A wireless real-time measurement system and installation method for the temperature of an internal combustion engine piston

Abstract

The application discloses a thermocouple suitable for temperature measurement of an internal combustion engine piston, and the thermocouple comprises a thermocouple wire and an armored sleeve, the armored sleeve comprises a large-end and a small-end, and the large-end is installed on the high-temperature gas side. The middle surface between the large-end and the small-end bears the pressure of the high-temperature gas in the piston, and simultaneously plays a sealing role, so that the high-temperature gas is prevented from leaking out from the gap between the piston and the thermocouple. The application further discloses a mounting method of the thermocouple suitable for temperature measurement of the internal combustion engine piston. For a monolithic piston, different mounting modes are selected according to the temperature measurement point position of the piston. For a combined piston, a protective sleeve is arranged between the piston crown and the piston skirt, and the thermocouple extension line passes through the protective sleeve, so that the thermocouple can work reliably and stably in the harsh environment of high temperature and high pressure.

Description

Technical Field

[0001] This invention patent relates to the field of engine and testing technology, and more specifically, to a method for measuring the piston temperature of an internal combustion engine. Background Technology

[0002] An internal combustion engine is a power device that converts heat energy into mechanical energy. It is compact, has high output power, and is stable and reliable, making it the most thermally efficient mobile power unit. It is widely used in vehicles, ships, and other fields. In an internal combustion engine, the piston, as the "heart" component, plays a crucial role in heat-work conversion, flow field organization, and combustion organization. However, the piston operates under extremely harsh conditions, directly contacting high-temperature combustion gases (2500K) and experiencing the coupled effects of alternating thermal and mechanical stresses. This makes it prone to mechanical failures such as burning, cracking, and cylinder scoring. Measuring piston temperature is a crucial basis for evaluating its thermal load and reliability.

[0003] Temperature measurement can be mainly divided into two categories: contact temperature measurement and non-contact temperature measurement. Although non-contact temperature measurement has a fast response speed and can measure the entire temperature field of the piston top surface, it is affected by the radiation of flames and carbon soot, resulting in large measurement errors; moreover, it is limited by the size of the equipment and cannot be used normally in confined spaces. For measuring the temperature of the piston top surface, contact temperature measurement is better, with thermocouples being the optimal choice.

[0004] For the problem of measuring piston temperature in internal combustion engines, how to design the structure of thermocouples, how to install thermocouples on pistons with high-speed reciprocating motion and narrow installation space, and how to ensure their reliable and stable operation in harsh environments with high temperature and high pressure have become challenges. Summary of the Invention

[0005] In response to the deficiencies or improvement needs of existing technologies, this invention provides a thermocouple and its arrangement scheme suitable for piston temperature measurement. Its purpose is to ensure the reliability and stability of the measurement and to provide basic data for the study of combustion and heat transfer problems in engine cylinders.

[0006] The internal combustion engine piston temperature wireless real-time measurement system includes a wireless signal transmitter located below the piston pin seat inside the cylinder, a data receiving antenna located below the cylinder liner, and a wireless signal receiver located outside the cylinder. The temperature sensor detects the temperature of the piston surface under test, converts the temperature signal into a voltage signal to be measured, and transmits the measured voltage signal to the in-cylinder wireless signal transmitter. The data transmitting antenna then transmits the measured temperature, cold end temperature, and other signals via 433MHz wireless communication to the data receiving antenna. The data receiving antenna transmits the data to the external wireless signal receiver and then via wired transmission to a host computer, where the temperature data is finally displayed in real time.

[0007] According to one aspect of the present invention, a thermocouple suitable for measuring the piston temperature of an internal combustion engine is provided, comprising a thermocouple wire and an armored sleeve, the armored sleeve comprising a large end and a small end, the large end being installed on the high-temperature combustion gas side. The pressure of the high-temperature combustion gas inside the piston is borne by the intermediate surface of the large end and the small end, while simultaneously serving a sealing function to prevent the high-temperature combustion gas from escaping from the gap between the piston and the thermocouple.

[0008] Furthermore, the armored sleeve is stepped or conical. When a stepped shape is used, the pressure of the high-temperature combustion gas inside the piston is supported by the intermediate shoulder between the large and small ends, thus achieving a seal.

[0009] Furthermore, for combined pistons, the circumferential surface of the large end has either a threaded or smooth surface, while for integral pistons, the circumferential surface of the large end has a smooth surface. Thermocouples with a threaded large end are fixedly connected to the piston via threads, resulting in better sealing and preventing the thermocouple from easily dislodging during piston movement. Thermocouples with a smooth large end are installed via a press-fit method, eliminating the need for rotation and tightening during installation, thus avoiding damage to the thermocouple extension wire due to tangling, and are suitable for integral pistons.

[0010] Furthermore, the armor sleeve is made of the same material as the piston to ensure that the thermal conductivity of the armor sleeve and the piston under test is consistent, thereby reducing measurement errors.

[0011] Furthermore, the thermocouple is a shell-type thermocouple. The wall thickness of the armored sleeve end face is determined by the material of the thermocouple armored sleeve. The minimum wall thickness for steel armored sleeves is 0.5 mm, and the minimum wall thickness for aluminum armored sleeves is 1 mm. This wall thickness can prevent the protective sleeve from being crushed by high-pressure combustion gases on the piston top surface, and also prevent a large deviation between the measuring point and the point to be measured on the piston top surface, which would reduce measurement accuracy.

[0012] Furthermore, the shape of the top surface of the armored sleeve should not damage the original surface structure of the piston test point, so as to avoid changes in the piston top shape structure caused by the installation of the armored thermocouple into the piston, which would lead to changes in the combustion performance of the internal combustion engine.

[0013] Furthermore, since the thermocouple is repeatedly eroded in the oil passage, in order to ensure the reliability of the thermocouple structure, the tensile strength between the thermocouple temperature measuring contact and the armor sleeve is greater than 20N during processing to prevent the thermocouple temperature measuring contact from falling off at the connection with the armor sleeve.

[0014] Furthermore, during thermocouple installation, high-temperature resistant ceramic adhesive needs to be applied to the surface of the armor sleeve before inserting the thermocouple. This serves two purposes: firstly, to prevent the thermocouple from flying out due to inertia when the piston moves at high speed; and secondly, the ceramic adhesive ensures a certain sealing effect, preventing high-temperature gas from escaping through the gap between the armor sleeve and the piston mounting hole.

[0015] To achieve the above objectives, according to another aspect of the present invention, a thermocouple mounting method suitable for piston temperature measurement is also provided, characterized in that a thermocouple mounting hole is machined on the piston surface, the thermocouple is mounted on the piston surface, and the thermocouple extension wire enters the piston interior from the piston top and is connected to an in-cylinder wireless signal transmitter.

[0016] For integral pistons, when the temperature sensor measuring point can avoid the oil passage hole, a long mounting hole is machined to mate with the thermocouple armor sleeve structure, allowing the thermocouple to directly reach the piston interior. This prevents the thermocouple from extending into the oil passage and affecting the lubricating oil flow, while also preventing electrical faults such as thermocouple detachment caused by the vibration environment of the lubricating oil within the oil passage. When the temperature sensor cannot avoid the thermocouple measuring point in the oil passage hole, such as at the piston ring land measuring point, a short mounting hole is machined to allow the thermocouple extension wire to enter the oil passage. A plug hole is machined near the thermocouple measuring point, and the thermocouple extension wire runs within the oil passage hole and exits from the plug hole.

[0017] For a combined piston, the thermocouple extension wire enters the inner oscillation chamber from the outer oscillation chamber through the oil passage. A protective sleeve is installed between the piston top and the piston skirt. The thermocouple extension wire enters the sleeve from the piston top and then exits from the piston skirt.

[0018] Specifically, the thermocouple extension wire is arranged against the wall of the oscillation chamber and fixed with high-temperature resistant epoxy resin to avoid damage to the thermocouple caused by piston oscillation and lubricating oil erosion.

[0019] Furthermore, in order to smoothly lead the thermocouple extension wire from the piston top to the piston skirt and avoid damage to the thermocouple due to piston oscillation and lubricating oil scouring, a protective sleeve is installed between the piston top and the piston skirt, through which the thermocouple extension wire passes.

[0020] Specifically, the protective sleeve consists of a top thread, an intermediate sleeve, a bottom thread, and a retaining ring.

[0021] Furthermore, a threaded hole is machined at the teardrop-shaped protrusion on the piston top, and the top of the protective sleeve is threadedly connected to the piston top. A tripod fixing bracket is installed on the piston skirt, with an installation hole machined in the middle of the tripod fixing bracket. The bottom of the protective sleeve is threadedly connected to the middle of the tripod fixing bracket, and the three legs of the tripod fixing bracket are connected to the piston skirt. Through the tripod fixing bracket, the lateral impact received by the protective sleeve will be transferred to the connection point at the piston skirt, thereby improving the impact resistance of the protective sleeve.

[0022] Alternatively, the protective sleeve can be designed with an external thread structure, through which the thermocouple extension wire passes. A threaded hole is machined on the outside of the oscillation chamber inside the piston skirt to mate with the external thread of the protective sleeve, thereby securing the protective sleeve. This method is simple to manufacture, but it requires a high degree of coaxiality between the thermocouple extension wire and the sleeve.

[0023] In summary, compared with the prior art, the thermocouple and installation method for piston temperature measurement provided by the present invention for transient temperature measurement have the following advantages:

[0024] (1) A thermocouple suitable for piston temperature measurement is proposed, including a thermocouple wire and an armored sleeve. The armored sleeve includes a large end and a small end, with the large end installed on the high-temperature gas side. The pressure of the high-temperature gas inside the piston is borne by the middle surface of the large end and the small end, which also serves as a seal to prevent the high-temperature gas from escaping from the gap between the piston and the thermocouple.

[0025] (2) An installation method for a thermocouple suitable for measuring the temperature of an internal combustion engine piston. Different installation methods and matching tooling are proposed according to different piston types to ensure that the thermocouple works stably and reliably in harsh environments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the working principle of an internal combustion engine piston temperature measurement system.

[0027] Figure 2 Schematic diagram of a stepped armored thermocouple structure;

[0028] Figure 3 A schematic diagram showing the installation method of an integral piston thermocouple that avoids the oil passage hole;

[0029] Figure 4 This is a schematic diagram illustrating the installation method of an integral piston thermocouple that cannot avoid the oil passage hole;

[0030] Figure 5 A schematic diagram showing the arrangement of the extension wires of a combined piston thermocouple.

[0031] Figure 6 This is a schematic diagram of the protective sleeve structure according to Embodiment 1 of the present invention;

[0032] Figure 7 This is a schematic diagram of the three-legged fixed bracket structure according to Embodiment 1 of the present invention;

[0033] Figure 8 This is a schematic diagram of the installation of the combined piston thermocouple according to Embodiment 1 of the present invention;

[0034] Figure 9 This is a schematic diagram of the protective sleeve structure according to Embodiment 2 of the present invention;

[0035] Figure 10 This is a schematic diagram of the installation of the combined piston thermocouple in Embodiment 2 of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. In this invention, the terms "first," "second," etc. (if present), in this invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0037] The working principle of the wireless real-time measurement system for internal combustion engine piston temperature is as follows: Figure 1 As shown, the wireless real-time piston temperature measurement system for internal combustion engines includes a wireless signal transmitter located below the piston pin seat inside the cylinder, a data receiving antenna located below the cylinder liner, and a wireless signal receiver located outside the cylinder. The temperature sensor detects the temperature of the piston surface under test, converts the temperature signal into a voltage signal to be measured, and transmits the measured voltage signal to the wireless signal transmitter inside the cylinder. The data transmitting antenna then transmits the measured temperature, cold end temperature, and other signals via 433MHz wireless communication to the data receiving antenna. The data receiving antenna transmits the data to the wireless signal receiver outside the cylinder and then via wired transmission to a host computer, where the temperature data is finally displayed in real time.

[0038] A thermocouple suitable for measuring piston temperature in internal combustion engines includes a thermocouple wire and an armored sleeve. The armored sleeve has a large end and a small end, with the large end installed on the high-temperature combustion gas side. The pressure of the high-temperature combustion gas inside the piston is borne by the middle surface of the large and small ends, which also serves as a seal to prevent the high-temperature combustion gas from escaping from the gap between the piston and the thermocouple. The armored sleeve is stepped or conical. The thermocouple used for piston temperature measurement is a grounding type thermocouple. The wall thickness of the armored sleeve end face is determined by the material of the thermocouple armored sleeve; the minimum wall thickness is 0.5 mm for steel armored sleeves and 1 mm for aluminum armored sleeves. This wall thickness prevents the protective sleeve from being crushed by the high-pressure combustion gas on the piston top surface, and also avoids a large deviation between the measuring point and the point to be measured on the piston top surface, which would reduce measurement accuracy. Its structure is as follows: Figure 2 As shown.

[0039] Thermocouples with a threaded structure on the circumferential surface of the large end are fixedly connected to the piston through the thread, resulting in better sealing and making it less likely for the thermocouple to come out during piston movement. Thermocouples with a smooth surface on the circumferential surface of the large end are installed by pressing, eliminating the need for rotation and tightening during installation and preventing damage to the thermocouple extension wire from tangling.

[0040] For integral pistons, the preferred solution is to avoid the oil passage. This is achieved by machining a long stepped bore, allowing the thermocouple to directly access the piston interior. The installation method is as follows: Figure 3As shown, this design avoids the thermocouple directly reaching the piston interior, thus preventing the thermocouple from extending into the oil passage and affecting the lubricating oil flow. It also prevents electrical faults such as the thermocouple falling off due to the oscillating environment of the lubricating oil within the oil passage.

[0041] For integral pistons, when the temperature sensor cannot avoid the thermocouple measuring point in the oil passage, such as at the piston ring land measuring point, a short stepped hole is machined to allow the thermocouple extension wire to enter the oil passage. A plug hole is machined near the thermocouple measuring point, and the thermocouple extension wire runs inside the oil passage and exits from the plug hole. The installation method is as follows: Figure 4 As shown.

[0042] For a combined piston, the thermocouple extension wire enters the inner oscillation chamber from the outer oscillation chamber through the oil passage. A protective sleeve is installed between the piston top and the piston skirt. After entering the sleeve from the piston top, the thermocouple extension wire exits from the piston skirt. The thermocouple extension wire is arranged close to the wall of the oscillation chamber and fixed with high-temperature resistant epoxy resin to prevent damage to the thermocouple due to piston oscillation and lubricating oil erosion. The extension wire arrangement is as follows... Figure 5 As shown.

[0043] For combined pistons, in order to smoothly lead the thermocouple extension wire from the piston top to the piston skirt and avoid damage to the thermocouple due to piston oscillation and lubricating oil flushing, a protective sleeve is installed between the piston top and the piston skirt, through which the thermocouple extension wire passes.

[0044] There are two types of protective sleeve structures and their corresponding installation methods. Specific Implementation Example 1:

[0046] The first type of protective sleeve structure is as follows: Figure 6 As shown, the protective sleeve consists of a top thread, a middle sleeve, a bottom thread, and a retaining ring. Further, a threaded hole is machined at the teardrop-shaped protrusion on the piston top to secure the top thread of the protective sleeve to the piston top. A tripod fixing bracket is installed on the piston skirt, the structure of which is as follows... Figure 7 As shown, the three legs of the tripod bracket are connected to the piston skirt, and the bottom thread of the protective sleeve is connected to the middle of the bracket, thus completing the fixation of the protective sleeve. Figure 8 As shown. The tripod fixing bracket transfers lateral impacts on the protective sleeve to the three screws at the piston skirt, thus ensuring the sleeve's impact resistance. Specific Implementation Example 2:

[0048] The second type of protective sleeve structure is an external thread structure, such as... Figure 9 As shown, the thermocouple extension wire passes through the protective sleeve. Specifically, a threaded hole is machined on the outside of the oscillation chamber inside the piston skirt to mate with the external thread of the protective sleeve, thereby fixing the protective sleeve in place. Figure 10As shown. This method is simple to process, but it requires a high degree of coaxiality between the extension line and the sleeve.

[0049] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for installing a thermocouple suitable for measuring the piston temperature of an internal combustion engine, characterized in that, The process includes the following steps: machining stepped thermocouple mounting holes on the piston surface, mounting the thermocouple to the piston surface, and extending the thermocouple wire from the piston top into the piston interior and connecting it to an in-cylinder wireless signal transmitter; the thermocouple includes a thermocouple wire and an armored sleeve, characterized in that the armored sleeve includes a large end and a small end, the large end being mounted on the high-temperature combustion gas side, and bearing the high-temperature combustion gas pressure inside the piston through the middle surface between the large end and the small end; for a composite piston, the circumferential surface of the large end has a threaded structure, and for an integral piston, the circumferential surface of the large end has a smooth structure; the armored sleeve is made of the same material as the piston to be tested; the thermocouple is a shell-type thermocouple, and the wall thickness of the end face of the armored sleeve is determined by the material of the armored sleeve, with a minimum wall thickness of 0.5mm for steel armored sleeves and a minimum wall thickness of 1mm for aluminum armored sleeves; For integral pistons, depending on the location of the piston temperature measurement point, when the thermocouple can avoid the oil passage hole, a long stepped hole is machined on the piston to allow the thermocouple extension wire to directly reach the piston interior; when the thermocouple cannot avoid the oil passage hole, a short stepped hole is machined on the piston to allow the thermocouple extension wire to enter the oil passage, and a plug hole is machined at the position where the thermocouple extension wire exits the oil passage, allowing the thermocouple extension wire to pass through the oil passage hole and exit from the plug hole; for combined pistons, the thermocouple extension wire passes through the oil passage hole, enters the inner oscillation chamber from the outer oscillation chamber of the piston, then enters the protective sleeve set between the piston top and the piston skirt, and finally exits from the piston skirt; The protective sleeve includes a top thread, a middle sleeve, a bottom thread, and a retaining ring. A threaded hole is machined at the teardrop-shaped protrusion on the piston top, and the top thread of the protective sleeve is connected to the piston top. A tripod fixing bracket is installed on the piston skirt. An installation hole is machined in the middle of the tripod fixing bracket, and the bottom thread of the protective sleeve is connected to the middle of the tripod fixing bracket. The three legs of the tripod fixing bracket are connected to the piston skirt.

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