JP2003130216A - Transmission for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a transmission for a working vehicle capable of performing a smooth shift operation and to perform swash plate control according to a rapid shift operation. SOLUTION: This transmission for the working vehicle adjusts a traveling speed and performs a shift by at least a variable displacement hydraulic continuously variable transmission 21 and a planetary mechanism 22. When the shift by the hydraulic continuously variable transmission 21 is switched to the shift by the hydraulic continuously variable transmission 21 and the planetary mechanism 22, a rate of change of a swash plate angle is maintained within a fixed range for a target value of the swash plate control of the hydraulic continuously variable transmission 21. A dead zone for a control value of an actuator 86 performing the swash plate control for the hydraulic continuously variable transmission 21 is estimated and control in a dead zone region is omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed change device and a speed change operation mechanism for a work vehicle. More specifically, the present invention relates to the structure and operating device of a transmission having a hydraulic continuously variable transmission (HST) and a planetary gear mechanism.

[0002]

2. Description of the Related Art Conventionally, a transmission having an HST and a planetary mechanism is known. For example, Japanese Patent Laid-Open No. 2001
It is disclosed in Japanese Patent Laid-Open No. 108061. this is,
In a hydraulic-mechanical transmission in which one is transmitted to the planetary gear mechanism and the other is transmitted to the planetary gear mechanism via HST to synthesize the engine power, when the traveling speed reaches a set speed, the swash plate actuator 94 of the HST 21 is used. And the electronic governor 93 are interlocked with each other to maintain the set speed. In addition, in this mechanism, the HST is used for the reverse and low speed forward regions, and the HST is used for medium and high speed forward movement.
The driving force is transmitted to the planetary gear mechanism to drive the vehicle by the combined driving force.

FIG. 8A is a diagram showing a conventional target value and actual measurement value of the swash plate angle. In FIG. 8A, the main shift lever is rotated at a constant speed toward the speed increasing side, and at time t1, H
Switching from the ST mode to the HMT mode is performed. Figure 8
As shown in (a), when the swash plate is operated with the conventional target value, the target value output from the controller changes rapidly at time t1. Hydraulic equipment is difficult to change rapidly. In particular, when the hydraulic device is feedback-controlled, the movement for correction becomes large, and the control becomes unstable if a sudden change occurs. That is, as shown in FIG. 8A, a sharp change in the angle occurs at the portion where the swash plate angle is reversed in the measured value.

FIG. 11 (a) is a diagram showing the relationship between the conventional valve command value (control current value to the actuator) and the rotational speed of the HST. The swash plate of the hydraulic transmission is controlled by an electromagnetic valve. By outputting a command value from the controller to the electromagnetic valve, the electromagnetic valve operates and the swash plate is hydraulically controlled. However, the electromagnetic valve has a dead zone that does not operate when the current of the command value is small. Therefore, as shown in FIG. 11A, when the command value of the valve is within the dead zone, the rotation speed of the HST hardly changes.

[0005]

In the above structure, H
When the ST mode is rapidly switched to the HMT mode, the swash plate control becomes unstable, and the swash plate control is rapidly performed. This may cause a shock when shifting. Further, in the dead zone of the electromagnetic valve, it is difficult to control the swash plate, which wastes time during gear shifting and makes it difficult to obtain a light shifting feeling. Further, the dead zone of the electromagnetic valve is often slightly different depending on the individual, and the behavior at the time of shifting may be slightly changed in each work vehicle in which the electromagnetic valve is arranged, resulting in individual difference.

[0006]

[Means for Solving the Problems] That is, the inventors take the following means for solving the problems. A transmission for adjusting a traveling speed according to claim 1,
In a transmission of a work vehicle, at least one of which has a variable displacement hydraulic continuously variable transmission and a planetary mechanism for shifting gears,
When switching from the hydraulic continuously variable transmission to the hydraulic continuously variable transmission and the planetary mechanism, the swash plate angle of the swash plate angle is different from the target value of the swash plate control of the hydraulic continuously variable transmission. Keep the rate of change within a certain range.

According to a second aspect of the present invention, there is provided a transmission for adjusting a traveling speed, wherein at least one of the transmissions has a variable displacement, and the transmission of a work vehicle is a hydraulic transmission. The dead zone for the control value of the actuator that controls the swash plate of the machine is predicted, and control in the dead zone is omitted.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described with reference to the drawings. FIG. 1 is an overall side view of a work vehicle, FIG. 2 is a schematic diagram showing a shift configuration of the work vehicle, FIG. 3 is a skeleton diagram showing a drive configuration of the work vehicle, FIG. 4 is a skeleton diagram showing a configuration of an HMT, and FIG. FIG. 6 is a development view showing the configurations of the planetary mechanism and the forward / reverse mechanism, FIG. 6 is a diagram showing the relationship between the discharge amount of the hydraulic pump and the gear ratio, FIG. 7 is a diagram showing the control configuration of the speed change mechanism, and FIG. 8 is a target of the swash plate angle. FIG. 9 is a diagram showing a time change of the measured value and the measured value, FIG. 9 is a diagram showing a process of generating the target value from the input value of the main shift lever, and FIG. FIG. 11 is a diagram showing the time change of the HST rotation speed and the valve command value of the actuator.

In FIG. 1, an embodiment in which a work vehicle is used as a tractor will be described from the overall structure. A front wheel 1 and a rear wheel 2 are supported at the front and rear of the machine, an engine 5 is arranged inside the front bonnet 6, and a steering handle 10 is provided at the rear of the bonnet 6 and at the rear of the steering handle 10. A seat 11 is arranged in the. Also,
A main gear shift lever 3, a sub gear shift lever 4, a height switching lever, etc. are provided on a side portion of the seat 11, and a forward / backward movement switching lever 7 as a forward / backward movement switching operation device is arranged on a side portion of a steering wheel column of the steering wheel 10. There is. The steering handle 10, the seat 11, the levers, and the like are arranged in a driving unit in the cabin 12.

Further, a transmission housing is arranged at the rear of the engine 5, a transmission case 9 is arranged at the rear of the transmission housing, and the power from the engine 5 is transmitted to the rear wheels 2 to drive the four wheels. It is possible to simultaneously transmit the driving force to the front wheels 1 via the mechanism.

Further, the driving force of the engine 5 is transmitted to the PTO shaft 15 protruding from the rear end of the transmission case 9, and is transmitted from the PTO shaft 15 via a universal joint (not shown) to the rear end of the machine body through a working machine mounting device. It is configured to drive the working machine that is installed. A brake pedal, a main clutch pedal, a diff lock pedal, etc. are provided on the lower front step of the seat 11.

Next, the transmission mechanism will be described with reference to FIG. In the speed change mechanism of the present invention, the output of the engine 5 is changed by the HST 21 and the planetary gear mechanism 22. Then, the shift or HST only by the HST21
21 HS and selection of the output shifted by the planetary mechanism 22
It is controlled by the T / HMT mechanism 23, and the auxiliary transmission mechanism 24 is arranged on the downstream side thereof. The output shaft (crankshaft) 25 of the engine 5 is extended to the rear of the fuselage,
The driving force is transmitted to 1 and the planetary gear mechanism 22. And HS
The driving force is selected by the T / HMT mechanism 23 and transmitted to the auxiliary transmission mechanism 24.

Next, the drive mechanism of the work vehicle is shown in FIG.
Will be described in more detail using. Behind the engine 5,
HST21 and planetary mechanism 22, and HST / HM
A T mechanism 23 is provided. The hydraulic pump 21 of the HST 21 is driven by the output shaft 25. Then, the gear that is inserted and fixed to the shaft extending from the output shaft 25 and meshes with the planetary mechanism also receives the driving force from the output shaft 25. The output shaft 25 is connected to the transmission shaft 41 via a PTO clutch (or damper) 33. The transmission shaft 41 transmits the driving force of the output shaft 25 to the PTO speed change mechanism 34. The driving force transmitted from the output shaft 25 drives the PTO shaft 15 via the PTO transmission mechanism 34 described above.

The HST 21 comprises a hydraulic pump 31 and a hydraulic motor 32. The driving force changed by the HST 21 is applied to the HST / HMT mechanism 23 and the planetary mechanism 2
It is introduced in 2. The HST / HMT mechanism 23 transmits the driving force changed by the HST 21 to the transmission shaft 42, or the HST 21 and the planetary mechanism 22.
It is selected whether to transmit the driving force that has been shifted by the transmission shaft 42 to the transmission shaft 42 or not to transmit the driving force of the engine 5 to the transmission shaft 42. The driving force is transmitted to the transmission shaft 42 via the HST / HMT mechanism 23. Transmission shaft 42
Is connected to the subtransmission mechanism 24, and changes the driving force transmitted to the front wheels 1 and the rear wheels 2 by the subtransmission mechanism 24. The rear wheels 2 are connected to the auxiliary transmission 22 via a diff mechanism 36, and the drive mechanism for the front wheels 1 is connected to a four-wheel drive switching mechanism 37.

Next, the structure of the HMT will be described with reference to FIGS. 4 and 5. The HMT mechanism mounted on the work vehicle is composed of the HST 21 and the planetary gear mechanism 22. The hydraulic pump 31 of the HST 21 has a drive shaft 67.
Is driven by the drive shaft 67, and the rear end of the drive shaft 67 is
It is connected to the. A gear 54 is inserted and fixed to the front portion of the transmission shaft 51, and the driving force is transmitted to the planetary gear mechanism 22 via the gear 54. In addition, the hydraulic motor 3 of the HST21
Reference numeral 2 is connected to a drive shaft 68, and transmits a drive force to the planetary gear mechanism 22 via a gear 56 integrally fixed to the drive shaft 68.

The gear 54 meshes with the gear 55, and the gear 55 is rotatably inserted into the transmission shaft 52. Further, the gear 55 is connected to a holding body that pivotally supports the planetary gears 58, 58. Then, the gear 55 and the holding body rotate integrally with respect to the transmission shaft 52. The planetary gears 58, 58 mesh with the sun gear 60 on the transmission shaft 52 side. The sun gear 60 is rotatably inserted into the transmission shaft 52 and rotates together with the gear 57. Further, the planetary gears 58, 58 mesh with the inner teeth of the ring gear 59. The ring gear 59 is rotatably fitted on the transmission shaft 52.

By adopting such a speed change mechanism, the speed is changed by the HST 21 in the reverse and low speed ranges,
In the medium and high speed range, the HMT mechanism shifts gears. That is, by selecting the clutch 61, the HST 21
Alternatively, the HMT mechanism is selected. For this reason, delicate speed adjustment can be easily performed in the reverse and low speed regions, and speed control can be smoothly performed. Further, even if the HST 21 fails, by fixing the drive shaft 68 on the hydraulic motor 32 side, it is possible to travel in an emergency.

Next, the relationship between the hydraulic oil discharge amount of the hydraulic pump of the HST 21 and the gear ratio of the work vehicle will be described. Figure 6
In the above, since the low speed and the reverse range are performed by the shift of the HST 21, the discharge amount of the hydraulic pump and the gear ratio (running speed) of the vehicle are proportional in the use range of the HST 21. Then, the gear shift operation by HMT is performed from the gear ratio V ₀ .
By gradually reducing the discharge amount, the gear ratio increases and the vehicle speed increases. The discharge amount becomes 0 at the gear ratio V ₁ . When the vehicle speed is further increased, the hydraulic oil discharge direction of the hydraulic pump 31 is reversed to increase the discharge amount. That is, the clutch is not required to be operated in the low speed range and reverse. In the low speed range and in the reverse, the clutch engagement / disengagement associated with the gear shift is not performed, so that the gear shift operation can be performed smoothly and smooth work can be performed. Further, the shift control can be easily performed, and the reliability of the shift mechanism is improved.

Next, the control configuration of the transmission will be described with reference to FIG.
Will be explained. The control of the speed change mechanism is performed by the controller 81 as shown in FIG. The controller 81 includes an electronic governor 84 arranged in the engine 5, a pickup 85 for detecting the rotational speed of the drive shaft of the hydraulic pump 31, a potentiometer 88 for recognizing the position of the main shift lever 3, and a position of the forward / backward lever 7. A potentiometer 87 for recognizing the above, a pickup 89 for detecting the rotation speed of the transmission shaft 42, an actuator 86 for controlling the swash plate of the hydraulic pump 31, and solenoid valves 82, 83 for connecting and disconnecting the clutch 61 are connected. Potentiometer 87
-By 88, the controller 81 can recognize the positions of the main speed change lever 3 and the forward / backward movement lever 7. Then, the swash plate control of the hydraulic pump 31 is performed in accordance with the position to connect and disconnect the clutch 61.

As described above, by separating the forward / reverse lever 7 and the main shift lever 3 into the work vehicle shift control device, the conventional vehicle operation configuration can be easily inherited. Then, the user of the work vehicle does not need to learn a new operation method, and the conventional operation experience can be utilized. The forward / backward lever 7 is also effective when operating a work machine such as a loader. It is possible to move forward and backward simultaneously with the operation of the loader, and it is possible to maintain the speed reproducibility of forward and backward movement.

Next, the hydraulic pump 31 in the HST 21
The swash plate control configuration will be described. A sensor capable of recognizing the position or the rotation angle of the main shift lever 3 is arranged near the main shift lever 3. In the present embodiment, the potentiometer 88 is provided at the base of the main transmission lever 3.
Is provided, and the position of the main shift lever 3 is recognized by the potentiometer 88. Then, the controller 81 recognizes the position of the main transmission lever 3. The controller 81 controls the shift according to the position of the main shift lever 3. Inside the controller 81, the swash plate angle of the hydraulic pump and the switching of the clutch 61 corresponding to the position of the main transmission lever 3 are set. Based on this setting, the swash plate angle is adjusted by the actuator 86 and Clutch control is performed by the valves 82 and 83.

The controller 81 includes a potentiometer 87 for recognizing the position of the forward / backward lever 7 and an HST.
/ HMT mechanism 23 electromagnetic valve 82 for connecting and disconnecting the clutch
・ 83 is connected. Then, the electromagnetic valves 82 and 83 are controlled in accordance with the forward (F), neutral (N), and reverse (R) positions of the forward / reverse lever 7 and the position of the main speed change lever 3 to control the clutch 61. It is something to do. That is, at the time of starting, the HST that is shifted by the HST
The vehicle is driven depending on the mode, and the gear ratio is a constant value (V ₁ )
When it becomes larger, the electromagnetic valves 82 and 83 are controlled to enter the HMT mode in which the vehicle is driven by the HMT.

Next, the configuration for switching between the HST mode and the HMT mode will be described with reference to FIG. Figure 8
FIG. 8A is a diagram showing a conventional target value and actually measured value of a swash plate angle, and FIG. 8B is a diagram showing a corrected target value and actually measured value of a swash plate angle. In FIGS. 8A and 8B, the main shift lever 3 is rotated to the speed increasing side at a constant speed. As a result, the instruction value given by the controller 81 is the target value. The measured value shows the actual swash plate angle at this time. Then, at time t1, the HST mode is switched to the HMT mode. As shown in FIG. 8A, when operating the swash plate with the conventional target value,
At time t1, the target value changes rapidly. Hydraulic equipment is difficult to change rapidly. In particular, when feedback control is performed on the hydraulic equipment, the movement for correction becomes large. That is, as shown in FIG. 8A, a sharp change in the angle occurs at the portion where the swash plate angle is reversed in the measured value.

However, by smoothly changing the target value, it is possible to smoothly switch from the HST mode to the HMT mode. As shown in FIG. 8B, it is possible to smooth the change in the swash plate angle by smoothing the target value. As a method for smoothing the target value, a moving average or a function is used to smooth the change in the target value.

Next, the structure for generating the target value will be described with reference to FIG. When the main transmission lever 3 is rotated so that the HST mode is switched to the HMT mode, the signal 100 is input to the controller 81. The signal 100 is converted into the swash plate angle of the HST 21 in the controller 81, and the signal 101 of the target value of the swash plate angle is calculated. This target value signal 101 is supplied to the filter circuit 102.
By passing through, the signal of the target value is smoothly converted into the signal 103. Since the target value for switching is smoothed in this way, the switching operation from the HST mode to the HMT mode can be performed smoothly.

In the above-described embodiment for generating the target value for swash plate control, the filter circuit 102 smoothes a discontinuous portion (a portion that becomes a differential load) with respect to a time change of an electronic target value signal. It is possible to use a smoothing circuit that performs the digitization. In addition to this, in the controller 81,
Calculate the swash plate change amount per unit time at the target value,
When the amount of change exceeds a certain value, it is possible to operate the smoothing circuit composed of a coil and a capacitor. It should be noted that as the unit time, it is possible to use an operation clock inside the controller 81 or a timer. In the controller 81, the target value signal 1
From 01, it is possible to calculate and output a smooth target value signal 103. At this time, it is possible to smooth the change of the target value by using a moving average or a function. Furthermore, when the swash plate change amount per unit time exceeds a certain value, the controller 81 causes the target value signal 10
Instead of 1, it is possible to output a signal 103 having a preset smooth target value. In this case,
The filter circuit 102 is a circuit that switches the target value signal 101 to the target value signal 103.

As a method of forming the target value signal 103, it is possible to use an average of changes in the target value (101) per unit time. This makes it possible to smooth the change in the target value even when the target value changes suddenly. For example, it is also possible to perform S-shaped acceleration / deceleration control on the swash plate. Smooth control can be performed by setting an S-shaped section and performing S-shaped acceleration / deceleration control in a region where the swash plate rotation changes rapidly. The S-shaped acceleration means that the acceleration is relatively slow at first, gradually increases, and then slowly again before reaching the maximum speed. The target value signal 103 can be calculated each time according to the target value, and it is also possible to output a preset smooth target value signal according to the degree of change of the target value.

Next, the control configuration of the swash plate in the operation (switching between normal rotation and reverse rotation) in which the rotation speed of the HST is reversed will be described. FIG. 10 shows the relationship between the current value applied to the actuator that controls the swash plate of the HST, the swash plate angle, and the output shaft rotation speed of the HST. As shown in FIG.
When the current related to the actuator is decreased from 0 to the minus direction, the swash plate angle does not change until a constant current value. However, when it exceeds a certain value, the swash plate angle is turned to the negative side.
Similarly, when the current is increased in the positive direction, if the value exceeds a certain value, the swash plate angle is rotated to the positive side. For this reason,
The rotational speed of the output shaft with respect to the electric current also becomes 0 in a constant range around 0, and the rotational speed increases as the swash plate rotates. That is, since the actuator 86 does not operate with respect to the current in the constant value range, a dead zone occurs when the current is controlled with respect to the actuator 86 in proportion to the rotation amount of the main transmission lever 3.

FIG. 11 (a) is a diagram showing the relationship between the conventional valve command value (control current value to the actuator) and the rotation speed of the HST, and FIG. 11 (b) is a valve command value and HST considering the dead zone. It is a figure which shows the relationship of the rotation speed of. Figure 11
In (a), when the valve command value is within the dead zone range, the rotation speed of the HST hardly changes. However, in FIG. 11B, the command value of the valve is controlled so as to exceed the dead zone, and the rotation speed of the HST is smoothly changed. That is, when accelerating the vehicle,
The dead zone is predicted and the current to the actuator 86 is controlled so as to fall outside the dead zone. As a result, it is possible to suppress a change in gear shifting performance due to variations in the actuator solids.

The dead zone of the valve can be predicted or recognized by the controller 81. As described above, the controller 81 includes the electronic governor 8
4. Pickups 85 and 89 are connected. The actuator 86 is controlled by the controller 81. That is, by recognizing the gear ratio with respect to the command value for the actuator 86, the dead zone of the actuator 86 in a constant state can be recognized. Thus, the dead zone of the actuator 86 in the gear shift operation is predicted, and the control without the dead zone is performed. That is, the dead zone of the actuator 86 is predicted, the control of the current value corresponding to the dead zone is omitted, and the current control that skips over the dead zone is performed. As a result, individual variations in the actuator 86 are eliminated, and it becomes possible to construct a work vehicle amount with stable gear shifting performance.

[0031]

According to a first aspect of the present invention, there is provided a transmission for adjusting a traveling speed, at least one of which is a variable continuously variable transmission having a variable displacement, and a planetary mechanism. At the time of switching from the shift by the hydraulic continuously variable transmission to the shift by the hydraulic continuously variable transmission and the planetary mechanism, the swash plate with respect to the target value of the swash plate control of the hydraulic continuously variable transmission is Since the change rate of the angle is maintained within a certain range, shifting from the hydraulic continuously variable transmission (HST mode) to shifting by the hydraulic continuously variable transmission and the planetary mechanism (HMT mode)
Switching to is smooth. By smoothly switching from the HST mode to the HMT mode, the load on the swash plate of the HST can be reduced and the load on the transmission mechanism can be reduced. The riding comfort of the work vehicle is improved.

According to a second aspect of the present invention, there is provided a transmission for adjusting the traveling speed, wherein at least one of the transmissions is a variable speed hydraulic continuously variable transmission for a work vehicle. Since the dead zone with respect to the control value of the actuator that controls the swash plate of the machine is predicted and the control in the dead zone is omitted, the responsiveness of the work vehicle to the shift can be improved. Further, it is possible to eliminate individual differences in behavior due to the electromagnetic valve.

[Brief description of drawings]

FIG. 1 is an overall side view of a work vehicle.

FIG. 2 is a schematic diagram showing a shift structure of a work vehicle.

FIG. 3 is a skeleton diagram showing a drive configuration of a work vehicle.

FIG. 4 is a skeleton diagram showing the configuration of HMT.

FIG. 5 is a development view showing configurations of a planetary mechanism and a forward / reverse rotation mechanism.

FIG. 6 is a diagram showing a relationship between a discharge amount of a hydraulic pump and a gear ratio.

FIG. 7 is a diagram showing a control configuration of a speed change mechanism.

FIG. 8 is a diagram showing a time change of a target value and an actually measured value of a swash plate angle.

FIG. 9 is a diagram showing a process of generating a target value from an input value of a main transmission lever.

FIG. 10 is a diagram showing a relationship between an output current value, a swash plate angle, and an output shaft rotation speed.

FIG. 11 is a diagram showing a time change of a HST rotation speed and a valve command value of an actuator.

[Explanation of symbols]

3 Main shift lever 7 Forward / backward lever 5 engine 15 PTO axis 21 HST 22 Planetary mechanism 23 Forward / reverse mechanism 24 Sub-transmission mechanism 31 hydraulic pump 32 hydraulic motor 61 clutch 81 controller 82 Solenoid valve 83 Solenoid valve 85 pickup 86 actuators 89 pickup

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akira Kuroda             1-32 Yanma, Chayamachi, Kita-ku, Osaka-shi, Osaka             ー Diesel Co., Ltd. F term (reference) 3J053 AA01 AB04 AB07 DA06 DA13                       DA21 EA01

Claims (2)

[Claims] 1. A transmission for adjusting traveling speed, comprising:
In a transmission of a work vehicle, at least one of which has a variable displacement hydraulic continuously variable transmission and a planetary mechanism for shifting gears,
When shifting from the hydraulic continuously variable transmission to the hydraulic continuously variable transmission and the planetary mechanism, the swash plate angle of the swash plate angle with respect to the target value of the swash plate control of the hydraulic continuously variable transmission is changed. A transmission for a work vehicle, characterized in that the rate of change is maintained within a certain range. 2. A transmission for adjusting a traveling speed, comprising:
In a transmission of a work vehicle in which at least one is changed from a variable displacement hydraulic continuously variable transmission, a dead zone for a control value of an actuator that performs swash plate control of the hydraulic continuously variable transmission is predicted, and control in a dead zone is performed. A transmission for a work vehicle, which is omitted.