Application Structure of Solid State Relays in Freshwater Preheating Units of Marine Diesel Engines

Abstract

This invention provides a solid-state relay (SSR) application structure in a marine diesel engine freshwater preheating unit. The SSR, housed in a control box, controls the on / off state of an electric heater. A radiator is mounted on the SSR, and a temperature control device is connected in series with the SSR's control circuit to detect its temperature. A cooling fan in the radiator is connected to a radiator operation monitoring circuit, and the heating unit's operating signal switch contacts are also connected in series with this circuit. When the operating signal switch contacts are closed, the radiator operation monitoring circuit monitors whether the cooling fan is functioning properly. This invention overcomes the shortcomings of traditional contactor-based heating units, such as high vibration, high power consumption, contact wear, and susceptibility to damage. It avoids the potential risks associated with SSRs, improving their reliability and safety, and achieving long-term reliable operation of the freshwater preheating unit.

Description

Technical Field

[0001] This utility model belongs to the field of diesel engine technology, specifically relating to the application structure of a solid-state relay in the freshwater preheating unit of a marine diesel engine. Background Technology

[0002] Marine diesel engines, as the power source for ships, require reliable and stable operation over a long period for navigation. During cold starts, internal components of the diesel engine are subjected to significant impact and wear, affecting its service life. Therefore, a warm-up process is usually required before starting a diesel engine. The freshwater preheating unit, an accessory to the diesel engine's external freshwater circulation system, is installed in the engine room. By preheating the circulating freshwater, it raises the internal temperature of the diesel engine, thus serving a warm-up function.

[0003] The freshwater preheating unit consists of two heating cylinders, an electric heater for heating the water in the heating cylinders, a control box, a circulating water pump, a safety valve, a shut-off valve, a flow switch, a pressure gauge, a temperature sensor, a temperature switch, inlet and outlet flanges, and mounting brackets. Its control principle is based on the temperature of the circulating freshwater detected by the temperature sensor. By controlling the engagement of the low-voltage AC contactor in the control box, the electric heater is connected or disconnected, so that the temperature of the circulating freshwater is controlled within a certain range.

[0004] Low-voltage AC contactors, as electrical control components, operate on the principle of electromagnets. When the voltage in the control circuit reaches a certain value, the electromagnet generates sufficient attraction to overcome the spring's reaction force, attracting the moving iron core and causing the main and auxiliary contacts to close, thus connecting the main circuit. When the control circuit loses power, the electromagnetic attraction disappears, the spring's reaction force resets the moving iron core, and the main and auxiliary contacts open, disconnecting the main circuit. However, these low-voltage AC contactors have the following drawbacks: 1) The contactor uses a mechanical contact principle, controlling the circuit's on / off state through the closing or opening of contacts. The manufacturing process is complex, requiring high-quality materials and precise processing techniques, thus resulting in relatively high costs; 2) Frequent engagement of high-current contactors... Significant vibration can easily cause loosening of wiring screws, leading to arcing and damage at the wiring points; it can also cause arcing when disconnecting the load, resulting in contact wear; 3) High contactor engagement power consumption: Since marine equipment often operates in humid environments, for safety reasons, such as the control circuit that the operator contacts using a safe AC24V voltage, the instantaneous current of the contactor engagement under AC24V / 50Hz conditions is about 7A. When the preheating unit initially starts working, due to the low temperature of the heating medium, two sets of heaters work simultaneously to improve efficiency, so the instantaneous contactor starting current is about 14A. To ensure reliable contactor engagement, the control circuit often needs to select a transformer with a larger capacity; therefore, to solve the above technical problems, it is necessary to improve the freshwater preheating unit. Utility Model Content

[0005] The technical problem solved by this utility model is to provide an application structure of solid-state relays in the freshwater preheating unit of marine diesel engines. By using solid-state relays in the freshwater preheating unit of marine diesel engines, the defects of traditional heating units using contactors, such as large vibration, high power consumption, contact loss, and easy damage, are overcome. Simultaneously, a temperature control device is connected in series in the control circuit of the solid-state relay, and a radiator operation monitoring circuit is designed to monitor whether the radiator of the solid-state relay is working properly. This avoids the potential risks associated with solid-state relays, improves their reliability and safety, and achieves the goal of long-term reliable operation of the freshwater preheating unit. It has many advantages such as frequent switching, low power consumption, high reliability, and long lifespan, providing a guarantee for the long-term stable operation of the diesel engine freshwater preheating unit.

[0006] The technical solution adopted in this utility model is as follows: The application structure of a solid-state relay in a freshwater preheating unit of a marine diesel engine includes a solid-state relay housed in a control box for controlling the on / off state of an electric heater. A radiator is mounted on the solid-state relay, and a temperature control device is installed on the radiator to detect its temperature. The temperature control device is connected in series in the control circuit of the solid-state relay. When the radiator temperature exceeds the set temperature of the temperature control device, the temperature control device disconnects the control circuit of the solid-state relay. A cooling fan in the radiator is connected to a radiator operation monitoring circuit, and the working signal switch contacts of the heating unit are connected in series in the radiator operation monitoring circuit. When the working signal switch contacts are closed, the radiator operation monitoring circuit monitors whether the cooling fan is working properly for heat dissipation.

[0007] The temperature control device includes a temperature switch, which is fixedly attached to the heat sink, and thermal grease is provided between the fixedly attached temperature switch and the heat sink.

[0008] Furthermore, the radiator operation monitoring circuit includes a DC power supply for powering the circuit, a current detection amplifier, a sampling resistor, a current limiting resistor, a relay drive circuit, an indicator light for indicating the working status of the heating unit corresponding to the cooling fan, and a normally open contact controlled by the relay drive circuit. The sampling resistor is connected in series with the cooling fan in the power supply circuit, and the differential input terminal of the current detection amplifier is connected to the sampling resistor to collect the voltage signal across the sampling resistor. The output terminal of the current detection amplifier is connected to the relay drive circuit through the current limiting resistor to output the amplified signal from the current detection amplifier to the relay drive circuit. The relay drive circuit is connected in series with the indicator light, and the working signal switch contact, the indicator light, and the normally open contact controlled by the relay drive circuit form an indicator branch connected in series in the power supply circuit.

[0009] Furthermore, the relay drive circuit includes an alarm relay for triggering an alarm signal when the cooling fan is in an abnormal state, and a Zener diode connected to the coil side for stabilizing the voltage of the relay drive circuit.

[0010] Furthermore, the ground pin of the current sensing amplifier is connected to the circuit common ground.

[0011] Furthermore, a temperature controller contact is connected in series in the control circuit of the solid-state relay, and the closing or opening of the temperature controller contact is controlled by a temperature controller used to detect the temperature of the circulating fresh water.

[0012] Advantages of this utility model compared to the prior art: 1. This technical solution has a temperature switch on the heat sink for detecting its temperature, and the temperature switch is connected in series in the control circuit of the solid-state relay. When the heat sink temperature reaches the temperature switch action value, the solid-state relay is disconnected, thereby protecting the solid-state relay. It achieves dual monitoring of the solid-state relay under the joint action of the heat sink operation monitoring circuit, ensuring its stable and reliable operation. 2. This technical solution designs a radiator operation monitoring circuit to monitor whether the radiator of the solid-state relay is working properly, realizes the status monitoring of the radiator, effectively avoids the potential risks of solid-state relays, improves the reliability and safety of solid-state relays, and achieves the goal of long-term reliable operation of the freshwater preheating unit. 3. This technical solution has a simple structure and novel design, overcoming the shortcomings of traditional heating units that use contactors, such as large vibration, high power consumption, contact loss, and easy damage. The solid-state relay operates stably and reliably, and has many advantages such as frequent switching, low power consumption, high reliability, and long service life, thus ensuring the long-term stable operation of the diesel engine freshwater preheating unit. Attached Figure Description

[0013] Fig. 1 This is a schematic diagram of the connection circuit in the solid-state relay of this utility model; Fig. 2 This is a schematic diagram of the radiator operation monitoring circuit of this utility model. Detailed Implementation

[0014] The following will be based on the embodiments of this utility model. Figs. 1-2 The technical solutions in the embodiments of this utility model are clearly and completely described herein. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0015] It should be noted that, unless otherwise stated herein, the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0016] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0017] The application structure of solid-state relays in the freshwater preheating unit of marine diesel engines, such as... Figs. 1-2 As shown, the system includes a solid-state relay 2 housed in a control box for controlling the on / off state of the electric heater 1. The solid-state relay 2 is equipped with a heat sink, which has a temperature control device for detecting its temperature. This temperature control device is connected in series in the control circuit of the solid-state relay 2. When the heat sink temperature exceeds the set temperature of the temperature control device, the temperature control device disconnects the control circuit of the solid-state relay 2. A cooling fan 4 in the heat sink is connected to a heat sink operation monitoring circuit 5, and a working signal switch contact 6 of the heating unit is connected in series in the heat sink operation monitoring circuit 5. When the working signal switch contact 6 is closed, the heat sink operation monitoring circuit 5 monitors whether the cooling fan 4 is working properly for heat dissipation. In the above structure, a solid-state relay is used. Device 2 replaces the traditional low-voltage AC contactor, overcoming the shortcomings of contactors such as large vibration, high power consumption, easy contact wear and damage. It has the advantages of frequent switching, low power consumption, high reliability, and long service life. By setting a temperature control device on the heat sink and connecting it in series with the control circuit of solid-state relay 2, temperature protection of solid-state relay 2 is realized. When the heat sink temperature is too high, the control circuit can be disconnected in time to avoid damage to solid-state relay due to overheating. The heat sink operation monitoring circuit 5 is designed to monitor the working status of cooling fan 4 in real time, ensuring the normal operation of the heat dissipation system, effectively avoiding the potential risks caused by poor heat dissipation of solid-state relay 2, improving the reliability and safety of solid-state relay 2, and ensuring the long-term reliable operation of the freshwater preheating unit.

[0018] The temperature control device includes a temperature switch 7, which is fixedly attached to the heat sink, and thermal grease is provided between the fixedly attached temperature switch 7 and the heat sink. By providing a temperature switch 7 on the heat sink to detect its temperature, and connecting the temperature switch 7 in series in the control circuit of the solid-state relay 2, the solid-state relay 2 is disconnected when the heat sink temperature reaches the operating value of the temperature switch 7, thereby protecting the solid-state relay 2. This achieves dual monitoring of the solid-state relay under the joint action of the heat sink operation monitoring circuit, ensuring its stable and reliable operation. The main function of temperature switch 7 is to connect or disconnect the circuit according to the temperature change, thereby controlling the operating status of electrical appliances or systems. When temperature switch 7 detects that the radiator temperature exceeds its set value, temperature switch 7 will activate, thereby disconnecting the control circuit of solid-state relay 2 and realizing overheat protection for solid-state relay 2.

[0019] Since temperature significantly affects the performance of the solid-state relay 2, the proper functioning of its heatsink is crucial. Detecting the operating current of the cooling fan 4 within the heatsink using a current monitoring amplifier is an effective method for determining whether the heatsink is functioning correctly. Therefore, a heatsink operation monitoring circuit 5 was designed, such as... Fig. 2As shown, the specific structure of the radiator operation monitoring circuit 5 is as follows: The radiator operation monitoring circuit 5 includes a DC power supply for powering the circuit, a current detection amplifier 5-1, a sampling resistor 5-2, a current limiting resistor 5-3, a relay drive circuit, an indicator light 5-7 for indicating the working status of the heating unit corresponding to the cooling fan 4, and a normally open contact 5-6 controlled by the relay drive circuit. The current detection amplifier 5-1 is an INA282AID current detection amplifier. The sampling resistor 5-2 is connected in series with the cooling fan 4 in the power supply circuit, and the differential input terminal of the current detection amplifier 5-1 is connected to the sampling resistor 5-2 to collect the voltage signal across the sampling resistor 5-2. The output terminal of the current detection amplifier 5-1 is connected to the relay drive circuit through the current limiting resistor 5-3 to output the amplified signal from the current detection amplifier 5-1 to the relay drive circuit. The relay drive circuit is connected in series with the indicator light 5-7, and the working signal switch contact 6 is connected to the indicator light 5-7. The indicator branch formed by lamp 5-7 and normally open contact 5-6 controlled by the relay drive circuit is connected in series in the power supply circuit. The grounding pin of the current detection amplifier 5-1 is connected to the circuit common ground. Specifically, the relay drive circuit includes an alarm relay 5-4 for triggering an alarm signal when the cooling fan 4 is in an abnormal state, and a Zener diode 5-5 connected to the coil side for stabilizing the voltage of the relay drive circuit. In the above structure, the radiator operation monitoring circuit 5 designed to monitor whether the radiator of the solid-state relay 2 is working properly realizes the status monitoring of the radiator, effectively avoids the potential risks of the solid-state relay, improves the reliability and safety of the solid-state relay, and achieves the purpose of long-term reliable operation of the freshwater preheating unit. Among them, the control circuit of the solid-state relay 2 also has a temperature controller contact 3 connected in series, and the closing or opening of the temperature controller contact 3 is controlled by a temperature controller for detecting the temperature of the circulating freshwater. The connection method of the temperature controller is an existing structure and is not closely related to this solution, so it will not be described in detail here.

[0020] When the working signal switch contact 6 is closed, if the cooling fan 4 is working normally, the relay drive circuit will activate the normally open contact 5-6, and the indicator light 5-7 will light up, indicating that the heating unit is working normally. If the cooling fan 4 is malfunctioning (such as stopping), the voltage signal across the sampling resistor 5-2 will be abnormal, the output signal of the current detection amplifier 5-1 will change, the relay drive circuit will not operate normally, and the state of the indicator light 5-7 will change accordingly, thus realizing the monitoring of the working status of the cooling fan 4.

[0021] The radiator operation monitoring circuit 5 monitors the working status of the cooling fan 4 and is a self-test circuit for equipment status. When a malfunction of the cooling fan 4 is detected, resulting in poor heat dissipation, an alarm is triggered via indicator lights 5-7, prompting maintenance personnel to intervene. The workload of this heating equipment varies greatly depending on the site conditions. (When the heating medium temperature is high, the solid-state relay 2 operates for a short time, which is considered light load operation; when the heating medium temperature is low, the heating operation time is long, which is considered heavy load operation.) During light load operation, the equipment relies on its own heat sink to achieve thermal equilibrium. During heavy load operation, the heat sink cannot achieve thermal equilibrium, resulting in excessive temperature rise. In this case, the thermal protection opener contact 3 is activated, cutting off the heating circuit to protect the solid-state relay 2.

[0022] The application of solid-state relay 2 in the freshwater preheating unit of marine diesel engines overcomes the defects of contactors such as large vibration, poor contact, contact loss, high power consumption, easy arcing, and easy damage. It has many advantages such as frequent switching, low power consumption, high reliability, and long service life. By adding an appropriate temperature switch 7 and designing a radiator operation monitoring circuit 7, the potential for the performance of solid-state relay 2 to be affected by temperature is avoided, and the reliability and safety of solid-state relay 2 are improved. This provides a guarantee for the long-term stable operation of the freshwater preheating unit of the diesel engine.

[0023] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0024] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. The structure of a solid-state relay in a freshwater preheating unit of a marine diesel engine, characterized by: The system includes a solid-state relay (2) located in the control box and used to control the on or off of the electric heater (1). The solid-state relay (2) is equipped with a heat sink. The heat sink is equipped with a temperature control device for detecting its temperature. The temperature control device is connected in series in the control circuit of the solid-state relay (2). When the temperature of the heat sink exceeds the set temperature of the temperature control device, the temperature control device disconnects the control circuit of the solid-state relay (2). The cooling fan (4) in the heat sink is connected in the heat sink operation monitoring circuit (5). The working signal switch contact (6) of the heating unit is connected in series in the heat sink operation monitoring circuit (5). When the working signal switch contact (6) is closed, the heat sink operation monitoring circuit (5) monitors whether the cooling fan (4) is working properly to dissipate heat.

2. The application structure of the solid-state relay in the freshwater preheating unit of a marine diesel engine according to claim 1, characterized in that: The temperature control device includes a temperature switch (7), which is fixedly attached to the heat sink, and thermal grease is provided between the fixedly attached temperature switch (7) and the heat sink.

3. The application structure of the solid-state relay in the freshwater preheating unit of a marine diesel engine according to claim 1, characterized in that: The radiator operation monitoring circuit (5) includes a DC power supply for powering the circuit, a current detection amplifier (5-1), a sampling resistor (5-2), a current limiting resistor (5-3), a relay drive circuit, an indicator light (5-7) for indicating the working status of the heating unit corresponding to the cooling fan (4), and a normally open contact (5-6) controlled by the relay drive circuit. The sampling resistor (5-2) is connected in series with the cooling fan (4) in the power supply circuit, and the differential input terminal of the current detection amplifier (5-1) is connected to the sampling resistor (5-2) to collect the voltage signal across the sampling resistor (5-2). The output terminal of the current detection amplifier (5-1) is connected to the relay drive circuit through the current limiting resistor (5-3) to output the signal amplified by the current detection amplifier (5-1) to the relay drive circuit. The relay drive circuit is connected in series with the indicator light (5-7), and the working signal switch contact (6) is connected in series with the indicator branch formed by the indicator light (5-7) and the normally open contact (5-6) controlled by the relay drive circuit in the power supply circuit.

4. The application structure of the solid-state relay in the freshwater preheating unit of a marine diesel engine according to claim 3, characterized in that: The relay drive circuit includes an alarm relay (5-4) for triggering an alarm signal when the cooling fan (4) is in an abnormal state, and a Zener diode (5-5) connected to the coil side for stabilizing the voltage of the relay drive circuit.

5. The application structure of the solid-state relay in the freshwater preheating unit of a marine diesel engine according to claim 4, characterized in that: The ground pin of the current sensing amplifier (5-1) is connected to the circuit common ground.

6. The structure of the solid-state relay according to any one of claims 1-5 in the freshwater preheating unit of a marine diesel engine, characterized in that: The solid-state relay (2) also has a temperature controller contact (3) connected in series in its control circuit, and the closing or opening of the temperature controller contact (3) is controlled by a temperature controller used to detect the temperature of the circulating fresh water.

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