JP5896041B2 - Hydraulic circuit and cargo handling vehicle - Google Patents

Description

  The present invention relates to an industrial vehicle such as a forklift mainly equipped with a cargo handling device, in particular, a hydraulic circuit used for a cargo handling vehicle, and a cargo handling vehicle equipped with such a hydraulic circuit.

  Conventionally, in an industrial vehicle such as a forklift equipped with a cargo handling device, particularly a cargo handling vehicle, as shown in FIG. 4, the hydraulic pump a2 that is a hydraulic pressure supply source and the hydraulic fluid from the hydraulic pump a2 are given priority. A diversion valve a4 for supplying surplus hydraulic fluid to the steering actuator a8 while supplying the steering a5, a flow rate adjusting valve a6 provided between the diversion valve a4 and the cargo handling actuator a8, and the hydraulic fluid are stored. For this purpose, a hydraulic circuit a1 including a passage a9 connecting the tank a7 to the cargo handling actuator a8 through the hydraulic pump a2, the diversion valve a4 and the flow rate adjusting valve a6 is widely used.

  By the way, the flow rate of the hydraulic fluid from the hydraulic pump is proportional to the rotational speed of the hydraulic pump. Further, when the cargo handling operation is not performed, the surplus hydraulic fluid is returned to the tank through the flow rate adjustment valve. At this time, when a hydraulic circuit having only one hydraulic pump is used, as shown in FIG. 5, the entire amount of hydraulic fluid discharged from the pump is circulated through the diverter valve a4 with the hydraulic pressure supplied to the steering. Will be. That is, when the cargo handling operation is not performed, the amount of hydraulic fluid corresponding to the area shown by the oblique lines in FIG. 5 flows unnecessarily through the diversion valve a4, and the power loss accompanying the pressure loss increases. That is, energy is wasted.

As a configuration for reducing such waste, there are a plurality of hydraulic pumps, for example, a first hydraulic pump b2 and a second hydraulic pump b3 as shown in FIG. A hydraulic circuit b1 having the following is considered. The hydraulic circuit b1 preferentially supplies the first hydraulic pump b2 and the second hydraulic pump b3, which are hydraulic supply sources, and the hydraulic fluid from the hydraulic pumps b2 and b3 to the steering b5. And a flow dividing valve b4 for supplying surplus hydraulic fluid to the cargo handling actuator b8, a flow rate adjusting valve b6 provided between the flow dividing valve b4 and the cargo handling actuator b8, and a tank for storing the hydraulic fluid a main passage b9 that connects the first hydraulic pump b2, the flow dividing valve b4 and the flow rate adjusting valve b6 to the cargo handling actuator b8, the tank b7 of the main passage b9, and the first passage b9. A sub-passage b10 that branches from the fluid pressure pump b2 and passes through the second fluid pressure pump b3 and joins the main passage b9 again between the flow dividing valve b4 and the flow rate control valve b6 is provided. In such a hydraulic circuit b1, when the first and second hydraulic pumps b2 and b3 are rotating at the minimum number of rotations n _min , a minimum amount of hydraulic fluid can be supplied to the steering b5. The capacity of the first hydraulic pump b2 can be set as much as possible, and the amount of liquid passing through the flow dividing valve b4 can be reduced as compared with the configuration described in the previous stage.

  However, even in such a configuration, when the rotational speed is high, the amount of hydraulic fluid discharged from the first hydraulic pump b2 and passing through the flow dividing valve b4 is large, and the above-described cargo handling operation is not performed. 5, the amount of hydraulic fluid corresponding to the area shown by the oblique lines in FIG. 5 circulates unnecessarily through the diverter valve b4, and the power loss accompanying the pressure loss is still large, resulting in a waste of energy.

JP 2010-76937 A

  The present invention pays attention to the above points, and in a hydraulic circuit used for an industrial vehicle such as a forklift equipped with a cargo handling device, particularly a cargo handling vehicle, the power loss accompanying the pressure loss when the cargo handling operation is not performed is greatly reduced. The purpose is to plan.

  In order to solve the above problems, the hydraulic circuit according to the present invention has a configuration as described below. That is, the hydraulic circuit according to the present invention supplies a plurality of hydraulic pumps, which are hydraulic supply sources, and supplies hydraulic fluid from these hydraulic pumps preferentially to the steering and supplies surplus hydraulic fluid to the cargo handling actuator. And a flow control valve provided between the flow dividing valve and the cargo handling actuator, wherein the plurality of hydraulic pumps include one main pump and at least one hydraulic pump. Two sub-pumps, and further provided when the discharge flow rate of the main pump is less than a predetermined discharge flow rate provided between the sub-pump and the diversion valve, or when the rotation speed of the main pump is lower than the predetermined rotation rate A first state in which the hydraulic fluid from the main pump is led to the upstream side of the flow dividing valve and the discharge flow rate of the main pump exceeds a predetermined discharge flow rate; When the rotational speed of the pump exceeds a predetermined rotational speed, there is provided a switching valve that takes a second state that guides the hydraulic fluid from the sub-pump to a bypass passage that joins downstream of the diverter valve and upstream of the flow regulating valve. Yes.

  In order to solve the above-described problem, the cargo handling vehicle according to the present invention includes the hydraulic circuit described in the previous section.

  If it is such, the rotation speed of the main pump which can ensure the predetermined flow volume of the hydraulic fluid required for steering only by the hydraulic fluid from the main pump is set to the predetermined rotation speed, and the discharge flow rate of the main pump is When the flow rate is lower than the predetermined discharge flow rate or when the rotation speed of the main pump is lower than the predetermined rotation speed, the switching valve is set to the first state, so that the hydraulic pump that is not connected to the bypass passage, that is, the main pump Even if the volume is reduced, the flow rate of the hydraulic fluid supplied to the steering can be secured. On the other hand, since the capacity of the main pump can be reduced, when the cargo handling operation is not performed and the rotational speed of the hydraulic pump is high, the switching valve is set to the second state, thereby diverting the flow compared to the conventional one. The amount of hydraulic fluid that passes through the valve can be greatly reduced, and therefore, the power loss accompanying the pressure loss when the cargo handling operation is not performed can be greatly reduced.

  ADVANTAGE OF THE INVENTION According to this invention, in industrial vehicles, such as a forklift provided with a cargo handling apparatus, especially the hydraulic circuit used for a cargo handling vehicle, it can aim at the significant reduction of the power loss accompanying the pressure loss when not performing cargo handling work. .

The circuit diagram which shows the hydraulic circuit which concerns on one Embodiment of this invention. The figure which shows the relationship between the rotational speed of the hydraulic pump which concerns on the embodiment, and the flow volume of the hydraulic fluid which shows the shunt valve of a hydraulic circuit. The circuit diagram which shows the hydraulic circuit which concerns on other embodiment of this invention. The circuit diagram which shows the conventional hydraulic circuit. The figure which shows the relationship between the rotational speed of the hydraulic pump in the hydraulic circuit shown in FIG. 4, and the flow volume of the hydraulic fluid which shows the shunt valve of a hydraulic circuit. The circuit diagram which shows the conventional hydraulic circuit. The figure which shows the relationship between the rotational speed of the hydraulic pump in the hydraulic circuit shown in FIG. 6, and the flow volume of the hydraulic fluid which shows the shunt valve of a hydraulic circuit.

  An embodiment of the present invention will be described below with reference to FIGS.

The hydraulic circuit 1 of the present embodiment is mounted on a cargo handling vehicle. As shown in FIG. 1, two hydraulic pumps that are hydraulic supply sources, that is, a main pump 2 and a sub pump 3, and these liquids The flow dividing valve 4 for supplying the hydraulic fluid from the pressure pump, that is, the main pump 2 and the sub pump 3 preferentially to the steering 5 and supplying the excess hydraulic fluid to the cargo handling actuator 8, and the flow dividing valve 4 and the cargo handling actuator A main flow rate control valve 6 provided between the main pump 2, the flow dividing valve 4 and the flow rate adjustment valve 6 to the cargo handling actuator 8 from a tank 7 for storing hydraulic fluid. The main pump 2 and the diversion valve of the main passage 9 branch from the passage 9 and between the tank 7 of the main passage 9 and the main pump 2 and pass through the sub pump 3. Between the first sub-passage 10 that joins the main passage 9 again, and between the sub-pump 3 and the diversion valve 4 in the first sub-passage 10, and the diversion valve 4 in the main passage 9. A second sub-passage 11 that joins the main passage 9 with the flow rate adjusting valve 6 and a portion where the second sub-passage 11 branches from the first sub-passage 10 are provided in the main pump 2. When the rotational speed is lower than the predetermined rotational speed n ₁ , the first state in which the hydraulic fluid from the sub pump 3 is guided to the upstream side of the flow dividing valve 4 is taken and the rotational speed of the main pump 2 exceeds the predetermined rotational speed n ₁ . In this case, a switching valve 12 is provided which takes a second state for guiding the hydraulic fluid from the sub pump 3 to the second sub passage 11. Here, the second sub-passage 11 is a bypass passage in the claims.

The main pump 2 and the sub pump 3 are both connected to a vehicle driving engine or motor, which is a power source (not shown), and are fixed capacity pumps having a known configuration that rotate in conjunction with each other at the same rotational speed. Here, the rotation speeds of the main pump 2 and the sub pump 3 are between the minimum rotation speed n _min and the maximum rotation speed n _max .

  The diversion valve 4 is used for a forklift or the like, and has the same configuration as a well-known priority valve mechanism that supplies hydraulic fluid to the steering 5 and the cargo handling actuator 8. That is, the diversion valve 4 gives priority to the input port 4a serving as an inlet for the high-pressure hydraulic fluid discharged from the main pump 2 and the sub pump 3 and the hydraulic fluid necessary for the operation of the steering 5 and discharges it toward the steering 5. And a surplus flow output port 4c that discharges surplus hydraulic fluid toward the cargo handling actuator 8. The hydraulic fluid discharged from the surplus flow output port 4 c is guided to the cargo handling actuator 8 through the flow rate adjusting valve 6.

  The flow rate adjusting valve 6 has a function of adjusting the amount of hydraulic fluid guided to the cargo handling actuator 8 by changing the opening degree in response to an operation received by an operation lever (not shown).

Then, the switching valve 12, as described above, is provided between the diverter valve 4 and the subordinate fuel pump 3, when the rotational speed of the main pump 2 is below a predetermined rotational speed n _1, i.e. discharge from the main pump 2 When the flow rate is lower than the predetermined discharge flow rate f _min that is the minimum flow rate required to operate the steering 5, the hydraulic fluid from the sub pump 3 passes through the first sub passage 10 to the upstream side of the flow dividing valve 4. In the first state of guiding, when the rotational speed of the main pump 2 exceeds the predetermined rotational speed n ₁ , the hydraulic fluid from the sub-pump 3 passes through the second sub-passage 11 downstream of the flow dividing valve 4 and the flow rate is adjusted. A second state of leading to the upstream side of the valve 6 is taken. Here, the discharge flow rate of the hydraulic fluid from the main pump 2 is substantially proportional to the rotational speed of the main pump 2. That is, at the predetermined rotational speed n ₁ , the flow rate of the hydraulic fluid discharged from the main pump 2 becomes substantially equal to the predetermined discharge flow rate f _min . The switching valve 12 includes a coil spring 12a that is an urging means for urging to take the first state and a urging force of the coil spring 12a when electric power is supplied. 2 is built in, and this solenoid 12b is connected to a control device (not shown) to be described later. This control device is formed by connecting a microcomputer system having a CPU, a storage device, and an input / output interface and a rotation speed sensor for detecting the rotation speed of the engine or motor, and outputs the rotation speed sensor. When the rotation speed indicated by the signal exceeds the predetermined rotation speed n ₁ , the solenoid 12b is energized and the switching valve 12 is controlled to be in the second state.

Here, the relationship between the rotational speed of the main pump 2 and the flow rate passing through the flow dividing valve 4 will be described with reference to FIG. 2. When the rotational speed falls below the predetermined rotational speed n ₁ , switching is performed as described above. Since the valve 12 is in the first state, the hydraulic fluid discharged from the main pump 2 and the sub pump 3 passes through the flow dividing valve 4. Accordingly, the flow rate passing through the diversion valve 4 is as shown by the solid line D1 + D2 in FIG. On the other hand, when the rotational speed exceeds the predetermined rotational speed n ₁ , the switching valve 12 takes the second state as described above, so that only the hydraulic fluid discharged from the main pump 2 passes through the flow dividing valve 4. . Accordingly, the flow rate passing through the diversion valve 4 is as shown by the broken line D1 in FIG. At this time, the flow rate of the hydraulic fluid discharged from the main pump 2 exceeds the minimum flow rate necessary for operating the steering 5, that is, the predetermined discharge flow rate f _min .

In other words, according to the present embodiment, in the region where the rotational speed is high as compared with the conventional hydraulic circuit a1 that uses only one hydraulic pump a2 described with reference to FIGS. The flow rate of the hydraulic fluid passing through 4 can be greatly reduced. More specifically, when the cargo handling operation is not performed, the amount of the hydraulic fluid that circulates unnecessarily through the flow dividing valve 4 is an amount corresponding to the area shown by the oblique lines in FIG. 2, and the rotational speed is the predetermined rotational speed n _1. 2, that is, in a region where the flow rate of the hydraulic fluid discharged from the main pump 2 exceeds the predetermined discharge flow rate f _min , a region X between the extended portion of the solid line D1 + D2 in FIG. 2 and the broken line D1 in FIG. Thus, the amount of hydraulic fluid that flows unnecessarily through the flow dividing valve 4 can be reduced by an amount corresponding to. Compared with the conventional hydraulic circuit 1 described with reference to FIGS. 6 and 7, since the main pump 2 and the sub pump 3 are used in the vicinity of the minimum rotation speed n _min , the hydraulic fluid from the main pump 2 is used. Therefore, it is not necessary to secure the minimum flow rate f _min necessary for operating the steering 5 alone, and the capacity of the main pump 2 can be reduced. Therefore, the flow rate of the working fluid that passes through the flow dividing valve 4 in the high rotation speed region Can be greatly reduced. That is, as compared with the conventional hydraulic circuit 1, the power loss due to the pressure loss at which the hydraulic fluid passes through the diverter valve 4 can be suppressed by significantly reducing the flow rate of the hydraulic fluid that passes through the diverter valve 4. And energy waste due to this power loss can be greatly reduced.

  In addition, this invention is not restricted to the Example mentioned above.

  For example, as shown in FIG. 3, the first state in which the working fluid that has passed through the sub pump 3 is guided to the tank 7 through the tank passage 14 in the bypass passage, that is, the second sub passage 11, and the operation that has passed through the sub pump 3. You may provide the 2nd switching valve 13 which can take the 2nd state which guide | induces a liquid to the upstream of the flow regulating valve 6. FIG. The second switching valve 13 has a coil spring 13a which is a biasing means for biasing to take the first state, and a biasing force of the coil spring 13a when electric power is supplied. The solenoid 13b for making it a 2nd state is built in, and this solenoid is connected to the control apparatus mentioned later. This control device is formed by connecting a microcomputer system having a CPU, a storage device, and an input / output interface, and a rotation speed sensor (not shown) that detects the rotation speed of the engine or motor, and performs a cargo handling operation. If it is not, the solenoid 13b is energized to control the switching valve 13 in the second state. Since the hydraulic circuit 1 shown in FIG. 3 has the same configuration as the hydraulic circuit 1 shown in FIGS. 1 and 2 in other points, the corresponding parts are denoted by the same names and symbols, and the details are as follows. Detailed explanations are omitted.

  With such a configuration, when the cargo handling operation is not performed, the hydraulic fluid that has passed through the sub pump 3 can be guided to the tank 7 with no load, and therefore the pressure loss at which the hydraulic fluid passes through the flow rate adjustment valve 6. It is also possible to suppress power loss associated with. And waste of energy due to this power loss can be further reduced.

  Further, the present invention may be applied to a hydraulic circuit having a plurality of sub pumps.

  In addition, in the above-described embodiment, a fixed displacement pump is used as the main pump and the sub pump, and attention is paid to the fact that the rotational speed and the discharge flow rate are substantially proportional. When the rotational speed is lower than the predetermined rotational speed, the switching valve is The first state is such that the hydraulic fluid from the sub pump is guided to the upstream side of the flow dividing valve, and the switching valve guides the hydraulic fluid from the sub pump to the bypass passage when the rotational speed exceeds a predetermined rotational speed. When the discharge flow rate of the hydraulic fluid from the main pump is directly detected using flow rate detection means such as a flow rate sensor, and the detected discharge flow rate of the hydraulic fluid is lower than the predetermined discharge flow rate When the switching valve is in a first state in which the hydraulic fluid from the sub-pump is guided to the upstream side of the flow dividing valve, and the detected hydraulic fluid discharge flow rate exceeds a predetermined discharge flow rate Kawaben may be adopted a configuration in which to take a second state to direct the hydraulic fluid from the sub pump to the bypass passage.

  In addition, various changes may be made without departing from the spirit of the present invention.

  By adopting the configuration of the present invention, in a hydraulic circuit used in an industrial vehicle such as a forklift equipped with a cargo handling device, in particular, a cargo handling vehicle, the power loss accompanying the pressure loss when the cargo handling operation is not performed is greatly reduced. be able to.

1 ... Hydraulic circuit 2 ... Main pump (Hydraulic pump)
3. Sub pump (hydraulic pump)
4 ... Branch valve 6 ... Flow control valve 11 ... Bypass passage (second auxiliary passage)
12 ... Switching valve

Claims (2)

A plurality of hydraulic pumps that are hydraulic pressure supply sources, a diverter valve for preferentially supplying hydraulic fluid from these hydraulic pumps to the steering and supplying excess hydraulic fluid to the cargo handling actuator, and the diverter valve And a flow control valve provided between the cargo handling actuator, the hydraulic pump having one main pump and at least one sub-pump as the plurality of hydraulic pumps, and the sub-pump When the discharge flow rate of the main pump is lower than a predetermined discharge flow rate or when the rotation speed of the main pump is lower than the predetermined rotation speed, the hydraulic fluid from the sub pump is upstream of the flow distribution valve. And when the discharge flow rate of the main pump exceeds a predetermined discharge flow rate or the rotation speed of the main pump is a predetermined rotation speed A fluid pressure circuit comprising a switching valve that takes a second state to guide the hydraulic fluid from the sub-pump to a bypass passage that joins the downstream side of the flow dividing valve and the upstream side of the flow rate adjusting valve when exceeding . A plurality of hydraulic pumps that are hydraulic pressure supply sources, a diverter valve for preferentially supplying hydraulic fluid from these hydraulic pumps to the steering and supplying excess hydraulic fluid to the cargo handling actuator, and the diverter valve A cargo handling vehicle equipped with a hydraulic pressure circuit having a flow rate adjustment valve provided between the cargo handling actuator and the cargo handling actuator, wherein the plurality of hydraulic pressure pumps include one main pump and at least one sub pump. Furthermore, when the discharge flow rate of the main pump provided between the sub pump and the diversion valve is lower than a predetermined discharge flow rate or when the rotation speed of the main pump is lower than the predetermined rotation speed, the working fluid from the sub pump is discharged. When the first state leading to the upstream side of the flow dividing valve is taken and the discharge flow rate of the main pump exceeds a predetermined discharge flow rate, or the rotation of the main pump A switching valve that takes a second state in which the hydraulic fluid from the sub-pump is led to a bypass passage that joins the downstream side of the flow dividing valve and the upstream side of the flow rate adjusting valve when the degree of rotation exceeds a predetermined rotational speed. A characteristic cargo handling vehicle.

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