral position and the movable swash plate 2a of the HST hydraulic pump is in the neutral position (St21 to St23), the sensor value (FP) of the forward pressure sensor S2 and Reverse side pressure sensor S3
Is read (St31), and the two sensor values are compared, that is, the pressure difference between the forward side and the reverse side is calculated (S31).
t32). Here, if there is no pressure difference, it is determined that the HST is correctly in the neutral state, and the routine returns. On the other hand, if there is a pressure difference, the HST output shaft rotation speed (HR) is set to 0 by the detection of the HST output shaft rotation speed sensor S4 to determine whether the HST output shaft 2b is actually rotating.
Is measured (St33). Where HST
If the output shaft rotation speed is 0, it means that the output shaft 2b is rotating even though the state of the hydraulic oil in the HST is in a neutral state, and the routine shifts to another routine for correcting this.

If the HST output shaft rotation speed (HR) is not 0, the rotation direction of the output shaft 2b is determined here. That is, the sensor values (FP ·
RP), and if the forward pressure sensor value (FP) is larger than the reverse pressure sensor value (RP) (St34), it is determined that the pressure oil flows to the reverse side and the hydraulic pressure is low, That is, it is determined that the output shaft 2b is rotating in the reverse direction, and the correction control means moves the movable swash plate 2a to the forward side (St27), and stops the rotation of the output shaft 2b. On the other hand, if the reverse pressure sensor value (RP) is greater than the forward pressure sensor value (FP) (St35), it is determined that the output shaft 2b is rotating in the forward direction, and the movable control plate 2a is determined by the correction control means. Is moved backward (St28), and the HST output shaft 2b is stopped.

The neutral control flowchart shown in FIG. 12 employs a method of judging the rotational direction without using such a sensor. First, the steps from St21 to St25 are the same as the basic flowchart shown in FIG.
When it is determined that the rotation speed (HR) of the HST output shaft 2b is 0, the movable swash plate 2a is minutely moved to any side (to the forward side in this embodiment) using the correction control means ( St41). At this point, the HST output shaft speed (D
HR) is read (St42) and compared with the HST output shaft rotation speed (HR) read in the previous St4 (St4).
3). When the subsequent rotation speed detection value (DHR) is lower than the previous rotation speed detection value (HR), the HST output shaft 2b has been decelerated, and has been slightly decelerated to the forward side and decelerated. The rotation direction of the output shaft 2b is determined to be the reverse side. Then, the movable swash plate 2a is moved forward by the correction control means (St27), and the rotation of the HST output shaft 2b is stopped. On the other hand, when the subsequent rotation speed detection value (DHR) is higher than the previous rotation speed detection value (HR), the speed of the HST output shaft 2b is increased, and the HST output shaft 2b is slightly rotated forward to increase the speed. Therefore, the rotation direction of the HST output shaft 2b is determined to be the forward side, and the movable swash plate 2a is moved backward by the correction control means (St28), and the rotation of the HST output shaft 2b is stopped.

[0042]

The present invention is applied to an agricultural work vehicle or the like. At least a setting means for setting a shift position or a shift amount, and a gear ratio or an output shaft mechanically connected to the setting means. A continuously variable transmission for a work vehicle, comprising a changing means for changing the number of revolutions and a correction control means for forcibly controlling the changing means, and having a configuration controlled as described above, Effect. First, as a first embodiment of the present invention, as a control configuration for shock mitigation at the time of sudden stop or sudden deceleration, as described in claim 1, the setting means is rapidly shifted from the high speed side to the neutral position or near neutral position. During the switching operation, the correction control means forcibly reduces the moving speed of the changing means, so that the changing means of the continuously variable transmission slowly moves despite the rapid operation of the setting means. Then, the vehicle arrives at the neutral position or near neutral position, so that the shock caused by sudden stop or sudden deceleration is reduced, and the burden on the operator who gets on the vehicle is reduced.

However, if it is assumed that the control of the changing means by the correction control means is performed consistently from the start of the operation of the setting means to the target neutral position or the position near the target neutral, the operator suddenly stops by the setting means. It is meaningless to operate quickly for the purpose of sudden deceleration. Therefore, when the setting means is rapidly switched from the high speed side to the neutral position or the neutral vicinity position, the position immediately before the neutral position or the neutral vicinity position which is the target position of the setting means is set. The correction control means forcibly lowers the moving speed of the changing means to the target position, so that a rapid operation or a sudden deceleration is performed for the purpose of sudden stop or sudden deceleration up to the neutral position or a position immediately before the neutral position. The movable swash plate quickly moves to the neutral side in synchronization with the movement of the setting means, and can be quickly stopped or decelerated in accordance with the operation purpose. The change means slowly moves to the nearby position by the correction control means, and even if the change control means is controlled by the correction control means only for such a limited short period of time, even if sudden stop or sudden deceleration occurs, Also that it is relaxed shock at the time of reaching the intended neutral position or target the vicinity of neutral position is when the generated shock, shock resistance effect is sufficiently obtained, the operator of the burden of riding in the vehicle becomes lighter.

Further, when the setting means is rapidly switched from the high speed side to the neutral position or the neutral near position, the neutral position or the neutral near position which is the target position of the setting means. From the position immediately before to the target position, the correction control means forcibly reduces the moving speed of the change means based on the detection of the output shaft rotation speed of the continuously variable transmission. In addition, deceleration control based on the detection of the output shaft rotation speed can be performed in accordance with the working conditions, etc., and the shock is alleviated in a deceleration state with a better feeling than simply moving the movable swash plate, and the desired stop is achieved. The position or the position near the stop is reached.

Such a shockless control is required when traveling on the road, and is not required when the vehicle is traveling at low speed, and is not required when traveling on a road. However, in certain cases, sudden stop or sudden deceleration is more important than shock mitigation, and such control may be a hindrance. It is conceivable to provide a switch for selecting whether or not to perform control, but it is assumed that the switch operation is forgotten. Therefore,
According to a fourth aspect of the present invention, there is provided a continuously variable transmission configured to shift the output shaft rotation of the internal combustion engine in combination with an auxiliary transmission according to the fourth aspect of the present invention. When the switching operation is rapidly performed toward the neutral position or the position near the neutral position, the correction control unit is configured to forcibly reduce the moving speed of the changing unit. This control is stopped when the rotational speed is equal to or less than the rotational speed set by the setting means or when the auxiliary transmission is at a predetermined set position. When the rotational speed is less than the rotation speed set by the means, it is determined that the vehicle is traveling, and when the auxiliary transmission is at a predetermined setting position, it is determined that the vehicle is traveling on a road that requires sudden stop or rapid deceleration. Or Not been made compulsory control of changing means by hazardous correction control unit I, by the operator's intention, by synchronously moving changing means to the operation of the setting means, it is possible to perform the sudden stop or deceleration of interest.

Next, as a control structure for the neutral position adjustment which is the second object of the present invention, the setting means is operated to the neutral set position and the changing means is set to the neutral position. Sometimes, the rotational speed of the output shaft of the continuously variable transmission is detected, and when the rotational speed is not 0, the correction control means controls the change means to move forward or backward to control the rotational speed. By setting to 0, the setting means and the change means are mechanically connected to each other, and the neutral position of the change means coincides with the stop position of the output shaft due to oil temperature conditions, aging, etc. Even if the situation does not occur, if the setting means is set to the neutral position, the output shaft of the continuously variable transmission can be stopped correspondingly, so that the vehicle can be stopped normally. In this way, it is not necessary to adjust the changing means having a narrow neutral range and the stop position of the output shaft one by one, so that the output of the continuously variable transmission can be changed to the neutral operation of the setting means in response to the state change of the changing means. The stop of the rotation of the shaft can be dealt with.

In the above-described control configuration, it is important to detect the rotation direction of the output shaft of the continuously variable transmission. Although the rotation speed sensor can detect the rotation speed, the number of used rotation speed sensors must be increased in order to detect the rotation speed. Therefore, when the setting means is operated to the neutral set position and the changing means is set to the neutral position, the rotation speed of the output shaft of the continuously variable transmission is detected and the rotation direction is changed. The output shaft is accelerated by detecting the forward and reverse fluid pressure detecting means in the hydraulic circuit of the continuously variable transmission, or by slightly moving the changing means to either forward or reverse. The rotation direction of the output shaft is determined depending on whether the rotation speed of the output shaft is detected or not, and the correction control unit controls the change unit to move forward or backward to set the rotation speed to zero. Therefore, by using the existing fluid pressure detecting means, or by a method of minutely moving the output shaft of the continuously variable transmission without using the detecting means, the rotation direction is detected, and without increasing the number of parts. Neutral of the setting means at low cost It become possible to control to stop the output shaft of the continuously variable transmission in response to work.

[Brief description of the drawings]

FIG. 1 is a system block diagram of an HST relating to control of a continuously variable transmission for a work vehicle according to the present invention.

FIG. 2 is a block diagram showing an embodiment when the HST control mechanism according to the present invention is applied to an agricultural work vehicle.

FIG. 3 is a basic flowchart of HST control at the time of sudden stop or sudden deceleration to which shockless control is applied.

FIG. 4 shows HS during sudden stop or sudden deceleration when performing shockless control immediately before a target neutral or near neutral position.
It is a T control flowchart figure.

FIG. 5 is a flowchart of an HST control at the time of sudden stop or sudden deceleration when shockless control is performed by setting a deceleration amount.

FIG. 6 is a flowchart of HST control at the time of sudden stop or sudden deceleration including a process of avoiding shockless control during low idling work traveling.

FIG. 7 is a flowchart of HST control at the time of sudden stop or sudden deceleration, which incorporates a process of avoiding shockless control when a predetermined shift speed is set in the sub-shift.

FIG. 8 is a flowchart of the HST control at the time of a sudden stop or a sudden deceleration in which the shockless control is avoided in either the case of low idling or the case where the auxiliary transmission is at a predetermined gear position.

FIG. 9 is a flowchart of the HST control at the time of sudden stop or sudden deceleration in which a traveling state is determined by an automatic / manual switch and shockless control is avoided during work traveling.

FIG. 10 is an HST control flowchart for surely stopping the rotation of the HST output shaft during the neutral operation of the HST operation lever.

FIG. 11 is an HST control flowchart including a process of determining the rotation direction of the HST output shaft by detecting the pressure of the HST.

FIG. 12 shows an HS including a process of judging the rotation direction by rotating the HST output shaft to one side at a low speed.
It is a T control flowchart figure.

[Explanation of symbols]

 Reference Signs List 1 controller 2 HST 2a (for hydraulic pump) movable swash plate 2b output shaft 3 main unit 4 governor 5 movable swash plate control motor drive unit 6 movable swash plate control motor 7 HST operating lever 8 auxiliary transmission (transmission) 9 auxiliary Shift setting device S1 Swash plate angle sensor S2 Forward pressure sensor S3 Reverse pressure sensor S4 HST output shaft speed sensor S5 HST lever angle sensor S6 Sub speed sensor M2 Speed monitor

Claims (6)

[Claims] At least a setting means for setting a shift position or a shift amount, a changing means mechanically connected to the setting means for changing a speed ratio or a rotation speed of an output shaft, and forcibly controlling the changing means A continuously variable transmission for a work vehicle, the correction control means comprising: a control unit for rapidly changing the setting means from a high-speed side to a neutral position or a position near neutral; A continuously variable transmission for a working vehicle, wherein the moving speed of the vehicle is forcibly reduced. 2. Setting means for setting at least a shift position or a shift amount; changing means mechanically connected to the setting means for changing a speed ratio or a rotation speed of an output shaft; and forcibly controlling the changing means. When the setting means is rapidly switched from a high speed side to a neutral position or a position near neutral, the neutral position which is the target position of the setting means is provided. A continuously variable transmission for a work vehicle, wherein the correction control means forcibly reduces the moving speed of the change means from the position immediately before the position or the position near the neutral position to the target position. 3. Setting means for setting at least a shift position or a shift amount; changing means mechanically connected to the setting means for changing a speed ratio or a rotation speed of an output shaft; and forcibly controlling the changing means. When the setting means is rapidly switched from a high speed side to a neutral position or a position near neutral, the neutral position which is the target position of the setting means is provided. The correction control means forcibly reduces the moving speed of the change means from the position immediately before the position or the position near the neutral position to the target position based on the detection of the output shaft rotation speed of the continuously variable transmission. A continuously variable transmission for a working vehicle. 4. At least a setting means for setting a shift position or a shift amount, a changing means mechanically connected to the setting means for changing a gear ratio or a rotation speed of an output shaft, and forcibly controlling the changing means. A continuously variable transmission for a work vehicle that shifts the output shaft rotation of the internal combustion engine in combination with a subtransmission, by moving the setting means from a high speed side to a neutral position or a position near neutral. When the switching operation is performed rapidly, the correction control means controls to forcibly reduce the moving speed of the change means, and the output shaft rotation speed of the internal combustion engine is equal to or less than the rotation speed set by the setting means. Wherein the control is stopped when the sub-transmission is in one of a predetermined set position and the sub-transmission is in a predetermined set position. 5. A setting means for setting at least a traveling direction, a shift position or a shift amount, and changing means mechanically connected to the setting means for changing a traveling direction, a gear ratio, or a rotation speed of an output shaft; And a correction control means for forcibly controlling the change means, wherein the setting means is operated to a neutral set position to set the change means to the neutral position, and The rotation speed of the output shaft is detected, and when the rotation speed is not 0, the correction control means controls the movement of the change means to the forward or reverse side to make the rotation speed substantially zero. Continuously variable transmission for working vehicles. 6. A setting means for setting at least a traveling direction, a shift position or a shift amount, and changing means mechanically connected to the setting means for changing a traveling direction, a gear ratio, or a rotation speed of an output shaft; And a correction control means for forcibly controlling the change means, wherein the stepless shift is performed when the setting means is operated to the neutral set position and the change means is set to the neutral position. The rotational speed of the output shaft of the device is detected, and the direction of rotation is detected by the forward and reverse fluid pressure detecting means in the hydraulic circuit of the continuously variable transmission, or the changing means is driven by the forward / reverse operation. By slightly moving to either side, the output shaft determines the rotation direction of the output shaft, depending on whether the output shaft detects acceleration or deceleration,
A continuously variable transmission for a working vehicle, wherein the correction control unit controls the change unit to move forward or backward so that the number of revolutions is substantially zero.