Electric control hydraulic system and forklift

Abstract

The electric control hydraulic system comprises a motor, a hydraulic pump connected with the motor, a control valve, an oil tank and a controller electrically connected with the motor, an oil inlet of the hydraulic pump is communicated with the oil tank, an oil outlet of the hydraulic pump is communicated with an oil inlet of the control valve, and a working oil port of the control valve is connected with an actuator; the first pressure sensor is connected to the upstream side of the control valve, the second pressure sensor is connected to the downstream side of the control valve, and the pressure signal output end of the first pressure sensor and the pressure signal output end of the second pressure sensor are connected with the controller. And the controller controls the rotating speed of the motor according to the pressure signal. The rotating speed of the motor can be adaptively controlled, so that the output flow of the hydraulic pump achieves the effect similar to that of a variable pump, energy loss caused by redundant flow bypass is avoided, on-demand flow supply is truly realized, and the energy consumption of a system is greatly reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of hydraulic pressure, in particular to an electric control hydraulic system and a forklift truck. Background Art

[0002] The currently used load sensing system mainly uses a three-way pressure compensator (load sensing valve) to achieve the purpose of accurate and stable speed without changing with the load, and is mainly applied to a fixed displacement pump hydraulic system. When the fixed displacement pump is at a fixed speed or the hydraulic oil output by the fixed displacement pump is more than that required by the actuator, the hydraulic oil output by the fixed displacement pump is greater than the required hydraulic oil. Part of the hydraulic oil enters the actuator, and the excess hydraulic oil returns to the hydraulic oil tank from the bypass of the load sensing valve. Since the excess hydraulic oil needs to overcome the spring force of the load sensing valve to return to the hydraulic oil tank, the hydraulic system will generate excess useless energy consumption and heat the hydraulic oil. For an electric counterbalanced forklift truck, the increased energy consumption means reduced endurance, increased charging times, and affects the use. Summary of the Utility Model

[0003] Aiming at the technical problems existing in the prior art, the utility model provides an electric control hydraulic system and a forklift truck, which can supply oil on demand, do not need to use a load sensing valve, and effectively avoid the energy consumption loss caused by the excess flow passing through the load sensing valve.

[0004] The technical solution adopted by the utility model to solve its technical problems is: an electric control hydraulic system, including a motor, a hydraulic pump connected to the motor, a control valve, an oil tank, and a controller electrically connected to the motor. The oil inlet of the hydraulic pump is communicated with the oil tank, the oil outlet of the hydraulic pump is communicated with the oil inlet of the control valve, and the working oil port of the control valve is connected to the actuator; it also includes a first pressure sensor connected to the upstream side of the control valve and a second pressure sensor connected to the downstream side of the control valve. The pressure signal output ends of the first pressure sensor and the second pressure sensor are respectively connected to the controller, so that the controller controls the rotation speed of the motor according to the pressure signal.

[0005] Further, the control valve is a multi-way valve, which includes a plurality of direction valves. The oil inlets of the respective direction valves are respectively communicated with the oil outlet of the hydraulic pump, the working oil ports of the respective direction valves are respectively connected to the corresponding actuators, and the oil return ports of the respective direction valves are respectively communicated with the oil tank; the pressure detection port of the first pressure sensor is connected to the oil outlet of the hydraulic pump, and the pressure detection port of the second pressure sensor is connected to the pressure feedback oil port of the direction valve.

[0006] Further, the number of the second pressure sensors is multiple, and the multiple second pressure sensors correspond to the multiple direction valves one by one.

[0007] Further, the number of the second pressure sensors is one. The pressure detection port of the second pressure sensor is connected to the pressure feedback oil ports of each directional valve through one or more shuttle valves. The pressure detection port of the second pressure sensor is located on the downstream side of the shuttle valve, and the pressure feedback oil port of the directional valve is located on the upstream side of the shuttle valve. At least two of the multiple shuttle valves are connected in series.

[0008] Further, the multi-way valve further includes a main safety valve. The oil inlet of the main safety valve is communicated with the oil outlet of the hydraulic pump, and the oil outlet of the main safety valve is communicated with the fuel tank. The multi-way valve further includes an Ls safety valve. The oil inlet of the Ls safety valve is connected to the pressure feedback oil ports of each directional valve through a shuttle valve, and the oil outlet of the Ls safety valve is communicated with the fuel tank.

[0009] Further, among the multiple directional valves, one directional valve is a lifting directional valve, and the actuator connected to the working oil port of the lifting directional valve is a lifting oil cylinder for controlling the lifting of the forklift's fork. One directional valve is a tilting directional valve, and the actuator connected to the working oil port of the tilting directional valve is a tilting oil cylinder for controlling the front and rear tilting of the forklift's mast.

[0010] Further, the multi-way valve is a load-sensitive multi-way valve.

[0011] Further, the hydraulic pump is a gear pump, and the controller is an ECU controller.

[0012] The present invention further provides a forklift, including the electro-hydraulic control system as described in the above-mentioned present invention.

[0013] Further, the forklift is an electric counterbalanced forklift.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. Since the present invention further includes a first pressure sensor connected to the upstream side of the control valve and a second pressure sensor connected to the downstream side of the control valve, the pressure signal output ends of the first pressure sensor and the second pressure sensor are respectively connected to the controller, so that the controller controls the rotation speed of the motor according to the pressure signal. Therefore, the present invention can adaptively control the rotation speed of the motor, making the hydraulic pump output flow reach the effect of a variable pump, thus eliminating the energy loss caused by the bypass of redundant flow, truly realizing the on-demand supply of flow, greatly reducing the energy consumption of the system, and improving the endurance of the electric counterbalanced forklift.

[0016] 2. The present invention uses the first pressure sensor and the second pressure sensor to replace the flow compensation valve structure of the traditional load-sensitive valve, simplifying the structure of the control valve.

[0017] 3. The flow rate output by each directional valve is only related to the opening degree and area of the spool, is not affected by the load, and has high control accuracy.

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments; however, an electro-hydraulic control system and a forklift of the present invention are not limited to the embodiments. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of the first embodiment of the present invention;

[0020] Figure 2 is a schematic structural diagram of the second embodiment of the present invention;

[0021] 1. Gear pump, 2. Motor, 3. First pressure sensor, 4. Lifting cylinder, 5. Tilt cylinder, 6. Load sensing multi-way valve, 61. Main safety valve, 62. Lifting directional valve, 63. Tilt directional valve, 64. Shuttle valve, 65. Ls safety valve, 7. Second pressure sensor, 8. Controller, 9. Fuel tank. Detailed Embodiment

[0022] In the present invention, for terms such as "first" and "second", they are only used to distinguish similar objects, rather than to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. Additionally, in the description of the present invention, unless otherwise stated, "a plurality of" means two or more. In the description of the present invention, unless otherwise clearly defined and limited, the term "connection" should be understood in a broad sense. It can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium. It can be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] Embodiment 1

[0024] Please refer to Figure 1As shown in the figure, an electro-hydraulic control system of the present utility model includes a motor 2, a hydraulic pump connected to the motor 2, a control valve, an oil tank 9, and a controller 8 electrically connected to the motor 2. The hydraulic pump is specifically a gear pump 1, whose inlet is communicated with the oil tank 9, and the outlet of the hydraulic pump is communicated with the inlet of the control valve. The working oil port of the control valve is connected to an actuator. The present utility model further includes a first pressure sensor 3 connected to the upstream side of the control valve and a second pressure sensor 7 connected to the downstream side of the control valve. The controller 8 is preferably an ECU controller. The pressure signal output terminals of the first pressure sensor 3 and the second pressure sensor 7 are respectively connected to the controller 8, so that the controller 8 controls the rotation speed of the motor 2 according to the pressure signal. Specifically, the controller 8 controls the rotation speed of the motor 2 according to the magnitude of the difference between the two pressure signals. The greater the difference, the lower the rotation speed of the motor; the smaller the difference, the higher the rotation speed of the motor. In other embodiments, the controller 8 controls the rotation speed of the motor 2 according to the magnitude of the average value of the two pressure signals, etc.

[0025] In this embodiment, the control valve is a multi-way valve, specifically a load-sensing multi-way valve 6, which includes a plurality of directional valves. The inlet of each directional valve is respectively communicated with the outlet of the hydraulic pump (i.e., the gear pump 1), the working oil port of each directional valve is respectively connected to a corresponding actuator, and the oil return port of each directional valve is respectively communicated with the oil tank 9. The pressure detection port of the first pressure sensor 3 is connected to the outlet of the hydraulic pump (i.e., the gear pump 1), and the pressure detection port of the second pressure sensor 7 is connected to the pressure feedback oil port of the directional valve.

[0026] The number of the above-mentioned directional valves is specifically two, but not limited thereto. The two directional valves are respectively a lifting directional valve 62 and a tilting directional valve 63. The actuator connected to the working oil port of the lifting directional valve 62 is a lifting cylinder 4 for controlling the lifting of the forklift's fork, and the actuator connected to the working oil port of the tilting directional valve 63 is a tilting cylinder 5 for controlling the front and rear tilting of the forklift's mast.

[0027] In this embodiment, the number of the second pressure sensors 7 is one. The pressure detection port of the second pressure sensor 7 is connected to the pressure feedback oil ports of each directional valve through one or more shuttle valves 64. The pressure detection port of the second pressure sensor 7 is located on the downstream side of the shuttle valve 64, and the pressure feedback oil port of the directional valve is located on the upstream side of the shuttle valve 64. Since the number of the directional valves is two, in this embodiment, the number of the shuttle valves 64 is one. One of the inlets of the shuttle valve 64 is connected to the pressure feedback oil port of the lifting directional valve 62, and the other inlet of the shuttle valve 64 is connected to the pressure feedback oil port of the tilting directional valve 63. The outlet of the shuttle valve 64 is connected to the pressure detection port of the second pressure sensor 7. In other embodiments, if the number of the directional valves is more than two, then the number of the shuttle valves is multiple. At this time, at least two of the multiple shuttle valves are connected in series. Connecting two shuttle valves in series means that one of the outlets of one shuttle valve is connected to one of the inlets of the other shuttle valve. For example, when the number of the directional valves is three, two shuttle valves can be used. These two shuttle valves are respectively named the first shuttle valve and the second shuttle valve. The two inlets of the first shuttle valve are respectively connected to the pressure detection ports of two of the directional valves. The outlet of the first shuttle valve and the pressure detection ports of the remaining directional valves are respectively connected to the two inlets of the second shuttle valve. The outlet of the second shuttle valve is connected to the pressure detection port of the second pressure sensor.

[0028] As Figure 1 shown, the multi-way valve (i.e., the load-sensing multi-way valve 6) of the present utility model further includes a main safety valve 61 for limiting the maximum pressure of the hydraulic system. The inlet of the main safety valve 61 is communicated with the outlet of the hydraulic pump (i.e., the gear pump 1), and the outlet of the main safety valve 61 is communicated with the oil tank 9. The multi-way valve (i.e., the load-sensing multi-way valve 6) of the present utility model further includes an Ls safety valve 65 for limiting the load feedback pressure. The inlet of the Ls safety valve 65 is connected to the pressure feedback oil ports of each directional valve through the shuttle valve 64, and the outlet of the Ls safety valve 65 is communicated with the oil tank 9. The shuttle valve 64 connected to the Ls safety valve 65 is the same shuttle valve 64 as that connected to the above-mentioned second pressure sensor 7.

[0029] The working principle of an electro-hydraulic control system of the present utility model is as follows:

[0030] When the lifting directional valve 62 and the tilting directional valve 63 are in the neutral position, the pressure at the shuttle valve 64 tends to zero, and the second pressure sensor 7 outputs no pressure signal to the controller 8. If the motor 2 drives the gear pump 1 to rotate and output flow at this time, since the second pressure sensor 7 outputs no pressure signal, the controller 8 controls the motor 2 to gradually stop rotating, so that the gear pump 1 does not output flow.

[0031] When the lift direction valve 62 or the tilt direction valve 63 is actuated, the load pressure is fed back to the shuttle valve 64 through the internal pressure feedback passage of the lift direction valve 62 or the tilt direction valve 63. The load pressure is fed back to the second pressure sensor 7 through the shuttle valve 64. The second pressure sensor 7 outputs a pressure signal to the controller 8, and the first pressure sensor 3 also outputs the detected pressure signal to the controller 8. The controller 8 automatically adjusts the rotational speed of the motor 2 according to the magnitude of the difference between the pressure signals transmitted by the first pressure sensor 3 and the second pressure sensor 7: when the difference between the pressure at the upstream (pump end) and the downstream (load end) of the load-sensitive multi-way valve 6 is less than the preset value, the controller 8 controls the rotational speed of the motor 2 to increase; otherwise, the rotational speed of the motor 2 decreases; when the difference between the pressure at the upstream (pump end) and the downstream (load end) of the load-sensitive multi-way valve 6 reaches the set value, the rotational speed of the motor 2 no longer increases. As the opening of the valve stem of each direction valve changes, the controller 8 controls the change in the rotational speed of the motor 2 and always maintains a constant difference between the pressure at the upstream (pump end) and the downstream (load end) of the load-sensitive multi-way valve 6. Therefore, the flow rate output by each direction valve is only related to the opening and area of the spool and is not affected by the load, with high control accuracy.

[0032] Therefore, the controller 8 of the present utility model can adaptively control the rotational speed of the motor 2, so that the flow rate output by the gear pump 1 achieves the effect similar to that of a variable pump, without energy loss caused by redundant flow bypass, truly realizing the on-demand supply of flow rate, greatly reducing the energy consumption of the system, and improving the endurance of the electric counterbalanced forklift.

[0033] Embodiment 2

[0034] Please refer to Figure 2 As shown, an electro-hydraulic control system of the present utility model is different from the above Embodiment 1 in that: the present utility model includes a plurality of second pressure sensors 7, and the plurality of second pressure sensors 7 correspond to the plurality of direction valves one by one.

[0035] In this embodiment, the number of direction valves is two. Therefore, the present utility model includes two second pressure sensors 7, but is not limited thereto. The two direction valves are respectively a lift direction valve 62 and a tilt direction valve 63. The actuator connected to the working oil port of the lift direction valve 62 is a lift cylinder 4 for controlling the lifting and lowering of the forklift's forks, and the actuator connected to the working oil port of the tilt direction valve 63 is a tilt cylinder 5 for controlling the front-back tilt of the forklift's mast.

[0036] Among the two second pressure sensors 7, the pressure detection port of one of the second pressure sensors 7 is connected to the pressure feedback oil port of the lift direction valve 62, and the pressure detection port of the other second pressure sensor 7 is connected to the pressure feedback oil port of the tilt direction valve 63.

[0037] In this embodiment, the control valve is specifically a load-sensitive multi-way valve 6, which further includes a main safety valve 61 and an Ls safety valve 65. The oil inlet of the main safety valve 61 is connected to the oil outlet of the hydraulic pump (i.e., the gear pump 1), and the oil outlet of the main safety valve 61 is connected to the fuel tank 9; the oil inlet of the Ls safety valve 65 is connected to the pressure feedback oil ports of each directional valve through a shuttle valve 64, and the oil outlet of the Ls safety valve 65 is connected to the fuel tank 9.

[0038] An electro-hydraulic control system of the present utility model has a working principle substantially the same as above, except that: when two second pressure sensors 7 simultaneously output pressure signals to the controller 8, the controller 8 calculates the difference between the pressure signal of the larger load end and the pressure signal of the pump end, and controls the rotational speed change of the motor 2 accordingly, which can also achieve the purpose of supplying flow on demand and reducing system energy consumption.

[0039] A forklift of the present utility model is specifically an electric counterbalanced forklift, which includes the electro-hydraulic control system of the present utility model as described above.

[0040] Regarding the structure and working principle of the electro-hydraulic control system, please refer to the previous description thereof, and details will not be repeated here.

[0041] An electro-hydraulic control system and a forklift of the present utility model, parts not involved are the same as the prior art or can be implemented using the prior art.

[0042] The above embodiments are only used to further illustrate an electro-hydraulic control system and a forklift of the present utility model, but the present utility model is not limited to the embodiments. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present utility model all fall within the protection scope of the technical solution of the present utility model.

Claims

1. An electronically controlled hydraulic system, comprising an electric motor, a hydraulic pump connected to the electric motor, a control valve, an oil tank and a controller electrically connected to the electric motor, wherein the oil inlet of the hydraulic pump is connected to the oil tank, the oil outlet of the hydraulic pump is connected to the oil inlet of the control valve, and the working oil port of the control valve is connected to the actuator; characterized in that: It also includes a first pressure sensor connected to the upstream side of the control valve and a second pressure sensor connected to the downstream side of the control valve. The pressure signal output end of the first pressure sensor and the pressure signal output end of the second pressure sensor are respectively connected to the controller so that the controller controls the speed of the motor according to the pressure signal.

2. The electronically controlled hydraulic system according to claim 1, characterized in that: The control valve is a multi-way valve, which includes multiple directional valves, the oil inlet of each directional valve is connected to the oil outlet of the hydraulic pump, the working oil port of each directional valve is connected to the corresponding actuator, and the oil return port of each directional valve is connected to the oil tank; the pressure detection port of the first pressure sensor is connected to the oil outlet of the hydraulic pump, and the pressure detection port of the second pressure sensor is connected to the pressure feedback oil port of the directional valve.

3. The electronically controlled hydraulic system according to claim 2, characterized in that: There are multiple second pressure sensors, and the multiple second pressure sensors correspond one-to-one to the multiple directional valves.

4. The electronically controlled hydraulic system according to claim 2, characterized in that: The number of the second pressure sensor is one, and the pressure detection port of the second pressure sensor is connected to the pressure feedback oil port of each directional valve through one or more shuttle valves, and the pressure detection port of the second pressure sensor is located on the downstream side of the shuttle valve, and the pressure feedback oil port of the directional valve is located on the upstream side of the shuttle valve; at least two shuttle valves among the multiple shuttle valves are connected in series.

5. The electronically controlled hydraulic system according to claim 2, characterized in that: The multi-way valve also includes a main safety valve, the oil inlet of the main safety valve is connected to the oil outlet of the hydraulic pump, and the oil outlet of the main safety valve is connected to the oil tank; the multi-way valve also includes an Ls safety valve, the oil inlet of the Ls safety valve is connected to the pressure feedback oil ports of each directional valve through a shuttle valve, and the oil outlet of the Ls safety valve is connected to the oil tank.

6. The electronically controlled hydraulic system according to any one of claims 2 to 5, characterized in that: Among the multiple directional valves, one of the directional valves is a lifting directional valve, and the actuator connected to the working oil port of the lifting directional valve is a lifting cylinder used to control the lifting and lowering of the forklift's cargo fork; one of the directional valves is a tilting directional valve, and the actuator connected to the working oil port of the tilting directional valve is a tilting cylinder used to control the forward and backward tilting of the forklift's mast.

7. The electronically controlled hydraulic system according to claim 2, characterized in that: The multi-way valve is a load-sensitive multi-way valve.

8. The electronically controlled hydraulic system according to claim 1, characterized in that: The hydraulic pump is a gear pump, and the controller is an ECU controller.

9. A forklift, characterized in that: Comprising the electronically controlled hydraulic system as claimed in any one of claims 1 to 8.

10. The forklift according to claim 9, characterized in that: The forklift is an electric counterbalance forklift.

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