JP3375371B2 - Work vehicle transmission - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work vehicle transmission in which a hydraulic continuously variable transmission having good operability is interposed between an engine and a traveling device.

[0002]

2. Description of the Related Art Conventionally, a technique related to a transmission of a work vehicle in which a hydraulic continuously variable transmission having good operability is interposed between an engine and a traveling device has been known.

[0003]

SUMMARY OF THE INVENTION A hydraulic continuously variable transmission is capable of continuously changing the traveling speed of a vehicle,
It has the advantage that it is extremely easy to operate in reverse and shift. However, the hydraulic continuously variable transmission has a problem that the transmission efficiency when transmitting the engine rotation to the traveling device is poor, and the hydraulic continuously variable transmission is operated at the maximum output rotational speed for working. In this case, this poor transmission efficiency caused the horsepower of the engine to be insufficiently utilized in the working machine. Even when the work machine is driven with a margin, the vehicle speed cannot be increased beyond the maximum output speed of the hydraulic continuously variable transmission, so the work efficiency per unit time is always constant. It also had the problem. The present invention effectively utilizes the lost horsepower of a hydraulic continuously variable transmission to increase the working machine horsepower and the running horsepower.

[0004]

The problems to be solved by the present invention are as described above. Next, the means for solving the problems will be described. In the first aspect, between the first transmission shaft that connects the engine and the input portion of the hydraulic continuously variable transmission, and the second transmission shaft that connects the output portion of the hydraulic continuously variable transmission and the traveling device, in a state where the HST outputs the maximum output rotation, power by the HST
Without being transmitted, the second transmission shaft is driven at a rotation speed equal to the maximum output rotation speed from the first transmission shaft to the constant speed transmission state, and the second transmission shaft is driven at a rotation speed higher than the maximum output rotation speed. It is provided with a mechanical transmission device that can be switched to a high-speed transmission state.

In claim 2, in claim 1,
An engine is equipped with a control device for selectively switching the mechanical transmission device to a constant-speed transmission state or a speed-increasing transmission state and a load detection means for detecting a load applied to the working machine, and an engine via the mechanical transmission device. When the load on the work machine is less than the set value while the vehicle is connected to the traveling device, switching operation from the constant speed transmission state to the speed increasing transmission state is allowed, and when the setting value is exceeded, the speed increasing transmission is performed. The load detecting means is connected to the control device so as to prevent the switching operation to the state and maintain the constant speed transmission state.

According to another aspect of the present invention, there is provided a first transmission shaft connecting the engine and an input portion of the hydraulic continuously variable transmission, and a second transmission shaft connecting an output portion of the hydraulic continuously variable transmission and the traveling device. during sometimes the state where the HST outputs a maximum output rotational power transmission is by the hydraulic stepless transmission
Without, in which the operator arbitrarily from the first transmission shaft to the second transmission shaft, provided with the maximum output speed mechanical speedup driving device driven at a higher rotational speed than.

[0007]

[Operation] Next, the operation will be described. That is, when the hydraulic continuously variable transmission outputs the substantially maximum output speed, the first transmission shaft and the second
If the transmission shafts are interlocked with each other by the constant speed transmission state of the mechanical transmission without the hydraulic continuously variable transmission, the hydraulic pressure included in the traveling horsepower while maintaining the traveling speed. The horsepower equivalent to the horsepower loss of the continuously variable transmission can be effectively used as the horsepower of the working machine.

Then, when the first transmission shaft and the second transmission shaft are interlocked by switching to the speed-increasing transmission state of the mechanical transmission device, the working machine horsepower is maintained while increasing as described above. , The rotational speed of the second transmission shaft is higher than the maximum output rotational speed of the hydraulic continuously variable transmission, and the horsepower equivalent to the lost horsepower of the hydraulic continuously variable transmission is used as the traveling horsepower for increasing the traveling speed. It can be used effectively.

Further, the load detecting means automatically determines whether or not the load applied to the working machine is less than the set value, and when it is less than the set value, there is still a margin in horsepower consumed by the working machine. This means that the switching from the constant speed transmission state to the speed increase transmission state is allowed, and the traveling speed can be selectively increased. Also, when the set value is exceeded, there is no margin in the horsepower consumed by the working machine, and if the traveling speed increases here, the load on the working machine will increase more and more and there is a high possibility that the engine will stop. At this time,
The switching to the speed-increasing transmission state is prevented, the constant-speed transmission state is maintained, and the working machine horsepower is maintained in the increased state.

[0010]

EXAMPLES Next, examples will be described. 1 is a schematic front view of a transmission according to the present invention, FIG. 2 is a schematic front view of a transmission showing another embodiment of the present invention, FIG. 3 is a perspective view around a gear shift lever 1, FIG. 4 is a hydraulic circuit diagram, and FIG. Block diagrams, FIGS. 6 and 7 are graphs showing the relationship between vehicle speed and horsepower.

This will be described with reference to FIG. Pulleys 26 and 27 are fixed to the output shaft 14 of the engine E. The pulley 26 transmits power to an input pulley 28 of the work machine S via a belt. The other pulley 27 transmits power to the pulley 29 of the input shaft 15 of the transmission case M via a belt. A hydraulic clutch 1 in which gears 40 and 41 are loosely fitted on the first transmission shaft 15 and any one of the gears 40 and 41 is connectable to the first transmission shaft 15.
0 and 12 are juxtaposed. The pump shaft 16 is connected to the end of the first transmission shaft 15 via a hydraulic transmission clutch 11.
Are connected to drive the hydraulic pump P of the hydraulic continuously variable transmission H. By operating the swash plate of the hydraulic pump P, the hydraulic motor Mo is continuously variable in forward and backward directions. The second transmission shaft 18 is connected to the motor shaft 17 via the hydraulic transmission clutch 13, and on the second transmission shaft 18,
Gears 42 and 31 are fixed.

The gear 42 is always meshed with the gear 40, and the gear 31 is meshed with the gear 41, to constitute a mechanical transmission device G. The gear trains of the gear 42 and the gear 40 are set to a transmission ratio in which the second transmission shaft 18 is driven at a rotation speed substantially the same as the maximum output rotation speed of the hydraulic continuously variable transmission H, and a constant speed transmission state. Is obtained. Further, the gear train of the gear 31 and the gear 41 is set to a transmission ratio in which the second transmission shaft 18 is driven at a rotational speed higher than the maximum output rotational speed of the hydraulic continuously variable transmission H, and the speed increasing transmission state is set. You can get it. Switching between the two gear trains is performed by selectively connecting the clutches 12 and 10 described above.

The gear 42 is the gear 3 on the shaft 19.
3 is always meshed. Fixed gear 3 on shaft 19
3, 32 are constantly meshed with the loose fitting gears 35, 34 on the shaft 20, and by engaging the sliding engagement body 25, either one of the loose fitting gears 35, 34 is selectively engaged with the shaft. Connected to 20. This constitutes a mechanical auxiliary transmission mechanism. A fixed gear 36 on the shaft 20 meshes with a fixed gear 37 on the steering clutch shaft 21. Then, the final deceleration shaft 23 is passed through the steering clutches 38L and 38R and the steering brakes 39L and 39R on the steering brake shaft 22.
L and 23R are connected to axles 24L and 24R and a crawler type traveling device (not shown).

Next, the embodiment shown in FIG. 2 will be described. In the embodiment, the hydraulic pump P of the hydraulic continuously variable transmission H is used.
And the hydraulic motor Mo is configured separately. In this case, the transmission clutch 11 includes the first transmission shaft 14 that also serves as the output shaft of the engine E and the pump shaft 1 of the hydraulic pump P.
6 is interposed. Further, the transmission clutch 13 and the clutch 1 are mounted on the second transmission shaft 18 of the mission case M.
2 and the clutch 10 are interposed.

Next, the periphery of the speed change lever 1 for operating the swash plate of the hydraulic pump P will be described. As shown in FIG. 3, the shift lever 1 is configured to be rotatable forward and backward in the forward direction F and the reverse direction R inside the lever guide groove 5. An arm 6 projecting downward of the speed change lever 1 is interlocked with an arm 7 for operating a swash plate of the hydraulic pump P.
Further, there is arranged an end sensor 2 which comes into contact with the lever 1 and is turned on when the shift lever 1 is rotated to the forward stroke end position. The end sensor 2 is composed of a limit switch and the like. Further, a changeover switch 3 configured as a push button is arranged at the grip 8 at the upper end of the speed change lever 1. In the present embodiment, whether or not the maximum output speed of the hydraulic continuously variable transmission H has been reached is determined by detecting the maximum tilt position of the speed change lever 1 by the end sensor 2. A rotation speed detector may be provided in the transmission path from 17 to the axles 24L and 24R to detect the maximum output rotation speed of the hydraulic continuously variable transmission H.

Referring to FIG. Hydraulic pump Pa
Are hydraulic pressure sources of the hydraulic transmission clutches 11 and 13 and the clutches 10 and 12. The solenoid valve V is a three-position switching type, and the transmission clutches 11, 1 are deenergized by deactivating the solenoids a, b.
3 are simultaneously joined, a position where the clutch 12 is joined by exciting the solenoid a, and a position where the clutch 10 is joined by exciting the solenoid b. Relief valve L1
Is connected to the oil supply circuits of the transmission clutches 11 and 13 and the clutch 12 via the shuttle valve D, and adjusts to an appropriate clutch hydraulic pressure. The delay relief valve L2 is connected to the oil supply circuit of the clutch 10 so that the clutch 1 does not have a shock during speed-up transmission.
It is for joining 0.

Referring to FIG. The control device C outputs a switching signal for the solenoids a and b of the solenoid valve V to select the hydraulic continuously variable transmission H or the mechanical transmission device G, and when the mechanical transmission device G is selected. Is
Among them, the operation is switched to either the constant speed transmission state or the speed increasing transmission state. In addition to the electric signals from the end sensor 2 or the rotation speed detector and the changeover switch 3, the control device C receives a load detection means K1 for detecting a load applied to the working machine, and an arbitrary load. An electric signal from the setting means K2 for inputting the set value X is input.

The graphs showing the relationship between vehicle speed and horsepower in FIGS. 6 and 7 will be described based on the control contents of the controller C. The engine mounted on the vehicle has a predetermined engine horsepower w2. A relational line (a) shown by a solid line in the graph shows how the vehicle speed increases when the hydraulic continuously variable transmission H is interposed between the engine E and the traveling device. When the engine E drives the hydraulic continuously variable transmission H, the horsepower loss w1 is always generated. A relational line (b) indicated by a chain double-dashed line shows a vehicle speed-horsepower relationship when the engine E and the traveling device are connected to each other without interposing the hydraulic continuously variable transmission H.

When the speed change lever 1 is operated to the forward side, the controller C controls the solenoids a and b until it reaches the most forward position.
Are both de-energized to control the solenoid valve V and the transmission clutch 1
Place at the position where 1 and 13 are joined. Therefore, the engine rotation is transmitted to the traveling device via the hydraulic continuously variable transmission H.
When the speed change lever 1 is tilted to the maximum, the motor shaft 17 of the hydraulic continuously variable transmission H reaches the maximum output speed and the vehicle speed is h.
It becomes 1. This time point is indicated by a point (a '). The engine horsepower w2 at this point (a') is the work machine horsepower wa used to drive the work machine and the traveling horsepower wb used to drive the vehicle speed. Is divided into

However, since the shift lever 1 turns on the end sensor 2, the control device C energizes the solenoid a and switches the solenoid valve V to a position where the clutch 12 is engaged and the transmission clutches 11 and 13 are disengaged. . Therefore, while the vehicle speed h1 is maintained, the mechanical transmission G is switched to the constant speed transmission state so that the engine rotation is transmitted to the traveling device without the hydraulic continuously variable transmission H interposed therebetween, and the point (a ') is set. To automatically move to the point (b ') on the relationship line (b). Therefore, a portion corresponding to the above-described loss horsepower w1 is added to the working machine horsepower wa, and the horsepower available for the working machine increases.

The load on the working machine is constantly detected by the load detecting means K1, and the set load value X is set to a value equal to or less than the working machine horsepower wa.
When the operator turns on the changeover switch 3 and the load is less than the set value X, the control device C excites the solenoid b and switches the solenoid valve V to the position where the clutch 10 is engaged. Therefore, the vehicle speed is increased from h1 to h2 by switching to the speed-increasing transmission state of the mechanical transmission device, and the point (B ') further shifts to the point (B "). Is less than the set value X, it means that there is a margin in horsepower used in the work machine,
The work efficiency per unit time can be improved by effectively utilizing the amount corresponding to the lost horsepower w1 as the horsepower for increasing the vehicle speed Δh.

Then, when the operator turns on the changeover switch 3, the load applied to the working machine is already set to the set value X.
When it exceeds the above, the control device C does not excite the solenoid b and maintains the energized state of the solenoid a, so that the speed increasing transmission state does not occur and the point (b ′) of the relational line (b) is maintained and The amount corresponding to the lost horsepower w1 is increased as the driving horsepower of the working machine and the engine stop is not caused. When the mechanical transmission G is in the speed increasing transmission state and the load applied to the work machine exceeds the set value X, the operator releases the changeover switch 3 to change the vehicle speed to h2.
The engine stop can be avoided by automatically decelerating from 1 to h1 or operating the speed change lever 1 to the deceleration side.

[0023]

Since the present invention is constructed as described above, it has the following effects. That is, according to claim 1, when the first transmission shaft and the second transmission shaft are set to the constant speed transmission state of the mechanical transmission, the horsepower equivalent to the loss horsepower of the hydraulic continuously variable transmission is used by the working machine. It is effectively used as horsepower and can increase the working machine horsepower. Then, when the mechanical transmission is switched to the speed increasing transmission state, the rotation speed of the second transmission shaft becomes higher than the maximum output rotation speed of the hydraulic continuously variable transmission, which is equivalent to the loss horsepower of the hydraulic continuously variable transmission. The horsepower to be used is effectively used as the horsepower to increase the vehicle speed, and the work efficiency per unit time can be increased.

According to the second aspect of the present invention, even if the operator tries to switch the mechanical transmission to the speed increasing transmission state when an excessive load is applied to the working machine, the constant speed transmission state is automatically maintained. The work machine horsepower is maintained in an increased state, the engine stop is avoided, and the work is not unexpectedly interrupted.

According to the third aspect, the operator arbitrarily switches the first transmission shaft and the second transmission shaft from the state in which the maximum output rotation of the hydraulic continuously variable transmission is transmitted to the mechanical speed increasing transmission. By increasing the rotational speed of the second transmission shaft above the maximum output rotational speed of the hydraulic continuously variable transmission, the horsepower equivalent to the lost horsepower of the hydraulic continuously variable transmission is effectively used as running horsepower for increasing the vehicle speed. Therefore, the work efficiency per unit time can be arbitrarily increased without using a large horsepower engine.

[Brief description of drawings]

FIG. 1 is a schematic front view of a transmission of the present invention.

FIG. 2 is a schematic front view of a transmission according to another embodiment.

FIG. 3 is a perspective view around the shift lever 1.

FIG. 4 is a hydraulic circuit diagram.

FIG. 5 is a control block diagram.

FIG. 6 is a graph showing the relationship between vehicle speed and horsepower.

FIG. 7 is a graph showing the relationship between vehicle speed and horsepower.

[Explanation of symbols]

H hydraulic continuously variable transmission E engine G mechanical transmission K1 Working machine load detection means K2 setting means S work machine 1 shift lever 10 clutch 11 Transmission clutch 12 clutch 13 Transmission clutch

Claims (3)

(57) [Claims] 1. A first transmission shaft connecting an engine and an input portion of a hydraulic continuously variable transmission, and a second transmission shaft connecting an output portion of the hydraulic continuously variable transmission and a traveling device, in a state where HST outputs the maximum output rotation, oil
A constant speed transmission state in which the second transmission shaft is driven from the first transmission shaft at a rotation speed equal to the maximum output rotation speed without transmitting power by the pressure type continuously variable transmission, and the maximum output rotation speed. A work vehicle transmission characterized by being provided with a mechanical transmission device that can be switched between an increased speed transmission state that is driven at a rotational speed higher than the number of revolutions. 2. The mechanical transmission according to claim 1,
A control device for selectively switching between a constant-speed transmission state and a speed-up transmission state and a load detection means for detecting a load applied to the working machine are provided, and the engine is connected to the traveling device via the mechanical transmission device. When the load applied to the work implement is less than the set value, the switching operation from the constant speed transmission state to the speed increasing transmission state is permitted, and when the setting value is exceeded, the switching operation to the speed increasing transmission state is performed. A transmission for a work vehicle, characterized in that load detecting means is connected to a control device so as to prevent the transmission and maintain a constant speed transmission state. 3. A first transmission shaft connecting an engine and an input portion of a hydraulic continuously variable transmission, and a second transmission shaft connecting an output portion of the hydraulic continuously variable transmission and a traveling device. sometimes states HST and outputs the maximum output rotation, oil
The operator does not need to transmit power by the pressure type continuously variable transmission.
Over the to the second transmission shaft from optionally first transmission shaft, a transmission for a working vehicle, characterized in that a said maximum output speed mechanical speedup driving device driven at a higher rotational speed than.