JPH0426705Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Field of industrial application) The invention is used for automotive cooling cycles,
The present invention relates to a control device for a variable capacity swash plate compressor capable of changing the internal volume of a compression chamber.

(Prior Art) FIG. 6 is a diagram showing a cooling cycle 1 used in a general automobile air conditioner. When a compressor 3 is driven by an engine (not shown) via a belt, a pulley 2, and a magnetic clutch 2a, the compressor 3 adiabatically compresses the gaseous refrigerant to a high temperature and high pressure, and supplies the gaseous refrigerant to a condenser 4. In this condenser 4, the refrigerant is cooled by exchanging heat with external air, and becomes a high-pressure liquid refrigerant.
The refrigerant that has passed through the liquid tank 5, which temporarily stores this liquid refrigerant and removes moisture and dust from the refrigerant,
The refrigerant is throttled and expanded in the expansion valve 6 and flows into the evaporator 7 as a low-pressure mist of refrigerant. As a result, the air flowing into the vehicle interior is cooled by the evaporator 7 and becomes cold air, thereby cooling the vehicle interior.

When the cooling cycle 1 is activated, it has the effect of dehumidifying the air flowing into the vehicle interior, so the cooling cycle 1 can be used not only in the summer but also in the spring.
It is designed to operate in both summer and winter. In the normal compressor 3, compressor 3
The amount of refrigerant discharged per revolution of the shaft portion is always constant, and the amount of refrigerant flowing into the evaporator 7 is controlled by the expansion valve 6 according to the heat load. In order to prevent the condensed water adhering to the outer surface of the evaporator 7 from freezing, if the outer surface of the evaporator 7 falls below a predetermined temperature, a thermoswitch 8 and an amplifier 9 are used to turn off the compressor 3. I'm trying to stop it. Therefore, when the outside air temperature is low and the heat load on the evaporator 7 is small, such as in winter,
The compressor 3 is turned on and off more frequently by the clutch 2a than when the heat load is large, such as during summer. By this,
We aim to save energy by obtaining power consumption that corresponds to the heat load of the evaporator, that is, the heat load of the cooling cycle (hereinafter referred to as "cycle load"),
It also prevents frost.

However, in such a conventional compressor 3, the amount of refrigerant discharged per revolution is always constant, so the compressor must also rotate at a high speed, especially when the engine speed is high. However, it becomes difficult to control the refrigerant flow rate according to the cycle load using only the expansion valve, and power consumption inevitably increases.

Therefore, recently, as the compressor 3 used in such a cooling cycle 1, the
A variable capacity swash plate type compressor having a structure shown in Japanese Patent No. 158382 has been proposed. In this variable capacity swash plate type compressor, the drive swash plate that reciprocates the piston changes the pressure in the crank chamber installed inside, thereby changing the stroke of the piston according to the suction pressure of the compressor. The maximum stroke (maximum cooling power) occurs when low pressure is introduced into the crank chamber, and the minimum stroke (minimum cooling power) occurs when high pressure is introduced into the crank chamber, and the discharge amount of the compressor per rotation of the rotor changes. It is designed to do so. Therefore, in such a variable capacity compressor, a desired amount of refrigerant depending on the cycle load is circulated within the cooling cycle while the suction pressure of the compressor is kept constant.

According to such a variable capacity compressor, for example, when the outside air temperature is low and the heat load is small, but when the cooling cycle 1 is operated to perform dehumidification in the evaporator 7, the refrigerant flowing through the entire cooling cycle 1 is Since the amount of refrigerant is small, the evaporation pressure of the refrigerant in the evaporator 7 is prevented from becoming too low due to excessive throttling in the expansion valve 6. Therefore, it is possible to avoid a so-called freezing phenomenon of the evaporator 7 at low load, which causes the condensed water in the evaporator 7 to freeze, and therefore a thermoswitch or the like to prevent this is not necessary.

Furthermore, even when the outside air temperature is high and the heat load is large, the capacity of the compressor changes accordingly, resulting in a reduction in power consumption.

(Problem to be solved by the invention) However, in such a variable displacement swash plate type compressor, the sliding parts between the piston and the cylinder were lubricated by using the pressure difference generated before and after the piston. If the pressure in the crank chamber formed on the rear side of the piston becomes equal to the discharge pressure of the compressor, the pressure difference between the front and rear of the piston during the discharge process disappears, and there is a risk that this sliding part will not be sufficiently lubricated. It was hot.

The present invention was made in view of the above circumstances, and aims to provide a control device for a variable capacity swash plate type compressor that contributes to energy saving and also improves lubrication of the sliding parts of the piston. .

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, the present invention integrates a plurality of pistons, which are mounted in a cylinder block so as to be able to reciprocate in the axial direction, into a drive shaft. The piston is rotated and reciprocated by a driving swash plate attached so that its inclination angle can be changed, and the pressure in the compression chamber formed in front of the piston and the pressure in the crank chamber formed in the rear of the piston are adjusted. In the variable capacity swash plate type compressor, the stroke of the piston is changed by changing the inclination angle of the driving swash plate according to a change in the differential pressure of the variable capacity swash plate type compressor. a cycle load detection means for detecting the cycle load; a cycle load comparison means for comparing whether the cycle load detected by the cycle load detection means is equal to or higher than a predetermined value; a crank chamber pressure detection means for detecting the pressure in the driving crank chamber; a compressor discharge pressure detection means for detecting the pressure of refrigerant discharged from the compressor; and whether the differential pressure between the pressure detected by the compressor discharge pressure detection means and the pressure detected by the crank chamber pressure detection means is less than or equal to a predetermined pressure. and a crank chamber pressure control means for changing the pressure in the crank chamber according to output signals from the crank chamber pressure comparing means and the cycle load comparing means, When the differential pressure compared by the comparison means is less than a predetermined pressure, the crank chamber pressure control means preferentially reduces the pressure in the crank chamber based on the output signal from the crank chamber pressure comparison means. It is characterized by control.

(effect) Next, the operation of the present invention will be explained based on FIG.

First, the thermal load acting on the evaporator in the cooling cycle is detected as a cycle load by the cycle load detection means 70. at the same time,
The crank chamber pressure detection means 73 detects the pressure inside the crank chamber, and the compressor discharge pressure detection means 74
Detects the refrigerant pressure on the discharge side of the compressor. Next, the differential pressure between the pressures detected by the crank chamber pressure detecting means 73 and the compressor discharge pressure detecting means 74 is compared and calculated by the crank chamber pressure comparing means 75. If this differential pressure is below a predetermined pressure, the crank chamber pressure is approaching the compressor discharge pressure, so in this case, the crank chamber pressure is forcibly reduced by using the crank chamber pressure control means. It is. As a result, the pressure in the crank chamber is always set lower than the compressor discharge pressure by a predetermined pressure, and lubricating oil is circulated along with the refrigerant toward the crank chamber through the gap between the piston and cylinder, constantly lubricating this sliding part. I will do it.

Further, if the differential pressure calculated by the crank chamber pressure comparison means 75 is larger than a predetermined pressure,
According to the output signal of the cycle load comparison means 71,
The crank chamber pressure control means 72 is controlled. This cycle load comparison means performs a comparison calculation to determine whether the cycle load detected by the cycle load detection means 70 is equal to or greater than a predetermined value. If the cycle load calculated by the cycle load comparison means 71 is equal to or higher than a predetermined value, it is considered that a large load is acting on the cooling cycle. It adjusts the pressure in the room, increases the stroke of the reciprocating piston, and flows the appropriate amount of refrigerant into the cycle in response to the heavy load. Furthermore, if the cycle load calculated by the cycle load comparison means 71 is less than a predetermined value, it is considered that the heat load acting on the cooling cycle is relatively small, so in this case, the crank chamber pressure control means 72 , controls the pressure in the crank chamber,
The stroke of the reciprocating piston is made smaller, allowing an appropriate flow rate of refrigerant to flow within the cycle in accordance with the small heat load.

(Example) Examples of the present invention will be described below.

Figure 1 is a block diagram showing the configuration of the present invention;
The figure is a schematic configuration diagram of a variable capacity swash plate compressor and its control device according to an embodiment of the present invention, and FIG. 3 is a flowchart showing the operation of the embodiment.
4A to 4C are schematic sectional views of a variable capacity swash plate type compressor according to the same embodiment, and FIGS. 5A and 5B are sectional views of essential parts of the piston in the compressor according to the same embodiment, as shown in FIG. The same reference numerals are given to the same members, and some explanations thereof will be omitted.

As shown in FIGS. 2 and 4, the variable capacity swash plate compressor 50 according to this embodiment includes a cylinder block 24, a crankcase 17 attached to the rear end of the cylinder block 24, and a crankcase 17 attached to the tip of the cylinder block 24. The compressor body 10 includes a head 30. For example, five pistons 23 are mounted within a cylinder 25 formed in the cylinder block 24 so as to be able to reciprocate in the axial direction. On the other hand, a crank chamber 12 is formed in the crankcase 17, and a drive rod 11a is fixed to the drive shaft 11, which is rotatably supported by the cylinder block 24 and the crankcase 17.
A drive swash plate 13 is mounted within the crankcase 12 so as to be rotatable about a pin 11b.
Therefore, this drive swash plate 13 rotates together with the drive shaft 11, and also rotates together with the drive shaft 11.
The angle of inclination relative to the base is freely variable.

A non-rotating wobble plate 16 is in contact with the drive swash plate 13 through a thrust bearing 14 at its radial end surface and a radial bearing 15 at its inner peripheral surface. The angle changes as the inclination angle changes. The movement of the non-rotating wobble plate 16 in the thrust direction is regulated by a thrust washer 20 and a snap spring 21. The non-rotating wobble plate 16 is connected to a shoe 19 slidably connected to a guide pin 18 fixed to a casing 17.
Rotation is prevented and movement in the direction of the drive shaft 11 is guided.

The piston 23 and the non-rotating wobble plate 16 are connected by a rod 22, and as the inclination angle of the drive swash plate 13 changes, the reciprocating stroke of each piston 23 is changed via the non-rotating wobble plate 16. Things are starting to change.

A valve plate 27 is attached between the cylinder block 24 and the head 30.
A compression chamber 26 is formed on the front surface of the piston 23, and a crank chamber 1 is formed on the rear surface of the piston 23.
It communicates with 2. As shown in the figure, this valve plate 27 has a suction port 28a that communicates with a suction port 29 formed in the head 30, and a discharge port 28a that communicates with a discharge port 33 formed in the head 30.
b is formed. Furthermore, this valve plate 27 has an inlet 2 during the suction stroke when the piston 23 moves backward.
A suction valve 34a is installed which opens the suction valve 8a and closes the suction port 28a during the discharge process.
The discharge valve 34 opens the discharge port 28b during the discharge process and closes the discharge port 28b during the suction process when the valve 3 moves forward.
b is installed.

The inclination angle of the drive swash plate 13 is changed by changing the pressure difference before and after the piston 23, that is, by changing the pressure inside the crank chamber 12. In order to control this pressure, a pressure control valve 51 is attached to the head 30, and a valve body 52 embedded in the head 30 has a
A suction side pressure chamber 32 is formed which communicates with the suction port 29 via a communication path 31. This valve body 52 has a supply passage 53 formed in the cylinder block 24 and the head 30, and a suction port 29.
A suction-side communication passage 54 is formed that communicates the two via the suction pressure chamber 32 and the communication passage 31. Further, a discharge side communication passage 55 is formed in the valve body 52, which communicates the discharge port 33 with the supply passage 53 via a discharge side pressure chamber 35 formed in the head 30.

A first electromagnetic valve 57 for opening and closing the suction side communication passage 54 is provided in the cylinder body 56 provided in the valve body 52.
Further, a second electromagnetic valve 58 for opening and closing the discharge side communication passage 55 is provided. These electromagnetic valves 57 and 58 are provided with a resilient force by a coil spring 59 in the direction of closing the communication passages 54 and 55, respectively.

In order to control the opening and closing of the first electromagnetic valve 57, the pressure control valve 51 actually has a
An electromagnetic coil 60 is provided. Further, in order to control opening and closing of the second electromagnetic valve 58, an electromagnetic coil 61 is provided on the valve body 52. These electromagnetic coils 6
0 and 61 are connected to a microcomputer (hereinafter simply referred to as "microcomputer") 62 shown in FIG. 2, which includes a built-in circuit corresponding to the crank chamber pressure control means 72. In addition to the crank chamber pressure control means 72 shown in FIG. 1, the microcomputer 62 includes a cycle load comparison means 71 and a crank chamber pressure comparison means 7
It has a built-in circuit equivalent to 5. Further, a pressure sensor 63 for detecting the pressure of the refrigerant on the outlet side of the evaporator 7 is connected to the microcomputer 62, as shown in FIG. This pressure sensor 63 corresponds to the cycle load detection means 70 shown in FIG.
The heat load acting on the cooling cycle will be detected. Furthermore, the microcomputer 62 includes the crank chamber 1
A pressure sensor 64 for detecting the internal pressure of 2 is connected. This pressure sensor 64 corresponds to the crank chamber pressure detection means 73 shown in FIG.
Furthermore, the microcomputer 62 also includes a compressor 5.
A pressure sensor 65 is connected to detect a discharge side refrigerant pressure of 0 (hereinafter referred to as "comp discharge pressure"). This pressure sensor 65 corresponds to the compressor discharge pressure detection means 74 shown in FIG.

Next, the operation of the control device for such a variable capacity swash plate compressor will be explained based on the flowchart shown in FIG.

In step 80, when the automobile cooling cycle is activated and the control device according to the present embodiment is activated, first, the microcomputer 62 shown in FIG.
The crank chamber pressure Pc is read into the microcomputer 62 by the pressure sensor 64 connected to the
81).

Almost simultaneously, in step 82, the compressor discharge pressure Pd is read into the microcomputer 62 by the pressure sensor 65 shown in FIG.

Next, in step 83, the crank chamber pressure comparison means 75 shown in FIG.
Compare whether the differential pressure (Pd - Pc) with When (Pd-Pc)≦Po, it indicates that the crank chamber pressure Pc is approaching the compressor discharge pressure Pd, and in this case, go to step 86, otherwise go to step 84. It's becoming like that. Note that the fact that the crank chamber pressure is close to the compressor discharge pressure indicates that the cycle load is low.

In step 84, the pressure sensor 63 shown in FIG.
The refrigerant pressure on the discharge side of the evaporator 7, that is, the refrigerant pressure on the suction side of the compressor 50 (compressor suction pressure) Ps is read into the microcomputer 62 from . this pressure
Ps has a correlation with the heat load acting on the evaporator 7, that is, the heat load (cycle load) of the cooling cycle, and the cycle load can be determined from this.

Next, in step 85, it is determined whether this compressor suction pressure Ps is greater than a predetermined target suction pressure Pe. This determination is made by cycle load comparison means 71 shown in FIG. 1 built into the microcomputer 62.

When the compressor suction pressure Ps is larger than the target suction pressure Pe, it indicates that the cycle load is high. Therefore, in such a case, proceed to steps 86 and 87. In the opposite case, it is determined that the cycle load is low, and in this case, the process goes to steps 89 and 90.

In steps 86 and 87, the crank chamber pressure control means 72 shown in FIG. 1 opens the first solenoid valve 57 and closes the second solenoid valve 58, as shown in FIG. 4A. By opening the first solenoid valve 57 in this manner, the compressor suction pressure Ps, which is lower than the compressor discharge pressure Pd, is applied to the crank chamber 12 through the suction side communication passage 5.
4 and the supply path 53,
The differential pressure between the pressure acting on the rear surface of the piston and the pressure acting on the front surface during the suction stroke as shown in FIG. 4B becomes small, and as shown in FIGS. The angle of inclination of the rotating wobble plate 16 with respect to the drive shaft 11 increases. As a result, the stroke of the reciprocating piston 23 becomes longer, the compressor discharge capacity for the same number of revolutions increases, and an appropriate flow rate of refrigerant corresponding to the high load flows into the cycle. Note that FIG. 4A shows a state in which the illustrated piston 23 has advanced to the top dead center, and FIG. 4B shows a state in which the illustrated piston 23 has retreated to the bottom dead center.

Next, in step 88, it is determined whether or not to end the control. If it is to be continued, the process returns to step 82; otherwise, the control is ended (step 100). The decision whether to continue with this control is
For example, this is done based on whether the air conditioner switch is on.

In step 85, the compressor suction pressure Ps reaches the predetermined pressure Po.
If it is determined that the cycle load is low, please proceed to step 89.
Go to 90. There, by the action of the crank chamber pressure control means 72 shown in FIG. 1, as shown in FIG. 4C,
The first solenoid valve 57 is closed and the second solenoid valve 58 is opened.
When the second electromagnetic valve 58 opens in this manner, the compressor discharge pressure Pd of the discharge port 33, which is a relatively high pressure, is supplied into the crank chamber 12 via the supply path 53. Then, the piston 23 in the suction process
(The state shown in Fig. 4B) The pressure difference between the front and rear of the piston becomes large, and the non-rotating wobble plate 1
A moment acts in the direction that makes 6 stand up. As a result, the inclination angle of the non-rotating wobble plate 16 becomes almost perpendicular to the drive shaft 11. Therefore, the reciprocating stroke of the piston becomes shorter,
The discharge capacity of the compressor for the same rotational speed is reduced, allowing an appropriate flow rate of refrigerant to flow into the cycle in accordance with the low load.

Next, when steps 89 and 90 are completed, step
Go to 88, and if the control is not finished, repeat the steps described above.

According to such control, in step 83, it is determined whether the internal pressure of the crank chamber is approaching the compressor discharge pressure, and if the internal pressure of the crank chamber is approaching a predetermined pressure or higher, the pressure of the crank chamber is forcibly lowered. become. Therefore, the pressure within the crank chamber 12 is always lower than the compressor discharge pressure. Therefore, as shown in FIG. 5A, when the piston 23 is in the suction stroke, the pressure in the crank chamber 12 is
pressure (compressor suction pressure), the difference in pressure before and after the pressure causes the pressure to flow from the crank chamber 12 side to the compression chamber 2.
A flow of refrigerant as shown by arrow A occurs toward the 6 side through the gap between the piston 23 and the cylinder 25,
At the same time, the lubricating oil contained in the refrigerant lubricates the sliding parts. In addition, as shown in FIG. 5B, in the piston 23 in the discharge process, the pressure in the crank chamber 12 is lower than the pressure in the compression chamber 26 (compressor discharge pressure), so from the pressure difference before and after that, Piston 23 and cylinder 2 toward the crank chamber 12 side
5, a flow of refrigerant occurs as shown by arrow B, and at the same time, the lubricating oil in the refrigerant lubricates the sliding parts.

Therefore, even if the internal pressure of the crank chamber 12 is brought close to the compressor discharge pressure in order to control the discharge capacity of the compressor, lubricating oil will enter and exit the crank chamber 12 through the gap between the piston 23 and the cylinder 25. , the lubrication inside the crank chamber 12 is maintained well.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways.

For example, the cycle load detection means 70 is not limited to the pressure sensor 63, but may be a temperature sensor that detects the temperature of the refrigerant on the discharge side of the evaporator 7, or a combination of the pressure sensor and the temperature sensor. The subcooling amount detection means for the refrigerant may be made of: Furthermore, the crank chamber 12
Since the cycle load can be estimated by detecting the internal pressure, the cycle load detection means 70 may be a pressure sensor 64 provided inside the crank chamber. Further, since the cycle load can be estimated by detecting the compression ratio of the compressor, the cycle load detection means 70 may be a compression ratio detection means of the compressor.

[Effects of the invention] As explained above, according to the invention, in a variable capacity swash plate type compressor, even if the internal pressure of the crank chamber is brought close to the compressor discharge pressure in order to change the capacity, the Since the internal pressure of the piston is always set to be lower than the compressor discharge pressure by a predetermined pressure, it contributes to energy saving and has the excellent effect of improving lubrication of the sliding parts of the piston.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the present invention;
The figure is a schematic configuration diagram of a variable capacity swash plate compressor and its control device according to an embodiment of the present invention, and FIG. 3 is a flowchart showing the operation of the embodiment.
4A to 4C are schematic sectional views of a variable capacity swash plate type compressor according to the same embodiment, FIGS. 5A and B are sectional views of essential parts of the piston in the compressor according to the same embodiment, and FIG. 6 is a cooling system for automobiles. FIG. 2 is a schematic diagram showing a cycle. 11... Drive shaft, 12... Crank chamber, 13...
... Drive swash plate, 16 ... Wobble plate, 23 ... Piston, 26 ... Compression chamber, 28a ... Suction port,
28b...Discharge port, 54...Suction side communication path,
55...Discharge side communication path, 57...First solenoid valve, 5
8...Second solenoid valve, 62...Microcomputer, 63...
Pressure sensor, 64, 65...Pressure sensor, 70...
... Cycle load detection means, 71 ... Cycle load comparison means, 72 ... Crank chamber pressure control means, 73
... Crank chamber pressure detection means, 74 ... Compressor discharge pressure detection means, 75 ... Crank chamber pressure comparison means.

Claims (1)

[Claims for Utility Model Registration] A plurality of pistons 23 mounted in a cylinder block 24 so as to be able to reciprocate in the axial direction are connected to the drive shaft 11.
The pressure in the compression chamber 26 formed in front of the piston 23 and the pressure in the compression chamber 26 formed in the rear of the piston 23 are controlled so that the pressure in the compression chamber 26 formed in the front of the piston 23 and the pressure in the compression chamber 26 formed in the rear of the piston 23 are In the variable capacity swash plate type compressor, the stroke of the piston 23 is changed by changing the inclination angle of the drive swash plate 13 according to a change in the differential pressure between the drive swash plate 13 and the pressure in the crank chamber 12. cycle load detection means 63, 70 for detecting the heat load of the cooling cycle in which the cycle load detection means is installed; cycle load comparison means 71 for comparing whether the cycle load detected by the cycle load detection means is greater than or equal to a predetermined value; and the crank chamber. 12; a compressor discharge pressure detector 74 that detects the pressure of the refrigerant discharged from the compressor; a pressure detected by the compressor discharge pressure detector 74 and the crank chamber; a crank chamber pressure comparison means 75 for comparing whether the pressure difference between the pressure detected by the pressure detection means 73 and the pressure detected by the pressure detection means 73 is below a predetermined pressure; and a crank chamber pressure control means 72 for changing the pressure within the crank chamber 12, and when the differential pressure compared by the crank chamber pressure comparison means 75 is below a predetermined pressure, A control device for a variable capacity swash plate type compressor, characterized in that the crank chamber pressure control means 72 controls the pressure in the crank chamber 12 preferentially based on an output signal.