JP3992611B2 - Backhoe hydraulic circuit structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backhoe hydraulic circuit structure including a load sensing system that controls a pump flow rate according to a detected load.
[0002]
[Prior art]
The hydraulic circuit structure of the backhoe equipped with the load sensing system is such that when traveling only, the pressure oil from the first pump and the second pump is supplied independently to the sections of the left and right traveling motors, and the traveling is stopped to excavate. When operating only the front working device, the pressure oil from the first pump and the second pump is merged and supplied to the section of the front working device, and the flow rates of the first pump and the second pump according to the detected work load. When controlling and operating the front working device while traveling, the pressure oil from the first pump and the second pump is independently supplied to the left and right traveling sections, and the third provided for turning and dozers. A configuration has been proposed in which pressure oil from a pump is supplied to a section of a front working device (see Patent Document 1). .
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-206256
[Problems to be solved by the invention]
According to the above-described conventional hydraulic circuit structure, since the flow rate obtained by joining the first pump and the second pump is supplied for front work, the maximum flow rate of each of the first pump and the second pump is the maximum required for normal front work. Half of the flow rate. For example, in the case of a 5-ton class backhoe, the maximum flow rate required for front work is about 130 (liters / minute), so the maximum flow rate of each of the first pump and the second pump is 65 (liters / minute). The flow rate required for traveling in class (generally 45 to 50 (liters / minute)) is increased.
[0005]
Therefore, when only traveling is performed, the first pump and the second pump discharge more than necessary by the flow control based on the horsepower control, and overheating and temperature rise of the hydraulic oil are likely to occur. there were. Further, when operating the front working device while traveling, a pilot-type switching valve is required to join and supply the pressure oil from the third pump to the section of the front working device, which tends to increase the cost.
[0006]
In the conventional hydraulic circuit structure, a flow path switching valve is provided upstream of the traveling section for pressure oil from the first pump and the second pump, and the first pump is operated by switching operation to the flow path switching valve. And a state in which the pressure oil from the second pump is independently supplied to the left and right traveling sections and a state in which the pressure oil from the first pump and the second pump are merged and supplied to the section of the front working device. In order to maximize the discharge amount of the first pump and the second pump during traveling, it is necessary to configure a circuit for making the pump discharge pressure (PPS) in the load sensing system zero. Therefore, the circuit configuration becomes complicated, and the flow path switching valve itself has a large number of ports related to the circuit for transmitting the pump discharge pressure (PPS). Now, it was those that contribute to the cost up.
[0007]
The present invention has been made paying attention to such points, and uses a first pump and a second pump that are controlled in flow rate, and a third pump for turning, and the front work of the load sensing system. In the configuration operated below, the first pump and the second pump can be reduced in size, the travel flow rate can be set to an appropriate amount, and the switching valve for joining the third pump can be omitted. The main object of the present invention is to provide a hydraulic circuit structure capable of simplifying a flow path switching valve and a circuit configuration for supplying pressure oil from the first pump and the second pump to a front working section and reducing the cost. And
[0008]
[Means for Solving the Problems]
[Configuration, Action, and Effect of Invention of Claim 1]
[0009]
In the hydraulic circuit structure of the backhoe according to the first aspect of the present invention, the pressure oil from the first pump and the second pump is independently supplied to the left and right traveling sections and the center bypass of the control valve that controls the left and right traveling sections is provided. The pressure oil supply state for supplying the pressure oil that has passed through the left and right traveling sections to the group of sections for the front work equipment, and the pressure A flow path switching valve that can be switched to a drained oil state that drains oil
Pressurized oil from the third pump, via a section for pivoting the section for the front work device, configured to always supplied in a state of not using the section for turning,
A load sensing system that controls the flow rate of the first pump and the second pump according to the detected load of the front working system is provided, and the circuit pressure at the upstream portion of the flow path switching valve is detected as the discharge pressure of the load sensing system. It is configured.
[0010]
According to the above configuration, when the section group for the front working device is operated, the pressure oil from the first pump and the second pump and the pressure oil from the third pump are supplied and joined. The maximum flow rate of pressurized oil should be set to the maximum flow rate required for front work. For example, when the maximum flow rate required for the front work is 130 (liters / minute) and the third pump flow rate is 30 (liters / minute), the maximum flow rates of the first pump and the second pump are 50 (liters). / Min).
[0011]
Further, when the flow path switching valve is switched to the oil draining state during traveling, the upstream of this valve is drained and the circuit pressure becomes zero, which is transmitted as the pump discharge pressure (PPS) of the load sensing system, and the first pump and the first pump. The two pumps are controlled up to the maximum flow rate.
[0012]
Therefore, according to the first aspect of the invention, the first pump and the second pump can be reduced in size, and the flow rate for traveling can be made appropriate. In addition, since the pressure oil from the third pump is always supplied to the front working device section without using the turning section, a switching valve for joining the third pump is not required as in the prior art. The circuit structure can be simplified and the cost can be reduced.
[0013]
Also, a circuit for zeroing the pump discharge pressure (PPS) in the load sensing system when traveling can be easily obtained upstream of the flow path switching valve, and the circuit for switching the flow path switching valve and pump discharge pressure. Is simplified, and the flow path switching valve itself is a simple one with a small number of ports, which is effective for cost reduction.
[0014]
[Configuration, Action, and Effect of Invention of Claim 2]
[0015]
The hydraulic circuit structure of the backhoe of the invention according to claim 2 is the pressure oil supply state according to the invention of claim 1, wherein when the state in which both the right and left traveling sections are not operating is detected, the flow path switching valve is brought into the pressure oil supply state. When it is detected that at least one of the left and right traveling sections is in an operating state, the oil draining state is switched.
[0016]
According to the above configuration, not only the state where the left and right traveling sections are operated together, but also when only one of the traveling sections is operated, the flow path switching valve is switched to the oil drained state as described above. The pump discharge pressure (PPS) in the load sensing system becomes zero, and the first pump and the second pump are controlled to the maximum flow rate.
[0017]
Therefore, according to the invention of claim 2, it is possible to maintain a high turning ability only with the one-side traveling device, which is effective in improving mobility.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an overall side view of the backhoe. This backhoe is mounted on the upper part of a traveling machine base 2 equipped with a pair of left and right crawler type traveling devices 1L and 1R so that a swivel base 5 equipped with an engine 3 and an operating unit 4 can be turned around the vertical axis X1. A front device 9 comprising a boom 6, an arm 7, and a bucket 8 sequentially connected to the front part of the swivel base 5 is installed, and the earth for dozer work is disposed at the front part of the traveling machine base 2. A board 10 is equipped.
[0019]
The left and right traveling apparatuses 1L and 1R are driven forward and backward by traveling hydraulic motors ML and MR, respectively, and the swivel base 3 is driven to turn left and right by a turning hydraulic motor MT. Boom 6 of the front device 6, arm 7 and bucket 8 are each boom cylinder C _1, and the arm cylinder C _2, vertical while being driven by the bucket cylinder C _3, the entire front unit 9 by the swing cylinder C ₄ It is driven to swing (swing) left and right around the axis X2. Further, a blade 10 is adapted to be vertically driven by a dozer cylinder C _5.
[0020]
FIG. 2 shows a hydraulic circuit that drives the various hydraulic actuators described above. In the figure, V ₁ is a control valve for traveling (left), V ₂ is a control valve for traveling (right), V ₃ is a control valve for boom, V ₄ is a control valve for arm, and V ₅ is for bucket. control valve, V ₆ are control valves for the swing, V ₇ are control valves, V ₈ control valve for swiveling, V ₉ for the service port is a control valve for dozer control valve for the left and right running of For V ₁ and V ₂ , artificially-operated ones in which the spools are directly switched by the left and right traveling levers 13 provided in the control tower 12 in front of the control seat 11 are adopted, and for swings, service ports, Each of the control valves V ₆ , V ₇ , V ₉ for the dozer is of an artificially operated type that directly operates the spool by lever operation or pedal operation, and for the boom, arm, bucket, and , Each of the control valves V ₃ , V ₄ , V ₅ , V ₈ for turning is a hydraulic pilot operated type, and is operated by a pair of left and right working levers 14 arranged on the control tower 12 so as to be able to perform a cross operation. The pilot valve is operated to an opening degree corresponding to the lever operation amount by a pilot pressure supplied from a pilot valve (not shown).
[0021]
As the hydraulic oil supply source in this hydraulic circuit, a first pump P ₁ , a second pump P ₂ , a third pump P ₃ and a pilot pump P ₄ driven by the engine 3 are provided. P ₁ and the second pump P ₂ are mainly used for the traveling system and the front working system, and are constituted by a variable displacement axial plunger pump capable of changing the discharge amount by changing the angle of the swash plate, which will be described later. The flow rate is controlled by the load sensing system. The third hydraulic pump P ₃ is mainly used for turning and dozer work, and a constant capacity gear pump is used. The pilot pump P ₄ is a pilot pressure supply pump composed of a constant capacity gear pump. The pilot pump P ₄ supplies pilot original pressure to a pilot valve (not shown) and three pilot oil passages a ₁ and a ₂ for detecting valve operation. , A ₃ are supplied with pilot pressure.
[0022]
The load sensing system is a system that can improve the power saving and operability by controlling the pump discharge amount according to the work load pressure and discharging the hydraulic power required for the load from the pump. , Boom section, arm section, bucket section, swing section, and service port front working section. Here, an after-orifice type load sensing system is used in which a pressure compensation valve CV is connected after the spool of each control valve V _{3 to} V ₇ in each section. Furthermore, the unload valve V ₁₀ and the system relief valve V ₁₁ is connected to the end of the hydraulic fluid supply passage b of the front work sections belonging to this load sensing system.
[0023]
A flow rate compensation valve V ₁₂ is provided for controlling the flow rate of the first pump P ₁ and the second pump P ₂ , and the flow rate compensation for adjusting the swash plate angle of the first pump P ₁ and the second pump P _2. use the piston Ac is provided with a horsepower control piston Ap, maximum negative pressure of the load sensing line in each section is transmitted to the flow compensation valve V ₁₂ as a signal pressure PLS for controlling the signal pressure PLS And the first pump P ₁ and the second pump P _{2 so} that the difference between the discharge pressure PPS of the first pump P ₁ and the second pump P ₂ is maintained at the control differential pressure given to the flow rate compensation valve V _12. The discharge flow rate is controlled. The discharge pressure PPS of the first pump P ₁ and the second pump P ₂ is detected as the pressure of the oil passage f that joins the center oil passages e ₁ and e ₂ of the left and right traveling sections, as will be described later. .
[0024]
Here, as shown in FIG. 1, the control differential pressure applied to the flow rate compensation valve V ₁₂ is given by the spring 15 and the differential pressure piston 16, and the rotational speed of the engine 3 is increased. When the discharge amount of the pilot pump P ₄ increases, the control differential pressure component provided by the differential pressure piston 16 increases, and the discharge flow rates of the first pump P ₁ and the second pump P ₂ increase accordingly. If the engine 3 is controlled and the rotational speed of the engine 3 decreases and the discharge amount of the pilot pump P ₄ decreases, the control differential pressure component provided by the differential pressure piston 16 decreases, and the first pump P _{1 correspondingly} decreases. The discharge flow rate of the second pump P ₂ is controlled to be small.
[0025]
Further, as described above, each section of the front working device 9 belongs to the load sensing system, whereas each section of the traveling, turning, and dozer is configured by an open circuit, and the left and right traveling The section center oil discharge passages e ₁ and e ₂ are joined to the oil passage f, and the oil passage f is connected to the pressure oil supply oil passage b of the front working section via a pilot-type passage switching valve V _13. Has been. Further, the center oil drain passage g of the turning and dozer section (corresponding to the turning section) is connected to the pressure oil supply oil passage b of the front working section.
[0026]
By switching the flow path switching valve V ₁₃ according to the running state, the following pressure oil supply state appears.
[0027]
[Stationary work]
In a state where the vehicle is not running, as shown in FIG. 3, no pressure is generated in the pilot oil passage a ₁ , so that the flow path switching valve V ₁₃ is in a pressure oil supply state, and the first pump P ₁ and the second pump The center oil discharged from P ₂ is supplied to the pressure oil supply oil passage b of the working section which is a load sensing system through the merge oil passage f and the passage switching valve V ₁₃ . Further, the pressure oil from the third pump P ₃ is also joined and supplied to the pressure oil supply oil passage b of the working section via the center oil discharge passage g of the swiveling and dozer section. That is, when the vehicle is not traveling, the total amount of oil from the _first to third pumps P ₁ , P ₂ , P ₃ is supplied to the pressure oil supply oil passage b of the front work section.
[0028]
Therefore, for example, when the maximum flow rate required for the front work is 130 (liters / minute) and the flow rate of the third pump P ₃ is 30 (liters / minute), the first pump P ₁ and the second pump P ₂ Therefore, the combined oil amount of 100 liters / minute is required, and the maximum flow rates of the first pump P ₁ and the second pump P ₂ may be 50 liters / minute, respectively.
[0029]
When the front working mechanism 9 is actuated operation, the first flow control of the pump P ₁ and the second pump P ₂ is made by a load sensing system, the supply of pressure oil at the flow rate corresponding to the load is performed.
[0030]
Here, the relief pressure of the relief valve V ₁₄ connected to the discharge passage of the third pump P ₃ is connected a relief of the relief valve V ₁₅ to the first discharge passage of the pump P ₁ and the second pump P ₂ It is set above the pressure. According to this, the pressure oil from the third pump P ₃ can be joined to the pressure oil from the first pump P ₁ and the second pump P ₂ without being relieved and supplied to the front work section.
[0031]
Incidentally, if the relief pressure of the third pump P ₃ is set lower than the relief pressures of the first pump P ₁ and the second pump P ₂ , the first to third pumps P ₁ , P ₂ , P ₃ When operating the front work section with the total amount of oil, work with a load pressure higher than the relief pressure of the third pump P ₃ and lower than the relief pressure of the first pump P ₁ and the second pump P _2. If, operating speed pressurized oil from the third pump P ₃ is accidentally relief outlet is delayed, but by setting the above, it is possible to avoid such a problem in advance.
[0032]
[Running]
When the traveling section is used without using the front working section, as shown in FIG. 5, pressure is generated in the pilot oil passage a ₁ and the passage switching valve V ₁₃ is switched to supply the oil passage f and the pressure oil supply. The communication with the oil passage b is cut off, and the oil passage f enters a drained state where it communicates with the drain oil passage d, and the pressure oil from the first pump P ₁ and the second pump P ₂ runs independently to the right. It is supplied only to the section of the hydraulic motor MR for left side and the section of the hydraulic motor ML for left running.
[0033]
In this case, pressure of the oil passage f located upstream of the flow path switching valve V ₁₃ is, because it is detected as a pump discharge pressure PPS at this time, when the flow path switching valve V ₁₃ is switched to the oil discharge state oil The pressure of the passage f, that is, the pump discharge pressure PPS in the load sensing system becomes zero, and the swash plate angle is controlled so that the first pump P ₁ and the second pump P ₂ discharge the maximum flow rate.
[0034]
[Running / Working]
[0035]
When the front working device 9 is operated while traveling, pressure is generated in the pilot oil passage a ₁ and the flow path switching valve V ₁₃ is switched to the oil-removed state, and pressure oil is supplied from the traveling section to the front working section. There is blocked, only the pressure oil from the third pump P ₃ is supplied to the section for the front working.
[0036]
In this example, an auto-idling control system that automatically operates the accelerator device of the engine 3 is provided. That is, as shown in FIG. 1, the governor 21 of the engine 3 is operated by an electric actuator 22, and a potentiometer provided in the control unit 4 is added to a control device 23 that controls the operation of the electric actuator 22. Is connected to a pressure switch 25 arranged to detect the pressure increase of any one of the pilot oil passages a ₁ , a ₂ , and a _3. The driver sets the accelerator setting device 24. The accelerator setting at the time of work is made by setting arbitrarily. In a state where all of the control valves V _{1 to} V ₉ are in a neutral state, the pressure switch 25 does not perform a pressure sensitive operation because all of the pilot oil passages a ₁ , a ₂ , and a ₃ are drained. In this state, the governor 21 is automatically accelerator-down controlled by the electric actuator 22 to a preset idling position. When any one of the control valves V _{1 to} V ₉ is operated, pressure is generated in one of the pilot oil passages a ₁ , a ₂ , and a ₃ , and this is detected by the pressure switch 25. When the pressure switch 25 is pressure-sensitively operated, the governor 21 is automatically accelerator-up controlled by the electric actuator 22 to the accelerator position set by the accelerator setter 24. In other words, when the front work or non-working is not performed, the engine 3 is automatically rotated to a predetermined idling speed to reduce noise and improve fuel efficiency. When it is performed, the rotational speed of the engine 3 is automatically increased to the set rotational speed, and the required hydraulic power is supplied to perform desired work or traveling efficiently.
[0037]
[Another embodiment]
[0038]
In the above embodiment, the pressure of the operation detection oil passage a ₁ formed in the control valve is used as means for switching the pilot-operated flow passage switching valve V _{13 according} to the OR logic according to the operating state of the traveling section. and that, but if those pilot operated is used to control valves for driving, switching operation of the flow path switching valve V ₁₃ in OR logic with the pilot pressure itself applied to the control valve via a pilot valve It is also possible to configure it. Further, by using an electromagnetic valve in the flow path switching valve V _13, it is possible to constitute an OR logic in the electrical circuit.
[Brief description of the drawings]
[Fig. 1] Overall side view of backhoe [Fig. 2] Overall hydraulic circuit diagram [Fig. 3] Hydraulic circuit diagram with a part omitted [Fig. 4] Hydraulic circuit diagram of load sensing system [Fig. 5] Only running Hydraulic circuit diagram in the state of being [Explanation of symbols]
P ₁ First pump P ₂ Second pump P ₃ Third pump V ₁₃ Flow path switching valve

Claims (2)

The pressure oil from the first pump and the second pump is independently supplied to the left and right traveling sections, and the oil that passes through the center bypass of the control valve that controls the left and right traveling sections is merged. It can be supplied to the section, and the flow path can be switched between the pressure oil supply state that supplies the pressure oil that passes through the section for left and right running to the section for the front work device, and the drain oil state that drains the pressure oil. A valve,
Pressurized oil from the third pump, via a section for pivoting the section for the front work device, configured to always supplied in a state of not using the section for turning,
A load sensing system that controls the flow rate of the first pump and the second pump according to the detected load of the front working system is provided, and the circuit pressure at the upstream portion of the flow path switching valve is detected as the discharge pressure of the load sensing system. A hydraulic circuit structure of a backhoe characterized by being configured.   When it is detected that the left and right traveling sections are not in operation, the flow path switching valve is switched to the pressure oil supply state, and it is detected that at least one of the left and right traveling sections is in an operating state. 2. The backhoe hydraulic circuit structure according to claim 1, wherein the hydraulic circuit structure is configured to be switched to the discharged oil state.

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