CN110173349A - A kind of variable compression ratio engine and its control method - Google Patents

Abstract

The invention discloses a variable compression ratio engine and a control method thereof, mainly comprising a VCR motor, an upper machine case body, a lower machine case body, an upper limit groove, a lower limit groove, an upper crankshaft support, a lower crankshaft support, a power shaft, and a bevel gear , internal thread bevel gears, threaded support shafts, crankshaft couplings, power shaft couplings, top dead center displacement sensors and other existing structures of reciprocating piston engines. The ECU obtains the top dead center displacement through the top dead center displacement sensor, calculates the actual compression ratio m and compares it with the optimal compression ratio ε at the current crankshaft speed calibrated in advance, and controls the VCR motor to drive the bevel gear on the power shaft and the internal thread bevel gear Mesh, push the upper and lower crankshaft supports respectively located in the upper and lower casings to move in the upper and lower limit grooves, change the position of the top dead center of the piston, and achieve the optimal compression ratio, so as to achieve the precise control of the continuously variable compression ratio of the engine.

Description

A variable compression ratio engine and its control method

technical field

This invention relates to reciprocating piston engines, and more particularly to variable compression ratio engines.

Background technique

The compression ratio of a reciprocating piston engine refers to the ratio of the volume of the combustion chamber when the piston is at the bottom dead center to the volume of the combustion chamber when the piston is at the top dead center. Increasing the compression ratio can significantly improve the cycle thermal efficiency of the engine. Under the condition of constant output work, improving the cycle thermal efficiency is equivalent to reducing fuel consumption and carbon emissions. However, the improvement of the compression ratio is not without constraints. The compression ratio of a gasoline engine is subject to the critical compression ratio of knocking, and the diesel engine is subject to the mechanical strength and cost of materials. The existing engines on the market are mainly fixed compression ratio engines, and the actual intake air volume and fuel injection volume of the engine vary greatly with the speed and load, and the fixed compression ratio cannot ensure good utilization of mechanical strength. The existing variable compression ratio technology is mainly divided into the following types: variable piston length, variable connecting rod length, variable crankshaft length, variable crankshaft support position, etc. As disclosed in CN108757206A, the purpose of variable compression ratio is achieved through the relative movement of the inner and outer pistons. The changes in the structure of the combustion chamber brought about by the changes in the positions of the inner and outer pistons have a greater impact on the airflow movement, heat load and cooling of combustion in the cylinder. The degree of influence; as disclosed in CN107829818A, the eccentric connection between the large end of the connecting rod and the crankshaft joint is changed according to the control of the eccentric gear, which increases the mass on the rotating body and brings unfavorable factors to the dynamic balance and the reduction of vibration and noise.

Contents of the invention

The object of the present invention is to overcome the disadvantages of the prior art, and provide a variable compression ratio engine and a control method thereof which realize continuous variable compression ratio and high control precision.

A variable compression ratio engine of the present invention comprises a lower engine casing and an upper casing fixed on the lower casing, a plurality of lower crankshaft supports arranged in parallel and spaced left and right are installed in the lower casing, and each An upper crankshaft support is respectively supported on each of the lower crankshaft supports, and the front and rear ends of the plurality of lower crankshaft supports are respectively slid up and down and connected in the lower limit grooves provided on the front wall and the rear wall of the lower chassis body. The front and rear ends of the upper crankshaft support arranged at intervals are respectively slid up and down and connected in the upper limit grooves provided on the front wall and the rear wall of the upper chassis body, and the depth of the upper limit grooves is smaller than the depth of the lower limit grooves;

The length of the front and rear end of the lower crankshaft support is greater than that of the upper crankshaft support. There is an arc-shaped installation groove in the middle of the top wall of each lower crankshaft support and the middle of the bottom wall of the upper crankshaft support. The mounting grooves are butted to form a bearing bush installation groove that matches the shape of the bearing bush of the crankshaft. The upper bearing bush of each crankshaft bush is installed in the arc-shaped installation groove of the upper crankshaft support and the lower bearing bush is installed in the arc-shaped installation groove of the lower crankshaft support. The crankshaft is installed between the upper and lower bearing shells of multiple bearing shells;

A rectangular groove is opened inwardly in the middle of the bottom wall of each lower crankshaft support, and a connecting through hole is opened vertically in the middle of each lower crankshaft support, and a screw thread is installed in each connecting through hole. The support shaft, the bottom of the threaded support shaft is fixed on the bottom wall of the lower cabinet, and the threaded support shaft located in the groove is connected with an internal thread bevel gear, and the internal thread bevel gear passes through the self-locking trapezoidal thread It is threadedly connected with the threaded support shaft, and there are crankshaft coupling installation grooves respectively opened in the middle of the top wall of the left and right side walls of the lower machine case and the bottom wall of the left and right side walls of the upper machine case. A crankshaft coupling is installed in the installation groove of the crankshaft, and the crankshaft coupling is fixedly connected with the left and right ends of the crankshaft respectively. A power shaft coupling is installed inside, and the top dead center displacement sensor adopts a slider-type linear displacement sensor. The sliding part of the top dead center displacement sensor is installed on the side wall of the rightmost lower crankshaft support. The fixed part of the point displacement sensor is fixedly installed on the boss of the lower limit slot on the far right;

All the lower crankshaft supports are fixedly connected by a power shaft arranged in the horizontal direction. A bevel gear meshing with each internal thread bevel gear is fixed on the power shaft. One end of the power shaft is connected to the power shaft through a power shaft coupling. The output shaft of a VCR motor fixed outside the engine is connected.

A control method for a variable compression ratio engine, comprising the following steps:

The first step is to calibrate the engine speed-piston optimal compression ratio map and the current-piston top dead center position map of the top dead center displacement sensor, and store the current actual compression ratio in the ECU;

In the second step, the ECU obtains the current engine speed according to the current crankshaft position sensor parameters, and reads the engine speed-piston optimal compression ratio map according to the current engine speed. The optimal compression ratio ε at the current speed calibrated in advance; The current of the top dead center displacement sensor reads the current of the top dead center displacement sensor - the piston top dead center displacement in the top dead center position map of the piston, and the actual dead center position of the piston under the current working condition is obtained, and the current working condition is calculated. the actual compression ratio m, and store the calculated current actual compression ratio in the ECU;

In the third step, the ECU compares the numerical relationship between ε and m. When ε>m, the ECU controls the rotation of the VCR motor to drive the power shaft coupling, power shaft, bevel gear, and internal thread bevel gear to drive the lower crankshaft and the upper crankshaft. The support and the crankshaft move toward the cylinder head, and the value of m becomes larger; when ε<m, the ECU controls the rotation of the VCR motor to drive the power shaft coupling, power shaft, bevel gear, and internal thread bevel gear in turn, so that the lower crankshaft supports, The upper crankshaft supports and the crankshaft moves away from the cylinder head, and the value of m decreases; when ε=m, the ECU controls the VCR motor to stop rotating, and at this time the lower crankshaft supports stop moving, and the self-actualization between the internally threaded bevel gear and the threaded support shaft Under the action of locking thread, it stops at the position of required compression ratio ε.

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

The rotation time and rotation direction of the VCR motor are controlled by the ECU to control the relative distance between the crankshaft and the cylinder head, and the top dead center displacement sensor is used to judge whether the compression ratio has reached the desired compression ratio. The top dead center displacement sensor should have the function of detecting the relative position change of the top dead center. It is a slider type linear displacement sensor. The limit groove in the upper chassis not only ensures the movable support of the upper crankshaft, but also serves as a support for the lower crankshaft. The limit device is mainly realized by the processing size of the limit groove of the upper chassis body being shallower than the limit groove of the lower chassis body, so that when the top dead center displacement sensor fails, the crankshaft support will not move upward without restriction.

The invention realizes continuous variable compression ratio through a simple structure, utilizes screw rotation to control the variation of the compression ratio, and has high control precision. Without changing the existing mature components such as the combustion chamber structure and the crank connecting rod mechanism, the structure of the existing engine is changed slightly, and the impact on the cost of the engine is small.

Description of drawings

Fig. 1 is a top view schematic diagram of the structure of the lower casing of a variable compression ratio engine of the present invention;

Fig. 2 is a schematic bottom view of the upper machine case structure of a variable compression ratio engine of the present invention;

Fig. 3 is a partial left view of a structural schematic diagram of a variable compression ratio engine of the present invention;

Fig. 4 is a control flow chart of a variable compression ratio engine of the present invention.

Detailed ways

The present invention will be further explained below in conjunction with the embodiments and drawings, but this should not be used as a limitation to the protection scope of the present application.

The present invention is the improvement on existing engine structure, except the structure shown in Fig. 1, Fig. 2, Fig. 3, all the other all adopt existing structure and get final product.

The present invention as shown in the accompanying drawing is a kind of variable compression ratio engine, comprises the lower machine case body 6 of engine and the upper machine case body 13 that is fixed on the lower machine case body 6, is installed in described lower machine case body 6 left and right parallel A plurality of lower crankshaft supports 1 arranged at intervals, each lower crankshaft support 1 is respectively supported with an upper crankshaft support 15, and the front and rear ends of the plurality of lower crankshaft supports 1 are respectively slid up and down and connected in the lower chassis body 6 In the lower limit groove 8 provided on the front wall and the rear wall, the front and rear ends of the upper crankshaft support 15 arranged in parallel and spaced intervals are respectively slid up and down and connected to the openings provided on the front wall and the rear wall of the upper chassis body 13. In the upper limit groove 14 , the depth L of the upper limit groove 14 is smaller than the depth of the lower limit groove 8 . During operation, the lower crankshaft support 1 is controlled to move up to the height of the highest point not higher than the height of the lower limit groove 8, so that the lower crankshaft support 1 can only move up and down in the lower limit groove 8, but cannot move in the upper limit groove 14.

The length of the front and back ends of the lower crankshaft support 1 is greater than the length of the front and rear ends of the upper crankshaft support 15, and an arc-shaped mounting groove is respectively opened in the middle of the top wall of each lower crankshaft support 1 and the bottom wall of the upper crankshaft support 15, and the upper and lower two correspond to each other. The provided arc-shaped mounting grooves are docked to form a bearing bush installation groove that matches the shape of the crankshaft bearing bush 12. The upper bearing bush of each crankshaft bearing bush 12 is installed in the arc-shaped installation groove of the upper crankshaft support 15 and the lower bearing bush is installed in the lower crankshaft support. 1, a crankshaft 16 is installed between the upper and lower bearing bushes of a plurality of bearing bushes 12. Crankshaft is then connected with connecting rod, and connecting rod is connected with piston, and connection mode is prior art, and connecting rod, piston are not drawn in the figure.

A rectangular groove is inwardly opened in the middle of the bottom wall of each lower crankshaft support 1, and a connecting through hole is opened vertically in the middle of each lower crankshaft supporting 1, and a connecting through hole is installed in each connecting through hole. A threaded support shaft 7, the bottom of the threaded support shaft 7 is fixed on the bottom wall of the lower cabinet body 6, and an internal thread bevel gear 5 is connected to the threaded support shaft 7 at the groove position, and the internal thread bevel gear The gear 5 is threadedly connected with the threaded support shaft 7 through a self-locking trapezoidal screw thread, and a crankshaft coupling is respectively arranged in the middle of the top wall of the left and right side walls of the lower machine case 6 and the bottom wall of the left and right side walls of the upper machine case 13. A shaft coupling installation groove 2, a crankshaft coupling 11 is installed in each crankshaft coupling installation groove, and the crankshaft coupling is fixedly connected with the left and right ends of the crankshaft respectively. During use, one of the crankshaft The coupling is connected with the pulley to drive accessories such as the starter motor, and the other crankshaft coupling is used as the power output end, which can be connected with a clutch or a dynamometer. The connection of the crankshaft coupling with the crankshaft, the connection with the power end and the connection with the belt pulley are all existing technologies, and the existing structure can be adopted. A through hole is formed on the right side wall of the lower cabinet body 6, and a power shaft coupling 10 is installed in the through hole. The top dead center displacement sensor 9 adopts a slider type linear displacement sensor, and the sliding part of the top dead center displacement sensor 9 is installed on the side wall of the lower crankshaft support 1 on the far right, and the fixed part of the top dead center displacement sensor It is fixedly installed on the boss of the lower limiting groove 8 on the far right, and the relative displacement between the sliding part and the fixed part of the sensor is the displacement of the crankshaft support, that is, the displacement of the top dead center of the piston.

All the lower crankshaft supports 1 are fixedly connected through the power shaft 3 arranged in the horizontal direction. The power shaft 3 is fixed with a bevel gear 4 meshing with each internal thread bevel gear 5. One end of the power shaft 3 passes through The power shaft coupling 10 links to each other with the output shaft of a VCR motor fixed on the outside of the engine. The VCR motor is an existing servo motor, and the connection mode adopts the existing structure.

The working process of this device is as follows:

The VCR motor rotates under the control of the ECU, and the generated power is transmitted to the bevel gear 4 fixed on the power shaft 3 through the power shaft coupling 10. The bevel gear 4 meshes with the internal thread bevel gear 5, and the internal thread bevel gear 5 is self-locking. The trapezoidal thread is connected with the threaded support shaft 7, and the internal thread bevel gear 5 can rotate around the threaded support shaft 7 driven by the VCR motor and push the lower crankshaft support 1 and the upper crankshaft support 15 up and down in the lower limit groove 8 and the upper limit groove 14 Moving, the lower crankshaft support 1 and the upper crankshaft support 15 are equipped with crankshaft bearing bush 12 and crankshaft 16, the crankshaft 16 is connected with the connecting rod, and the connecting rod is connected with the piston. When the ECU controls the rotation of the VCR motor, the top dead center position of the piston changes, thereby Change the engine compression ratio.

The combustion of fuel in the cylinder pushes the piston to move, the piston pushes the connecting rod, and the connecting rod drives the crankshaft 16 to rotate, and the crankshaft 16 is connected with the clutch outside the engine through the crankshaft coupling 11 to realize power output.

Control method of the present invention (control map sees Fig. 4) comprises the following steps:

Compared with the existing calibration parameters, the control method of the present invention includes the following steps:

The first step is to calibrate the engine speed-piston optimal compression ratio map and the current-piston top dead center position map of the top dead center displacement sensor.

In the second step, the ECU obtains the current engine speed according to the current crankshaft position sensor parameters, and reads the engine speed-piston optimal compression ratio map according to the current engine speed. The optimal compression ratio ε at the current speed calibrated in advance; The current of the top dead center displacement sensor 9 reads the current of the top dead center displacement sensor-piston top dead center displacement x in the top dead center position map of the piston, obtains the actual dead center position of the piston under the current working condition, and calculates the current working condition the actual compression ratio m under the condition, and store the calculated current actual compression ratio in the ECU.

When the compression ratio does not change, the physical quantities, symbols and units correspond to the following table 1:

Table 1. Description of physical quantities, units and symbols

Equivalent clearance: the sum of the distance from the top dead center of the piston to the cylinder head and the quotient obtained by dividing the volume of the piston pit by the area of the piston.

Regulations: the top dead center displacement is x.

At this time, the current actual compression ratio is

In the third step, the ECU compares the numerical relationship between ε and m. When ε>m, the ECU controls the rotation of the VCR motor to drive the power shaft coupling 10, power shaft 3, bevel gear 4, and internal thread bevel gear 5 to drive the lower crankshaft. Support 1, upper crankshaft support 15, and crankshaft 16 move toward the cylinder head, and the value of m becomes larger; when ε<m, the ECU controls the rotation of the VCR motor to drive the power shaft coupling 10, power shaft 3, bevel gear 4, inner Driven by threaded bevel gear 5, the lower crankshaft support 1, upper crankshaft support 15, and crankshaft 16 move away from the cylinder head, and the value of m decreases; when ε=m, the ECU controls the VCR motor to stop rotating, and at this time the lower crankshaft support 1 stops Move, and stop at the position of required compression ratio ε under the effect of the self-locking thread between the internally threaded bevel gear 5 and the threaded support shaft 7.

Claims (2)

1. a kind of variable compression ratio engine, what it is including engine lower case body (6) and the upper case that is fixed on lower case body Body (13), it is characterised in that: multiple lower Curved shaft supports of left and right parallel interval setting are installed in the lower case body, Each support is provided with one upper Curved shaft support (5), the front and back two of multiple lower Curved shaft supports respectively on lower Curved shaft support End is slided up and down respectively in the lower limit slot (8) for being connected to and opening up on antetheca and rear wall in lower case body, between multiple left and right are parallel It is slided up and down respectively every the rear and front end of the upper Curved shaft support (5) of setting and is connected to upper case body (3) interior antetheca with after In the upper limit position groove (4) opened up on wall, the upper limit position groove depth is less than lower limit groove depth；

The front and back end length of lower Curved shaft support is greater than the front and back end length of upper Curved shaft support (15), on the top of each lower Curved shaft support An arc mounting groove, the upper and lower two arc installations being correspondingly arranged are had among wall and among upper Curved shaft support bottom wall Slot docks the bearing shell mounting groove to be formed and be coincide with the bearing shell shape of crankshaft, and the top bearing shell of each crankshaft bearing liner (12) is mounted on song In the arc mounting groove of axis support and lower bearing is mounted in the arc mounting groove on lower Curved shaft support (1), a crankshaft (1) It is mounted between the upper and lower bearing shell of multiple bearing shells；

A rectangular recess is inwardly provided among the bottom wall of each lower Curved shaft support, in the centre of each lower Curved shaft support along perpendicular Histogram is mounted on a threaded support axle (7), the screw thread branch to a connection through-hole is provided in each connection through-hole The bottom of support axis is fixed on the bottom wall of lower case body, and internal screw thread cone tooth is connected in the threaded support axle for being located at concave part position Wheel, the internal screw thread bevel gear (5) is threadedly coupled by self-locking type trapezoidal thread with threaded support axle (7), under described Crankshaft connection is had among the roof of the left and right sidewall of box body and among the bottom wall of the left and right sidewall of upper case body (13) Axis device mounting groove (2) is mounted on a crankshaft shaft coupling (11), the crankshaft connection in each crankshaft shaft coupling mounting groove The left and right ends of axis device and crankshaft are fixedly linked respectively, and a through-hole is provided on the right side wall of lower case body, lead in described It is equipped in hole line shaft shaft coupling (10), top dead centre displacement sensor (9) uses slider type linear displacement transducer, most right The slipper of top dead centre displacement sensor is installed, the top dead centre, which is displaced, to be passed on the side wall of the lower Curved shaft support (1) of side The fixed part of sensor is fixedly mounted on the boss of lower limit slot (8) of the rightmost side；

All lower Curved shaft support (1) is fixedly linked by the line shaft (3) arranged in the horizontal direction, solid in the line shaft Surely there is the bevel gear (4) that cooperation is engaged with each internal screw thread bevel gear (5), described line shaft one end passes through line shaft shaft coupling The output shaft for the VCR motor for being fixed on external engine with one is connected.

2. the control method of variable compression ratio engine according to claim 1, it is characterised in that the following steps are included:

The first step is determined on electric current-piston of engine speed-piston optimal compression ratio arteries and veins spectrogram and top dead centre displacement sensor only Point position arteries and veins spectrogram；

Second step, ECU obtains present engine revolving speed according to current crankshaft position sensor parameter, according to present engine revolving speed Read optimal compression ratio ε under the current rotating speed demarcated in advance in engine speed-piston optimal compression ratio arteries and veins spectrogram；ECU root In the electric current-piston top dead center position arteries and veins spectrogram for reading top dead centre displacement sensor according to the electric current of top dead centre displacement sensor (9) Piston top dead center displacement, obtain the practical top dead center position of current working lower piston, calculate the actual compression under current working Than m, and by the currently practical compression ratio of calculating, there are in ECU；

Third step, ECU compares the numerical relation of ε and m, and as ε > m, ECU controls the rotation of VCR motor and successively drives line shaft shaft coupling Device (10), line shaft (3), bevel gear (4), internal screw thread bevel gear (5) transmission make lower Curved shaft support (1), upper Curved shaft support (15), Crankshaft (1) is mobile towards cylinder cap direction, and m value becomes larger；As ε < m, ECU controls the rotation of VCR motor and successively drives line shaft shaft coupling Device (10), line shaft (3), bevel gear (4), internal screw thread bevel gear (5) transmission, make lower Curved shaft support (1), upper Curved shaft support (15), to far from the movement of cylinder cap direction, m value reduces crankshaft (1)；As ε=m, ECU controls VCR motor stalls, this is at present Curved shaft support (1) stops movement, and self-locking thread between interior screw thread bevel gear (5) and threaded support axle (7) under the action of is parked in The position of required compression ratio ε.