Steering hydraulic system and fork lift truck

Abstract

The application belongs to the field of industrial vehicles, and discloses a steering hydraulic system and a forklift truck. The steering hydraulic system is sequentially connected in hydraulic pressure to a steering gear, a booster cylinder and a steering oil cylinder. The hydraulic oil at the oil outlet of the steering gear can drive the booster cylinder in hydraulic pressure, and the steering oil cylinder is driven to extend and retract by the booster cylinder. The application adds the booster cylinder between the steering gear and the steering oil cylinder, so that the hydraulic oil with low pressure can drive the steering oil cylinder by driving the booster cylinder, the booster driving effect is realized, the pressure output of the hydraulic system is improved, the steering operation intensity is significantly reduced, the steering is more flexible, the response speed and stability of the system are improved, and the energy utilization efficiency of the hydraulic system is optimized.

Description

Technical Field

[0001] This application belongs to the field of industrial vehicles, and specifically relates to a forklift and its steering hydraulic system. Background Technology

[0002] When a forklift is in operation, the front end is loaded and timely and flexible steering is required. However, under certain conditions, such as idling, large internal leakage, or high steering speed, the steering can become heavy, making it difficult for the driver to operate and affecting the driving experience and safety.

[0003] Furthermore, in the hydraulic steering system of forklifts, the fully hydraulic steering gear itself has the function of a manual pump. However, since the steering axle of a forklift is generally located at the rear, the steering pressure required for rear-mounted steering is large, which causes the fully hydraulic steering gear to lose its function as a manual pump and become unable to steer in an emergency. Utility Model Content

[0004] The purpose of this application is to provide a steering hydraulic system and a forklift to effectively improve the performance of steering operations.

[0005] To achieve the above objectives, this application provides a steering hydraulic system, which includes a steering gear, a booster cylinder, and a steering cylinder connected in sequence by hydraulics. The hydraulic oil at the outlet of the steering gear can hydraulically drive the booster cylinder, and the booster cylinder can drive the steering cylinder to extend and retract.

[0006] In some embodiments, the booster cylinder includes a small piston cylinder and a large piston cylinder located at both ends, the large piston cylinder being hydraulically connected to the oil outlet of the steering gear, and the small piston cylinder being hydraulically connected to the cylinder chamber of the steering cylinder.

[0007] In some embodiments, the piston assembly of the booster cylinder may include:

[0008] The small piston is located in the cylinder cavity of the small piston cylinder;

[0009] The large piston is located in the cylinder chamber of the large piston cylinder;

[0010] The piston linkage shaft rigidly connects the small piston and the large piston.

[0011] In some embodiments, the piston area ratio between the large piston and the small piston is not less than 2.

[0012] In some embodiments, the piston assembly of the booster cylinder includes a stepped shaft of integral construction.

[0013] In some embodiments, the steering gear is provided with a first oil outlet and a second oil outlet, a first connecting oil passage is provided between the first end of the steering cylinder and the first oil outlet, and a second connecting oil passage is provided between the second end and the second oil outlet.

[0014] The booster cylinder includes a first booster cylinder disposed in the first connecting oil circuit and a second booster cylinder disposed in the second connecting oil circuit.

[0015] In some embodiments, the first and second booster cylinders have the same structure and dimensions.

[0016] In some embodiments, the steering hydraulic system further includes:

[0017] A priority valve is used to distribute hydraulic oil to the steering gear.

[0018] In some embodiments, the steering hydraulic system further includes:

[0019] A hydraulic pump is used to pump hydraulic oil to the inlet of the priority valve.

[0020] This application also provides a forklift, including a rear-mounted steering axle and the aforementioned steering hydraulic system, wherein the steering cylinder acts on the steering axle.

[0021] In the technical solution of this application, a booster cylinder is added between the steering gear and the steering cylinder. This allows the hydraulic oil with low pressure to drive the steering cylinder through the booster cylinder, achieving a boosted drive effect and increasing the pressure output of the hydraulic system. This significantly reduces the effort required for steering, making steering lighter and more agile. While effectively improving steering performance, this also enhances the system's response speed and stability, and optimizes the energy utilization efficiency of the hydraulic system.

[0022] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without any inventive effort. In the drawings:

[0024] Figure 1 A partial hydraulic schematic diagram of a steering hydraulic system according to a specific embodiment of this application;

[0025] Figure 2This is a structural diagram of a booster cylinder in a steering hydraulic system according to a specific embodiment of this application;

[0026] Figure 3 This is a complete hydraulic schematic diagram of a steering hydraulic system according to a specific embodiment of this application.

[0027] Explanation of reference numerals in the attached figures

[0028] Detailed Implementation

[0029] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0030] The forklift and its steering hydraulic system according to this application are described below with reference to the accompanying drawings.

[0031] The steering hydraulic system of a forklift generally consists of a hydraulic pump, a priority valve, a steering gear, and a steering cylinder. The hydraulic pump serves as the power source to supply oil to the system, the priority valve distributes the hydraulic oil, the steering gear is the core control component that plays a role in control and metering, and the steering cylinder is the actuator. The steering gear outlet is connected to the steering cylinder. When factors such as internal leakage or excessive steering wheel speed lead to insufficient hydraulic oil, it is easy to cause heavy steering, which makes it difficult for the driver to operate, affecting the driving experience and safety.

[0032] In view of this, this application discloses a basic steering hydraulic system. For example... Figure 1 As shown, in this embodiment, the novel steering hydraulic system includes a steering gear 5, a booster cylinder, and a steering cylinder 7 connected in sequence by hydraulics. The hydraulic oil from the oil outlet of the steering gear 5 (first oil outlet A or second oil outlet B) can hydraulically drive the booster cylinder, and the booster cylinder drives the steering cylinder 7 to extend and retract.

[0033] By adding one or more booster cylinders between the steering cylinder 7 and the steering gear 5, the pressure output of the hydraulic system can be increased, thereby significantly reducing the steering effort and making steering lighter and more agile. In this way, even the low-pressure hydraulic fluid at the outlet of the steering gear 5 can drive the steering cylinder, improving the system's response speed and stability, and ensuring steering accuracy and reliability under complex operating conditions. Simultaneously, the energy utilization efficiency of the low-pressure hydraulic fluid can be improved, reducing unnecessary energy loss, extending system lifespan, and lowering maintenance costs.

[0034] Specifically, as an example, see Figure 1Two booster cylinders are connected in series between the outlet of the steering gear 5 and the steering cylinder 7, forming an approximately closed circuit. The hydraulic oil at the outlet of the steering gear 5 first drives the booster cylinder, and then drives the steering cylinder 7 through the booster cylinder, thus achieving twice the result with half the effort. It can smoothly drive the steering cylinder 7 even with low pressure output, solving the problem of heavy steering.

[0035] See Figure 1 , Figure 2 A booster cylinder typically consists of a small piston cylinder and a large piston cylinder located at both ends, i.e. Figure 2 The upper and lower ends of the booster cylinder are shown. The large piston cylinder is hydraulically connected to the oil outlet of the steering gear 5, and the small piston cylinder is hydraulically connected to the steering cylinder 7. With this configuration, since the cylinder thrust equals the hydraulic pressure multiplied by the piston's working area, and the small piston cylinder of the booster cylinder is connected to the steering cylinder 7, its pressure is the same as that of the steering cylinder 7. Furthermore, because the piston area of ​​the large piston cylinder of the booster cylinder is several times that of the small piston cylinder, its pressure is a fraction of the steering cylinder's pressure. Since the large piston cylinder is connected to the steering gear outlet, the steering gear's output pressure is also a fraction of the steering cylinder's pressure, thus achieving a power assist effect and reducing the force required to turn the steering wheel. In addition, the booster cylinder improves the system's response speed and stability, ensuring steering accuracy and reliability under complex operating conditions.

[0036] Figure 2 The diagram shows a typical booster cylinder structure. The booster cylinder's piston assembly includes a small piston located in the chamber of a small piston cylinder and a large piston located in the chamber of a large piston cylinder. The small piston in the small piston cylinder and the large piston in the large piston cylinder are rigidly connected by a piston linkage shaft 6. Thus, the hydraulic oil from the outlet of the steering gear 5 first enters the chamber of the large piston cylinder. The hydraulic oil in the large piston cylinder pushes the large piston to move, which in turn drives the small piston to move synchronously via the piston linkage shaft 6.

[0037] Since the large and small pistons are rigidly connected by a linkage shaft, meaning the piston assembly is a single moving part, given a fixed steering oil pressure required for the cylinder chamber of steering cylinder 7, the hydraulic oil pressure required for the large piston cylinder is relatively small; that is, a relatively small outlet oil pressure from steering gear 5 is sufficient. As mentioned earlier, the ratio between the steering oil pressure required for steering cylinder 7 and the outlet oil pressure from steering gear 5 should be the ratio of the piston areas of the large and small pistons. Therefore, the larger the piston area ratio between the large and small pistons, the more pronounced the booster effect. As an example, Figure 1 , Figure 2 In the booster cylinder shown, the piston area ratio between the large and small pistons should be no less than 2. Of course, this application is not limited to this; the piston area ratio can be set to be larger or smaller, and can be determined and selected according to specific working conditions.

[0038] The piston assembly of the booster cylinder in this application is not limited to... Figure 2 The structure of the large and small pistons and piston linkage shaft 6 shown can be optionally integrated, with the piston assembly being a stepped shaft, the small end of the stepped shaft serving as the small piston, and the large end serving as the large piston, which facilitates integral machining.

[0039] It should be noted that in the steering hydraulic system of this embodiment, depending on the working conditions, only one booster cylinder may be installed, that is, only steering operation on one side is assisted. For example... Figure 1 As shown, a typical system includes two booster cylinders: a first booster cylinder 61 and a second booster cylinder 62. Due to the balance and symmetry required for left and right steering, both booster cylinders 61 and 62 can be of the same specifications, meaning they have identical structure and dimensions. Of course, depending on the required level of assistance, the first and second booster cylinders can be of different sizes; however, in such cases, the hydraulic system design must consider overflow and replenishment requirements.

[0040] See Figure 3 The steering hydraulic system of this embodiment includes not only Figure 1 The steering gear 5, steering cylinder 7, and booster cylinder shown may further include:

[0041] Priority valve 4 is used to distribute hydraulic oil to the steering gear 5.

[0042] The priority valve is used to distribute and prioritize hydraulic oil between the steering system and other working attachments. Priority valve 4 can deliver some or all of the hydraulic oil to the steering gear 5 for steering operations.

[0043] Furthermore, the steering hydraulic system may also include a hydraulic pump 2 for pumping hydraulic oil to the inlet of the priority valve 4. This hydraulic pump 2 may be the undercarriage master pump of an industrial vehicle, directly pumping hydraulic oil to the priority valve 4. Of course, the steering hydraulic system may also be connected to the main working oil circuit of other hydraulic systems through the priority valve 4, and this application is not limited to this.

[0044] As can be seen, hydraulic pump 2 supplies oil to the system, priority valve 4 is used to distribute the pumped hydraulic oil, steering gear 5 is the core control component, playing the role of control and metering, and steering cylinder 7 is the steering actuator, with the outlet of steering gear 5 connected to steering cylinder 7. Figure 3 The priority valve 4 and the steering gear 5 can both use commonly available valve components, therefore, the structure and working principle of each valve component will not be described in detail here. Figure 1 , Figure 3 It is evident that the steering gear 5 used in this system has a manual pump function.

[0045] In summary, Figure 3In this embodiment, a basic power steering system is disclosed, comprising a filter 1, a hydraulic pump 2, a pump oil check valve 3, a priority valve 4, a steering gear 5, a booster cylinder, and a steering cylinder 7. The hydraulic oil pumped by the hydraulic pump 2 first passes through the priority valve 4 for flow distribution, then enters the P port of the steering gear 5. After being metered by the steering gear 5, the oil exits from the steering gear 5 and connects to the large piston chamber of the booster cylinder. The large piston and small piston of the booster cylinder are rigidly connected, and their areas are proportional. The small piston cylinder is connected to the steering cylinder 7.

[0046] In addition, this application also protects a forklift including a rear-mounted steering axle (not shown) and the aforementioned steering hydraulic system, wherein the steering cylinder 7 acts on the steering axle.

[0047] Since forklift steering axles are generally rear-mounted, the steering pressure requirement is high. When the system is without power, such as when pumping hydraulic oil to other work attachments via a priority valve, the fully hydraulic steering gear loses its function as a manual pump, making steering impossible in emergencies. In this situation, the steering hydraulic system of this application, even with low hydraulic oil pressure through the steering gear 5, can still achieve a large pressure output, proportionally reducing the output pressure of the steering gear. The areas of the large and small piston cylinders in the booster cylinder are proportional; according to F=PA, the pressure of the large piston cylinder is less than the pressure of the small piston cylinder. The small piston cylinder is connected to the steering cylinder 7, and the large piston cylinder is connected to the outlet of the steering gear 5. Therefore, it reduces the effort required to turn the steering wheel and extends the service life of the steering gear 5.

[0048] The steering hydraulic system described in this application also improves system accuracy. Because the diameters of the large and small piston cylinders in the booster cylinder are proportional, the flow input to the large piston cylinder is proportionally amplified, thus improving steering precision. Furthermore, it enables the steering gear to function as a manual pump, allowing for steering in emergencies and improving safety. The booster cylinder reduces the steering gear outlet pressure, resulting in a smaller force acting on the steering gear rotor, thereby enabling manual steering without power. Based on this, it solves the problem of large-tonnage forklifts being unable to directly use the steering gear due to excessively high pressure.

[0049] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0051] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A steering hydraulic system, characterized in that, The steering hydraulic system includes a steering gear (5), a booster cylinder and a steering cylinder (7) connected in sequence by hydraulics. The hydraulic oil at the outlet of the steering gear (5) can hydraulically drive the booster cylinder and drive the steering cylinder (7) to extend and retract through the booster cylinder.

2. The steering hydraulic system according to claim 1, characterized in that, The booster cylinder includes a small piston cylinder and a large piston cylinder located at both ends. The large piston cylinder is hydraulically connected to the oil outlet of the steering gear (5), and the small piston cylinder is hydraulically connected to the cylinder chamber of the steering cylinder (7).

3. The steering hydraulic system according to claim 2, characterized in that, The piston assembly of the booster cylinder includes: The small piston is located in the cylinder cavity of the small piston cylinder; The large piston is located in the cylinder chamber of the large piston cylinder; The piston linkage shaft (6) rigidly connects the small piston and the large piston.

4. The steering hydraulic system according to claim 3, characterized in that, The piston area ratio between the large piston and the small piston is not less than 2.

5. The steering hydraulic system according to claim 2, characterized in that, The piston assembly of the booster cylinder includes a stepped shaft with an integral structure.

6. The steering hydraulic system according to any one of claims 2 to 5, characterized in that, The steering gear (5) is provided with a first oil outlet (A) and a second oil outlet (B). The first end of the steering cylinder (7) is provided with a first connecting oil passage between the first oil outlet (A) and the second end is provided with a second connecting oil passage between the second end and the second oil outlet (B). The booster cylinder includes a first booster cylinder (61) disposed in the first connecting oil circuit and a second booster cylinder (62) disposed in the second connecting oil circuit.

7. The steering hydraulic system according to claim 6, characterized in that, The first booster cylinder (61) and the second booster cylinder (62) have the same structure and size.

8. The steering hydraulic system according to claim 1, characterized in that, The steering hydraulic system also includes: Priority valve (4) is used to distribute hydraulic oil to the steering gear (5).

9. The steering hydraulic system according to claim 8, characterized in that, The steering hydraulic system also includes: A hydraulic pump (2) is used to pump hydraulic oil to the inlet of the priority valve (4).

10. A forklift, characterized in that, The forklift includes a steering hydraulic system according to any one of claims 1 to 9.

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