JPH06104460B2 - Hydraulically driven vehicle direction correction device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulically driven vehicle that travels by a hydraulic motor connected to a variable displacement hydraulic pump by a closed circuit, and a hydraulically driven vehicle that corrects its traveling direction. The present invention relates to a direction correcting device.

[Conventional technology]

Examples of hydraulically driven vehicles that are driven by a hydraulic motor include a hydraulic shovel equipped with crawlers and a hydraulic crane. Among such hydraulically driven vehicles, a hydraulic shovel will be described with reference to the drawings.

FIG. 4 is a side view of the schematic configuration of the hydraulic shovel. In the figure, 1 is a lower traveling structure, 2 is an upper revolving structure, and 3 is a front mechanism. The front mechanism 3 is composed of a boom 4, an arm 5 and a bucket 6. 7'is the undercarriage 1
The crawler 8'is mounted on the vehicle, and 8'is a hydraulic motor for traveling. The illustrated crawler 7'and hydraulic motor 8'are the right crawler and hydraulic motor, and the same crawler 7 and hydraulic motor 8 are also provided on the left 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 a drive circuit for the left hydraulic motor 8,
R is a drive circuit for the hydraulic motor 8'on the right side. Since the left and right drive circuits L and R have the same configuration, hereinafter, in the drive circuit R on the right side, the same parts as those in the drive circuit L on the left side are denoted by the same reference numerals and the 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 by the main pipelines A and B to form a hydraulic closed circuit. Reference numeral 11 is an operating lever for traveling, and 12 is a regurator for driving a variable displacement mechanism (for example, a swash plate) of the hydraulic pump 10 according to the operation of the operating lever 11. Reference numeral 13 is a flushing valve connected between the main pipes A and B, and connects the low-pressure main pipe to the tank. Reference numeral 14 is a flushing relief valve interposed between the flushing valves 13 and 13 'and the tank. Reference numeral 15 is a charge pump that supplies pressure oil to the hydraulic circuit, and 16 is a charge relief valve that regulates the maximum discharge pressure of the charge pump 15. The setting pressure of the charge relief valve 16 is the flushing relief valve 14
It is selected to be higher than the set pressure of. Reference numeral 17 is a check valve for supplying the pressure oil of the charge pump 15 to the main pipelines A and B.

Next, the operation of the drive circuits L and R will be described.

(1) When moving the hydraulic shovel straight on a flat ground or on a slope (when the load of the hydraulic motors 8 and 8'is positive and rotates them in the direction of the arrow in the figure) In this case, the operating levers 11 and 11 ' In the same manner, hydraulic oil is supplied from the hydraulic pumps 10 and 10 'to the main pipelines A and A', and the hydraulic motors 8 and 8'rotate in the arrow directions. At this time, since the pressure on the main pipelines A, A'side is higher than the pressure on the main pipelines B, B'side, the flushing valves 13, 13 'are set at positions II shown in the figure.
To position I and the main lines B, B'are connected to the tank via a flushing relief valve 14. On the other hand, the setting pressure of the charge relief valve 16 is the flushing relief valve.
Since it is higher than the set pressure of 14, the pressure oil of the charge pump 15 is supplied to the main pipelines B, B'through the check valves 17, 17 '. Therefore, a quantity of pressure oil equal to the flow rate of the supplied pressure oil flows out to the tank through the flushing valves 13 and 13 'and the flushing relief valve 14, whereby the hydraulic fluid in the hydraulic closed circuit is replaced. . In such a state, the straight movement of the hydraulic shovel continues.

(2) When braking or downhilling the hydraulic shovel (when the load on the hydraulic motors 8 and 8'is negative) To control the hydraulic shovel while traveling, the operating lever
When 11, 11 'is returned to the neutral position direction, the hydraulic motors 8, 8'perform a pump action by its inertial force, suck the pressure of the main pipelines A, A', and discharge them to the main pipelines B, B '. . Because of this, the main pipeline
The B and B'sides become high in pressure, and the hydraulic pumps 10 and 10 'act as motors to bring the engine into a braking state and apply braking. Due to the high pressure on the main pipe lines B, B'side, the flushing valves 13, 13 'are switched from the position I to the position III, the main pipe lines A, A'are connected to the tank, and the operation similar to the above (1) is performed. The hydraulic oil is replaced. The same operation is performed at the time of descending the plate.

(3) When the hydraulic shovel is curved from straight-ahead straight traveling Let us consider a case where the hydraulic shovel that is traveling straight ahead is curved rightward. In this case, of the operation levers 11 and 11 'which have been the same operation amount until now, only the operation lever 11' is slightly returned to the neutral position direction. As a result, the amount of pressure oil supplied from the hydraulic pump 10 'to the main line A'is reduced, and the speed of the hydraulic motor 8'is also reduced. In this state, the drive circuit L on the left side is in the same state as in (1) above, and the drive circuit R on the right side is in the same state as in (2) above, and the right crawler 7'is dragged by the left crawler 7 and the hydraulic shovel is Turn right. The left turn is also the same.

[Problems to be Solved by the Invention]

The operation of each drive circuit L, R when the hydraulic shovel is traveling straight or curved has been described above. Now, consider a case where the hydraulic shovel travels straight again from a curved state. When shifting from rightward curving to straight traveling, the operation amount of the operation lever 11 ′ is the same as that of the operation lever 11 when the operation lever 11 ′ is returned to the neutral direction, and the discharge amount of the hydraulic pump 10 ′ is equal to the discharge amount of the hydraulic pump 10. To increase the rotation of the hydraulic motor 8 '. At this time, the pressure in the main line A'becomes higher than the pressure in the main line B ', and the flushing valve 13' is switched from position III to position I.

However, the switching of the flushing valve 13 may not be performed smoothly depending on the difference in efficiency between the hydraulic pump and the hydraulic motor or the way of operation. That is, when shifting from the above-mentioned rightward curving to straight traveling, the flashing valve 13 'does not switch to the position I but remains at the position III. For this reason, the main pipe line A ′ remains connected to the tank,
The pressure oil discharged from the hydraulic pump 10 'is not supplied to the hydraulic motor 8', but flows through the flushing valve 13 'and the flushing relief valve 14 into the tank. For this reason, the hydraulic shovel may further turn to the right even though the straight traveling operation is performed. Such a situation is a phenomenon that occurs even immediately after the hydraulic shovel is started.

Conventionally, in order to prevent the occurrence of such a situation, the spring of the flat sink valve 13 is set to be stronger, or between the main pipelines A and A ′,
A means for connecting the main pipelines B and B'through a throttle was used. However, since the means for strengthening the spring of the flushing valve 13 is inevitably limited, a sufficient effect cannot be obtained, and there is a drawback that a new pipeline must be added to the communication between the left and right main pipelines. I got it.

An object of the present invention is to provide a direction correcting device for a hydraulically driven vehicle that can smoothly perform the transition from curved traveling to straight traveling, excluding the above-mentioned drawbacks of the prior art.

[Means for Solving the Problems]

In order to achieve the above object, the present invention respectively relates to a fusible displacement hydraulic pump, a traveling hydraulic motor connected to the variable displacement hydraulic pump by a main circuit, and the main circuit and a low pressure circuit on the tank side. In a hydraulically driven vehicle having a first hydraulic closed circuit and a second hydraulic closed circuit having a flushing valve for conducting and shutting off, each detecting means for detecting a value related to driving of each hydraulic motor, and the hydraulic pressure. Judgment means for judging the equilibrium state of the drive of each hydraulic motor based on the detection value of each detection means when the traveling instruction device of the drive vehicle directs straight, and the drive of each hydraulic motor is balanced by this judgment means. When it is determined that the hydraulic motor is not normally driven based on the detection value of the detection means when it is determined that the main circuit and the flushing valve of the hydraulic closed circuit Characterized by providing a blocking means for blocking the connection between the low-pressure circuit.

[Action]

When the traveling of the hydraulically driven vehicle is changed from the curved traveling to the straight traveling, the determining means determines whether the drive of each hydraulic motor is in the equilibrium state. This determination is made based on the detection value of the detection means.For example, when the pressure of the discharge side pipeline of the pressure oil in the hydraulic closed circuit is lower than the pressure of the suction side pipeline, or the rotation speed of one hydraulic motor is different from that of the other hydraulic motor. When it is lower than the rotation speed, it is determined that the driving of each hydraulic motor is not in a balanced state. In this way, when it is determined that the pressure is not in the equilibrium state, the pressure in the discharge side pipeline is lower than the pressure in the suction side pipeline, or through the flushing valve and the main circuit of the hydraulic closed circuit on the side where the rotation speed is low. The connection with the low-voltage circuit is cut off by the cut-off means, and the cut-off is released when the detection means detects that the drive of each hydraulic motor is in a balanced state.

〔Example〕

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

FIG. 1 is a system diagram of a hydraulic shovel direction correcting device according to a first embodiment of the present invention. In the figure, the same parts as those shown in FIG. 19,1
Reference numeral 9'denotes a left and right traveling operation lever, which outputs an electric signal proportional to the operation direction and operation amount. 20a, 20b,
20a ', 20b' are pressure detectors, respectively, and are connected to the main pipelines A, B,
The pressure of A'and B'is detected and a signal proportional to it is output. 21 is an operating lever 19, 19 ', pressure detectors 20a, 20b, 20
This is a control device that inputs signals a ', 20b' and executes predetermined calculation and control based on these signals. Reference numerals 22, 22 'are electromagnetic switching valves operated by an output signal from the control device 21. This electromagnetic switching valve 22, 22 'is a flushing valve 13, 1
It is interposed in the pilot conduit of 3 ', and normally the pilot conduits at both ends of the flushing valves 13 and 13' are kept in a conducting state, but the pilot conduit is switched off by the output signal from the control device 21. And connect the pilot chambers at both ends.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG. When traveling straight or traveling in a curve,
The control device 21 inputs signals from the operating levers 19 and 19 ', and drives the regu-lators 12 and 12' in response thereto. Therefore, the operation of the drive circuits L and R is exactly the same as the above-mentioned operations (1) to (3). Next, the operation when shifting from curved traveling to straight traveling will be described. First, the control device
21 receives the signals from the operating levers 19 and 19 'and determines whether or not these operating levers 19 and 19' are in the straight-ahead range, that is, whether the operating levers 19 and 19 'are in substantially the same operation amount. or the judges (Step S _1). Since the above-mentioned drawback occurs when the hydraulic shovel moves from the curved state to the straight state, it is determined in step S ₁ that the hydraulic shovel is going straight. Next, the control device 21 controls the pressure detectors 20a, 20
Input the signals b, 20a ', 20b' and compare the discharge side pressure and the absorption side pressure of the hydraulic pumps 10 and 10'.Only one of the hydraulic pumps has a discharge side pressure lower than the absorption side pressure. and it determines whether that (Step S _2). If the answer is NO, it is determined that the vehicle is traveling straight ahead without any problems.
Performs an operation of the state of the illustrated 2 '(Step S _5), the processing of again in Step S _1, S ₂ is repeated. If it is determined that one of the hydraulic pumps has a discharge pressure lower than the absorption pressure, that is, the flushing valve does not switch smoothly, and the pressure oil of the hydraulic pump passes through the flushing valve to the tank. If the discharge side pressure is lower than the absorption side pressure, the electromagnetic switching valve of the hydraulic closed circuit is switched. Thus, is connected across the pilot chamber to each other in Furatsushingu valve, Furatsushingu valve is switched to force the neutral position II from position III (Step S _3). For this reason, the discharge side of the hydraulic pump, which has been connected to the low pressure circuit on the tank side through the flushing valve until then, is disconnected from the low pressure circuit, and the pressure oil of the hydraulic pump is changed to the hydraulic motor. Is supplied to. By this control, the pressure on the discharge side increases.

Here, the control device 21 compares the discharge side pressure with the absorption side pressure and determines whether or not the discharge side pressure has become equal to or higher than the absorption side pressure (step S ₄ ). If not, again it repeats the processing of steps S ₁ to S _3. Eventually, when the discharge pressure is determined to has decreased to or absorption-side pressure in step S _4, the controller 21 returns to the original electromagnetic switching valve, is conducting pilot line of the flushing valve, normally operable to Furatsushingu valve and a state (Step S _5). After that, the hydraulic shovel runs straight at a speed corresponding to the operation amount of the operating levers 19 and 19 ', and the flushing valve is switched to the position I.

As described above, in the present embodiment, when one of the hydraulic closed circuits is not operating normally at the time of transition from curving to straight traveling, it is detected and one of the hydraulic closed circuits that is not operating normally is detected. Since the flushing valve is forcibly set to the neutral position and the main line and the low-pressure circuit on the tank side via the flushing valve are temporarily shut off so that the operation of the hydraulic closed circuit can be restored normally, without providing a separate pipe, It is possible to smoothly shift from curving to straight traveling.

FIG. 3 is a system diagram of a hydraulic shovel direction correcting device according to a second embodiment of the present invention. In the figure, the same parts as those shown in FIG. 23,2
Reference numeral 3'denotes a rotation speed detector for detecting the rotation speeds of the hydraulic motors 8 and 8 ', respectively. This embodiment differs from the first embodiment in that
In the first embodiment, two pressure detectors are used to detect an abnormal operation of the hydraulic circuit on one side when the hydraulic shovel moves from the curved movement to the straight movement. Only the point using one rotation speed detector is used, and the other points are the same.

When the hydraulic shovel moves from curving to straight traveling, the flushing valve is not switched. Therefore, unless the hydraulic pressure from the hydraulic pump is supplied to the hydraulic motor, the rotational speed of the hydraulic motor decreases. This embodiment utilizes this phenomenon to detect an abnormal operation of the hydraulic closed circuit. Control device
In 21, the detection signals of the rotation speed detectors 23, 23 'are taken in,
By comparing these, the judgment in step S ₂ shown in the previous example is made. Further, the determination in step S ₄ is based on whether or not the rotation speed on the low rotation speed side has increased. The other operations of the control device 21 are the same. This embodiment also has the same effect as the first embodiment.

In the above description, the hydraulic shovel is illustrated as an example of the hydraulically driven vehicle, but the hydraulic shovel is not limited to the hydraulic shovel, and can naturally be applied to other hydraulically driven vehicles. Further, in the description of the above-mentioned embodiment, the example in which the electromagnetic switching valve forcibly returns the flushing valve to the neutral position has been described, but the present invention is not limited to this, and the conduit from the main circuit connected to the flushing valve may be used. Of course, it may be blocked. Further, the main line and the low-pressure circuit on the tank side via the flushing valve may be disconnected not by only one hydraulic closed circuit but by both hydraulic closed circuits.

〔The invention's effect〕

As described above, in the present invention, when one of the hydraulic closed circuits is not operating normally at the time of the transition of the hydraulically driven vehicle from curving to straight traveling, this is detected, and the hydraulic closed circuit or both of them are detected. Since the main circuit of the hydraulic closed circuit and the low-pressure circuit on the tank side via the flushing valve are cut off, it is possible to smoothly perform the transition from curved travel to straight travel without providing additional piping.

[Brief description of drawings]

FIG. 1 is a system diagram of a direction correcting device for a hydraulic shovel according to a first embodiment of the present invention, FIG. 2 is a flow chart for explaining the operation of the device shown in FIG. 1, and FIG. FIG. 4 is a system diagram of a hydraulic shovel direction correcting device according to a second embodiment.
FIG. 5 is a side view of the schematic configuration of the hydraulic shovel, and FIG. 5 is a circuit diagram of a hydraulic closed circuit for driving the hydraulic motor shown in FIG. 8,8 ′ …… hydraulic motor, 10,10 ′ …… hydraulic pump, 12,1
2 ′ …… Regulator, 13,13 ′ …… Flatsing valve, 1
9,19 '... Operating lever, 20a, 20b, 20a', 20b '... Pressure detector, 21 ... Control device, 22,22' ... Solenoid switching valve, 23,
23 '... Rotation speed detector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-100020 (JP, A) JP-A-57-147963 (JP, A) JP-A-51-50132 (JP, A) JP-B-59- 11462 (JP, B2) Actual public Sho 57-32024 (JP, Y2)

Claims (4)

[Claims] 1. A variable displacement hydraulic pump, a traveling hydraulic motor connected to the variable displacement hydraulic pump by a main circuit, and a flushing valve for connecting and disconnecting the main circuit and a low pressure circuit on the tank side, respectively. In a hydraulically driven vehicle having the first hydraulically closed circuit and the second hydraulically closed circuit, each detection means for detecting a value related to the drive of each of the hydraulic motors, and a travel instruction device for the hydraulically driven vehicle go straight ahead. And a determination unit that determines the balanced state of the drive of each hydraulic motor based on the detection value of each detection unit, and when the determination unit determines that the drive of each hydraulic motor is not in the balanced state. A connection between the main circuit of the hydraulic closed circuit on the side where the hydraulic motor is determined not to be normally driven based on the detection value of the detection means and the low pressure circuit via the flushing valve. Hydraulic drive vehicle direction adjustment device also provided with a blocking means for blocking. 2. The pressure detecting device according to claim 1, wherein the detecting means detects the circuit pressures of the circuits on both sides of the first hydraulic closed circuit and the second hydraulic closed circuit, respectively. A direction correcting device for a hydraulically driven vehicle, which is characterized in that 3. The direction correcting device for a hydraulically driven vehicle according to claim 1, wherein the detecting means is a rotation speed detector for detecting the rotation speed of each of the hydraulic motors. 4. The direction correcting device for a hydraulically driven vehicle according to claim 1, wherein the shut-off means is a flushing valve returning means for returning the flushing valve to a neutral position.