JPS6259170A - Direction correcting device for hydraulic drive vehicle - Google Patents

Abstract

PURPOSE:To smoothly shift a hydraulic drive vehicle from turning travelling to straight travelling by reducing the discharge of one hyraulic pump to return the operation of one hydraulic circuit to the normal one when the other of hydraulically closed circuit is not normally operated. CONSTITUTION:A hydraulic drive vehicle is provided respectively with variable capacity pumps 10, 10', travelling hydraulic motors 8, 8' driven by these pumps 10, 10' and first and second hydraulically closed circcuits having flushing valves 13, 13'. In the above constitution, when the hydraulic drive vehicle is shifted from turning travelling to straight one, signals from operating levers 19, 19' are sent to the input to a control device 21 and the straight travelling condition, i.e. whether or not the operating amounts of said levers are equal to each other is judged. Next, signals of pressure detectors 20a, 20b, 20a', 20b' are sent to the input of the control device 21 to compare the discharge side pressure with the absorbing side one of hydraulic pumps 10, 10'. And when one of hydraulically closed circuits is not normally operated, the slant rotation of the other hydraulic pump is reduced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a hydraulically driven vehicle which is driven by a hydraulic motor connected to a variable displacement hydraulic pump through a closed circuit, and which corrects the running direction of the hydraulically driven vehicle. Relating to a correction device.

[Background of the invention]

Hydraulically driven vehicles that run using hydraulic motors include, for example, hydraulic excavators equipped with crawlers, hydraulic cranes, and the like. Among hydraulically driven vehicles, a hydraulic excavator will be explained using a diagram.

FIG. 4 is a side view of the schematic configuration of the hydraulic excavator. In the figure, 1 is a lower traveling body, 2 is an upper rotating body, and 3 is a front □ mechanism. The front mechanism 3 is composed of a poom 4, an arm 5, and a packet 6. 7' is lower running body 1
8' is a hydraulic motor for traveling. The illustrated crawler 7' and hydraulic motor 8' are the right-hand crawler and hydraulic motor, and the same crawler 7 and hydraulic motor 8 are also provided on the left-hand side.

FIG. 5 is a circuit diagram of a hydraulic closed circuit that drives the left and right hydraulic motors. In the figure, L is the drive circuit for the left hydraulic motor 8;
R is a drive circuit for the right hydraulic motor 8'. Since the left and right drive circuits R have the same configuration, hereinafter, the same parts in the right drive circuit R as those in the left drive circuit will be denoted by the same reference numerals with a dash, and a description thereof will be omitted. Reference numeral 10 denotes a variable displacement hydraulic pump (hereinafter simply referred to as a hydraulic pump), which is connected to the hydraulic motor 8 through main lines A and B, forming a hydraulic closed circuit. Reference numeral 11 denotes a driving operation lever, and 12 a regulator that drives a variable displacement mechanism (for example, a swash plate) of the hydraulic pump 10 in accordance with the operation of the operation lever 11.

13 is a flushing valve connected between main pipes A and B, and connects the main pipe on the low pressure side to the tank.

14 is a relief valve located between the flushing valves 13 and 13' and the tank. 15 is a charge pump that supplies pressure oil to the hydraulic closed circuit, and 16 is a charge relief valve that defines the maximum value of the discharge pressure of the charge pump 15. The set pressure of the charge relief valve 16 is selected to be higher than the set pressure of the flushing relief valve 14.

A check valve 17 supplies pressure oil from the charge pump 15 to the main pipes A and B.

Next, the operation of the drive circuit H will be explained.

(1) When moving the hydraulic shovel straight on flat ground or on a slope (when the load on the hydraulic motors 8, 8' is positive and the motors are rotated in the direction of the arrow in the figure), in this case, the operation lever 11.11 ' is operated in the same way, and from the hydraulic pump 10.10' the main pipes A, A'
Pressure oil is supplied to the hydraulic motors 8, 8' to rotate in the direction of the arrow. At this time, the pressure on the main pipe A, A' side is
, the pressure on the B' side also increases, so the flushing valve 1
3.13' is switched from the illustrated position ■ to position I, and the main lines B and B' are connected to the tank via the flushing relief valve 14.

On the other hand, since the set pressure of the charge relief valve 16 is higher than the set pressure of the seven latching relief valves 14, the pressure oil of the charge pump 15 is supplied to the main pipes B and B' via the check valves 17 and 17'. Therefore, an amount of pressure oil equal to the flow rate of this supplied pressure oil is supplied to the 7 latching valves 13.13.
' and 7 through the flush/relief valve 14 to the tank, thereby replacing the hydraulic fluid in the closed hydraulic circuit. In this state, the hydraulic excavator continues to move straight.

(2) When applying braking to or dismounting the hydraulic excavator (
(When the load on the hydraulic motor 8.8' becomes negative) In order to apply braking to the running hydraulic excavator, the operating levers 11', 1
1' is returned to the neutral position, the hydraulic motor 8.8' performs a pumping action by its inertial force, sucks pressure oil from the main pipes A and A', and transfers it to the main pipe B.

It is discharged to B'. Therefore, while the main pipes B and B' are at high pressure, the hydraulic valves 10 and 10' operate as motors, resulting in an engine braking state and applying braking. Due to high pressure on the main pipes B and B' sides, flushing valve 1
3.13' is switched from position ■ to position ■, and main pipe A
, A' are connected to the tank, and the hydraulic oil is replaced by the same operation as in (1) above. A similar operation is performed when exiting the board.

(3) When a hydraulic excavator is caused to turn from a straight lead on flat ground to a curved line Now, consider the case where a hydraulic excavator that is traveling straight is caused to turn to the right. In this case, only the operating lever 11' of the operating levers 11, 11', which have been operated with the same amount until now, is slightly returned toward the neutral position.

As a result of this K, the amount of pressure oil supplied from the hydraulic pump 10' to the main pipe A' decreases, and the speed of the hydraulic motor 8' also decreases. In this state, the left drive circuit is in the same state as +1) above, the right drive circuit R is in the same state as in (2) above, and the hydraulic excavator is moved to the right while the right crawler 7' is dragged by the left crawler 7. turn in the direction The same applies to turning to the left.

The above is a description of each drive circuit when the hydraulic excavator moves straight through one curve, H
I described the operation of . Now, let us consider a case where the hydraulic excavator starts traveling straight again from a curved state. When transitioning from rightward turning to straight driving, press the operating lever 11'
is the same amount of operation as the operation lever 11 from the state returned to the neutral direction, and the discharge amount of the hydraulic pump 10' is changed to
, and the rotation of the hydraulic motor 8' is increased.

At this time, the pressure in the main pipe A' becomes higher than the pressure in the main pipe B', and the flushing valve 13' is switched from the position (2) to the position (2).

However, if there is a difference in efficiency between the hydraulic pump and the hydraulic motor, or depending on the operating method, the switching of the seven lash/g valve 13 may not be performed smoothly.

In other words, when shifting from the above-mentioned right turn to straight-ahead driving,
The flushing valve 13' is not switched to position I, but remains at position (3). Therefore, the main pipe A' remains connected to the tank, and the pressure oil discharged from the hydraulic pump 10' is not supplied to the hydraulic motor 8', but instead passes through the flushing valve 13' and the flood/relief valve 14. flushed into the tank. For this reason, a situation occurs in which the hydraulic excavator curves further to the right even though the operator performs an operation to travel straight. Such a situation is a phenomenon that can be observed even immediately after the hydraulic excavator starts.

Conventionally, in order to prevent such five situations from occurring, the spring of the 7 lashing valve 13 was set to be strong, or the main pipes A, A
Means was used to communicate between the main pipes B and B through a choke. However, 7 lash/g valve 13
The means for strengthening the springs inevitably have limitations and cannot be sufficiently effective, and there is also the drawback that a new pipe must be added to communicate between the left and right main pipes.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a direction correction device for a hydraulically driven vehicle that eliminates the drawbacks of the prior art described above and can smoothly transition from curved driving to straight driving.

[Summary of the invention]

In order to achieve the above object, the present invention provides a hydraulically driven vehicle having two hydraulic closed circuits each including a variable displacement hydraulic pump, a hydraulic motor for traveling, and a flushing valve. Detect values related to the drive of the hydraulic motor, such as the pressure in the circuits on both sides of the hydraulic motor or the number of revolutions of the hydraulic motor, and when the instruction from the control lever etc. is to go straight, both hydraulic motors are activated based on the detected values. It is determined whether or not they are being driven in approximately the same way, and if it is determined that the drive of both hydraulic motors is in an unbalanced state as a result of this determination, the pressure on the discharge side of both displacement hydraulic pumps is The higher variable displacement hydraulic pump, or the variable displacement hydraulic pump connected to the hydraulic motor with a higher rotation speed of both hydraulic motors, that is, the variable displacement hydraulic pump on the side where the hydraulic motor is normally driven, It is characterized in that the discharge amount is controlled to decrease.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a system diagram of a direction correction device for a hydraulic excavator according to a first embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 5 are given the same reference numerals, and explanations thereof will be omitted. 19
．． Reference numeral 19' denotes a control lever for left and right travel, which outputs an electric signal proportional to the direction and amount of operation. 20
a, 20b, 20a'.

20 b' are pressure detectors, and the main pipe A.

Detects the pressures of B, A', and B' and outputs a signal proportional to them. 21 inputs the signals of the operating lever 19, 19', pressure detector zoa, 20b, 20&', 20b',
This is a control device that executes predetermined calculations and control based on these signals.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG. When driving straight and when driving around curves,
The control device 21 receives signals from the operating levers 19 and 19' and drives the regulators 12 and 12' accordingly.

Therefore, the drive circuit.

The operation of R is exactly the same as the operations (1) to (3) described above. Next, an explanation will be given of the operation when the vehicle shifts from curved driving to straight driving. First, the control device 21 inputs signals from the operating levers 19.19' and determines whether these operating levers 19.19' are in the straight-ahead range, that is, the operating levers 19.19' have approximately the same operating amount. (Step S). The above-mentioned drawback occurs when the hydraulic excavator shifts from a curved state to a straight state, so it costs $8. Now it is determined that the hydraulic excavator is trying to move straight. Next, the control device 21 controls the pressure detector 2
Input the signals 0a*20b, 20a'*20b',
The discharge side pressure and absorption side pressure of the hydraulic pumps 10 and 10' are compared, and it is determined whether or not the discharge side pressure of only one of the hydraulic pumps is lower than the absorption side pressure (step S). If not, it is determined that the vehicle is traveling straight ahead without any problem, and the steps St-Ss are repeated. if,
If it is determined that the discharge side pressure of one of the hydraulic pumps is lower than the absorption side pressure, that is, the flushing valve does not switch smoothly, and the pressure oil of the hydraulic pump flows into the tank via the 7 lashing valve. If it is flowing, reduce the tilting of the variable displacement mechanism of the hydraulic pump whose discharge side pressure is higher than the absorption side pressure (hydraulic pump in the normally operating drive circuit) (manual JIS). Through this control, the amount of pressure oil supplied to the normally driven hydraulic motor is reduced, the rotational speed of the hydraulic motor is reduced, and the driving speed of the hydraulic excavator is also reduced. Therefore, the outlet pressure of the hydraulic motor that is not normally driven also decreases. The control device 21 takes in the pressure of the drive circuit that is not performing tilting control (the drive circuit that is not operating normally), compares the discharge side pressure with the absorption side pressure, and determines whether the discharge side pressure is the absorption side pressure. It is determined whether the side pressure has exceeded the side pressure (step S4).

If not, the process returns to step S and the discharge amount of the normally driven hydraulic pump is reduced. By repeating steps S and S, eventually when it is determined by hand @S that the pressure on the discharge side has become higher than the pressure on the absorption side, that is, the flushing valve is at the position! When it is determined that the hydraulic pump is in a normal state where pressure oil is supplied to the hydraulic motor, the tilting of the hydraulic pump, which was lowered in step S, is changed according to the amount of operation of the operating lever. to the original value (step S, ). Thereafter, the hydraulic excavator travels straight at a speed corresponding to the amount of operation of the operating lever 19, 19'.

In this way, in this embodiment, when one side of the hydraulic closed circuit is not operating normally when transitioning from curved driving to straight driving, this is detected, and the tilting of the other hydraulic pump is reduced to perform the above-mentioned operation. Since the operation of one of the hydraulic closed circuits is restored to normal, it is possible to smoothly transition from curved driving to straight driving without providing additional piping.

FIG. 3 is a system diagram of a direction correction device for a hydraulic excavator according to a second embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 22.
Reference numerals 22' denote rotation speed detectors for detecting the rotation speed of the hydraulic motors 8 and 8', respectively.

The difference between this embodiment and the first embodiment is that the first embodiment is
While two pressure detectors were used to detect abnormal operation of any hydraulic circuit when the hydraulic excavator transitions from curved to straight travel, this embodiment uses one rotation speed detector. Only the points used are the same; the other points are the same.

When the hydraulic excavator transitions from curved travel to straight travel, the brushing valve does not switch, and therefore, if pressure oil from the hydraulic pump is not supplied to the hydraulic motor, the rotational speed of the hydraulic motor decreases. In this embodiment, this phenomenon is utilized to detect abnormal operation of the hydraulic closed circuit. The control device 21 takes in the detection signals of the rotation speed detectors 22, 22' and compares them to make the determination in step S shown in the previous embodiment. Further, the determination in step S4 is based on whether or not the rotational speed on the lower rotational speed side has increased. The other operations of the control device [21 are the same. This embodiment also has the same effects as the first embodiment.

9. In the first and second embodiments, in the hydraulic closed circuit on the normally driven side, control is executed to reduce the tilting of the hydraulic pump by looking at the command of the operating lever. As a result, there will be a slight change in running speed.

Therefore, when operating the vehicle, it is only necessary to ensure smooth running with appropriate acceleration/deceleration. Also, until now,
Although the explanation was given using a hydraulic excavator as an example of a hydraulically driven vehicle,
It goes without saying that the present invention is not limited to hydraulic excavators, but can also be applied to other hydraulically driven vehicles.

〔Effect of the invention〕

As stated above, in the present invention, when one of the hydraulic closed circuits is not operating normally when a hydraulically driven vehicle transitions from turning to straight traveling, this is detected and the discharge amount of the other hydraulic pump is Since the operation of one of the above-mentioned hydraulic closed circuits is restored to normal by reducing the
A smooth transition from curved driving to straight driving can be achieved.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a direction correction device for a hydraulic excavator according to a first embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the device shown in FIG. 1, and FIG. 4th system diagram of the direction correction device for a hydraulic excavator according to the embodiment of
The figure is a side view of the schematic configuration of the hydraulic excavator, and FIG. 5 is a circuit diagram of a hydraulic closed circuit that drives the hydraulic motor shown in FIG. 4. 8.8'...Hydraulic motor, 10.10'...
...Hydraulic pump 7', 12.12'...Regulator, 13, 13'...Fujitsu sink valve, 1
9.19'...Operation rate p<-120a. 20b, 20a', 20b'...pressure detector,
21...Control device, 22.22'...
Rotation speed detector. Figure 4

Claims (1)

[Claims] 1. A first hydraulic closed circuit and a second hydraulic closed circuit each having a variable displacement hydraulic pump, a traveling hydraulic motor driven by the variable displacement hydraulic pump, and a flushing valve. In a hydraulically driven vehicle, each detecting means detects a value related to the drive of each of the hydraulic motors, and when the traveling instruction device of the hydraulically driven vehicle instructs to go straight, the detecting means detects the value based on the value detected by each of the detecting means. determining means for determining whether the driving of each hydraulic motor is in a balanced state; and when the determining means determines that the driving of each of the hydraulic motors is not in a balanced state, the variable displacement hydraulic pump on the side where the hydraulic motor is normally driven; A direction correction device for a hydraulically driven vehicle, comprising a discharge amount control means for reducing a discharge amount of the hydraulically driven vehicle. 2. In claim 1, the detection means:
A direction correction device for a hydraulically driven vehicle, characterized in that the device is a pressure detector that detects circuit pressures of circuits on both sides of the first hydraulic closed circuit and the second hydraulic closed circuit. 3. In claim 1, the detection means:
A direction correction device for a hydraulically driven vehicle, characterized in that it is a rotation speed detector that detects the rotation speed of each of the hydraulic motors.