JP6084443B2 - Engine control apparatus and control method - Google Patents

Description

  The present invention relates to an engine control device and a control method for switching between all-cylinder operation and reduced-cylinder operation.

  For the purpose of improving fuel efficiency, an engine that performs a reduced-cylinder operation that stops combustion of some of the cylinders is already known. As one of the control methods during the reduced-cylinder operation, there is a method of opening and closing the intake valve and the exhaust valve in the idle cylinder as in the other operating cylinders. At this time, in the idle cylinder, the PV curve of the compression stroke in which the intake valve and the exhaust valve are closed and the piston is raised follows the same path as the PV curve of the expansion stroke in which the intake valve and the exhaust valve are closed and the piston is lowered. I will not take it. In this case, the area of the area surrounded by the PV curves of different paths becomes a loss, and the fuel consumption during the reduced-cylinder operation is reduced.

  In order to reduce the amount of energy loss during reduced-cylinder operation, a method for closing the intake valve and the exhaust valve during reduced-cylinder operation has already been proposed. For example, there is a method of closing an intake valve and an exhaust valve when a piston in a cylinder is near the top dead center of an exhaust stroke (see, for example, Patent Document 1). According to this method, it is enclosed in the cylinder as compared with the case where each valve is closed when the piston is positioned between the top dead center and the bottom dead center or when the piston is positioned near the bottom dead center. The amount of gas is reduced. As a result, expansion and compression of the enclosed gas are repeated in a state where the pressure in the idle cylinder is 1 atm or less. According to this method, the increase in the internal energy of the gas sealed in the cylinder is smaller in the compression stroke than when the valves are closed when the piston is positioned between the top dead center and the bottom dead center. Thus, heat loss due to heat radiation from the gas is also reduced.

Japanese Utility Model Publication No. 5-42652

  However, the mass of the gas sealed in the cylinder varies depending on the timing at which the intake valve and the exhaust valve are closed, even within the range that can be said to be near the top dead center. For example, when the piston is located at the top dead center in the exhaust stroke and both the exhaust valve and the intake valve are open, exhaust gas is sent out to the exhaust passage, while fresh air is sucked from the intake passage. For this reason, the mass of the gas in a cylinder does not necessarily become the minimum at the said timing. Further, for example, if there is an EGR (Exhaust Gas Recirculation) recirculation amount or a change in the supercharging pressure due to the supercharger, the piston position at which the mass of gas in the cylinder is minimized also changes.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine control device and a control method that improve fuel efficiency in reduced-cylinder operation.

An engine control device that solves the above problems is an engine control device that switches between all-cylinder operation and reduced-cylinder operation, and is provided at least in a cylinder that can be stopped and from an in-cylinder pressure sensor that detects the pressure in the combustion chamber , cylinder pressure in a predetermined time period leading to the intake stroke from the exhaust stroke type multiple times, each time to enter the cylinder pressure within the predetermined time period, the cylinder pressure and the input, the crank angle at the time of detecting the cylinder pressure multiplying the volume of the calculated said combustion chamber based on, when the position of the piston the multiplication value is minimized, and the gas quantity minimum position that put the intake stroke from the exhaust stroke, the reduced-cylinder operation condition is established, An engine control device that acquires the minimum gas amount position calculated one cycle before and closes an intake valve and an exhaust valve when the piston is positioned at the minimum gas amount position.

An engine control method that solves the above problem is an engine control method that switches between all-cylinder operation and reduced-cylinder operation, wherein the engine control device is provided in a cylinder that can be stopped and detects the pressure in the combustion chamber. The in-cylinder pressure sensor inputs a plurality of in-cylinder pressures in a predetermined period from the exhaust stroke to the intake stroke, and each time the in-cylinder pressure is input in the predetermined period, the input in-cylinder pressure and the in-cylinder pressure are The volume of the combustion chamber calculated based on the crank angle at the time of detection is multiplied, and the position of the piston where the multiplication value is minimum is set as the gas amount minimum position in the intake stroke to the intake stroke, and the reduced cylinder operation condition is When established, the minimum gas amount position calculated one cycle before is acquired, and the intake valve and the exhaust valve are closed when the piston is positioned at the minimum gas amount position.
It has been found by the inventors' experiments and the like that the in-cylinder temperature is substantially constant in the vicinity of the gas amount decrease period that shifts from the exhaust stroke to the intake stroke. According to this aspect, the piston position at which the gas amount is minimized can be estimated from the multiplication value of the in-cylinder pressure and the volume of the combustion chamber. By closing the intake valve and the exhaust valve when the piston is located at the minimum gas amount position, the loss in the idle cylinder can be minimized, and the fuel efficiency can be improved in the reduced cylinder operation.

  With respect to the engine control device, the engine includes a hydraulic variable valve mechanism that varies opening and closing timings of the intake valve and the exhaust valve, and the control device includes hydraulic oil that flows through the variable valve mechanism. A response delay time from when a drive command is output to the actuator that opens and closes the oil passage to when the intake valve and the exhaust valve are closed is calculated according to the oil temperature and oil pressure of the oil, and the piston It is preferable that the drive command is output to the actuator earlier than the time when the minimum position is reached by the response delay time.

  According to this aspect, since the response delay time is calculated according to the oil temperature and the oil pressure, the accuracy of the response delay time can be improved. Further, since the drive command is output to the actuator at a timing earlier than the minimum gas amount position by the response delay time, the intake valve and the exhaust valve can be closed at the minimum gas amount position.

In the engine control apparatus, it is preferable that the minimum gas amount position is calculated for each cycle from the intake stroke to the exhaust stroke.
According to this aspect, since the minimum gas amount position is updated every cycle, even if the gas amount sucked in the intake stroke fluctuates due to factors such as the EGR amount and the supercharging pressure, the fluctuation is not changed. This can be reflected in the minimum gas amount position.

1 is a schematic view showing an essential part of an engine according to an embodiment. The block diagram which shows the principal part and control apparatus of the engine of the embodiment. The block diagram which shows the principal part and control apparatus of the engine of the embodiment. The flowchart for calculating the gas amount minimum position by the control device. The graph which shows the cylinder pressure and cylinder temperature in each stroke. The flowchart for calculating the response delay by the same control apparatus. The graph which shows the relationship between oil temperature and response delay time. The graph which shows the relationship between oil pressure and response delay time. The flowchart of the reduced cylinder operation control by the control device. The figure which shows the valve timing at the time of all cylinder operation | movement of the embodiment. The figure which shows the valve timing at the time of the cylinder reduction operation | movement of the embodiment. The figure which shows the PV curve in the reduced cylinder driving | operation of the embodiment and a prior art example.

Hereinafter, an embodiment of an engine control device and a control method will be described. In the present embodiment, the engine will be specifically described as a diesel engine.
As shown in FIG. 1, a cylinder head 13 is mounted on a cylinder block 12 in which a cylinder 11 as a cylinder is formed. The cylinder head 13 is formed with a pair of intake ports 18 and a pair of exhaust ports 19 that communicate with the cylinder 11. A piston 16 is accommodated in the cylinder 11 so as to be reciprocally movable by a crank (not shown). A combustion chamber 17 is defined by the piston 16, the cylinder head 13 and the cylinder block 12. The cylinder head 13 is provided with an injector 22 for injecting fuel into the combustion chamber 17.

  An intake valve 20 is attached to each intake port 18. An exhaust valve 21 is attached to each exhaust port 19. Each intake valve 20 is connected to a variable valve mechanism 30 of the intake valve 20. Each exhaust valve 21 is connected to a variable valve mechanism 31 of the exhaust valve 21.

  Further, the cylinder head 13 is provided with an in-cylinder pressure sensor 50 for measuring the pressure in the combustion chamber 17 corresponding to each cylinder 11. The in-cylinder pressure sensor 50 is, for example, a diaphragm sensor, and detects a change in resistance of a strain gauge formed on the diaphragm by an electric signal.

  Further, an EGR pipe (not shown) that connects the exhaust manifold 15 and the intake manifold 14 is connected to the exhaust manifold 15 connected to the exhaust port 19. The EGR pipe is provided with an EGR valve, and a part of the exhaust gas is mixed with the intake air by opening the EGR valve. Further, a turbocharger turbine (not shown) is provided in the exhaust passage downstream of the exhaust manifold 15 to rotate the compressor in the intake passage upstream of the intake manifold 14. Then, the compressed intake air is sent to the intake manifold 14 by the compressor.

  Next, the variable valve mechanisms 30 and 31 and the ECU 10 as an engine control device will be described. Since the variable valve mechanisms 30 and 31 are the same mechanism, the exhaust side variable valve mechanism 31 will be described.

  As shown in FIG. 2, the variable valve mechanism 31 includes a camshaft 32 that extends along the arrangement direction of each cylinder 11. An exhaust cam 33 is pivotally supported on the exhaust side camshaft 32, and an intake cam 33 is pivotally supported on the intake side camshaft 32. The camshaft 32 rotates in conjunction with the crankshaft via a timing chain (not shown). A cam position sensor 26 provided in the vicinity of the cam 33 detects the rotation angle of the cam 33 and outputs it to the ECU 10.

  A rocker shaft 34 is provided on the exhaust valve 21 side of the camshaft 32. The rocker shaft 34 extends in parallel with the camshaft 32. The same number of rocker arms 35 as the number of cylinders are supported on the rocker shaft 34 so as to be swingable.

  A roller 36 is rotatably supported at one end of the rocker arm 35. The roller 36 is slidably contacted to the outer peripheral surface of the cam 33 with respect to the rocker arm 35. A drive shaft 37 </ b> A of the lifter 37 is fixed to the other end of the rocker arm 35.

  The lifter 37 includes a drive shaft 37A and a columnar piston 37P connected to the drive shaft 37A. The piston 37P is accommodated in a sliding hole 39 provided in the push pin 38, and is provided so as to be slidable on the inner surface of the push pin 38.

  The push pin 38 is accommodated in an oil passage forming member 40 provided above the cylinder head 13 so as to be movable up and down. The push pin 38 is formed in a cylindrical shape having a bottom portion, and has a sliding hole 39 for accommodating the piston 37P inside thereof. The push pin 38 includes a plurality of communication holes 41 penetrating in the radial direction. Each communication hole 41 extends from the outer peripheral surface of the push pin 38 toward the radial center of the push pin 38, and connects the outer peripheral surface and the sliding hole 39.

  Further, the push pin 38 is disposed at an angle at which the communication hole 41 and the oil passage 42 formed in the oil passage forming member 40 communicate with the oil passage forming member 40. An electromagnetic valve 43 is provided in the middle of the oil passage 42. The electromagnetic valve 43 can open and close the oil passage 42 under the control of the ECU 10. A pump (not shown) is provided in the middle of the oil passage 42. That is, the hydraulic oil flowing in the oil passage 42 circulates between the pump, the push pin 38 and the electromagnetic valve 43.

  When an ON signal is output from the ECU 10 to the electromagnetic valve 43, the electromagnetic valve 43 is closed. When the solenoid valve 43 is closed, the flow of hydraulic oil is interrupted upstream of the solenoid valve 43. Then, hydraulic oil is introduced between the bottom surface of the sliding hole 39 of the push pin 38 and the bottom surface of the piston 37 </ b> P by the pressure generated by driving the pump, and the hydraulic oil is supplied to the oil passage 42 downstream from the push pin 38. Will not flow. When the lifter 37 is lowered in accordance with the swing of the rocker arm 35 with the electromagnetic valve 43 closed as described above, the push pin 38 is pressed downward via the hydraulic oil between the push pin 38 and the piston 37P. .

  On the other hand, when an OFF signal is output from the ECU 10 to the electromagnetic valve 43, the electromagnetic valve 43 is opened. When the solenoid valve 43 is opened, the oil passage 42 is opened, and the hydraulic oil between the push pin 38 and the piston 37P can flow to the oil passage 42 on the solenoid valve 43 side as the piston 37P descends. . As shown in FIG. 3, even if the piston 37P descends to the lowest position in the movement range with the oil passage 42 opened, the piston 37P does not press the push pin 38 downward. Therefore, the rocking motion of the rocker arm 35 is not transmitted to the push pin 38.

  A bridge 45 is provided below the push pin 38. The bridge 45 is supported by the oil passage forming member 40, and the upper surface thereof is in contact with the bottom surface of the push pin 38. A pair of exhaust valves 21 are fixed below the bridge 45. As shown in FIG. 3, the bridge 45 is biased to an initial position closest to the oil passage forming member 40 by a biasing means (not shown) such as a spring. When the swing of the rocker arm 35 is not transmitted to the push pin 38, the bridge 45 is urged to the initial position and ascends. When the swing of the rocker arm 35 is transmitted to the push pin 38 and the drive shaft 37A of the lifter 37 is lifted, the push pin 38 is also lifted by the bridge 45.

When the bridge 45 is disposed at the initial position, the exhaust valve 21 is disposed at the closed position. As shown in FIG. 2, when the oil passage 42 is closed by the electromagnetic valve 43 and the bridge 45 is pressed downward by the push pin 38, the exhaust valve 21 starts to open. When the piston 37P is located at the lowest position, the lift amount of the exhaust valve 21 is maximized. Furthermore, with the oil passage 42 is closed, the push pin 38 is raised, the exhaust valve 21 begins to close, when the push pin 38 is located at the uppermost exhaust valve 21 is closed.

  The ECU 10 receives rotation angle signals from the crank angle sensor 25 and the cam position sensor 26, respectively. Further, the ECU 10 outputs various signals to the injector 22 and the variable valve mechanisms 30 and 31 based on the rotation angles. Further, an oil temperature sensor 46 and a hydraulic pressure sensor 47 that detect the temperature and pressure of the oil are provided in the middle of the oil passage 42. The ECU 10 inputs detection signals indicating the oil temperature and the oil pressure to the oil temperature sensor 46 and the oil pressure sensor 47.

  During all-cylinder operation, the ECU 10 closes the intake-side and exhaust-side solenoid valves 43 and drives the rotation of the cam 33 to be transmitted to the exhaust valve 21 via the rocker arm 35. During the reduced-cylinder operation, the ECU 10 selects the number and position of the cylinders that stop the combustion, and stops the fuel injection from the injector 22 for the deactivated cylinders. Further, the ECU 10 opens the intake side and exhaust side solenoid valves 43 of the deactivated cylinder. As a result, the rotation of the cam 33 is not transmitted to the intake valve 20 and the exhaust valve 21, and the intake valve 20 and the exhaust valve 21 are maintained in the closed position.

Next, the operation | movement for performing the reduced cylinder driving | running | working by ECU10 of this embodiment is demonstrated using the flowchart in each process.
In this embodiment, the position where the mass of the gas in the combustion chamber 17 is minimized is sequentially calculated from the in-cylinder pressure and the volume of the combustion chamber 17. A method for calculating the minimum gas amount position θmin will be described. This calculation process of the minimum gas amount position is performed for each cycle in which the crank angle is 0 ° to 720 °.

  The ECU 10 sequentially inputs the in-cylinder pressure P detected from the in-cylinder pressure sensor 50 to the pressure in the combustion chamber 17. As shown in FIG. 4, in the calculation process of the minimum gas amount position θmin, the ECU 10 inputs the in-cylinder pressure P during the gas amount decrease period from the exhaust stroke to the intake stroke, for example, a crank angle of 300 ° to 400 ° ( Step S1). The gas amount decrease period is a predetermined period based on 360 ° at which the piston 16 is top dead center.

  Further, the ECU 10 calculates the volume V of the combustion chamber 17 when the in-cylinder pressure P is detected based on detection signals from the crank angle sensor 25 and the cam position sensor 26 when the in-cylinder pressure P is detected. (Step S2). The volume V can be calculated from the position of the piston 16 corresponding to the crank angle and the total volume of the cylinder 11.

The ECU 10 calculates a gas amount minimum position θmin at which the gas mass in the combustion chamber 17 is minimized based on the in-cylinder pressure P and the volume V obtained during the gas amount reduction period (step S3). At this time, the ECU 10 multiplies each in-cylinder pressure P obtained in one cycle by the volume V of the combustion chamber 17 at the time when the in-cylinder pressure P is detected, and obtains a crank angle at which the multiplication value becomes the smallest. The position of the gas in the combustion chamber 17 is estimated to be the minimum.

That is, the mass of the gas sealed in the combustion chamber 17 is expressed by the following equation, where P is the in-cylinder pressure, V is the volume of the combustion chamber 17, R is the gas constant, and T is the in-cylinder temperature.
n = PV / RT
On the other hand, as shown by a chain line in FIG. 5, it turned out by the inventors of the experiments that the cylinder temperature is almost constant in the vicinity of the gas loss period shifts to air suction stroke (300 ° ~400 °) from the exhaust stroke doing. This is because the intake valve 20 starts to open during the gas amount decrease period, and therefore, fresh air having a low temperature is sucked. Therefore, the position where the mass of the gas is minimized is the same as the position where the multiplication value of the cylinder pressure P and the volume V is minimized. Further, since the in-cylinder pressure sensor 50 has higher responsiveness than the temperature sensor, the minimum gas amount position θmin can be accurately calculated.

  On the other hand, as shown by the solid line in FIG. 5, the in-cylinder pressure P is low during the exhaust stroke (approximately 180 ° to 360 °) and the intake stroke (approximately 360 ° to 540 °), but the piston 16 is near the top dead center. Even in the case, the in-cylinder pressure P varies depending on the engine operating conditions as shown in the lower right in FIG. When the overlap between the intake valve 20 and the exhaust valve 21 is provided, the gas amount minimum position θmin tends to be larger than 360 °.

  The calculation of the minimum gas amount position θmin is repeated every cycle. For this reason, the minimum gas amount position θmin is constantly updated, and the minimum gas amount position θmin reflecting the valve timing, EGR amount, supercharging pressure, and the like at that time can be set.

  When the condition of the reduced cylinder operation is satisfied, the timing of closing the exhaust valve 21 and the intake valve 20 is paused by minimizing the mass of gas sealed in the combustion chamber 17 (hereinafter referred to as sealed gas). The amount of energy loss in the cylinder can be minimized. That is, in the idle cylinder, in the compression stroke, the greater the mass of the enclosed gas, the greater the work done on the enclosed gas, and the greater the internal energy change of the enclosed gas. On the other hand, since the area of the inner surface of the cylinder 11 does not change, the greater the internal energy change of the sealed gas that contacts the cylinder 11, the greater the heat loss due to heat dissipation of the sealed gas. The heat loss includes a cooling loss absorbed by the cooling water passing through the wall portion of the cylinder block 12 through the wall portion of the combustion chamber 17 and a radiation loss diffused to the surroundings as radiant heat. For this reason, the heat loss in the idle cylinder can be minimized by reducing the mass of the enclosed gas in the idle cylinder.

  Further, the ECU 10 sequentially calculates the response delay θdy of the variable valve mechanism 31 from the oil pressure and the oil temperature. The response delay θdy is a period of time from when the ECU 10 outputs an ON signal to the solenoid valve 43 until the exhaust valve 21 and the intake valve 20 are opened, and after the OFF signal is output to the solenoid valve 43, the solenoid valve 43 Response delay due to oil characteristics such as response delay until the valve is opened, time required until the hydraulic oil of the push pin 38 is released after the solenoid valve 43 is opened, time required for the bridge 45 to return to the initial position There is a mechanical response delay of the variable valve mechanism 31 and the like.

  First, the ECU 10 calculates a response delay due to the characteristics of the oil. As shown in FIG. 6, the ECU 10 inputs an oil temperature detection signal from the oil temperature sensor 46, and calculates a response delay time according to the oil temperature (step S11). At this time, the ECU 10 reads out a previously stored map for oil temperature, and calculates a response delay time based on the oil temperature and the map. As shown in FIG. 7, in the map for oil temperature, the response delay time increases as the oil temperature decreases. Since the map is based on a constant engine speed NE, when the engine speed NE at that time deviates from the reference, the acquired response delay time is corrected.

  As shown in FIG. 6, the ECU 10 inputs a hydraulic pressure detection signal from the hydraulic pressure sensor 47, and calculates a response delay time corresponding to the hydraulic pressure (step S12). At this time, the ECU 10 reads a map for hydraulic pressure stored in advance, and calculates a response delay time based on the hydraulic pressure and the map. As shown in FIG. 8, in the map for hydraulic pressure, the response delay time increases as the hydraulic pressure decreases. Since this map is also based on a constant engine speed NE, when the engine speed NE at that time deviates from the reference, the acquired response delay time is corrected.

  Next, as shown in FIG. 6, the ECU 10 calculates a response delay θdy (step S13). At this time, the ECU 10 adds a response delay according to the oil temperature, a response delay according to the oil pressure, and a response delay having a constant value other than that to obtain a response delay θdy. And step S11-step S13 mentioned above are repeated for every cycle of crank angle 0 degree-720 degree, or for every several cycles. For this reason, the response delay θdy is constantly updated, and the response delay θdy reflecting the oil temperature and hydraulic pressure at each time point can be obtained.

  Next, processing when actually starting the reduced cylinder operation will be described. This process is repeated from the engine start to the stop. As shown in FIG. 9, the ECU 10 determines whether or not the reduced-cylinder operation condition is satisfied (step S21). At this time, the ECU 10 reads a map that divides the operation region in which the reduced cylinder operation is performed and the operation region in which the all cylinder operation is performed. The map divides the all-cylinder operation region and the reduced-cylinder operation region by the engine speed NE and the command injection amount Qfin. The ECU 10 determines whether or not the engine speed NE and the command injection amount Qfin at that time are included in the reduced-cylinder operation region, and determines that the reduced-cylinder operation condition is satisfied when included in the reduced-cylinder operation. To do.

  When ECU 10 determines that the reduced-cylinder operation condition is not satisfied (NO in step S21), ECU 10 performs all-cylinder operation (step S27). As shown in FIG. 10, during all cylinder operation, for example, the exhaust valve 21 is closed at a position where the piston 16 has passed the top dead center (crank angle 360 °), and the intake valve 20 is connected to the piston 16 at the top dead center. The valve is opened at the position before reaching. At this time, the ECU 10 outputs a drive signal to the electromagnetic valve 43 earlier by the response delay θdy calculated in advance than the opening timing of the intake valve 20 and the closing timing of the exhaust valve 21.

  On the other hand, if it is determined in step S21 that the reduced-cylinder operation condition is satisfied (YES in step S21), the ECU 10 inputs the latest gas amount minimum position θmin calculated in step S2 (step S22). Since the gas amount minimum position θmin input at this time is a value calculated one cycle before, the EGR amount and supercharging pressure at that time are reflected.

  Further, the ECU 10 inputs the latest response delay θdy calculated in step S13 (step S23). Then, the valve opening control position θc for outputting the ON signal to the intake side and exhaust side electromagnetic valves 43 is calculated (step S24). At this time, the ECU 10 subtracts the response delay θdy from the gas amount minimum position θmin to obtain the valve opening control position θc.

The ECU 10 waits for the timing at which the crank angle θ reaches the valve opening control position θc based on the rotation angle input from the crank angle sensor 25 and the cam position sensor 26 (step S25). Crank angle θ as shown in FIG. 11, and reaches the valve opening control position .theta.c (YES in step S25), ECU 10 is opened controls the solenoid valve 43 (step S26).

Solenoid valve 43 opens the oil passage 42 by opening. As shown in FIG. 3, when the oil passage 42 on the exhaust side is opened, even if the piston 37P moves up and down as described above, no pressing force is transmitted to the push pin 38, and the exhaust valve 21 is closed. Maintained. The intake valve 20 is also held in the closed position when the intake-side oil passage 42 is opened by the electromagnetic valve 43.

As shown in FIG. 11, when the ECU 10 outputs an off signal to the solenoid valve 43 of the deactivated cylinder at the valve opening control position θc, the intake valve 20 and the exhaust valve 21 are closed at the gas amount minimum position θmin, respectively. As a result, as compared with the case where the intake valve 20 and the exhaust valve 21 are closed at other timings, a small mass of gas is sealed in the idle cylinder.

As shown in FIG. 1 2, when the gas volume minimum position θmin is not the top dead center, the intake valve 20 and exhaust valve 21 at a timing when the piston 16 is located at the top dead center is closed, the energy loss in the rest cylinder The region is surrounded by the PV curve shown in the upper side of the figure. When the intake valve 20 and the exhaust valve 21 are closed at the minimum gas amount position θmin, the energy loss amount in the idle cylinder is a region surrounded by the PV curve shown in the lower side in the figure. The PV curve when the intake valve 20 and the exhaust valve 21 are closed at the minimum gas amount position θmin has a lower in-cylinder pressure and a smaller energy loss than when the valve is closed at the top dead center. For this reason, the fuel consumption at the time of reduced-cylinder operation can be further improved.

As described above, according to one embodiment of the engine control apparatus, the effects listed below can be obtained.
(1) According to the above embodiment, the ECU 10 that switches between all-cylinder operation and reduced-cylinder operation inputs the in-cylinder pressure from the in-cylinder pressure sensor 50 that is provided in the cylinder that can be stopped and detects the pressure in the combustion chamber 17. Further, the ECU 10 calculates a piston position where the mass of gas in the combustion chamber 17 is minimized from the exhaust stroke to the intake stroke from the in-cylinder pressure and the volume of the combustion chamber 17 to obtain the minimum gas amount position θmin. Further, the ECU 10 closes the intake valve 20 and the exhaust valve 21 at the timing when the piston 16 is positioned at the minimum gas amount position θmin when the reduced-cylinder operation condition is satisfied. In other words, since the temperature variation in the cylinder is small during the gas reduction period from the exhaust stroke to the intake stroke, the piston position at which the gas amount is minimized can be calculated from the in-cylinder pressure and the volume of the combustion chamber 17. Then, by closing the intake valve 20 and the exhaust valve 21 based on the minimum gas amount position θmin, it is possible to minimize the energy loss in the idle cylinder and improve the fuel efficiency in the reduced cylinder operation.

  (2) According to the above embodiment, the engine includes the hydraulic variable valve mechanism 31 that varies the opening / closing timing of the intake valve 20 and the exhaust valve 21. The ECU 10 outputs an ON signal to the electromagnetic valve 43 that opens and closes the oil passage 42 based on the oil temperature and hydraulic pressure of the hydraulic oil flowing through the variable valve mechanism 31 and then closes the intake valve 20 and the exhaust valve 21. The response delay time θdy until the valve is operated is calculated, and an ON signal is output to the electromagnetic valve 43 before the response delay time θdy before the time when the piston 16 reaches the gas amount minimum position θmin. Furthermore, a certain response delay time such as a mechanical delay time of the variable valve mechanism 31 was added to the response delay θdy corresponding to the oil temperature and the hydraulic pressure. For this reason, the accuracy of the response delay time can be improved. Further, since the ON signal is output to the electromagnetic valve 43 before the response delay θdy from the minimum gas amount position θmin, the intake valve 20 and the exhaust valve 21 can be closed at the minimum gas amount position θmin.

(3) In the above embodiment, the ECU 10 calculates the minimum gas amount position θmin for each period from the intake stroke to the exhaust stroke. Therefore, since the minimum gas amount position θmin is updated every cycle, even if the amount of gas sucked in the intake stroke fluctuates due to factors such as EGR amount and supercharging pressure, the fluctuation is minimized. This can be reflected in the position θmin.

In addition, the said embodiment can also be suitably changed and implemented as follows.
In the above embodiment, the electromagnetic valve 43 is closed when an ON signal is input, and is opened when an OFF signal is input. However, the electromagnetic valve 43 is opened when an OFF signal is input, The valve may be closed when.

In the above embodiment, regarded as the cylinder temperature is substantially constant in the gas quantity decrease period, the gas mass, approximates the multiplication value of the cylinder pressure P and the volume V. However, since the in-cylinder temperature changes slightly, when it is necessary to calculate the gas mass more precisely, the in-cylinder temperature is used to calculate the gas mass based on the above formula (n = PV / RT). You may do it.

  The in-cylinder pressure sensor 50 is provided so as to correspond to each cylinder 11, but may be provided corresponding to only the cylinder 11 that can be stopped during the reduced-cylinder operation. Further, a sensor other than the diaphragm type may be used, and a Bourdon tube type or bellows type pressure sensor may be used.

  The variable valve mechanisms 30 and 31 are hydraulically operated variable valve mechanisms and may be mechanisms other than those described above. Further, a variable valve mechanism other than the hydraulically operated type may be used. In this case, the response delay is calculated using a mechanical response delay or the like excluding the response delay due to the characteristics of the hydraulic oil.

  In the above embodiment, the gas amount minimum position θmin is updated every cycle of the engine. The calculation period of the minimum gas amount position θmin may be changed, for example, every two cycles as long as the change in the minimum gas amount position θmin is small.

  In the above embodiment, the engine control device is embodied as a control device for a diesel engine, but may be embodied as a control device for a gasoline engine.

  DESCRIPTION OF SYMBOLS 10 ... ECU as a control apparatus, 11 ... Cylinder as a cylinder, 16 ... Piston, 17 ... Combustion chamber, 20 ... Intake valve, 21 ... Exhaust valve, 30, 31 ... Variable valve mechanism, 43 ... Electromagnetic valve as actuator 50: In-cylinder pressure sensor.

Claims (4)

An engine control device that switches between all-cylinder operation and reduced-cylinder operation,
An in-cylinder pressure in a predetermined period from the exhaust stroke to the intake stroke is input a plurality of times from an in-cylinder pressure sensor that is provided at least in the cylinder that can be stopped and detects the pressure in the combustion chamber,
Each time to enter the cylinder pressure within the predetermined time period, the cylinder pressure and the input, multiply the volume of the combustion chamber, which is calculated based on the crank angle at the time of detecting the cylinder pressure, the multiplication value the position of the smallest piston, the gas volume minimum position that put the intake stroke from the exhaust stroke,
An engine control device that acquires the minimum gas amount position calculated one cycle before the reduced-cylinder operation condition and closes the intake valve and the exhaust valve when the piston is positioned at the minimum gas amount position. The engine includes a hydraulic variable valve mechanism that makes opening and closing timings of the intake valve and the exhaust valve variable.
The controller is
A response delay time from when a drive command is output to an actuator that opens and closes an oil passage until the intake valve and the exhaust valve are closed according to the oil temperature and hydraulic pressure of the hydraulic fluid flowing through the variable valve mechanism And
The engine control device according to claim 1, wherein a drive command is output to the actuator earlier than the time when the piston reaches the minimum gas amount position by the response delay time. The engine control device according to claim 1 or 2, wherein the minimum gas amount position is calculated for each period from the intake stroke to the exhaust stroke. An engine control method for switching between all-cylinder operation and reduced-cylinder operation,
The engine control device comprises:
An in-cylinder pressure in a predetermined period from an exhaust stroke to an intake stroke is input a plurality of times from an in-cylinder pressure sensor that is provided in the cylinder that can be stopped and detects the pressure in the combustion chamber,
Each time to enter the cylinder pressure within the predetermined time period, the cylinder pressure and the input, multiply the volume of the combustion chamber, which is calculated based on the crank angle at the time of detecting the cylinder pressure, the multiplication value the position of the smallest piston, the gas volume minimum position that put the intake stroke from the exhaust stroke,
An engine control method for obtaining the minimum gas amount position calculated one cycle before the reduced-cylinder operation condition and closing the intake valve and the exhaust valve when the piston is positioned at the minimum gas amount position.

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