JPH0687467U - Hydraulic circuit of construction vehicle - Google Patents

Abstract

(57) [Summary] [Purpose] A straight-ahead traveling function and a travel boosting function are easily realized. [Construction] The line switching valve 45 has a state in which the traveling motors 30 and 31 are driven by the pumps 21 and 22, respectively.
In step 2, the state where both traveling motors 30 and 31 are driven is switched to realize a straight traveling function. The line switching valve 45 is switched when both the traveling motors 30 and 31 are operated, and further, any attachment such as the arm 33 is operated. In such a state, the pilot pressure Py in the pilot line 62 becomes equal to the pressure Ps in the discharge circuit of the servo pump 20. When either traveling motor 30, 31 is operated, the pilot line 5
Pilot pressure Ps is applied to at least one of 6 and 57. Therefore, as the output of the shuttle valve 58, the pressure Px in the pilot conduit 39 becomes equal to Ps, and the set pressure of the relief valve 38 is switched to the high pressure side to realize the travel boosting function.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic circuit of a construction vehicle such as a hydraulic excavator.

[0002]

[Prior art]

 FIG. 7 shows an example of a prior art of a hydraulic circuit of a conventional hydraulic excavator. This prior art is disclosed in Japanese Utility Model Publication No. 62-21163. Such a hydraulic excavator is provided with a pair of pumps 1 and 2. Operation valves 3, 4, and 5 are connected in parallel to the discharge circuit of one pump. Operation valves 6, 7, 8, 9 are connected in parallel to the discharge circuit of the other pump 2. The operation valves 3 and 6 arranged at the uppermost stream of each parallel circuit are provided to drive and operate the pair of traveling motors 10 and 11. The other operating valves 4, 5, 7, 9 are provided for driving hydraulic cylinders 12, 13, 14 for driving, for example, buckets, booms or arms. The operation valve 8 is provided to drive and operate the turning motor 15. These attachments are divided into two groups and connected in parallel.

The discharge circuits of the pumps 1 and 2 are connected to a relief valve 18 whose set pressure is switched by a pressure setting spring 17 connected to one rod of a double rod type cylinder 16 via check valves. Connected. The cylinder 16 presses the pressure setting spring 17 to switch the set pressure of the relief valve 18 to the high pressure side when at least one of the operation valve 3 and the operation valve 6 is not in the neutral position. When the operation valve 3 or the operation valve 6 is operated, traveling by the traveling motors 10 and 11 is performed. That is, the hydraulic circuit shown in FIG. 7 has a traveling pressure increasing function for increasing the discharge pressure of the pumps 11 and 12 during traveling.

In construction vehicles such as hydraulic excavators, most of the operating time uses only attachments such as booms, arms, buckets, or turns, and the travel motor is stopped. However, construction vehicles need to travel on rough roads, and it is preferable to increase the output as much as possible when traveling. Therefore, a travel pressure increasing function is provided to increase the set pressure of the relief valve only when traveling for a short time.

[0005]

[Problems to be solved by the device]

 In the prior art shown in FIG. 7, a pair of pumps 1 and 2 drive a pair of traveling motors 10 and 11 and a pair of attachment groups, respectively. Therefore, for example, only one pump 1 needs to drive the hydraulic cylinder 14 at the same time while simultaneously driving the pair of traveling motors 10 and 11 to move straight. When the hydraulic cylinder 14 is driven, the hydraulic pressure output to one of the traveling motors 10 is reduced and it becomes impossible to perform straight traveling.

A prior art of switching the hydraulic circuit so that the straight traveling function is not impaired even if the attachments are simultaneously operated is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-165429. In this prior art, when the attachment is operated during straight traveling, one pump drives both traveling motors and the other pump switches the hydraulic circuit so as to drive the attachment. However, this prior art does not include the traveling boosting function as disclosed in Japanese Utility Model Laid-Open No. 62-21163.

An object of the present invention is to provide a hydraulic circuit for a construction vehicle that can easily realize a straight traveling function and a traveling boosting function.

[0008]

[Means for Solving the Problems]

 The present invention provides a hydraulic circuit of a construction vehicle that operates by supplying hydraulic oil from a pair of pumps to a pair of left and right traveling motors and a plurality of attachments. A pair of motor operating valves equipped with a main switching valve that switches the flow rate and a pilot switching valve that switches the flow direction of the pilot hydraulic oil in conjunction with the main switching valve, and a check valve on the inlet side of the discharge circuit from the pair of pumps. Relief valves that are connected via a pair of input ports to the output sides of the pilot switching valves of the pair of motor operating valves, respectively. A shuttle valve, the output side of which is connected to the pilot input side of the relief valve, and the pair of motor main switching valves, which are arranged in the most upstream. In the flow, a pair of tandem pipes that connect each group of attachment operation switching valves, which are divided into a pair of groups in advance, in series, and an operation switching valve of the attachments of the pair of groups are connected in parallel. A pair of parallel conduits are formed, and the NO. 1 pump and NO. A passage is provided in the parallel line for attachment directly by turning the throttle from two pumps, and the tandem line is connected to the downstream of the parallel line throttle through a check.

In response to the pilot pressure from the output side of the pair of parallel pipelines and the pair of motor control valves, the operating hydraulic fluid from one pump is sent to one tandem pipeline and one parallel pipeline. The first state of supplying the operating oil from the other pump to the other tandem conduit and the other parallel conduit, and supplying the operating oil from one pump to the pair of tandem conduits However, at least one attachment is operated and at least one attachment is operated, and both traveling motors are operated by the line switching valve that switches between the second state in which the operating oil from the other pump is supplied to the pair of parallel lines. Only when it is operated, it is connected so as to derive the pilot pressure for switching the above-mentioned line switching valve from the first state to the second state from the pilot switching valve of the one motor operating valve. A pilot switching valve for each motor, wherein the pilot switching valve of each motor operation valve derives pilot pressure from the output side to the shuttle valve when the traveling motor is being operated. Is.

Further, a throttle is connected between the conduit switching valve of the present invention and the pair of parallel conduits, respectively.

[0011]

[Action]

 According to the present invention, the pair of motor operation valves provided for each of the pair of left and right traveling motors is provided with the pilot switching valve that interlocks with the main switching valve. The inlet side of the pilot switching valve is connected to the pilot hydraulic power source via a throttle. The outlet side of the pilot switching valve is connected via a shuttle valve to a relief valve whose set pressure can be switched between high and low. The relief valves are connected to the discharge circuits from a pair of pumps via check valves. Since the pilot pressure to the relief valve is given when at least one of the pair of motor operating valves is operated, the travel boosting function is realized. Moreover, the pair of tandem pipelines and the pair of parallel pipelines are switched by the pipeline switching valve. The second state of the line switching valve is switched only when at least one attachment is operated and both traveling motors are operated, and the straight traveling function is realized.

Further, according to the present invention, throttles are respectively connected between the conduit switching valve and the pair of parallel conduits. As a result, the tandem conduit can be preferentially operated in each actuator.

[0013]

【Example】

 FIG. 1 shows a hydraulic circuit of a hydraulic excavator according to an embodiment of the present invention. Pilot hydraulic oil is supplied from the servo pump 20. The hydraulic oil for operation is supplied from the pair of variable displacement pumps 21 and 22. Operation valves 23, 24, 25, 29a are connected to the discharge circuit of one pump 21, and operation valves 26, 27, 28, 29b are connected to the discharge circuit of the other pump 22, respectively. The operation valve 23 is provided for driving the left traveling motor 30. The operation valve 26 is provided for driving operation of the right travel motor 31. The traveling motors 30 and 31 drive the left and right traveling crawlers, respectively. The operation valve 24 operates and drives the hydraulic cylinder 32 for the boom. The operation valve 25 operates and drives the hydraulic cylinder 33 for the bucket. The operation valve 27 operates and drives the hydraulic cylinder 34 for the arm. The operation valve 28 drives a turning motor 35 for turning. The operation valve 29a is provided to perform the operation of joining the arms. The operation valve 29b is provided to perform a boom merging operation. FIG. 1 shows a state in which each of the operating valves 23, 24, 25, 26, 27, 28, 29a, 29b is in the neutral position.

The discharge circuits of the pumps 21 and 22 are provided with a relief valve 38, which adjusts a pressure setting spring 37 by a cylinder 36 and switches the set pressure. The cylinder 36 is controlled by the pressure Px in the pilot line 39. A relief valve 40 is provided in the discharge circuit of the servo pump 20 to set the relief pressure Ps. The relief valve 38 is connected to the discharge circuits of the pumps 21 and 22 via check valves 41 and 42, respectively. The maximum values of the discharge pressures P1 and P2 of the pumps 21 and 22 are suppressed to the set pressure of the relief valve 38.

The discharge circuits of the pumps 21 and 22 are connected to the throttles 43 and 44 and the line switching valve 45. The conduit switching valve 45 switches the discharge circuits from the pumps 21 and 22 between the main conduits 46 and 47, which are tandem conduits, and the throttles 43 and 44, as described later. One main pipeline 46 is connected to the main pipeline 48 via the main switching valve of the operation valve 23 for the left travel motor. The other main pipeline 47 is connected to the main pipeline 49 via the main switching valve of the operation valve 26 for the right travel motor. The main pipe line 48 is connected to the tank 50 through the operation valves 24, 25, 29a in series. The main pipeline 49 is connected to the tank 50 through the operation valves 27, 28, 29b in series.

The discharge circuits of the servo pump 20 are connected to the inlet sides of the throttles 51, 52, 53, respectively. Pilot lines 54 and 55 are connected to the outlet sides of the throttles 51 and 52, respectively. The pilot conduit 55 is connected to the pilot conduit 56 via the pilot switching valve of the operation valve 23. The pilot line 54 is connected to the pilot line 57 via the pilot switching valve of the operation valve 26. The pilot lines 56 and 57 are connected to a pair of input sides of the shuttle valve 58, respectively. The output side of the shuttle valve 58 is connected to a pilot line 39 for switching the set pressure of the relief valve 38.

At the neutral position of the operation valve 23, the pilot pipe line 55 and the pilot pipe line 56 are connected and further connected to the drain pipe line 59. In the neutral position of the operation valve 26, the pilot line 57 is connected to the drain line 60. Therefore, the input sides of the shuttle valve 58 are both connected to the drain conduit, and the pressure Px of the pilot conduit 39 is atmospheric pressure. Each of the operation valves 24, 25, 29a, 29b, 28, 27 has a pilot switching valve, and is connected in series at the neutral position to form a drain line 61 1.

The switching of the conduit switching valve 45 is performed by the pilot pressure Py in the pilot conduit 62. Drain generated when the conduit switching valve 45 operates is discharged to the drain conduit 63.

Hydraulic oil is supplied to the input side of the main switching valves of the operation valves 24, 25, 29a from the main pipeline 71 which is one parallel pipeline via the check valves 64, 65, 69a. Hydraulic fluid is supplied to the input side of the main switching valves of the operation valves 27, 28, 29b from the other main pipeline 72 which is a parallel pipeline via check valves 67, 68, 69b, respectively. The outlet side of the throttle 53 is connected to the uppermost stream side of the drain conduit 61 via the pilot conduit 73.

FIG. 2 shows the operation valve 23, FIG. 3 shows the operation valve 26, and FIG. 4 shows the operation valve 24. The operation valves 23, 26, 24 are switched to three positions by interlocking the main line and the pilot line. The switching positions 23a, 26a, 24a of the pilot switching valves correspond to the switching positions 23A, 26A, 24A of one of the main switching valves of the operating valves 23, 26, 24, respectively. The other switching positions 23B, 26B, 24B correspond to the switching positions 23b, 26b, 24b of the pilot switching valve, respectively. The neutral positions 23C, 26C, 24C of the main switching valve correspond to the neutral positions 23c, 26c, 24c of the pilot switching valve, respectively. In these operating valves, the main switching valve performs a driving operation in the opposite direction between one switching position and the other switching position. There is no difference in the control of the pilot switching valve depending on the direction, and switching to either direction will result in a connection state different from the neutral position.

FIG. 5 shows the configuration of the conduit switching valve 45. The conduit switching valve 45 operates as a pilot type 4-port 2-position switching valve. When the pilot pressure Py is not applied to the pilot line 62, two ports out of the four ports are connected and the switching position 45A in the first state is reached. When the pilot pressure Py is applied to the pilot conduit 62, the open center type connection state with the throttle including the throttle 45x is established, and the switching position 45B which is the second state is established.

The operation of the hydraulic circuit of this embodiment will be described with reference to FIGS. As the operation mode, eight kinds as shown in the following Table 1 can be realized.

[0023]

[Table 1]

The state shown in FIG. 1 in which all the operation valves are in the neutral position is the mode 1. At this time, on the input side of the shuttle valve 58, the pilot switching valves of the operation valves 23 and 26 are connected to the drain conduits 59 and 60 via the neutral positions 23c and 26c, respectively. The pressure Px is a gauge pressure and is zero. Further, since the pilot switching valve neutral position 23c of the operation valve 23 connects the pilot conduit 62 to the drain conduit 59, the pilot pressure Py of the pilot conduit 62 is zero in gauge pressure. Therefore, the relief valve 38 is on the low pressure side, and the conduit switching valve 45 is in the first state.

When one or more of the operation valves 24, 25, 27, 28, 29a, 29b are operated, the mode 2 is entered, the drain line 61 is shut off, and the pilot line 73 is filled with pilot pressure. Occur. However, it does not affect the pilot pressures Px and Py. Therefore, also in mode 2, as in mode 1, the relief valve 38 is on the low pressure side, and the conduit switching valve 45 remains in the first state.

When the operating levers 23 and 26 are individually operated or both are operated at the same time, only the pilot pressure Px is generated and the pilot pressures Py are zero, and the modes 3 and 4 and 7 operate respectively. To do. Regardless of the switching position of the operation valve 23, the pilot pipe line 62 is connected to the drain pipe line 61 via the check valve 66. Since the drain conduit 61 is continuous, the pilot pressure Py in the pilot conduit 62 becomes zero. When the pilot switching valve of the operation valve 23 is operated to either of the switching positions 23a and 23b, the pilot conduit 56 is disconnected from the drain conduit 59 and is connected only to the pilot conduit 55. . The pilot conduit 57 is disconnected from the drain conduit 60 when the operation valve 26 is operated to either of the switching positions 26a and 26b, and is connected to the pilot conduit 54. Therefore, in any one of the modes 3, 4, and 7, the pilot pressure is applied to one of the pair of inputs of the shuttle valve 58, and the pilot pressure Px in the pilot line 39 is changed to the servo pump 20. Becomes equal to the pilot pressure Ps of the discharge circuit. With this pressure Ps, the set pressure of the relief valve 38 is switched to the high pressure side, and the travel boosting function is realized.

In mode 5, the operation valve 23 is operated to drive the left traveling motor 30, and at the same time, the operation valve for one of the attachments is operated. For example, it is assumed that the operation valve 24 is being operated. The pilot conduit 62 is connected to the input side of the check valve 66 and the pilot conduit 57 via the switching position 23a or 23b of the pilot switching valve of the operation valve 23. When the operation valve 24 is operated, the drain conduit 61 is shut off, so that the pressure in the pilot conduit 73 on the outlet side of the check valve 66 becomes Ps. However, the pilot switching valve of the operation valve 26 connects the pilot line 57 to the drain line 60 at the neutral position 26c. Therefore, the pilot pressure Py in the pilot conduit 62 becomes zero. On the other hand, the pilot pipe line 56 cancels the connection state with the drain pipe line 59 at the switching positions 23a and 23b, is connected to the pilot pipe line 55, and is supplied with the pilot pressure Ps. Therefore, the pilot pressure Px in the pilot conduit 39 also becomes equal to Ps.

The mode 6 in which the operation valve 26 for operating the traveling motor 31 on the right side is operated and any one of the attachments is operated is the same as the mode 4 with respect to the pilot pressures Px and Py.

In mode 8 in which the operation valve 23 and the operation valve 26 are simultaneously operated and the attachment is also operated, pilot pressure Px is applied to pilot pressure Px as in mode 7, so the relief valve 38 The boosting function is realized by. In mode 7, the drain line 61 on the outlet side of the check valve 66 is continuous, but if any attachment is operated, the drain line 61 becomes discontinuous, and the pilot line 62 is piloted. The pressure Ps is supplied. As a result, the line switching valve 45 is switched to the second state. In the second state of the conduit switching valve 45, the discharge circuit of the one pump 21 is connected to the main conduits 71 and 72, which are parallel conduits, via the throttles 43 and 44, respectively. The discharge circuit of the other pump 22 is connected to the main pipelines 46 and 47 which are a pair of tandem pipelines. That is, the hydraulic oil from one pump 21 is given to the attachment, and the hydraulic oil from the other pump 22 is given to both traveling motors 30 and 31. In this way, the function of straight traveling is realized.

FIG. 6 shows a part of a hydraulic circuit according to another embodiment of the present invention. This embodiment is similar to the embodiment of FIG. 1 and uses a 2-port 2-position switching valve 74 instead of the throttle 43 of FIG. The switching valve 74 operates simultaneously with the conduit switching valve 45 by the pilot pressure from the pilot conduit 62. It is closed when this pilot pressure is not applied. When the pilot pressure Ps is applied, the throttle valve enters the throttle open state, which is substantially the same as the embodiment of FIG. The throttles 43 and 44 of the embodiment of FIG. 1 and the switching valve 74 of the embodiment of FIG. 6 operate as throttles to reliably switch between the tandem pipeline and the parallel pipeline.

It is needless to say that each operating valve may be directly operated by human power, or may be remotely operated by a mechanical type or a pilot type. Although the servo pump 20 is used as the pilot hydraulic power source, the pilot pressure may of course come from the main pipeline via the pressure reducing valve, as in the case of the prior art of the actual opening Sho 62-21163. Is.

[0032]

[Effect of device]

 As described above, according to the present invention, there is provided a traveling straight traveling function that does not impair the straight traveling performance even if another attachment is operated while traveling straight, and a traveling boosting function that raises the relief valve set pressure during traveling. It is possible to realize a hydraulic circuit having both. Moreover, since the functions of straight traveling and boosting of traveling can be realized only by one conduit switching valve, one relief valve and pilot conduit, the hydraulic circuit can be simply constructed.

Further, according to the present invention, the tandem pipeline can be preferentially operated by providing a throttle between the pipeline switching valve and the pilot pipeline. As a result, the function of traveling straight ahead can be easily realized.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of an operation valve 23 shown in FIG.

3 is a circuit diagram of an operation valve 26 of FIG.

4 is a circuit diagram of a control valve 24 of FIG.

5 is a circuit diagram of a conduit switching valve 45 of FIG.

FIG. 6 is a partial hydraulic circuit diagram of another embodiment of the present invention.

FIG. 7 is a prior art hydraulic circuit diagram.

[Explanation of symbols]

 20 Servo pump 21, 22 Pump 23-28, 29a, 29b Operation valve 30, 31 Traveling motor 32, 33, 34 Hydraulic cylinder 35 Swing motor 38 Relief valve 39, 62 Pilot line 43, 44 Throttling 45 Pipe line switching valve 46 ~ 49,71,72 Main line 51,52 Throttle 54 ~ 57 Pilot line 58 Shuttle valve 59,60 Drain line 74 Switching valve

Claims (2)

[Scope of utility model registration request] 1. A hydraulic circuit of a construction vehicle that operates by supplying hydraulic oil from a pair of pumps to a pair of left and right traveling motors and a plurality of attachments. Check the inlet side of the pair of motor operating valves equipped with a main switching valve that switches the direction and a pilot switching valve that switches the flow direction of the pilot hydraulic oil in conjunction with the main switching valve, and the discharge circuit from the pair of pumps. A relief valve that is connected via a valve and that can switch the set pressure between high and low depending on the presence or absence of pilot pressure, and a pair of input sides connected to the output side of the pilot switching valve of the pair of motor operating valves, respectively. A shuttle valve whose side is connected to the pilot input side of the relief valve, and the pair of motor main switching valves are arranged in the uppermost stream, respectively. Includes a pair of tandem conduits that connect each group of attachment operation switching valves that have been divided into a pair of groups in advance, and a pair that connects the operation switching valves of the attachments of the pair of groups, respectively, in parallel. In response to the pilot pressure from the parallel pipelines and the output side of the pair of motor control valves, operating oil from one pump is supplied to one tandem pipeline and one parallel pipeline, and the other A first state in which operating oil is supplied from the pump to the other tandem pipeline and the other parallel pipeline; and operating oil from one pump is supplied to the pair of tandem pipelines,
A pipe line switching valve that switches between a second state in which the operating hydraulic fluid from the other pump is supplied to the pair of parallel pipe lines, and at least one attachment are operated, and both traveling motors are operated. And a switching pilot pipe line connected so as to derive a pilot pressure for switching the pipe line switching valve from the first state to the second state from the pilot switching valve of the one motor operating valve, The hydraulic circuit of a construction vehicle, wherein the pilot switching valve of each motor operation valve derives pilot pressure from the output side to the shuttle valve when the traveling motor is being operated. 2. The hydraulic circuit for a construction vehicle according to claim 1, wherein throttles are respectively connected between the pipeline switching valve and the pair of parallel pipelines.