JPH0618820Y2 - Running hydraulic circuit of wheel type construction machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a traveling hydraulic circuit of a wheel type construction machine such as a wheel crane.

[Prior Art] Conventionally, as a traveling mechanism in a truck crane or the like,
The mainstream method is to transmit the rotational force of the prime mover to the wheels via a transmission, a drive shaft, etc. Also, the upper revolving structure has a separate prime mover for operating the hydraulic circuit for the crane.

However, in conventional truck cranes, etc.,
Since the rotational force of the prime mover is mechanically transmitted, the structure is complicated and expensive, and since the upper revolving structure is equipped with a separate prime mover, there are two prime movers on the same machine. It was uneconomical in this respect.

Therefore, conventionally, a system has been devised in which a traveling mechanism in a wheel-type construction machine is a hydraulic drive system, and a hydraulic drive circuit for traveling and a hydraulic circuit for a crane are both driven by the same prime mover.

FIG. 2 shows such a traveling hydraulic circuit, in which the prime mover 1 drives the variable displacement pump 2 and the control pump 3 and has the following configuration.

The discharge line 4 of the variable displacement pump 2 is provided with a pilot type traveling switching valve 5 and various switching valves 6 (only one is shown in the figure), and the traveling switching valve 5 is provided with a swivel joint (not shown). A traveling motor 7 is connected to the switching valve 6, and an actuator 8 for a crane is connected to the switching valve 6. The bypass circuit 9 connected to the discharge line 4 on the upstream side of the traveling switching valve 5 is connected to the traveling switching valve 5 and the switching valve 6, respectively, and the discharge on the further upstream side of the connection point of the bypass passage 9 is connected. A return line 11 is connected to the line 4 via a relief valve 10, and each switching valve 5, 6 is connected to the return line 11. By connecting the return line 11 to the tank 12, the discharge line 4 is connected to the tank 12 via the return line 11.

On the other hand, a control line 13 from the control pump 3 is provided with a switch valve 14 and a forward / reverse operation valve 15 which are interlocked with a traveling accelerator pedal, and two pilot lines 16 and 17 from the forward / reverse operation valve 15 are provided. It is connected to the switching operation side of the traveling switching valve 5, and the shuttle valve 1 is provided between both pilot lines 16 and 17.
8 is provided, and the pressure oil from the shuttle valve 18 is sent to the actuator 20 for controlling the discharge amount of the variable displacement pump 2 as a feedback line 19.

Reference numeral 21 is a relief valve for setting a control pressure, and 22 is a pressure oil suction line.

In the case of such a traveling hydraulic circuit, when the crane operation is performed, the control valve 13 is cut off by setting the switch valve 14 to the state shown in the figure, so that the discharge oil from the control pump 3 is returned to the tank 12 via the relief valve 21, Actuator
The control pressure does not act on 20, and the variable displacement pump 2 is fully opened. The valve position of the traveling switching valve 5 is the neutral position n, and the variable displacement pump 2 and the switching valve 6 are short-circuited.

When the switching valve 6 is operated in this state, pressure oil is supplied to the actuator 8 according to the operating direction of the switching valve 6.

Next, when the switch valve 14 is changed over by depressing the accelerator pedal, the control pump 3 and the forward / reverse operation valve 15 communicate with each other. Since the oil passage is short-circuited at the neutral position of the forward / reverse operation valve 15, all the oil discharged from the control pump 3 is returned to the tank 12.

When the forward / reverse operation valve 15 is switched to the a position, the control pressure acts on the a side of the travel switching valve 5 via the pilot line 17,
The pilot line 16 communicates with the tank 12. Therefore, the traveling switching valve 5 is switched to the a position, and the traveling motor 7
Pressure oil is fed from the variable displacement pump 2 to rotate the motor 7 in a desired direction. At this time, the pilot line
When the control pressure is supplied to 17, the shuttle valve 18 is switched, the pilot line 17 and the feedback line 19 communicate with each other, the control pressure acts on the actuator 20, and the discharge amount of the variable displacement pump 2 is throttled. Here, this control pressure is determined by the relief pressure of the relief valve 21, and this relief pressure is determined by the maximum oil amount required by the traveling motor 7.

Next, when the forward / reverse operation valve 15 is switched to the b position, the control pressure acts on the b side of the traveling switching valve 5 via the pilot line 16, and the pilot line 17 is connected to the tank 12. As a result, the traveling switching valve 5 is switched to the b position, pressure oil is fed in the opposite direction to the above, and the traveling motor 7 is rotated in the opposite direction. Further, the control pressure of the pilot line 16 switches the shuttle valve 18, and the control pressure also acts on the actuator 20 to control the discharge amount of the variable displacement pump 2.

In this way, by switching the switch valve 14,
By operating the forward / backward operation valve 15, the main body can be moved in a direction required for forward / backward movement, and the amount of oil supplied to the traveling motor 7 can be optimized.

[Problems to be solved by the invention] However, in the case of the traveling hydraulic circuit recently devised,
Since the switch valve 14 that is linked to the accelerator pedal is used, the pilot pressure acting on the travel switching valve 5 rises rapidly, and the switching operation of the travel switching valve 5 is performed quickly. It may occur. Further, the discharge flow rate of the variable displacement pump 2 is controlled by switching the shuttle valve 18 so that the pilot line 16 or 17 and the feedback line 19 are communicated with each other so that the control pressure gradually increases. Therefore, there is a problem that the response is slow.

In view of this, the present invention provides a traveling hydraulic circuit for a wheel-type construction machine in which the traveling switching valve is gently switched and the discharge flow rate of the variable displacement pump can be immediately controlled to prevent a shock at the start of traveling. Is to provide.

[Means for Solving the Problems] In order to achieve the above object, the present invention enables a variable displacement pump and a control pump to be driven by a single prime mover, and a pilot is provided in a discharge line from the variable displacement pump. Type traveling switching valve and a switching valve are provided, a traveling motor is connected to the traveling switching valve, a crane actuator is connected to the switching valve, and a forward / reverse operation valve is provided on a control line connected to the control pump. Connecting the forward-reverse operation valve and the travel switching valve with two pilot lines, providing a shuttle valve between the pilot lines, and further operating an accelerator pedal at a position upstream of the shuttle valve on the control line. In the traveling hydraulic circuit provided with a clutch valve that gently starts up the traveling switching valve in conjunction with the A feedback line is provided between the variable displacement pump and the displacement changing actuator, and a pilot switching valve set to a switching pressure lower than the switching starting pressure of the traveling switching valve is provided in the middle of the feedback line. The pilot switching valve is switched according to the pressure of the outlet line of the shuttle valve so that the control line and the capacity changing actuator are communicated with each other via the feedback line to control the discharge flow rate of the variable capacity pump.

[Operation] When the accelerator pedal is operated, the clutch valve operates in response to the operation of the accelerator pedal. Therefore, the control pressure from the control pump gradually increases and acts on the traveling switching valve through the pilot line via the forward / reverse operation valve. Therefore, the traveling switching valve switches slowly.
At this time, hydraulic pressure is applied to the displacement changing actuator of the variable displacement pump via the feedback line to control the discharge flow rate of the variable displacement pump.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, which has the same structure as the traveling hydraulic circuit shown in FIG.
Forward / backward operation valve in the control line 13 from the control pump 3
A clutch valve 23, which operates in conjunction with the accelerator pedal, is provided at a position between 15 and the relief valve 21. Further, instead of the feedback line 19 shown in FIG.
A feedback line 24 is provided between the actuator 20 and the position between the clutch valve 23 and the relief valve 21 in 13 and in the middle of the feedback line 24.
The pilot switching valve 25 set to a switching pressure lower than the switching starting pressure of the traveling switching valve 5 is provided, and the switching of the pilot switching valve 25 is performed by the outlet line of the shuttle valve 18.
It is constructed so that it can be performed by a pressure of 26.

In such a configuration, when the clutch valve 23 is switched by operating the accelerator pedal, the control pump 3 and the forward / reverse operation valve 15 communicate with each other.

When the forward / reverse operation valve 15 is switched to the a position, the control pressure acts on the a side of the travel switching valve 5 via the pilot line 17,
The pilot line 16 communicates with the tank 12. Therefore, the traveling switching valve 5 is switched to the a position, and pressure oil is fed from the variable displacement pump 2 to the traveling motor 7 to rotate the traveling motor 7 in a desired direction. At this time, since the clutch valve 23 operates in response to the operation of the accelerator pedal, the pressure oil from the control pump 3 gradually passes through the forward / reverse operation valve 15. Therefore, the traveling switching valve 5 switches slowly in response to the operation of the accelerator pedal. Therefore, a shock at the start of traveling is prevented.

On the other hand, when the control pressure is supplied to the pilot line 17, the shuttle valve 18 is switched, the pilot line 17 and the outlet line 26 of the shuttle valve 18 communicate with each other, and the control pressure acts on the pilot switching valve 25 as the switching pressure. . Therefore, due to this switching pressure, the pilot switching valve 25 is switched, and the feedback line 24 that was blocked is communicated,
The pressure oil in the control line 13 is supplied to the actuator 20 through the feedback line 24, and the discharge capacity of the variable displacement pump 2 is controlled. At this time, the pilot switching valve 25
Since the switching pressure is set lower than the switching start pressure of the traveling switching valve 5, the pilot switching valve 25 switches faster than the traveling switching valve 5. Therefore, before the travel switching valve 5 is switched, the discharge flow rate of the variable displacement pump 2 is already reduced.

As described above, according to the present invention, it becomes possible to slowly switch the traveling switching valve 5 and immediately control the discharge flow rate of the variable displacement pump.

In the above embodiment, in order to control the discharge flow rate of the variable displacement pump 2, the pressure oil of the control pump 3 is supplied to the actuator 20.
However, as long as it speeds up the operation of the variable displacement pump 2 at the time of rising, it is possible to provide a separate pump as a hydraulic pressure source for the variable displacement pump 2,
Needless to say, various changes can be made without departing from the scope of the present invention.

[Advantages of the Invention] As described above, according to the traveling hydraulic circuit of the wheel-type construction machine of the present invention, the following excellent effects can be obtained.

(i) Since the clutch valve that operates in conjunction with the accelerator pedal is provided, the travel switching valve can be gently switched and a shock at the start of travel can be prevented.

(ii) A pilot switching valve set to a switching pressure lower than the switching starting pressure of the traveling switching valve is installed in the feedback line of the control pump to supply pressure oil to the actuator of the variable displacement pump to drive the vehicle. The discharge flow rate of the variable displacement pump can be controlled before the switching valve is switched.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a traveling hydraulic circuit of a wheel type construction machine of the present invention, and FIG. 2 is an explanatory view of a hydraulic circuit recently considered. 2 ... Variable displacement pump, 3 ... Control pump, 4 ... Discharge line, 5 ... Travel switching valve, 6 ... Switching valve, 7 ... Travel motor, 13 ... Control line, 15 ... Forward / backward movement Operating valve, 1
6,17 …… Pilot line, 18 …… Shuttle valve, 20 ……
Actuator, 23 …… Clutch valve, 24 …… Feedback line, 25 …… Pilot switching valve, 26 ……
Exit line.

Claims (1)

[Scope of utility model registration request] 1. A variable displacement pump and a control pump can be driven by a single prime mover, and a discharge line from the variable displacement pump is provided with a pilot type traveling switching valve and a switching valve, and the traveling switching is performed. A traveling motor is connected to the valve, a crane actuator is connected to the switching valve, and a forward / reverse operation valve is provided on the control line connected to the control pump. The forward / reverse operation valve and the traveling switching valve are two. A clutch valve for connecting the pilot line and providing a shuttle valve between the two pilot lines, and further, at a position upstream of the shuttle valve on the control line, for gently raising the running switching valve in conjunction with the operation of the accelerator pedal. In the traveling hydraulic circuit provided with, between the position upstream of the clutch valve of the control line and the displacement changing actuator of the variable displacement pump. A feedback line is provided, and a pilot switching valve set to a switching pressure lower than the switching starting pressure of the traveling switching valve is provided in the middle of the feedback line. A traveling hydraulic circuit for a wheel-type construction machine, characterized in that the control line and the displacement changing actuator are connected to each other via a feedback line to control the discharge flow rate of the variable displacement pump.