JP2003130177A - Hydraulic-mechanical transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a hydraulic-mechanical transmission provided to a working vehicle, in which a movable swash plate of a hydraulic pump in the HST is controlled with the decrease in the volume efficiency of the HST, so as to achieve smooth traveling. SOLUTION: In the hydraulic-mechanical transmission (HMT), a swash plate angle of the HST is offset by a correction value Δr0 of a tilt angle (HST swash plate angle) of a movable swash plate 22a in a hydraulic pump 22, on the basis of a load applied to the HST21 on the decelerating side, when increasing vehicle speed and on the accelerating side, when reducing vehicle speed. The correction value Δr0 is determined on the basis of the value of the load, which is estimated from a difference between a rotation speed of an actual output shaft 27 and the rotation speed of an output shaft 27, which is detected in the immediately previous control loop and determined by a shift operating means, such as a main shift operating means 84, whereby the HST swash plate angle is subjected to the feedback control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic-mechanical transmission (HMT) provided in a work vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, there has been known a hydraulic-mechanical transmission (HMT) which is a combination of an HST (hydraulic continuously variable transmission) and a planetary gear mechanism. The HST links the movable swash plate of the variable displacement hydraulic pump with the main shift operating means, and rotates the main shift operating means to change the discharge amount from the hydraulic pump to change the output rotational speed. Then, the main gear shift is performed, and the main gear shift operation means is rotated in the opposite direction from the neutral position to switch between forward and backward movement so that the gear shift can be performed simultaneously.

And in the hydraulic-mechanical transmission,
For example, as disclosed in Japanese Patent Laid-Open No. 2001-108061, when the gear ratio of the transmission is lower than the set value, the first clutch is engaged to output the output rotation of the HST to the axle. When the speed ratio is increased and the gear ratio exceeds the set value, the second clutch is engaged to combine the output rotation of the HST and the output rotation of the engine to the axle. A device configured to output "HMT drive mode" has been proposed.

In the above-mentioned prior art, the "HST drive mode" and the "HMT drive mode" in that the gear ratio of the vehicle is accelerated or decelerated and becomes equal to the predetermined change gear ratio.
It is configured such that switching between the two is performed. However, if it is operated to switch to the "HMT drive mode" after it is detected that the gear ratio of the vehicle becomes equal to the switch gear ratio, an electrical time delay may occur until the "HMT drive mode" is actually entered. And a mechanical time delay causes a time lag, which causes a deviation between the output rotation of the HST and the output rotation of the HMT, which causes a shock at the time of mode switching. Further, in the HST, when the load becomes large, the hydraulic pressure in the circuit rises, and when the hydraulic pressure rises, the volume efficiency decreases due to oil leakage and compression due to the characteristics of the HST, and the angle of the movable swash plate of the hydraulic pump is constant. Even so, the rotation speed of the output shaft that interlocks with the axle of the hydraulic-mechanical transmission changes, that is, the vehicle speed changes. Therefore, a situation may occur in which desired acceleration and deceleration cannot be obtained unless control is performed in consideration of the load on the HST.

[0005]

Therefore, in the present invention, H
The load applied to the ST is detected, and the control for changing the HST swash plate angle to the deceleration side (or the acceleration side) is performed according to the detected value to eliminate the shock at the time of mode switching or acceleration / deceleration. To do.

[0006]

The problems to be solved by the present invention are as described above. Next, the means for solving the problems will be described.

That is, according to claim 1, in the hydraulic-mechanical transmission (HMT) equipped on the work vehicle,
The load on ST (Hydraulic continuously variable transmission) is configured to be detectable, and the value of the detected load on HST is to the deceleration side when increasing the vehicle speed and to the acceleration side when decelerating the vehicle speed. The HST swash plate angle is offset-controlled by a value determined according to the above.

According to a second aspect of the present invention, in the hydraulic-mechanical transmission according to the first aspect, the rotation speed of the output shaft of the transmission,
The load applied to the HST is detected from the difference between the target rotation speed corresponding to the target vehicle speed and the HST swash plate angle is feedback-controlled.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. FIG. 1 is a skeleton diagram of an HMT type transmission, and FIG.
FIG. 3 is a side sectional development view of the ST, FIG. 3 is a side sectional development view of the front part of the mission, and FIG. FIG. 5 is a diagram showing the relationship between the vehicle gear ratio and the HST gear ratio, FIG. 6 is a diagram showing the relationship between the HST gear ratio and time, and FIG. 7 is a main flow diagram relating to the speed control of the control device. 8 is a flow chart related to the HST swash plate angle control block,
FIG. 9 is a flow chart when switching from the HST mode to the HMT mode, and FIG. 10 is a chart showing control of the HST swash plate angle when switching from the HST mode to the HMT mode.
FIG. 1 is a diagram showing the control of the HST swash plate angle at the time of switching from the HST mode to the HMT mode, and FIG. 12 is a diagram showing the control of the HST swash plate angle at the time of switching from the HST mode to the HMT mode.

A working vehicle equipped with a hydraulic-mechanical transmission (HMT) according to this embodiment will be described below. [Travel Drive System] First, the travel drive system will be described. As shown in FIGS. 1 and 2, the HST 21 includes a hydraulic pump 22 and a hydraulic motor 23, both of which are attached to a flat center section 32, and the HST housing 3
It is housed in 1. The center section 32 is fixed to the mission case 33.

A pump output shaft 25 penetrates the rotary shaft center of the hydraulic pump 22 of the HST 21, and the pump output shaft 25
Transmits the power from the engine 20 which is a drive source to the hydraulic pump 22 and the planetary gear mechanism 10, and further transmits the power to the PTO shaft 5 via a PTO drive system described later.
Power is also transmitted to 3. The cylinder block 22b of the hydraulic pump 22 is engaged with the pump output shaft 25 to make it relatively unrotatable, and the cylinder block 22b is driven together with the pump output shaft 25. Plural plungers 22c are slidably arranged on the cylinder block 22b, and a movable swash plate 22a is in contact with the head of the plunger 22c. The movable swash plate 22a is pivotally supported so as to be tiltable, and the volume of the hydraulic pump 22 can be changed by adjusting the tilt angle.

The hydraulic oil discharged by the hydraulic pump 22 is sent to the hydraulic motor 23 via an oil passage provided in the center section 32. Then, similarly, by driving a fixed displacement hydraulic motor 23 composed of a cylinder block, a plunger, etc., the hydraulic motor 2
The configuration is such that the rotation speed and direction of the motor output shaft 26 of No. 3 are controlled. In addition, in the HST 21 of the present embodiment, only the hydraulic pump is a variable displacement type and the hydraulic motor is a fixed displacement type, but it is not limited to the HST having the configuration.
For example, the present invention can be applied to a configuration in which both the hydraulic pump and the hydraulic motor are of the variable displacement type.

The structure of the mission 30 will be described with reference to FIGS. The mission 30 is covered with a mission case 33, and a pump output shaft 25, a motor output shaft 26, an output shaft 27, an auxiliary transmission shaft 28, a PTO shaft 53, etc. are horizontally arranged in the mission case 33 in the front-rear direction. And are rotatably supported. Further, the planetary gear mechanism 10 is provided in the mission case 33. The planetary gear mechanism 10 is arranged behind the HST 21 and is composed of a sun gear 1, a planetary gear 2, a ring gear 3, a carrier 5 and the like, which will be described later.

On the other hand, the boss 3a of the ring gear 3 and the gear 12 are loosely fitted to the motor output shaft 26 of the HST 21, and the boss 3a of the ring gear 3 and the motor output shaft 26 are fitted.
A first hydraulic pack clutch 13 is provided between
The second hydraulic pack clutch 14 is interposed between the motor output shaft 26 and the motor output shaft 26. The two hydraulic pack clutches 13 and 14 are used for switching between two drive modes (HMT drive mode and HST drive mode), and the two hydraulic pack clutches 1 are used according to the drive mode.
By engaging one of the gears 3 and 14 and releasing the other, the power is transmitted to the output shaft 27 via either the ring gear 3 or the gear 12.

On the other hand, the pump output shaft 25 is the HST.
21 extends through the center section 32 of the transmission unit 21 into the transmission case 33, and the pump-side input gear 8 is fitted onto the extended portion. The pump-side input gear 8 and the gear 5a formed on the outer peripheral surface of the front portion of the carrier 5 concentrically fitted in the sun gear 1 mesh with each other to rotate the carrier 5. A plurality of planetary gears 2, 2 that mesh with the sun gear 1 and the ring gear 3 are supported by the carrier 5, and these sun gear 1 and planetary gears 2 are supported.
The planetary gear mechanism 10 is composed of 2, the ring gear 3, the carrier 5, and the like.

The planetary gear mechanism 10 will be described. The sun gear 1 as the first element of the planetary gear mechanism 10 is loosely fitted to the output shaft 27, and the planetary gear 2 meshes with the sun gear 1 and a ring gear 3 as a third element arranged concentrically with the sun gear 1. is doing. Here Planetary Gear 2
It is rotatably supported by a carrier 5, which is a second element loosely fitted on the output shaft 27, and is configured to be able to revolve with the carrier 5 while rotating. A gear 5a is formed in the front portion of the carrier 5, and the gear 5a meshes with a pump-side input gear 8 fitted on the pump output shaft 25.

On the other hand, the HST 21 is arranged in parallel with the output shaft 27.
Of the motor output shaft 26 is disposed, and the motor side input gear 9 is fixed on the motor output shaft 26.
The sun gear 1 is rotatably driven by meshing a gear 6 externally fitted and fixed to the front part of the sun gear 1 loosely fitted to the motor 7, and a motor-side input gear 9. On the motor output shaft 26, a gear 15 is further fixed behind the motor-side input gear 9, and the gear 15 is fixed.
Engages with the gear 12 loosely fitted on the output shaft 27.

As shown in FIG. 1, a transmission shaft 34 is connected to the rear end of the output shaft 27 via a coupling, and two gears 17 and 18 are fixed to the rear portion of the transmission shaft 34. The auxiliary transmission shaft 28 is supported in parallel with the transmission shaft 34,
Gears 60 and 61 are loosely fitted on the auxiliary transmission shaft 28, and the gears 60 and 61 mesh with the gears 17 and 18 and are driven at different rotational speeds. Then, by operating the auxiliary transmission clutch 62 provided on the auxiliary transmission shaft 28, the rotational driving force of either one of the gears 60 and 61 can be transmitted to the auxiliary transmission shaft 28, and the auxiliary transmission mechanism is constructed. I am configuring. A bevel gear 69 is formed at the rear end of the auxiliary transmission shaft 28, and the rear wheel differential 7 is inserted through the bevel gear 69.
Power is transmitted to 0.

Further, as shown in FIG. 1, two gears 63 and 64 are fixedly mounted on the front end portion of the auxiliary transmission shaft 28, and the gears 63 and 64 are loosely fitted on the front wheel output shaft 29. 65
66 are engaged with each other to drive the gears 65 and 66 at different rotational speeds. Further, two hydraulic clutches 67 and 68 are provided on the front wheel output shaft 29, and by connecting one of the hydraulic clutches 67 and 68, rotational drive of either one of the gears 65 and 66 is performed. The force can be transmitted to the front wheel output shaft 29 to form a front wheel speed increasing switching mechanism.

[PTO drive system] Next, referring to FIG.
The TO drive system will be described. The rear end of the pump output shaft 25 is transmitted to the PTO input shaft 41 via the PTO clutch 40. At the rear end of the PTO input shaft 41 are three gears 42.4
3 and 44 are fitted so as not to rotate relative to each other, and mesh with gears 46, 47, and 48 that are loosely fitted to the PTO auxiliary transmission shaft 45, respectively. The output that has been shifted in three stages by the operation of the PTO auxiliary shift clutch 49 is transmitted to the PTO shaft 53 via the gears 50, 52, and 54, and the power is transmitted to the working machine or the like.

[Drive transmission configuration in each drive mode] Next, in the transmission in the above configuration,
The drive transmission configuration of the traveling drive system in each drive mode of HMT / HST will be described.

[HMT Drive Mode] First, the drive transmission configuration in the HMT drive mode will be described. H
In the MT drive mode, the first hydraulic pack clutch 13 of the two hydraulic pack clutches 13 and 14 is engaged and the second hydraulic pack clutch 14 is disengaged.

Pump output shaft 2 connected to the engine 20
Since the pump-side input gear 8 fixed to the gear 5 meshes with the gear 5a formed on the carrier 5, the pump output shaft 2
The rotation output of 5 is transmitted to the carrier 5 of the planetary gear mechanism 10. On the other hand, the rotation output of the motor output shaft 26 causes the motor-side input gear 9 and the gear 6 fixed to the front portion of the sun gear 1 to mesh with each other, so that the sun gear 1 is rotationally driven. Therefore, the rotation of the both 5.1 is combined and transmitted to the planetary gear 2 which is supported by the carrier 5 and further meshes with the sun gear 1, and the combined driving force is transmitted to the planetary gear 2. It is transmitted to the meshing ring gear 3.

In the HMT drive mode, the first hydraulic pack clutch 13 is controlled to be engaged, so that the rotational power of the ring gear 3 is transmitted to the output shaft 27. The power of the output shaft 27 is transmitted to the rear wheels and the front wheels via the auxiliary transmission shaft 28, and the vehicle is driven.

[HST Drive Mode] Next, the drive transmission configuration in the HST drive mode will be described. HS
In the T drive mode, the second hydraulic pack clutch 14 of the two hydraulic pack clutches 13 and 14 is engaged, and the first hydraulic pack clutch 13 is disengaged.

Since the gear 15 is meshed with the gear 12 as described above, the rotation output of the motor output shaft 26 is transmitted to the output shaft 27. This power is transmitted to the rear wheels and the front wheels via the auxiliary transmission shaft 28, and the vehicle is driven.

In the HST drive mode, the power transmission structure does not pass through the planetary gear mechanism 10 until the output of the engine 20 is transmitted to the front and rear wheels.
That is, the output of the engine 20 drives the carrier 5 via the pump output shaft 25, but since the boss portion 3a of the ring gear 3 and the output shaft 27 do not engage with each other, the planetary gear mechanism 10 rotates idly by the rotation of the carrier 5. It is only supposed to do. Eventually, the output of the engine 20 is speed-changed by the HST 21 and transmitted from the motor output shaft 26 to the output shaft 27, and then is sub-speed-changed and transmitted to the front and rear wheels.

[Configuration of Drive Mode Switching Mechanism] Next, the configuration of the drive mode switching mechanism will be described. FIG. 4 is an explanatory view showing the structure of the drive mode switching mechanism of the transmission.

In this embodiment, as shown in FIGS. 3 and 4, a detector 81 provided close to the motor-side input gear 9 externally fitted to the motor output shaft 26 is used to detect the rotation amount of the motor output shaft 26. Is detected as a pulse signal, and its rotation direction can also be detected. Further, a detector 82 is also provided close to a dummy gear 82a fixed to the output shaft 27, and the detector 82 detects the rotation amount and the direction of the output shaft 27. Further, as shown in FIG.
The crankshaft is also provided with a detector 83 to detect the engine speed. Further, a main speed change lever 84, which is a main speed change operation means, is provided in a driver's seat of a vehicle, and a rotation angle detection means (for example, a potentiometer) 84a is arranged at a pivot portion of the main speed change lever 84. The operation position can be detected.

As shown in FIG. 4, the three detectors 81.
82 and 83 are electrically connected to the control device 90, and the control device 90 indicates the vehicle speed by the main speed change lever 84 based on the operation position of the main speed change lever 84 and the detection value of the detector 82. The inclination angle of the movable swash plate 22a of the hydraulic pump 22 is feedback-controlled through the HST swash plate angle actuator 86 so that the vehicle speed becomes higher. This will be described later. In addition, the first and second hydraulic pack clutches 13
Electromagnetic valves 91 and 92 are respectively connected to 14 so that pressure oil can be supplied and discharged, and the control device 90 is electrically connected to the electromagnetic valves 91 and 92.

The control device 90 has a calculating means for calculating the transmission gear ratio from the detection values of the detectors 82 and 83, and when the obtained gear ratio is in a constant region on the high speed side, the "HMT drive mode" is selected. ", And sends a signal to the solenoid valves 91 and 92 to engage the first hydraulic pack clutch 13 and disengage the second hydraulic pack clutch 14. On the other hand, when the gear ratio is in the constant range on the low speed side, the "HST drive mode" is set and the solenoid valves 91 and 92
To disengage the first hydraulic pack clutch 13 and engage the second hydraulic pack clutch 14. That is, in the medium speed range to the high speed range, the "HMT drive mode",
In the low speed range, two drive modes such as "HST drive mode" are automatically switched according to the gear ratio, and the solenoid valve 9
It is configured to electrically control the 1.92 to disengage the clutches 13 and 14.

Here, the movable swash plate 22a of the hydraulic pump 22 is
The feedback control of the tilt angle will be described. As described above, in the command value to the HST swash plate angle actuator 84 for obtaining the target gear ratio, the feedback control of the correction value Δr0 is intermittently performed on the tilt angle of the movable swash plate 22a of the hydraulic pump 22. .

In FIG. 11, the upper line indicates the movable swash plate 2 of the hydraulic pump 22 when the load applied to the HST 21 is large.
2A shows the relationship between the swash plate angle of 2a and the number of rotations of the hydraulic motor 23 per unit time, and the lower line shows the case where the load applied to the HST 21 is small. When the swash plate angle of the movable swash plate 22a is 0, the hydraulic pump 22 of the HST 21
Is in the neutral position. As shown in FIG. 11, the drive efficiency of the hydraulic motor 23 of the HST 21 changes depending on the load applied to the HST 21. The volumetric efficiency of HST21 is the temperature of hydraulic oil,
Depends on the degree of deterioration and the load on the HST 21.
For example, the volumetric efficiency changes due to oil leakage or compression caused by an increase in hydraulic pressure in the circuit due to the load applied to the HST 21, and deterioration over time due to repetition of these or changes in oil temperature. When the load on HST21 is large,
When the increase rate of the rotation speed of the hydraulic motor 23 is small with respect to the swash plate angle of the movable swash plate 22a and the load is small, the increase rate of the rotation speed of the hydraulic motor 23 with respect to the swash plate angle of the movable swash plate 22a. Grows larger. That is, even if the number of rotations of the hydraulic motor 23 per unit time is the same, the swash plate angle of the movable swash plate 22a of the hydraulic pump 22 varies depending on the load applied to the HST 21.

Therefore, when the volumetric efficiency of the HST 21 is changed, the HST swash plate angle actuator 8 is operated by the operation amount corresponding to the gear ratio determined by the operation of the main transmission lever 84.
Even if 6 changes the inclination angle of the movable swash plate 22a, a situation occurs in which the desired speed is not achieved. Therefore, the actuator 86
In consideration of the change of the volumetric efficiency in the operation amount, the offset angle of the tilt angle of the movable swash plate 22a is controlled by the correction value Δr0 to cope with the change of the volumetric efficiency of the HST 21.

The correction value Δr0 of the tilt angle of the movable swash plate 22a corresponding to the change in the volumetric efficiency of the HST 21 is HST.
It is determined from the value of the load applied to 21. Control device 90
Is a detector 83 for detecting the rotation speed of the engine 20, HS
The target of the output shaft 27 required for the gear ratio determined by the information from the detector 81 for detecting the hydraulic motor rotation speed of T21, the detection means 84a, 87a for detecting the main shift lever 84 position and the auxiliary shift switch 87 position, and the like. The difference M (M = Mp) between the target rotation speed Mp and the actual rotation speed m of the output shaft 27 obtained from the detector 82 that calculates the rotation speed Mp and detects the rotation speed of the output shaft 27 that is interlocked with the axle. -M) is calculated. By presuming that the value of the difference M calculated in this way is caused by the load applied to the HST 21, this is used as a standard of the load applied to the HST 21. Then, a map representing the correspondence between the value of the difference M and the correction value Δr0 is created in advance and stored in the control device 90, and the correction value Δr0 is determined based on the map.

The correction value Δr0 is determined according to the load applied to the HST detected in the control loop one time before, that is, the inclination of the movable swash plate 22a at the command value to the HST swash plate angle actuator 86. The angle (HST swash plate angle) is feedback-controlled. The correction value Δr0 is a value that corrects the inclination angle of the movable swash plate 22a toward the deceleration side when the main transmission lever 84 is operated to increase the speed of the vehicle. This is a value for correcting the tilt angle of the movable swash plate 22a on the speed increasing side when operating. Therefore, the inclination angle in the command value to the HST swash plate angle actuator 86 is corrected to the inclination angle r0 determined by the information from the detecting means 84a, 87a for detecting the main shift lever 84 position and the auxiliary shift switch 87 position. A value obtained by combining Δr0 (r = r0 + Δr
0). As described above, since the tilt angle of the movable swash plate 22a is intermittently feedback-controlled, fine control according to various situations is possible, and smooth acceleration can be achieved more stably.

Next, the structure for switching from the "HST drive mode" to the "HMT drive mode" in the drive mode switching mechanism will be described.

First, the relationship between the gear ratio of the HST and the gear ratio of the vehicle is shown in FIG. As described above, the entire range from the reverse drive range to the low forward drive range is set to the "HST drive mode",
In this mode, since the rotation output of the HST 21 is directly output to the output shaft 27, the vehicle is not driven when the HST 21 is in the neutral position, and the HST output shaft (motor output shaft) 26 is normally rotated. Is the vehicle moving forward,
When it reverses, the vehicle moves backward. The vehicle speed is proportional to the rotation speed of the output shaft 27. From this, "HS
In order to accelerate the vehicle to the forward side in the "T drive mode", it is necessary to change and control the gear ratio of the HST 21 to the forward rotation side.

On the other hand, the "HMT drive mode" is set in the forward medium speed range to the high speed range, and the HS mode is set in this mode.
The rotational output of T21 and the rotational output of the pump output shaft 25 are combined by the planetary gear mechanism 10, and the power differentially taken out is output to the output shaft 27. Therefore, in order to accelerate the vehicle to the forward side in the "HMT drive mode", it is necessary to change and control the gear ratio of the HST 21 to the reverse side contrary to the "HST drive mode".

Next, switching control of the clutch at the time of switching the drive mode will be described. At the time of switching the drive mode, the rotation speeds of the ring gear 3 and the gear 12 before and after the first and second hydraulic pack clutches 13 and 14 are equal, and the gear ratio of the vehicle is equal in either of the two modes. Exists, which is the point X in FIG. 5 in the present embodiment. The drive mode switching mechanism of the present invention is configured such that when the vehicle is accelerated or decelerated and the gear ratio of the vehicle reaches the point X, switching between the two drive modes is performed, and shocks at the time of switching are generated. We try to suppress the occurrence.

The control when the vehicle accelerates to the point X in the "HST drive mode" will now be described. That is, after the fact that the point X is reached is detected, "HMT
The signal is sent to the solenoid valves 91 and 92 in order to switch to the "driving mode". Therefore, after the control device 90 sends the signal, the clutches 13 and 14 are actually engaged or disengaged and the "HMT" is actually applied. Before the "drive mode" is set, there is a time lag (especially a mechanical time delay) due to an electrical time delay and a mechanical (hydraulic device etc.) time delay. At the time of operation, the first and second hydraulic pack clutches 13
The rotational speeds of the ring gear 3 and the gear 12 around 14 are deviated, which causes a shock at the time of mode switching.

Therefore, in the present invention, as shown in FIG. 6, for example, as shown in FIG.
From "HST mode" to "HMT mode" (or "HM
When switching from the "T mode" to the "HST mode"), the hydraulic / mechanical delay time Δt2 / Δt1 is measured in advance in each of the first hydraulic pack clutch 13 and the second hydraulic pack clutch 14, and the delay time Δt2 is measured.
・ If Δt1 is known, Δt2
The mode is switched at a time earlier by Δt1. In this way, the actual gear ratio is exactly the switching gear ratio v
When it becomes 1, the mode switching operation can be performed. That is, the control device 90 calculates the slope of the actual speed ratio, predicts the speed ratio after Δt1 (or after Δt2) from the current speed ratio and the calculated slope of the actual speed ratio, and the speed ratio is the switching speed ratio. If it has reached v1, the second hydraulic pack clutch 14 (or the first hydraulic pack clutch 1
The clutch switching operation is performed by sending a signal to the solenoid valve 92 (or solenoid valve 91) to engage 3).

Incidentally, in the drive mode switching at the point X, control is performed so that one of the two hydraulic pack clutches 13 and 14 is engaged and the other is disengaged, but in the present embodiment, switching is performed. At this time, the state in which both the hydraulic pack clutches 13 and 14 are both engaged is made to appear for a short time (Δt, which will be described later), so that the switching is smoothly performed.

The flow of processing performed inside the control device 90 in the drive mode switching mechanism of the present invention will be described below. FIG. 7 is a flowchart illustrating the main flow relating to the gear ratio control.

When the control loop starts in the gear ratio control, the current gear ratio of the transmission is calculated from the detection values of the rotation speed detectors 82 and 83 (S100).
And the current drive mode is "HST drive mode""H
"MT drive mode" is determined (S10
1) In the case of the "HST drive mode", the gear ratio after Δt1 of the gear ratio calculated previously is predicted, and whether the gear ratio exceeds a predetermined set value (switching gear ratio v1). Is determined (S102). If not, the HST swash plate angle control block described later is executed (S10).
3) The inclination angle of the movable swash plate 22a is changed according to the operation position of the main transmission lever 84. If it exceeds, "HM
In order to switch to the "T drive mode", a drive mode switching block described later is executed (S104).

The current drive mode is "HMT drive mode"
If it is, the gear ratio after Δt2 of the gear ratio calculated earlier is predicted, and it is determined whether the gear ratio is below a set value (switching gear ratio v1) (S105). If not, execute the HST swash plate angle control block (S1
03), the tilt angle of the movable swash plate 22a is changed according to the operation position of the main transmission lever 84. If it exceeds, "H
The drive mode switching block is executed to switch to the "ST drive mode" (S106).

In the HST swash plate angle control block shown in FIG. 8, first, the operation position of the main transmission lever 84 is detected, and the HST swash plate control target value is set to a value corresponding to the operation position (S201). ). Subsequently, the value commanded to the HST swash plate angle actuator 86 in the control loop one time before is subtracted from the HST swash plate control target value, and the calculated value and the set value E are compared (S202).

If the difference is less than the set value E, the control target value is directly commanded to the HST swash plate angle actuator 86 (S203). When the difference between the HST swash plate control target value and the previous command value is equal to or more than the set value E, the value commanded to the HST swash plate angle actuator 86 is obtained by adding or subtracting the set value E to the previous command value. Then, the value is set close to the control target value (S204). In this way, the amount by which the movable swash plate 22a is changed in one control loop is always the set value E.
It is ensured that the following is true, and it is possible to prevent extreme sudden acceleration / deceleration and avoid a severe shift shock.

Finally, the value previously commanded to the HST swash plate angle actuator 86 is held in the memory (S205), and the flow of the swash plate angle control block ends. This memory is an array memory and is capable of holding the value instructed to the actuator in each control loop from the present to a predetermined number of times before.

Next, the drive mode switching flow from "HST drive mode" to "HMT drive mode" will be described.

"HST drive mode" shown in FIG. 9
In the drive mode switching flow of the “HMT drive mode”, the gear ratio after Δt1 is predicted from the actual gear ratio, and when the gear ratio reaches the set value (switch gear ratio v1), the second hydraulic pack clutch 14 An engagement signal is transmitted to the solenoid valve 92 in order to engage (S301). 6 and 10
As shown in FIG. 5, in the present embodiment, the set time Δt1 is set to be the same as the response delay time of the second hydraulic pack clutch 14, and therefore, after the engagement signal is transmitted to the solenoid valve 92, After Δt1, the actual gear ratio is the switching gear ratio v1.
The second hydraulic pack clutch 14 is actually engaged at this time.

With this configuration, the rotation speed overrun of the HST output due to the time delay of the response of the second hydraulic pack clutch 14 is absorbed by the control, and when the mode is switched (specifically, the second The shock when the hydraulic pack clutch 14 is actually engaged is reduced. Therefore,
Acceleration accompanied by switching from "HST drive mode" to "HMT drive mode" can be smoothly performed. The control of the inclination angle of the movable swash plate 22a is similarly performed when the vehicle is decelerated and the "HMT drive mode" → "HST drive mode" is switched in the reverse manner to the above.

Therefore, at the same time as sending a signal to the solenoid valve 92 to engage the second pack clutch 14, the command value r1 before the time Δt1 is read from the memory and the HST swash plate angle actuator 86 is commanded (S302). ). That is, the value of the swash plate angle of the movable swash plate 22a corresponding to the switching speed ratio v1, which is the command value Δt1 before the signal is sent to the solenoid valve 92 to engage the second pack clutch 14. Let r1 be a command value of the swash plate angle of the movable swash plate 22a for the HST swash plate angle actuator 86.

Since the vehicle is accelerating, the value r1
Solenoid valve 92 to engage the second pack clutch 14.
From the value r2 commanded to the HST swash plate angle actuator 86 in the control loop just before sending the signal to the HST.
The value will be on the deceleration side. That is, at the same time as sending a signal to the electromagnetic valve 92 to engage the second pack clutch 14, the tilt angle of the movable swash plate 22a is controlled to the deceleration side.

Immediately after the control of the HST swash plate angle actuator 86 described above, time measurement is started (S3).
03), the loop is repeated without doing anything until the measured time reaches Δt−Δt2 (S304). After Δt−Δt2 has passed, a signal is sent to the HST swash plate angle actuator 86 so that the HST gear ratio gradually shifts to the deceleration side, and this is repeated until the measurement time passes Δt (S305 · S).
306). When Δt has elapsed, a signal is transmitted to the solenoid valve 91 to disengage the first hydraulic pack clutch 13 (S307). Immediately, the swash plate angle of the movable swash plate 22a of the HST 21 is tilted by Δr toward the forward rotation side,
Send a signal to the HST swash plate angle actuator 86 (S3
08), the control flow of the block ends.

Here, a fixed time (Δt-Δt) after the signal for engaging the second hydraulic pack clutch 14 is transmitted.
In 2), the tilt angle of the movable swash plate 22a is controlled to be constant, but after the time Δt−Δt2 has elapsed, HS
The HST swash plate angle is changed to H
Gradually decelerating as ST (increasing speed as a whole HMT)
The control is performed so that

That is, the HST 21 is decelerated at the timing after transmitting the signal for engaging the second hydraulic pack clutch 14 and before transmitting the signal for disengaging the first hydraulic pack clutch 13. The first pack clutch 1 is controlled by controlling the HST swash plate angle actuator 86.
3 is actually disengaged, and Δt2 after the signal for disengaging the first hydraulic pack clutch 13 is transmitted, the HST 21 causes the hydraulic pump to move from the target value r0 determined by the operation of the main shift lever 84. The movable swash plate 22a of No. 22 is tilted to the forward rotation side by the swash plate angle difference Δr.

Here, at the time of switching the drive mode, H
The correction control of the hydraulic pump swash plate angle in ST21 will be described. 11, the rotational speed Ra indicates the rotational speed of the hydraulic pump at the point X shown in FIG. At point X, "HST drive mode" to "HMT drive mode"
Or when the "HMT drive mode" is switched to the "HST drive mode", the load on the HST 21 changes. This is "HST mode" and "HM
This is because how the HST 21 applies a force to the hydraulic pump 22 when the mode is switched to the “T mode”. That is, in the “HST mode”, the hydraulic pump 22 rotates the hydraulic motor 23, whereas in the “HMT mode”, the hydraulic pump 22 suppresses the attempt to rotate the hydraulic motor 23. Therefore, it is necessary to correct the swash plate angle (correction of the swash plate angle difference Δr) due to the load in order to perform a smooth shift operation when switching the drive mode.

Therefore, as shown in FIG. 12, smooth shift control can be performed by adjusting the swash plate angle of the movable swash plate 22a of the hydraulic pump 22 in accordance with the load applied to the HST 21. That is, when the drive mode is switched, the swash plate angle difference Δr is corrected to enable smooth gear shifting. Specifically, by correcting the swash plate angle difference Δr, when switching from the “HST drive mode” to the “HMT drive mode”, the swash plate of the hydraulic pump is tilted to the forward rotation side by the swash plate angle difference Δr. , "HM
When switching from the “T drive mode” to the “HST drive mode”, the swash plate of the hydraulic pump is tilted to the neutral side by the swash plate angle difference Δr.

The swash plate angle difference Δr is caused by the magnitude of the load applied to the HST 21. As described above, the output shaft of the engine 20 is recognized by the detector 83, and the HS
The output of the hydraulic pump at T21 is recognized by the detector 81. Further, the angle of the hydraulic pump swash plate of the HST 21 is recognized by the actuator 86. This allows
The control device 90 recognizes the load applied to the HST 21, and calculates the swash plate angle difference Δr necessary for correcting the swash plate angle based on the recognition. That is, the control device 90 always recognizes the load applied to the HST 21, corrects the swash plate angle of the movable swash plate 22a with respect to the load when switching the drive mode, and realizes a smooth gear shift.

Thus, when switching the drive mode, the HST
The HST 21 is controlled to the deceleration side (the HMT speed-up side) in order to prevent a temporary drop in the vehicle speed due to a change in volumetric efficiency due to the load on the vehicle. Therefore, the HMT caused by the time delay of the response of the first hydraulic pack clutch 13 is caused.
When the drive mode is switched (specifically, when the disengagement of the first hydraulic pack clutch 13 is actually performed, the shortage of the output rotation speed is absorbed and the change in the volume efficiency of the HST 21 is covered. ).

[0062]

Since the present invention is constructed as described above,
The following effects are achieved.

That is, as described in claim 1, in the hydraulic-mechanical transmission (HMT) mounted on the work vehicle, H
The load on ST (Hydraulic continuously variable transmission) is configured to be detectable, and the value of the detected load on HST is to the deceleration side when increasing the vehicle speed and to the acceleration side when decelerating the vehicle speed. Since the HST swash plate angle is offset-controlled by a value determined in accordance with the above, it is possible to prevent a decrease in vehicle speed due to a change in HST volume efficiency, and obtain smooth acceleration or deceleration.

According to a second aspect of the present invention, in the hydraulic-mechanical transmission according to the first aspect, the rotational speed of the output shaft of the transmission and
The load on the HST is detected from the difference from the target speed corresponding to the target vehicle speed, and the HST swash plate angle is feedback-controlled. Therefore, the fluctuation of the volume efficiency of the HST at the time of shifting to the “HMT drive mode” is caused by the HST hydraulic oil. It is possible to perform fine control according to the situation, taking into account that it varies depending on the temperature of the vehicle and the load applied to the axle. Therefore, the vehicle speed can be prevented from temporarily dropping under various conditions, and smooth acceleration and deceleration can be stably obtained.

[Brief description of drawings]

FIG. 1 is a skeleton diagram of an HMT transmission.

FIG. 2 is a side sectional development view of the HST.

FIG. 3 is a side sectional development view of the front part of the mission.

FIG. 4 is an explanatory diagram showing a configuration for HST swash plate control.

FIG. 5 is a diagram showing a relationship between a vehicle gear ratio and an HST gear ratio.

FIG. 6 is a diagram showing a relationship between an HST gear ratio and time.

FIG. 7 is a main flow diagram relating to speed control of the control device.

FIG. 8 is a flowchart showing an HST swash plate angle control block.

FIG. 9 is a flowchart when switching from HST mode to HMT mode.

FIG. 10 is a diagram showing the control of the HST swash plate angle when switching from the HST mode to the HMT mode.

FIG. 11 is a diagram showing a relationship between a hydraulic pump swash plate angle and a rotational speed of a hydraulic motor per unit time.

FIG. 12 is a diagram showing a relationship between an HST hydraulic pump swash plate angle and a gear ratio.

[Explanation of symbols]

13 First hydraulic pack clutch 14 Second hydraulic pack clutch 20 engine 21 HST 22 Hydraulic pump 22a movable swash plate 23 Hydraulic motor 25 Pump output shaft 26 Motor output shaft 27 Output shaft 81 detector 82 detector 84 Main shift lever (main shift operating means) 84a detecting means 86 actuators 90 Control device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukio Kubota             1-32 Yanma, Chayamachi, Kita-ku, Osaka-shi, Osaka             -Agricultural machinery Co., Ltd. (72) Inventor Akira Kuroda             1-32 Yanma, Chayamachi, Kita-ku, Osaka-shi, Osaka             ー Diesel Co., Ltd. F-term (reference) 3J053 AB02 AB32 AB34 AB45 DA01                       DA07 EA02

Claims (2)

[Claims] 1. A hydraulic-mechanical transmission (HMT) mounted on a work vehicle, wherein a load applied to an HST (hydraulic continuously variable transmission) can be detected, and the deceleration side is used when increasing the vehicle speed. The hydraulic-mechanical transmission device is characterized in that when decelerating the vehicle speed, the HST swash plate angle is offset-controlled by a value determined according to the detected value of the load on the HST when decelerating. 2. The hydraulic-mechanical transmission according to claim 1, wherein the load applied to HST is detected from the difference between the rotation speed of the output shaft of the transmission and the target rotation speed corresponding to the target vehicle speed, and H
A hydraulic-mechanical transmission that is characterized in that the ST swash plate angle is feedback-controlled.