JPH0486338A - Compression ratio variable device for engine - Google Patents

Abstract

PURPOSE:To obtain an optimum compression ratio in the whole rotating area of an engine by opening a control valve disposed in a cylinder head at the time of starting compression stroke, and closing the valve in the course of the compression stroke. CONSTITUTION:A cylinder head 3 is provided with a control valve as well as a suction valve 4 and an exhaust valve 5, and the control valve 6 is opened and closed by a valve operating device 7. The valve operating device 7 is controlled by a controller 20 which receives various detection signals from sensors detecting the operating state of an engine and calculates opening and closing timing, opening time, and valve stroke of the control valve 6. In this case, the controller 20 is formed of a start detecting means 21 to control the valve operating device 7 in such a manner that the control valve 6 is opened at the time of starting compression stroke and closed in the course of the compression stroke, a start-time compression ratio calculating means 22, an operation-time compression ratio calculating means 23, an environmental condition comparing means 24, a correction compression ratio calculating means 25, and an operation timing calculating means 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine compression ratio variable device that can be used in reciprocating engines such as diesel engines and gasoline engines.

[Conventional technology]

Conventionally, various mechanisms have been developed as devices for varying the compression ratio of an engine. For example, as shown in FIG. 6, the engine compression ratio variable device includes a control valve 6 provided in the cylinder head separately from the intake valve 4 and exhaust valve 5, a sensor 10 for detecting the operating state of the engine, and a control valve 6. A valve operating device 7 that opens and closes the control valve 6, and a valve that opens the control valve 6 at the start of the compression stroke and closes it in the middle of the compression stroke in response to a detection signal from the sensor 10 that is equal to or higher than a predetermined set value. It has a controller 20 for controlling the actuating device 7 (for example, as disclosed in Japanese Patent Application No.
278449).

The compression ratio variable device for the engine detects the engine rotation speed and engine load as the operating state of the engine using a rotation sensor and a load sensor, respectively, and inputs the detection signals to the comparison means of the controller 20. The comparison means compares and judges the detected values from the rotation sensor and the load sensor with a preset set value, and if the detected value is smaller than the set value, the control valve 6 maintains the closed state and compresses. The ratio is constant. However, if the detected values from the rotation sensor and the load sensor are larger than the set values, the comparison means issues a signal to the calculation means of the controller 20. The calculating means calculates the actuation timing of the control valve 6 based on the detection signal from the position sensor that detects the crank angle, and issues commands to the valve operating device 7 regarding the opening timing and closing timing of the control valve 6. . The command signal is transmitted to the valve actuating device 7.
When inputted, the valve operating device 7 opens the control valve 6 at the bottom dead center of the compression stroke, and controls the valve to close after the piston 2 has risen and moved a predetermined distance.

That is, during the compression stroke, while the piston moves a predetermined distance, the control valve 6 remains open, so that the intake air is hardly compressed and the piston makes an ineffective stroke. After the piston has traveled a predetermined distance, the control valve 6 closes and substantial compression of the intake air begins for the first time. Therefore, the volume at the moment when the control valve 6 closes and compression begins becomes the volume before compression, so the compression ratio becomes small.

As described above, the compression ratio variable device of the engine is configured to lower the compression ratio in a high speed rotation region or a high load region of the engine.

As an engine compression ratio variable device, in addition to those equipped with a control valve as described above, there are also those equipped with an auxiliary piston. In other words, this variable compression ratio device equipped with a sub-piston has a sub-cylinder that projects upwardly at the upper part of the combustion chamber of the cylinder, and a sub-piston is disposed within the sub-cylinder, and the variable compression ratio is adjusted according to the operating conditions. The auxiliary piston driving device receives a command from the control circuit and moves the auxiliary piston up and down, thereby changing the volume of the combustion chamber, that is, the compression ratio (for example, as disclosed in Japanese Patent Laid-Open No. 62-282137). , see Japanese Patent Application Laid-Open No. 64-41626).

[Problem to be solved by the invention]

However, the conventional engine compression ratio variable device is configured to change the compression ratio according to the engine speed and engine load, and therefore has the following problems.

For example, in the case of a diesel engine, a high compression ratio is required to obtain the compressed air temperature necessary for combustion when starting the engine. That is, since the temperature of the wall surface of the engine when the engine is started is lower than the temperature during operation, the compression ratio, which is considered optimal from the viewpoint of strength and economy, is too low to start the engine.

On the other hand, if the high compression ratio required at startup is achieved, the pressure inside the cylinder becomes excessive during high-speed rotation and high load, making it impossible to ensure safety in terms of strength. [
See Figure 7 (a)]. In this case, it is possible to construct the engine so that it can withstand high pressure, but in that case, heavy and highly rigid components are required, resulting in a large inertial load and a large friction loss.

Therefore, in order to obtain the high compression ratio required when starting the engine, there is a method of temporarily increasing the compression ratio only at the time of engine startup, and at other times switching to the compression ratio that is optimal from the viewpoint of strength and economy. (see Figure 7 (B))], or a method of increasing the compression ratio at startup and then gradually lowering it [see Figure 7 (C)]. However, with either method, when the engine speed drops during operation, the compression ratio will rise rapidly, so knocking will occur mainly when a high load is applied at low speeds. Such things are not desirable.

In addition, conventional compression ratio variable devices are configured to lower the compression ratio when the engine is rotating at high speed.For example, when the engine is rotating at high speed and the load is low, It will be controlled. However, such control results in poor thermal efficiency and poor fuel efficiency.

The purpose of this invention is to solve the above problems,
When the load is high, the compression ratio is lowered, when the load is low, the compression ratio is increased, and when starting, the starter motor gives a starting signal, and the compression ratio is set to a high value, taking into account the atmospheric temperature and engine speed, and the compression ratio is set to a high value in the entire engine speed range. An object of the present invention is to provide a variable compression ratio device for an engine configured to obtain an optimum compression ratio.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides a starting sensor that detects the voltage of the starter motor, a sensor that detects the engine operating state, a sensor that detects environmental conditions, an intake valve, an exhaust valve, and a control valve provided in the cylinder head, and a sensor that detects the opening and closing of the control valve. It has a valve operating device that operates the valve operating device, and a controller that controls the operation of the valve operating device such that the control valve is opened at the start of the compression stroke and closed in the middle of the compression stroke in response to detection signals from the respective sensors. The present invention relates to a variable compression ratio device for an engine.

Further, in this engine compression ratio variable device, the controller includes a start detection means for determining the presence or absence of a detection signal in the start sensor, and a start detection means that determines the presence or absence of a detection signal from the start sensor, and when the detection signal is input from the start detection means, the controller detects a detection value related to an environmental condition. Compression ratio calculation means at startup that calculates a compression ratio; compression ratio calculation means during operation that calculates a compression ratio based on a detected value regarding the operating state of the engine when no detection signal is input from the startup detection means; an environmental condition comparison means that issues a signal when the detected value is smaller than a set value, and a correction compression ratio calculation that corrects the compression ratio calculated by the operating compression ratio calculation means in response to the signal from the environmental condition comparison means. and operation timing calculation means for calculating the operation timing at which the control valve opens and closes based on a signal from one of the compression ratio calculation means.

Alternatively, the present invention provides a starting sensor that detects the voltage of a starter motor, a sensor that detects the engine operating state,
A sensor for detecting environmental conditions, a sub-cylinder provided at the top of the cylinder, a sub-piston slidably disposed within the sub-cylinder, a sub-piston drive device for operating the sub-piston;
The present invention also relates to an engine compression ratio variable device including a controller that controls the operation of the auxiliary piston drive device that displaces the auxiliary piston to a position corresponding to a target compression ratio in response to detection signals from each of the sensors.

Further, in this engine compression ratio variable device, the controller includes a start detecting means for determining whether or not there is a detection signal from the start sensor, and a start detecting means for determining whether or not there is a detection signal from the start sensor; Compression ratio calculation means at startup that calculates a compression ratio; compression ratio calculation means during operation that calculates a compression ratio based on a detected value regarding the operating state of the engine when no detection signal is input from the startup detection means; an environmental condition comparison means that issues a signal when the detected value is smaller than a set value, and a correction compression ratio calculation that corrects the compression ratio calculated by the operating compression ratio calculation means in response to the signal from the environmental condition comparison means. means,
and a position calculation means for calculating a displacement position of the sub-piston based on a signal from one of the compression ratio calculation means.

Furthermore, in this engine compression ratio variable device, the starting compression ratio calculation means presets an optimal compression ratio for two values of atmospheric temperature and atmospheric pressure in the form of a two-dimensional map,
The compression ratio is calculated from the atmospheric temperature and atmospheric pressure detected by referring to the two-dimensional map.

Further, in this engine compression ratio variable device, the operating compression ratio calculation means presets the optimum compression ratio for three values of engine speed, rack sensor output, and boost pressure in the form of a three-dimensional map; By referring to the three-dimensional map, the compression ratio is calculated from the detected engine speed, rack sensor output, and boost pressure.

[Effect]

The variable compression ratio device for an engine according to the present invention is configured as described above and operates as follows. That is,
In this engine compression ratio variable device, the start detection means of the controller determines whether or not it is time to start based on the presence or absence of a detection signal from the start sensor. When starting the engine,
That is, when the voltage of the starter motor is detected, the compression ratio calculation means of the controller calculates the compression ratio based on the detected value of the environmental condition detection sensor. Specifically, the compression ratio is calculated using a two-dimensional map that determines the optimal compression ratio based on the relationship between atmospheric temperature and atmospheric pressure. In this two-dimensional map, settings are made to obtain the high compression ratio necessary for combustion at startup, and the compression ratio is relatively higher when the atmospheric temperature and pressure are low than when they are high. It is set.

During operation other than when the engine is started, the compression ratio calculation means of the controller calculates the compression ratio based on the detected value of the engine operating state detection sensor. Specifically, the compression ratio is calculated using a three-dimensional map that determines the optimal compression ratio based on the relationship between engine speed, rack sensor output, and boost pressure. In this three-dimensional map, the higher the engine speed and rack sensor output (engine load), the lower the compression ratio is set, but even if the engine speed is high, the compression ratio is not set low when the rack sensor output is low. is set to .

The environmental condition comparison means of the controller compares the detected value of the environmental condition detection sensor with the set value, and when the detected value is small, specifically when the atmospheric pressure is low, the calculated compression ratio is corrected by the compression ratio calculation means. be done.

In a compression ratio variable device equipped with a control valve, the position of the top dead center or bottom dead center of the engine detected by the position sensor and the value of the target compression ratio calculated by the compression ratio calculation means are used by the operation timing calculation means. , the operation timing calculation means calculates the opening/closing timing of the control valve, the pulp stroke, the valve opening/closing period, etc., and issues a command signal to the valve operating device. This command signal drives the valve operating device, opens and closes the control valve, and changes the compression ratio.

In addition, in a compression ratio variable device equipped with an auxiliary piston,
Based on the target compression ratio calculated by the compression ratio calculation means, the position calculation means calculates the position of the sub-piston corresponding to the target compression ratio, and issues a command to the sub-piston drive device. The sub-piston is displaced by this command signal, and the compression ratio changes.

As described above, the present invention detects the voltage of the starter motor when starting the engine and can obtain the high compression ratio necessary for combustion at the time of starting. Instead, the compression ratio can be determined in consideration of environmental conditions, so the optimum compression ratio can be obtained over the entire engine rotation range.

〔Example〕

Embodiments of a variable compression ratio device for an engine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a variable compression ratio device for an engine according to the present invention.
- It is a block diagram showing an example. A piston 2 is arranged within the cylinder 1 so as to be able to reciprocate. The cylinder head 3 is provided with an intake valve 4, an exhaust valve 5, and a control valve 6.

The intake valve 4 and the exhaust valve 5 are opened and closed by a conventional valve mechanism, and the control valve 6
is opened and closed by a separately provided valve operating device 7.

The valve actuating device 7 is actuated by a command from the controller 20. The controller 2o receives information from the engine, that is, various detection signals from a sensor that detects the operating state of the engine, calculates the opening/closing timing, valve opening time, valve stroke, etc. of the control valve 6, and operates the valve operating device accordingly. Issue a command to 7.

This engine compression ratio variable device is similar to the conventional compression ratio variable device shown in FIG. 6 in that it is composed of various sensors, a controller 20, a valve operating device 7, and a control valve 6. They differ in type and in the functions performed by the controller 20.

First, various sensors will be explained. As sensors for detecting the operating state of the engine, a rotation sensor 11 for detecting the number of revolutions of the engine, a rack sensor 12 for detecting engine load, and a boost pressure sensor 13 are provided. Also, as a sensor to detect environmental conditions,
A temperature sensor 14 that detects atmospheric temperature and a pressure sensor 15 that detects atmospheric pressure are provided. Furthermore, a starting sensor 16 that detects the voltage of the starter motor and a position sensor 17 that detects the crank angle are provided.

The controller 20 controls the valve operating device 7 to open the control valve 6 at the start of the compression stroke and close it in the middle of the compression stroke in response to detection signals from each sensor. The controller 20 includes a start detection means 21, a start compression ratio calculation means 22, an operation compression ratio calculation means 23,
It is composed of an environmental condition comparison means 24, a correction compression ratio calculation means 25, and an operation timing calculation means 26.

The starting detection means 21 determines whether or not it is time to start, depending on whether a detection signal is input from the starting sensor 16 that detects the voltage of the starter motor. Naturally, the voltage of the starter motor is detected at the time of starting. The starting detection means 21 issues a command signal to the starting compression ratio calculating means 22 during starting, and issues a command signal to the running compression ratio calculating means 23 during operation other than starting.

The starting compression ratio calculating means 22 calculates the compression ratio based on detected values regarding environmental conditions, that is, atmospheric temperature and atmospheric pressure values, when a command signal is input from the starting detecting means 21. The optimal compression ratio for the two values of atmospheric temperature and atmospheric pressure is set in advance in the form of a two-dimensional map, and the compression ratio is calculated from the detected atmospheric temperature and atmospheric pressure by referring to the two-dimensional map. . As shown in Figure 2, the two-dimensional map has atmospheric pressure C on the vertical axis and atmospheric temperature B on the horizontal axis.
The lower the atmospheric pressure C, the higher the compression ratio, and the lower the atmospheric temperature B, the higher the compression ratio. Therefore, even when starting a diesel engine in a cold region, by achieving a high compression ratio, it is possible to obtain the high temperature necessary for starting the engine, so that the engine starts much better than before.

When the command signal is input from the start detection means 21, the operating compression ratio calculation means 23 calculates the compression ratio based on detected values regarding the operating state of the engine, that is, the engine rotation speed, rack sensor output, and boost pressure. .

For engines equipped with a turbocharger, a large amount of intake air is supplied to the combustion chamber due to supercharging.
During the compression stroke, the pressure in the combustion chamber increases abnormally and the intake air temperature increases, making knocking more likely to occur. Therefore, in order to prevent this knocking, it is necessary to lower the compression ratio when the boost pressure becomes too high. Furthermore, it is necessary to lower the compression ratio when the engine speed is high, and it is also necessary to lower the compression ratio when the engine load is large. Also, when the engine speed is high (but the engine load is small), it is preferable in terms of fuel efficiency not to lower the compression ratio too much.

Taking these into consideration, the optimum compression ratio on flat ground for the three values of engine speed, rack sensor output, and boost pressure is set in advance in the form of a three-dimensional map, and the three-dimensional map is referred to. The compression ratio is calculated from the detected engine speed, rack sensor output, and boost pressure. As shown in Figure 3, the three-dimensional map has engine speed E, rack sensor output D, and boost pressure F on each axis, and boost pressure F, engine speed E, and rack sensor output are higher. The compression ratio is set as low as possible.

The environmental condition comparison means 24 compares the detected value regarding the environmental condition, that is, the atmospheric pressure, with a preset value,
When the detected value is smaller than the set value, that is, when the atmospheric pressure is low, a signal is issued to the correction compression ratio calculation means 25. The above-mentioned setting value is, for example, a value of atmospheric pressure on flat ground.

The correction compression ratio calculation means 25 reads the signal from the environmental condition comparison means 24, and multiplies the compression ratio value calculated by the driving compression ratio calculation means 23, which is considered to be optimal on flat ground, by a correction coefficient to obtain the target compression. Determine the ratio. Therefore, even at high altitudes where the air is rare, the engine can be operated at the optimum compression ratio.

The operation timing calculation means 26 receives the crank angle from the position sensor 17, and calculates the crank angle from the three compression ratio calculation means 22, 23 .
25, and based on this information, the operation timing for opening and closing the control valve 6 is calculated.

Next, the operation of the variable compression ratio device equipped with this control valve will be explained with reference to the flowchart shown in FIG.

First, the voltage A of the starter motor is detected by the starting sensor 16, and the detection signal is input to the starting detecting means 21 of the controller 20 (step 40).

The start detection means 21 determines whether or not it is time to start the engine, depending on whether a detection signal is input.

The starting detection means 21 detects the voltage A of the starter motor.
When this is detected, it is determined that it is time to start, and a command signal is issued to the starting compression ratio calculation means 22. When the voltage A of the starter motor is zero, it is determined that the engine is operating other than during starting, and a command signal is issued to the operating compression ratio calculation means 23 (step 41).

When the voltage A of the starter motor is detected, the detected values of the atmospheric temperature and atmospheric pressure detected by the temperature sensor 14 and the pressure sensor 15 are read into the starting compression ratio calculation means 22 (step 42).

The startup compression ratio calculating means 22 calculates the optimum compression ratio at the detected atmospheric temperature and atmospheric pressure by referring to the two-dimensional map regarding the atmospheric temperature and atmospheric pressure (step 43).

When the voltage of the starter motor is zero, each engine rotation speed detected by the engine rotation sensor 11, the laser sensor 12, and the boost pressure sensor 13,
The rack sensor output and boost pressure are read into the operating compression ratio calculation means 23 (step 44).

The operating compression ratio calculation means 23 calculates the optimum compression ratio by referring to a three-dimensional map regarding the engine speed, rack sensor output, and boost pressure (step 45).

At this time, the environmental condition comparison means 24 determines whether the atmospheric pressure C detected by the pressure sensor 15 is smaller than the set value (step 46).

If the detected atmospheric pressure value C is smaller than the set value CI,
That is, in a place where the air is rare, such as a highland, the correction compression ratio calculation means 25 corrects the compression ratio calculated in step 45 according to the magnitude of the atmospheric pressure detected at that time (step 47).

When the target compression ratio is determined by the above procedure, the position sensor 17 detects the crank angle, that is, the top dead center or bottom dead center position of the piston, and inputs a signal to the operation timing calculation means 26 (step 48).

Position sensor 17 and compression ratio calculation means 22, 23.25
The signal from is input to the operation timing calculation means 26, which calculates the opening/closing timing, valve stroke, valve opening period, etc. of the control valve 6, and issues a command signal to the valve actuation device 7 (step 4
9).

In response to the command signal, the valve operating device 7 opens the control valve 6 at the bottom dead center of the piston during the compression stroke, and after a predetermined period of time, closes the control valve 6 in the middle of the compression stroke (step 50).

When the above processing is completed, the process returns to step 40, and the processing from step 40 to step 50 is repeated.

As described above, this engine's compression ratio variable device is
The optimum compression ratio can be obtained over the entire engine rotation range according to various environmental conditions.

Another embodiment of the engine compression ratio variable device according to the present invention will be described.

FIG. 5 is a block diagram showing a compression ratio variable device for an engine equipped with an auxiliary piston.

In this variable compression ratio device, a sub-cylinder 50 is provided above the cylinder 1 of the engine, and a sub-piston 51 is slidably disposed within the sub-cylinder 50. The sub-piston 51 is driven by the sub-piston driving device 52 in response to a command from the controller 60, and is displaced within the sub-cylinder 50. As the sub-piston 51 is displaced, the volume inside the cylinder 1 changes, so the compression ratio changes.

The controller 60 controls the sub-piston drive device 52 for displacing the sub-piston 51 to a position corresponding to the target compression ratio in response to detection signals from various sensors.

The controller 60 has almost the same configuration as the controller 20 of the variable compression ratio device equipped with a control valve shown in FIG. That is, the controller 60 differs from the controller 20 in that it includes a start detection means 21, a start compression ratio calculation means 22, an operation compression ratio calculation means 23, an environmental condition comparison means 24, and a correction compression ratio calculation means 25. Although they are common, they differ in that position calculation means 61 is provided instead of actuation timing calculation means 26.

The position calculation means 61 calculates the displacement position of the sub-piston 51 based on the compression ratio calculated by the position sensor 17 and the compression ratio calculation means 22, 23.25.

Next, an example of the operation of the variable compression ratio device equipped with this sub-piston will be explained.

The process steps up to calculating the target compression ratio are the same as the process steps from step 40 to step 47 in the variable compression ratio device equipped with a control valve.

When the target compression ratio is calculated in the above process, the compression ratio is input to the position calculation means 61. The position calculation means 61 calculates the position of the sub-piston 51 corresponding to the compression ratio.

Then, based on the command signal from the position calculation means 61,
The sub-piston drive device 52 displaces the sub-piston 51. By displacing the sub-piston 51, the volume of the cylinder 1 changes, so the compression ratio also changes.

〔Effect of the invention〕

Since the engine compression ratio variable device according to the present invention is configured as described above, it has the following effects. In other words, the variable compression ratio device of this engine is configured to detect the voltage of the starter motor when the engine is started, and temporarily attain a high compression ratio only while the starter motor is rotating. In this case, it is possible to obtain the high compressed air temperature necessary for combustion when starting the engine.

Furthermore, the compression ratio is determined by taking into account environmental conditions such as atmospheric temperature and atmospheric pressure, so it can be used in a wide range of atmospheric temperatures and environments, from highlands with thin air, cold regions to scorching deserts. The engine can be started smoothly within the atmospheric pressure range, improving startability.

On the other hand, during operation other than when starting, the compression ratio can be adjusted by taking into account not only the engine speed and engine load, but also the boost pressure in the turbocharger and atmospheric pressure, which improves strength and economy such as fuel consumption. The compression ratio can be adjusted to be optimal from the viewpoint of Therefore, an optimum compression ratio can be obtained over the entire rotational range of the engine.

Also, as mentioned above, the way the compression ratio is determined is different when starting the engine and when operating other than that, so for example, even if the engine speed drops to the speed when starting, , the compression ratio does not rise suddenly. Therefore, even if a high load is applied to the engine when the engine speed decreases, the problem of knocking can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an engine compression ratio variable device according to the present invention, FIG. 2 is a two-dimensional map diagram used in the present invention, and FIG. 3 is a three-dimensional map diagram used in the present invention. 4 is a processing flow diagram showing an example of the operation of the variable compression ratio device of the engine shown in FIG.
FIG. 6 is a block diagram showing another embodiment of the variable compression ratio device for an engine according to the present invention, FIG. 6 is a schematic explanatory diagram showing a conventional variable compression ratio device for an engine, and FIGS. (b) and FIG. 7(c) are explanatory diagrams illustrating the relationship between engine speed and compression ratio. 4, ---- Intake valve, 5 ---- Exhaust valve,
6 control valves,? --------Valve actuator, L L
-----・One revolution sensor (engine operating condition detection sensor), 12------Rack sensor (engine operating condition detection sensor), 13---Boost pressure sensor (engine operating condition detection sensor) ), 14-
・---One rotation sensor (environmental condition detection sensor), 1
5--Pressure sensor (environmental condition detection sensor), 1
6-----~- Starting sensor, 20, 60-1--
- controller, 21 startup detection means, 22---compression ratio calculation means at one start, 23---compression ratio calculation means at one operation, 24. --- Environmental condition comparison means, 25--
・-Correction compression ratio calculation means, 26--・Operation timing calculation means, 50------ Sub cylinder, 51-
-----One sub-piston, 52-11---Sub-piston drive device, 61--One position calculation means. Applicant: IS-Jidosha Co., Ltd.

Claims (6)

[Claims] (1) Starting sensor that detects starter motor voltage;
Sensors that detect engine operating conditions, sensors that detect environmental conditions, intake valves located in the cylinder head,
an exhaust valve and a control valve; a valve operating device for opening and closing the control valve; and a valve actuating device for opening and closing the control valve at the start of a compression stroke and closing the control valve in the middle of the compression stroke in response to detection signals from each of the sensors. An engine compression ratio variable device that includes a controller that controls the operation of a valve operating device. (2) The controller includes a start detection means for determining the presence or absence of a detection signal in the start sensor, and a start-up compression system that calculates a compression ratio based on a detected value related to environmental conditions when a detection signal is input from the start detection means. ratio calculation means,
an operating compression ratio calculating means for calculating a compression ratio based on a detected value regarding the operating state of the engine when no detection signal is input from the start detecting means; an environmental condition comparison means for emitting a signal, a correction compression ratio calculation means for correcting the compression ratio calculated by the operating compression ratio calculation means in response to a signal from the environmental condition comparison means, and each of the compression ratio calculation means. 2. The variable compression ratio device for an engine according to claim 1, further comprising operation timing calculation means for calculating the operation timing at which the control valve opens and closes based on a signal from one of the control valves. (3) A starting sensor that detects the voltage of the starter motor;
A sensor for detecting engine operating conditions, a sensor for detecting environmental conditions, a sub-cylinder provided at the top of the cylinder, a sub-piston slidably disposed within the sub-cylinder;
An engine comprising: a sub-piston drive device that operates the sub-piston; and a controller that controls the operation of the sub-piston drive device that displaces the sub-piston to a position corresponding to a target compression ratio in response to detection signals from each of the sensors. compression ratio variable device. (4) The controller includes a starting detection means for determining the presence or absence of a detection signal from a starting sensor, and a starting compression ratio for calculating a compression ratio based on a detected value related to environmental conditions when a detection signal is input from the starting sensor. a calculation means, an operating compression ratio calculation means for calculating a compression ratio based on a detected value regarding the operating state of the engine when no detection signal is input from the start detection means, and when the detected value regarding the environmental condition is smaller than a set value; an environmental condition comparison means for emitting a signal from the environmental condition comparison means, a correction compression ratio calculation means for correcting the compression ratio calculated by the operating compression ratio calculation means in response to the signal from the environmental condition comparison means, and each of the compression ratio calculation means. 4. The variable compression ratio device for an engine according to claim 3, further comprising position calculation means for calculating the displacement position of the sub-piston based on a signal from one of the pistons. (5) The startup compression ratio calculation means presets the optimum compression ratio for two values of atmospheric temperature and atmospheric pressure in the form of a two-dimensional map, and detects the atmospheric temperature by referring to the two-dimensional map. The variable compression ratio device for an engine according to claim 2 or 4, wherein the compression ratio is calculated from the atmospheric pressure. (6) The operating compression ratio calculation means is configured to calculate the engine rotational speed;
The optimal compression ratio for three values of rack sensor output and boost pressure is set in advance in the form of a three-dimensional map, and the compression ratio is determined from the engine speed, rack sensor output, and boost pressure detected by referring to the three-dimensional map. The compression ratio variable device for an engine according to claim 2 or 4, wherein the engine compression ratio variable device calculates .