JP2543146Y2 - Hydraulic circuit of traveling hydraulic motor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for preventing cavitation of a traveling hydraulic motor in a hydraulic traveling vehicle.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional hydraulic circuit of a traveling hydraulic motor in a hydraulic traveling work vehicle such as a wheel hydraulic excavator.

This hydraulic circuit is an aggregate of hydraulic pumps 1A and 1B for driving various actuators of a work vehicle and control valves for controlling the supply of pressure oil from the hydraulic pumps 1A and 1B for each actuator. It comprises a multiple control valve 2A, 2B and a traveling hydraulic motor 4 driven and controlled by traveling control valves 3a, 3b of the multiple control valve 2A, 2B. An overflow relief valve 6, a counter balance valve 7, and a make-up valve 8 are connected. Further, makeup valve 8 and oil tank 10 are connected to external makeup circuit 12.
The oil cooler 11 is provided in the return oil line of the control valve 2A. In addition, CJ
Is a center joint that circulates oil between the upper and lower revolving superstructures.

In the above configuration, when the control valves 3a, 3b are operated to the "A" position, the oil of the hydraulic pumps 1A, 1B exits the respective control valves and joins, and the pressures thereof cause the "A" position. Is supplied to the traveling hydraulic motor 4 from the main pipeline 5A through the counter balance valve 7 which is switched to, and drives the traveling hydraulic motor 4.
On the other hand, return oil from the traveling hydraulic motor 4 is supplied to the main pipeline 5B.
The return oil is returned to the oil tank 10 via the oil cooler 11 or directly through the counter balance valve 7 and the control valves 3a and 3b which have been switched to the position "a". Thus, the traveling hydraulic motor 4
Rotates forward, and the work vehicle moves forward. In the case of reverse travel, the reverse operation is performed.

If the amount of oil supplied to the traveling hydraulic motor 4 is reduced by operating the control valves 3a and 3b in order to decelerate the running vehicle, the pressure in the main pipeline 5A decreases,
The counter balance valve 7 returns to the neutral position by its spring force, and completely closes the circuit of the traveling motor 4. In this state, the traveling hydraulic motor 4 attempts to continue rotation due to the inertia during traveling, so a high brake pressure is generated in the main pipeline 5B, and the traveling hydraulic motor 4 is decelerated. The vehicle stops.

When the vehicle descends on a slope, the traveling hydraulic motor 4 is rotated by an external force, and the amount of oil supplied from the hydraulic pumps 1A and 1B becomes insufficient. As a result, the circuit of the traveling hydraulic motor 4 is fully closed by the counterbalance valve 7 as in the case of deceleration, and the brake hydraulic pressure is applied to the main pipeline 5B to decelerate the traveling hydraulic motor 4 as in the case of deceleration. I do. When the shortage of the supplied oil amount is resolved by this deceleration, the pressure in the main pipeline 5A increases again, the counter balance valve 7 is switched to the position "A", and the traveling hydraulic motor 4 continues to rotate. By repetition of such an operation, runaway at the time of descending a slope is prevented.

Here, when the counterbalance valve 7 is closed and the traveling hydraulic motor 4 is decelerated during deceleration and descent, when cavitation occurs in the traveling hydraulic motor 4, the life of the traveling hydraulic motor 4 is reduced and the cause of abnormal noise is caused. Becomes

The make-up valve 8 and the external make-up circuit 12 are provided to prevent this. When a pressure drop occurs in the main line 5A, oil is supplied from the oil tank 10 to the external make-up circuit 12, the make-up valve 8 and the like. Through the main conduit 5A to compensate for the lack of oil and to prevent the occurrence of cavitation.

However, in recent years, the weight of the vehicle has increased and its speed has tended to increase, and the amount of oil shortage at the entrance of the traveling hydraulic motor 4 at the time of deceleration or downhill is increasing. As a result, the shortage of oil from the oil tank 10 by the external make-up circuit 12 and the make-up valve 8 alone cannot compensate for the insufficient oil amount, and cavitation cannot be prevented.

In order to solve such a problem, the present applicant has previously disclosed Japanese Utility Model Application Laid-Open No. 63-152724 (Japanese Utility Model Application No. 62-0).
No. 46213) proposed a new hydraulic circuit. This hydraulic circuit, as shown in FIG. 5, supplies the discharge oil of the auxiliary hydraulic pump 1C to the main line 5A via the switching valve 11, the upper pipe 12, the center joint CJ, the lower pipe 13, the pressure reducing valve 14, and the check valve 15. Connected, the switching valve 11
Is switched to the “A” position, and decompressed pressure oil (for example, 10 kg / cm ² ) is introduced upstream of the check valve 15. In this way, by setting the makeup pressure to a low pressure higher than the tank pressure, the makeup flow rate in the direction shown by arrow S3 is supplemented during deceleration, and is combined with the flow rate in the directions shown by arrows S1 and S2. Cavitation during deceleration is reduced.

[0011]

However, the makeup circuit shown in FIG. 5 requires the auxiliary hydraulic pump 1C, the switching valve 11, and the pressure reducing valve 14, which increases the number of parts and increases the cost. Further, the makeup upper pipe 12 and the lower pipe 13 are connected through a center joint CJ, and the center joint CJ is provided with passages for large flow rates of the main pipelines 5A and 5B. The passage cannot be made too thick. as a result,
Even if the pipe diameters of the pipes 12 and 13 are increased, it is difficult to ensure a desired makeup flow rate, and cavitation may occur. Also, if this circuit is applied to both the forward and backward sides, it is necessary to provide two check valves 15 and two pipes, which increases the number of parts and increases the cost.

An object of the present invention is to provide a hydraulic circuit of a traveling hydraulic motor that can secure a desired makeup flow rate without increasing the number of parts.

[0013]

The present invention will be described with reference to FIG. 1 showing an embodiment. The present invention is directed to a hydraulic pump 1 (1A, 1B) provided on an upper rotating body, and an upper rotating body. Control valve 2 (2A, 2B) provided in
A traveling hydraulic motor 4 driven and supplied with oil discharged from a hydraulic pump 1 via a control valve 2 and a center joint CJ, and makeup for guiding makeup oil to a main pipeline 5 (5A, 5B) of the traveling hydraulic motor 4. The present invention is applied to a hydraulic circuit of a traveling hydraulic motor having the up pipeline 12. According to the first aspect of the present invention, the makeup pipeline 12 is provided to the main pipelines 5C and 5D between the center joint CJ and the control valve 2 via the first makeup valve 23.
The above object is achieved by connecting one end of B. Further, the invention of claim 2 is applied to a hydraulic circuit of a traveling hydraulic motor provided with a steering hydraulic pump 1D provided on the upper-part turning body, and a return line 26 of the steering hydraulic pump 1D is made up of a make-up pipe. It is connected to the road 12B. Furthermore, the invention of claim 3 provides a hydraulic circuit according to claim 1 or 2, wherein the traveling hydraulic motor is provided via a second make-up valve 8 provided between the traveling hydraulic motor 4 and its counterbalance valve 7. The main lines 5A and 5B of the motor 4 are connected to a makeup line 12B. According to a fourth aspect of the present invention, the other end of the makeup line 12B is connected to the upstream side 23 of the oil cooler 11 through which the return oil of the control valve 2 flows.

[0014]

[Action] Center joint CJ and control valve 2
Main lines 5C, 5D for the motor on the upper revolving structure side connecting
Makeup oil is introduced into the oil. Therefore, if a large amount of makeup oil is introduced, the large amount of makeup oil is guided to the traveling hydraulic motor 4 installed on the lower traveling body. Also, the return oil of the steering hydraulic pump 1D is joined to the makeup pipeline 12B, and a sufficient makeup flow rate can be secured. Therefore, cavitation of the traveling hydraulic motor 4 can be reliably prevented. Further, makeup oil is directly supplied from makeup line 12B to lower main lines 5A and 5C. Further, the pressure of the makeup oil can be set to the cooler relief pressure, and the replenishing efficiency is improved.

In the section of the means for solving the above-described problem and the operation of the present invention, the drawings of the embodiments are used to make the present invention easier to understand. It is not limited to the embodiment.

[0016]

FIG. 1 shows an embodiment in which the present invention is applied to a wheel-type hydraulic excavator. 4 and 5 are denoted by the same reference numerals and differences are mainly described. Makeup pipeline 12 having one end connected to main pipelines 5A and 5B via lower makeup valve (second makeup valve) 8
The other end of A is connected to the upstream pipeline 22 of the cooler relief valve 21 via the makeup pipeline 12B. The conduit 22 is a return conduit for the multiple control valves 2A and 2B. The upper main pipelines 5C and 5D between the traveling control valves 3a and 3b incorporated in the multiple control valves 2A and 2B and the center joint CJ are provided with an upper make-up valve (first make-up valve) 23.
Is connected to makeup line 12B, and makeup oil is also supplied to upper main lines 5C and 5D from various parts. The hydraulic pump 1 </ b> D is a steering hydraulic pump, and is connected to a steering hydraulic cylinder 25 via a steering valve 24. The return oil of the steering valve 24 is supplied to the return line 26 and the makeup line 12.
It is led through B to the upstream pipeline 22 of the cooler relief valve 21. In addition, each device drawn above the center joint CJ is installed on the lower revolving superstructure, and each device drawn on the lower side is installed on the upper revolving superstructure, and the main pipelines 5C, 5D on the upper revolving superstructure side and the lower revolving superstructure side. And the main pipelines 5A and 5B are connected via the center joint CJ.

Next, the operation of the hydraulic circuit will be described. (1) When moving forward and backward Switch the control valves 3a and 3b to "A".
The oil discharged from the hydraulic pumps 1A and B is supplied to the control valve 3
When the counter balance valve 7 reaches the counter balance valve 7 via the upper main pipes 5C and 5D, the counterbalance valve 7 is switched to "A", and the pressure oil passes through the counter balance valve 7 and the lower main pipe 5A at the "A" position. Then, the vehicle reaches the entrance port of the traveling motor 4, the traveling motor 4 rotates, and the vehicle moves forward. When the control valves 3a and 3b are switched to "C", the pressure oil reaches the traveling hydraulic motor 4 in the reverse route and reversely rotates, so that the vehicle moves backward.

(2) Deceleration, descent When the control valves 3a, 3b are switched to the neutral position during forward traveling, the pressure in the main line 5C is reduced and the counter balance valve 7 is switched to the neutral position. For this reason,
Since the main line 5B is throttled, the pressure rises, the crossover relief valve 6 opens, and pressurized oil flows from the main line 5B into the main line 5A. Also, the control valves 3a, 3b
In the neutral position, the main lines 5C and 5D communicate with each other.
D, flows into the main line 5A via the control valves 3a and 3b, the line 5C, and the counter balance valve 7. Further, since the pressure in the main pipelines 5A and 5C decreases, return oil of the multiple control valves 2A and 2B is introduced into the main pipeline 5C via the makeup pipeline 12B, the pipeline 22, and the upper makeup valve 23. . The return oil of the steering valve 24 is introduced into the main line 5C via the return line 26 and the upper makeup valve 23. Here, the make-up oil pressure is the relief pressure of the cooler relief valve 21. Further, makeup oil is also introduced into main line 5A from makeup line 12A via lower make-up valve 8. As described above, the makeup oil of a large flow rate set to the cooler relief pressure is introduced from the upper makeup valve 23 into the main line 5C, and the makeup oil is also made into the lower main line 5A from the lower makeup valve 8 as in the related art. Since the make-up oil is introduced, a sufficient amount of make-up oil is introduced into the inlet side of the hydraulic motor 4 to eliminate the possibility of cavitation. Make-up oil is introduced into the main pipelines 5D and 5B in the same manner during reverse travel.

As described above, the control valves 2A, 2
B and the return oil of the steering valve 24 are set to the cooler relief pressure and introduced into the main pipelines 5C and 5D, which are upper pipes. Therefore, when the control valves 3a and 3b are switched to the neutral position and decelerated, a large flow rate makeup is performed. Up oil can be introduced into the main pipelines 5A and 5B on the lower traveling body side, and cavitation can be reliably prevented. Therefore, when the traveling hydraulic motor 4 provided on the lower traveling structure and the oil tank 10 provided on the upper revolving structure are far apart,
Even when the inertial force is large or when driving at high speed,
During deceleration, pressure oil is reliably supplied to the inlet side of the traveling hydraulic motor 4, and cavitation is prevented. As described above, the traveling energy of the vehicle body is generated as heat of the hydraulic circuit during deceleration and stored in the vicinity of the traveling hydraulic motor 4 and the crossover relief valve 6. Is introduced into the main pipeline, so that overheating of the circuit can be prevented.

The present invention is not limited to the above embodiment, but is applied to various forms of hydraulic circuits for work vehicles.

[0021]

According to the present invention, the makeup oil is introduced into the upper main line connected to the lower main line via the center joint, so that a large amount of makeup can be applied without increasing the number of parts. The oil can be introduced into the traveling hydraulic motor, which reliably prevents cavitation during deceleration without increasing costs and also prevents overheating of the traveling hydraulic circuit. Further, since the return oil of the steering valve is used as the make-up oil, the above-mentioned effect can be further remarkable.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a partially enlarged view of FIG. 1;

FIG. 4 is a conventional hydraulic circuit diagram.

FIG. 5 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 1A, 1B Hydraulic pump 1C Auxiliary hydraulic pump 1D Steering hydraulic pump 2 Control valve 2A, 2B Multiple control valve 3a, 3b Traveling control valve 4 Traveling hydraulic motor 5 Main pipeline 5A, 5B Lower main pipeline 5C, 5D Upper main line 7 Counter balance valve 8 Lower make-up valve 9,10 Oil tank 11 Oil cooler 12 Make-up line 12A, 12B Make-up line 21 Cooler relief valve 23 Upper make-up valve 24 Steering valve 25 Steering hydraulic cylinder 26 Steering Return line CJ center joint

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Saburo Yoshio 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Inside the Tsuchiura Plant (72) Inventor Junichi Hosono 2-6-1, Otemachi, Chiyoda-ku, Tokyo Within Hitachi Construction Machinery Co., Ltd. (72) Akira Tatsumi 650, Kandamachi, Tsuchiura-shi, Ibaraki Prefecture Tsuchiura Plant, Hitachi, Ltd. (56) References JP-A-60-249707 (JP, A) JP-A-2-212603 (JP, A) JP-A-3-117157 (JP, U) JP-A-63-152724 (JP, U)

Claims (4)

(57) [Scope of request for utility model registration] 1. A hydraulic pump provided on an upper rotating body,
A control valve provided on the upper revolving unit, a traveling hydraulic motor driven and supplied with oil discharged from the hydraulic pump via the control valve and a center joint, and a traveling hydraulic motor that supplies makeup oil to the traveling hydraulic motor. In a hydraulic circuit for a traveling hydraulic motor having a make-up line leading to a main line, the make-up line is connected to the main line between the center joint and a control valve via a first make-up valve. A hydraulic circuit for a traveling hydraulic motor, one end of which is connected. 2. The traveling hydraulic motor according to claim 1, further comprising a steering hydraulic pump provided on the upper revolving unit, and a return line connected to the makeup line. Hydraulic circuit. 3. The hydraulic circuit according to claim 1, wherein
A main hydraulic line for the traveling hydraulic motor is connected to the makeup line via a second makeup valve provided between the traveling hydraulic motor and its counterbalance valve. Motor hydraulic circuit. 4. The hydraulic circuit according to claim 1, wherein the other end of the makeup line is connected to an upstream side of an oil cooler through which return oil of the control valve flows. Characteristic hydraulic circuit of hydraulic motor for traveling.