JP2002174333A - Wheel running type work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a gear shift shock when shifting down. SOLUTION: A wheel running type work vehicle is provided with a continuously variable gear shift hydraulic drive device 100 provided with a variable displacement hydraulic pump 10 and a variable displacement hydraulic motor 31, and a shifting gear unit 44 shifting an output of the continuously variable gear shift hydraulic drive device 100 to at least two stages. It takes Δt seconds from a shift down command to the completion of the shift down in the shifting gear unit 44. Then, a speed reduction amount α during Δt seconds is detected, and the speed reduction amount αis added to a reference speed Vo which becomes the start of outputting of a gear shift command to obtain a shift down instruction speed Vd. When a vehicle speed Va to be detected becomes the shift down instruction speed Vd, the shift down command is outputted. Consequently, the vehicle speed Va upon completion of shift down becomes the reference speed Vo.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheeled work vehicle such as a wheeled hydraulic excavator.

[0002]

2. Description of the Related Art Conventionally, a wheel type excavator has been
It has a continuously variable hydraulic drive that drives a variable displacement hydraulic motor with pressure oil discharged from a variable displacement hydraulic pump, and a transmission that shifts the output of the hydraulic motor between high and low levels. . In recent years, automatic transmissions that automatically shift from high to low in accordance with the detected vehicle speed have been developed.

A transmission mounted on a wheel type hydraulic excavator or the like transmits power from an output shaft of a hydraulic motor to a low side drive gear by a low side clutch, and transmits power from an output shaft of the hydraulic motor by a high side clutch. This is transmitted to the high side drive gear. That is, when downshifting in response to detection of a predetermined vehicle speed, the high-side clutch moves from the connected state to the disconnected state, and the low-side clutch moves from the disconnected state to the connected state. Since a predetermined time is required for such clutch switching, a shift shock occurs.

[0004] It is an object of the present invention to provide a wheel traveling type working vehicle which prevents a shift shock during downshifting.

[0005]

According to a first aspect of the present invention, there is provided a wheel traveling type work vehicle, comprising: a continuously variable hydraulic drive having a variable displacement hydraulic pump and a variable displacement hydraulic motor; and an output of the continuously variable hydraulic drive. A transmission that takes a predetermined time from a downshift command to the completion of downshifting, a vehicle speed detecting means for detecting the speed of the vehicle, and determining that the vehicle is decelerating. Deceleration determining means, a speed reduction amount calculating means for calculating a speed reduction amount of the vehicle which falls within a predetermined time, and a speed reduction amount calculated by the speed reduction amount calculating means and a preset reference speed. Calculating means for calculating a downshift instruction speed for downshifting the transmission, and when deceleration is determined by the deceleration determining means, the vehicle speed detected by the vehicle speed detecting means is shifted by the shift speed. By providing a shift instruction means for outputting a shift-down command when it reaches down instruction speed, to achieve the above object. (2) In the wheel traveling type work vehicle according to the first aspect, the shift instructing unit may be configured to shift the speed when the vehicle speed detected by the vehicle speed detecting unit becomes the shift-up instruction vehicle speed after the completion of the downshift. A shift-up command is output to the device. (3) In the wheel traveling type work vehicle according to the first aspect of the present invention, when the transmission is switched from the high speed side to the low speed side, the reference speed may be a predetermined number of revolutions of the hydraulic motor. It is characterized in that it is set so as not to exceed the maximum rotation speed. (4) According to a fourth aspect of the present invention, in the wheel traveling work vehicle according to any one of the first to third aspects, the shift instruction means calculates the downshift instruction speed by adding the speed reduction amount and the reference speed. It is characterized by.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where the present invention is applied to a wheel type hydraulic excavator will be described with reference to FIGS. The wheel type hydraulic excavator has a revolving body mounted on a traveling body so as to be revolvable, and a work attachment is attached to the revolving body. The traveling body is a continuously variable hydraulic drive 10 shown in FIG.
0 and driven by the transmission 44.

As shown in FIG. 1, the direction and flow rate of oil discharged from a variable displacement hydraulic pump (main pump) 10 driven by an engine 41 are controlled by a control valve 11, and a counter balance valve 42 is built in. The electric power is supplied to the traveling motor 31 via the brake valve 43. A transmission 44 (transmission) is connected to an output shaft of the traveling motor 31. Travel motor 31
Rotation of transmission 44, propeller shaft 4
5, The tire 47 is driven via the axle 46, and the wheel hydraulic excavator runs. The variable displacement hydraulic pump 10 and the variable displacement hydraulic motor 31 constitute a continuously variable hydraulic drive 100.

[0008] As shown in FIG.
Reference numeral 4 denotes an input gear 44a connected to the output shaft 31a of the traveling motor 31, a reduction gear 44b for reducing the rotational speed of the input gear 44a, and a high gear train 4 for rotating the reduction gear 44b.
4c connected to the high-side clutch 44d and the reduction gear 44
and a low-side clutch 44f for connecting the rotation of b to a low-side gear train 44e. High / low switching is performed by the high port 44H and the low port 44 of the transmission 44.
The control is performed by controlling the pressure of L by the clutch switching circuit 70.

The clutch switching circuit 70 includes a controller 2
Electromagnetic switching valve 71 which is switched by a switching command signal from
And a hydraulic pilot switching valve 72 that is switched by a control pilot pressure from an electromagnetic switching valve 71. When the electromagnetic switching valve 71 is switched to the H position, the hydraulic pilot switching valve 72 is also switched to the H position, a high pressure is applied to the high port 44H and a low pressure is applied to the low port 44L, and the transmission 44 is set to a high speed stage. That is, the high-side clutch 44d connects the reduction gear 44b and the high-side gear train 44c, and the low-side clutch 44f disconnects the connection between the reduction gear 44b and the low-side gear train 44e. On the other hand, the electromagnetic switching valve 71
Is switched to the L position, the hydraulic pilot switching valve 72
Is also switched to the L position, a low pressure is applied to the high port 44H and a high pressure is applied to the low port 44L, and the transmission 44
Is a low speed stage. That is, the low side clutch 44f connects the reduction gear 44b and the low side gear train 44e, and the high side clutch 44d connects the reduction gear 44b and the high side gear train 44e.
The connection with c is cut off.

The rotation speed of the output gear 44ea of the low gear train 44e is detected by the rotation sensor 21. Rotation sensor 21
Is converted into a vehicle speed signal Va by the FV converter 22 and input to the controller 23.

The displacement volume (tilt angle) of the main pump 10
Is adjusted by the regulator 48 according to the pump discharge pressure. The switching direction and stroke amount of the control valve 11 are controlled by a pilot pressure from a pilot circuit. The travel speed of the vehicle can be controlled by adjusting the stroke amount. The pilot circuit includes a pilot pump 10A, a traveling pilot valve 52 that generates a pilot secondary pressure in response to depression of an accelerator pedal 51, and a slow return valve that follows the pilot valve 52 and delays return oil to the pilot valve 52. 53 and a forward / backward switching valve 54 following the slow return valve 53 for selecting forward, backward or neutral of the vehicle. The pilot pressure is a pressure sensor 69
And is input to the controller 23.

FIG. 1 shows a state in which the forward / reverse switching valve 54 is neutral (N position) and the traveling pilot valve 52 is not operated.
Is in the neutral position, the pressure oil from the main pump 10 returns to the tank, and the vehicle is stopped. Forward / reverse switching valve 54
Is switched to forward (F position) or reverse (R position) and the accelerator pedal 51 is depressed, a pilot secondary pressure corresponding to the depression amount is generated. Accelerator pedal 51
The pilot pressure generated in proportion to the above operation is output as forward pilot pressure oil or reverse pilot pressure oil through the forward / reverse switching valve 54,
Act on pilot ports. Control valve 1
1 is switched by a stroke amount according to the pilot pressure. By switching the control valve 11, the oil discharged from the main pump 10 is guided to the traveling motor 31 via the control valve 11, the center joint 55, and the brake valve 43, and the traveling motor 31 is driven. The vehicle travels with the drive output taken out from 44.

The traveling motor 31 is provided with a self-pressure tilt control mechanism. The driving motor 31 is driven at a low speed and a high torque by increasing the volume as the driving pressure is increased. Drive with low torque. The driving pressure acts on the control piston 58 and the servo valve 59 of the traveling motor 31 from the shuttle valve 56.

When the accelerator pedal 51 is released during traveling, the traveling pilot valve 52 shuts off the pressure oil from the pilot pump 10A, and the outlet port thereof communicates with the tank.
As a result, the pressure oil acting on the pilot port of the control valve 11 returns to the tank via the forward / reverse switching valve 54, the slow return valve 53, and the traveling pilot valve 52. At this time, since the return oil is throttled by the throttle of the slow return valve 53, the control valve 11 is gradually switched to the neutral position. When the control valve 11 is switched to the neutral position, the oil discharged from the main pump 10 returns to the tank and the hydraulic oil
(Drive pressure) supply is cut off and the counterbalance valve 4
2 also switches to the illustrated neutral position.

In this case, the vehicle body continues to travel due to the inertial force of the vehicle body, and the traveling motor 31 changes from a motor operation to a pump operation, and the B port side in the drawing draws air and the A port side discharges. The pressure oil from the travel motor 31 is throttled by the throttle (neutral throttle) of the counter balance valve 42, so that the pressure between the counter balance valve 42 and the travel motor 31 increases and acts as a brake pressure on the travel motor 31. . As a result, the traveling motor 31 generates a braking torque to brake the vehicle body. If the amount of suction oil is insufficient during the operation of the pump, the travel motor 31 is replenished with the amount of oil from the makeup port MP.

When the accelerator pedal 51 is released on a downhill, a hydraulic brake is generated as in the case of deceleration described above.
Go down the hill by inertial running while braking the vehicle. When going downhill,
Even when the accelerator pedal 51 is depressed, the counter balance valve 42 operates to generate a hydraulic brake pressure so as to attain a motor rotation speed (running speed) corresponding to the flow rate of flow from the main pump 10 to the running motor 31.

FIG. 3 is a flowchart showing a processing procedure for controlling the transmission 44 and the like. This flowchart is processed by a program executed by the CPU in the controller 23.

In step S1 of FIG. 3, the speed signal Va is read from the F / V converter 22, and the speed signal Va is read in step S2.
Calculate the deceleration with. The deceleration is calculated from at least two or more speed signals Va having a time difference. If it is determined in step S3 that the vehicle is in the deceleration state based on the deceleration calculated in step S2, the process proceeds to step S4,
The speed reduction amount α (km / h) is calculated from the following equation.

Α = VΔt + Vc (1) VΔt: speed reduction amount in Δt seconds (km / h) Vc: constant determined by vehicle (km / h) where Δt is from high side to low side This is the time required to switch the clutch. In other words, Δt is the time required from the output of the downshift command to the completion of the downshift. This Δt differs depending on the model.

In step S5, a downshift instruction speed Vd (km / h) for instructing a downshift from the following equation:
Calculate

Vd = Vo + α (2) Vo: Reference vehicle speed, which is predetermined (km / h)

If it is determined in step S6 that the accelerator pedal is full, the process proceeds to step S7. The full accelerator is determined based on the magnitude of the traveling pilot pressure Pt from the pressure sensor 69. If it is determined in step S7 that the speed signal Va is equal to or lower than Vd, the process proceeds to step S8. Step S
At 8, a downshift command, that is, a clutch low switching signal is output to the clutch switching electromagnetic switching valve 71. As a result, the clutch switching electromagnetic switching valve 71 and the hydraulic pilot switching valve 72 are switched to the L side, the high side clutch 44f is driven in the disengagement direction, and the low side clutch 44
d is driven to the connection side. Then, after Δt seconds, the shift down of the transmission 44 to the lower speed stage is completed.

When it is determined in step S9 that the speed signal Va has become equal to or higher than the reference speed Vo, in step S10, a shift-up command, that is, a clutch high switching signal is output to the clutch switching electromagnetic switching valve 71. I do. As a result, the clutch switching electromagnetic switching valve 71
And the hydraulic pilot switching valve 72 is switched to the H side, the low side clutch 44d is driven in the disconnection direction, and the high side clutch 44f is driven to the connection side. Then, after Δt seconds, the upshift of the transmission 44 to the high speed stage is completed. Then, the process returns to step S1.

If the vehicle is not decelerating (step S3)
When the vehicle speed is not reduced to the predetermined value (when step S7 is denied), the process returns to step S1.

A specific operation based on such shift control will be described. When the vehicle enters the uphill road while the transmission 44 is running at the high speed, that is, at the high speed, step S2
It is determined from the deceleration calculated in that the vehicle is decelerating. In this case, the speed reduction amount α for Δt seconds is calculated, and the speed reduction amount α is added to the preset reference speed Vo to calculate the vehicle speed Vd for outputting the downshift instruction.

The reference speed Vo can be set as follows. FIG. 4 is a running performance curve with the vehicle speed (km / h) on the horizontal axis and the driving force (kN) on the vertical axis. The diagram H shows the characteristics when the transmission 44 is set to the high speed stage, and the diagram L shows the characteristics when the transmission 44 is set to the low speed stage. At the intersection of the characteristics H and L, the traveling drive force at the high speed stage and the low speed stage match, and at this point, shifting from the high speed stage to the low speed stage is preferable because there is no change in the traveling drive force. Therefore, in this embodiment, the vehicle speed Vo at the intersection is set as the reference speed.
Further, if the vehicle shifts down below this vehicle speed, the rotational speed of the hydraulic motor 31 does not exceed a predetermined maximum rotational speed, for example, a rated maximum rotational speed, and the motor overspeed can be reliably prevented.

As described above, when shifting the transmission from the high gear to the low gear, it takes Δt seconds from the downshift command to the completion of the downshift. Therefore, when the downshift is completed at the reference speed Vo, it is necessary to take into account the vehicle speed fluctuation for Δt seconds. In order to make the reference speed Vo by the speed decrease for Δt seconds, a downshift instruction speed Vd for instructing a downshift is calculated based on the above equation (2) (step S5).

In the full accelerator state, when the speed signal Va output from the F / V converter 22 becomes the downshift command speed Vd (step S7), the controller 23
Outputs a downshift command to the shift electromagnetic switching valve 71 (step S8). The electromagnetic switching valve 71 is switched to the L position, and the hydraulic pilot switching valve 72 is also switched to the L position.
As a result, a low pressure is applied to the high port 44H, and a high pressure is applied to the low port 44L.
b and the low-side gear train 44e start to shift from disconnection to connection, respectively. After Δt seconds, the high-side clutch 44d
Thus, the reduction gear 44b and the high-side gear train 44c are disconnected, and the low-speed clutch 44f connects the reduction gear 44b and the low-side gear train 44e to complete the downshift. Therefore, since the downshift is completed at the reference speed Vo, the fluctuation of the horsepower accompanying the shift can be reduced, and the shift shock can be reduced.

When the vehicle speed signal Va output from the F / V converter 22 becomes the shift-up instruction vehicle speed Vo (step S9), the controller 23 outputs a shift-up command to the shift electromagnetic switching valve 71 (step S10). The electromagnetic switching valve 71 is switched to the H position, and the hydraulic pilot switching valve 72 is also switched to the H position. As a result, a high pressure is applied to the high port 44H and a low pressure is applied to the low port 44L. The low side clutch 44f causes the reduction gear 44b and the low side gear train 44e to be disconnected from the connected state. Side gear train 44c
Begin to transition from disconnection to connection. And
After Δt seconds, the low speed clutch 44f is operated by the low side clutch 44f.
b is disconnected from the low-side gear train 44e, and the reduction gear 44b and the high-side gear train 44c are connected by the high-side clutch 44d, thereby completing the upshift.

The transmission may have three or more stages. In this case, the present invention can be applied to any case where the gear is downshifted from the third gear to the second gear and from the second gear to the first gear. Further, the vehicle speed at which the traveling driving force is constant irrespective of the gear ratio is set as the reference speed Vo at the time of downshifting. However, the reference speed Vo can be set from various viewpoints as long as the hydraulic motor does not rotate excessively. Also, the wheel type excavator has been described above. However, as long as the vehicle includes a continuously variable hydraulic drive device and a transmission, the present invention is applicable to a wheel traveling type work vehicle other than the excavator such as a wheel loader, a truck crane, and a rough terrain crane. The invention is equally applicable.

[0029]

As described above, according to the present invention, the shift-down command speed is calculated in consideration of the speed reduction that decreases between the shift-down command and the completion of the shift-down, so that the shift shock is reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a view for explaining hydraulic drive of a wheel hydraulic excavator according to an embodiment.

FIG. 2 is a block diagram illustrating details of a transmission.

FIG. 3 is a flowchart illustrating an example of a shift control.

FIG. 4 is a diagram illustrating a traveling performance curve.

[Explanation of symbols]

10: Variable displacement hydraulic pump 21: Vehicle speed sensor 22: F / V converter 23: Controller 31: Travel hydraulic motor 44: Transmission 44d: High side clutch 44f: Low side clutch 71: Electromagnetic switching valve 72: Hydraulic pilot switching valve

Claims (4)

[Claims] 1. A continuously variable transmission hydraulic drive including a variable displacement hydraulic pump and a variable displacement hydraulic motor, and a transmission for shifting the output of the continuously variable transmission hydraulic drive in at least two stages, wherein A transmission that requires a predetermined time to complete a downshift; vehicle speed detection means for detecting the speed of the vehicle; deceleration determination means for determining that the vehicle is decelerating; and a speed reduction of the vehicle that falls within the predetermined time Speed reduction amount calculating means for calculating the amount; and a downshift instruction speed for shifting down the transmission based on the speed reduction amount calculated by the speed reduction amount calculating means and a preset reference speed. Calculating means for calculating the vehicle speed; when deceleration is determined by the deceleration determining means, when the vehicle speed detected by the vehicle speed detecting means reaches the downshift instruction speed. Wheel traveling working vehicle, characterized in that it comprises a shift instruction means for outputting the serial shift down command. 2. The wheel traveling type work vehicle according to claim 1, wherein the shift instructing means is configured to, when the vehicle speed detected by the vehicle speed detecting means becomes a shift-up instructing vehicle speed after the completion of the downshift, change the transmission. A wheel traveling type work vehicle, which outputs an upshift command to a vehicle. 3. The wheel traveling type work vehicle according to claim 1, wherein the reference speed is a predetermined number of revolutions of the hydraulic motor when the transmission is switched from a high speed stage to a low speed stage. A wheel traveling type work vehicle characterized by being set so as not to exceed a maximum rotation speed. 4. The wheel traveling type work vehicle according to claim 1, wherein the shift instructing means calculates the downshift instruction speed by adding the speed reduction amount and the reference speed. A wheeled work vehicle characterized by: